International Workshop on Tethyan Orogenesis and Metallogeny in Asia and Cooperation Among

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International Workshop on Tethyan Orogenesis and Metallogeny in Asia and Cooperation among

Institutions of Higher Education

Extended Abstract Volume

Edited by Changqian Ma, Paul T. Robinson and Yunlong He

Mafic dykes in Paleo-Tethyan granitoid pluton (East Kunlun, Northern Qinghai-Tibet Plateau)

China University of Geosciences 11th - 16th October, 2014 Wuhan, China

Organization Structure of Workshop

Scientific Committee Chair: Jingsui Yang (China)

Co-Chairs: Erdin Bozkurt (Turkey) Jianwei Li (China) Paul T. Robinson (China) Qinglai Feng (China) Hassan Mirnejad (Iran) Olga Sayfulloeva (Tajikistan)

Members: Sajjad Ahmed (Pakistan) Roger Mason (China) Jonathan Aitchison (Australia) Lianfu Mei (China) Honghan Chen (China) U.ur Ka.an Tekin (Turkey) Chongpan Chonglakmani (Thailand) Nguyen Van Vuong (Vietnam) Farahnaz Daliran (Germany) Guocan Wang (China) Mohammad Naim Eqrar (Afghanistan) Guoqing Wang (China) Mohammad Hassan Karimpour (Iran) Jiasheng Wang (China) Xinbiao Lv (China)

Organizing Committee Chair: Changqian Ma (China)

Co-chairs: Qinglai Feng (China) Lailin Sun (China) Hongtao Su (China) Lijun Zhang (China)

Members: Myo Min (Myanmar) Mongkol Udchachon (Thailand) Zhenbing She (China) Yunlong He (China) Sihai Wang (China) Hui Wang (China) Dan Wu (China) Sponsors

China University of Geosciences (CUG), Wuhan

National Natural Science Foundation of China, Beijing

State Key Laboratory of Geologcial Processes and Mineral

Resources, CUG, Wuhan State Key Laboratory of Continental Tectonics and

Dynamics, CAGS, Beijing

Contents

Basaltic flows in the Laki Range of the Lower Indus Basin, Sindh, Pakistan: evidence for northwestern extension of the Deccan traps ...... 1 Muhammad Hassan Agheem, Qasim Jan, Sarfraz Hussain Solangi, Amanullah Laghari, Humaira Dars Petrogenesis of Late Carboniferous gabbro east of Misho, Northwest Iran, based on geochemical and Sr–Nd isotopic data ...... 2 Maryam Ahankoub Hydrology of the Himalaya Mountains under a changing climate from historical stream gauge data for selected watersheds in Pakistan ...... 6 Zulfiqar Ahmad Review of the geology of gold-bearing quartz veins in the Tethyan orogenic belt- A case study of the Mayum gold deposit, Tibet, SW China ...... 7 Hafizullah Abba Ahmed, Ismaila V. Haruna, Mukhtar Habib, Jakada Hamza, Mohammed Ishag Mohammed Abdallsamed The importance of field observations in geological investigations: Some stratigraphic constraints on the timing of India-Asia collision ...... 8 Jonathan Aitchison Palaeoproductivity and palaeoredox conditions of the HuaiHinLat Formation in Northeastern Thailand ...... 10 Boonnarong Arsairai,Akkhapun Wannakomol,QinglaiFeng, Chongpan Chonglakmani Ophiolites: their magmatic evolution and emplacement mechanisms ...... 12 Yildirim Dilek Water resources of Afghanistan and their trans-boundary context ...... 14 M.Naim Eqrar Temporal and spatial distribution of major metal deposits in the Eastern Tethyan metallogenic domain: a review ...... 16 Yuheng Guo, Changqian Ma Assessing the viability of research cooperation for petroleum exploration and production: A case study of the Federal University of Technology (FUT), Minna, Nigeria and CUG, Wuhan, China ...... 17 Mukhtar Habib, Yao GuangQing, Congjiao Xie, Hamza Jakada Volcanogenic massive sulfide mineralization in the Kashan-Delijan region, Iran ...... 21 Fayeq Hashemi, Fardin Mousivand, Mehdi Rezaei-Kahkhaei Stratigraphy and paleontology of marine Permian and Triassic sequences in the Nong Prue district, Kanchanaburi Province, Thailand ...... 25 Krongkaew Jenjitpaiboon, Chongpan Chonglakmani Paleozoic-Mesozoic magmatism and metallogeny in the Laojunshan district, Yunnan Province, South China ...... 27 Shaoyong Jiang, Bin Xu, Rong Wang Time constraints on partial melting and deformation of the Himalayan crystalline sequence, Nyalam Tibet: implications for orogenic models ...... 29 Philippe Hervé Leloup, Gweltaz Mahéo, Alexandre Aubray, Xiaobing Liu, Xiaohan Liu, Jean-Louis Paquette, Nicolas Arnaud

Magmatism and mineralization in the Permian large igneous province in the Tarim Basin, NW China ...... 32 Zilong Li, Yinqi Li, Shufeng Yang, Hanlin Chen, Yu Xing, Siyuan Zou Late Permian back-arc basin development in the western Jinshajiang suture zone, Central Qinghai-Tibetan Plateau: evidence from the Yushu mafic-ultramafic rocks ...... 34 Bin Liu, Changqian Ma, Xin Zhang, Pan Guo, Fuhao Xiong Analysis of the mechanism of faulting and uplift in the Huizhou depression, Pearl River Delta, South China ...... 37 Hailun Liu Different mantle evolutions between the Paleo-Asian and Paleo-Tethyan domains deduced from Pb isotopic data ...... 39 Xijun Liu, Wenjiao Xiao, Jifeng Xu, Paterno R Castillo Subduction and oceanic ridges and ophiolite obduction ...... 43 Roger Mason Crustal assembly of Myanmar: establishing a geo/thermochronological database for magmatism, metamorphism, deformation, and exhumation in central and eastern Myanmar ...... 46 Myo Min, Lothar Ratschbacher, Eva Enkelmann, Leander Franz, Raymond Jonckheere, Marion Tichomirowa Evaluating the origin of major magmatic iron deposits in Iran (Gol-Gohar, Sanagan and Bafq): constraints from geological, mineralogical and geochemical characteristics ...... 48 Hassan Mirnejad Volcanogenic massive sulfide Cu-ag mineralization in the Kharturan area, southeast of Shahrood .... 53 Fadin Mousivand Record of tectonic transformation in SW Yunnan: Geochemical and zircon U–Pb geochronological evidence from arc-derived, Late Devonian volcanogenic sediments in the southern Lancangjiang zone ...... 54 Xiaomei Nie, Qinglai Feng Petrography, geochemistry and U-Pb detrital zircon dating of the clastic Phu Khat Formation in the Nakhon Thai region, Thailand: implications for provenance and geotectonic setting ...... 56 Pradit Nulay, Chongpan Chonglakmani, Qinglai Feng Application of geochemical fingerprinting to mineral deposit classification and exploration ...... 58 J. A. Pearce Geochemical and geochronology constraints on the origin of the meta-mafic volcanic rocks in the Tengtiaohe Zone, SW China ...... 62 Xin Qian, Qinglai Feng, Yuejun Wang, Zhibin Zhang Porphyry Cu-Au, Mo and Cu-Mo metallogenic systems in the Qinghai-Tibetan Plateau from subduction and continental collision to transitional settings ...... 63 Kezhang Qin, Guangming Li, Junxing Zhao, Jinxiang Li, Bo Xiao, Lei Chen, Mingjian Cao New perspectives on ophiolite formation: evidence from UHP, highly reduced and crustal minerals in mantle peridotites and podiform chromitites ...... 67 Paul T. Robinson, Jingsui Yang, Fahui Xiong and Xiangzhen Xu Geodynamics of the inner and outer Zagros Ophiolite belt (Iran), inferred from the chemical composition of Cr-spinel in chromitites ...... 69 Fatemeh Sepidbar, Hassan Mirnejad Petrography and mineral chemistry of volcanic rocks south of Bardsir (Dahaj-Sarduieh, Iran): evidence for magma mixing ...... 73 Fatemeh Sepidbar, Hassan Mirnejad

Tectonic setting of plagiogranites and gabbros in the Shahre-Babak ophiolitic sequence (Nain- Baft belt), Iran ...... 77 Fatemeh Sepidbar, Hassan Mirnejad Late Cretaceous intra-plate volcanism in Ceno-Tethys: evidence from the Kazhaba Volcanics, Balochistan, Pakistan ...... 82 Rehanul Haq Siddiqui Volcanogenic massive sulfide Cu-Ag mineralization in the Kharturan area, southeast of Shahrood, Iran ...... 84 Majid Tashi, Fardin Mousivand, Habibollah Ghasemi Landslide susceptibility assessment of Yom River Basin, Phrae Province, Northern Thailand ...... 88 Suree Teerarungsigul Depositional environment of the Tertiary Krabi Basin of Southern Thailand using coal petrography ...... 89 Bantita Terakulsatit Petroleum potential assessment in northeastern Thailand using computer programs ...... 91 Kriangkrai Trisarn and Akkhapun Wannakomol Inorganic carbon isotopic anomalies across the Ordovician--Silurian boundary on the Yangtze Platform, South China: an environmental event interpretation ...... 93 Shen Tu, Zhou Wang, Jiasheng Wang Geochemical analysis of chert for interpretation of depositional environment in the Saraburi region, Thailand ...... 94 Hathaichanok Vattanasak, Chongpan Chonglakmani, Qinglai Feng Superimposed and simple pop-up structures in fold-and-thrust belts and their implications: Insights from sandbox models of thrust wedges ...... 96 Yuanbo Wan, Bin Deng, Zhiwu Li, Shugen Liu, Gaoping Zhao, Tong Lin Using apatite as a tracer for the origin of carbonatite: a case study of the Kaiserstuhl complex, south Germany ...... 99 Lianxun Wang, Michael A.W. Marks, Changqian Ma, Gregor Markl Halogen (F, Cl and Br) variations in alkaline rocks from the Upper Rhine Graben, SW Germany ... 103 Lianxun Wang, Michael A.W. Marks, Changqian Ma, Gregor Markl Comparison of coastal change in the Gulf of Thailand and the Andaman Sea: case study in Nakhon Si Thammarat and Trang Provinces, southern Thailand ...... 108 Namporn Wattanaton, Chongpan Chonglakmani Generation of appinitic magmas of the Xiadawu pluton, East Kunlun orogen, Northern Tibetan Plateau, by partial melting of a mixed mantle ...... 110 Fuhao Xiong, Changqian Ma Three dimensional exhumation process of the greater Himalayan Complex above the main Himalaya thrust ...... 112 Zhiqin Xu Alkaline basalts in the Karamay ophiolitic mélange, southern Central Asian Orogenic Belt ...... 113 Gaoxue Yang, Yongjun Li, M. Santosh, Wenjiao Xiao, Baokai Yang, Lili Tong, Shenglong Zhang Diamonds and highly reduced minerals in ophiolitic mantle rocks and chromitites ...... 117 J.S. Yang, X.X. Zhang, X.Z. Xu, Zh.M. Zhang, Zh. Huang, P. T. Robinson, Y. Dilek, W.L. Griffin Tethys: an archipelagic ocean model ...... 119 Hongfu Yin

III

Nb/Ta fractionation in the skarn system: evidence from in-situ textures and chemical analysis of magnetite of the Baishiya iron deposit, East Kunlun orogenic belt ...... 122 Shuo Yin, Changqian Ma Structural features, prototype-basin reconstruction and petroleum exploration potential of the Bay of Bengal Basin ...... 124 Peng Zhang, Lianfu Mei, Yixing Ma, Lulu Wu Correlations between deformation and various shortening velocities of a hypothetical fold-and- thrust belt: Evidence from sandbox modeling ...... 127 Gaoping Zhao, Bin Deng, Shugen Liu, Yuanbo Wan, Zhiwu Li, Jinxi Li Zircon U-Pb geochronology, whole-rock geochemical and Lu-Hf isotopic constraints on the petrogenesis of highly evolved I-type rhyolites in the Loei fold belt and their tectonic implications ...... 130 Tianyu Zhao, Qinglai Feng

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Basaltic flows in the Laki Range of the Lower Indus Basin, Sindh, Pakistan: evidence for northwestern extension of the Deccan traps

Muhammad Hassan Agheem1*, Qasim Jan2, Sarfraz Hussain Solangi1, Amanullah Laghari1, Humaira Dars1 1. Centre for Pure and Applied Geology, University of Sindh, Jamshoro, Sindh, Pakistan 2. National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan *Corresponding author’s e-mail address: [email protected]

Abstract The Deccan traps of India are one of the best examples of continental flood basalts. These basalts are abundantly exposed in the south-central part of India and have been studied in detail by many workers. Some 1300 km to the NW of Deccan, a sedimentary succession of Cretaceous-Tertiary rocks is well-exposed in the southern Lower Indus Basin of Pakistan. An unusual occurrence of volcanic rocks in the form of basalts is noted in this succession, both in the exposed and subsurface sections. These volcanic rocks are present in the form of meter-scale multiple flows within the Khadro Formation of Early Paleocene age. Some volcanoclasts are also observed within the Pab Sandstone of Late Cretaceous age. Although some work on these rocks has been carried out, no detailed studies have been performed on their petrogenesis and their possible relationship to the Deccan traps. These basaltic rocks are exposed in various sections of the Laki Range at almost the same stratigraphic position, and have also been encountered at the same stratigraphic positions during oil field drilling in the Lower Indus Basin. In the studied area, one flow is exposed in the Ranikot area, whereas two or three flows are exposed in the Bor Nala, Bara Nala and Bezan Dhoro sections farther north. The flows are mostly altered but are locally fresh, and these were selected for petrographic and geochemical studies. The weathered rocks are grey to light green, whereas fresh rocks are black to dark green. At places, the flows contained vesicles, which are commonly filled with secondary quartz and calcite. Petrographically, the rocks are mostly composed of calcic plagioclase, clinopyroxene, glass and opaque mineral(s) as primary constituents. A secondary orange-brown mineral (after olivine?) is the main altered product along with carbonate-filled amygdules. Texturally the rocks are fine-grained and porphyritic, with subophitic to ophitic clinopyroxene. Due to devitrification, the intersertal glass is charged with secondary magnetite. The whole-rock major element geochemistry indicates that the basalts are tholeiitic in character and may be of the Continental Flood Basalt type. The stratigraphic position, petrography and geochemistry of the basalts share commonalities with the Deccan Traps of India to the southeast. We propose, as also suggested by some earlier workers, that the Deccan trap volcanism extends northward to the Lower Indus Basin. Thus, models proposed for the emplacement of the Deccan Traps may equally be applied to the basalts of the Lower Indus Basin.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Petrogenesis of Late Carboniferous gabbro east of Misho, Northwest Iran, based on geochemical and Sr–Nd isotopic data

Maryam Ahankoub Department of Geology,Faculty of Science, Payame-e- Noor University , Tehran, Iran Corresponding author’s e-mail address: [email protected]

Abstract

Whole-rock chemical and Sr and Nd isotope data are presented for gabbroic rocks of the Misho Mountain terrain in Northwest Iran. Age data indicate that these rocks were emplaced in the late Carboniferous. The Misho Mountain gabbros are located in the central part of Misho Mountain 3+ 2+ where they form tholeiitic magma series with high TiO2, REE abundance and Fe / Fe ratios. These gabbroic rocks have major and trace element chemistry similar to N-MORB, with low initial 87Sr/86Sr (0.70379–0.70381) and initial Nd isotope ratios (ɛNd = 1 to 2); regional variations in Sr and Nd isotope ratios are similar to those of the mantle array. The Sr and Nd isotope ratios are attributed to a depleted mantle magma source. The gabbros are similar in composition to tholeiitic basalts, with relatively high contents of Ba, Pb and Sr and relatively low contents of Nb, Zr and Ni. The Sr-Nd isotopic characteristics of the Misho gabbro are similar to those of N-MORB, and show no evidence of contamination or AFC in the source. Keywords: Sr-Nd isotopes, Gabbro, Misho Mountain, Iran

1. Introduction

The Iranian Plateau is divided into eight major parts based on their geological structures, and the study area is located in the Soltanye-Misho Zone (Eftekharnejad, 1981). Closure of the Paleotethyan Ocean was marked by a collisional event between the Turan and Central Iran plates along an E-W suture zone (PTSZ), which is well displayed in the Misho Mountains of NW Iran (Azimzade and et al, 2010). The Misho Mountains are bounded both on the north and south by dextral, oblique-slip Cenozoic faults along which they have been uplifted to form a major positive flower structure (Moayyed and Hossainzade, 2011).

2. Geological Setting

Basement rocks in the Misho Mountains are composed mainly of the Precambrian Kahar Formation, which consists of pelitic, micaceous shale and fine-grained sandstone and tuff, locally intercalated with limestone. These rocks are locally contact-metamorphosed to hornfels along the periphery of a series of mafic to ultramafic plutons. Mafic plutonic rocks consist of gabbro, dunite, norite, pyroxenite, troctolite, anorthosite, and are locally covered by basaltic extrusive rocks. The gabbroic rocks contain mainly plagioclase, orthopyroxene, clinopyroxene and olivine, and show

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China tholeiitic compositions. Micro-sond analyses (ARL-EMX computer) show that pyroxenes in the massif are enstatite to hypersthene, plagioclases are labradorite to bytownite and olivines are hyalosiderite (Azimzade et al., 2010). The FeO content is high in the mafic plutons and their

LREE/HREE is >1. Positive correlations between CaO and Al2O3 and HREE suggest an origin by partial melting of the upper mantle. All gabbroic rocks are likely to have been derived from the same parental magmas since their spider diagrams and multi-element patterns are similar.

2.1 Analytical techniques

After observing 45 thin sections, 6 gabbro samples were selected for whole-rock chemical analyses using XRF and ICP-AES instruments of ALS CHEM, North Vancouver, Canada. Sm–Nd and Rb–Sr isotope of the rocks were analysed in Nagoya University, Japan.

2.2 Field relations and petrographic descriptions

The Misho granitoid complex is situated between 35◦03'20" and 35◦11'20"N，and 47◦11'20" and 47◦20'54" E in northwestern Iran. In the study area, there are two main granitic bodies that crop out south of Payam village (Fig. 1), both of which contain monzosyenite, syenogranite and alkali granite. This complex has an irregular morphology and is mainly composed of K-feldspars, quartz, and Na- plagioclase together with hornblende and some biotite. It is dissected by a mafic dike (Fig, 2).

3. Petrochemistry

The gabbroic rocks have granular ophitic textures and consist of clinopyroxene and plagioclase laths, brown olivine, apatite and opaques. The AFM diagram shows a tholeiitic affinity. Decreasing

Al2O3, CaO, Cr and Ni, increasing Fe2O3, TiO2, P2O5, K2O, Na2O, MnO and incompatible trace elements, with decreasing Mg# (0.61 to 0.14) and constant Sr content, indicate an evolved tholeiitic magmas derived from depleted mantle. Chondrite-normalized REE patterns and ratios are similar to those of N-MORB (Sun and McDonough, 1995), as are the La/Yb and Ce/Y ratios. Some other ratios display similar behavior (e.g. Zr/Y, Ce/Zr, Ti/Y, Ce/Y and Th/La). Sr-Nd isotopic data for 5 selected samples from the gabbroic 87 86 sample display low initial Sr/ Sr (Sri) ratios). εNd(t) values were calculated assuming ages of late Carboniferous. In an εSr(t)–εNd(t) plot the samples lie in the mantel array, showing the significant role of a DMM component in their genesis.

4. Conclusions

The gabbroic magmatic activity in the study area occurred in the Paleozoic. The chemical compositions and Sr–Nd data show that the gabbros are compositionally similar to N-MORB and that they originated from a depleted mantle source.

Figures and Tables

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 1 Location of study area and formed positive flower structure by dextral, oblique-slip fault systems (Moayyed and Hossainzade, 2011).

Fig. 2 Schematic geologic map of the Misho area is modified form (Asadiyan and et al, 1995).

Acknowledgements

This paper is part of the Misho Magmatic and Tectonic Setting Project. The authors would like to thank the University of Nagoya for supporting the analyses and measure Isotope data.

References

Asadyan, O., Rastgar Mirzaie, A.R., Mohajel, M., Hajalilo, B., 1995, 1/100000 Marand Geology Map, Geological Survey of Iran.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Azimzadeh, Z., Dilek, Y., Jahangir, A., Amery, A., 2010, Remnants of the paleotethyan suture one in NW Iran(Misho Mountains) and regional correlations, conference geology meeting.

Ftekharnejad, J., 1981.Tectonic division of Iran with respect to sedimentary basins, Journal Iran Petrol Soc, v.82, p.19–28.

Moayyed, M., Hosseinzade, G.H., 2011, Petrography and petrology of A-type granitoids of eastern Misho mountains with emphasis on their geodynamic importance”, Journal of crystallography and mineralogy. p. 529-566.

Sun, S.S., McDonough, W.F., 1989, chemical and isotopic systematics of oceanic basalts; implications for mantle composition and processes Magmatic in the ocean basins, In: Saunders AD, Norry MJ, (Eds.), Geological Society of London, v.42, p.313–345.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Hydrology of the Himalaya Mountains under a changing climate from historical stream gauge data for selected watersheds in Pakistan

Zulfiqar Ahmad Department of Earth Sciences, Quaid-i-Azam University, Islamabad, Pakistan Corresponding author’s e-mail address: [email protected]

Abstract Mountainous areas with high elevations in northern Pakistan have numerous river systems with enormous surface runoff during the rainy months and glacier melt seasons that contribute significantly to the rivers of the Indus Basin and generate recharge to the underlying aquifers. A thorough study has not been made to explore the role these rivers might in increasing the water resources of the country. The Indus River, the largest in the Asia, flows from the northern mountainous areas in the Himalayas of Baltistan, Pakistan. Others streams and four major rivers are regarded as tributaries to the Indus River. Spurred by an interest in the economic development of the country, a hydrological study of the mountainous areas has been carried out to understand the mechanism of snowmelt runoff. Eight major watersheds in Pakistan, including the Gilgit, Hunza, Shigar, Shyok, Astore, Jhelum, Swat and Chitral, have been selected for this study. Available historic data from1960-2005 have been precisely utilized to study the mountainous hydrology in terms of monitoring changes in temperature and precipitation, monthly runoff, snow melt runoff, ascertained from hydrographs (1990 to 1999), and the relationship between the water yield component and runoff. Climatological data from ten meteorological observatories located in the high uplands show an uneven rainfall distribution, however changes in the rainfall patterns in winter and summer seasons are apparent. A review of the historic temperature data from the ten stations suggests that the hydrology of the northern Himalayan can be related to three regimes. i) Higher upland watersheds including large glaciated parts; ii) lower elevation watersheds in southern Karakoram; and iii) foothill drainage basins.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Review of the geology of gold-bearing quartz veins in the Tethyan orogenic belt- A case study of the Mayum gold deposit, Tibet, SW China

Hafizullah Abba Ahmed1*, Ismaila V. Haruna2, Mukhtar Habib1, Jakada Hamza1, Mohammed Ishag Mohammed Abdallsamed1 1. Faculty of Earth Sciences, China University of Geosciences, Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, Wuhan, Hubei, 430074, China 2. Department of Geology, Modibbo Adama University of Technology, Yola Adamawa State, Nigeira *Corresponding author’s e-mail address: [email protected]

Abstract Here we review the history of the Mayum orogenic quartz vein gold deposit of Tibet. The deposit, which was discovered in 2002, is located in Western Tibet in a part of the northern Himalayan, (Tethyan) orogenic zone. The deposit has an estimated reserve of >80 tonnes gold, with grades ranging from 2.23g/t to 69.56g/t. The mineralization is hosted in Neoproterozoic-Cambrian schists and is controlled by an E-W-trending fault and nearly parallel fracture zones. Isotopic and fluid inclusion analyses suggest that the ore fluids might have been derived from deep, metamorphic sources, although extensive magmatism and subsequent intrusions of Late Mesozoic –Tertiary granite or granodiorite batholiths in the region could also be an important source of mineralizing fluids. 40Ar/39Ar age dating on sericite from altered zones associated with the auriferous quartz veins shows that the gold mineralization was related to the Indo-Asian collision and was formed during the early stage of orogenesis. A future rigorous fluid-rock interaction study of the area and oxygen and isotope data from adjoining belts in the region would give a better understanding of the genesis of the deposit and perhaps encourage exploration for additional orogenic gold deposits in the region.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

The importance of field observations in geological investigations: Some stratigraphic constraints on the timing of India-Asia collision

Jonathan Aitchison School of Geosciences, University of Sydney, Sydney, NSW 2006, Australia Corresponding author’s e-mail address: [email protected]

Abstract Much has been both said and written about the timing of collision between India and Asia and the uplift of the Himalayan mountain chain and Tibet-Qinghai Plateau. In spite of a wealth of new observations and data it is not uncommon for models and syntheses to rely on existing out-dated dogmas and take little account of important new constraints. Of particular importance in the past decades has been the realisation that the chain of ophiolite occurrences along the Indus/Yarlung suture zone represents elements of one or more intra-oceanic island arc systems that were present within the Tethyan Ocean. In spite of this knowledge, few new models take into account the fact that any such crustal elements within Tethys MUST have interacted with either the Indian or Eurasia margins as surrounding Tethyan oceanic lithosphere was consumed. If they did so then the geological record should contain some evidence of this activity. Although we still have much to learn about intra-Tethyan arc systems and associated subduction polarities any models that fail to take into account the complexity of Tethys are simply not worth the paper upon which they are written. In other cases there is a proliferation of non sequitors, where new models are built on false premises. This is clearly the case in consideration of many geochemical data, which are commonly interpreted as post-collisional simply because existing hypotheses that are clearly falsified by other data suggest a particular time for collision. Thus, rather than considering petrography and geochemistry on its merits any rocks that are younger than an time arbitrarily assigned to collision are automatically regarded as post-collisional. In other areas stratigraphic relationships, which are clearly impossible are accorded some sort of validity further compounding errors (e.g. sediments of the Xigazeforearc basin emphatically do not have a depositional relationship upon ophiolitic basement at any location along the Indus/Yarlung suture zone – yet this is ignored). In fact, it is astonishing that concluding sections of many papers where models are presented seem to be the area where the least scientific rigour is applied. This kind of simplistic approach is counter-productive as surely we should build on new data rather than ignoring it. In 2007 Aitchison and colleagues published a summary of existing data and interpreted those data on their merits in order to test the 55 Ma collision model. Their results clearly demonstrated major problems associated with the notion of early collision. Amazingly this publication generated an

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China enormous backlash of anti-scientific research where large sections of the community found any challenge to the existing dogma unacceptable and in a departure from the usual Popperian epistemology of hypothesis falsification set out to prove the early collision hypothesis rather than to test it. Such a response is perhaps not surprising as history shows that other major scientific advances (Darwin – biological evolution and Wegener – continental drift and plate tectonics) have all faced similar resistance. Perhaps this reflects some sort of DōgenZen Buddhist philosophy involving the concept of ‗non-thinking‘. The age of the youngest marine sediment is widely recognised as a key constraint in any consideration of when continent-continent collision occurred. Over the past two decades we have searched for and physically visited as many known occurrences as possible of the youngest marine strata across the Himalaya from the eastern to western syntaxes. Preconceived notions of when collision occurred clearly flavour discussions of many of these localities. In some instances the youngest marine fossils do not indicate the last marine deposition – they merely indicate the last preserved marine fossils. What is clear is that along the suture from Ladakh to eastern Tibet we see evidence of deep marine deposition (radiolarites) until at least the Paleocene-Eocene boundary. These biogenic sediments are, in turn, succeeded by clastic deep marine sediments (gravity flows) that incorporate ophiolite-derived detritus. Contrary to reports that over, or incorrectly, interpret detrital zircon data (where but a few potential source terrains have been characterised) they do not contain any material that mandates a source along the Eurasian margin. Clearly it is easier to get papers reviewed and published when they agree with the ‗consensus‘ even if said consensus is wrong. Thus, there has been a rush to publication in order to achieve career goals rather than to impose some sort of scientific rigour. Slightly south of the suture zone within the Tethyan Himalayan zone several localities at which marine sedimentation clearly continues through into the Late Eocene exist. Sections contain the youngest preserved marine sediments but as all sections are truncated by faulting or erosion and the uppermost sediments remain marine they merely place a maximum age constraint on the cessation of marine conditions. Fossils including benthic and planktonic foraminifers, marine ostracods and calcareous nannofossils all indicate similar Late Eocene depositional records (Wan et al. 2014). The occurrences of marine fossils are primary evidence of marine deposition. They do not require any special interpretation of any sort of geochemistry or paleomagnetic signature. Instead they provide unambiguous physical evidence of marine conditions immediately south of the suture zone until at least latest Eocene time.

Reference

Aitchison, J.C., Ali, J.R., Davis, A.M., 2007. When and where did India and Asia collide? Journal of Geophysical Research, Solid Earth 112, B05423, doi:05410.01029/02006JB004706.

Wan, X., Jiang, T., Zhang, Y., Xi, D., Li, G., 2014. Palaeogene marine stratigraphy in China.Lethaia 47, 297-308.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Palaeoproductivity and palaeoredox conditions of the HuaiHinLat Formation in Northeastern Thailand

Boonnarong Arsairai1, 2*,Akkhapun Wannakomol1,QinglaiFeng2, Chongpan Chonglakmani1 1. School of Geotechnology, Institute of Engineering, Suranaree University of Technology, NakhonRatchasima 30000, Thailand 2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China * Corresponding author’s e-mail address: [email protected]

Abstract The petroleum exploration has been conducted in the Khorat Plateau since 1962 and two gas fields have been discovered and commercially produced thus far. The lacustrine facies of the HuaiHinLat Formation is believed to be one of the main source rocks of the gas. Therefore, we carried out a study of the HuaiHinLat shale as a potential petroleum source rock in the region.. The HuaiHinLat Formation consists of fluvio-lacustrine sediments of Late Triassic (Norian) age. Chonglakmani and Sattayarak (1978) suggested that the HuaiHinLat Formation was deposited in half-grabens and that it consists predominantly of clastic sediments deposited in alluvial fan, restricted lacustrine and fluvial environments. The formation is exposed along the margin of the Khorat Plateau and is present in the sub-surface basins beneath the Khorat Group of Rhaetian to Late Cretaceous age. The Kuchinarai Group is the equivalent of the HuaiHinLat Formation in the subsurface (Booth, 1998). The studied section is located in the Sap Phlu Basin, which is a small basin among the Late Triassic basins of this region. The section is about 14 m thick and consists mainly of calcareous shale, calcareous mudstone, marlstone, and limestone, which can be correlated to a part of the DatFa Member of a deep lacustrine facies (Chonglakmani and Sattayarak, 1987). We undertook a petrographic and geochemical study of shale samples from the studied section in order to investigate the past redox conditions and palaeoproductivity in the basin. The biotic diversity and the concentration of palynofacies were analyzed and calculated using light microscopy. The palynofacies assemblage comprises on average AOM (51.7 %), acritarchs (26.7 %), phytoclasts (21.6 %), and very small amounts of spores and pollen. We analysed the total organic carbon (TOC) and the concentrations of major, trace, and rare earth elements. The palaeoproductivity proxies are -4 composed of palynofacies, TOC (1.9-7.1 %), excess SiO2 (1-13.43 %), Ba/Al (11.85-49.55(10 )), and P/Al (0.009-0.023(10-4)). A high palaeoproductivity, particularly in the middle part of the section, is indicated by high values of TOC, Ba/Al, P/Al, acritarchs and phytoclasts. The sediments with high palaeoproductivity accumulated adjacent to terrestrial sources as indicated by mixing of abundant phytoclasts and spores and pollen. This palynological assemblage (including AOM) is associated with organic matter predominantly of Type I and Type II kerogen.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

The palaeoredox proxies consist of U/Th, V/Cr, NiCo, (Cu+Mo)/Zn, Ni/V, and the Ce anomaly. They were used to establish the depositional environment, to characterize the organic matter content and to assess the source rock potential. The V/Cr (1.5-3.3), (Cu+Mo)/Zn (0.52-1.04), Ni/V (0.09-0.20), and Ce anomalies (0.84-1.19) are good indicators for redox conditions. U/Th and Ni/Co values also show the same trend throughout the section. The average value of V/Cr is greater than 2 indicating that it is above the oxic-dyosxic boundary (Jones and Manning, 1994) and Ce/Ce* exceeds 0.8, which is above the oxic-dysoxic and anoxic cutoff (Shen et al., 2012). The lower and the upper parts of the studied section were deposited under reduced and good preservation conditions. They can be referred to the typical black shale facies of dysoxic to anoxic environments. The middle part of the section is lighter grey in color and may represent a more oxic condition in the bottom water. The shale samples of the HuaiHinLat section of the Sap Phlu Basin are interpreted to have been deposited in a dysoxic to anoxic environment. Keywords: fluvio-lacustrine facies, primary productivity, Ban NongSai section, acritarchs, Sap Phlu Basin, trace elements, organic carbon preservation, dysoxic to anoxic environment

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Ophiolites: their magmatic evolution and emplacement mechanisms

Yildirim Dilek1, 2 1. Department of Geology & Env. Earth Science, Miami University, Oxford, USA 2 State Key Laboratory of Continental Tectonics and Dynamics of China, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Corresponding author’s e-mail address: [email protected]

Abstract Ophiolites display significant variations in their internal structure, geochemical fingerprints and emplacement mechanisms. These differences are controlled by (a) the proximity of their tectonic setting of magmatic construction to plumes or trenches; (b) rates, geometry and nature of spreading; (c) mantle compositions, temperatures and fertility; and, (d) the availability of fluids in these environments. The oceanic crust preserved in ophiolites may form in any tectonic setting during the Wilson cycle evolution of ocean basins from rift-drift and seafloor spreading stages to subduction initiation and terminal closure. Ophiolites are classified to the first order as subduction-related and subduction-unrelated types. Those ophiolites whose magmatic construction was not affected by subduction processes include continental margin (CM), mid-ocean ridge (MOR) and plume-type (P) ophiolites (Table 1). These types correspond to the ophiolites developed at ‗normal‘ mid-ocean, plume-related mid-ocean, continental margin, and subducted ridges. Subduction-influenced ophiolites include suprasubduction zone (SSZ) and volcanic arc (VA) ophiolites (Table 1). The SSZ types encompass the ophiolites formed in subduction-initiation and backarc basin ridges. The occurrence of ophiolites in orogenic belts is a product of two important factors: (1) tectonic, magmatic and geochemical processes of ophiolite formation, and (2) preservation of ophiolites as a result of different emplacement mechanisms and post-emplacement processes. An ophiolite is emplaced either from a down-going oceanic lithosphere via subduction-accretion or from the upper plate of a subduction zone through trench–continent collision. Subduction zone tectonics is thus the most important factor in the igneous evolution and emplacement of ophiolites into continental margins. The distribution and different types of ophiolites in China are evaluated within the framework of this classification scheme.

