DOCSLIB.ORG

Petrology, Geochemistry and Geochronology of Late Triassic Volcanics, Kunlun Orogenic Belt, Western China: Implications for Tectonic Setting and Petrogenesis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Petrology, Geochemistry and Geochronology of Late Triassic Volcanics, Kunlun Orogenic Belt, Western China: Implications for Tectonic Setting and Petrogenesis Geochemical Journal, Vol. 39, pp. 1 to 20, 2005 Petrology, geochemistry and geochronology of late Triassic volcanics, Kunlun orogenic belt, western China: Implications for tectonic setting and petrogenesis HONGTAO LIU* Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China (Received November 27, 2003; Accepted April 28, 2004) The Qimantage volcanic suite (QVS) of late Triassic age, dominated by dacitic to rhyolitic lavas and pyroclastic rocks with minor basaltic andesites, outcrops mainly in the middle segment of Qimantage Mt. region, Kunlun orogenic belt, which extends along the northern margin of Tibetan plateau, western China. Petrological and geochemical studies indicate that the volcanic rocks are of typical calc-alkaline affinity with silica contents ranging from ~53 to ~80 wt%, exhibiting a medium- to high-K characteristics. Major element variations define relatively smooth compositional trends, while large ion lithophile (LIL) trace elements correlate positively with increasing SiO2. Chondrite-normalized incompatible trace element spidergram shows conspicuous sparks at Rb and Th, but pronounced Nb and Ti depletion. The chondrite- normalized REE patterns of QVS are generally paralleled to each other, exhibiting highly fractionated LREE/HREE spec- tra with small to pronounced negative Eu anomalies. Two whole-rock Rb-Sr isochrons yield ages of ca. 209 and ca. 225 Ma, respectively, indicating the volcanic suite was emplaced during the late Triassic. The initial 87Sr/86Sr ratios (0.708– 0.709) and initial eNd(t) values (–2.05~–2.35) imply that the magmas were derived from a slightly enriched mantle source with considerable crustal contamination. Considering its petrological, geochemical and isotopic characteristics in a re- gional geological background, it is proposed that QVS was generated upon an active continental margin during the late Triassic north-directed subduction event. Both the volcanics and the closely-related coeval granitoid plutons collectively make up the late Triassic arc magmatic belt on the paleogeographically southern margin of the Tarim continent. Keywords: calc-alkaline volcanic, active continental margin, Kunlun orogen, western China would be very helpful in elucidating the tectonic evolu- INTRODUCTION tion of the Kunlun orogen. A voluminous terrestrial volcanic rocks of late Triassic age, covering an area of about 1800 km2, distributed in REGIONAL GEOLOGY the middle portion of the Qimantage Mt. region (Fig. 1), Kunlun orogenic belt (Jiang et al., 1992), which lies along Within the Qimantage Mt. region and adjacent areas, the northern margin of the Tibetan plateau, western China. stratigraphy underlying QVS comprises pre-Triassic meta- The volcanic rocks are dominated by dacite and rhyolite morphic and non-metamorphic sequences (QPGB, 1985), lavas, subordinate andesites and minor basaltic andesites, including Neoproterozoic, upper Ordovician, upper with vast accumulation of ignimbrites, volcanic breccias Devonian, Carboniferous and Lower Permian and agglomerates of dacitic to rhyolitic composition, in- stratigraphic sequences. The Neoproterozoic Jinshuikou truded by late Mesozoic granitoid plutons and dykes. Group is the oldest stratigraphic unit in the region, com- Because of its geographical remoteness and high altitudes, posed mainly of granulites, plagioclase gneisses, two- few detailed studies on the volcanic rocks have been re- mica plagioclase gneisses, quartz schists, biotite- corded previously. The merely documented but not pub- actinolite schists with some quartzite interlayers. Con- lished