University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 2000 Geochemistry and geochronology of I-type granitoid rocks in the northeastern central Iran plate Abolfazl Soltani University of Wollongong Recommended Citation Soltani, Abolfazl, Geochemistry and geochronology of I-type granitoid rocks in the northeastern central Iran plate, Doctor of Philosophy thesis, School of Geosciences, University of Wollongong, 2000. http://ro.uow.edu.au/theses/1970 Research Online is the open access institutional repository for the University of Wollongong. For further information contact Manager Repository Services: [email protected]. GEOCHEMISTRY AND GEOCHRONOLOGY OF I-TYPE GRANITOID ROCKS IN THE NORTHEASTERN CENTRAL IRAN PLATE A thesis submitted in fulfilment of the requirements for the award of the degree of DOCTOR OF PHILOSOPHY from UNIVERSITY OF WOLLONGONG, by ABOLFAZL SOLTANI BSc Mashhad, MSc (Hons) Wollongong SCHOOL OF GEOSCIENCES 2000 I dedicate this thesis to my wife Zahra and my children Somayeh and Farzad This work has not been submitted for a higher degree at any other university or institution and, unless otherwise acknowledged, is the author's original research. Abolfazl Soltani 31/03/2000 i ABSTRACT The Taknar and Sabzevar Zones in the northeastern Central Iran Plate (CIP) encompass a large variety of volcanic and plutonic rocks. The plutonic rocks are mainly I-type granitoids, ranging in age from Late Jurassic to Middle-Late Eocene. Among the plutonic rocks, granodiorite and granite are the most abundant rock types. This dissertation summarises the results of a detailed petrographic, geochemical and isotopic study of granitoid rocks from three areas of northeastern CEP, comprising the Kashmar and Bornavard granitoids in the Taknar Zoiie, and the Kuh Mish intrusions in the Sabzevar Zone. The Kashmar and Bornavard granitoids are generally high in Na20, total Fe as Fe203, Mn, Ba, Zr and Sr, and low in Ti02, P205, Rb, Nb, Cr, Ni and Sn contents. On Harker plots, they show regular trends for most major and trace element concentrations. They are characterised by steep negative slopes for LREE, flat to slightly negative gradients for HREE and moderate to strongly negative anomalies for Eu, features attributed to fractional crystallisation. However, in the Kashmar granitoid, restite separation and fractional crystallisation may be responsible for compositional variations. Mineralogical and chemical data suggest that the Kashmar and Bornavard granitoids have formed from low temperature I-type magmas and can be assigned to a 'simple suite' of White et al. (2000). In the Kashmar granitoid, initial 87Sr/86Sr (0.70471-0.70569) and 6Nd (-0.70 to -1.86) values are low and exhibit a restricted range, indicating a homogeneous lower crustal protolith. In the Bornavard granitoid, however, 87 86 initial Sr/ Sr (0.70757-0.75008) and eNd values (-1.41 to -5.20) exhibit a large range, suggesting that magmas were extensively contaminated with older continental crust or they were derived from partial melting of older felsic rocks of the continental crust. ii The Kuh Mish intrusions are compositionally diverse, ranging from gabbro to quartz monzodiorite, but are dominated by granodiorite. They have low abundances of alkalis, LFSE, HFSE and LREE relative to the Kashmar and Bornavard granitoids. They are also the most isotopically primitive plutonic rocks in northeastern CJP, typically having initial (at 87 86 42.8 Ma) Sr/ Sr of 0.70386-0.70475 and sNd values of +8.02 to +6.30 that indicate a mantle source. In these aspects, they are similar to the tonalitic association in the American Cordillera and, in particular, to the western Peninsular Ranges Batholith. The granitoid rocks of the northeastern CJJP show characteristics of magmas that originated in a subduction-related environment. The Rb/Sr ages of biotite-whole rock pairs from granitoids of northeastern CIP are consistent with the timing of subduction of the Neo- Tethys Oceanic crust beneath the CIP. In particular, Sr-Nd isotopic data show that in the northeastern CIP, Middle-Late Eocene granitoids are isotopically less evolved or have primitive features compared with Late Jurassic/Early Cretaceous granitoids. It seems that voluminous injection of basaltic and andesitic magmas derived from subduction of the oceanic crust resulted in a complete change in the genesis of magmas in the northeastern CIP. Using tectonic discrimination diagrams, the Kashmar and Bornavard granitoids typically plot in the 'volcanic arc and syn-collisional' granite field. However, the Kuh Mish intrusions are strongly depleted in Rb, Nb and Y contents suggesting that they may have emplaced in an