Figures and Tables

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

From: Dilek & Furnes, 2014, Elements, v. 10, No. 2, p. 93-100.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Water resources of Afghanistan and their trans-boundary context

M.Naim Eqrar Faculty of Geosciences, University of Kabul, Afghanistan Corresponding author’s e-mail address: [email protected]

Abstract Securing access for all to a critical resource such as water is one of the key human development challenges facing Afghanistan, considering the critical bearing that water has on many afghan livelihoods. Such a vital task will essentially include managing increasing scarcity (mainly fueled by a growing demand); ensuring protection against vulnerabilities associated with climate shocks and uncertainties in water flows; and safeguarding water quality. While confronting such challenge, Afghanistan cannot afford to ignore the regional dimensions of its water resources. At the national level, Afghanistan could be labeled a water-rich country. Yet, the perception at the country level can be misleading. Indeed, the very high spatial variability in river basins and sub- basin gives a different perspective and indicates that water scarcity (as defined per the Falkenmark indicator) is already serious in the Northern Basin. Other river basins, such as the Kabul-Indus, are already suffering from localized scarcity or are under pressure. Furthermore, the foreseen increasing water demand driven mainly by population growth logically puts an increasing stress on the supply-demand balance. Predictions show that some river basins, such as the Helmand and Harirod, will pass below the scarcity threshold within a few decades if not years, while the Northern Basin will face absolute scarcity in the very near future. Dealing with this issue will involve improved water productivity via better efficiency of water use for food production but also, where possible, improved supply via storages and dams. Watershed rehabilitation and protection should also be a long term but vital strategy. Such an approach would in fact also contribute to being prepared for climate change impacts, which are inevitably going to add to the existing problem of scarcity and climate shocks. Groundwater, which has traditionally been developed and utilized for irrigation purposes through the use of karezes, springs and shallow hand dug open wells should also seriously be considered as a priority for development and protection. Despite an overall positive picture in terms of availability/use balance, analysis shows that in some river basins, over-extraction is already happening. There is clearly a need to develop accurate estimates in the country to allow sustainable development of this resource. This effort should be combined with a water resource management approach in order to prevent over allocation and serious depletion of this resource on which millions of Afghans rely for domestic purposes.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Afghanistan also faces strong challenges in terms of climate shocks. If droughts occur in Afghanistan as in any arid and semi-arid countries, the country will be particularly sensitive to such shocks. A strong dependence on the agriculture sector, a low level of infrastructure development and storage limitations are some of the factors which multiply the impacts of such climate shocks. Floods are another climate shock regularly affecting Afghans‘ livelihood. Land degradation over the past decades as well as multiplication of settlements in risk areas partly fueled by population growth are certainly factors increasing risks of severe impacts. Remote sensing forecast programmes, hold great promises to decrease population vulnerability by enhancing warning systems and relief support. While Afghanistan increasingly needs to take initiatives in order to tackle its forthcoming water scarcity challenge, and to mitigate the devastating effects of droughts and floods, it cannot ignore the regional dimensions of its internal water management. As the majority of Afghan rivers are shared with several downstream riparian countries, major development projects in Afghanistan‘s river basins will have to take into considerations the potential consequences for its neighbors. Engaging dialogue through appropriate institutional platforms should be encouraged to avoid unnecessary tensions. At the same time, the international community needs to acknowledge Afghanistan‘s weak bargaining position (partly due to a lack of reliable data, expertise and relatively low diplomatic strength), and should commit to developing its capacity until it can be considered as an equally empowered stakeholder.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Temporal and spatial distribution of major metal deposits in the Eastern Tethyan metallogenic domain: a review

Yuheng Guo, Changqian Ma* Faculty of Earth Sciences, China University of Geoscoences *Corresponding author’s e-mail address: [email protected]

Abstract The metal deposits in the Tethyan metallogenic domain (TMD) are much more poorly documented as a synthesized classical metallogenic model than other such domains. Here we attempt to classify spatially the major metal deposits in the eastern TMD into seven areas on the basis of previously published data and metallogenic models. These areas are: Turkey, Iran, Five Central Asian countries, Afghanistan, Pakistan, Tebet-Sanjiang in China, and Indochina, According to published geochronological data, the major metal deposits can be placed into six main metallogenic epochs: the Late Devonian-Early Permian, Late Permian, Middle-Late Jurassic, Middle Cretaceous, Late Cretaceous-Early Paleocene and middle Eocene-Present, which were related with tectonic processes associated with opening, subduction and closure of the Paleo-Tethyan and Neo-Tethyan Oceans. All of the deposits are areally scattered rather than occurring in continuous belts. This distribution pattern of the deposits is closely related to the tectonic-metallogenic processes involved in their formation.

Keywords: east Tethyan metallogenic domain; temporal and spatial distribution; metal deposits

Acknowledgements

This study was financially supported by National Nature Science Foundation of China (Grants 41272079).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Assessing the viability of research cooperation for petroleum exploration and production: A case study of the Federal University of Technology (FUT), Minna, Nigeria and CUG, Wuhan, China

Mukhtar Habib1*, Yao GuangQing2, Congjiao Xie1, Hamza Jakada2, Musa Salihu Danlami1, Hifzullah Ahmed Abba3 1.Faculty of Earth Resources, China University of Geosciences, Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, Wuhan, Hubei, 430074, China 2. School of Environmental Studies, China University of Geosciences, Wuhan. 3. Department of Geology, China University of Geosciences, Wuhan * Corresponding author’s e-mail address: [email protected]

Abstract This paper grew out of a need to establish research as an integral and very important aspect for successful petroleum exploration campaigns. Two research institutions were identified for a proposed joint research collaboration with a view toward the effective exploration of Nigeria‘s inland basins. The findings of this collaboration will serve as a report agency that can be accessed and leveraged by any potential investor operating in the region. We developed a numerical model that can be used by the collaborating institutions to validate the viability of their relationship and enhance their research capacities. The model was built based on six different constructs and thirty measurable variables, which morphed into a set of equations that can be applied to simulate the collaboration process. The proposed co-operating partners (FUT—CUG), were identified based on a literature review to be a best fit for a mutually beneficial research collaboration that will yield a tangible result, thus opening opportunities for potential investors.

1. Introduction

Education has long been regarded as a means of social development. It is this exceptional feature of education that makes it not only important for the sustainability of the mineral industries globally and nationally, but also in ensuring that there is a consistent flow of new energy to the sector. Coupled with research and development activities, which are primarily geared toward providing the best methodologies to all levels, there is a need to ensure cost savings and overall efficiency in any collaborative energy project. The twin relationship is critical for the survival of the industry and for ensuring its advantageous linkage with associated industries and development in general. The Chinese policy on joint mineral exploration (both on a country to country basis, country to private basis, or a private company agreement) contains all elements of this sort of reciprocal educational agreement (McKenzie and Zhao, 2008). Many universities in China such as the China University of Geosciences (CUG), Wuhan in Hubei Province provides training to many international and Chinese students in various areas related directly and indirectly to the mineral and petroleum industry worldwide. Approximately 80% of the more than 620 international students in the university

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China from over eighty different countries are involved in such training (Bally 2012). Most of these countries are important trade partners for China in the mineral industry or countries where China has interest indirectly related to the mineral exploration industry. In this paper, we identify CUG to be a potential research partner in any successful mineral or petroleum exploration and development project around the world. We identified a specific exploration target that is in serious need of research and development in collaboration with a potential research partner in the resource home country. We then developed a conceptual model that will aid research partners to evaluate the viability of the research partnership and or co-operation.

2. Scope and Specific Tasks

2.1 Scope

The objective followed in this study was to develop a theoretical structural and measurement model that is capable of evaluating the effects of some key variables in respect of an FUT – CUG research co-operation to explore the hydrocarbon prospects of the inland basins of Nigeria.

2.2 Specific Tasks

Definition of FUT-CUG cooperation Defining the cooperation model Defining model constructs and path diagram Converting path diagrams to structural and measurement models Conclusion

3. Developing the conceptual model and hypotheses

3.1 Conceptual model definition

The model is a theoretical construct of structural and measurement parameters. It consists of a set of latent variables, operational measurements and hypotheses depicted in path diagrams (Fig 3). The model intends to provide some relationships in the form of mathematical equations that will serve as tools for measuring effects of defined key parameters that have great influence on the proposed FUT- CUG research cooperation.

3.2 Defining key parameters

We established the basis of this model on six structural constructs and thtrr interdependences in the form of a hypotheses as shown in Fig 4. These constructs consist of one latent exogenous variable and four latent endogenous variables. Furthermore, five independent operational variables were established with respect tp the latent exogenous variable, whereas twenty five dependent operational variables were also established with respect to the latent endogenous variables as shown in Table 1 and Fig. 3. The evidence of interdependence among the constructs and their respective operational variables can be seen on the path diagrams.

3.3 Converting path diagrams to measurement and structural models

The constructs represent latent variables that can only be measured indirectly through some observations. These observations can only be carried out by establishing the key variables controlling the effectiveness of each construct. As a result, the interaction between each construct and its variables

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China define its individual measurement model, which translates into the set of linear equations as shown in Fig. 5. Having obtained the measurement for each construct, interactions can then be applied to define the set of linear equations represented in Fig. 6. These equations represent the effectiveness of the organization for the entire process that will yield the viability of the proposed FUT-CUG cooperation.

4. Conclusions

The aim of this paper is to contribute toward cooperation among institutions in respect of petroleum and or gas exploration research. The paper provides a platform on which institutions can collaborate not only on petroleum and or gas development but also on other various areas of research with a view to testing and validating the viability of their intended cooperation The case tested in this paper is expected to yield successful economic results for a viable investment potential, which will create jobs and reduce youth restiveness and insecurity in the region. In order to support the partnership, a numerical model was developed in which key constructs for cooperation were identified together with their respective measurement variables. These constructs and variables were translated into simple mathematical equations that can be applied to capture different operating conditions, creating a means of evaluating effectiveness of the collaboration. It is evident that there is a growing awareness in the business world regarding the need for research and collaboration and proposed cooperation will be an excellent test case.

References

Closes D. 2006. Building the high performance of E&P Company. Journal of petroleum technology.58 (9), 1-4.

Earr bally, Joint exploration and development of mineral resources, Paper presented at the international conference for joint mineral resource development, Wuhan China,2012.

G.Haveluck Harrison and Fadal Safar, Modern E&P Data in Kuwait Oil Company. Journal of Petroleum Science and Engineering doi:10.1016/j.petrol.2003.12.002

Jahn,F., Cook,M., Graham,M.,2008. Hydrocarbon exploration and production, elsevier, Abardeen.

Kaplan, .Norton, D., 1992. The balanced score card measures that drive performance. Harvard Business review 71-79.

Laura Mastella, Viana Canpinho and Joao roberto alonso. PROLAB: An integrated platform for E&P data management. EAGE Conference paper, Volume 31 – issue2 – feruary 2013.

L.E.Doublet, P.K.Pande,M.B.Clark, J.W.Nevans and T.A.Blasingme. SPE29594, An Integrated Geologic and Engineering Reservoir Characterization on the north robertson (Clearfork) Unit: A case study .Paper Presented at SPE Conference,Colorado,USA, March 1995.

Mohamed AY, Pearson MJ, Ashcroft WA, Illiffe JE, Whiteman AJ, (1999). Modeling petroleum generation in the southern Muglad rift basin, Sudan: AAPG Bulletin, 83:1943–1964.

N.G. Obaje,H.Wehner,G.scheeder,M.B.Abubakar, and A.Jauro. AAPG Bulleting, V.88,No.3 (March 2004), PP. 325-353.

Nexant (2003). National oil and gas policy: A draft report prepared for the Bureau of Public Enterprises (Nigeria) by Nexant, Griffin House, First Floor South, 161 Hammersmith Road, London. Nigerias Contitution (1999). Constitution of the Federal republic of Nigeria

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Ogbonna, D. N.; Ekweozor, I. K. E.; Igwe, F. U. (2002). "Waste Management: A Tool for Environmental Protection in Nigeria". A Journal of the Human Environment 31 (1): 55–57. JSTOR 4315211.

Paul Beckett and James O’Connell, Education and Power In Nigeria, Hodder and Stoughton, 1977, pp. 26-30; and History of Ahmadu Bello University, Appendix V and VI, pp. 280-1

Paul D. McKenzie and George Zhao, New Regulations on mineral exploration in china, 2008.

Souder W.E, Buisson.D and Garret.T, 1997. Success through new costomer driven new product development.a comparisom of US and new zealand small enterpreneurial high technology firms. Journal of product innovation management. USA14(6), 459-472.

Yang, M.G., Hong., P., Modi, S., 2011. Impact of lean manufacturing and environmental management on business performance; anemphirical study of manufacturing fims.International journal of petroleum economics 129, 251-261

Zanguina M, Bruneton A, Gonnard R (1998). An introduction to the petroleum geology of Niger: J. Petrol. Geol.; 21(1):83–103.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Volcanogenic massive sulfide mineralization in the Kashan-Delijan region, Iran

Fayeq Hashemi*, Fardin Mousivand, Mehdi Rezaei-Kahkhaei School of Geosciences, Shahrood University of Technology, Iran *Corresponding author’s e-mail address: [email protected]

Abstract Volcanogenic massive sulfide (VMS) mineralization in the Kashan-Delijan region occurs in the Urumieh-Dokhtar magmatic arc as several deposits and occurrences, including the Varandan Ba-Pb- Cu, Dareh-Amrood Pb-Zn, and Tapeh-Sorkh and Dorreh Ba deposits. The host rocks comprise a Middle-Late Eocene, bimodal volcano-sedimentary sequence composed of gray and green siliceous tuff, tuff breccia, andesitic-basalt lava, rhyolite, shale, limestone, marl and pyroclastic rocks. The mineralization is concentrated in the volcaniclastic and tuffaceous rocks. The orebodies are lenticular to tabular with variable thicknesses. The ore minerals are mainly barite, galena, sphalerite, chalcopyrite, pyrite, bornite, tetrahedrite, magnetite and hematite, accompanied by secondary native copper, cuprite, covellite, chalcocite, goethite, hematite and malachite. Gangue minerals consist of chlorite, sericite, quartz and calcite. Major wall rock alterations in the deposits consist of chlorite and quartz-sericite. The VMS mineralization in the region is of the Kuroko-type, formed in an intra-arc setting due to subduction of Neo-Tethyan ocean lithosphere beneath the Iranian plate. Keywords: Massive sulfide, VMS, Khashan-Delijan, Urumieh-Dokhtar, Iran

1. Introduction

The Kashan-Delijan region, located in west-central Iran, hosts several Kuroko-type volcanogenic massive sulfide (VMS) deposits and occurrences, the largest of which are the Varandan Ba-Pb-Cu (Hashemi et al, 2014 a,b), Dareh-Amrood Pb-Zn (Hashemi et al, 2014 a), Tapeh-Sorkh (Khalajmaasomi et al., 2010) and Dorreh Ba (Nazari et al., 1992) deposits. Kuroko-type deposits and other VMS are the main sources of base (and precious) metals in the world. Therefore, these deposits have already been studied extensively (e.g., Shikazono et al., 2008; Melekestseva et al., 2014; Eyuboglu et al., 2014). The aim of this paper is to review the VMS deposits in the Kashan-Delijan region and to identify the ore-bearing VMS horizons within the host volcano-sedimentary sequence.

2. Geologic Setting

The Kashan-Delijan region is part of the Urumieh-Dokhtar magmatic arc (Figure. 1) formed in an intra-arc setting due to subduction of Neo-Tethyan ocean lithosphere beneath the Iranian plate. The Middle-Late Eocene volcano-sedimentary sequence in the region is divided into four stratigraphic units (Figure. 2), from bottom to top:

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Unit 1: Grey, green siliceous tuff, tuff breccia and crystal tuff Unit 2: White to grey nummulitic limestone locally transformed to marble and skarn, limy tuff, shale and marl Unit 3: Tuff breccia and crystal-lithic tuff Unit 4: Pyroclastic rocks and lavas (andesite, basalt and rhyolite) with varying compositions and textures, interbedded with some nummulitic-bearing volcano-sedimentary rocks and limestone Lithologically, units 1, 2 and 3 are comprised of mainly tuffaceous sediments and volcaniclastics rocks (i.e., ), whereas unit 4 is dominated by lavas (i.e., ) (Figure. 2).

3. Mineralization

The VMS mineralization southwest of Kashan and northeast of Delijan occurs in four stratigraphic ore horizons (OH) within units 1, 3 and 4 of the host sequence (Figure. 2). The first ore horizon (OH-1) involves the Varandan (Ba-Pb-Cu) deposit hosted in unit 1 (grey and green siliceous tuff, tuff breccia and crystal tuff) (Figure. 2). This ore horizon in the Varandan deposit is comprised of four sub horizons (SH-1, 2, 3, 4) (Figure. 2). The second ore horizon (OH-2) contains the Dareh- Amrood (Pb-Zn) deposit hosted by tuff breccia and crystal-lithic tuff, within the lower part of unit 3 (Figure. 2). The third ore horizon (OH-3) involves the Tapeh-Sorkh (Ba) deposit hosted by tuff in the upper parts of unit 3 (Figure. 2). The fourth ore horizon (OH-4) contains the Dorreh (Ba) deposit within unit 4 of the host sequence (Figure. 2). The footwall and hanging walls are felsic lavas and limestone, respectively. The VMS mineralization in the region shows many similarities to Kuroko- type deposits.

4. Mineralogy, ore textures and wallrock alteration

Ore textures and structures in the VMS deposits of the Kashan-Delijan region dominantly are massive, semi-massive, banded, laminated, disseminated and veins-veinlets. Ore minerals are dominated by barite, galena, sphalerite, chalcopyrite, pyrite, bornite, tetrahedrite, magnetite and hematite, which are accompanied by some secondary minerals such as native copper, cuprite, covellite, chalcocite, goethite, hematite and malachite. Major gangue minerals are chlorite, sericite, quartz and calcite. The main wallrock alteration is to chlorite and quartz-sericite.

5. Conclusions

The VMS mineralization southwest of Kashan and northeast of Delijan occurs in four stratigraphic ore horizons within units 1, 3 and 4 of the Eocene volcano-sedimentary host sequence. The Varandan deposit occurs in the first ore horizon within unit 1, whereas the Dareh-Amrood and Tapeh-Sorkh deposits occur within unit 3, in the second and third ore horizons, respectively. The fourth ore horizon involves the Dorreh deposit within unit 4. Ore textures and structures are dominated by massive, semi-massive, banded, laminated, disseminated and veins-veinlets. Primary ore minerals are chiefly barite, galena, sphalerite, chalcopyrite, pyrite, bornite, tetrahedrite, magnetite and hematite, accompanied by some secondary minerals, such as native copper, cuprite, covellite, chalcocite, goethite, hematite and malachite. Gangue minerals mainly consist of chlorite, sericite, quartz and

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China calcite. Major wall rock alterations in the deposits are to chlorite and quartz-sericite. The VMS mineralization in the region shows many similarities to Kuroko-type deposits, and were formed in an intra-arc setting due to subduction of Neo-Tethyan oceanic lithosphere beneath the Iranian continental block during the Middle-Late Eocene.

Figures and Tables

Fig. 1 Geological and structural map of Iran (Aghanabati, 2004) and locations of the Kashan-Deligan region and the VMS deposits

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 2. General stratigraphic sequences of the studied area (A) and host sequences of the Dorreh (B), Tapeh-Sorkh (C), Dareh-Amrood (D) and Varandan (E) deposits

Reference

Aghanabati, S., A., 2004, geology of Iran, Geological exploration of mining, 400 p.

Eyuboglu, Y., Santosh. M., Yi. K., 2014, The Eastern Black Sea-type volcanogenic massive sulfide deposits: Geochemistry, zircon U–Pb geochronology and an overview of the geodynamics of ore genesis, Ore Geology Reviews, v.59, p.29–54.

Hashemi, F., Mousivand, F., Rezaei-kahkhaei, M., 2014, Varandan Deposit: Kuroko-type Ba-Pb-Cu volcanogenic massive sulfide mineralization in the Urumieh-Dokhtar magmatic arc, 32nd meeting of the first Congress of the International Earth Science, Geological Survey of Iran, Tehran, Iran.

Hashemi, F., Mousivand, F., Rezaei-kahkhaei, M., 2014, Geology and geochemistry of the ore-bearing horizons of the Varandan volconogenic Ba-Pb-Cu massive sulfide deposit, southwest of Qamsar, Sixth Conference of Iranian Society of Economic Geology, Sistan and Baluchestan University, Zahedan, Iran.

Melekestseva. I., Y., Tret'yakov a, G., A., Nimis, P., 2014, Barite-rich massive sulfides from the Semenov-1 hydrothermal field (Mid-Atlantic Ridge, 13°30.87′ N): Evidence for phase separation and magmatic input Marine Geology, v.349, p.37–54.

Nazari, M., Yaaghobpor, A., Madani, H., 1991, Doreen Kashan barite deposit" of Tarbiat Moallem University, Iran mining the fourth symposium, P.106-125.

Khalajmaasomi, M., Lotfi, M., Nazari, M., 2010, Tapeh-Sorkh Mine mineralization model designation Byjgan Stagecoach-Central Province, Journal of Land and Resources, the first year, the second number.

Shikazono. N., Ogawa. Y,. Utada. M., 2008, Geochemical behavior of rare earth elements in hydrothermally altered rocks of the Kuroko mining area, Japan, Journal of Geochemical Exploration, v.98, p.65–79.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Stratigraphy and paleontology of marine Permian and Triassic sequences in the Nong Prue district, Kanchanaburi Province, Thailand

Krongkaew Jenjitpaiboon1,2*, Chongpan Chonglakmani1 1. School of Geotechnology, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand. 2. Northeastern Research Institute of Petrified Wood and Mineral Resources, Nakhon Ratchasima Rajabhat University, Nakhon Ratchasima, 30000, Thailand. *Corresponding author’s e-mail address: [email protected]

Abstract The aims of this study are to define the lithostratigraphy of marine Permian and Triassic sedimentary sequences, to identify the bivalve, ammonoid and fusulinid fauna in them, and to clarify the geological age and the depositional environment of these rocks. The area of study is located in the Nong Prue District, Kanchanaburi Province, western Thailand. Marine sedimentary sequences in the study area can be subdivided into four rock units, A, B, C and D, from oldest to youngest, respectively. Unit A consists of shale, calcareous shale and limestone and contains an ammonoid assemblage in the shales. Unit B unconformably overlies unit A and consists of limestone conglomerate, limestone, shale and siliceous shale. The limestone conglomerate contains fusulinid-bearing clasts. Unit C conformably overlies unit B and consists of shale and siliceous shale. Unit D conformably overlies unit C and consists of sandstone and shale. A bivalve assemblage has been discovered in the shales of units C and D. The collected fossils were systematically identified and described. They consist of two Phyla, the Mollusca and the Protozoa. The Mollusca consists of two Classes, the Bivalvia and the Cephalopoda (Ammonoidea). The Bivalvia comprises three genera: Halobia, Posidonia and Daonella. Halobia consists of three species; Halobia (Halobia) talauana Wanner, Halobia (Halobia) styriaca Mojsisovics, and Halobia (Zittelihalobia) sp. The Cephalopoda (Ammonoidea) comprises seven species, i.e., Agathiceras sp., Adrianites sp., Popanoceras sp., Cyclolobus sp., Metalegoceras sp., Parapronorites sp. and Propinacoceras sp. The Protozoa consists of one Class, the Foraminifera which comprises one species: Verbeekina sp. Unit A is assigned to the Middle Permian (Roadian-Wordian) based on the ammonoid faun; units C and D contain the Halobiid bivalve, which indicates a Late Triassic (Carnian-Norian) age; and the basal conglomerate of unit B contains fusulinid-bearing clasts suggesting that it is younger than late Middle Permian and is most likely Triassic based on stratigraphic grounds. Based on the lithological and paleontological evidence, the depositional environments of the studied rock units can be inferred. Unit A consists predominantly of laminated shales which indicate a low-energy environment. These shales contain ammonoids but without associated marine benthic fauna

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China suggesting that they were accumulated far from shore on a deep marine (abyssal plain) environment in the Middle Permian. The limestone conglomerate in unit B indicates a major tectonic event of the basin with considerable uplift and erosion which is represented by a strong unconformity after the late Middle Permian. Shales of units C and D also represent a low-energy environment. They contain only pelagic bivalves (Halobiids) suggesting that they accumulated in a deep marine (abyssal plain) environment in the Late Triassic. Keywords: Marine Triassic, Permian, Bivalve, Ammonoid, Fusulinid, Stratigraphy, Paleontology

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Paleozoic-Mesozoic magmatism and metallogeny in the Laojunshan district, Yunnan Province, South China

Shaoyong Jiang1,2*, Bin Xu2, Rong Wang3 1. State Key Laboratory of Geological Processes and Mineral Resources, Collaborative Innovation Center for Exploration of Strategic Mineral Resources, Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China 2. State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, Jiangsu, China 3. Faculty of Land Resources and Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China *Corresponding author’s e-mail address: [email protected]

Abstract The Laojunshan district is located in SE Yunnan Province (SW China) at the junction of the Yangtze Block to the north, the Cathaysia Block in the east and the Indochina Block to the south. This district is locally known as the Laojunshan Metamorphic Core Complex (LMCC), which consists mainly of the Early Paleozoic (Caledonian) and Mesozoic (Yanshania) granites, metamorphic rocks with Paleoproterozoic and Neoproterozoic ages, and sedimentary rocks of Cambrian, Devonian to Triassic age. The Caledonian granitic plutons in the LMCC were partly metamorphosed or deformed during the Indosinian, and contain three different intrusive suites: 1) Tuantian Unit granites, consisting of medium- to fine-grained, porphyritic and gneissic granites with blasto-quasiporphyritic textures and augen and gneissic structures; 2) Nanlao gneisses, consisting of biotite monzonitic gneiss with lepidoblastic and blastogranitic textures and streaky and gneissic structure; and 3) Laochengpo Unit granites, consisting of fine-grained gneissic granites with K-feldspar phenocrysts and streaky gneiss structures. LA-ICP-MS U-Pb dating of zircons yielded magmatic crystallization ages of ~436 Ma, ~430 Ma and ~427 Ma for suites 1, 2, and 3, respectively. Initial εHf values of magmatic zircons in all three suites are heterogeneous, ranging between +3 and -14. All three suites contain inherited zircon cores with Proterozoic U-Pb and Hf model ages. Bulk compositions form well-defined mixing arrays, with suites 1 and 2 being strongly peraluminous (A/CNK >1.1), whereas suite 3 is weakly peraluminous # (A/CNK = 1.0-1.1). Suites 1 and 2 have lower TFe2O3, Al2O3, MnO, MgO, CaO, TiO2, Na2O, Mg and

Nb/Ta but higher K2O, Rb/Sr, Rb/Ba and εNd(t) than those of suite 3. These results suggest that suites 1 and 2 were formed by partial melting of Proterozoic metasedimentary rocks with little or no input of mantle-derived materials, but that suite 3 was derived from a mixture of crustal and mantle derived, mafic magmas. The apparent paradox that the mantle-derived component has lower εNd(t) values than the crustal components is consistent with very low εNd(t) found in mantle-derived basalts in the South

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

China Block (SCB). The Wuyi-Yunkai orogenic collapse may have caused lower crustal melting of the Cathaysia Block. The Early Paleozoic granitoid magmatism with mafic input indicates an extensional environment in the western SCB, in response to post-collisional orogenic collapse. Asthenospheric upwelling and basaltic underplating probably contributed heat and melts, triggering felsic magmatism in the western SCB. Mesozoic granitoids and accompanying Sn-polymetallic ore deposit are widespread in the LMCC, which forms one of the most important polymetallic tin ore districts in China. Three mineralization- related granite bodies were identified in the district, including the Dulong coarse-grained granite (DCG), the Dulong fine-grained granite (DFG), and the Dulong porphyritic granite (DPG). LA-ICP-MS U-Pb dating of zircon grains from these three granite bodies yielded magmatic emplacement ages of 90.1 ± 0.7 Ma, 89.7 ± 0.8 Ma and 86.0 ± 0.5 Ma, respectively. The granites contain quartz, K-feldspar and plagioclase as the principal phases, accompanied by biotite, muscovite, and minor accessory minerals. Geochemically, the granites are strongly peraluminous, with high contents of alkalis, enrichment in LILEs (such as Rb) and depletion in HFSEs (such as Zr, Nb, Ti). Fractional crystallization of plagioclase and K-feldspar was the principal process of magmatic differentiation that controlled Rb, Sr, Ba and Eu concentrations, whereas the REE were fractionated by accessory minerals, such as apatite and monazite. The geochemical data suggest that the rocks are highly fractionated S-type granites. The granites show bulk rock εNd(t) values in the range of -12.2 to - C 10.8 and zircon εHf(t) values from -15.5 to -2.5, with Meso-Paleoproterozoic TDM ages for both Nd and Hf isotopes. Geochemical and isotopic data suggest that these highly fractionated S-type granites (DCG, DFG and DPG) originated from the same episode of partial melting of the protolith, which was probably metamorphosed pelitic rocks from the Meso-Paleoproterozoic continental crust. Extreme fractional crystallization resulted in enrichment of tin in the evolved granitic magmas, and the low oxygen fugacity (fO2 below NNO) would efficiently remove Sn into a hydrothermal fluid, leading to deposition of Sn-rich mineral phases. The association of the Dulong giant tin deposit and the Gejiu giant tin deposit both in the western Cathaysia Block likely mark the onset of back-arc extension or intra-arc rifting in the region during the Late Cretaceous. The upwelling of asthenospheric mantle may have triggered partial melting of metasedimentary rocks in the overlying crust to generate the S-type granitic magmas and related Sn-polymetallic mineralization to form the world class deposits in this district. Keywords: Magmatism, Tin mineralization, Laojunshan Metamorphic Core Complex, Yunnan Province

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Time constraints on partial melting and deformation of the Himalayan crystalline sequence, Nyalam Tibet: implications for orogenic models

Philippe Hervé Leloup1*, Gweltaz Mahéo1, Alexandre Aubray1, Xiaobing Liu2, Xiaohan Liu2, Jean-Louis Paquette3, Nicolas Arnaud4

1.Laboratoire de Géologie de Lyon, CNRS UMR 5276, Université Lyon1 – ENS Lyon, France 2.Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences,China 3.Laboratoire Magmas et Volcans, CNRS UMR 6524, Clermont-Ferrand Université, France 4.Géosciences Montpellier, UMR CNRS 5243, Université de Montpellier, France *Corresponding author’s e-mail address: [email protected]

Abstract New observations and deformation chronology constrained by U/Pb and Ar/Ar ages along the Nyalam section across the Himalaya are more compatible with a wedge model rather than a lower crustal channel flow model for the exhumation of the Himalayan crystalline series.

1. Introduction

The processes leading to the formation of the Himalayan belt are still widely debated. For some, the main process is that of a crustal wedge with Indian rocks being underthrusted in the lower plate and deeply buried, before being accreted to the upper plate and then overthrusted and exhumed (e.g., Mattauer, 1986). Following numerical experiment analysis, a second class of models considers that the main process is that of a lower crustal melted layer expelled outward from beneath Tibet (e.g., Jamieson et al, 2006). Both models intend to explain the main geological characteristic of the High Himalaya: a zone of high-grade metamorphic rocks (the Himalayan crystalline series [HCS]) overthrusting less metamorphosed rocks along the Main central thrust (MCT), and overlain by unmetamorphosed rocks above the South Tibet detachment (STD). The internal structure, the Oligo- Miocene inverse metamorphism and the high degree of melting observed in the HCS, have been interpreted as characteristic of either an accretionary prism, tectonic wedging, or lower channel flow.

1.1 Nyalam section results

We present new structural, U-Th/Pb and Ar/Ar data from the Nyalam section across the HCS. From south (bottom) to north (top), we distinguish four tectono-stratigraphic units between the main central thrust (MCT) and the south Tibet detachment system (STDS). Unit 1 corresponds to the MCT zone and contains the upper MCT, unit 2 shows migmatitic orthogneiss, unit 3 contains in situ migmatites and marbles, and unit 4 consists of paragneiss and marbles intruded by leucogranites. The top of unit 4 is the ~ 300-m-thick STD shear zone. Fifteen new U-Th/Pb ages on monazites and zircons of magmatic rocks from units 2, 3 and 4 (Fig. 1) indicate: a) Intrusion of N-S steep dykes between 15 and 17.5 Ma; b) Prograde metamorphism (M1) occurred at ~35 Ma followed by the onset of partial fusion (M2) at ~30 Ma in units 2 and 3; c) End of partial melting at ~18 Ma in unit 2 and ~20 Ma in unit 3; d) Seven new Ar/Ar ages of micas in late N-S gashes span the period between 18 and 5 Ma (Fig. 1) and suggest fast cooling right after the end of partial melting in unit 2.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

2. Regional implications

When combined with published P-T results, Ar/Ar, AFT, ZFT data from Nyalam as well as published results from the Lantang and Dudh Kosi Valleys these data imply that: a) Magmatic rocks of unit 4 were produced in units 1, 2 and 3; b) Ductile deformation was restricted to the base of unit 1 (MCT 1) and the top of unit 4 (STD shear zone) after ~17.5 Ma, more specifically motion ended at ~13 Ma on the STD and ~9 Ma on the MCT; c) Partial melting ended several million years before the end of motion on the MCT and the STD. In Nyalam, these structures never were the boundary of a partially molten channel; d) A first phase of rapid cooling occurred right after the end of partial fusion (at ~20 Ma in Dudh Kosi and ~17 Ma in Nyalam) (FC1, Fig. 1) prior to, or during, the intrusion of the last dykes that seal any ductile deformation in between the MCT and STD; e) A second phase of rapid cooling from ~16 to 13 Ma corresponds to exhumation of the STDsz footwall up to near surface (FC2, Fig. 1); f) The third, and last, rapid cooling event since ~5 Ma (FC3, Fig. 1) only affected the southern part of the section (units 1 and 2); g) The STDsz has a more complex geometry than the straight. low- angle fault often depicted. We propose that it follows flata and ramps, rooting south of the South Tibetan domes and that it initiated at ~24.5 Ma and has a total offset of ~40 km.

3. Conclusions

Several of these observations are barely compatible with the lower crustal channel flow model for exhumation of the HCS. Instead we propose a wedge model (Fig. 2) where HCS partial melting resulted from decompression above the MCT with an erosion and deformation front located at least ~100 km south of the present-day exposure of the MCT in the Langtang, Nyalam and Dudh Kosi sections. Shaping of the south slope of the high Himalaya took place since less than 5 Ma and was related to erosion triggered by uplift above a ramp of the MHT, not to focused erosion linked with the main exhumation of the HCS.