data regarding the volcanics are the stratigraphical formably overlying the Jinshuikou Group is the and lithological descriptions by Qinghai Provincial Geo- Neoproterozoic Langyashan Group that is dominated logical Bureau in a regional mapping program scaled at lithologically by marbles, dolomites and quartzites, with 1:200,000 in the early 1980’s (QPGB, 1985). Since QVS minor quartz schists and low-grade metamorphic clastic is an integral part of the Kunlun orogenic belt, detailed sediments, i.e., metasandstones and metasiltstones. petrological, geochemical and geochronological studies Unconformably overlying the Langyashan Group is the Tieshidasi Group of late Ordovician age, which can be subdivided into three sub-units: the lower is mainly of *E-mail address: [email protected]) metaclastic sediments with subordinate metavolcanics, the Copyright © 2005 by The Geochemical Society of Japan. middle part dominated by metavolcanics including 1 the Lower Permian strata. They usually have a very lim- ited distribution and mainly composed of limestones and dolomitic limestones containing abundant early Permian Brachiopoda and Fusulinida fossils. The strata of early to middle Triassic age are absent in the Qimantage Mt. region but are well developed in adjacent areas such as the southern Kunlun region. They consist mainly of marine flysch sediments. As shown in Fig. 1, voluminous Late Paleozoic to Mesozoic granitoid plutons are widely distributed in the Qimantage Mt. region and surrounding areas. Most of those intrusives are elongated in shape and extended along the SE-trending Qimantage Mt. range, indicating fault- controlled plutonic emplacement. Well-developed contact metamorphism between intrusives and country rocks can be frequently observed. It is also recognized that most regional-scaled faults and fractures were developed in the SE direction along the Qimantage Mt. reflecting a unique regional structural pattern. In general, the geology of the Qimantage region is Fig. 1. Geological map of the Qimantage Mt. region. Simpli- characterized by its thick metamorphic and non- fied after Jiao et al. (1988). See text for more description of metamorphic sequences ranging in age from Proterozoic regional geology. to early Triassic, intruded by voluminous late Paleozoic to Mesozoic granitoid plutons (Zhou and Yuan, 2003; Jiang et al., 1999). The most prominent structures in the region are the SE-trending regional faults and fractures. pillowed metabasalts, meta-andesites, and metadacites All these indicate that the region had experienced a long with some intercalations of quartz schists, quartzites and and complicated geological evolution prior to the initia- metasandstones. The upper part consists mainly of lime- tion of the terrestrial volcanism (Jiang et al., 1992; Xu et stones, marbles, dolomites, phyllites and metasiltstones. al., 1994; Xiao et al., 2003). This Group is widely distributed throughout the Qimantage Mt. region and characterized by its consider- PETROGRAPHY able lateral variations in both composition and thickness. The Upper Devonian strata, namely the Qiegaisu Based on field investigation and microscopic studies, Group, are also widely distributed in the region, which is it is recognized that QVS is mainly composed of inter- unconformably over the Tieshidasi Group. It can be mediate to acidic lavas and pyroclastic rocks, with minor lithologically divided into two parts: the lower part is basaltic andesite. The pyroclastic rocks including composed mainly of siltstones, sandstones and calcare- ignimbrites, volcanic breccias and agglomerates of dacite ous siltstones, intercalated with silty limestones, in which to rhyolite compositions make up more than 60 vol% of there are abundant late Devonian fossils; the upper part QVS, indicating relatively strong volcanic eruptions. Due is dominated by lavas and pyroclastic rocks of basaltic- to its considerable lateral variations in both lithology