island arc environment. iii ACKNOWLEDGEMENTS This thesis could not have completed without the help and assistance of many people who contributed their time, enthusiasm and support towards the intellectual and practical understanding of granitoids. My supervisor Dr Paul F. Carr is especially thanked for giving me the opportunity to complete a doctoral study in one of the most scenic field sites in the world. He also provided valuable insight and fruitful discussion through all phases and aspects of the present study. His patience, during my field and laboratory work and his critical reading of chapter drafts, is hereby acknowledged. Special thanks are due to my family for their constant support during my studies, often under difficult and trying circumstances, and for their love and faith in me. The various Heads of the Department of Geology/School of Geosciences (A/Prof. Tony J. Wright, A/Prof. Brian G. Jones, Prof. Allan R. Chivas and A/Prof. Ted Bryant) are thanked for making available the facilities of the Department/School. I am indebted to A/Prof. Brian G. Jones and Mr Aivars M. Depers for encouragement and reading of many drafts of my thesis chapters and bringing to my attention errors and omissions, all beyond the call of duty. Prof. Bruce W. Chappell from the Australian National University is sincerely thanked for giving me his advice and forwarding copies of his publications. I would like to thank Mr. David Carrie for his help in the preparation of polished thin sections. Thanks are also due to Dr Norm Pearson from Macquarie University for his assistance with the electron microprobe iv analyses. I wish to express my sincere appreciation to Dr Masoud Doroudian and Mr Ali A. Shojaei for proof reading my thesis references and linking these with the text. Mr Ali A. Faramarziah is thanked for help in final printing of the thesis. The field aspects of the present study occupied a large proportion of my time and numerous people need to be thanked for their assistance, not only in active muscle work, but also camaraderie, often during inclement weather. I am indebted to Mr Mahmoud Refabi for his continued and enthusiastic help with all aspects of field sampling, as well as logistics. I am grateful to the Director of the Geological Survey of Mashhad, Mr Jafar Taheri for allowing me to use unpublished data from the Kashmar 1:100 000 Geological Sheet. He also provided assistance and informative discussions during field trips. The Governor's Office of Kashmar provided suitable vehicles for field trips. I am grateful to fellow postgraduate students of the School of Geosciences, particularly Musa Arhoma, Jenny Atchison, Sue Murray, Mark Dickson, Alex Golab, Daniel Palamara and Simon Clarke for providing amusement and social relief as well as different academic insights into research, both relevant and irrelevant to granitoids. This work was supported by a scholarship from the Ministry of Culture and Higher Education of the Islamic Republic of Iran. Without this assistance, this study would not have been possible. V TABLE OF CONTENTS ABSTRACT i ACKNOWLEDGEMENTS iii TABLE OF CONTENTS v LIST Of FIGURES x LIST OF TABLES xvi CHAPTER 1 INTRODUCTION 1.1 INTRODUCTION 1 1.2 GENERAL GEOLOGY 2 1.3 AIMS 4 1.4 PREVIOUS WORK 4 1.5 IGNEOUS ROCK NOMENCLATURE 5 1.6 LAYOUT OF THE THESIS 5 CHAPTER 2 REGIONAL GEOLOGY OF IRANIAN GRANITOIDS 2.1 INTRODUCTION 7 2.2 CENTRAL IRAN PLATE (CIP) 8 2.3 SANANDAJ-SIRJAN MET AMORPHIC ZONE (S-SMZ) 10 2.4 URUMIEH-DOKHTAR VOLCANIC BELT (U-DVB) 12 2.5 GEOLOGICAL SETTING OF IRANIAN GRANITOIDS 12 2.5.1 REGIONAL-AUREOLE GRANITOIDS 12 2.5.1.1 Chapedony Complex 13 2.5.1.2 Doran Granite 13 2.5.2 CONTACT-AUREOLE GRANITOIDS 14 2.5.2.1 Mashhad Granite 14 2.5.2.2 Shahkuh Granite 16 2.5.2.3 Shirkuh Batholith 17 2.5.2.4 Muteh Granite 17 2.5.2.5 Hamadan Batholith 17 VI 2.5.3 SUB VOLCANIC GRANITOIDS 19 2.5.3.1 Natanz Intrusive Complex 19 2.5.3.2 Karkas and Jebal-e-Barez Intrusions 20 2.5.4 SUMMARY 20 CHAPTER 3 GEOLOGICAL SETTING AND GEOCHRONOLOGY 3.1 GEOLOGICAL SETTING 23 3.1.1 TAKNAR ZONE 23 3.1.2 SABZEVAR ZONE 24 3.2 MAJOR FAULT SYSTEMS 25 3.2.1 DORUNEH FAULT 25 3.2.2 RIVASH FAULT 26 3.3 GEOCHRONOLOGY 26 3.3.1 KASHMAR GRANITOID 26 3.3.1.1 Rb/Sr Age Dating 28 3.3.1.2 IsotopicData 28 3.3.2 BORNAVARD GRANITOID 31 3.3.2.1 IsotopicData 32 3.3.2.2 Age Discussion on the Bornavard Granitoid 35 CHAPTER 4 PETROGRAPHY AND MINERAL CHEMISTRY 4.1 PETROGRAPHY OF KASHMAR GRANITOID 38 4.1.1 TONALITE 38 4.1.2 GRANODIORITE 39 4.1.3 GRANITE 39 4.1.4 ALKALI FELDSPAR GRANITE 40 4.2 MINERAL CHEMISTRY OF KASHMAR GRANITOID 41 4.2.1 PLAGIOCLASE 41 4.2.2 AMPHD30LE 43 4.2.3 BIOTITE 47 4.2.4 Fe-Ti OXIDES 52 4.2.5 K-FELDSPAR 54 4.2.6 QUARTZ 56.