Figures and Tables

Fig. 1 Available ages plotted as a function of the distance from the MCT along the Nyalam cross-section. Symbols colour / shapes refer to the geochronological / mineral systems and the type of rock. U/Pb data from units 2, 3 and 4 are from this study. Ar/Ar data are from Maluski et al. [1988], Wang et al. [2006], and this study (N standing for

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

T11N samples). Zircon fission track data from Wang et al. [2010]. Apatite fission track (AFT) data from Wang et al. [2001] and Wang et al. [2010]. Grey area are interpretation: EPM: early prograde metamorphism, PM: partial melting, LRM: late retrograde metamorphism, LD: late undeformed dykes. The black arrows show fast cooling periods (FC), and inferred melt migration (MM).

Fig. 2 Conceptual model for the Miocene evolution of the Himalaya in between ~85°E and 87°E. Cross-section striking ~N30°. This oversimplified model does not take into account all observations that have been published on the Himalaya but focuses on the Miocene evolution of the HCS.

References

Jamieson, R. A., et al., 2006, Provenance of the Greater Himalayan Sequence and associated rocks: predictions of channel flow models, in Channel Flow, Ductile Extrusion and Exhumation in Continental Collision Zones, edited, pp. 165-182.

Maluski, H., et al., 1988, Argon-39-Argon-40 Dating of Metamorphic and Plutonic Events in the North and High Himalaya Belts (Southern Tibet - China), Tectonics, 7, 299-326.

Mattauer, M., 1986, Intracontinental subduction, crust-mantle decollement and crustal-stacking wedge in the Himalayas and other collision belts, Geological Society, London, Special Publications, 19, 37-50.

Wang, A., et al., 2010, Episodic exhumation of the Greater Himalayan Sequence since the Miocene constrained by fission track thermochronology in Nyalam, central Himalaya, Tectonophysics () 495, 315–323.

Wang, Y., et al., 2006, Ar-40/Ar-39 thermochronological constraints on the cooling and exhumation history of the South Tibetan Detachment System, Nyalam area, southern Tibet, in Channel Flow, Ductile Extrusion and Exhumation in Continental Collision Zones, edited by R. D. Law, et al., pp. 327-354, Geological Society of London Special Publication, London.

Wang, Y., et al., 2001, Thermochronological evidence of tectonic uplift in Nyalam, South Tibetan Detachment System, Bulletin of mineralogy, petrology and geochemistry, 20, 292-294 (in Chinese with english abstract).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Magmatism and mineralization in the Permian large igneous province in the Tarim Basin, NW China

Zilong Li*, Yinqi Li, Shufeng Yang, Hanlin Chen, Yu Xing, Siyuan Zou Department of Earth Sciences, Zhejiang University, Hangzhou 310027, China *Corresponding author’s e-mail address: [email protected]

Abstract The Early Permian Tarim Large Igneous Province (Tarim LIP) in northwestern China, contains extensive flood basaltic lavas, interlayered with tuff and sedimentary rocks, and layered intrusive rocks. The lavas have ages of 290-285 Ma, whereas the intrusive rocks range from 284 to 274 Ma. Using whole-rock geochemistry and Sr-Nd-Pb-Hf-PGE isotopic data of the different magmatic rock types and the associated Fe-Ti-V oxide deposit, we present a magmatic evolutionary model for the Tarim LIP genetically relating it to mantle plume activity and discuss the genesis of the Wajilitag Fe- Ti-V oxide deposit. Keywords: Spatial-temporal distribution, Sr-Nd-Pb-Hf isotopes, magma source and evolution, Fe-Ti oxides, Tarim large igneous province, Permian.

The Early Permian Tarim Large Igneous Province (Tarim LIP) occurs in the Tarim Basin, and encompasses an area of ca. 250,000 km2. It consists mainly of basalts and numerous mafic-ultramafic intrusions, and is comparable to the Siberian Traps and the Permian Emeishan LIP in South China. The flood basalts are widely distributed in the Kepin, Tazhong and Taibei areas, where they are locally associated with layered intrusive rocks, mica-olivine pyroxenite breccia pipes, and mafic dike swarms, syenitic rocks and bimodal dykes in the Xiaohaizi area of Bachu County; minor picrite has been found in the Tabei area. The major, trace element and Sr-Nd-Pb-Hf-PGE isotopic compositions, as well as the associated large-scale Fe-Ti-V mineralization in the Wajilitag area of Bachu County, all support a genetic model involving mantle plume activity. The basalts have a chemical affinity with OIB-like magmas and preceded formation of the intrusive rocks. The geochemical compositions and Hf isotopic character of the intrusive rocks suggests that they formed by low degrees of partial melting an OIB-like asthenospheric (plume) mantle and influenced by subcontinental lithospheric mantle (Yang et al., 2007; Zhang et al., 2008; Zhang et al., 2010a; Li et al., 2010, 2011, 2012). We argue that the basalts (290-285 Ma) were probably derived by mainly low degrees of partial melting from a complicated source within a lithospheric mantle that had been modified by interaction with asthenospheric (or plume) mantle. The mafic-ultramafic intrusive rocks (284-274 Ma) might have been derived from deeper sources, after which the magmas underwent extensive fractional crystallization. The Wajilitag layered mafic-ultramafic intrusion in Bachu County has a potential large-scale, Fe- Ti oxide (magnetite and ilmenite) deposit and is as an important lithological unit of the Tarim LIP. It consists mainly of layered olivine pyroxenite, pyroxenite and gabbro. The FeOT/MgO ratios of 1.09 to

1.64 and the presence of exsolution lamellae of ilmenite in clinopyroxene and high FeOT and TiO2 contents in whole-rocksamples of the pyroxenite and gabbro suggest that the magma parental to the intrusion was considerably enriched in iron and titanium. Olivine from these rocks has low and

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China variable Fo values, and clinopyroxene compositions show a continuous evolutionary trend, indicating that the magma parental to the intrusion experienced extensive fractional crystallization of mafic minerals and probably early removal of olivine with high Fo values before final emplacement. The high liquidus temperature of olivine (ca. 1253°C) supports that the Wajilitag mafic-ultramafic rocks were derived from an asthenospheric mantle source caused by the mantle plume upwelling under very high-temperature conditions. The magnetite (or ilmenite) inclusions enclosed in the olivine and presence of Fe-Ti oxide grains interstitial to the silicate minerals indicate that the majority of the Fe-Ti oxides were crystallized at a late stage. The presence of ilmenite lamellae in magnetite can be explained by exsolution of ilmenite from the magnetite during slow cooling. We suggest that the Wajilitag layered mafic-ultramafic rocks and massive Fe-Ti oxide ore hosted therein were derived from a mantle source and underwent continuous fractional crystallization in a slowly cooling magma chamber.

Acknowledgements

This study was funded by National Key Project for Basic Research of China (No. 2011CB808902, 2007CB411303) and Natural Scientific Foundation of China (No. 40930315).

References

Li, Z.L., Li, Y.Q., Chen, H.L., Santosh, M., Yang, S.F., Xu, Y.G., Langmuir, C.H., Chen, Z.X., Yu, X., Zou, S.Y., 2012, Hf isotopic characteristics of the Permian large igneous province of Tarim, NW China: Implications for magma source and evolution: Journal of Asian Earth Sciences, v.49, p.191-202.

Li, Y.Q., Li, Z.L., Sun, Y.L., Santosh, M., Langmuir, C.H., Chen, H.L., Yang, S.F., Chen, Z.X., Yu, X., 2012, Platinum-group elements and geochemical characteristics of the Permian continental flood basalts in the Tarim Basin, northwest China: Implications for the evolution of the Tarim Large Igneous Province: Chemical Geology, v.328, p.278-289.

Li, Y.Q., Li, Z.L., Chen, H.L., Yang, S.F., Yu, X., 2012, Mineral characteristics and metallogenesis of the Wajilitag layered mafic-ultramafic intrusion and associated Fe-Ti-V oxide deposit in the Tarim large igneous province, northwest China: Journal of Asian Earth Sciences, v.49, p.161-174.

Li, Z.L., Chen, H.L., Song, B., Li, Y.Q., Yang, S.F., Yu, X., 2011, Temporal evolution of the Permian large igneous province in Tarim Basin, Northwest China: Journal of Asian Earth Sciences, v.42, p.917-927.

Yang, S.F., Li, Z.L., Chen, H.L., Santosh, M., Dong, C.W., Yu, X., 2007, Permian bimodal dyke of Tarim Basin, NW China: Geochemical characteristics and tectonic implications: Gondwana Research, v.12, no.1, p.113- 120.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Late Permian back-arc basin development in the western Jinshajiang suture zone, Central Qinghai-Tibetan Plateau: evidence from the Yushu mafic-ultramafic rocks

Bin Liu1,2, Changqian Ma2*, Xin Zhang3, Pan Guo3, Fuhao Xiong3 1. School of Geosciences, Yangtze University, Wuhan430100, China 2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China 3. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China * Corresponding author’s e-mail address: [email protected]

Abstract The Central Qinghai-Tibetan Plateau (CQTP) is mainly characterized by the development of the Palaeo-Tethyan tectonic-magmatic system, which involved complex evolutionary processes of multiple terranes and suture zones, and provides an important window into understanding Palaeo-Tethyan tectonic evolution and mineralization of the Qinghai-Tibetan Plateau and elsewhere. The Jinshajiang Suture Zone (JSZ) is generally considered as an extremely important feature in the CQTP. However, the nature of the JSZ and the way it extends westward remain hotly debated (e.g. Wang et al., 2000; Reid et al., 2005; Metcalfe, 2006; Pullen et al., 2008; Fan et al., 2010; Yang et al.,2012). In this paper, we provide new geochronological, geochemical and isotopic data for the Yushu mafic-ultramafic rocks in the western JSZ that help to constrain the Palaeo-Tethyan tectonic evolution of the CQTP. The Yushu mafic-ultramafic rocks have very uniform zircon U-Pb ages, which range from 258±2 Ma to 257±1 Ma. However, they display more complex chemical compositions. The Geriliha gabbros intruded into the Yushu-Zhongdian block as dikes. Note that the Yushu-Zhongdian block block might be a part of the northern North Qiangtang block. Pyroxenes from the gabbros are augite with relatively high Ti and Fe, and they follow a rift-cumulate trend. The gabbros are also characterized by significantly high FeOt and TiO2, similar to typical Fe-Ti-rich mafic rocks from the Panzhihua, Eastern Greenland and Northern Somalia large igneous provinces (e.g. Zhou et al., 2005). The rocks plot between the sub-alkaline and alkaline basalt series in the Zr/TiO2-Nb/Y classification diagram and they have relatively high REE contents. In MORB-normalized trace element spider diagrams, they display strong enrichment of LREE and Th, depletion of P and weak depletion of Nb, Ta and Ti, similar to OIB. The rocks have relatively low εNd (t) (0 to +0.7) and high Isr (0.706-0.709). The Haxiu gabbros and olivine pyroxenites are distributed in the Duocai-Longbao ophiolitic mélange as slices. Olivines from the olivine pyroxenites have relatively high Fo values (78.3-83.8). Pyroxenes from the gabbros are diopside characterized by relatively high Mg and Cr and low Ti and that follow an arc-cumulate trend. The Haixu gabbros and olivine pyroxenites are compositionally similar to primitive alkaline basalst. The two rock types have very low REE and weak LREE

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China enrichment. In MORB-normalized trace element spider diagrams, they show enrichment of LREE and Th, obvious depletion of Nb, Ta, P and Ti, and are generally comparable to IAT from intra-oceanic arcs and primitive arc magmas derived from a subduction-modified asthenosphere mantle beneath a continental arc, such as the Antarctic Peninsula (Leat et al., 2002). The two rock types also have relatively low εNd (t) (-0.6 to 0 and +0.7 to +1.7, respectively) and high Isr (0.709-0.712 and 0.709, respectively). The Zhiduo mafic rocks are exposed in the Duocai-Longbao ophiolitic mélange as slices or massifs and they are usually regarded as components of an ophiolite. The Zhiduo layered gabbros and dolerites have the same chemical compositions as the Geriliha gabbros. They also plot in the area between sub-alkaline and alkaline basalts in the Zr/TiO2-Nb/Y classification diagram and they have significantly high FeOt and TiO2 and OIB-like compositions. The two rock types have relatively low εNd

(t) (+0.7 and +0.3 to +0.5, respectively) and high Isr (0.707 and 0.707, respectively). However, the

Zhiduo isotropic gabbros have moderate FeOt and TiO2 and belong to a sub-alkaline basalt series. In the MORB-normalized trace element spider diagrams, they are characterized by enrichment of LREE and Th and obvious depletion of Nb, Ta, P and Ti, similar to the mafic rocks derived from a subduction-modified lithospheric mantle. They also have relatively low εNd (t) (-1.2 to -1.0) and high

Isr (0.708-0.711). Based on mineralogical, geochemical and Sr-Nd isotopic compositions, we suggest that the Geriliha gabbros and the Zhiduo layered gabbros and dolerites all formed by partial melting of a spinel-garnet lherzolite mantle source metasomatized by subducted, slab-derived melts and aqueous fluids. The primary magmas then underwent high degrees of fractional crystallization dominated by removal of olivine and clinopyroxene under conditions of low fO2 that resulted in their Fe-Ti enrichment. The Haxiu gabbros could have been derived by partial melting of a spinel lherzolite asthenospheric mantle metasomatized by aqueous fluids. The Haxiu olivine pyroxenites were generated by relatively high degrees of partial melting of a spinel lherzolite mantle source. The Zhiduo isotropic gabbros might have been derived by partial melting of a spinel lherzolite lithospheric mantle metasomatized by aqueous fluids and sediments. On the basis of regional relationships, we propose that the JSZ does not extend westward into the Yushu-North Qiangtang area and that the Yushu mafic-ultramafic rocks could have formed in a back-arc extensional environment, which might have been related to Late Permian rollback of the Longmu Co-shuanghu oceanic slab.

Acknowledgment

This work was financially supported by the China Geological Survey (No. 1212011121270) and the National Nature Science Foundation of China (Grant No. 41272079).

References

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fan, W.M., Wang, Y.J., Zhang, A.M., Zhang, F.F. and Zhang, Y.Z., 2010. Permian arc-back-arc basin development along the Ailaoshan tectonic zone: Geochemical, isotopic and geochronological evidence from the Mojiang volcanic rocks, Southwest China: Lithos, v.119, p.553-568.

Leat, P.T., Riley, T.R., Wareham, C.D., Millar,I.L., Kelly, S.P. and Storey, B.C., 2002. Tectonic setting of primitive magmas in volcanic arcs: an example from the Antarctic Peninsula: Journal of the Geological Society, London, v.159, p.31-44.

Metcalfe, I., 2006. Paleozoic and Mesozoic tectonic evolution and Paleogeography of East Asian crustal fragments: the Korean Peninsula in context: Gondwana Research, v.9, no.1-2, p.24–46.

Pullen, A., Kapp, P., Gehrels, G.E., Vervoort, J.D., and Ding, L., 2008. Triassic continental subduction in central Tibet and Mediterranean-style closure of the Paleo-Tethys Ocean: Geology, v.36, p.351–354.

Reid, A.J., Wilson, C.J.L., and Liu, S., 2005. Structural evidence for the Permo-Triassic tectonic evolution of the Yidun Arc, eastern Tibetan Plateau: Journal of Structural Geology, v.27, no.1, p.119-137.

Wang, X.F., Metcalfe, I., Jian, P., He, L., and Wang, C., 2000. The Jinshajiang-Ailaoshan Suture Zone, China: tectonostratigraphy, age and evolution: Journal of Asian Earth Sciences, v.18, no.6, p. 675-690.

Yang, T.N., Hou, Z.Q., Wang, Y., Zhang, H.R., and Wang, Z.L., 2012. Late Paleozoic to Early Mesozoic tectonic evolution of northeast Tibet: Evidence from the Triassic composite western Jinsha-Garzê-Litang suture: Tectonics, v.31, no.4, p.1-20.

Zhou, M.F., Robinson, P.T., Lesher, C.M., Keays, R.R., Zhang, C.J. and Malpas,J., 2005. Geochemistry, petrogenesis and metallogenesis of the Panzhihua gabbroic layered intrusion and associated Fe-Ti-V oxide deposits, Sichuan province, SW China: Journal of petrology, v.46, no.11, p.2253-2280.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Analysis of the mechanism of faulting and uplift in the Huizhou depression, Pearl River Delta, South China

Hailun Liu Faculty of Earth Resources, China University of Geosciences, Wuhan, Hubei, 430074, China Corresponding author’s e-mail address: [email protected]

Abstract The Huizhou depression of the Pearl River Delta is located at the junction of the Pacific, Eurasian and Indian plates. It was formed originally in the Paleogene as a continental rift basin superimposed on a setting characterized by shear stress. The formation and evolution of the basin were complex, making this feature different from a typical rift basin. A structural pattern of uplifts and depressions is the common rule in the development of rift basins. For a long time, the boundary fault, as the main controlling factor in the development and structure of a rift basin has been thought to influence the sedimentary system and sequence configuration, and hence to determine which zones were favorable for hydrocarbon migration and accumulation. Very few studies have discussed the role that uplift plays on the evolution of a rift basin and how it may have controlled the basin‘s structural characteristics. We found that the Huizhou depression is a unique feature with frequent changes of strike and trend, an unusual pattern of ―uplifts and depressions― and multiple structural styles. Uplifts at different locations and depths, as well as faulting, have played an important roles in the formation and development of the Huizhou depression. Thus, both faulting and uplift should be investigated together in order to understand basin formation and evolution. We propose a model of combined ―faulting and uplift‖ that can be used to investigate the characteristics of any basin. Our model can be used to investigate the structures and development of hydrocarbon-bearing basins and provides a solid foundation for resource evaluation and exploration. The boundary fault as a major factor in basin development controls the basic form of the depression and generally controls both the location and depth of subsidence. The more intense the faulting, the deeper the half graben and the wider the basin. The fundamental boundary fault is generally a listric normal or ramp-flat feature that controls the basin development. This, in turn, controls the location of the depocenter(s), and the holding capacity of the basin. The boundary fault in the Huizhou depression is segmented so that its strike and trend change several times, probably as a result of ―contortion‖ in the prevailing stress field. Uplift on the opposite side of the Huizhou depression limited its further development in that direction. The depression has also been affected by Pre-Cenozoic fold uplift, pre-existing faults cutting basement and differential settlement and uplift, tilted fault block uplift and vertical stacking.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

These various uplifts have played a large role in determining the development and structure of the depression and in the sediment distribution. Faulting and uplift combined will define the sequence architecture of a depression, the style, sedimentary-filling and the distribution of sand bodies that comprise the main hydrocarbon reservoirs. Sediment sources are controlled by the basin shape, the steepness of the surrounding slopes. Important sand bodies may include subaqueous fans, transfer zone deltas, gently sloping deltas, low- uplift beach bars and channels. Keywords: Huizhou depression，Paleogene，faulting and uplift

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Different mantle evolutions between the Paleo-Asian and Paleo-Tethyan domains deduced from Pb isotopic data

Xijun Liu1*, Wenjiao Xiao2, Jifeng Xu3, Paterno R Castillo4 1. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, University of Technology, Guilin, 541004, China 2. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China 3. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, CAS, Guangzhou 510640, China 4. Scripps Institution of Oceanography, UCSD, La Jolla, CA, 92093, USA *Corresponding author’s e-mail address: [email protected]

Abstract Paleo-Tethyan and Paleo-Asian mantle domains have existed on Earth throughout the Phanerozoic. We analyzed the geochemical and Pb, Nd and Sr isotopic compositions of representative mafic rocks from five Paleo-Asian Ocean (PAO) ophiolites ranging in age from 354 to 624d Ma to constrain the isotopic evolution of its mantle domain that, in turn, will help us better understand mantle geodynamics during Earth‘s history. Data suggest that the Sr isotopic composition of PAO ophiolites do not represent primary magmatic composition due to alteration. Combined with similar data for mafic rocks from Paleo-Tethyan Ocean (PTO) ophiolites, the Nd and Pb isotopic composition indicates the sub-PAO and -PTO mantles have had similar long time-integrated history of Sm/Nd enrichment but marked differences in their Th/Pb and U/Pb fractionation. The former produced a 207 204 208 204 206 204 Pacific MORB-type mantle with lower Pb/ Pb(t) and Pb/ Pb(t) for given Pb/ Pb ratios than the latter. The PAO and PTO evolutionary histories and associated tectonic characteristics suggest the Pb isotopic differences between the two mantles may be due to the presence of two long-lived independent global-scale mantle convention cells, Pacific and Africa, which kept the sub-PAO and - PTO mantles isolated from each other. The Africa cell was overlain and, perhaps, at the same time controlled continental dispersals and collisions within the PTO realm whereas the Pacific cell was underlain and controlled the accretionary margins in the PAO realm. Consequently, the long time- integrated Pb isotopic evolution of the sub-PTO mantle most probably had been affected by continental materials more so than the sub-PAO mantle. Keywords: Paleo-Asian ocean; Paleo-Tethyan ocean; ophiolite; mantle domain; mantle convection cell

1. Introduction

Global-scale mantle heterogeneities have been recognized through geochemical studies of oceanic basalts (Hart, 1984; Hofmann, 1997). The origins, properties and histories of such chemical

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China heterogeneities provide keys to a better understanding of global mantle evolution during Earth history. One way to decipher the geology of the mantle is through long-lived radiogenic isotopes (Castillo, 1988; Dupre and Allegre, 1983; Hart, 1984; Hofmann, 1997). In this respect, Pb isotopes are a very powerful tool because Pb has four naturally occurring isotopes - the ~non-radiogenic 204Pb and radiogenic 206Pb, 207Pb and 208Pb isotopes, the half-lives of the radioactive parent elements U and Th are relatively short, and these radioactive parents are geochemically different from each other. These make 206Pb /204Pb, 207Pb /204Pb and 208Pb /204Pb isotope ratios sensitive tracers of different mantle reservoirs. Ophiolites, pieces of ocean floor that are occasionally preserved on land (e.g., Dilek, 2003), are interesting to study in this context since their trace element and isotopic characteristics generally reflect those of the composition and evolution of their underlying mantle (e.g., Mahoney, 1998; Xu and Castillo, 2004; Xu et al., 2002; Zhang et al., 2005). They are an important source of direct information on the nature of their sources and can also provide opportunities to extrapolate mantle evolution through time (Mahoney, 1998; Xu and Castillo, 2004; Xu et al., 2002; Zhang et al., 2005). The Paleo-Asian and Tethys are two extinct ancient oceans. The Paleo-Asian Ocean (PAO) was formed during the break up of the Rodinia Supercontinent between 900 to 700 Ma (Coney, 1992; Dobretsov et al., 1995). The Tethys can be further subdivided into Paleo-Tethys Ocean (PTO) and Neo-Tethys Ocean; the PTO most probably was formed during Cambrian to Silurian times, between ~550 to ~420 Ma, corresponding to the detachment of the Hun Superterrane along the Gondwanan margin (Stampfli,̧ 2000) and existed throughout the Paleozoic (550 to 270 Ma). Thus, the PAO is older than the PTO (Xu and Castillo, 2004; Xu et al., 2002; Zhang et al., 2005), but they co-existed during the Paleozoic. The Central Asian Orogenic Belt (CAOB; Jahn, 2004; Xiao et al., 2009) and Tethyan Tectonic Zone (TTZ) are two large complex tectonic domains associated with the evolution and closure of the PAO and PTO, respectively. Ophiolites representing relict fragments of the PAO and PTO crusts are preserved along the CAOB and TTZ, respectively. Thus, the geochemistry of these ophiolites can provide constraints on the mantle properties of the sub-PAO and -PTO mantles and, together with Mesozoic and Phanerozoic data, offer a natural window to constrain the Earth’s mantle evolution through the Phanerozoic eon. We present new chemical and Pb, Nd and Sr isotope compositions of mafic rocks (basalts and gabbros) collected from five typical PAO ophiolites: the Bindaban ophiolite from Tianshan of the North Xinjiang region and the Hegenshan, Chaokeshan and Ondor Sam ophiolites from the Inner Mongolia region, both in China. Significantly, good-quality Pb isotope analyses are now available for a wide variety of mafic rocks from PTO ophiolites. Thus, for comparison we also compiled the Pb and Nd isotope data for ophiolites from Tibet, the Sanjian area of southwest China and central China (Hou et al., 2006a; Hou et al., 2006b; Mahoney, 1998; Xu and Castillo, 2004; Xu et al., 2002; Zhang et al., 2005) representing the PTO. Based on Pb isotopic data, we found a distinct isotopic difference between the PAO and PTO sub-oceanic mantles (Figure. 1). In detail, almost all PAO ophiolites plot within the age-corrected (to 400Ma) Pacific MORB – i.e., along the NHRL (Hart, 1984). The PAO ophiolites have lower 207Pb/204Pb (t) and 208Pb/204Pb (t) for given 206Pb/204Pb ratios than PTO ophiolites (Hou et al., 2006a; Hou et al., 2006b; Mahoney, 1998; Xu and Castillo, 2004; Xu et al., 2002; Zhang et al., 2005), suggesting separate evolutions of the Pb isotopes in the sub-PAO and -PTO mantles. We suggest this Pb isotopic distinction between PAO and PTO mantles may have been due to the presence of two long-lived independent global-scale mantle convention cells - Pacific and Africa that have slightly different compositions and kept the PAO and PTO mantles isolated from each other. The Africa cell was overlain by and, perhaps, at the same time controlled continental dispersals and collisions within the PTO realm whereas the Pacific cell was underlain and controlled the accretionary margin processes in the PAO realm. Consequently, the long time-integrated Pb isotopic evolution of the sub-PTO mantle most probably had been affected by continental materials more so than the sub-PAO mantle.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Figures and Tables

Fig. 1 Age-corrected initial 207Pb/204Pb(t) and 208Pb/204Pb(t) vs 206Pb/204Pb(t) for PAO mafic rocks compared to age-corrected PTO mafic rocks (Xu and Castillo, 2004; Xu et al., 2002; Zhang et al., 2005, Hou et al., 2006a, 2006b) and age-corrected Indian and Pacific-north Atlantic MORB. Data source for MORB are the same as in Fig. 5. Age- corrected MORB field at 400Ma was calculated by assuming 238U/204Pb = 5 and 232Th/238U = 2.5 in the depleted MORB source (White, 1993). NHRL (Northern Hemisphere Reference Line) is from Hart (1984).

Acknowledgements

This study was jointly supported by NSFC funds (No. 41302041, 41463002), Guangxi Natural Science Foundation of China (No. 2014GXNSFBA118218, 2012GXNSFCA053007), China Postdoctoral Science Foundation Grant (2013M530440), 2013 Bagui Scholar Innovation Project of Guangxi Province (to Xu JF) and open research grants of Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration (No.13-A-01-01).

References

Castillo, P., 1988, The Dupal anomaly as a trace of the upwelling lower mantle: Nature, v. 336, p. 667-670.

Coney, P.J., 1992, The lachlan belt of eastern Australia and Circum-Pacific tectonic evolution: Tectonophysics, v. 214, p. 1-25.

Dilek, Y., 2003, Ophiolite concept and its evolution: Special Paper 373: Ophiolite concept and the evolution of geological thought, v. 373, p. 1-16.

Dobretsov, N., Berzin, N., and Buslov, M., 1995, Opening and Tectonic Evolution of the Paleo-Asian Ocean: International Geology Review, v. 37, p. 335 - 360.

Dupre, B., and Allegre, C.J., 1983, Pb-Sr isotope variation in Indian Ocean basalts and mixing phenomena: Nature, v. 303, p. 142-146.

Hart, S.R., 1984, A large-scale isotope anomaly in the Southern Hemisphere mantle: Nature, v. 309, p. 753-757.

Hofmann, A.W., 1997, Mantle geochemistry: the message from oceanic volcanism: Nature, v. 385, p. 219-229.

Hou, Q., Zhao, Z., Zhang, H., Zhang, B., and Chen, Y., 2006a, Indian Ocean-MORB-type isotopic signature of Yushigou ophiolite in North Qilian Mountains and its implications: Science in China Series D, v. 49, p. 561-572.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Hou, Q.Y., Zhao, Z.D., Zhang, B.R., Zhang, H.F., Zhang, L., and Chen, Y.L., 2006b, On the boundary of Tethyan tectonic domain on northeastern margin of the Tibetan Platea: Acta Petrologica Sinica, v. 22, p. 567-577.

Jahn, B.-M., 2004, The Central Asian Orogenic Belt and growth of the continental crust in the Phanerozoic: Geological Society, London, Special Publications, v. 226, p. 73-100.

Mahoney, J., 1998, Tracing the Indian Ocean Mantle Domain Through Time: Isotopic Results from Old West Indian, East Tethyan, and South Pacific Seafloor: Journal of Petrology, v. 39, p. 1285-1306.

Stampfli, G.M., 2000, Tethyan oceans: Geological Society, London, Special Publications, v. 173, p. 1-23.

White, W.M., 1993, 238U/204Pb in MORB and open system evolution of the depleted mantle: Earth and Planetary Science Letters, v. 115, p. 211-226.

Xu, J.F., and Castillo, P.R., 2004, Geochemical and Nd-Pb isotopic characteristics of the Tethyan asthenosphere: implications for the origin of the Indian Ocean mantle domain: Tectonophysics, v. 393, p. 9-27.

Xu, J.F., Castillo, P.R., Li, X.H., Yu, X.Y., Zhang, B.R., and Han, Y.W., 2002, MORB-type rocks from the Paleo-Tethyan Mian-Lueyang northern ophiolite in the Qinling Mountains, central China: implications for the source of the low 206Pb/204Pb and high 143Nd/144Nd mantle component in the Indian Ocean: Earth and Planetary Science Letters, v. 198, p. 323-337.

Xiao, W.J., Windley, B.F., Yuan, C., Sun, M., Han, C.M., Lin, S.F., Chen, H.L., Yan, Q.R., Liu, D.Y., Qin, K.Z., Li, J.L., and Sun, S., 2009, Paleozoic multiple subduction-accretion processes of the southern Altaids: Am J Sci, v. 309, p. 221-270.

Zhang, S.Q., Mahoney, J.J., Mo, X.X., Ghazi, A.M., Milani, L., Crawford, A.J., Guo, T.Y., and Zhao, Z.D., 2005, Evidence for a Widespread Tethyan Upper Mantle with Indian-Ocean-Type Isotopic Characteristics: J. Petrology, v. 46, p. 829-858.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Subduction of oceanic ridges and ophiolite obduction

Roger Mason Faculty of Earth Sciences, China University of Geosciences, Wuhan, China Corresponding author’s e-mail address: [email protected]

Abstract The case I discuss here is an example where an established subduction zone over-rides plates containing a spreading oceanic ridge. I am making a simplifying assumption that plate motions close to a ridge-trench collision take place on a plane rather than a sphere. First consider a case where a spreading ridge is parallel to a subduction zone (Fig.1). The three plates present are labelled A, B and C, with A and B separated by the subduction zone, and B and C by the ridge. The lithosphere in Plate A may be a continental or oceanic island arc but plates B and C must be oceanic lithosphere. The rate of subduction of Plate B below Plate A is shown by the vector s, and the half-rate of spreading between B and C by the vectorsr.I am only treating cases where the rate of subduction s is appreciably greater than the rate of spreading 2r,so that the ridge, Plates B and C areall subducted because s>2r. (Several other interesting cases are possible.)The ridge converges on the trench at a rate s-r andthe rate of subduction falls from s to s-2rafter it has been subducted. This simple case is quite often portrayed in vertical cross sections through plate tectonic models but it is unrealistic because spreading ridges are usually oblique to subduction zones and curved rather than straight in plan. Fig.2 illustrates a case where a ridge is oblique to a subduction zone at an angle φ between the ridge and the subduction zone. There is a triple junction T where the ridge collides with the subduction zone. The condition for ridge subduction is now s>rcosφ and Plate C converges with Plate A obliquely at s- 2rcosφ. The triple junction T migrates along the subduction zone from top to bottom of the diagram, the rate of migration of T depending on relative values of s, r and φ. I shall only discuss cases where s>>r and therefore T remains a TTR triple junction, and omittingalternatives. Movements become more complex when transform faults offset the spreading ridge (Fig.3). The faults may displace the ridge away from the subduction zone (+ case) or towards it (- case). In the + case the triple junction migrates along the subduction zone in the direction S→U until it reaches a point where a transform fault crosses the ridge. It then changes direction along U→S until the next section of ridge starts to collide, when it resumes its migration along S→U. Plate C is first subducted orthogonally at rate s, then undergoes oblique subduction after T has migrated past. The rate of subduction normal to the subduction zone become s-2rcosφ until normal subductionof Plate C resumes beyond the transform fault. If 2rcosφ>s>rcosφ subduction alternates with oblique extension as T migrates along the subduction zone. Collision between a subduction zone and a ridge offset by transform faults can give rise to several episodes of extension during a general period of plate

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China convergence.In the – case a triangular remnant of oceanic lithosphere belonging to Plate B (shaded in

Fig3.1) may be pressed against the subduction zone as the triple junction T migrates along S→U. This flake could become fixed to the over-riding continental plate and become detached along a transform fault and overthrust (Figs.3.2, 3.3) until T re-connects with the subduction zone (Fig.4). The flake would escape subduction and thrust over the ridge as an ophiolite fragment, shown in tectonic cross- section (Fig.4). Consideration of oblique plate collision in plan as well as cross-sections (profiles) provides significant insights into visible tectonics of mountain belts. We should bear in mind that oblique plate collisions occur over much more of the Earth‘s plate boundaries than orthogonal collisions.

Figures and Tables

Fig. 1 Orthogonal collision betweensubduction Fig. 2 Oblique collision between subduction zone (left) oceanic ridge (right). zone and oceanic ridge

Fig. 3 Oblique collision between subduction zone and oceanic ridge;+ case above, - case below.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 4 Oblique subduction of subduction zone(- case) causingan isolated triangular flake between Plate A and the ridge, Fig.4.1. Fig. 4.2,the flake detaches from the oceanic lithosphere and over-rides the ridge;Fig.4.3,the flake is thrust along the ridge; Fig. 4.4 the flake comes to rest and triple junction T continues along the subduction zone.