and andesitic-dacitic-rhyolitic compositions, intercalated with thickness, it is very difficult to make a detailed some slate, calcareous siltstone and limestone layers, in lithostratigraphical correlation between adjacent sections. which also contain abundant Brachiopoda and corral fos- The rock colors are also variable ranging from purple- sils of late Devonian. red to greenish-dark with varying grayish hues. Accord- The Carboniferous Dagangou Group is dominated by ing to microscopic examinations and chemical analyses, varying types of limestones intercalated with sandstones the volcanic rocks having red to purple colors are usually and slate layers. A basal conglomerate layer usually oc- dacites to rhyolites, while the rocks with grayish-dark curs. The various limestones including biocalcirudite, colors are commonly andesites and basaltic andesites. In biosparrudite, biopararenite, and silica-bearing limestone, the western area of its distribution, the most common rock contain abundant Carboniferous corral and Brachiopoda types are rhyolites, dacites, and voluminous ignimbrites fossils. The group is also widespread in the Qimantage and volcanic breccias of dacite-rhyolite compositions, Mt. region and possesses pronounced lateral variations with minor andesites and basaltic andesites; whereas in in thickness. Conformably overlying Dagangou Group is the eastern area, although the rock types are similar to 2 H. Liu those in the west, it appears that the pyroclastic rocks are from andesine to oligoclase with varying alteration of more abundant and may reach up to 70 vol%, indicating sericitization and carbonitization. The hornblende and more fiercely explosive eruptions. pyroxene phenocrysts usually exhibit euhedral to In terms of lithologic and facies variations at differ- subhedral shape but partly altered into chlorite and Fe- ent locations, the volcanic activities can be roughly gen- oxide aggregates especially on the rims of the phenocrysts. eralized as following.
Load more

Recommended publications
  • Southward-Directed Subduction of the Farallon–Aluk Spreading Ridge and Its Impact on Subduction Mechanics and Andean Arc Magmatism: Insights From
    feart-08-00121 May 7, 2020 Time: 11:30 # 1 ORIGINAL RESEARCH published: 08 May 2020 doi: 10.3389/feart.2020.00121 Southward-Directed Subduction of the Farallon–Aluk Spreading Ridge and Its Impact on Subduction Mechanics and Andean Arc Magmatism: Insights From Edited by: Marina Manea, Geochemical and Seismic National Autonomous University of Mexico, Mexico Tomographic Data Reviewed by: 1,2 1,2 1,2 1,2 Luca Ferrari, Sofía B. Iannelli *, Lucía Fernández Paz , Vanesa D. Litvak , Guido Gianni , Geosciences Center, National Lucas M. Fennell1,2, Javiera González3, Friedrich Lucassen4, Simone Kasemann4, Autonomous University of Mexico, Verónica Oliveros3 and Andrés Folguera1,2 Mexico 1 2 Jiashun Hu, Departamento de Ciencias Geológicas, Universidad de Buenos Aires, Buenos Aires, Argentina, Instituto de Estudios 3 California Institute of Technology, Andinos ‘Don Pablo Groeber’, CONICET- Universidad de Buenos Aires, Buenos Aires, Argentina, Departamento 4 United States de Ciencias de la Tierra, Universidad de Concepción, Concepción, Chile, MARUM - Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany *Correspondence: Sofía B. Iannelli sofi[email protected] Since the initial proposal of the past existence of a southward-directed mid-ocean ridge–subduction interaction in the Andes during Late Cretaceous–Paleogene times, Specialty section: This article was submitted to several studies have been devoted to uncover the tectonomagmatic evidence of this Structural Geology and Tectonics, process. The collision of a spreading ridge against a subduction margin provokes a section of the journal important tectonomagmatic changes, including, between them, variations in arc-related Frontiers in Earth Science magmatic activity and in the plate-margin stress regime.