Fig. 5 Cross section through the subduction zone and oceanic ridge, showing detachment at the base of oceanic lithosphere.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Crustal assembly of Myanmar: establishing a geo/thermochronological database for magmatism, metamorphism, deformation, and exhumation in central and eastern Myanmar

Myo Min1*, Lothar Ratschbacher2, Eva Enkelmann3, Leander Franz4, Raymond Jonckheere2, Marion Tichomirowa2 1. Geology Department, Shwebo University, 02261 Shwebo, Myanmar. 2. Institut für Geologie, Technische Universität Bergakademie Freiberg, Bernhard-von-Cottastraβe 2, 09599 Freiberg, Germany. 3. Geology Department, University of Cincinnati, Cincinnati, Ohio, USA 4. Mineralogisch-Petrographisches Institut,Universität Basel, Bernoullistrasse 30, CH-4056 Basel, Switzerland *Corresponding author’s e-mail address: [email protected]

Abstract This research was undertaken to initiate the acquisition of a modern geo/thermochronological database by dating samples from central and eastern Myanmar; this area straddles the plate boundary between India and Asia and is characterized by large‐scale dextral wrench faulting. Regionally, the project addressed such questions as how the sutures of the Pamir‐Tibet plateau continue to the southeast around the East Himalayan (Namche Barwa) syntaxis and when deformation, exhumation, and uplift occurred south of this feature.. U/Pb zircon geochronology suggests that all basement units in Myanmar are part of Gondwana. The Shan Plateau—Shan‐Thai block of eastern Myanmar lacks Cenozoic and Cretaceous magmatism and its Triassic event links it to the Qiangtang block of Central Tibet; the Jinsha suture lies to the east of eastern Myanmar. Jurassic–Early Cretaceous magmatism ties the Mogok metamorphic belt to the Gangdese belt of Tibet (Lhasa block) and puts the Bangong‐Nujiang suture along the eastern margin of the Mogok belt. Late Eocene–Oligocene high‐grade metamorphism dominates the Mogok belt. Its ages overlap with Himalayan magmatism and the heat source for its arc‐type geothermal gradient may have been slab break‐off; Tertiary adakitic granitoids provide the firsts hints for this interpretation. The Mogok metamorphic belt cooled from high‐T metamorphism and associated magmatism over a time‐span of >10 m.y. to mid‐crustal temperatures and within a few million to near surface conditions; rapid cooling started at ~17 Ma and terminated before 10 Ma. Pebbles of the Irrawaddy Formation of NE‐Myanmar, likely Late Miocene‐Pliocene coarse fluvial deposits of the Paleo‐Irrawaddy, cooled to 60‐100°C 5‐10 m.y. later than the adjacent Mogok belt rocks. This suggests derivation of these conglomerates from the Eastern Himalayan syntaxis region, supporting speculations of a paleodrainage link with the Yarlung Tsangpo river of Tibet. The Mogok belt

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China metamorphism reached ≥700°C and ~6 kbar at ~35 Ma. Metamorphic conditions were drastically different in the Katha basement of N‐central Myanmar. There, pressure‐dominated upper greenschist facies developed prior to ~37 Ma. PTt data, lithology (metapelites and Cambro‐Ordovician orthogneisses), and absence of Cretaceous magmatism suggest that the Katha basement is part of the Himalayan Series (Indian plate). The Mogok metamorphic belt rocks experienced ductile deformation in the Oligocene with subhorizontal ~NW‐SE extension, accompanied by ~NE‐SW shortening resulting in folding and contractual strain geometries; overall, ductile deformation was moderately strong. Low‐T ductility and faulting accompanied rapid Miocene cooling. Late faulting, mostly along N‐trending, dextral, strike‐slip faults occurred in the Late Miocene–Pliocene and was related to the Sagaing fault zone that started to be active after 7 Ma. Our ongoing work in Yunnan shows that at least two of the large‐scale crustal shear zones that were interpreted to be responsible for large‐scale lateral extrusion of the Shan Plateau–Shan‐Thai block (the dextral Gaoligong and the sinistral Chongshan shear zone) formed sub‐horizontally and were related to decoupling between upper and middle crust, resulting in southward (present coordinates) flow of the upper crust. Our work in Myanmar allows us to suggest that flow in the middle crust was moderate. Based on this work, we speculate that large scale ―channel‐flow‖ around the East Himalayan syntaxis did not occur; the picture that emerges is that of flow of the upper crust, possibly caused by a topographic gradient. Keywords: Mogok metamorphic belt, Thermochronology, Exhumation, Myanmar

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Evaluating the origin of major magmatic iron deposits in Iran (Gol-Gohar, Sanagan and Bafq): constraints from geological, mineralogical and geochemical characteristics

Hassan Mirnejad Department of Geology, University of Tehran, Tehran, Iran Corresponding author’s e-mail address: [email protected]

Abstract Iron deposits in Iran encompass a variety of geological settings. The geology, mineralogy and geochemistry of three major Fe deposits (i.e., Gol-Gohar, Sangan and Bafq) suggest that magmatic activity and induced metasomatism, both related to the subduction of either Paleo-Tethys or Neo- Tethys oceanic lithosphere under the Iranian continental plate, played a dominant role in the formation and evolution of the Fe ore deposits. Keywords: Fe deposits, origin, magmatic, Tethys, Iran

1. Introduction

Iran has 12th largest Fe ore reserves in the world, and about 4 billion tonnes of Fe have been discovered thus far. The iron deposits occur in a variety of geological settings with different ages in Iran, and the majority of these are related to igneous processes. This paper describes the origin of 3 main Fe ore deposits in the country, namely Gol-Gohar, Bafq and Sangan (Fig 1).

2. Geology

The continental crust of Iran consists of different microplates that were amalgamated during the opening and closure of both the Paleo-Tethys and Neo-Tethys oceans (Berberian and King, 1981). The Ordovician–Silurian opening of Paleo-Tethys in northern Iran was followed by its northward subduction beneath the Turan plate (the southern part of Laurasia) in the late Devonian, final closure of the ocean and collision between the Iranian microcontinent and Turan plate in the late Triassic– Jurassic (Mirnejad et al., 2012). According to Davoudzadeh and Schmidt (1984), the Iran plate fragmented following collision with the Turan plate, and the Central Iranian microcontinent is one of those fragments. Following closure of Paleo-Tethys, the Neo-Tethys oceanic crust was constructed and subducted below Central Iran in the Late Jurassic to Cretaceous. The consumption of the Neo- Tethys ocean basin resulted in collision of the Iranian and Arabian plates during the Oligocene– Miocene. It has been proposed that the metamorphic and igneous rocks in the Sanandaj–Sirjan zone formed during various stages of Neo-Tethys subduction in early to late Mesozoic times. Subduction of the Neo-Tethys lithosphere beneath Central Iran resulted in the formation of the Urumieh–Dokhtar zone, a volcano-plutonic, calc-alkaline belt which is parallel to the Sanandaj–Sirjan zone (Omrani et al., 2008).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

The Gol-Gohar Fe deposit, estimated to contain 1200 Mt of ore with a grade of 53% Fe, is located at 29° 07'-29° 03'N, 55° 15'-55° 24'E, in the SE portion of the Sanandaj–Sirjan zone (Figure 1). The deposit is covered by a 100-200m-thick layer of Quaternary alluvium and surrounded by the Gol- Gohar metamorphic complex consisting of schist, amphibolite, gneiss and marble. Iron mineralization occurs in three zones of upper magnetite (high magnetite, low sulfide), oxide (hematite, goethite, limonite) and lower magnetite (high magnetite, high sulfide). The Sangan Fe deposit with a reported resource of 1200 Mt and a grade of 53% Fe, is located at 60° 24'-60° 45'N, 34° 26'-34° 33'E, in the northeast corner of the Central Iran zone (Fig. 1). The oldest rock units in the Sangan are lower Jurassic metamorphosed shale, siltstone, and sandstone, which are overlain by Middle to Upper Cretaceous limestone and dolomite in the north, and are covered unconformably by Eocene volcaniclastic and pyroclastic rocks interlayered with lava. These units are intruded by a W-E elongate body of late Oligocene (39.2-42.3 Ma) granitic rocks (Malekzadeh Shafaroodi, 2013) and cut by several syn- and post- mineralization felsic stocks and dykes. The intrusion of granitoid has metasomatized the country rocks and generated quartzite, biotite-hornfels and skarn. The three main Fe deposits in Sangan, called distal, proximal and Fe skarn, crop out in the region. The Bafq mining district, located at 55° 00'-56° 00'N, 31° 30'-32° 30'E in the Central Iran zone (Fig. 1), hosts several major Kiruna type magnetite–apatite deposits, including Esfordi, Sechahun, Choghar and Chadormalu, and contains over 2000 Mt of Fe ore (premining reserve: Choghart 216 Mt; Chadormalu 400 Mt; Se-Chahun 140 Mt; Esfordi 17 Mt). The Precambrian basement of the Bafq area consists of high- to low-grade metamorphic rocks that are covered unconformably by an Early Cambrian volcano-sedimentary sequence (529-554 Ma; Ramezani and Tucker, 2003). The metamorphic and volcano-sedimentary sequences are intruded by Cambrian granitic rocks (527-533 Ma; Ramezani and Tucker, 2003). The magnetite-apatite ore deposits in the Bafq district occur mainly within the volcano-sedimentary unit.

3. Discussion

An overview of the geology, mineralogy and geochemistry of three main Fe deposits in Iran shows that although the models for ore formation are controversial and diverse, magmatic activity can be considered as the main process responsible for the Fe mineralization. The ore in the Gol Gohar Fe deposit consists of magnetite and the gangue minerals including serpentine, talc and clinochlore are visible in the periphery of the deposit and as irregular grains filling spaces between magnetite. A number of controversial hypotheses have been suggested for the origin and evolution of the Gol-Gohar Fe deposit, including Rapitin-type, magmatic, volcano-sedimentary, and skarn type. Bayatiy-Rad et al. (2010) measured the oxygen isotope ratios of the magnetite and observed that the δ18O values range from 3.8‰ to 4.8‰, while the calculated δ18O values of the fluids in isotopic equilibrium with magnetite vary between 10‰ and 11.3‰. Such isotopic attributes indicate that the magnetite originated from magmatic fluids that were also equilibrated with sources enriched in 18O. Based on trace element variations and stable isotope compositions, Mirnejad et al. (2011) consider that the Fe deposit which was originally formed in a volcano-sedimentary environment was subsequently affected by the formation of skarn, due to the effects of magmatic activity, likely related to Neo-Tethys subduction, on the dolomitic units. These authors also consider that the early Cimmerian orogeny which metamorphosed the Gol-Gohar complex up to the amphibolite facies as the

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China result of Neo-Tethys subduction, played an important role in the remobilization and accumulation of the magnetite ore. For the Sangan deposit, models of magmatic segregation, volcano-sedimentary and skarn types have also been proposed. Boomeri et al. (2010) measured carbon and oxygen isotope compositions of calcite and dolomite grains in carbonate rocks and those interlayered with magnetite in skarn. The lowest δ18O and δ13C values of calcite and dolomite in marble are higher values than those in the Fe deposit. The latter also show a progressive decrease of δ18O and δ13C values from distal into proximal skarn, which was ascribed to the interaction of magmatic hydrothermal fluids with carbonate rocks. In addition, the presence of metasomatic silicate minerals associated with magnetite mineralization such as andradite-rich garnet, hedenbergite, and K, Cl, and F-rich amphibole in proximal skarn as well as phlogopite, chlorite, talc, and serpentine in distal skarn, point to the involvement of an igneous- hydrothermal system. The geochemical characteristics of the igneous bodies responsible for Fe mineralization in Sangan indicate that these rocks are calc-alkalic, metaluminous to slightly peraluminous, I-type granitoids, and that their parental magmas were likely generated as the result of partial melting of an enriched mantle (Malekzadeh Shafaroui et al., 2013). The mantle source was metasomatized during Tertiary subduction of the Neo-Tethys oceanic lithosphere under the Lut block. The dominant minerals in the Bafq Fe deposits are magnetite, apatite and actinolite. Most of the iron ore bodies occur as lenses of massive magnetite surrounded by ore breccia and disseminated magnetite in the host rocks. Apatite occurs in varying proportions with magnetite, ranging from sporadic grains intergrown with magnetite to relatively pure apatite veins which cut the magnetite- apatite ore. Actinolite occurs as anhedral to subhedral grains and displays continuous solid solution with tremolite. Other hydrothermal minerals are quartz, calcite, albite, K-feldspar, sericite, chlorite, talc, titanite and epidote. Monazite occurs in deposits having large apatite contents. Torabi and Lehman (2007), based on mineralogical and geochemical data as well as the monazite age of 515±21 Ma to 529±21 Ma being contemporaneous with the emplacement of the volcano-plutonic host rocks of the magnetite-apatite mineralization and with widespread sedimentation of Late Proterozoic to Cambrian evaporitic rocks in Central Iran, suggest that the magnetite-apatite deposits were likely related to large-scale brine circulation induced by felsic magmatism during the Cambrian. Moore and Modabberi (2003) measured the oxygen isotope ratios and trace element contents of apatite and magnetite from the Choghart deposit and suggested that separation of an iron oxide melt and the ensuing hydrothermal processes dominated by alkali metasomatism were both involved to different degrees in the formation of the Choghart and other similar deposits in the Bafq mining district. According to Bonyadi et al. (2011), extensive Na-rich fluid circulation produced large-scale albitization in a mixed volcano-sedimentary sequence intruded by sodic granitoids. This regional alteration was followed by deposit-related, Na–Ca alteration and magnetite–apatite mineralization at Sechahun. Although the Bafq mining district is considered by Berberian and King (1981) as part of the narrow N-S trending Pan-African rift zone, which was developed as a result of stretching of the Arabo-Iranian continental crust during an Infracambrian extensional phase, the zircon U-Pb age data of the volcano-plutonic rock association and the calc-alkaline signature of the Cambrian plutonic rocks (Ramezani and Tucker, 2003) provide evidence for subduction under the Central Iranian microplate and closure of a Proto-Tethys ocean in the Early Cambrian. The latter model is also consistent with recent reviews that have found a strong association between some iron oxide-associated mineralization and Andean margins.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Figures and Tables

Fig. 1 Map showing the position of the Gol-Gohar, Sangan and Bafq Fe deposits relative to the structural zones in Iran

References

Bayati-Rad, Y., Mirnejad, H., and Ghalamghash, J., 2010, Evaluating the origin of magnetite and sulfide phases from Gol-Gohar iron ore deposit (Sirjan): constrains from O and S isotope data: Geoscience Journal of the Geological Survey of Iran, v.89, p.139-146.

Berberian, M., and King, G.C.P., 1981, Towards a paleogeography and tectonic evolution of Boomeri, M., Ishiyama, D. T. Mizuta, D., Matsubaya, O., and Lentz, D.R., 2010, Carbon and oxygen isotopic systematics in calcite and dolomite from the Sangan iron skarn deposit, Northeastern Iran: Journal of Sciences, Islamic Republic of Iran, v.21, p.213-224

Bonyadi, Z., Davidson G. J., Mehrabi, B., Meffre, S., Ghazban, F., 2011, Significance of apatite REE depletion and monazite inclusions in the brecciated Se–Chahun iron oxide–apatite deposit, Bafq district, Iran: Insights from paragenesis and geochemistry: Chemical Geology, v.281, p.253–269

Davoudzadeh and Schmidt, K., 1984, A review of the Mesozoic paleogeography and paleotectonic evolution of Iran: Neues Jb Geol Paläont Mh, v.168,p.182–207.

Förster H. and Jafarzadeh A. The Bafq mining district in Central Iran: A highly mineralized Infracambrian volcanic field. Economic Geology, 89: 1697-1721 (1994).

Malekzadeh Shafaroudi, A., Karimpour, M. H., and Golmohammadi, A., 2013, Zircon U–Pb geochronology and petrology of intrusive rocks in the C-North and Baghak districts, Sangan iron mine, NE Iran: Journal of Asian Earth Sciences, v.64, p.256-271.

Mirnejad, H., Ghalamghash, J., Asghari. G, and Bayati-Rad, Y., 2011, An overview of the origin and evolution of Gol-Gohar Fe deposit. 30th Assembly of the Geological Survey of Iran. P. 1-7.

Mirnejad, H., Lalonde, A. E., Hassanzadeh, J., and Obeid, M., 2012, Geochemistry and petrogenesis of Mashhad granitoids: An insight into the geodynamic history of the Paleo-Tethys in northeast of Iran: Lithos, v.170, p.105-116

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Moore, F., and Modabberi, S., 2003, Origin of Chogart iron oxide desposit, Bafq mining district, central Iran: New isotopic and geochemical evidence: Journal of Sciences, Islamic Republic of Iran, v.1, p.259-269

Omrani, J., Agard, P., Whitechurch, H., Benoit, M., Prouteau, G., Jolivet, L., 2008, Arcmagmatism and subduction history beneath the Zagros Mountains, Iran: a new report of adakites and geodynamic consequences: Lithos, v.106, p.380–398.

Ramezani, J., and Tucker, R.D., 2003, The Saghand region, Central Iran: U-Pb geochronology, petrogenesis and implications for Gondwana tectonics: American Journal of Science, v.303, p.622-665.

Torabi, F. M., and Lehman, B., 2007, Magnetite-apatite deposits of the Bafq district, Central Iran: apatite geochemistry and monazite geochronology: Mineralogical Magazine, v.71, p. 347-363.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Volcanogenic massive sulfide Cu-ag mineralization in the Kharturan area, southeast of Shahrood

Fadin Mousivand Shahrood Univeristy of Technology, Iran Corresponding author’s e-mail address: [email protected]

Abstract Volcanogenic massive sulfide (VMS) mineralization in the Kharturan area, 290 km southeast of Shahrood, Iran, occurs in the Late Cretaceous volcano-sedimentary sequence in the Sabzevar subzone of the Central East Iranian Microcontinent. The main VMS deposits in the area are the Garmabe Paein and Asbkeshan bodies. The mineralization occurs as stratiform and stratabound orebodies within a specific stratigraphic horizon. The host rocks are andesitic lavas and related volcaniclastics. The orebodies from footwall to hanging wall involve four ore facies: vein-veinlets (stringer), massive, bedded and exhalative sediments (exhalite). Mineralogically, the deposits contain primary pyrite, native copper, chalcopyrite and magnetite, and secondary cuprite, covellite, malachite and Fe-Mn oxides. Textures and structures of ores involve massive, semi-massive, laminated, banded, vein- veinlets, replacement and open space-fillings. Wallrock alterations are dominated by chlorite and argillite.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Record of tectonic transformation in SW Yunnan: Geochemical and zircon U–Pb geochronological evidence from arc-derived, Late Devonian volcanogenic sediments in the southern Lancangjiang zone

Xiaomei Nie1, Qinglai Feng1,2* 1. Faculty of Earth, China University of Geosciences, Wuhan, China 2. State Key Laboratory of Geo-processes and Mineral Resources, China University of Geosciences, Wuhan, China *Corresponding author’s e-mail address: [email protected]

Abstract The Longmucuo-Shuanghu and Lancangjiang (including Changning-Menglian) suture zones in northern Tibet and western Yunnan, preserve abundant geological records of the Proto-Tethys (Late Sinian–Silurian) and Paleo-Tethys (Devonian–Triassic Oceans, suggesting a temporal and spatial connection between the two. In order to document their relationship, one must understand the tectonic transformation that took place in the Devonian. In this paper, we present new elemental data as well as LA-ICPMS U-Pb zircon ages on the volcanogenic sediments from the southern Lancangjiang zone in SW Yunnan. Three tuff samples yielded weighted mean 206Pb/238U ages of 366±5 Ma, 378±4 Ma and 382±8 Ma, documenting the Devonian age of these sedimentary rocks. Of 108 analyses, 105 on 101 grains from two sandstone samples have extremely tight age clusters, ranging from 355 Ma to 385 Ma, with mean 206Pb/238U ages of 363±3 Ma (n=63, MSWD=1.7) and 364±4 Ma (n=42, MSWD=1.8), indicating a relatively uniform source with rapid deposition. Lithologically, the studied rocks are immature volcanogenic sediments with high volcanic lithic contents (55-65%, mostly andesite, dacite, rhyolite and tuff), indicating they are closely related to island arc magmatism. Geochemically, the studied rocks have high Fe2O3T+MgO (4.19–14.03 wt%; mean 10.06 wt%), high Al2O3/SiO2 ratios (0.27–0.32; mean 0.30), and low Th/Sc ratios (0.14-0.21; mean 0.17). Chondrite-normalized REE patterns are characterized by right-sloping curves with enrichment of LREE, relatively flat HREE segments and slightly negative to positive Eu anomalies. On PAAS-normalized REE patterns, the samples display significant positive Eu anomalies, flat HREE patterns and relative depletion in LREE. These signatures imply an oceanic island arc source. A similar interpretation was reached by Dickinson and Suczek (1979). Based on all available data, a tectonic model involving eastward subduction in the Devonian can be proposed for the evolution of the Proto-Tethys Ocean. ―A missing arc‖ in western Yunnan, SW China, in the Late Devonian did not undergo contemporaneous tectonic uplift and erosion. The studied rocks are composed of Late Devonian volcanogenic sediments, sourced from a magmatic arc and deposited in a descending back- arc basin. These sedimentary rocks represent the subduction record of the Proto-Tethys Ocean in Western Yunnan, identify a hitherto unknown Late Devonian subduction event at the northeastern

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Gondwana margin, and provide reliable means of studying the relationship between the Proto-Tethys and Paleo-Tethys Oceans and the tectonic transformation that took place in SW China in the Late Devonian.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Petrography, geochemistry and U-Pb detrital zircon dating of the clastic Phu Khat Formation in the Nakhon Thai region, Thailand: implications for provenance and geotectonic setting

Pradit Nulay1,2,3*, Chongpan Chonglakmani1, Qinglai Feng2 1. School of Geotechnology, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand 2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China 3. Department of Mineral Resources, Ministry of Natural Resources and Environment, Bangkok 10400, Thailand *Corresponding author’s e-mail address: [email protected]

Abstract The clastic Phu Khat Formation is the topmost unit of the red bed sequence (mainly Khorat Group and overlying salt formation) in the Indochina Block (Heggemann, 1994). It is well exposed in the Nakhon Thai region, which is located between two tectonic terranes, the composite Nan-Uttaradit Suture and Sukhothai Zone to the west and the Loei-Phetchabun Fold Belt and Indochina Block to the east. The formation was interpreted to have been derived from both western and eastern thrust fault blocks in the Latest Cretaceous-Early Tertiary (Heggemann, 1994). However, this interpretation is principally based on surface mapping without detailed study. Therefore, the purpose of this study was to determine the provenance and tectonic setting of the Phu Khat Formation using petrography and whole-rock geochemistry integrated with U-Pb detrital zircon dating. The alluvial fan facies of the Phu Khat Formation is underlain unconformably by aeolian sandstone of the Khao Ya Puk Formation (or Phu Tok Formation). The sandstone of the Phu Khat Formation is poorly sorted and has a high content of unstable volcanic lithic fragments.

Geochemically, the tectonic setting discriminators, including the plot of K2O/Na2O ratio against SiO2

(Roser and Korsch, 1986), Al2O3/SiO2 versus (Fe2O3 + MgO), the discriminant function plot of major elements (Bhatia,1983) and the Th-Sc-Zr/10 triangular plot (Bhatia and Crook, 1986) indicate that the Phu Khat Formation accumulated in a passive margin tectonic setting. The discriminant function plot of major elements (Roser and Korsch, 1988) and the plot of La/Th ratio against Hf (Floyd and Leveridge, 1987), together with the plot of Th/Sc against Zr/Sc ratios (McLennan et al., 1993) and variations of the Eu anomaly values (Eu/Eu* 0.42 to 0.74) show that the provenance of the Phu Khat Formation consists primarily of sedimentary rocks associated with a continental volcanic arc that had been uplifted either in the western or the eastern continental terranes or both. However, the U-Pb detrital zircon dating provides clear evidence that the provenance of the Phu Khat Formation was uniquely from the western terrane where igneous activity occurred predominantly in the Middle to Late Triassic (Shichan, 2008: 2009; Khositanont, 2008; Barr et al., 2000:2006; Qian et al., 2013).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

These results indicate that while the Phu Khat Formation was accumulating in the Nakhon Thai region, the western terrane was uplifted by reactivation of the pre-existing structures probably since the Maastrichian (Ahrendt et al., 1993. Meanwhile, the eastern terrane (mainly the Loei-Phetchabun Fold Belt) was probably not uplifted until accumulation of the Phu Khat Formation was complete. Subsequently, the whole region was uplifted, forming a high mountainous area since the Ypresian (Racey et al., 1997) when Greater India collided with Eurasia. Keywords: Phu Khat Formation, Provenance, U-Pb detrital zircon dating, geochemistry

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Application of geochemical fingerprinting to mineral deposit classification and exploration

J. A. Pearce School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK Corresponding author’s e-mail address: [email protected]

Abstract Geochemical fingerprinting of igneous rocks in the Geological Record is now a well-established procedure. For lavas, methodologies are based on the so-called immobile elements, elements which are relatively unaffected by weathering and metamorphism Fingerprinting normally involves three stages: 1) classification of rock type using an immobile element proxy; 2) identification of tectonically defined magma type; and 3) petrogenetic diagrams which provide more detail on the precise tectonic setting. Of the plutonic rocks, there are usually sufficient numbers of fresh granite samples that the complete bulk-rock compositions can be used, but gabbros and peridotites are normally best-studied using resistant minerals such as clinopyroxene and spinel. Alteration is even more important around most mineral deposits, especially (but not exclusively) in the case of hydrothermal deposits. Using immobile elements to classify the rock type of highly metasomatised rocks is then particularly important. These immobile elements then provide an opportunity to classify ore deposits in terms of tectonic setting. Thus VMS deposits may be assigned a tectonic setting of formation based on geochemical fingerprinting. The same is possible for ore deposits associated with granites, gabbros and peridotites. This may be useful in the construction of accurate Ore Deposit Models. In terms of assigning probabilities of economic significance to particular compositions, this goal can presently only be achieved to a limited extent. However, there are well-defined links between host rock composition and type of mineralization.

Keywords: trace elements, fingerprinting, mineralization

1. Fingerprinting Rock Type in Highly Altered Rocks

Almost all ore-forming hydrothermal processes can completely transform the mineralogy and geochemistry of the host rock. A key part of geochemical fingerprinting is therefore to identify which elements have been mobilized and so to determine what was the original rock type. The important elements are the so-called immobile elements, typically elements in III to V oxidation states with intermediate ionic radii. To do this, we need to use immobile element proxies for the common classification diagrams. The procedure for lavas is: 1) To plot diagrams of elements which should behave in a similar way and check that their behaviour is consistent with immobility during hydrothermal processes (Cann, 1970). 2) To use an immobile element proxy for the total-alkali-silica (TAS) diagram (such as Zr/Ti v Nb/Y: Pearce, 1996) to classify the rock type according to the IUGS convention.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

If the rock type can be shown to be of volcanic arc affinity, it is necessary to use an immobile proxy for the K2O-SiO2 arc classification diagram (such as Th v Co: Hastie et al., 2007). 3) Compare the actual composition with the inferred original composition and so quantify the extent of element mobility and determine whether the type and extent of geochemical mobility has economic significance. 4) Check the petrography for phenocrysts that have escaped complete replacement (e.g. clinopyroxene, spinel) as these can also be indicators of tectonic setting. Proxies are also available for plutonic igneous rocks, though the coarse grain size and lower permeability usually means that they are less necessary. However, it is possible to use immobile elements to classify cumulate gabbros and ultramafic rocks, by using immobile element proxies for minerals, such as Sc for clinopyroxene, Co for olivine and Al for feldspar. Having evaluated mobility and assigned a rock type, the tectonic setting can be investigated. This depends on the type of ore deposit. A few examples are covered here.

2. Fingerprinting Lavas: Volcanigenic Massive Sulphide (VMS) Deposits

For VMS-type deposits, it has long been apparent that mineralization may be associated with almost any magma type (Pearce and Gale, 1977), but immobile element fingerprinting does have uses, not only in giving a name to highly altered rocks and quantifying alteration through immobile-mobile element relationships (as described above), but also: 1) placing the district in a tectonic context and, 2) identifying lava unit boundaries, which are often the preferential sites of mineralization. Then a subduction/crustal contribution proxy diagram (Th/Yb-Nb/Yb) and melting depth proxy diagram (Ti/Yb v Nb/Yb) can be used to identify setting (Pearce, 2008), as well as resolve in more detail the relationship between the basalts and rhyolites of what are commonly bimodal volcanic sequences (Schandl and Gorton, 2002). These results can then be integrated with geological criteria in making a final interpretation. Theoretically, the extent of melting in these settings results primarily from a combination of mantle temperature, lithospheric extension (beta-value) and fluid content, while the extent of crustal input depends primarily on magmatic heat flux, crustal composition, geothermal gradient and availability of crustal fluid. Modelling of the geochemical effects of these processes allows the discrimination diagrams to be properly interpreted. Applying these methodologies to lavas associated with VMS deposits provides the basis for a number of most-probable interpretations as follows. 1) Cyprus-type deposits occupy a near-trench setting following subduction-initiation roll-back with slab-edge volcanism providing additional thermal input. 2) Baimak-type deposits from the Urals occupy a more advanced subduction-initiation setting at the boundary between slab roll-back and proto-arc development. 3) Kuroko-type and Flin-Flon type deposits occupy extensional supra-subduction zone settings (possibly arc-capture rather than back-arc) in more developed continental and oceanic arcs respectively. 4) Besshi-type deposits formed at a normal mid-ocean ridge setting and were accreted to the Japanese margin. 5) Iberia-type deposits formed in post-collisional basins. 6) A wide range of VMS-Sedex deposits also formed in association with volcanism at passive margins and in aulacogens and similar sedimentary basins. 7) Noranda-type deposits formed in extensional basins within plume-derived volcanic terranes. The fact that many of these interpretations are at odds with existing VMS classification schemes and Mineral Deposit Models suggests that these schemes and models need to be revisited.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

3. Fingerprinting Granites: Porphyry Copper Deposits

The well-known granite discrimination diagrams based on Y, Nb and Rb have been used to predict that type of mineralization likely to be associated with a granite of given composition. Most used is the plot of Rb v (Y+Nb) (Pearce et al., 1984; Pearce, 1996), which distinguishes granites of different settings: volcanic arc, ocean ridge, intraplate, syn-collision and post-collision. Christiansen and Keith (1995) noted that it also, to a certain extent, distinguishes granites according to the type of ore deposit hosted by that granite. For example: Mo deposits are typically associated with continental arc and post-collision granites, Sn deposits with syn-collision and intraplate granites, and Cu-Au with island arc granites. For some deposits, more detailed petrogenetic diagrams have proved productive: for example, granites associated with porphyry copper deposits have been shown not just to have volcanic arc character, but also a low-HREE (adakite) character which may relate to a particular, if debated, stage of subduction evolution. This can be combined with other geochemical characteristics related to fluid build up and loss from the cooling pluton, as in the Y-Mn diagram aimed as separating productive and non-productive intrusions (Baldwin and Pearce, 1982).

4. Fingerprinting Peridotites: Podiform Chromite Deposits

For mafic and ultramafic plutonic hosts, mineral compositions are most useful. This is particularly true of chromites where the Y-site elements (Al, Cr, V, FeIII, Ga, Ti) provide a detailed picture of the tectonic history of the host rock. Ophiolitic peridotites can be separated into suprasubduction zone and MORB-type settings and then further classified according to the setting of the residual mantle and the setting any melt that has interacted with it. Geochemical fingerprinting to date has shown a link between podifirm chromites and marginal basin settings (Pearce et al., 1984; Roberts, 1988), and further suggested that most of the largest podiform chromite deposits, and particularly the larger ones, are associated with mantle that formed in a ridge setting but was then fluxed by arc magma following subduction initiation (Dare et al., 2008). In mafic plutons, too, chromites provide evidence of oxygen fugacity and degree of melting of their parent magma which, combined with clinopyroxene analyses, can usefully distinguish plume from arc settings and hence identify mineralization potential.

References

Baldwin, J.A. and Pearce, J.A., 1982. Discrimination of productive and non-productive porphyritic intrusions in the Chilean Andes. Econ. Geol. v.77, p.664-674.

Christiansen, E.H. and Keith, J.D., 1996. Trace element systematics of silicic magmas: a metallogenic perspective. Geol. Assoc. Canada Spec. Publ. v.12, p.115-151.

Dare, S.S., Pearce, J.A., McDonald, I. and Styles, M.T., 2008. Tectonic discrimination of peridotites using fO2- Cr# and Ga-Ti-FeIII systematics in chrome-spinel. Chem. Geol. v.261, p.199-216.

Hastie, A.R., Kerr, A.C., Pearce, J.A. and Mitchell, S.F., 2007. Classification of altered volcanic island arc rocks using immobile trace elements: Development of the Th-Co discrimination diagram. J. Petrol. v.48, p.2341- 2357.

Pearce, J.A. and Gale, G.M., 1977. Identification of ore-deposition environment from trace element geochemistry of associated igneous host rocks. In: Volcanic Processes in Ore Genesis. Geol. Soc. Lond. Spec. Publ. v.7, p.14-24.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Pearce, J.A., Harris, N.B.W., and Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J. Petrol. v.25, p.956-983.

Pearce, J.A., Lippard, S.J. and Roberts, S., 1984. Characteristics and tectonic significance of supra-subduction zone ophiolites. Geol. Soc. Lond. Spec. Publ. v.16, p.77-94.

Pearce, J.A., 1996. A user’s guide to basalt discrimination diagrams. In: Trace element geochemistry of volcanic rocks: implications for massive sulphide exploration. Geol. Assoc. Canada Spec. Publ. v.12, p.79-113.

Pearce, J.A., 2008. Geochemical Fingerprinting of oceanic basalts with implications for the classification of ophiolites and search for Archean oceanic crust. Lithos v.100, p.14-48.

Pearce, J.A., 2014. Immobile element fingerprinting of ophiolites. Elements v.10, p.97-104.

Roberts, S., 1988. Ophiolitic chromitite formation: a marginal basin phenomenon. Econ. Geol. v.83, p.1034- 1036.

Schandl, E.S. and Gorton, M.P., 2002. Application of high field strength elements to discriminate tectonic settings in VMS environments. Econ. Geol. v.97, p.629-642.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Geochemical and geochronology constraints on the origin of the meta-mafic volcanic rocks in the Tengtiaohe Zone, SW China

Xin Qian1, Qinglai Feng1*, Yuejun Wang2, Zhibin Zhang3 1. State Key Laboratory of Geological Process and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, China 2. Department of Earth Sciences, Sun Yat-Sen University, Guangzhou, 510275, China 3. Geological Survey of Yunnan Province, Kunming, 650011, China *Corresponding author’s e-mail address: [email protected]

Abstract It is possible that Late Permian basalts and ultramafic-mafic complexes exposed at Jinping (southeastern Yunnan province) and northern Vietnam constitute a westerly extension of the ELIP. The meta-basic volcanic rocks together with Late Permian flood basalts from the Tengtiaohe Zone yield zircon U-Pb ages of 258.4±2.4 Ma and 258.6±2.6 Ma, essentially the same as the ages of flood basalts of the ELIP, and similar to basaltic rocks and komatiites from the Song Da Zone in northern Vietnam, suggesting a Late Permian origin rather than the Early Permian and Early Carboniferous ages as previously thought. They basalts are strongly enriched in LREE relative to HREE and display trace element patterns similar to the OIB pattern, are enriched in LILE and show very negative Sr anomalies. Their magmas were derived from an enriched and deep mantle source without significant crustal contamination. These meta-mafic volcanic rocks formed in ELIP and do not belong to the Ailaoshan ophiolite,and their geochemical signatures are similar to these high-Ti flood basalts in the Song Da Zone. The Tengtiaohe Zone is not an ophiolite zone and can link to the Song Da Zone in northern Vietnam. Keywords: meta-basic volcanic rocks, geochemical characteristics, zircon U-Pb dating, Emeishan large igneous province, Tengtiaohe Zone, SW China

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Porphyry Cu-Au, Mo and Cu-Mo metallogenic systems in the Qinghai- Tibetan Plateau from subduction and continental collision to transitional settings

Kezhang Qin1*, Guangming Li1, Junxing Zhao1, Jinxiang Li2, Bo Xiao1, Lei Chen1, Mingjian Cao1 1 Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China 2 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China *Corresponding author’s e-mail address: [email protected]

Abstract Over the last ten years China has made dramatic progress in exploration and ore discoveries in the Qinghai-Tibetan Plateau. These mineral deposits are associated with Mesozoic Tethys oceanic subduction and Cenozoic India-Eurasia continental collision. Because of this distinctive tectonic evolution, the geology and mineralization of these ore deposits are complex and diverse. However, the metallogeneses under different tectonic settings are poorly understood so far, due to limited exploration and a lack of systematic studies. The metallogenic framework in Tibet can be divided into four principal mineralization epochs. (1) An oceanic subduction setting (≧125-115 Ma) represented by the Duolong super-large, gold-rich, porphyry Cu deposit and the Naruo high-sulfide porphyry Cu(Au) deposit hosted in quartz diorite and granodioritic porphyry in the Bangong arc of northern Tibet (Li et al., 2012; Li et al., 2012, 2013). (2) A major-collisional setting (∼ 65–50 Ma) as exemplified by the Sharang porphyry Mo deposit and the Yaguila skarn Pb-Zn deposit associated with granite porphyry and quartz porphyry in the northern Gangdese terrane (Qin et al., 2008; Zhao et al., 2012, 2014), as well as the Yulong-Narigongma Cu-Mo ore belt (40-41 Ma) in east Tibet-south Qinghai that represents an old rejuvenated orogenic belt (Li et al., 2013). (3) A late-collisional transform structural setting (~30–23 Ma) in which occurs the Nuri skarn-porphyry Cu-W-Mo deposit (Li et al., 2006; Chen et al., 2012) and (4) a Miocene post-collisional transitional setting from compression to extension (~18–14 Ma) in which the Qulong giant porphyry Cu-Mo deposit (﹥10Mt

Cu) was formed (Xiao et al., 2012, Qin et al., 2014) and the Jiama skarn-porphyry Cu-Pb-Zn-Mo deposit (Tang et al., 2013) associated with monzogranitic to granodioritic porphyry in the central Gangdese belt of southern Tibet. Petrographic, geochemical and Sr-Nd-Hf isotopic correlations among these deposits indicate that Au-rich porphyry Cu deposits formed in the Neo-Tethys oceanic subduction regime and that highly-evolved magmas and old continental materials may have been the magmatic sources for the Mo mineralization. In contrast, the post-collisional adakitic porphyry Cu- Mo deposits were derived from partial melting of thickened juvenile arc lower crust. Each stage of

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China porphyry mineralization represents an individual uplift event, thus, the building of the Tibet Plateau may be due to multistage and diverse crustal thickening and uplifting. Systematic descriptions of the geology, mineralization, hydrothermal alteration and ore-forming fluids of the early Cretaceous Duobuza gold-rich porphyry copper district in the Bangongco Mesozoic arc have been published by Li et al. (2012). Intense hydrothermal alteration occurred in the granodiorite porphyries and at the contact zone with volcanic rocks. Four main hypogene alteration zones are distinguished at Duobuza; early-stage potassic alteration with dense magnetite and quartz- magnetite veining; propylitic alteration, extensive chloritization-silicification superposed on the potassic alteration; and final-stage argillic alteration overprinting all the earlier alteration. Cu coexists with Au, which indicates their simultaneous precipitation. The early stage hydrothermal fluids were responsible for the potassic alteration and Cu-Au mineralization. The enrichment of copper and gold in the potassic alteration zone indicates that that the K-silicate alteration was the main mineralization stage. The occurrence, mineralogical assemblages and mineral chemistry of secondary albite, K- feldspar, biotite, chlorite, and apatite in the Early Cretaceous Duolong superlarge, gold-rich porphyry copper deposit has also been reported by Li et al. (2012). In this deposit hydrothermal alteration is divided into potassic, argillic and propylitic zones from the ore-bearing granodiorite porphyry and quartz diorite porphyrite center outward and upward. All the biotites lack F, but have high Cl contents (0.19-0.26%), suggesting a significant role for chloride complexes in transporting and precipitating copper and gold. Chlorite is present in all the alteration zones, and is mainly pycnochlorite. Fe3+/Fe2+ ratios of chlorites correlate negatively with AlIV, suggesting that the oxygen fugacity of the fluids increased with decreasing temperature. Apatite mineral inclusions in the biotite phenocrysts show high SO3 content (0.44-0.82 wt%) and high Cl content (1-1.37 wt%), indicating that the host magma had a high oxidation state and was enriched in S and Cl. The low concentration of SO3 in the hydrothermal apatite compared to the magmatic apatite may reflect a decrease of oxygen fugacity and S content in the hydrothermal fluid, which was caused by the abundant precipitation of magnetite. In the Gangdese metallogenic belt, newly-discovered deposits related to Neotethyan subduction and the following India-Asia continental collision are more commonly reported than Miocene porphyry- and skarn-type deposits. The first porphyry Mo deposit discovered in Gangdese belt, the Sharang deposit, is hosted in a multi-stage composite complex emplaced in the Upper Permian Mengla Formation in the northern part of the Gangdese metallogenic belt. Intrusive rocks of the ore- forming stage are mainly granite, granite porphyry, porphyritic granite and fine-grain granite porphyry. The main mineralization is Mo-bearing veins, stockworks of quartz+molybdenite±sulfide (other gangue minerals) veins, and ribbon-textured quartz+molybdenite±pyrite veins. Less common disseminated mineralization is also present. Based on field work and geochronologic studies, the Sharang complex has undergone two major tectonic episodes in the Tibet orogen: Paleocene-Eocene

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China main-stage continent-continent collision (56-51 Ma) and Miocene post-collisional activity (22-18 Ma). The Sharang porphyry Mo deposit was formed in the main stage of India-Asia continental collision (65-50 Ma), with ages of the ore-forming rocks of 52.9-51.6 Ma) and the mineralization of 52.3 Ma. Therefore, the ore-forming, magmatic-hydrothermal evolution probably persisted for 1.3 Ma. Negative εHf(t) values in the ore-forming rocks differ from those of pre-ore and post-ore rocks, indicating old ancient continental materials, probably basement of the Lhasa terrane, may have played an important role in the formation of the Sharang ore-forming intrusions and Mo mineralization. The intrusive sequence, petrography, trace element and Sr-Nd isotope geochemistry of the Eocene Sharang porphyry Mo deposit in the Gangdese metallogenic Belt, formed during the main collisional stage, was reported by Zhao et al (2012, 2014). The geochemical data suggest a highly oxidized and evolved magma and some old continental materials may have been the magma source for the Sharang intrusive complex. We conclude that melting of ancient continental crust and juvenile crust from of a metasomatized mantle wedge in the process of Neotethyan oceanic slab roll-back after continent-continent collision could have been the main tectono-magmatic process involved in the formation of the Sharang Mo deposit, and other Eocene deposits in the southern Gangdese belt. In addition, Hf isotopic characteristics of porphyry deposits formed during the continental collisional and post-collisional environments, mainly in Gangdese and Qinling belt, reflect variable degrees of crust-mantle interaction. We collected new data on the nature of the ore-forming fluids, their evolution and the mechanism of formation for the Oligocene Mingze porphyry Mo deposit (~30 Ma, Fan et al., 2012) and the Nuri large skarn-porphyry Cu-W-Mo deposit (`23Ma) in the southern subzone of the Gangdese metallogenic belt (Chen et al.,2012). There are three types of mineralization in the Nuri deposit: skarn, vein and porphyry type. Detailed petrographic observations and microthermometric study of fluid inclusions in garnet, scheelite and quartz from the different stages reveal that the homogenization temperatures ranged from 280-386°C in the skarn stage, but decreased to 160-280°C in the quartz- carbonate stage. Fluid salinities were in the range of 2.9- 49.7 wt % to 1.2-15.3 wt % (NaCl) equiv.

Analyses of CO2-rich inclusions suggest that the ore-forming process occurred at depths of 0.9-2.2 km. The ore-forming fluid flow through the host carbonate rocks resulted in the formation of layered skarn and generated CO2 and other gases. The CO2 escaped from the fluid by boiling, resulting in scheelite precipitation. The fluid mixing and boiling reduced the solubility of metal sulfides and lead to precipitation of chalcopyrite, molybdenite, pyrite and other sulfides. Xiao et al. (2012) and Qin et al. (2014) confirmed the abundant presence of magmatic anhydrite and hydrothermal anhydrite in the Miocene Qulong porphyry Cu-Mo deposit, the largest porphyry- type deposit in China (11Mt Cu), usually in association with clusters of sulfur-rich apatite, which is direct evidence of a highly oxidized and sulfur-rich, magmatic-hydrothermal condition in non- subduction settings. Microthermometric study suggests that copper-bearing sulfides precipitated at about 320-400°C in A and B veins. Fluid boiling is assumed for the early stage of mineralization, and

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China these fluids may have been trapped at about 35-60 Mpa and 460-510°C and 28-42 Mpa at 400-450°C, corresponding to trapping depths of 1.4-2.4 km and 1.1-1.7 km, respectively.

References

JX Li, KZ Qin, GM Li, JP Richards, JX Zhao, MJ Cao.2014.Geochronology, geochemistry, and zircon Hf isotopic compositions of Mesozoic intermediate-felsic intrusions in central Tibet: Petrogenetic and tectonic implications. Lithos, 198–199: 77–91.

JX Zhao, KZ Qin, GM Li, JX Li, B Xiao, L Chen, YS Yang, C Li, YS Liu. 2014. Collision-related genesis of the Sharang porphyry molybdenum deposit, Tibet: Evidence from zircon U-Pb ages, Re-Os ages and Lu-Hf isotopes. Ore geology Review, 56:312-326.

Li JX. Qin KZ, Li G.M, Xiao B, Zhao JX, Cao M.J, Chen L.2013. Petrogenesis of ore-bearing porphyries from the Duolong porphyry Cu-Au deposit, central Tibet: Evidence from U-Pb geochronology, petrochemistry and Sr-Nd-Hf-O isotope characteristics.Lithos, 160-161：216 - 227

Zeng QD, Liu JM, Qin KZ, Fan HR, Chu SX, Wang YB, Zhou LL. 2013. Types, characteristics, and time–space distribution of molybdenum deposits in China. Intern Geol Rev, 55(11): 1311-1358.

Li JX, Qin KZ, Li GM, Cao MJ, Xiao B, Chen L, Zhao JX, Evans NJ, McInnes IA..2012. Petrogenesis and thermal history of the Yulong porphyry copper deposit, Eastern Tibet: insights fromU-Pb and U-Th/He dating, and zircon Hf isotope and trace element analysis. Mineralogy and Petrology, 105:201–221

Xiao B, Qin KZ, Li GM, Li JX, Xia DX, Chen L and Zhao JX.2012. Highly oxidized magma and fluid evolution of Miocene Qulong giant porphyry Cu- Mo deposit, southern Tibet, China . Resource Geology, 62 (1): 4-18.

Chen L, Qin KZ, Li JX, Xiao B, Li GM, Zhao JX and Fan X.2012.Fluid inclusions and hydrogen, oxygen, sulfur isotopes of Nuri Cu-W-Mo deposit in the southern Gangdese, Tibet. Resource Geology, 62(1): 42-62.

LI GM, Li JX, QinKZ, Duo J, Zhang TP, Xiao B and Zhao JX.2012. Geology and hydrothermal alteration of the Duobuza gold-rich porphyry copper district in the Bangongco metallogenetic belt, northwestern Tibet. Resource Geology, 62(1): 99-118

Qin Kezhang.2012.Preface for Thematic Articles “Porphyry Cu-Au-Mo deposits in Tibet and Kazakhstan”. Resource Geology, 62(1):1-3.

Li JX, Qin KZ, Li GM, Xiao B, Chen L Zhao JX.2011.Post-collisional ore-bearing adakitic porphyries from Gangdese porphyry copper belt, southern Tibet: melting of thickened juvenile arc lower crust. Lithos, 126 （3-4）:265-277.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

New perspectives on ophiolite formation: evidence from UHP, highly reduced and crustal minerals in mantle peridotites and podiform chromitites

Paul T. Robinson*, Jingsui Yang, Fahui Xiong and Xiangzhen Xu CARMA, State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China *Corresponding author’s e-mail address: [email protected]

Abstract The presence of ultrahigh pressure (UHP), highly reduced, and crustal-type minerals in podiform chromitites and mantle peridotites of many ophiolites in Tibet, Myanmar, Russia and Northern China is difficult to reconcile with evidence for ophiolite formation in suprasubduction zone mantle wedges. The UHP and highly reduced minerals must have crystallized at least in the lower parts of the upper mantle and perhaps even deeper. In-situ grains of these minerals in magnesiochromite are hosted in small, circular to irregular patches of amorphous carbon, indicating the former presence of a C-rich fluid during or after crystallization of the magnesiochromite grains. Many chromitites and peridotites also contain crustal-type minerals, (feldspar, amphibole, mica, quartz, corundum, kyanite, apatite, zircon, Fe-Mn garnet), many of which would presumably be unstable in UHP and highly reduced environments. Most podiform chromitites in ophiolites are Cr-rich (Cr#75-85) unlike those recovered from in-situ oceanic lithosphere (Cr#<60), although high-Al varieties do exist. Podiform chromitites are rarely distributed evenly along tectonic belts but rather tend to cluster in individual ophiolitic blocks or massifs, suggesting formation by non-steady state processes. In most ophiolites there is abundant evidence for modification of peridotites and magnesiochromite grains by suprasubduction zone (SSZ) melts and fluids. Clearly, ophiolite formation and the generation of podiform chromitites must be a complex, multi-stage process. We propose a model that attempts to reconcile some of the contradictory evidence outlined above. a) Subduction of oceanic slabs during at least the last 2500 m.y. of earth history would have introduced crustal minerals into the upper mantle and transition zone. Being unstable in such environments, some of the crustal minerals would be broken down and recrystallized, while others may have been encapsulated in crystallizing magnesiochromite grains. b) UHP and highly reduced minerals are transported upward from the transition zone or lower mantle by C-rich fluids, which are trapped or encapsulated in magnesiochromite grains growing above the transition zone. c) Upwelling of the mantle peridotites beneath oceanic spreading axes carries the magnesiochromite grains containing inclusions of UHP, highly reduced and some crustal- type

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China minerals to shallow levels where they may form small podiform chromitites or remain distributed in the host peridotites. d) Formation of a new, intraoceanic subduction zone traps the upper mantle peridotites in a suprasubduction wedge where they are modified by SSZ melts and fluids. The magnesiochromite grains become progressively richer in Cr by melt-rock reaction and may be physically redistributed into podiform bodies. Slab rollback and slab tear allow upwelling of asthenospheric mantle, adding Cr to the SSZ mantle wedge and stimulating crystallization of magnesiochromite grains to produce abundant chromitites e) The crystallizing magnesiochromite grains encapsulate unstable crustal minerals derived from the downgoing slab, thus preserving them in the chromitites, along with UHP and highly reduced grains encapsulated at an earlier stage of evolution. f) With closure of the ocean basin low-density oceanic or continental crust is subducted beneath the mantle wedge allowing it to be uplifted and emplaced as an ophiolite on a continental margin or island arc.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Geodynamics of the inner and outer Zagros Ophiolite belt (Iran), inferred from the chemical composition of Cr-spinel in chromitites

Fatemeh Sepidbar*, Hassan Mirnejad Department of Geology, University of Tehran, Tehran, Iran *Corresponding author’s e-mail address: [email protected]

Abstract The composition of chromian spinel in chromitites and their host peridotites from the Neyriz and Nain ophiolites in the Zagros ophiolite belt shows that there are remarkable compositional variations between these two ophiolites. The Nain ophiolite in the NW is dominated by harzburgite with limited and small-size chromitite pods, whereas the Neyriz ophiolite to the SW contains both harzburgite and dunite with a large potential for high-Cr chromitites. The Neyriz chromitites in the southern sectors (outer Zagros) are the product of typical fore-arc-related boninitic melts, whereas the Nain chromitites of the inner Zagros probably originated in a back-arc basin from island arc tholeiite and MORB-like magmas. Keywords: Mineral chemistry, Cr-spinel, ophiolites of Iran, back-arc basin, fore-arc basin

1. Introduction

Harzburgites are the dominate mantle rocks in both the inner and outer Zagros ophiolite belt in the central Iran micro-continental block (CIM), whereas lherzolite and gabbro are subordinate. Dunites are abundant only in the outer Zagros belt. Crustal sequences of these ophiolites are dominated by pillow lavas, but more-evolved felsic rocks (e.g. plagiogranites) and sheeted dyke complexes are also present. Despite some similarities, there are significant differences between these two groups of Zagros ophiolites, e.g., chromitite bodies are small and limited in the inner Zagros ophiolites (e.g. Nain and Dehshir ophiolites) whereas large chromitite pods and residual and cumulate dunitic lenses are restricted to the outer Zagros ophiolites (Agard et al., 2011; Ghazi et al., 2010, 2011; Rajabzadeh, 1998; Shafaii Moghadam and Stern, 2011a,b). The focus of this paper is to describe the mineral chemistry of a set of Cr-spinels from the Nain and Neyriz ophiolites, in central and southern Iran, respectively, to determine their parental magma compositions and geotectonic settings.

2. Geology

The Nain ophiolitic complex is located at the northwest margin of the CIM (Fig.1). It extends from NNW to SSE and is surrounded by Tertiary sedimentary rocks in the east and volcanic rocks in the west. The mantle sequence is composed of pyroxenite lenses, orthopyroxenite veinlets, impregnated gabbro, pegmatite gabbro and diabasic–gabbroic dykes, whereas the crustal sequence consists of gabbro, diabase, dyke swarms, pillow lava, pelagic limestone and radiolarite (Ghazi et al., 2010). The Neyriz ophiolites are located in western border of Zagros Suture Zone farther south

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

(Rajabzadeh et al., 2013). (Fig.1), and their mantle sections are composed of homogeneous harzburgite that contains patches of lherzolite in their lower parts (Rajabzadeh et al., 2013).

3. Discussion

Microprobe analyses show that the chromitites (including hydrous silicate-inclusions, Rajabzadeh, 1998) from the Neyriz ophiolite have significantly higher Cr#s (73–82) and Mg#s (62–

71), and lower in Al2O3 (9.1–13.9 wt%) and TiO2 (up to 0.08 wt%) than those of the Nain ophiolite

(Cr#: 59–63, Mg#: 60–68, Al2O3: 18.9–22.3 wt%, TiO2: 0.13–0.33 wt% for chromitite patches and

Cr#: 69–73, Mg#: 68–70, Al2O3: 13.6–15.0 wt%, TiO2: 0.18–0.28 wt% for chromitite lenses) (Ghazi et al., 2010, 2011, Rajabzadeh et al., 2013). The compositions of the chromian spinels from Neyriz plot in the field of typical fore-arc-related boninites, and those of the Nain show affinities to island arc tholeiite (IAT) or MORB-like magmas (Figs. 2 and 3).

The trend of increasing Cr# up to 79 and low TiO2 and Al2O3 contents of spinel from lherzolite to dunite in Neyriz suggest a linkage to a boninitic melt in a fore-arc setting whereas those of the Nain ophiolite plot mainly in the field of back-arc basins (Fig. 3).

4. Geodynamic synthesis

Two controversial models have been proposed for the tectonic setting of the Central Iran ophiolites; 1) that the inner and outer Zagros Ophiolite Belts are remnants of two distinct Late Cretaceous oceanic basins, or 2) a single disrupted one. Based on the similarity in ages for the inner and outer belt ophiolites, Shafaii Moghadam et al. (2010) and Shafaii Moghadam and Stern (2011a,b) suggested that these ophiolites formed in a single fore-arc tectonic setting, essentially where they are seated today, and were attached to the southern margin of Eurasia during subduction initiation of Neo- Tethys. In contrast, on the basis of geochemical characteristics of the peridotites and chromitites of the Nain ophiolite, Ghazi et al. (2010, 2011) suggested that this ophiolite was probably formed in a back- arc basin. These authors also proposed that the subduction was slow and that the mantle source beneath the Nain back-arc basin was influenced by slab-derived fluids, which changed progressively from arc-like to depleted MORB-like composition (Rajabzadeh et al., 2013). Shirdashtzadeh et al. (2011) also suggested a MORB origin for chromian spinels in pillow lavas of the Nain ophiolite. Clearly, the Neyriz chromitites formed in a different geotectonic environment than those of the Nain ophiolite, which is consistent with the model proposed by Ghazi et al. (2010(. Boninitic melts are abundant in fore-arc settings (Bedard et al., 1998), and we suggest that interaction between residual peridotites and boninitic melts in such an environment formed the large, high-Cr chromitites in the Neyriz ophiolite. In contrast, the limited, small chromitites in the Nain ophiolite probably formed from IAT and MORB-like melts in a back arc basin (Fig. 4) (Rajabzadeh et al., 2013). During subduction of the Neo-Tethys oceanic lithosphere beneath the southern margin of the CIM, a back-arc basin formed in the north and a fore-arc environment formed in the south. As a result, trenchward Neyriz peridotites were largely impregnated by percolating fore-arc-related hydrous boninitic melts, producing large and abundant chromitite pods. In contrast, oceanic back-arc basin was affected by smaller volumes of slab-released fluids/melts with MORB- or IAT-like affinity.

Figures and Tables

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig.1. Fig1:Distribution Distributio of then of Nain Nain and and Neyriz Nayriz ophiolite ophiolite complexes complexes in Iranin Iran.

Fig. 2. Compositional variations of Cr# versus Mg# in Fig. 3. Compositional variation of spinel from the spinel from the Neyriz and Nain ophiolites. Dat for the Neyriz ophiolite. (a) TiO2 versus Cr#. Data sources are Nain chromitites are from Ghazi et al. (2011), and data the same as for Fig. 2. for the Neyriz chromitites are from Rajabzadeh et al. 2013

Fig. 4 A possible sketch model for tectonic settings of the Neyriz and Nain chromitites (modified from Xia et al. (in Rajabzadeh et al., 2013)).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

References

Agard, P., Omrani, J., Jolivet, L., Whitechurch, H., Vriealynck, B., Spakman, W., Monie,P., Meyer, B., Wortel, R., 2011. Zagros orogeny: a subduction-dominated process. Geological Magazine 148 (5–6), 692–725.

Bedard, J.H., Lauzier, K., Tremblay, A., Sangster, A., 1998. Evidence from Betts Cove ophiolite boninites for forearc seafloor-spreading. Tectonophysics 285, 233–245.

Ghazi, J.M., Moazzen, M., Rahgoshay, M., Shafaii Moghadam, H., 2010. Mineral chemical composition and geodynamic significance of peridotites from Nain ophiolite, Central Iran. Journal of Geodynamics 49, 261– 270.

Ghazi, J., Moazzen, M., Rahgoshay, M., Shafaii Moghadam, H., 2011. The geodynamic of the Nain ophiolites, central Iran: evidences from chromian spinel in the chromitites and associated rocks. In ofiliti, 36: 59-76.

Rajabzadeh, M.A., 1998. Mineralisation en chromite et elements du groupe du platine dans les ophiolites d’Assemion et de Neyriz, ceinture du Zagros, Ph.D Thesis. Polytechnic University of Lorraine.

Rajabzadeh, M. A., NazariDehkordi, T., Caran, S., 2013. Mineralogy, geochemistry and geotectonic significance of mantle peridotites with high-Cr chromitites in the Neyriz ophiolite from the outer Zagros ophiolite belts, Iran. Journal of African Earth Sciences. 78: 1-15

Shahabpour, J., 2005. Tectonic evolution of the orogenic belt in the region located between Kerman and Neyriz. Journal of Asian Earth Science 24, 405–417.

Shafaii Moghadam H., 2010. The Dehshir Ophiolites (Central Iran): Geochemical constraint on the origin and evolution of the Inner zagros ophiolite belt", GSA Bulletin 122, 1516–1547.

Shafaii Moghadam, H., Stern, R.J., 2011a. Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone. Geological Magazine 148 (5–6), 762– 801.

Shafaii Moghadam, H., Stern, R.J., 2011b. Late Cretaceous forearc ophiolites of Iran. Island Arc 20, 1–4.

Shirdashtzadeh, N., Torabi, G., Arai, S., 2011. Two Mesozoic oceanic phases recorde in the Nain and Ashin- Zavar ophiolitic melanges (Isfahan Province, Central Iran). Ofioliti 36 (2), 191–205.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Petrography and mineral chemistry of volcanic rocks south of Bardsir (Dahaj-Sarduieh, Iran): evidence for magma mixing

Fatemeh Sepidbar*, Hassan Mirnejad Department of Geology, University of Tehran, Tehran, Iran *Corresponding author’s e-mail address: [email protected]

Abstract The Shirinak volcanic rocks are located in south-east Bardsir (Kerman Province). Geologically, the area is part of the Urumieh-Dokhtar volcanic belt, which is known as the Dahaj–Sarduieh belt in Kerman Province. The studied lavas are porphyritic with phenocrysts of plagioclase, clinopyroxene and olivine set in a microlithic and fine–grained matrix. On the basis of petrographic observations and electron microprobe analyses the plagioclases are labradorite-bytownite with sieve textures due to thermal and compositional magma mixing. On the other hand, the clinopyroxenes are augite and their physical and chemical conditions indicate formation at different depths in the ascending magma under oxygenated condition with H2O ranging up to 10 wt%. The Cpx thermometry yields temperatures of 550-1110ºC. The clinopyroxene compositions suggest formation from a mafic magma with tholeiitic to calc-alkaline affinities in a volcanic arc. Keywords: clinopyroxene, sieve texture, mineral chemistry, volcanic arc, Urumieh-Dokhtar

1. Introduction

Mineral chemistry is an important petrogenic indicator in igneous rocks. It is important for deducing the condition during magma crystallization (e. g., Orberger et al., 1995), and is important for identifying the tectonic setting in which the magmatism occurred. This paper describes the origin of volcanic rocks in the Dahaj-Sardueieh (Uroumieh-Dokhtar belt) using both petrographic and mineral compositional data..

2. Geology and petrography

Subduction of Neo-Tethyan lithosphere beneath Central Iran resulted in the formation of the Urumieh–Dokhtar zone, a calc-alkaline, volcano-plutonic belt which is parallel to the Sanandaj–Sirjan zone (Omrani et al., 2008). Volcanic rocks southeast of Bardisir are part of the Urumieh-Dokhtar zone in Iran that is named the Dahaj-Sarduieh belt in Kerman Province. According to their whole-rock chemical compositions (Naderi, 2013), the volcanic rocks have calc-alkaline to tholeiitic affinities. These rocks are mainly composed of basalt and basaltic andesite. The basalts have porphyritic textures, with microphenocrysts of olivine (10%) plagioclase (up to 50%) and clinopyroxene (15%). Basaltic andesites are mainly composed of plagioclase (even up to 80%), clinopyroxene (15%) and olivine (less than 5%). The plagioclases show mesh, dusty, zoned and sieve textures (Fig.2), indicating disequilibrium with the melt from which they crystallized, possibly due to replenishment of the

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China magma chamber and magma mixing, variations water pressure, decompression during rapid ascent of the magma and fractional crystallization.

3. Discussion

An overview of the geology, mineralogy and geochemistry of the igneous rocks in the Urumieh- Dokhtar zone show that subduction of Neo-Tethys can be considered as the main process responsible for the magmatic activity. Geochemical investigations reveal that the studied rocks belong to a medium–K, calc-alkaline magmatic series with some tholeiitic affinity (Naderi, 2013). On the basis of electron microprobe analyses the plagioclases are labradorite-bytownite (Fig.2a) that record both thermal and compositional mixing (Fig.3). On the other hand, the composition of the clinopyroxene is augite (Fig.2b) and its physical and chemical conditions show formation at different depths (Fig.4a) under generally oxygenated conditions with H2O up to 10 wt%,(Fig4.b). The Cpx thermometry yielded temperatures of 550-1110ºC.

4. Tectonic setting

Pyroxene is an important petrogenic indicator in igneous rocks, particularly for deducing the physical and compositional conditions under which they formed. The mineral chemistry of pyroxenes in lavas of the Urumieh-Dokhtar zone suggests an affinity with tholeiitic to calc-alkaline lavas, indicating formation in a VAB and IAB environment (Fig.5 a, b). The whole-rock compositions of the lavas show negative anomalies of HFSE, HREE, P, Ti, Nb and positive anomalies of LREE, Th, Rb, Ba, Sr suggesting that the parent magmas may have been produced in a subduction zone setting (Nderi, 2012) by variable degrees of partial melting of spinel or garnet lherzolite. Trace element abundances reveal that the mantle source was probably metasomatized by slab-derived fluids at an early stage. Then, the enriched mantle wedge partially melted and the resulting magmas were contaminated by continental crust enroute to the surface.

Figures and Tables

Fig. 1. Typical textures in plagioclase, a. Sieve texture, b. poikilitic texture, c. resorbed core in plagioclase

Wo50

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Hedenbergite Diopside 500 Salite Ferosalite

Enid

opsi

de Augite Feroaugite

Subcalcic Augite Subcalcic Feroaugite

Magnesium pigeoniteIntermediate pigeoniteFerriferous pigeonite

Clinoenstatite ferrosillite 0 500 100 En Fs Fig. 2. Mineral compositions a. plagioclase (Deer et al., 1966) , b. pyroxene (Morimoto et al., 1988)

Fig. 3. FeO versus An diagram for determining mixing

Fig. 4. Al-T(IV) versus Al-M(V) diagrams for determination of formation condition of pyroxenes at; a. different pressures (Green, 1972; Helz, 1973), and b. different water contents (Helz, 1973)

0.06 0.04 0.08 a 0.05

0.03 0.06 Alkaline 0.04 MORB CAB

Ti+Cr 0.03 Ti 0.02 Ti 0.04 Subalkaline

Tholeiitic & 0.02 IAT VAB 0.01 0.02 calc-alkaline 0.01

0.00 0.00 0.00 0.0 0.2 0.5 0.7 0.9 1.1 0.5 0.6 0.7 0.8 0.9 1.0 Al Na+Ca Ca Fig. 5 a. Variation of Ca versus Ti+Cr diagram (Leterrier et al.,1982), b. Ti vs. Al diagram (Leterrier et al ., 1982), c. Ti vs. Na+Ca diagram( Leterrier et al ., 1982)

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References

Deer, W. A., Howie, R. A. and Zussman, J. (1966) Rock- forming minerals, 3rd Volume. Sheet silicates. Longman, London.

Green, T. H. (1972) Crystallization of calc – alkaline andesite under controlled high pressure hydrous condition. Contributions to Mineralogy and Petrology 34: 367-385.

Helz, R. T. (1973) Phase relations of basalts in their melting ranges at pH2O = 5 kb as a function of oxygen fugacity, Part I, Mafic phases. Journal of Petrology 14: 249-302.

Leterrie, J., Maury, C.R., Thonon, P., Girard, D. and Marchal, M.(1982) Clinopyroxene composition as a method of identification of the magmatic affinities of paleo-volcanic series. Earth and Planetary Science Letter, 59, 139-154.

Morimoto, N., Fabries, J., Ferguson, A.K., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J.,Aoki, K. and Gottardi, D.(1988) Nomenclature of pyroxenes. American Mineralogist, 62, 53-62.

Naderi, M. (2013) Geochemistry and petrogenesis of igneous rocks in North-Northeast Shirinak village, south– east of Bardsir, (Kerman province). MSc thesis, University of Shahid Bahonar Kerman, Kerman, Iran (in Persian).

Orberger, B., Lonardb, J. P., Girardeau, J., Mercier, J-C.C. and Pitragool S., 1995. Petrogeneis of ultramafic rocks and associated chromitite in the Nan Uttaradit ophiolite, Northern Thailand. Lithos, 35, 100: 255-299.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Tectonic setting of plagiogranites and gabbros in the Shahre-Babak ophiolitic sequence (Nain-Baft belt), Iran

Fatemeh Sepidbar*, Hassan Mirnejad Department of Geology, University of Tehran, Tehran, Iran *Corresponding author’s e-mail address: [email protected]

Abstract Plagiogranite intrusive rocks crop out in the gabbroic section of an ophiolite southeast of Shahre-Babak. Petrographically, the rocks are comprised of tonalite, trondhjemite and leucogabbro. The plagiogranites have inequigranular, hypidiomorphic and granophyric textures, and consist of plagioclase, quartz and sodium feldspars with less than 10% amphibole ± pyroxene and opaques. The gabbros consist primarily of augite, plagioclase and amphibole. Geochemical studies show that the parent magma was sub-alkaline (calc-alkaline series) and metaluminous, typical of volcanic arc granite (VAG) and MORB or I-type granites. Chondrite- normalized REE patterns of the Shahre- Babak plagiogranites and gabbros show weak light REE enrichment with flat HREE sections, consistent with formation in a supra-subduction zone environment. It seems probable that the parental magma of the plagiogranites formed by partial melting of mafic rocks, such as gabbro, in a spreading basin associated with a subduction zone. Keywords: ophiolite of Shahre-Babak, plagiogranite, suprasubduction zone, volcanic arc, partial melting

1. Introduction

Plagiogranites and gabbros are useful in reconstruction of the tectonic history of ophiolites, which indicate the presence of sutures and the closure of ancient oceans and marginal basins (e.g. Savov et al., 2001). Suprasubduction zone ophiolites (cf. Pearce et al., 1984) often contain a geochemical stratigraphy, which consists of island arc tholeiites (IAT) and boninitic volcanic rocks, as well as lavas transitional between IAT and mid-ocean ridge basalts (MORB) (Beccaluva et al., 2005; Dilek et al., 2008; Saccani and Photiades, 2004). These ophiolites in orogenic belts are considered to represent oceanic crust generated in subduction rollback cycles during the closing stages of oceanic basins prior to collision (Dilek and Furnes, 2009). Recent studies reveal that most Tethyan ophiolites display suprasubduction zone chemical characteristics and are mainly of SSZ type (Dilek et al., 2007).