    [Show full text]
  • And Ordovician (Sardic) Felsic Magmatic Events in South-Western Europe: Underplating of Hot Mafic Magmas Linked to the Opening of the Rheic Ocean
    Solid Earth, 11, 2377–2409, 2020 https://doi.org/10.5194/se-11-2377-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Comparative geochemical study on Furongian–earliest Ordovician (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe: underplating of hot mafic magmas linked to the opening of the Rheic Ocean J. Javier Álvaro1, Teresa Sánchez-García2, Claudia Puddu3, Josep Maria Casas4, Alejandro Díez-Montes5, Montserrat Liesa6, and Giacomo Oggiano7 1Instituto de Geociencias (CSIC-UCM), Dr. Severo Ochoa 7, 28040 Madrid, Spain 2Instituto Geológico y Minero de España, Ríos Rosas 23, 28003 Madrid, Spain 3Dpt. Ciencias de la Tierra, Universidad de Zaragoza, 50009 Zaragoza, Spain 4Dpt. de Dinàmica de la Terra i de l’Oceà, Universitat de Barcelona, Martí Franquès s/n, 08028 Barcelona, Spain 5Instituto Geológico y Minero de España, Plaza de la Constitución 1, 37001 Salamanca, Spain 6Dpt. de Mineralogia, Petrologia i Geologia aplicada, Universitat de Barcelona, Martí Franquès s/n, 08028 Barcelona, Spain 7Dipartimento di Scienze della Natura e del Territorio, 07100 Sassari, Italy Correspondence: J. Javier Álvaro ([email protected]) Received: 1 April 2020 – Discussion started: 20 April 2020 Revised: 14 October 2020 – Accepted: 19 October 2020 – Published: 11 December 2020 Abstract. A geochemical comparison of early Palaeo- neither metamorphism nor penetrative deformation; on the zoic felsic magmatic episodes throughout the south- contrary, their unconformities are associated with foliation- western European margin of Gondwana is made and in- free open folds subsequently affected by the Variscan defor- cludes (i) Furongian–Early Ordovician (Toledanian) activ- mation.
    [Show full text]
  • Masterarbeit
    MASTERARBEIT Titel der Masterarbeit Late Cretaceous Volcaniclastic Rocks in the Pontides (NW Turkey) verfasst von Katharina Böhm BSc angestrebter akademischer Grad Master of Science (M.Sc.) Wien, 2015 Studienkennzahl lt. Studienblatt: A 066 815 Studienrichtung lt. Studienblatt: Erdwissenschaften Betreuerin / Betreuer: Ao. Univ.-Prof. Dr. Michael Wagreich Declaration ”I hereby declare that this master’s thesis was authored by myself independently, without use of other sources than indicated. I have explicitly cited all material which has been quoted either literally or by content from the used sources. Further this work was neither submitted in Austria nor abroad for any degree or examination.” Contents Declaration2 1. Introduction8 1.1. Project.................................. 9 1.1.1. Goals............................... 9 1.2. Geographical setting.......................... 10 1.3. Geological setting............................ 12 1.3.1. The Pontides........................... 14 1.3.2. The Pontides in the Cretaceous................ 18 1.3.3. Correlation with relative ages.................. 24 2. Nomenclature 28 3. Methods 29 3.1. ICP-ES and ICP-MS........................... 29 3.2. PXRD.................................. 29 3.3. Heavy mineral extraction........................ 30 4. Results 31 4.1. Mineralogy................................ 31 4.1.1. Powder X-Ray diffraction.................... 31 4.1.2. Thin sections.......................... 33 4.1.3. Mineral Extraction: Dating of minerals............. 34 4.2. Geochemistry.............................. 36 5. Interpretation of the geochemical results 37 5.1. Mobility of elements........................... 37 5.2. Alteration of minerals.......................... 39 5.3. Determining the rock type........................ 41 3 5.4. Discriminating volcanic series..................... 48 5.5. Revealing the tectonic setting...................... 52 5.6. Plotting geochemical element patterns................. 60 5.7. Summary of the geochemical classification.............. 62 6.