2. Geology

The Shahre-Babak ophiolite complex occupies approximately 400 km2 area and is a part of the ophiolite belt around the CIM, situated in the center of the Nain–Baft ophiolite belt southeast of Shahre-Babak. The ophiolitic complex crops out along the Nain–Baft fault (Fig. 1). Several other relatively dismembered fragments of Neo-Tethyan ophiolite exist along this fault zone on the western

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China side of the CIM, (Shojaat et al., 2003). Other ophiolitic complexes of the Nain–Baft belt include the Nain, Dehshir, Balvard and Robat bodies. The Nain–Baft ophiolitic suture has been interpreted as (i) the remnant of a narrow oceanic basin like the Red Sea, between the Lut block and the active continental margin of the Iranian block known as the Sanandaj–Sirjan Zone (e.g. Berberian and King, 1981); (ii) as a Cretaceous arc basin formed during Tethyan subduction (e.g. Hassanipak and Ghazi, 2000) and (iii) as a Late Cretaceous Nain–Baft back arc basin (Ghazi et al., 2010a).

3. Discussion

The plagiogranites have inequigranular, hypidiomorphic and granophyric textures and consist of plagioclase, quartz, sodium feldspars with less than 10% amphibole ± pyroxene and opaques. The gabbros consist of augite, plagioclase and amphibole. The plagiogranites are particularly, silica-rich ranging from 67 to 76 wt% SiO2. In addition, they have extremely low K2O (0.19-1.45 wt%) and Rb (<4 ppm) contents matching exactly the geochemical characteristics of plagiogranites defined by

Coleman and Peterman (1975). On the SiO2–total alkalis diagram, such as (Winchester and Floyd, 1977), the plagiogranites and gabbros plot in the granodiorite and diorite-gabbro fields, respectively (Fig. 2). On the Ab–An–Or diagram (O’Connor, 1965), plagiogranites fall in the trondhjemite and, partly in the tonalite field (Fig. 3). In terms of the standard chemical classification, such as the SiO2– total alkalis and AFM diagrams, the plagiogranites and gabbros fall within the subalkaline and calc- alkaline fields, respectively. The A/CNK and A/NK ratios for the Shahre-Babak plagiogranite range from 0.77 to 0.91 and from 1.03 to 1.09, respectively. Thus, the plagiogranites plot in the metaluminous field. Because the A/CNK ratios of the plagiogranite are less than 1.1, the samples plot in the field of I-type granites.

4. Petrogenesis

The origin of plagiogranites or low-Al trondhjemites has been attributed to fractional crystallization, partial melting or liquid immiscibility. About 10–35% partial melting of pyroxene– hornblende-bearing gabbroic or basaltic rocks or their metamorphosed equivalents, garnet-free amphibolites or quartz-eclogites, can also give rise to low-Al2O3 felsic melts. In comparison with ocean ridge basalts, the Shahre-Babak plagiogranites and gabbros have relatively high contents of LILE such as Ba and Th, and low HFSE contents with marked negative Nb and Ta anomalies similar to the Troodos ophiolite (Fig. 4b). Chondrite-normalized REE patterns show insignificant LREE/HREE fractionation typical of mid-ocean ridge magmas (Fig.4a). In the Y–Nb discrimination diagram, the plagiogranite samples plot in the VAG and syn-collisional granite field (Fig.5a, b) and in the TiO2-MnO*10-P2O5 and V-Ti*1000 discrimination diagrams, the gabbros plot in the IAT and ARC fields, respectively (Fig.5c, d). In general, these rocks show an affinity with spreading margins related to subduction zones (suprasubduction zone environment). The chondrite-normalized REE patterns of the gabbros are similar to those of the plagiogranites.

5. Conclusions

Plagiogranites crop out in the gabbroic section of the ophiolitic sequence southeast of Shahre- Babak. Petrographically, they are composed of tonalite, trondhjemite and leucogabbro. Mineralogically, they consist of plagioclase, quartz and sodium feldspar, with less than 10% amphibole ± pyroxene and opaques. The gabbros consist of augite, plagioclase and amphibole. Geochemical studies show that they were derived from sub-alkaline (calc-alkaline) and metaluminous-

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

type magmas. The plagiogranites have compositions typical of volcanic arc granite (VAG) and MORB-like, I-type granites. Chondrite-normalized REE patterns of the Shahre-Babak plagiogranites and gabbros show weak light REE enrichment and flat HREE segments. The geochemical characteristics of the plagiogranites suggest that they formed by partial melting of mafic rocks, such as gabbro, in a spreading basin associated with a subduction zone.

Figures and Tables

Azerbaijan 20 An Turkemenistan Caspian syenite Granite Sea 15 Paleo-Tethys suture Nain Af monzonite Quartz IRAN Gabbro -Baft monzonite experimental gh K 2 O/Na 2 O 10 melt compositions fault an Granodiorite Shahre-Ba Main Zagros Thrust 5 Diorite Pe ist TO Gd bak Pa Tonalite rsi an Tdh ki 0 Gr an 50 60 70 80 SiO Ab Or Gulf of Oman st 2 G an ulf Fig. 1 Sketch map of Iran showing Fig. 2 SiO2 vs total alkalis (Winchester Fig. 3 CNK diagram locations of the major ophiolites, Iran and Floyd, 1977) (O'Connor, 1965)

Rock/Chondrites REEs-Sun and McD 89 Rock/MORB Pearce, 1983 1000 a 100 100

10 1

1 .01 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Sr K Rb Ba Th Ta Nb Ce P Zr Hf Sm Ti Y Yb

Fig. 4 a-Chondrite-normalized REE (Sun and Mcdonough) and b-Primary Mantle-normalized spider (left) diagrams for the rocks from the Shahre-Babak ophiolite

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

1000 1000 a b WP Syn-COLG 100 100 WPG G VAG+ Nb 10 Rb Syn-COLG Antaly 10 1 ORG VAG a ORG Oman .1 1 1 10 100 1000 1 10 100 1000 Y Yb+Nb

TiO 2

c d

O M IT OR

B OIA IAT

CAB

MnO*10 P2O5*10

Fig. 5 a, b- Nb vs. Y and Rb vs. Yb/Nb discrimination diagrams (Pearce et al., 1984); c- MnO-TiO2-P2O5 diagram (Mullen, 1986). d-Ti (ppm) versus V (ppm) diagram from Shervais (1982)

References

Beccaluva, L., Coltorti, M., Saccani, E., Siena, F., 2005. Magma generation and crustal accretion as evidenced by supra-subduction ophiolites of the Albanide–Hellenide Subpelagonian zone. The Island Arc 14, 551–563.

Dilek, Y., Furnes, H., Shallo, M., 2008. Geochemistry of the Jurassic Mirdita Ophiolite (Albania) and the MORB to SSZ evolution of a marginal basin oceanic crust. Lithos 100, 174–209.

Dilek, Y., Furnes, H., 2009. Structure and geochemistry of Tethyan ophiolites and their petrogenesis in subduction rollback system. Lithos 113, 1–20.

Dilek, Y., Furnes, H., Shallo, M., 2007. Suprasubduction zone ophiolite formation along the periphery of Mesozoic Gondwana. Gondwana Research 11, 453–475.

Emami, M. H., Sadegi, M. M., Omrani, S. J., 1993. Magmatic map of Iran. Scale 1:100000,Geol. Surv. Iran.

Ghazi, J.M., Moazzen, M., Rahgoshay, M., Shafaii Moghadam, H., 2010a. Mineral chemical composition and geodynamic significance of peridotites from Nain ophiolite, central Iran. Journal of Geodynamics 49, 261– 270.

Hassanipak, A.A., Ghazi, A.M., 2000. Petrochemistry, 40Ar–39Ar ages and tectonics of the Nain Ophiolite, Central Iran. GSA Annual Meeting, pp. 237–238.

Mullen, E. D., 1986. MnO/ TiO2/ P2O5 a minor element discriminatiom for Basaltic rock of oceanic environment and its implication for petrogenesis. Earth pelanet Sci. Lott, 62: 53-62.

O'Connor, J.T., 1965. A classification for quartz-rich igneous rock based upon feldspar ratios. U.S.G.S. Professional Paper 525B, B79–B84.

Pearce, J. A. & Harris,N.B.W. and Tindle, A. G., 1984. Trace element discrimination diagram for the tectonic interpretation of granitic rocks", J.Petrol.,25: 956-983.

Saccani, E., Photiades, A., 2004. Mid-ocean ridge and supra-subduction affinities in the Pindos Massif ophiolites (Greece): implications for magma genesis in a protoforearc setting. Lithos 73, 229–253.

Shand, S. D., 1947. Erptive rockes: their genesis, composition classification and their relation to ore deposites 3" , edition. Jhon Wiley and sons, New York. (1947) 488p.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Shervais,J.W., 1982. Ti-V plots and the petrogenesis of modern and ophiolitic lavas", Earth and planetary science letter ,56:101-118.

Shojaat, B., Hassanipak, A.A., Mobasher, K., Ghazi, A.M., 2003. Petrology, geochemistry and tectonics of the Sabzevar ophiolite. North Central Iran. Journal of Asian Earth Sciences 21, 1053–1067.

Sun, S. S., Mc Donough, W. F., 1989. Chemical and isotopic systematic of oceanic basalts implication for mantle compocition and process", Jn: A.D.Saunders,M.Norry,(eds)Magmatism in ocean Basins.Geological society of London Specical publication ,42 : 313-345.

Winchester, J. A. and Floyd, P.A,. 1977. Geochemical discrimination of different magma series and their Iraq differentation product using immobile element", Chem. Geol., 20: 325-343.

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Late Cretaceous intra-plate volcanism in Ceno-Tethys: evidence from the Kazhaba Volcanics, Balochistan, Pakistan

Rehanul Haq Siddiqui Geoscience Advance research Laboratories, Geological Survey of Pakistan, Shahzad Town,Islamabad, Pakistan Email: [email protected]

Abstract

Basaltic pillow lavas near Kazhaba village in Balochistan occur as tectonic slivers in the Bagh complex, the mélange zone beneath the Muslim Bagh ophiolite complex. These volcanic rocks are mainly alkali basalts, whose petrography and chemistry suggest that they belong to a mildly to strongly alkaline, intra-plate volcanic rock series. Their low Mg # and low Cr, Ni and Co contents suggest that the parent magma was not directly derived from a partially melted mantle source, but resulted from fractionation in a in an upper level magma chamber before eruption. Their LILE and HFSE, and enriched primordial mantle-normalized patterns with marked positive Nb anomalies further confirm their within-plate geochemical signatures and are consistent with an enriched mantle source. Their highly enriched LREE patterns and high (La/Yb)N and (Ce/Yb)N ratios suggest a partially melted garnet-lherzolite parent magma source. A Zr versus Zr/Y plot suggests that these rocks were derived from about 15% partial melting of an enriched mantle source. We suggest that these Late Cretaceous intra-plate volcanic rocks may represent mantle plume activity related to the Reunion hotspot, and that they were erupted during passage of the Ceno- Tethys ocean floor over it. Keywords: Late Cretaceous; Kazhaba volcanics; Balochistan, Pakistan.

Figures and Tables

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 1. A to D. Sketch showing 120-55 Ma journey of Ceno-Tethys ocean floor, Indian continent and the Indian ocean floor (based on the data from Boulin, 1988, 1990; Sengor, 1988; Stocklin, 1989; Brookfield, 1993; Trelaor et al., 1993; Metacalfe, 1995; Zaman and Torii, 1999; Siddiqui et al., 2010). (A) Rifting of India from the northern margin of Gondwana, suturing of Afghan block with Eurasia, (B) Intra-oceanic convergence in Ceno-Tethys and convergence of Ceno-Tethys below the Afghan block, eruption of Kazhaba volcanics during the passage of Ceno-Tethys ocean floor over the Reunion hotspot at 81 Ma, (C) North-western margin of Indian plate over the hotspot and eruption of 71 Ma Bibai volcanic , (D) Indian plate over the hotspot and eruption of 66-68 Ma Deccan Trap. (E) Obduction of Muslim Bagh ophiolite and associated mélange zone having slivers of Ceno- Tethys ocean floor with allocthonous blocks 81 Ma Kazhaba volcanics on to the northwestern margin of the Indian plate during 55 Ma and (F) Collision of northwestern margin of Indian plate and Afghan block in Pliocene (Trelaor et al., 1993). In Figure F, the slivers of Bagh complex having the Kazhaba volcanics are magnified in a circle.

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Volcanogenic massive sulfide Cu-Ag mineralization in the Kharturan area, southeast of Shahrood, Iran

Majid Tashi*, Fardin Mousivand, Habibollah Ghasemi School of Geosciences, Shahrood University of Technology, Iran *Corresponding author’s e-mail address: [email protected]

Abstract Volcanogenic massive sulfide (VMS) mineralization in the Kharturan area, 290 km southeast of Shahrood, Iran, occurs within the Late Cretaceous volcano- sedimentary sequence in the Sabzevar subzone of the Central East Iranian Microcontinent. The Main VMS deposits in the area are the Garmabe Paein and Asbkeshan bodies. The mineralization occurs as stratiform and stratabound orebodies within a specific stratigraphic horizon. The host rocks are andesitic lavas and related volcaniclastic rocks. The orebodies from footwall to hanging wall involve four ore facies: vein-veinlets (stringer), massive, bedded and exhalative sediments (exhalite). Mineralogically, the deposits contain primary pyrite, native copper, chalcopyrite and magnetite, and secondary cuprite, covellite, malachite and Fe-Mn oxides. The textures and structures of the ores include massive, semi-massive, laminated, banded, vein-veinlets, replacement and open space-fillings. Wallrock alterations are dominated by chlorite and argillite. Keywords: Massive sulfide, Cu-Ag, Garmabe Paein , Asbkeshan, Kharturan, Iran

1. Introduction

Volcanogenic massive sulfide (VMS) mineralization in Iran occurs as numerous base (and precious) metal deposits. The VMS deposits are of different types, with various ages, occurring in different structural zones (Mousivand et al., 2008). The Sabzevar zone hosts several VMS deposits including the Nudeh Cu-Ag deposit (Maghfuri et al., 2013) and some deposits in the Kharturan area, 290 km southeast of Shahrood. Copper-silver VMS mineralization in the Kharturan area involves the Garmabe Paein (Tashi et al., 2014) and Asbkeshan deposits and a few small occurrences. The deposits are medium to small in size, were extracted during ancient times, and currently are under detailed exploration. The aim of this article is to present geological, mineralogical, textural, structural and wallrock alteration data on the VMS mineralization in the Kharturan area.

2. Geological setting

The Kharturan area is locate in the Sabzevar subzone of the Central East Iranian Microcontinent (Fig. 1). The Sabzevar subzone contains mainly Mesozoic and Cenozoic rock units, and Late Cretaceous ophiolite mélanges and volcano-sedimentary sequences are extensive. According tp Rossetti et al. (2010), the Cretaceous rocks were formed in a back-arc setting due to subduction of the Neo-Tethyan oceanic lithosphere beneath the Iranian plate (Fig. 2).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Exposed rock units of the Kharturan area from bottom to top are dominated by Early Cretaceous, orbitolina-bearing massive limestone, dacitic-andesitic lava flows and related volcaniclastic rocks٫ chert and radiolarite and Late Cretaceous globotrunkana- bearing limestone, Paleocene polygenic conglomerate consisting of the Cretaceous volcanic clasts and limestone pebbles (equal to the Kerman conglomerate), and a Pliocene weakly-cemented polygenic conglomerate horizon are also present (Fig. 3).

3. Mineralization and wallrock alteration

The Cu-Ag VMS mineralization in the Kharturan area occurs as stratiform and stratabound orebodies within a specific stratigraphic horizon. The host rocks are andesitic lavas and related volcaniclastic rocks. The orebodies from footwall to hanging wall involve four ore facies: 1) vein- veinlets (stringer), 2) massive, 3) bedded and 4) exhalative sediments (exhalite). Mineralogically, the deposits contain primary pyrite, native copper, chalcopyrite and magnetite, and secondary cuprite, covellite, malachite and Fe-Mn oxides. The textures and structures of the ores include massive, semi- massive, laminated, banded, vein-veinlets, replacement and open space-fillings. Major wallrock alteration is to chlorite and argillite.

4. Conclusions

VMS mineralization in the Kharturan area took place within a back-arc setting due to subduction of Neo-Tethyan oceanic lithophere beneath the Iranian continental crust during the late Cretaceous. The mineralization involves a few deposits and occurrences hosted in andesitic lava flows and volcaniclastic rocks within a specific ore horizon in the Late Cretaceous volcano-sedimentary sequence. The orebodies involve four distinct facies which from the bottom upward include vein- veinlets (stringer), massive, bedded and exhalative sediments (exhalite). Mineralogically, the deposits contain primary pyrite, native copper, chalcopyrite and magnetite, and secondary cuprite, covellite, malachite and Fe-Mn oxides. Textures and structures of the ores include massive, semi-massive, laminated, banded, vein-veinlets, replacement and open space-fillings. Major wallrock alteration mainly produce chlorite and argillite.

Figures and Tables

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 1 a) Different pieces of the Tethys Ocean convergence zone along the Alps - Himalaya and the tectonic map (tectonic domains) of Iran, and location of the Sabzevar subzone, b) general expansion of the Sabzevar zone (Lindenberg et al. 1983) and location of the main VMS deposits in the, including the Nudeh and Garmabe Paein eposits. CEIM:Central East Iran Microcontinent

Fig. 2 Schematic drawing of subduction of the Neo-Tethyan oceanic crust beneath the Central Iran plate in the Late Cretaceous (Late Cretaceous), and formation of a back-arc basin wich includes the Sabzevar subzone (Rossetti et al., 2010).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 3 Geological map of the Kharturan area (modified after Kohansal, 2007) indicating locations of the Garmabe Paein and Asbkeshan VMS deposits.

References

Kohansal. (2007), Geological map (scale 1:1000000) of Mary and Asbkeshan, Geological Survey of Iran.

Lindenberg, H.G., Gorler, K. Ibbeken. H., 1983, Stratigraphy, structure and organetic evolution of the Sabzevar zone the area of Oryan Khorasan, NE, Iran GSI, Rep. No. 51, p: 120-142.

Tashi. M., Musivand. F. Ghasemi. H., (2014) Occurrence of Garmabe Paein copper volcanogenic massive sulfide deposit in The Kharturan area, southeast of Shahrood. 32nd Conference of Geosciences, Geological Survey of Iran.

Mghfuri, S. Rastad, b. Mousivand, F., (2011) a massiv of copper sulfide ore-bearing facies (a) Nodeh, SW, Sabzevar Tarbiat Moallem University, Tehran, Iran Geological Society.

Mousivand, F., Rastad, E., Hoshino, K. & Watanabe, M., (2007) The Bavanat Cu-Zn-Ag orebody: First recognition of a Besshi-type VMS deposit in Iran: Neues Jahrbuch Fur Mineralogie-Abhandlungen, 183, 297-315.

Rosseti. F., Nasrabady. M. Vignaroli. G. Theye. T. Gerdes. A. Razavi. M. and Moin Vaziri. H., (2010) Early Cretaceous migmatitic mafic granulites from the Sabzevar range (NE Iran): implications for the closure of the Mesozoic peri- Tethyan oceans in central Iran” Terra Nova, v 22, pp 26- 34.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Landslide susceptibility assessment of Yom River Basin, Phrae Province, Northern Thailand

Suree Teerarungsigul Ministry of Natural Resources, Thailand Corresponding author’s e-mail address: [email protected]

Abstract A landslide susceptibility assessment was conducted for the Yom River catchment, North Thailand. A map was produced, which groups the basin into different areas of susceptibility regarding landslides. An integrated approach was tested that allows more detailed treatment of combined factors, which are inherently responsible for the occurrence of landslide events. All working steps and decision rules used for the analysis are based on robust statistical threshold criteria. The final susceptibility map describes the spatial hazard after applying a quantitative classification. The main landslide-controlling factors, chiefly based on remotely sensed data, were considered. The final map provides a suitable and reliable starting point for further detailed mass movement analysis in the Yom River Basin. This region was hit by a disastrous landslide on May 4, 2001. The map can further be used to support strategic spatial planning measures at a regional scale and to identify priority areas for more detailed investigations at larger scales. Keywords: Statistical Evaluation, Weight of Evidence, Bayesian statistics, Landslide susceptibility

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Depositional environment of the Tertiary Krabi Basin of Southern Thailand using coal petrography

Bantita Terakulsatit School of Geotechnology, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand Corresponding author’s e-mail address: [email protected]

Abstract The Bang Mark coal deposit is situated at the Krabi mine in the Tertiary Krabi basin, Southern Thailand. The coal, which is low rank (ranges from lignite to sub-bituminous), is about 7 to 20 m thickness. The purpose of this paper is to provide a comprehensive description of the composition, character and depositional environment of the coal seams in the Bang Mark deposit in the Krabi Basin using coal petrography. The lower coal seam is completely dominated by a huminite group (between 50 to 70 percent), accompanied by 20 to 45 percent liptinite and a small amount of inertinite, ranging from 0 to 5 percent. In the upper coal seam, the huminite content ranges from 50 to 60 percent, the liptinite group from 30 to 40 percent and the inertinite from 0 to 3 percent. The huminite group (humotelinite and humodetrinite) indicates a generally oxygen-deficient paralic coal deposit. The liptinite group (sporinite, cutinite, resinite, fluorinite, suberinite, alginite, liptodetrinite and exsudatinite) indicates a forest-swamp or lake environment. Those deposits containing alginate probably formed in stagnant water. Sclerotinite only occurs in the inertinite group, indicating the rare occurrence of wildfires during coal accumulation. The alginite in both coal seams is dominated by Botryococcus sp. (alginite A) of Pila and Reinschia types, which is associated with green algae in swampy depositional environments. Variation in Reinschia, Pila algae could indicate changes of water quality. Sporinites mainly occur in coal seams associated with a forest swamp environment, and these are embedded in a groundmass of liptodetrinite, coal and clay matrices. Megaspores mainly occur in the upper coal seam, and microspores occur in both lower and upper seams. Nypa-type pollen and palm leaves (Sabilistis sp.) have also been found in the lower coal seam, which are the indicators of a tropical,mangrove-plant environment. The cutinite is dominantly in this seam, where it is associated with needle-like fragments of Pinus sp., indicating an association with temperate plants and probably higher-elevation plant assemblages. The cutinite and alginite association in the both coal seams is an indication of intermediate to shallow water depth. The suberinite is represented in both lower and upper coal seams, indicating the common occurrence of large tree trunks in a forest swamp environment In conclusion, the lower Bang Mark coal seam represents a fluctuating environment, dominated by fresh water, but also influenced by slightly saline water. The coals show very high destruction of

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China plant material before coal formation indicating a high water content in the deposits. The environment may have been a large salt marsh or coastal swamp beyond the intertidal mud flat. The water level was gradually increasing and then became stable in the upper portion of the lower coal seam, indicated by the high content of alginite. The upper part of the coal seam was dominated by fresh water with a stable water level and the upward dryness in the upper portion of this seam indicates an increase in terrestrial plants (suberinite). It also indicates a balance between coal accumulation and accommodation space. Keywords: Krabi basin, Coal Petrography, Macerals, Liptinite, Thailand

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Petroleum potential assessment in northeastern Thailand using computer programs

Kriangkrai Trisarn* and Akkhapun Wannakomol School of Geotechnology, Institute of Engineering, Suranaree University of Technology 111 University Revenue, Nakorn Ratchasima 30000, Thailand. *Corresponding author’s e-mail address: kriangkr@ sut.ac.th

Abstract We carried out a petroleum assessment of the Northeastern region of Thailand based on geological data that have a direct influence on the generation of petroleum, reservoir rocks, seal rocks and geological structures. Play types and traps were classified according to their geological setting and relationship to geological structures. In the Northeastern region, 3 play types can be identified; pre-Permian, Permian and Triassic. The major known gas fields of Nam Phong, Phu Horm, Chonnabot, Dong Mun and Phu Khieo are located in the Permian play type. The petroleum resources in the Northeastern region were evaluated by utilizing the FASPU (Fast Appraisal System for Petroleum Universal) program. The petroleum geology factor is the main variable for the petroleum system evaluation for play attributes, prospect attributes and hydrocarbon volume attributes. The petroleum engineering factor is used for petroleum resource calculations. The petroleum resource evaluation in the Northeastern region was compiled and calculated using well data obtained from 17 prospects of the Permian III play type. The results show that gas accumulation at a high level of confidence is 6.60 TCF and at a low level of confidence is 310.4 TCF. The objective of the research was to study the Northeastern petroleum potential of the One field, Namphong field and Permian formation using the FASPU computer program. The study and analysis were divided into 3 sections. First was the software development for petroleum potential and risk assessment under various geological conditions and petroleum engineering requirements, including Monte Carlo Simulation, Swanson‘s Mean and Probability of Success. In addition, a theory of petroleum economics was applied to the software development for considering the internal rate of return and profit to investment ratio. The software was developed using Microsoft Visual Basic Version 6.0, which is here called MSP (Monte Carlo Simulation, Swanson‘s Mean และ Probability of Success). Secondly, the gas in place for the One field,, Namphong field, and Permian formation, was compared using FASPU, GeoX (GeoKnowledge) and MSP. The gas in place for One field is 122-234, 403-622 and 833-1,808 Bcf for P90, P50 and P10, respectivel, the gas in place for the Namphong field is 420-456, 819-1,264 and 2,084-2,851 Bcf for P90, P50 and P10, respectively and finally the gas in place for the Permian formation is 6,498-14,831, 40,645-70,564 and 252,860-307,507 Bcf for P90, P50 and P10 respectively. The third activity involved comparing petroleum economic benefits in terms of internal rate of return and profit to investment ratio, using gas in place for P50 of MSP only.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

As an example, the, profit to investment ratio and internal rate of return for 470 Bcf in One field are 3.40-3.77 and 28.41-40.19% respectively; profit to investment ratio and internal rate of return for 1,154 Bcf of the Namphong field are 5.75 and 37.94% respectively; and profit to investment ratio and internal rate of return for 46,198 Bcf of the Permian formation are 4.91 and 36.90% respectively. Fifty prospects of various sizes were randomly economic simulated using the Monte Carlo technique to find NPV (Net Present Value) and EMV (Expected Monetary Value P50). The probability to earn 200-500 MM$ is 12% and Expected Monetary Value (P50 or the cumulative probability of 50%) is 200 MM$. The results of this study can be applied to the northeastern regopm or any other petroleum potential and risk assessment, using various geological conditions, petroleum engineering requirements and computer software (such as FASPU, GeoX and MSP) and should promote petroleum exploration investments in Thailand.

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Inorganic carbon isotopic anomalies across the Ordovician--Silurian boundary on the Yangtze Platform, South China: an environmental event interpretation

Shen Tu1, Zhou Wang1, Jiasheng Wang1,2* 1. Faculty of Earth Sciences, China University of Geosciences, Wuhan, China 2. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan *Corresponding author’s e-mail address: [email protected]

Abstract Strata crossing the Ordovician-Silurian boundary in the Guanyinqiao, Chongqing and Huanghuachang sections, in Hubei Province record the end-Ordovician glaciations (Hirnantian) that are correlated with mass extinctions and associated environmental changes. These sections were sampled for high-resolution inorganic carbon and oxygen isotope analysis. Compilation of the new 13 13 δ Ccarb curves with other sections in South China shows different magnitudes of negative δ Ccarb excursions in the Upper Ordovician Kuanyinchiao Bed, which contradicts the global positive Hirnantian Isotopic Curve Excursion event (HICE). This inorganic carbon anomaly in South China indicates the injection of a massive extra light carbon (12C) component into the dissolved inorganic carbon reservoir (DIC) of the Yangtze Sea at the time of the Hirnantian glaciations, owing to aerobic and/or anaerobic oxidation of methane (AOM) and organic matter during the glacio-eustatic sea-level drop in South China. Keywords: end-Ordovician glaciation; carbon and oxygen isotope; the Kuanyinchiao Bed; anomaly; DIC

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Geochemical analysis of chert for interpretation of depositional environment in the Saraburi region, Thailand

Hathaichanok Vattanasak1*, Chongpan Chonglakmani1, Qinglai Feng2 1. Vattanasak School of Geotechnology, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand 2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China *Corresponding author’s e-mail address: [email protected]

Abstract The Saraburi Group in the Saraburi-Pak Chong area can be sub-divided into 8 lithofacies representing shelf or platform, basin margin and deep basin environments. Lithofacies of shallow marine environments include thin-to-thick bedded limestone and dolomite, boundstone and dolomite, and sandstone, shale and limestone. Basin margin and deep basin environments are represented by crinoidal limestone, micritic limestone, limestone conglomerate, allodapic limestone, shale and cherts (Chonglakmani, 2001, 2005). We used major, trace and rare earth elements data to investigate the depositional environment of a chert sequence in the Muak Lek district, Saraburi Province, Thailand. The studied section belongs to the Saraburi Group and comprises shale, thin-bedded cherts and limestone of deep marine facies. The cherts are brown to dark grey and yield moderate and poorly preserved radiolarians. The radiolarian fauna shows that the cherts accumulated in the Middle Permian to early Late Permian. The geochemical analysis of cherts and study of sedimentary facies are incorporated to explain the depositional environment of this sequence. The results of major and trace elements analysis of cherts indicate high ratios of SiO2/SiO2+Al2O3+Fe2O3. Al/(Al+Fe+Mn) ratios are from 0.67 to 0.82

(Adachi et al., 1986) and MnO/TiO2 are 0.14 on average (Murray, 1994). Al2O3/(Al2O3+Fe2O3) ratios of chert samples are 0.60 to 0.82 (0.76 on average) (Sugitani et al., 1996). The MnO/TiO2 and

Al2O3/(Al2O3+Fe2O3) ratios and the 100×Fe2O3/SiO2 vs. 100×Al2O3/SiO2 and the Fe2O3/(100-SiO2) vs.

Al2O3/(100-SiO2) diagrams suggest that the cherts were deposited in a continental margin setting. All samples plotted in the Al-Fe-Mn diagram lie close to the non-hydrothermal field (Adachi et al., 1986 and Yamamoto, 1987). The Lan/Cen vs. Al2O3/(Al2O3+Fe2O3) discrimination diagram shows that the majority of the chert samples are related to pelagic and continental margin settings. NASC- normalized REE patterns are very flat with Ce/Ce* ratios ranging from 0.18 to 0.61, indicating that these cherts may have formed in a pelagic basin, perhaps relatively near to a continental margin (Feng et al., 2002: Chen et al., 2006 and Udchachon et al.,2011). The studied section can be interpreted to represent the deposition in a deep marine basin. This facies can be correlated with the Nong Pong and the Nam Duk Formations of the Saraburi Group in northeastern Thailand. From the results of the geochemical analysis, cherts of the Saraburi region

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China and the Nan Suture Zone are related to the continental margin settings. In the Nan area, the sequence of chert is associated with oceanic island basalt which represents a small ocean with oceanic islands close to a continental margin (Yang et al., 2008). However, the chert sequence of the studied area was deposited in a deep basin on continental crust in a continental margin setting. Keywords: Depositional Environment, Chert, Nong Pong Formation, Geochemical analysis

Acknowledgement

NSFC (project No. 41172202), China Geological Survey Program (No. 1212011121256)

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Superimposed and simple pop-up structures in fold-and-thrust belts and their implications: Insights from sandbox models of thrust wedges

Yuanbo Wan, Bin Deng*, Zhiwu Li, Shugen Liu, Gaoping Zhao, Tong Lin State key Laboratory of Oil and Gas Reservior Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China *Corresponding author’s e-mail address: [email protected]

Abstract Pop-up structures are widely developed in fold-and-thrust belts and strike-slip tectonic settings (e.g., Sylvester, 1988; Harding, 1990; Rrichard et al., 1995; Dooley and McClay, 1996; McClay and Whitehouse, 2004), and have been of great significance in petroleum exploration. Analogue sandbox modeling has proved to be a powerful visual tool for simulating such complex structures in various tectonic settings (e.g., McClay and Whitehouse, 2004). We conducted a series of sandbox modeling to unravel the differences in structural geometry of pop-up structures during the development of fold- and-thrust belts, based on the same initial conditions with various shortening velocities (0.3mm/s, 0.1mm/s, 0.05mm/s, 0.005mm/s). From our modeling results, two types of pop-up structures, i.e. superimposed and simple pop-up structures, can be developed in thrust wedges depending on different shortening velocities. In general, the geometric pattern of pop-up structures consists of paired thrust and retro-thrust, with their ramp angle showing a inverse relationship with increasing shortening velocity before reaching a steady-state eventually, at which ramp angles are 30° - 41° for thrusts and 48° - 65° for retro-thrusts. In particular, there are significant differences between superimposed and simple pop-up structures. The angle between thrust and retro-thrust (βs) in superimposed pop-up structures is mainly within 100° - 108°, and larger than that of simple pop-up structure (βn) between 80° ~ 100° (Table 1). Although displacements of the thrust and retro-thrust in both types of pop-up structures are similar (30-73.7 mm and 5.2-30.2 mm respectively), there are more faults developed in superimposed pop-up structures. Thus, the superimposed pop-ups show much wider geometry, with low height/width ratios and more complicated internal deformation (Figure.1). Furthermore, the shortening velocity shows an intimate correlation with the structural geometry of the thrust wedge. At a high velocity (e.g., 0.3mm/s), the wedge typically shows a simple deformation style characterized by simple pop-up structures and increasing deformation propagating continuously towards the foreland. However, it is characterized by superimposed pop-up structures with an asymmetrical axial plane (Figure 1, dipping toward the hinterland) and more stronger deformation localized within the back limb of the pop-up structure at a low velocity (e.g., 0.005mm/s). It should be noted that the growth of superimposed pop-up structures has significant control on the evolution of fold-and-thrust belts and their petroleum accumulation. With the development of new

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China retrothrust faults, pre-existing thrusts are cut and moved backward, resulting in a superimposed pop- up structure characterized by an asymmetrical axial plane (Figure 1, toward the foreland). The deformation further controls the fault entrapment and spill points of plays located in the fold-and- thrust belt. Keywords: sandbox modeling, pop-up structure, superimposed pop-up, simple pop-up.