    [Show full text]
  • The Cretaceous Igneous Rocks in Southeastern Guangxi and Their Implication for Tectonic Environment in Southwestern South China Block
    Open Geosciences 2020; 12: 518–531 Research Article Yang Liu, Nianqiao Fang*, Menglin Qiang, Lei Jia, and Chaojie Song The Cretaceous igneous rocks in southeastern Guangxi and their implication for tectonic environment in southwestern South China Block https://doi.org/10.1515/geo-2020-0160 Keywords: high-magnesian andesites 1, I-type granite 2, received January 9, 2020; accepted May 13, 2020 clastoporphyritic lava 3, Neo-Tethyan Subduction 4, Abstract: Southeastern Guangxi is located in the south- Southwestern South China Block 5 western South China Block and to the northwest of the South China Sea (SCS), with abundant records of the Cretaceous magmatism. A detailed study of igneous rocks will contribute to a better understanding of the late 1 Introduction Mesozoic tectonic environment. Zircon U–Pb dating yields ages of 93.37 ± 0.43 Ma for Yulin andesites and 107.6 ± South China Block lies between the Tethyan tectonic belt fi [ ] 1.2 Ma for Luchuan granites. Yulin andesites are hornblende and Paci c tectonic belt 1 .Itisacrucialperiodfor andesites, of which w(MgO) is between 7.72% and 8.42%, magmatic rocks and mineralization in southwestern South and Mg# is between 66.7 and 68.0, belonging to high China Block in Cretaceous, especially in the range of – [ ] magnesian andesites (HMAs) from peridotite sources. 100 90 Ma 2 . These magmatic rocks are a key to study Luchuan granites are medium- to fine-grained monzogra- the tectonic evolution in this region. More research has - nites. Monzogranites and clastoporphyritic lava are high-K been done by predecessors, including Kunlunguan bath calc-alkaline series and metaluminum to weakly peralumi- olith, Dali rock mass and Dachang dike group with nous series, which belong to the I-type granites.
    [Show full text]
  • Ammonoid Genus Argentiniceras from Kachchh (India) and Its Relevance to J Urassic/Cretaceous Boundary
    Newsl. Stratigr. Berlin · Stuttgart, 28. 3. 1991 Discovery of Lower Berriasian (Lower Creataceous) Ammonoid Genus Argentiniceras from Kachchh (India) and its Relevance to J urassic/Cretaceous Boundary by jAr KRISHNA with 1 plate, 2 figures and 4 tables Abstract. The ammonoid genus Argentiniceras SPATH 1924 (= Andesites GERTH 1925) is described and illustrated from Umia Member (Green Oolitic bed) North of Lakhapar, Western Kachchh, Gujarat. The genus Argentiniceras is a Lower Berriasian form known so far only from South America (Colombia, Peru, Chile, Argentina) and Antarctica (Alexander Island) i.e. the Andean marine fauna! province (also known as S. American or SE Pacific) and it is considered a good marker of Lower Berriasian. This is the first report of this genus from anywhere outside the Andean Province. Its discovery in Jurassic/Cretaceous passage beds helps more precise and better delineation of the Jurassic/Cretaceous boundary in Kachchh. Further, together with the earlier reports of some South American Upper Tithonian genera from India, the present discovery also strengthens the evidence of direct marine connection between Andean and Indo-East-African marine fauna! provinces near the Jurassic/Cretaceous boundary. Resume. Le genre Argentiniceras SPATH 1924 (= Andesites GERTH 1925) decouvert clans le membre Umia (couche oolithique verte) au Nord de Lakhapar (Gujarat, Ouest de l'Inde) est decrit et illustre. D'age Berriasien inferieur, il etait connu jusqu'a present uniquement du Sud de l'Amerique (Colombie, Perou, Chili, Argentine) et de l'Antarctique (Ile Alexander), c'est-a-dire de la province andine. Le genre est considere comme un bon marqueur stratigraphique du Berriasien inferieur et pour la premiere fois est cite en-dehors de la province andine, clans les couches de passage Jurassique-Cretace.
    [Show full text]
  • New Age Constraints for Early Paleogene Strata of Central Patagonia
    New age constraints for early Paleogene strata of central Patagonia, Argentina New age constraints for early Paleogene strata of central Patagonia, Argentina: Implications for the timing of South American Land Mammal Ages J. Marcelo Krause1,2,†, William C. Clyde3, Mauricio Ibañez-Mejía4,5, Mark D. Schmitz6, Timothy Barnum3, Eduardo S. Bellosi7, and Peter Wilf8 1CONICET–Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, 9100, Trelew, Argentina 2Departamento de Geología, Universidad Nacional de la Patagonia San Juan Bosco, Ruta Provincial 1 s/n, 9000, Comodoro Rivadavia, Chubut, Argentina 3Department of Earth Sciences, University of New Hampshire, 56 College Road, Durham, New Hampshire 03824, USA 4Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 5Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627, USA 6Department of Geosciences, Boise State University, 1910 University Drive, Boise, Idaho 83725, USA 7CONICET–Museo Argentino de Ciencias Naturales, Ángel Gallardo 470, 1405 Buenos Aires, Argentina 8Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA ABSTRACT in our new magnetostratigraphic framework, rec ords of regional biotic responses to global we correlate the Peñas Coloradas Formation climatic events (e.g., Raigemborn et al., 2009, The Río Chico Group in the San Jorge to chrons C27n-26r (ca. 62.5 to ca. 61.6 Ma; 2014; Bellosi and González, 2010; Krause et al., Basin of central Patagonia (Argentina) pre- late Danian) and the section from the middle 2010; Dunn et al., 2015; Kohn et al., 2015; serves some of South America’s most signif- Las Flores to the uppermost Koluel-Kaike to Selkin et al., 2015).
    [Show full text]
  • (Turkey) Based on New Nannoplankton Age Determinations in the Eastern Pontides: Geodynamic Implications Jean-Claude Hippolyte, C
    Stratigraphic comparisons along the Pontides (Turkey) based on new nannoplankton age determinations in the Eastern Pontides: geodynamic implications Jean-Claude Hippolyte, C. Müller, E. Sangu, N. Kaymakci To cite this version: Jean-Claude Hippolyte, C. Müller, E. Sangu, N. Kaymakci. Stratigraphic comparisons along the Pontides (Turkey) based on new nannoplankton age determinations in the Eastern Pontides: geo- dynamic implications. The Geological Society, London, Special Publications, Geological Society of London, 2017, Tectonic Evolution of the Eastern Black Sea and Caucasus., 428 (1), pp.323 - 358. 10.1144/SP428.9. hal-01708711 HAL Id: hal-01708711 https://hal.archives-ouvertes.fr/hal-01708711 Submitted on 14 Feb 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Copyright 1 Stratigraphic comparisons along the Pontides (Turkey) based on new nannoplankton age determinations in the Eastern Pontides: geodynamic implications J-C. Hippolyte, C. Müller, E. Sangu and N. Kaymakci Hippolyte Jean-Claude * UMR-6635 CNRS - Universite Aix-Marseille III BP 80, Europole Mediterraneen de l'Arbois 13545 Aix en Provence Cedex 4, FRANCE Tel. +33 4 42 97 17 70, Fax. +33 4 42 97 16 58, e-mail: [email protected] Müller Carla PL-66-431b Santok, Ludzislawice 36, Poland Sangu Ercan Kocaeli University, Department of Geological Engineering, 41100 Kocaeli, Turkey Kaymakci Nuretdın Middle East Technical University, Department of Geological Engineering, 06800- Ankara Turkey.