Figures and Tables

Table 1 Summary of experimental parameters and results of experiment series with different velocity V V V V No. of models 1 2 3 4 0.3mm/s 0.1mm/s 0.05mm/s 0.005mm/s θ1 30.4° 33 35.1 35 θr1-1 -53° -66° -50° -61.5°

θr1-2 -54° -51° -51° -45°

β1 96.5° 96° 94.9° 100°

S1（mm） 43.4 42.7 47.1 73.7 T1

Sr1-1（mm） 22.2 11.9 24.3 15.2

Sr1-2（mm） 15.6 44.2 11.1 30.2

θ2 35.2° 35.4° 39.7° 34.9° θr2-1 -37° -66° -46° -50° θr2-2 -55° -61° -43.3° -50.6° β2 89.8° 95.6° 94.3° 95.1° T2 βS - 100° - -

S2（mm） 34.1 70 27.1 45.5

Sr2-1（mm） 18.5 5.5 23.5 10.9

Sr2-2（mm） 9.1 11.1 28.2 11.7

θ3 38.3° 44.4° 37.8° 30 θr3-1 -53° -60° -58° -50.2° θr3-2 -49° - -44° -45.2° β3 92.7° 75.6° 98.2° 99.8° β 105° - 100° 108° T3 S S3（mm） 64.9 18.7 76.1 17.8

Sr3-1（mm） 19.1 7.3 7.8 24.8

Sr3-2（mm） 17.6 - 11.6 13.4

θ4 39.1° 31.1° 41° - θr4-1 -60° -50° -60.5° - θr4-2 -62° -44° -65° - β4 80.9° 98.8° 78.5° - β - 95° - - T4 S S4（mm） 31.6 54.6 30.2 -

Sr4-1（mm） 7.7 9.3 8.1 -

Sr4-2（mm） 8.2 18.8 5.2 - （Tn=Thrust, θn=Thrust ramp angle, θrn=Retrotrust ramp angle,βn=The angle of simple pop-up faults, βs=The angle of superimposed pop-up faults, Dn=Thrust displacement, Drn=Retrothrust displacement.)

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Fig. 1 Single and superimposed pop-up structures in Fold-and-thrust belt and their evolution A)extrusion rate V=0.3mm/s,a,b,respectively shortening R= R = 76%, 89.6% of the pop-up structure(As the symmetry axis,T1,T2,T3,T4 represent thrust fault, Tr1, Tr2, Tr3, Tr4 respectively retreothrust fault),c,respectively interpretation model to b;B)V=0.005mm/s,a,b,shortening R=74.8%, 89.6%.

Acknowledgments

This work was supported by the National Basic Research Program of China (No. 2012CB214805), the Natural Science Foundation of China (Nos. 41402119, 2014JQ0057, 41472017).

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

Using apatite as a tracer for the origin of carbonatite: a case study of the Kaiserstuhl complex, south Germany

Lianxun Wang1,2*, Michael A.W. Marks1, Changqian Ma2, Gregor Markl1 1. Department of Geoscience, Mathematics-Natural Science Faculty, University of Tuebingen, 72074 Tuebingen, Germany 2. Faculty of Earth Science, China University of Geosciences, 430074 Wuhan, China *Corresponding author’s e-mail address: [email protected]

Abstract Apatite from carbonatites of the Kaiserstuhl complex contains lower Cl, Br, S, Fe, Mn, Th, U and Si contents but higher Sr and Nb contents than apatite from associated alkaline silicate rocks. Apatite from a bergalite sample (carbonate-bearing melilititic dyke rock) and a diatreme breccia (containing both carbonatitic and silicate fragments) shows systematic core-rim and replaced zonations, respectively. The core zone of apatite from the bergalite and the relic part of the apatite from the diatreme breccias have compositions similar to those of apatite from silicate rocks in terms of Cl, S, Sr and Si contents. In contrast, the rim zones of apatite from the bergalite and the replaced part of apatite from the diatreme breccias are similar to the composition of apatite from carbonatites. These observations imply that a genetic link exists between the alkaline rocks and associated carbonatites in the Kaiserstuhl complex as recorded by the respective apatite compositions. Keywords: Apatite, Carbonatite, Silicate alkaline rocks, Kaiserstuhl, Zoning texture

1. Introduction

Despite nearly a century of research on carbonatites, their origin and relationships to associated silicate rocks is not yet completely understood (e.g., Bell et al., 1999; Gittins and Harmer, 2003). Experimental work has shown that carbonatites can be generated by; (1) liquid immiscibility of carbonatite and silicate melts; (2) partial melting of carbonate-bearing mantle peridotite; and (3) fractional crystallization of carbonate-rich alkaline silicate magma. Of the approximately 500 carbonatite occurrences worldwide, more than 75% are associated with alkaline silicate rocks, ultramafic lamprophyres and kimberlites (e.g. Woolley and Kjarsgaard, 2008). In some localities, unusual transitional rocks (e.g., carbonate-rich/bearing silicate rocks), such as bergalites, turjaites and okaites, are also found temporally and spatially close to the carbonatite and associated silicate rocks (e.g., Eby, 1975). Apatite is a common accessory mineral in all these rocks and can reach appreciable amounts in some carbonatites (e.g., Bühn et al., 2001). Therefore, a comprehensively investigation of apatite from carbonatites, associated alkaline rocks and the transitional dyke rocks may provide important clues for the petrogenetic link between carbonatites and associated silicate rocks. The Kaiserstuhl Volcanic Complex (KVC) comprises a series of alkaline silicate rocks, associated with carbonatites as well as transitional dyke rocks (bergalites) and polygenic diatreme breccias (mixtures of carbonatite and silicate-rock fragments). Hence, in the present work we studied apatites from various rocks of the KVC with the aim to; (1) constrain the chemical variations of these

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China apatites, and (2) shed more light on the petrogenetic relationship between carbonatite and associated silicate rocks.

2. Geological setting

The KVC is located in the southern part of the Upper Rhine Graben and is part of extensive Cenozoic volcanism in Central Europe. Formation of the graben and its related magmatism are a result of the Alpine Orogeny with northward subduction (e.g., Keller et al., 1990). Ages of the Kaiserstuhl rocks range between 18 and 13 Ma. The KVC is a sequence of early intrusive and extrusive alkaline silicate rocks followed by late formation of carbonatites. The silicate rocks are dominated by tephrites, essexites and phonolites. Sub-dominant rock types include olivine-melilitites, olivine-nephelinites, limburgites (olivine + augite + glassy groundmass), hauynophyres, syenites, shonkinite porphyries, and mondhaldeites. Shonkinite porphyry and mondhaldeite are fractionated dyke rocks from tephritic magmas. The carbonatites consist of sövite intrusions (Badberg and Orberg), alvikitic dykes and rare extrusive carbonatites. These are spatially and temporally associated with; (1) magmatic diatreme breccias, some of which are polygenic mixtures consisting of mafic cumulates, carbonatite and silicate rock fragments that fill pipe structures in the sövite bodies; and (2) bergalite dyke rocks, which are carbonate-bearing and silica-undersaturated rocks with a mineral assemblage of melilite + sodalite + perovskite + biotite ± nepheline + apatite + magnetite + calcite. In this study we investigated apatite separates from twelve KVC rocks, including four sövitic carbonatites from surface outcrops and drill cores, one diatreme breccia, one bergalite, and six alkaline silicate rocks (one essexite, one mondhaldeite, one shonkinitic porphyry, and three phonolitic rocks).

3. Results and Discussions

Compositional analysis shows that the Cl and Br concentrations in apatites from carbonatitic rocks (C.Ap) are always lower than those from alkaline silicate rocks (S.Ap), whereas the F values largely overlap. This agrees well with previous studies showing that apatites from carbonatite complexes are Cl-poor, with mostly less than 0.1 wt% Cl (e.g., Seifert et al., 2000; Patiño Douce et al., 2011). The Cl depletion has been explained by Cl partitioning into an aqueous fluid phase, which generally coexisted with the carbonatitic melt (Gittins, 1989; Seifert et al., 2000). The consistent behavior of Cl and Br in all apatites is also consistent with previously reported positive correlations between Cl and Br (O’Reilly and Griffin, 2000; Marks et al., 2012), implying Cl and Br behave in a similar fashion when incorporated in apatite. In addition to the halogens, S, Fe, Mn, Th, U and Si contents in C.Ap are generally lower than those in S.Ap, whereas Sr and Nb contents are higher in C.Ap. These chemical variations are mainly controlled by apatite-melt partitioning coefficients, melt composition, and the substitution mechanisms of apatite (e.g., Sha and Chappell, 1999). For instance, the partitioning coefficient D apatite-melt value of Nb in apatite-carbonatitic melt systems is higher than that in apatite-silicate melt systems, resulting in the relatively higher Nb contents in C.Ap. However, the higher Sr contents in C.Ap are most likely buffered by the melt composition, since carbonatitic melts are usually much richer in Sr than silicate melts (e.g., Keller et al., 1990). In addition, positive correlations between S and Si and between La+Ce and Si for C.Ap and S.Ap imply that the substitutions of Si4+ + S6+ = 2P5+ and REE3+ + Si4+ = Ca2+ + P5+ play dominant roles in the variation of S and Si contents in C.Ap and S.Ap. Apatites from the bergalite show a systematic and discontinuous core-rim zonation under cathodoluminescence (CL), with the core being compositionally similar to S.Ap and the rim corresponding to C.Ap (Fig. 1). This observation probably reflects the evolution of the magma

100

International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China composition during cooling and crystallization of bergalite. The overgrowth of C.Ap-like rims on S.Ap-like cores implies that the bergalite apatites nucleated in a silicate melt and continued to crystallize from an evolving CO2-enriched melt probably with carbonatitic affinity. The origin of carbonatitic melt could be principally explained by prolonged fractional crystallization of a melilite nephelinitic magma, which has been successfully duplicated in early experimental studies (Watkinson and Wyllie, 1971). The coherence of Cl contents in the rim zone of apatites from bergalite and C.Ap indicate that Cl is a good tracer for magma evolution. Apatites from the diatreme breccia comprise three populations (Fig. 1); (1) similar to S.Ap; (2) similar to C.Ap; and (3) resembling apatite population (1) partially replaced by apatite (2). These observations are consistent with the mixing components of this sample which contains both silicate and carbonatitic fragments. The replacement texture found in the apatites probably represents a late- stage fluid/melt re-equilibration product caused by metasomatism of late-injected carbonatitic melt on early crystallized apatites from silicate rock fragments. Overall, we conclude that apatite (1) is derived from silicate rock fragments and apatite (2) is crystallized from a later intruding carbonatitic melt, which metasomatized the silicate rock fragments and caused the replacement textures as observed in apatite population (3).

Figures and Tables

Fig. 1. Chemical variations (selective elements) of the investigated apatites from the Kaiserstuhl complex, south Germany.

Acknowledgements

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International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China

This study was financially supported by National Nature Science Foundation of China (Grants 41272079).

References

Bell, K., Simonetti, A., 1996, Carbonatite magmatism and plume activity: implications from the Nd, Pb and Sr isotope systematics of Oldoinyo Lengai. Journal of Petrology, v. 37(6), 1321-1339.

Bühn, B., Wall, F., Le Bas, M.J., 2001, Rare-earth element systematic of carbonatitic fluorapatites, and their significance for carbonatite magma evolution. Contributions to Mineralogy and Petrology, v. 141, 572-591.

Eby, G.N., 1975, Abundance and distribution of the rare-earth elements and yttrium in the rocks and minerals of the Oka carbonatite complex. Geochimica et Cosmochimica Acta, v. 39, 597-620.

Gittins, J., Harmer, R.E., 2003, Myth and reality in the carbonatite–silicate rock “association”. Period Mineralogy, v. 72, 19-26.

Marks, A.W.M., Wenzel, T., Whitehouse, M.J., Loose, M., Zack, T., Barth, M., Worgard, L., Krasz, V., Eby, G.N., Stosnach, H., Markl, G., 2012, The volatile inventory (F, Cl, Br, S, C) of magmatic apatite: an integrated analytical approach. Chemical Geology, v. 291, 241-255.

O’Reilly, S.Y., Griffin, W.L., 2000, Apatite in the mantle: implications for metasomatic processes and high heat production in Phanerozoic mantle. Lithos, v. 53(3), 217-232.

Patiño Douce, A.E., Roden, M.F., Chaumba, J., Fleisher, C., Yogodzinski, G., 2011, Compositional variability of terrestrial mantle apatites, thermodynamic modeling of apatite volatile contents, and the halogen and water budgets of planetary mantles. Chemical Geology, v. 288, 14-31.

Seifert, W., Kämpf, H., Wasternack, J., 2000, Compositional variation in apatite, phlogopite and other accessory minerals of the ultramafic Delitzsch complex, Germany: implication for cooling history of carbonatites. Lithos, v. 53, 81-100.

Sha, L.K., Chappell, B.W., 1999, Apatite chemical composition, determined by electron microprobe and laser- ablation inductively coupled plasma mass spectrometry, as a probe into granite petrogenesis. Geochimica et Cosmochima Acta, v. 63, 3861-3881.

Watkinson, D.H., Wyllie, P.J., 1971, Experimental study of the composition join NaAlSiO4-CaCO3-H2O and the genesis of alkali rock-carbonatite complexes. Journal of Petrology, v. 12, 357-378.

Woolley, A.R., Kjarsgaard, B.A., 2008, Paragenetic types of carbonatites as indicated by the diversity and relative abundances of associated silicate rocks: Evidence from a global database. Canadian Mineralogist, v. 46, 741-752.

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Halogen (F, Cl and Br) variations in alkaline rocks from the Upper Rhine Graben, SW Germany

Lianxun Wang1,2*, Michael A.W. Marks1, Changqian Ma2, Gregor Markl1 1. Department of Geoscience, Mathematics-Natural Science Faculty, University of Tuebingen, 72074,Tuebingen, Germany 2. Faculty of Earth Science, China University of Geosciences, 430074 Wuhan, China *Corresponding author’s e-mail address: [email protected]

Abstract We present halogen compositions in a series of alkaline rocks from the Kaiserstuhl, Hegau and Urach areas of the Upper Rhine graben region (South Germany). Most primitive rocks (olivine melilitites and olivine nephelinites) have lower Cl and Br concentrations (generally below 100 µg/g and below 0.3 µg/g, respectively) compared to more evolved tephrites, phonolites and related rocks (up to 7600 µg/g Cl and 34 µg/g Br). However, the Cl/Br ratios of the majority of the investigated samples are relatively uniform (371 ± 120), regardless of rock type and sample locality, suggesting that partial melting, fractional crystallization, and degassing have limited effects on the fractionation of Cl from Br. The mean value of the Cl/Br ratio is similar to previous estimates for basaltic rocks with MORB and OIB mantle signatures. Fluorine concentrations of the primitive rocks show limited variations (900-1100 µg/g) and are within the range defined by the evolved rocks (400-2100 µg/g), but are much higher than previous estimates for the MORB and OIB mantle (50-135 µg/g). This may indicate a relatively F-rich mantle source beneath the Rhine Graben region. In contrast to Cl/Br ratios, the F/Cl ratios vary significantly over three orders of magnitudes (from <0.1 to around 100) and decrease from primitive rocks to more evolved ones, implying that magmatic processes such as fractional crystallization and degassing strongly effect this ratio. Keywords: Halogens; Alkaline rocks; Upper Rhine Graben; Magmatic processes; Cl/Br ratio; Degassing

1. Introduction

In addition to water, carbon dioxide, sulphur and halogens (F, Cl and Br) are important volatile components in magmatic systems. They play essential roles in melting of the mantle, degassing of eruptive volcanoes and in transporting and depositing metals during hydrothermal processes (e.g., Pyle and Mather, 2009). Our current understanding of how halogens are distributed between the Earth’s geochemical reservoirs and how they are mobilized during magmatic processes is limited (e.g., Aiuppa, 2009; Pyle and Mather, 2009). Estimates of halogen abundances in the primitive mantle imply low concentrations (F = 18-28 µg/g, Cl = 1-38 µg/g, Br = 0.004-0.5 µg/g; Pyle and Marther 2009). Similarly, studies on mid-ocean ridge basalts (MORB) imply that the MORB-mantle is relatively depleted in halogens (F =

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50-135 µg/g; Cl = 1-21 µg/g; e.g., Saal et al., 2002). Detailed studies on MORB and ocean island basalts (OIB), however, generally show relatively high and variable halogen concentrations, partially attributed to the assimilation of seawater (e.g., Kenderick et al., 2013). Halogen abundance ratios (F/Cl, Cl/Br) in magmatic systems are considered to be indicators of their origin and evolution (e.g., Jambon et al., 1995; Kendrick et al., 2012). Recent studies show that Cl/Br ratios of pristine MORB and OIB samples show only limited variations, implying relatively similar geochemical behavior for Cl and Br during magmatic processes, such as partial melting, fractional crystallization and degassing (average of 360±112; Jambon et al., 1995; Kendrick et al., 2012). However, much less is known about halogen systematics in rift-related alkaline magmatic systems (e.g., Köhler et al., 2009; Mangler et al., 2014). A detailed investigation of the halogen systematics of such rock series may help to constrain halogen signatures in the sub-continental mantle. For example, rift-related alkaline silicate rocks from Greenland and Oldoinyo Lengai (Tanzania) reveal high F contents (up to 1.2 wt %) and variable Cl contents (70-5000 µg/g) and are partially interpreted to reflect mantle halogen abundances (Mangler et al., 2014; Köhler et al., 2009). In this contribution, we report F, Cl and Br abundance data for a suite of alkaline rocks from the Upper Rhine Graben area of southwest Germany, which is a part of the Cenozoic rift system in western and central Europe. The main goals of this work are; (1) to investigate the variation of halogen contents and ratios in alkaline rocks; (2) to understand the influences of magmatic differentiation and degassing on halogen variations; and (3) to constrain halogen signatures for the sub-continental mantle beneath Central Europe.

2. Geological settings and sample descriptions

The Upper Rhine Graben (URG). located in southwest Germany. is one of the largest branches of the Cenozoic rift system in western and central Europe (Wilson and Downes, 2006). Along the graben and in close proximity, Tertiary/Cenozoic volcanic centers, dykes, pipes, necks and diatremes are widespread (Keller et al., 1990). The dominant rock types are alkaline mafic rocks of sodic affinity and their more evolved differentiation products (e.g., trachytes, phonolites). Strongly silica- undersaturated olivine nephelinites and olivine melilitites characterize the southern sector of the URG as the only primitive mantle melts (Keller et al., 1990). Samples for the present study are from three main volcanic fields in Southwest Germany, namely the Kaiserstuhl, Hegau and Urach areas. The Kaiserstuhl is the largest volcanic to subvolcanic complex of the Upper Rhine Graben and was active between 18 and 13 Ma (Keller et al., 1990). The main rock types exposed are tephrites, essexites, phonolites, basanites (limburgites), olivine nephelinites, hauynophyres, carbonatites and unusual carbonate- and melilite-bearing dyke rocks called bergalites which are considered as transitional between alkaline silicate rocks and carbonatites (Keller et al., 1990). Small occurrences of olivine melilitite are additionally present in the surrounding area, for example at Mahlberg and Lehen. Spinel lherzolite nodules are found in some of the olivine nephelinites and olivine melilitites which are considered to represent relatively primitive mantle-derived melts (e.g., Keller et al., 1990). Other evolved rocks, such as basanites, tephrites, essexites, phonolites and hauynophyres, are assumed to reflect variable degrees of fractionation, potentially combined with minor amounts of crustal contamination (Keller et al., 1990). The Hegau and Urach volcanic fields are situated in the adjacent regions east of the URG. Volcanic activity in both regions took place between about 16 and 7 Ma (Keller et al., 1990). Olivine melilitites (and melilite-bearing olivine nephelinites) and phonolites are two major rock types exposed in the Hegau area (Keller et al., 1990). The Urach field is known for its more than 350 diatreme centers consisting of olivine melilitites and (olivine) nephelinites and lack of more evolved rocks.

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Mineralogical, petrological and geochemical studies show that these primitive rocks are very similar to the olivine melilitites and olivine nephelinites from the Kaiserstuhl and its surroundings (Keller et al., 1990). For this study we investigated 51 powdered whole-rock samples from alkaline igneous rocks of the Kaiserstuhl, Hegau and Urach areas, including 13 relatively primitive olivine nephelinites and olivine melilitites and 38 variably evolved alkaline rocks.

3. Results and discussion

The thirteen olivine nephelinites and olivine melilitites reveal a narrow range of F concentrations (900-1300 µg/g), with no significant differences among sample localities. Their Cl contents are low (10-100 µg/g), except for two outliers from the Kaiserstuhl (900 and 2200 µg/g). Bromine concentrations correlate with Cl, showing low contents (<0.3 µg/g) in Cl-poor samples and relatively higher ones (2 and 5 µg/g) in the two Cl-rich outliers. In contrast, the evolved alkaline rocks display larger variations in all halogens. Their F contents generally vary from 400 to 1400 µg/g, whereas Cl and Br vary largely from 50 to 7700 µg/g and from 0.4 to 34 µg/g, respectively, and are clearly higher than values of the primitive rocks. Variations of halogen contents in bulk rocks are predominantly related to the constituting halogen-bearing minerals. The F contents in most investigated rocks roughly increase with increasing CIPW-calculated apatite abundance, indicating that apatite is an important F-carrier in these samples. However, contributions from other halogen-bearing minerals are also apparent. For example, the phonolitic rocks are relatively poor in apatite but contain abundant titanite and thus show the most pronounced deviation in the bulk F contents vs. apatite volume correlation diagram. For Cl and Br, the highest concentrations are present in hauynophyres, phonolites and bergalites, due to the significant amounts of sodalite-group minerals in these samples. Considered as the most primitive mantle-derived melts (Keller et al., 1990), olivine nephelinitic and olivine melilititic samples were used to constrain the composition of their source mantle based on their halogen signatures. Because Cl and Br are strongly incompatible and are preferably enriched in melts rather than residual solids during partial melting, the low Cl and Br concentrations (10-100 µg/g for Cl and < 0.3 µg/g for Br) of the olivine nephelinites and olivine melilitites place an upper limit to the Cl and Br abundances of the source mantle. However, this conclusion ignores the effect of halogen emission during degassing. Two lines of evidence seem to support the missing of degassing processes to these samples; (1) their low Cl and Br concentrations are similar to previous estimates for the primitive mantle and the lower end of values reported for MORB and OIB samples (e.g., Jambon et al., 1995; Saal et al., 2002; Kendrick et al., 2012); and (2) these low Cl values are much lower than the reported Cl solubility in phonolitic melts (0.6-0.8 wt%). The F concentrations of the investigated olivine nephelinites and olivine melilitites are fairly constant (around 1100 ± 100 µg/g) and are much higher than estimates for the primitive and depleted mantle (Pyle and Mather, 2009). This indicates that mantle-derived nephelinitic and melilititic rocks are much higher in F than typical MORB and OIB samples, which could be caused by high F concentrations of the source mantle, or alternatively, by different degrees of mantle melting. Displaying large variations, the halogen concentrations of evolved rocks could have undergone various modifications during fractional crystallization and degassing and thus are used to constrain halogen behavior during magmatic processes. Modeling of magma/crystal fractionation generally shows that F, Cl and Br concentrations increase with magma evolution because of their incompatible behavior. From our sample suite, however, there is no clear indication that halogen concentrations vary systematically with magma differentiation, which could be attributed to the retention and

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Acknowledgements

This study was financially supported by National Nature Science Foundation of China (Grants 41272079).

References

Aiuppa, A., Baker, D.R., Webster, J.D., 2009, Halogens in volcanic systems. Chemical Geology, v. 263(1), 1-18.

Jambon, A., Déruelle, B., Dreibus, G., Pineau, F., 1995, Chlorine and bromine abundance in MORB: the contrasting behaviour of the Mid-Atlantic Ridge and East Pacific Rise and implications for chlorine geodynamic cycle. Chemical Geology, v. 126(2), 101-117.

Keller, J., Brey, G., Lorenz, V., Sachs, P., 1990, IAVCEI 1990 Pre-conference Excursion 2A: Volcanism and Petrology of the Upper Rhinegraben (Urach-Hegau-Kaiserstuhl). 1-60.

Kendrick M.A., Arculus R., Burnard P., Honda, M., 2013, Quantifying brine assimilation by submarine magmas: Examples from the Galápagos Spreading Centre and Lau Basin. Geochimica et Cosmochimica Acta, v. 123, 150-165.

Kendrick, M.A., Kamenetsky, V.S., Phillips, D., Honda, M., 2012, Halogen systematics (Cl, Br, I) in mid-ocean ridge basalts: A Macquarie Island case study. Geochimica et Cosmochimica Acta, v. 81, 82-93.

Köhler, J., Schönenberger, J., Upton, B., Markl, G., 2009, Halogen and trace-element chemistry in the Gardar Province, South Greenland: subduction-related mantle metasomatism and fluid exsolution from alkalic melts. Lithos, v. 113(3), 731-747.

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Mangler, M.F., Marks, M.A.W., Zaitzev, A.N., Eby, G.N., Markl, G., 2014, Halogen (F,Cl, and Br) at Oldoinyo Lengai volcano (Tanzania): Effects of magmatic differentiation, silicate –natrocarbonatite melt separation and surface alteration of natrocarbonatite. Chemical Geology, v. 365, 43-53.

Pyle, D.M., Mather, T.A., 2009, Halogens in igneous processes and their fluxes to the atmosphere and oceans from volcanic activity: A review. Chemical Geology, v. 263(1), 110-121.

Saal, A.E., Hauri, E.H., Langmuir, C.H., Perfit, M.R., 2002, Vapour undersaturation in primitive mid-ocean- ridge basalt and the volatile content of Earth's upper mantle. Nature, v. 419, 451-455

Schilling, J.G., Unni, C.K., Bender, M.L. 1978. Origin of chlorine and bromine in the oceans. Nature, v. 273, 631-636.

Webster, J.D., Kinzler, R.J., & Mathez, E.A., 1999, Chloride and water solubility in basalt and andesite melts and implications for magmatic degassing. Geochimica et Cosmochimica Acta, v. 63(5), 729-738.

Wilson, M., Downes, H., 2006, Tertiary-Quaternary intra-plate magmatism in Europe and its relationship to mantle dynamics. Geological Society of London.

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Comparison of coastal change in the Gulf of Thailand and the Andaman Sea: case study in Nakhon Si Thammarat and Trang Provinces, southern Thailand

Namporn Wattanaton*, Chongpan Chonglakmani School of Geotechnology, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima, 30000 Thailand *Corresponding author’s e-mail address: [email protected]

Abstract Thailand has an extensive coastal area covering 23 provinces of the eastern Gulf of Thailand coast of the Pacific Ocean and western Andaman Sea coast of the Indian Ocean. Thailand comprises extensive coastline totaling about 2,637 kilometers in length (DMR, 2002). The Gulf of Thailand coastline extends for 1,700 kilometers and the Andaman Sea coastline for 937 kilometers. These coastal zones are endowed with rich natural resources and are, therefore, important for economic development of the country. In the past, the coastlines have been changed mainly by natural processes, but currently are suffering from human activity including beach pollution, coastal erosion, reduction of coastal wetland, and reduction in sediment supply. In the gulf of southern Thailand, the coast of Nakhon Si Thammarat Province is about 190 kilometers in length and it lies within the Khanom, Sichon, Tha Sala, Muang, Pak Panang and Hua Sai districts. In the Andaman Sea, the coast of Trang Province is about 150 kilometers in length and it lies within the Sikoa, Kantang, Hat Samran, and Palian districts. This study uses the Landsat ETM+ satellite imagery scene 128/54, 129/54 and 129/55 acquired in four periods of 1989, 1994, 2001 and 2004. The SPOT imagery scene 263/332, 263/335, 263/336, and 264/333 was acquired in two periods of 2006, 2007. The THEOS imagery scene 263/332, 264/333, and 265/334 werecacquired in two periods of 2007 and 2009. In this study image transformation techniques are used for classification of land and water or coastline by using the ENVI program and GIS techniques. The satellite images were processed and analysed using the Normalized Difference Water Index (NDWI), decision tree classification and field investigations. The NDWI method reveals the distribution of water and land bodies. The NDWI value is used in decision tree classification and the best value for classification is 0.25. Then the decision tree classification is used for indicating the coastline and field investigations are used to recheck the coastline analysis. The classification of land and water and the mapping of coastlines in two periods have been accomplished using remote sensing. In Nakhon Si Thammarat Province coastal erosion is severe and has affected a segment more than 60 kilometers long. The prominent coastal erosion area is in Ban

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Laem Talumphuk and Ban Ao Bon with a rate of 4.48 meters per year and 8.79 meters per year, respectively during 2004 to 2007. In Trang Province the coastal erosion is severe and has affected about 25 kilometers of beach. The main coastal erosion areas are Hat Ratcha Mongkhon and Hat Pak Meng with rates of 1.92 meters per year and 1.70 meters per year, respectively during 1989 to 2001. Keywords: Coastal Change, Remote Sensing, NDWI, Decision Tree Classification

Acknowledgement

The Royal Golden Jubilee Program of the Thailand Research Fund (RGJ-TRF)

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Generation of appinitic magmas of the Xiadawu pluton, East Kunlun orogen, Northern Tibetan Plateau, by partial melting of a mixed mantle

Fuhao Xiong1,2, Changqian Ma3* 1.College of Earth Sciences, and Key Laboratory of Tectonic Controlled Mineralization and Oil Reservoir 2.Ministry of Land and Resources, Chengdu University of Technology, Chengdu 610059, PR China 3.State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, PR China *Corresponding author’s e-mail address: [email protected]

Abstract The appinite suite is commonly generated from a mantle source metasomatised by fluids or melts in varied geologic settings and thus holds the key to understanding geodynamic and magmatic processes. This study presents geochronological, geochemical and Sr-Nd-Hf isotopic data for one Ordovician appinitic pluton from the Proto-Tethyan suture zone in the East Kunlun orogen, Northern Tibetan Plateau. LA-ICP-MS zircon U-Pb dating of mafic appinites and associated granodiorites implies that they originated at 449 and 451 Ma, respectively. The mafic appinites consist of hornblende-rich gabbroic diorites, with low contents of SiO2 (48.62-54.95 wt.%), high contents of FeOT (7.90-12.84 wt.%) and MgO (4.32-11.89 wt.%) and high values of Mg# [Mg# = molar 100*Mg/(Mg+Fe); 49-69], enrichment in large ion lithophile elements and depletion in high field 87 86 strength elements, with initial Sr/ Sr ratios of 0.70536 to 0.70617, εNd(t) of 0.79 to 3.02 and zircon

εHf(t) from 10.84 to 12.82. The associated granodiorites exhibit calc-alkaline characteristics, and have similar rare earth and trace elements patterns and identical depleted Sr-Nd-Hf isotopic compositions

87 86 to the mafic appinites (( Sr/ Sr)i = 0.70564 - 0.70589, Nd(t) = 2.01 - 2.09, εHf(t) = 8.73 - 12.77). These features and geochemical modeling suggest that their parental magma was generated by partial melting of a mixed mantle source consisting of depleted mantle (ca. 75-80%) and subducted sediment- derived melts (ca. 20-25%). The mafic appinites and coeval granodiorites were derived by the fractional crystallization of the parental magma. The mafic appinitic magmatism not only constrains the time of Proto-Tethyan ocean subduction in the East Kunlun orogen, but also provides a vital probe to study the processes of mantle enrichment and transformation. It is probable that long-lived subduction during the early Paleozoic in the East Kunlun orogen introduced numerous sediments into the primary depleted mantle, resulting in metasomatism and mixing leading to formation of a new mantle characterized by an arc-related geochemical imprint. Keywords: Appinite, Geochemistry, Petrogenesis, Mantle enrichment, East Kunlun Orogen

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Figures and Tables

Fig. 1. C1-chondrite-normalized REE patterns and primitive mantle-normalized trace element spider diagrams for the studied gabbroic diorites, Proto-Tethyan MORB, Shaliuhe gneiss and the simulated mixtures.

Fig. 2. Variations in εHf(t) vs. TDM for the Paleozoic Proto-Tethyan orogeny-related mafic appinites in the East Kunlun, exhibiting a mantle enrichment trend.

Acknowledgements

This study was financially supported by China Geological Survey (Grant 1212011121270) and National Nature Science Foundation of China (Grants 41272079 & 90814004).

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Three dimensional exhumation process of the greater Himalayan Complex above the main Himalaya thrust

Zhiqin Xu State Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Corresponding author’s e-mail address: [email protected]

Abstract The Greater Himalayan Complex (GHC) is characterized by high-grade (up to granulite facies) metamorphic rocks exhumed from the middle to lower crust, widespread migmatites from extensive anatectic processes and high-temperature ductile deformation, suggesting that the Himalayan orogen is a ―hot‖ collisional orogen. For a long time, the southward exhumation of the GHC was assumed to occur between the Main Central Thrust (MCT) and the South Tibet Detachment (STD) at ~24‒10 Ma. However, our previous studies in the GHC revealed the widespread presence of a sub-horizontal ductile detachment with orogen-parallel stretching lineation in the upper part of the GHC, which can be traced from the Purang area in the western Himalaya to the eastern Namche Barwa Syntaxis. The U‒Pb ages of metamorphic zircon rims and 40Ar/39Ar cooling ages of mica and hornblende indicate that the orogen-parallel extension in the GHC is asymmetric: initiated first in the central GHC and moved faster eastward (28‒26 Ma in the Nyalam and Jilong areas), but migrated slower westward (22 Ma in the Purang area). The lateral flow along the orogen-parallel detachments continued to 13‒11 Ma, coeval with the activation of the MCT and STD. In this study we identified a large-scale ductile thrust shear zone in the GHC in the Beni-Jamson cross-section, Central Nepal, which is characterized by high-temperature quartz fabric (>650 °C), syn-tectonic felsic veins and a top-to-the-south shear sense. This thrust shear zone began the high- temperature ductile deformation at 34 Ma in the top of the GHC, and progressively migrated to the south at 26 Ma in the lower part of the GHC, i.e., earlier than the activation of the STD and MCT. Combined with seismic profiles across the Himalaya, we interpret this thrust shear zone as the exposed Main Himalaya Thrust (MHT). Activation of the MHT probably triggered the emplacement of late Eocene leucogranites in the Lagugoi Ganri metamorphic domes of the Tethys Himalaya. Therefore, we propose a 3-D exhumation process of the GHC as follows: (1) Initial activation of the MHT triggered partial melting of a thickened crust at 45‒36 Ma and resulted in a weak and hot GHC; (2) Top-to-the-south thrusting along the MHT formed a thick shear zone in the GHC in the Oligocene (34 ‒ 26 Ma); (3) Initial orogen-parallel gravitational collapse occurred in the late Oligocene in the central and eastern GHC (28‒26 Ma); (4) Widespread orogen-parallel extension and southward extrusion of the GHC in the Early-Middle Miocene, accompanied with activation of the STD and MCT (24‒10 Ma) under upper-amphibolite to greenschist facies metamorphic conditions. Subsequently, the MHT migrated southward and produced the Main Boundary Thrust and Main Frontal Thrust between 10 and 5 Ma.