    [Show full text]
  • Petrogenesis of the Early Cretaceous Adakite-Like Porphyries And
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/257553072 Petrogenesis of the Early Cretaceous adakite- like porphyries and associated basaltic andesites in the eastern Jiangnan orogen... Article in Journal of Asian Earth Sciences · November 2012 DOI: 10.1016/j.jseaes.2012.10.017 CITATIONS READS 13 97 5 authors, including: Xiao-Lei Wang Ming Tang Nanjing University Rice University 49 PUBLICATIONS 1,467 CITATIONS 13 PUBLICATIONS 168 CITATIONS SEE PROFILE SEE PROFILE R. M. Gaschnig University of Massachusetts Lowell 34 PUBLICATIONS 293 CITATIONS SEE PROFILE All content following this page was uploaded by Ming Tang on 20 February 2014. The user has requested enhancement of the downloaded file. Journal of Asian Earth Sciences 61 (2012) 243–256 Contents lists available at SciVerse ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes Petrogenesis of the Early Cretaceous adakite-like porphyries and associated basaltic andesites in the eastern Jiangnan orogen, southern China ⇑ Xiao-Lei Wang a, , Xu-Jie Shu a, Xisheng Xu a, Ming Tang a, Richard Gaschnig b a State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, PR China b Department of Geology, University of Maryland, MD 20742, USA article info abstract Article history: Early Cretaceous quartz porphyries are associated with mantle-derived mafic rocks (basaltic andesites) in Received 4 October 2011 the eastern segment of the Neoproterozoic Jiangnan orogen, southern China. Zircons from two quartz Received in revised form 10 October 2012 porphyries yield identical U–Pb ages at 142 ± 1 Ma by the LA–ICP–MS method.
    [Show full text]
  • Mineral Deposits of Lake Valley Quadrangle, Grant, Luna, and Sierra Counties, New Mexico
    BULLETIN 37 Geology and Mineral Deposits of Lake Valley Quadrangle, Grant, Luna, and Sierra Counties, New Mexico BY HENRY L. JICHA, JR. Stratigraphy and structure of sedimentary and volcanic rocks and descriptions of mining districts 1954 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Eugene Callaghan, Director THE REGENTS MEMBERS Ex OFFICIO The Honorable Edwin L. Mechem ............ Governor of New Mexico Tom Wiley .......................... Superintendent of Public Instruction APPOINTED MEMBERS Robert W. Botts ........................................................... Albuquerque Holm O. Bursum, Jr. ................................................................... Socorro Thomas M. Cramer ............................................................ Carlsbad Frank C. DiLuzio ............................................................ Los Alamos A. A. Kemnitz .............................................................................. Hobbs FRONTISPIECE VIEW OF LAKE VALLEY (circa 1905). TOWN OF LAKE VALLEY IN THE LAST DAYS OF THE SILVER BOOM. COMPARE WITH PLATE 2-A. Picture by Henry Schmidt, from the collection of Ray- mond Schmidt. Contents Page ABSTRACT ........................................................... 1 INTRODUCTION ............................................................. 2 Geography and physiography ......................................................
    [Show full text]
  • 070256B0.Pdf
    NATURE useful in districts remote from medical aid. Courses of Messrs. Slipher and Lalllpland, un the visibility of fine elementary lectures are also given, both at the college and lines a t various distances. The experiments were exactly similar to those previously carried out with a fine wire of at the United Service Institution, open to all who may 0.7 inch diameter, except that a fine blue line 0.7 inch in expect to reside or travel in the tropics. The" Year Book" width, drawn on a white disc 8 feet in diameter, was contains details of the college and its curriculum, and useful observed at the same time as the wire.· At a distance of directions for the preservation of health in the tropics. 1450 feet, when the angular width of the disc was 19' and that of the lines was 0".86, the wire was certainly IN the short notice of Mr. Cecil Hawkins's" Elementary seen, but a fi ctitious line was seen accompanying what was Geometry" in NATURE of June 30 (p. 193), reference was supposed to be the real one. The general results of the experiments indicated that the made to the absence of numerical answers in the copy wire was more generaiiv visible than the line, although at supplied. Mr. Hawkins asks us to state that the book is distances less than 400 feet the latter was the more readily also supplied with answers if desired. seen. MESSRS. T . C. AND E. C. JACK, of Edinburgh, have sub­ VARIABILITY OF MI I\ OR PLA:'(ETs.-Observa tions of the mitted for ollr inspection four of the pl ates of a stereoscopic magnitudes of the minor planets Iris, Ceres, and Pallas, m ade by H err J.
    [Show full text]
  • Geochronology and Geochemistry of the Mesozoic Volcanic Rocks In
    Available online at www.sciencedirect.com Lithos 102 (2008) 88–117 www.elsevier.com/locate/lithos Geochronology and geochemistry of the Mesozoic volcanic rocks in Western Liaoning: Implications for lithospheric thinning of the North China Craton ⁎ Wei Yang, Shuguang Li CAS Key laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China Received 17 October 2006; accepted 24 September 2007 Available online 11 October 2007 Abstract Determining the age and petrogenesis of the voluminous Mesozoic magmatic rocks from the North China Craton (NCC) provides critical data for deducing the process and timing of lithospheric thinning. Four Mesozoic magmatic events in the northeast of the craton (Western Liaoning) are delineated by Ar–Ar and U–Pb zircon dating, i.e. the Xinglonggou Formation (177 Ma), the Lanqi Formation (166–153 Ma), the Yixian Formation (126–120 Ma), and the Zhanglaogongtun Formation (∼106 Ma), respectively. The Xinglonggou lavas are high-Mg# adakites with arc-like Sr–Nd–Pb isotopic compositions, suggesting that they originated from the subducted Palaeoasian oceanic crust. The typical “continental” geochemical signatures of the Lanqi basalts and basaltic andesites as well as their 87 86 low ɛNd(t), moderate Sr/ Sri, and extremely unradiogenic Pb isotopes indicate significant involvement of lower crust materials in their magma. These features, coupled with the low Mg, Ni, and Cr contents may suggest significant olivine fractionation and a magma underplating event, which caused the partial melting of the low-middle crust to produce the voluminous low-Mg andesites and acidic volcanic rocks overlying the Lanqi basalts.
    [Show full text]
  • Environmental Effect and Genetic Influence: a Regional Cancer
    Environ Geol (2008) 54:391–409 DOI 10.1007/s00254-007-0826-3 ORIGINAL ARTICLE Environmental effect and genetic influence: a regional cancer predisposition survey in the Zonguldak region of Northwest Turkey Selahattin Kadir Æ A. Piril O¨ nen-Hall Æ S. Nihal Aydin Æ Cengiz Yakicier Æ Nurten Akarsu Æ Murat Tuncer Received: 20 December 2006 / Accepted: 21 May 2007 / Published online: 28 June 2007 Ó Springer-Verlag 2007 Abstract The Cretaceous-Eocene volcano-sedimentary and kaolinite, and the suborientation of feldspar-edged, units of the Zonguldak region of the western Black Sea subparallel kaolinite plates to fracture axes may exhibit an consist of subalkaline andesite and tuff, and sandstone authigenic smectite or kaolinite. Increased alteration de- dominated by smectite, kaolinite, accessory chlorite, illite, gree upward in which Al, Fe, and Ti are gained, and Si, Na, mordenite, and analcime associated with feldspar, quartz, K, and Ca are depleted, is due to the alteration following opal-CT, amphibole, and calcite. Kaolinization, chloriti- possible diagenesis and hydrothermal activities. Micro- zation, sericitization, albitization, Fe–Ti-oxidation, and the morphologically, fibrous mordenite in the altered units and presence of zeolite, epidote, and illite in andesitic rocks the presence of needle-type chrysotile in the residential and tuffaceous materials developed as a result of the deg- buildings in which cancer cases lived were detected. In radation of a glass shards matrix, enclosed feldspar, and addition, the segregation pattern of cancer susceptibility in clinopyroxene-type phenocrysts, due to alteration pro- the region strongly suggested an environmental effect and a cesses. The association of feldspar and glass with smectite genetic influence on the increased cancer incidence in the region.
    [Show full text]