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Alkaline basalts in the Karamay ophiolitic mélange, southern Central Asian Orogenic Belt

Gaoxue Yang1,2*, Yongjun Li1,2, M. Santosh3, Wenjiao Xiao4,5, Baokai Yang2, Lili Tong1,2, Shenglong Zhang2 1. Ministry of Education Key Laboratory of Western China’s Mineral Resources and Geological Engineering, Xi′an 710054, China 2. School of Earth Science and Resources, Chang′an University, Xi′an 710054, China 3. School of Earth Sciences and Resources, China University of Geosciences, Xueyuan Road, Haidian District, Beijing, 100083, China 4. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 5. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China *Corresponding author’s e-mail address: [email protected]

Abstract Here we report geological, geochronological, geochemical, and whole-rock Sr-Nd isotopic data for alkaline basalts from the Karamay ophiolitic mélange of West Junggar, southern Central Asian Orogenic Belt (CAOB). U–Pb analyses of zircon grains from a representative basalt by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded a crystallization age of ca. 395 ± 3 Ma, suggesting formation during the Middle Devonian. Geochemically, all the samples bear the signature of ocean island basalt (OIB), and are characterized by alkaline affinity. The results suggest that all the alkaline basalts were derived from a mantle plume-related source in an intra-oceanic setting. These observations, in combination with previous work, indicate that the alkaline basalts from Karamay can be correlated to Middle Devonian mantle plume magmatism within the Paleo-Asian Ocean. Keywords: Ophiolitic mélange, Mantle plume, Zircon geochronology, Geochemistry, West Junggar, Central Asian Orogenic Belt

1. Introduction

Ophiolites represent fragments of upper mantle and oceanic crust (Nicolas, 1989), and their secular evolution during Earth history has been a major topic of recent research (e.g., Furnes et al., 2014). In a recent synthesis, ophiolites have been grouped into continental margin, mid-ocean ridge, plume, supra-subduction zone, and volcanic arc types (Dilek and Furnes, 2011, 2014). Alkaline basalts are common constituents in many ophiolite belts and accretionary complexes. Here we report geological, geochronological, geochemical, and whole-rock Sr-Nd isotopic data for alkaline basalts from the Karamay ophiolitic mélange of West Junggar, southern Central Asian Orogenic Belt (CAOB; Şengör et al., 1993; Windley et al., 2007; Wilhem et al., 2012; Kröner et al., 2014; Xiao and Santosh, 2014; Figure 1).

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2. Results

In the ophiolitic mélange, imbricate thrusts, duplexes, “web” structures, pinch-and-swell structures, tilted structures in pillow metabasalts, and shear band cleavages are widely developed. U– Pb analyses of zircon grains from a representative basalt by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded a crystallization age of ca. 395 ± 3 Ma, suggesting formation during the Middle Devonian. Geochemically, all the samples bear the signature of ocean island basalt

(OIB), and are characterized by alkaline affinity with high concentrations of Na2O + K2O (4.22-7.28 wt.%) and TiO2 (1.72-2.89 wt.%), LILE and LREE enrichment and HREE depletion ((La/Yb)N = 8.4- 15.6), with very strong or no Eu anomalies (Eu/Eu* = 0.6-1.1), and no obvious Nb, Ta or Ti negative anomalies. The rocks display consistent Sr–Nd isotopic compositions (initial 87Sr/86Sr ratios = 0.70326-0.70453, and εNd(t) = +3.1 to +7.6). The results suggest that all the alkaline basalts were derived from a mantle plume-related source in an intra-oceanic setting with ca. 1-3% degrees of partial melting of garnet lherzolite.

3. Discussion and Conclusions

The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogens in the world and comprises island arcs, ophiolites, seamounts, accretionary prisms, oceanic plateaus, and microcontinents accreted during closure of the Paleo-Asian Ocean from the late Mesoproterozoic to the Mesozoic (Şengör et al., 1993). The ophiolitic mélanges in the CAOB are therefore keys to evaluate the geodynamic evolution of the ancient oceanic realm. Although alkaline basalts occur in many ophiolite belts and accretionary complexes (Safonova and Santosh, 2014), they can easily be overlooked, in the absence of focused investigations. Although typically of relatively small volume in accretionary complexes, alkaline basalts and OIB-type basalts carry critical information related to either continuous or episodic mantle plume magmatism. The various features described in this study suggest that the alkaline basalts from the Karamay ophiolitic mélange might represent an oceanic island or seamount formed in an intraplate setting, and probably originated from an upwelling mantle plume during the Middle Devonian. In a previous study, Safonova (2009) suggested that the intraplate magmatism (OIB, OIB-type basalts) in the CAOB occurred during two major periods, Late Neoproterozoic–Early Paleozoic and Late Paleozoic–Mesozoic, with a Middle Paleozoic hiatus of about 100 Ma. This gap could be explained by a mantle plume periodicity of 120 and 90 Ma, although some authors suggested even 30 and 10 Ma periodicities of mantle plume magmatism. Recently, Safonova and Santosh (2014) summarized Middle Paleozoic, OIB-bearing units in the CAOB, showing the number is obviously less than that of Late Neoproterozoic–Early Paleozoic and Late Paleozoic–Mesozoic units. Based on the above observations and discussions, and in combination with previous work (Yang et al. 2012a, b, 2013), we suggest that plume-related activity in the CAOB was generally continuous during development of the Paleo-Asian Ocean from the late Mesoproterozoic to the Mesozoic. However, its scale/intensity so far identified is relatively small during the Middle Paleozoic. This could be due to our limited knowledge on the accreted OIB or OIB-bearing units that are poorly preserved in the suture zones of CAOB, and warrants further investigation.

Figures and Tables

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Fig. 1 a. Location of the study area within the Central Asian Orogenic Belt (Windley et al., 2007); b. Geological map of the West Junggar region (Yang et al., 2012a).

Acknowledgments

This research was financially supported by the National Nature Science Foundation of China (41303027) and Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (2014G1271058).

References

Dilek, Y., and Furnes, H., 2011. Ophiolite genesis and global tectonics: geochemical and tectonic fingerprinting of ancient oceanic lithosphere. Geological Society of America Bulletin, v. 123, p. 387-411.

Dilek, Y., and Furnes, H., 2014. Ophiolites and Their Origins. Elements, v. 10, p. 93-100.

Furnes, H., Dilek, Y., and de Wit, M., 2014 Precambrian greenstone sequences represent different ophiolite types. Gondwana Research, doi.10.1016/j.gr.2013.06.004.

Kröner, A., Kovach, V., Belousova, E., Hegner, E., Armstrong, R., Dolgopolova, A., Seltmann, R., Alexeiev, D.V., Hoffmann, J.E., Wong, J., Sun, M., Cai, K., Wang, T., Tong, Y., Wilde, S.A., Degtyarev, K.E., and Rytsk, E., 2014. Reassessment of continental growth during the accretionary history of the Central Asian Orogenic Belt. Gondwana Research, v. 25, p. 103-125.

Safonova, I.Y., Utsunomiya, A., Kojima, S., Nakae, S., Tomurtogoo, O., Filippov, A.N., and Koizumi, K., 2009. Pacific superplume-related oceanic basalts hosted by accretionary complexes of Central Asia, Russian Far East and Japan. Gondwana Research, v. 16, p. 587-608.

Safonova, I.Yu., and Santosh, M., 2014. Accretionary complexes in the Asia-Pacific region: Tracing archives of ocean plate stratigraphy and tracking mantle plumes. Gondwana Research, v. 25, p. 126-158.

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Wilhem, C., Windley, B.F., and Stampfli, G.M., 2012. The Altaids of Central Asia: a tectonic and evolutionary innovative review. Earth-Science Reviews, v. 113, p. 303-341.

Windley, B.F., Alexeiev, D., Xiao, W., Kröner, A., and Badarch, G., 2007. Tectonic models for accretion of the Central Asian Orogenic Belt. Journal of the Geological Society, London, v. 164, p. 31-47.

Xiao, W.J., and Santosh, M., 2014. The western Central Asian Orogenic Belt: A window to accretionary orogenesis and continental growth. Gondwana Research, v. 25, p. 1429-1444.

Yang, G.X., Li, Y.J., Santosh, M., Gu, P.Y., Yang, B.K., Zhang, B., Wang, H.B., Zhong, X., and Tong, L.L., 2012a. A Neoproterozoic seamount in the Paleoasian Ocean: Evidence from zircon U–Pb geochronology and geochemistry of the Mayile ophiolitic mélange in West Junggar, NW China. Lithos, v. 140-141, p. 53- 65.

Yang, G.X., Li, Y.J., Santosh, M., Yang, B.K., Yan, J., Zhang, B., and Tong, L.L., 2012b. Geochronology and geochemistry of basaltic rocks from the Sartuohai ophiolitic mélange, NW China: Implications for a Devonian mantle plume within the Junggar Ocean. Journal of Asian Earth Sciences, v. 59, p. 141-155

Yang, G.X., Li, Y.J., Santosh, M., Yang, B.K., Zhang, B., and Tong, L.L., 2013. Geochronology and geochemistry of basalts from the Karamay ophiolitic mélange in West Junggar (NW China): Implications for Devonian-Carboniferous intra-oceanic accretionary tectonics of the southern Altaids. Geological Society of America Bulletin, v. 125, p. 401-419.

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Diamonds and highly reduced minerals in ophiolitic mantle rocks and chromitites

J.S. Yang1,2*, X.X. Zhang2, X.Z. Xu1, Zh.M. Zhang1, Zh. Huang1, P. T. Robinson1, Y. Dilek3, W.L. Griffin4 1 CARMA, State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037,China 2. China University of Geosciences, Wuhan, 430074, China 3 Dept of Geol & Env Earth Science, Miami University, Oxford, OH 45056, USA 4 CCFS/GEMOC, Earth and Planetary Sciences, Macquarie University, NSW 2109 Australia *Corresponding author’s e-mail address: [email protected]

Abstract Ophiolitic mantle rocks and chromitites are generally thought to have formed near the top of the upper mantle. However, our discovery of diamonds and highly reduced minerals in ophiolitic chromitites significantly challenges this model. Some new progresses are summarized as below: 1. A very significant milestone is that the diamonds have now been shown to occur in situ within chromite grains from the Luobusa and Polar Ural chromitites. This discovery has ended all doubts about the diamonds being the result of contamination during sample processing. Previously such contamination could not be conclusively ruled out because all the diamonds had been obtained from mineral separates. 2. The C isotope compositions and mineral inclusions of the diamonds from Luobusa and the Polar Urals are very similar, with the diamonds being characterized by their light C isotopes (δ13C - 18 to -28) and typical Mn-bearing mineral inclusions, such as Mn-olivine, Mn-garnet, Mn-spinel and Co-Mn-Ni alloy. These features, along with their typical occurrence in oceanic mantle rocks, clearly distinguish these diamonds from kimberlite diamonds within cratons and UHP metamorphic diamonds at plate margins. Thus, we propose a new occurrence of diamond on Earth, termed ophiolite-hosted diamond. 3. We have greatly expanded the number of ophiolites known to contain diamonds. Diamonds and highly reduced minerals have now been confirmed in mantle peridotites or chromitites from 11 ophiolites in 5 orogenic belts in different parts of the world. These include the Luobusa, Zedang, Xigaze, Dangqiong, Parang and Dongbo massifs in the Yarlung Zangbo suture and the Dingqing massif in the Bangong-Nujiang suture of Tibet, the Myitkyina massif in Myanmar, the chromitites in the Sartohai and Hegenshan massifs of the Central Asia Orogenic Belt, and the Ray-Iz massif in the Polar Urals. Thus, we propose that diamonds and their associated unusual minerals may be common within oceanic mantle, although not present in great abundance. If this can be proven with future

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Tethys: an archipelagic ocean model

Hongfu Yin China University of Geosciences, Wuhan Corresponding author’s e-mail address: [email protected]

Abstract Tethys (sensu lato) can be categorized into Paleotethys, Mesotethys and Neotethys successively. In contrast to such typical wide and ‗clean‘ oceans as the Atlantic, in all its evolutionary stages Tethys, especially eastern Tethys, has always been an archipelagic ocean containing many continental blocks (delineated partly by rifts) and microplates (delineated by sutures). The blocks and microplates were all formed during the general process of Gondwana dispersal and Asia accretion, through rift extension, northward migration and final integration of belts of blocks with Eurasia such as the Tethysides and Cimmerides. This paper will focus on the archipelagic eastern Eurasian Tethys consisting of the Qinling- Qilian-Kunlun, South China and Xizang-Yunnan regions. The Qinling-Qilian-Kunlun Region includes the Jiangsu-Shandong Belt (SULU), Dabie Mts., Qinling, Qilian and Kunlun Mts. It was originally composed of a series of micro-plates plus a row of Early Paleozoic micro-oceans to its north (Central Asia-Mongolia Ocean) and a row of Late Paleozoic micro-oceans to the south (Palaeotethys). SULU, Dabie, Central Qinling, Central Qilian and Qaidam are the main microplates, characterized by epeiric and continental deposits. They form the earliest and northernmost row of microplates in Tethys. In addition, there were smaller blocks in Palaeotethys. Between North China and the Central Qinling microplate there were at least two rows of island arcs: the southern arc made by the Qinling Group and the northern one by the Kuanping Group. Eastern Kunlun also consists of blocks that underwent multiphase rift-collision subcycles (polycyclicity) to finally form an orogenic belt, The South China Region includes thee Yangtze Plate, Lower Yangtze Block, Cathaysia Microplate, Nanpanjiang Block and rifted blocks along the western margin of Yangtze - Songpan- Garze, Zhongzai, and Qamdo-Simao. The Yangtze and Cathaysia blocks began to collide during the Late Proterozoic. Nanpanjiang was a block rifted from the Yangtze Plate in the Late Palaeozoic. Songpan-Garze, Qamdo-Simao and Zhongza Blocks, were parts of Yangtze the experienced riftogenesis, accretion or sagging in the Palaeozoic. Their fossils generally show tropical to subtropical Palaeotethyan affinity. Ediacaran to Triassic paleolatitudes show that these blocks were not fully incorporated until the Triassic Indosinian Orogeny. The Tibet-Yunnan Region includes the North and South Qiangtang Microplates and the Gandis- Lhasa-Baoshan Microplates which connect with SIBUMASU Microplates southward. Biota of the Gondwana type and Late Paleozoic tillites are common features in this area, attributing it to a

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Gondwana margin. These microplates rifted away from Gondwana during the Mesozoic (along the Bangong Co-Dingqing and Nujiang faults,) and Cenozoic (Yarlung-Zangbo suture), forming Mesotethys and Neotethys successively. The intermediate area between the pro-Gondwanan Baoshan Block and pro-Yangtze Qamdo-Simao Block consists of, from west to east, the Changning-Menglian Belt, the Lincang Block and the Lancangjiang Belt. The two belts were branches of the archipelagic Paleotethys. Characteristics of the archipelagic Tethys 1. Archipelagic vs. clean ocean, with an intercalated series of microplates and micro-ocean basins. 2. Soft collision occurred between blocks moving along the same (northward) direction but with different speeds and directions of rotation, e.g. the leading block stopped due to collision with Eurasia, or the trailing block caught up. The motional energy (1/2mv2) of such collisions is much smaller than that of head-on collisions between plates, because here v is the difference, rather than the sum of velocities of the two blocks, and the m of the blocks is much smaller. The collision may not have occurred in a single event, but rather in a stepwise process.. 3. Polycyclicity--each collision caused by unidirectional (northward) movements with unequal velocities can speed up the northward shift of the leading bloc;, meanwhile the reaction can slow down the northward migration of the trailing one. Thus, after each collision there will follow a process of extension and then compression. An orogeny can occur only when the leading block collides with a fixed plate and stops, and successive block collide with the leading one, and are underthrusted and subducted. An orogeny would not immediately follow block collision, but may be delayed up to 100 m.y. or more, during which several openings and closures may take place--this is the mechanics of polycyclicity. The modern Indian Ocean was formed through dispersal of previous Gondwanan blocks including the Arabian Peninsula, Indian Subcontinent and Australia, which have been (or will be) accreted with Eurasia, and in this sense the Indian Ocean could be called Modern Tethys. The history of archipelagic Tethys may help to comprehend and predict analogous evolutions of SE Asia archipelagic micro-oceans.

References

Yin Hongfu and Huang Dinghua, 1996, Early palaeozoic evolution of the Zhen'an-Xichuan Block and the small Qinling Multi-island Ocean Basin. Acta Geologica Sinica, 9(1):1-15.

Yin Hongfu, 1998, Tethys--an archipelagic ocean model. Proc. 30th Int'l Geol. Congr., 11:91-97.

Yin Hongfu, Wu Shunbao, Du Yuansheng, Yan Jiaxin and Peng Yuanqiao, 1999, South China as a part of archipelagic Tethys during Pangea time. In Yin Hongfu and Tong Jinnan (eds.): Proceedings of the International Conference on Pangea and the Paleozoic-Mesozoic transition. China Univ. Geos. Press, Wuhan, 1999,69-73.

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Yin Hongfu, J.M.Dickins, G.R.Shi and J.Tong (eds.), 2000, Permian-Triassic evolution of Tethys and western Circum-Pacific. Developments in Palaeontology and Stratigraphy, 18, Elsevier Press, Amsterdam, 392pp.

Yin Hongfu, Zhang kexin and Feng Qinglai, 2004, The archipelagic ocean system of the eastern Eurasian Tethys. Acta Geologica Sinica, 78(1):230-236.

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Nb/Ta fractionation in the skarn system: evidence from in-situ textures and chemical analysis of magnetite of the Baishiya iron deposit, East Kunlun orogenic belt

Shuo Yin1,2, Changqian Ma1,2* 1. State Key Laboratory of Geological Processes and Mineral Resources，China University of Geoscience，Wuhan 430074，China 2. Faculty of Earth Sciences，China University of Geoscience，Wuhan 430074，China *Corresponding author’s e-mail address: [email protected]

Abstract The ―missing Nb paradox‖ based on subchondritic Nb/Ta ratios in both continental crust and depleted mantle has been a complicated problem for geologists. Magnetite formed in magmatic- hydrothermal systems with distinct mineral assemblages may be enriched in variable trace elements which can be used to trace the evolution of the hydrothermal fluids. In this article, we provide in-situ textural and trace element data for magnetite collected from different sites in the Baishiya iron deposit, East Kunlun orogenic belt. The samples were analyzed by scanning electron microscope and LA-ICP- MS, to reveal more details about Nb/Ta fractionation in a skarn system, which has rarely been observed previously. Four stages of mineralization have been determined: iron skarnization, hydrothermal alteration, carbonization and sulfide mineralization. Backscattered images revealed that the magnetite grains in the iron-bearing skarns and other rocks have obvious oscillatory zoning. The trace elements in the magnetite, particularly the high field-strength elements (Nb, Ta, Zr, Hf) and Ti, show systematic variations correlated with the zoning. Other elements (e.g., Si, Al, Ca, W, Ni, V) vary suggesting the influence of some other minerals that crystallized synchronously with the magnetite. Twenty-two samples of magnetite from the 4 stages have been analysed for trace elements and textural variations. Nb/Ta fractionation in magnetite may be common in hydrothermal fluid metasomatic systems, considering the high Si and Al contents in magnetite reported by many geologists previously. The observed zoning textures most likely represents changes in fluid composition and/or physiochemical parameters (such as temperature, pH, and perhaps even redox conditions), that could also periodically change the partitioning behavior of trace elements into magnetite during its precipitation. An enrichment of Nb in the rims of these magnetite crystals, with a slight decrease in Ti implies that Nb/Ta fractionation is not controlled by temperature. The influence of other minerals crystallizing during skarn formation may also be excluded due to the absence of minerals with high contents of Nb and Ta (e.g., rutile, titanite and zircon). Because Nb and Ta share with V the inherent property of Group-5 transition elements to adopt multiple valences, the correlation between Nb and V in the

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International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China magnetite grains may reflect variations in oxygen fugacity. Thus, we propose that redox variations control Nb/Ta fractionation in magmatic-hydrothermal metasomatic systems. Our findings may provide new insights into the ―missing Nb paradox‖.

Acknowledgements

This study was financially supported by National Nature Science Foundation of China (Grants 41272079).

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Structural features, prototype-basin reconstruction and petroleum exploration potential of the Bay of Bengal Basin

Peng Zhang1, Lianfu Mei1,2*, Yixing Ma2, Lulu Wu1 1. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, Wuhan 430074, China; 2. Development Research Center of China Geological Survey, Beijing 100037, China *Corresponding author’s e-mail address: [email protected]

Abstract Satellite-derived gravity data processed by applying various image enhancement methods (filter, gradient and continuation) and cross-sections of standardized seismic reflection profiling, are used to analyse the tectonic features and dynamics of the Bay of Bengal Basin. Free-air gravity anomalies obtained by enhanced processing indicate that there are NW-trending fracture zones in the west, EW- trending faults in the Ninetyeast Ridge, and NE-trending linear structures in the east of the basin, which suggest the influence of sea floor spreading, ridge emplacement and Indian Ocean crust subduction, respectively. Based on the standardized seismic reflection proﬁling, gravity anomalies and strata thicknesses, the basin comprises five tectonic/stratigraphic units, and can be divided into five structural elements that are West Depression, 85°E Ridge, Central Depression, Ninetyeast Ridge and Rakhine Depression. Prior to the collision, the sedimentary framework was controlled by multiple isolated rises developed in the 85°E Ridge, in response to episodic eruption processes of the hotspot. The post-collisional sediments known as the Bengal fan sediments were not significantly affected by the ridge and the sediments continuously migrated southward during the Eocene to Miocene. Subduction of the Ninetyeast Ridge promoted the westward growth of the Andaman accretionary prism in the south (7°N-14°N) and controlled the evolution of the Rakhine Depression, Indo-Burmese Wedge and the depocenter of the Bay of Bengal Basin in the north (14°N-20°N). We restored the proto-oceanic basin stage (Later Cretaceous to Early Oligocene) and the remnant ocean basin stage (Later Oligocene to present) of the Bay of Bengal basin since the Late Mesozoic based on detailed marine geophysical investigations and geological evidence. The two main prototype-basins have different geophysical characteristics, structural features and tectonic evolution processes, which result in variations of source rock, traps, hydrocarbon accumulation processes and modes. We propose that source rock and traps might have been related in time and space. Apparently, the tectonic evolution of the basin controlled the formation and evolution of traps and reservoirs in the Bay of Bengal

Basin. Keywords: the Bay of Bengal Basin, Structure features, Dynamics, Basin reconstruction, Petroleum exploration potential

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Fig.1. Trap types and corresponding units of the Bay of Bengal Basin, HARPS=High Amplitude Reflection Packets, are represented by sheet-like down slope sand bodies; CHARS=Chaotic High Amplitude Reflectors, are represented by inter-channel-levee deposit systems.

References

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Alam, M., Alam, M.M., Curray, J.R., et al., An Overview of the Sedimentary Geology of the Bengal Basin in Relation to the Regional Tectonic Framework and Basin-fill History, Sedimentary Geology, 2003, 155(3- 4):179–208.

Bastia, R., Radhakrishna, M., Srinivas, T., et al., Structural and Tectonic Interpretation of Geophysical Data along the Eastern Continental Margin of India with Special Reference to the Deep Water Petroliferous Basins, Journal of Asian Earth Sciences, 2010a, 39(6):608–619.

Bastia, R., Das, S., Radhakrishna, M., Pre- and Post-collisional Depositional History in the Upper and Middle Bengal Fan and Evaluation of Deepwater Reservoir Potential along the Northeast Continental Margin of India, Marine and Petroleum Geology, 2010b, 27(9):2051–2061.

Brune, J.N., Curray, J.R., Dorman, L., et al., A Proposed Super-thick Sedimentary Basin, Bay of Bengal, Geophysical Research Letters, 1992, 19(6):565-568.

Curray, J.R., Emmel, F.J., Moore, D.G., et al., Structure, Tectonics and Geological History of the Northeastern Indian Ocean. In: Nairn, A.E.M., Stehli, F.G. (Eds.). The Ocean Basins and Margins: The Indian Ocean, 6. Plenum Press, New York, 1982, 399–450.

Curray, J.R., Munasinghe, T., Origin of the Rajmahal Traps and the 85°E Ridge: Preliminary Reconstructions of the Trace of the Crozet Hotspot, Geology, 1991, 19(12):1237–1240.

Desa, M., Ramana, M.V., Ramprasad, T., Seafloor Spreading Magnetic Anomalies South of Sri Lanka, Marine Geology, 2006, 229(3-4):227–240.

Hall, R., Late Jurassic–Cenozoic Reconstructions of the Indonesian Region and the Indian Ocean, Tectonophysics, 2012, 570–571:1–41.

Krishna, K.S., Laju, M., Bhattacharyya, R., et al., Geoid and Gravity Anomaly Data of Conjugate Regions of Bay of Bengal and Enderby Basin–New Constraints on Breakup and Early Spreading History between India and Antarctica, Journal of Geophysical Research, 2009, 114(B03102):1-21.

Lee,T.T and Lawver,L.A., Cenozoic Plate Reconstruction of Southeast Asia, Tectonophysics, 1995, 251(1- 4):85–138.

Maurin, T and Rangin, C., Impact of the 90°E Ridge at the Indo-Burmese Subduction Zone Imaged from Deep Seismic Reflection Data, Marine Geology, 2009, 266(1-4):143–155.

Radhakrishna, M., Srinivasa, R.G., Satyabrata, N., et al., Early Cretaceous Fracture Zones in the Bay of Bengal and Their Tectonic Implications: Constraints from Multi-channel Seismic Reflection and Potential Field Data, Tectonophysics, 2012, 522-523:187–197.

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Correlations between deformation and various shortening velocities of a hypothetical fold-and-thrust belt: Evidence from sandbox modeling

Gaoping Zhao, Bin Deng*, Shugen Liu, Yuanbo Wan, Zhiwu Li, Jinxi Li State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation/Chengdu University of Technology, Chengdu, China, 610059.*Corresponding author’s e-mail address: [email protected]

Abstract Brittle deformation in shallow crust is generally characterized by a long tectonic history and complex geological features which result from interdependent parameters. Since the 1810s, tectonic sandbox modeling has been a powerful and indispensable tool to help in providing a uniﬁed picture of the evolution of deformation in shallow crust with considerable spatial and temporal detail based on self-organization and unreasonable effectiveness of tectonics. Using similar initial conditions for a sandbox model (pure quartz sand thickness: 15 mm, 10 mm, 10 mm and red quartz sand thickness: 1 mm), we investigated different geometry, kinematics and evolution of a thrust wedge with various shortening velocities. With a high shortening velocity (0.5-0.1 mm/s, e.g., gravity-driven and earthquake-related event), the thrust wedge in the sandbox model is simple, characterized by piggyback imbricate-thrust structures. The wedge is relatively narrow and thick, with a steady-state taper angle of 5°-14°, and a wedge length of about 410 mm. There are always seven faults in the wedge, and the ramp angle decreases with increasing shortening, finally reaching a steady-state angle of 33°-43° (Table 1 and Figure 1). During evolution of the thrust wedge, the faults do not progressively thrust forward, but show retro-thrusting to cut existing thrust faults, resulting in multiphase activity of wedge and fault. With low shortening velocity (0.05-0.005 mm/s), the thrust wedge in sandbox model is relatively complex, characterized by piggyback imbricate-thrusting and superimposed pop-up structures. Thus, the wedge has a steady-state wedge taper angle of 6°-12°, and is wider and thinner than that formed with a high shortening velocity. There are always eight faults associated with the wedge and the ramp angles range from 30°-50°. In particular, the wedge length increases with increasing retrothrust faults, resulted in out-of-sequence thrusting. When the shortening velocity is very low (0.002 mm/s), the deformation in the thrust wedge is significantly different from the others. It is characterized by Jura- style folds, with seven faults, which have steady-state ramp angles of 36°-43 °. In particular, the wedge taper angle ranges between 8°-11° ,much smaller than all the others, suggesting that Jura-style folds form under low shortening velocities with uniform material, rather than detachment as previously thought. Our sandbox modeling with various shortening velocities revealed differences in deformation structure style in a hypothetical fold-and-thrust belt. Under high velocity, the thrust wedge shows

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Figures and Tables

Fig. 1 The final structural styles under various shortening velocities. It should be noted that there are significant differences in the thrust wedge between high shortening velocity (0.5~0.1 mm/s) and low shortening velocity (0.05~0.005 mm/s), in particular at a velocity of 0.002 mm/s.

Table 1. Summary of experimental parameters and results of the various shortening velocity

Number Of Velocity Wedge Taper Trust Fault Wedge Wedge The Displacement No. Fault(n) Pop-up (mm.s-1) Angel (°) Length(mm) Of Fault(mm) Dip（°） Height(mm） Structure(n)

1 0.5 5-14 33-43 107.098 7 404.042 6 14.364-54.634 2 0.4 5-14 33-42 114.432 7 409.779 6 15.345-51.844 3 0.3 5-14 33-43 104.563 7 410.534 6 16.417-54.958 4 0.2 5-14 33-41 112.977 7 412.063 6 14.643-50.685 5 0.1 5-14 30-50 112.943 7 416.089 6 15.783-51.591 6 0.05 6-12 30-50 104.631 8 447.338 6 11.307-70.709 7 0.005 6-12 36-43 113.746 8 476.251 5 11.234-73.715 8 0.002 8-11 36-43 111.864 7 461.021 5 11.571-52.574

Acknowledgments

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This work was supported by the Natural Science Foundation of China (Nos. 41402119, 2014JQ0057, 41472017), and the National Basic Research Program of China (No. 2012CB214805).

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Zircon U-Pb geochronology, whole-rock geochemical and Lu-Hf isotopic constraints on the petrogenesis of highly evolved I-type rhyolites in the Loei fold belt and their tectonic implications

Tianyu Zhao1, Qinglai Feng1,2* 1. Faculty of Earth, China University of Geosciences, Wuhan, China 2. State Key Laboratory of Geo-processes and Mineral Resources, China University of Geosciences, Wuhan, China *Corresponding author’s e-mail address: [email protected]

Abstract Southeast Asia is composed of a number of terranes that were successively rifted off from Gondwana, drifted northward and accreted to each other. The Indochina Block originated from eastern Gondwana and was rifted away in the Early Devonian (Metcalfe, 2013). The Loei fold belt, situated in the west of Indochina, has been intensely studied regarding the controversy over its regional tectonic evolution (Intasopa and Dunn, 1994; Panjasawatwong et al., 2006; Udchachon et al., 2011; Vivatpinyo et al., 2014). Recently, we found Silurian rhyolites in the Loei fold belt, and the identification of lower Paleozoic volcanic rocks is of significant importance in studying the geological and tectonic evolution this terrane and the reconstruction of Gondwana. We obtained zircon U-Pb ages for the rhyolites, as well as their whole-rock geochemistry and Hf isotope compositions. Zircon grains from Loei rhyolites yielded concordant 206Pb/238U ages, with mean of 423.7±2.7 Ma, suggesting the timing of emplacement was Wenlockian. The Loei rhyolite samples show enriched

SiO2 (75% - 77%), Al2O3 (12.10%-13.13%), K2O (2.97%-3.50%) and low CaO(0.26-0.61%),

Fe2O3T(0.98%-2.24%) and P2O5 (0.05%). The molecular A/CNK ratios of the samples range from 1.19 to 1.34, indicating that they are strongly peraluminous. The rhyolites show moderate negative Eu anomalies (δEu=0.58-0.56). In the primitive mantle-normalised spidergram, all samples are enriched in LILE (e.g., Ba, K, Pb) and LREE and depleted in HFSE (e.g., Th,Nb, Ta, Zr, Ti). The high A/CNK (1.20-1.34) values of the Loei rhyolites resemble those of S-type granites. However, we suggest that the Loei rhyolites are actually highly evolved, I-type rhyolite, because there are no Al-rich minerals in these rocks. In addition, low P granitoids may be highly fractionated I-type granites. On the Rb/Sr vs. Rb/Ba diagram, all of the Loei samples plot within the clay-poor area,which combined with their positive εHf(t) values (4.03 - 5.38) precludes the possibility of being

S-type silicic magmas. In the plots of (Na2O+K2O)/CaO and FeOt/MgO vs. Zr+Nb+Ce+Y, all samples lie in the field of fractionated I-type granites. The concentrations of LILE (such as Ba, K, Pb) in the Loei rhyolites are high, but hey are relatively depleted in HFSE (such as Th, Nb, Ta, Zr, Ti). These are characteristic features of magmas formed in active continental margins in suprasubduction zone settings (Qi et al., 2014). On the La/Yb

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International Workshop on Tethyan Orogenesis and Metallogeny in Aisa October11-16, 2014, Wuhan, China vs. Th/Yb tectonic discrimination diagram, all the Loei rhyolites plot within the area of 'continental margin-arc'. According to the regional geological outline of the Indochina Block, magmatism, metamorphism and deformation were widespread in the region during the Silurian, suggesting subduction of an ocean plate beneath Indochina. Therefore, we argue that the rhyolites from the Loei fold belt were generated from partial melting of juvenile lower crust related to ocean lithosphere beneath the Indochina Block. The primary magma then underwent extensive differentiation.

Figures and Tables

Fig. 1 Geodynamic evolutionary model of the Indochina Block during Mid-Late Silurian

References

Intasopa, S., Dunn, T., 1994. Petrology and Sr-Nd isotopic systems of the basalts and rhyolites, Loei, Thailand. Journal of Southeast Asian Earth Sciences9, 167-180.

Metcalfe, I., 2013. Gondwana dispersion and Asian accretion: Tectonic and palaeogeographic evolution of eastern Tethys. J Asian Earth Sci66, 1-33.

Panjasawatwong, Y., Zaw, K., Chantaramee, S., Limtrakun, P., Pirarai, K., 2006. Geochemistry and tectonic setting of the Central Loei volcanic rocks, Pak Chom area, Loei, northeastern Thailand. J Asian Earth Sci26, 77-90.

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Qi, X., Santosh, M., Zhu, L., Zhao, Y., Hu, Z., Zhang, C., Ji, F., 2014. Mid-Neoproterozoic arc magmatism in the northeastern margin of the Indochina block, SW China: Geochronological and petrogenetic constraints and implications for Gondwana assembly. Precambrian Res245, 207-224.

Udchachon, M., Thassanapak, H., Feng, Q., Chonglakmani, C., 2011. Geochemical constraints on the depositional environment of Upper Devonian radiolarian cherts from Loei, north-eastern Thailand. Frontiers of Earth Science5, 178-190.

Vivatpinyo, J., Charusiri, P., Sutthirat, C., 2014. Volcanic Rocks from Q-Prospect, Chatree Gold Deposit, Phichit Province, North Central Thailand: Indicators of Ancient Subduction. Arabian Journal for Science and Engineering39, 325-338.

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