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Discovery of the Indosinian aluminum A-type granite in Zhejiang Province and its geological significance

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Science China Earth Sciences 2012年第1期55卷 13-25页

作者： LI WanYou MA ChangQian LIU YuanYuan paul t.robinson Faculty of Earth Sciences China University of GeosciencesWuhan 430074China 706 Geological team Guangdong Provincial Bureau of GeologyShaoguan 512030China State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan 430074China

Zircon LA-ICP-MS U-Pb dating of the Jingju syenogranites in the southwestern part of Zhejiang Province shows that these rocks were crystallized in the Late triassic at 215±2 Ma, rather than in the Cretaceous as previously proposed. the Jingju sy- enogranites are characterized by relatively high K2O and FeO＊, and low MgO. they have high concentrations of large ion lithophile elements （LIL） and LREE, such as K, th, La, and Ce, but are depleted in high field strength elements （HFSE） such as Nb, ta, and ti. their 104Ga/A1 ratios and （Zr＋Nb＋Ce＋Y） contents are also high. these characteristics are similar to those of A-type granites. the syenogranites have high Isr （0.7179-0.7203）, low eNa（t）（from --14.2 to --13.2）, and relatively old t2DM ages, similar to those of the ancient metamorphic basement in the Cathaysia Block. It is suggested that the Jingju syenogranites were formed by partial melting of the Cathaysia basement rocks during tectonic extension. this identification of Indosinian A-type granite in Jingju has significant implications for understanding the early Mesozoic tectonic evolution of South China.

关键词： Indosinian chronology geochemistry A-type granite Zhejiang Province

Platinum-group Mineral(PGM) and Base-metal Sulphide(BMS) Inclusions in Chromitites of the Zedang Ophiolite, Southern tibet, China and their Petrogenetic Significance

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Acta Geologica Sinica(English Edition) 2016年第3期90卷 900-912页

作者： GUO Guolin YANG Jingsui paul t.robinson LIU Xiaodong XU Xiangzhen XIONG Fahui State Key Laboratory Breeding Base of Nuclear Resources and Environment East China University of Technology CARMA State Key Laboratory of Continental Tectonics and Dynamics Institute of Geology Chinese Academy of Geological Sciences School of earth sciences East China University of Technology

Voluminous platinum-group mineral （PGM） inclusions including erlichmanite （Os,Ru）S2, laurite （Ru,Os）S2, and irarsite （Ir, Os,Ru,Rh）AsS, as well as native osmium Os（Ir） and inclusions of base metal sulphides （BMS）, including millerite （NiS）, heazlewoodite （NiaS2）, covellite （CuS） and digenite （Cu3S2）, accompanied by native iron, have been identified in chromitites of the Zedang ophiolite, tibet. the PGMs occur as both inclusions in magnesiochromite grains and as small interstitial granules between them; most are less than 10 ~m in size and vary in shape from euhedral to anhedral. they occur either as single or composite （biphase or polyphase） grains composed solely of PGM, or PGM associated with silicate grains. Os-, Ir-, and Ru-rich PGMs are the common species and Pt-, Pd-, and Rh-rich varieties have not been identified. Sulfur fugacity and temperature appear to be the main factors that controlled the PGE mineralogy during crystallization of the host chromitite in the upper mantle. If the activity of chalcogenides （such as S, and As） is low, PGE clusters will remain suspended in the silicate melt until they can coalesce to form alloys. Under appropriate conditions of fS2 and fO2, PGE alloys might react with the melt to form sulfides-sulfarsenides. thus, we suggest that the Os, Ir and Ru metallic clusters and alloys in the Zedang chromitites crystallized first under high temperature and low fS2, followed by crystallization of sulphides of the laurite-erlichmanite, solid-solution series as the magma cooled and fS2 increased. the abundance of primary BMS in the chromitites suggests that fS2 reached relatively high values during the final stages of magnesiochromite crystallization. the diversity of the PGE minerals, in combination with differences in the petrological characteristics of the magnesiochromites, suggest different degrees of partial melting, perhaps at different depths in the mantle. the estimated parental magma composition suggests formation in a suprasubdu

关键词： chromite ophiolite petrogenetic PGM Zedang

Geochemistry and zircon SHRIMP U-Pb dating of granitoids from the west segment of the North Qaidam

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Science China Earth Sciences 2009年第11期52卷 1771-1790页

作者： Joseph L.WOODEN paul t.robinson Frank K.MAZDAB Chris MAttINSON Department of Earth and Environmental Sciences Stanford University Department of Earth Sciences Dalhousie University

Granitoid intrusives such as Saishitenshan, tuanyushan, Aolaohe and Sanchagou occur widely in the western segment of North Qaidam. All these bodies trend NW, roughly parallel to the regional structure. Zircon SHRIMP dating for these granites show that they range in age from Ordovician to Permian; 465.4±3.5 Ma for Saishitenshan, 469.7±4.6 Ma and 443.5±3.6 Ma for tuanyushan, 372.1±2.6 Ma for Aolaohe, and 271.2±1.5 Ma and 259.9±1.2 Ma for Sanchagou. Both the tuanyshan and Aolaohe plutons record two distinct intrusive events. Geochemically, the early Paleozoic granites have an island arc or active continental margin affinity, and their protolith may have been Mesoproterozoic oceanic crust derived from depleted mantle. the protolith of the late Paleozoic granites may have been Mesoproterozoic lower crust from the root of an island arc with the magmas reflecting a mixture of mantle and crustal material.

关键词： granitoid zircon SHRIMP U-Pb dating North Qaidam

Geochronology and Geochemistry of the Middle Proterozoic Aoyougou Ophiolite in the North Qilian Mountains,Northwestern China

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Acta Geologica Sinica(English Edition) 2001年第1期75卷 41-50页

作者： ZHANG Zhaochong MAO Jingwen ZUO Guochao YANG Jianmin paul t.robinson Institute of Geology Chinese Academy of Geological SciencesBaiwanzhuang Road 26Beijing 100037China Institute of Mineral Deposits Chinese Academy of Geological SciencesBaiwanzhuang Road 26Beijing 100037China Institute of Geology Gansu Bureau of Geology and Mineral ResourcesLanzhou 730000China Centre For Marine Geology Dalhousie UniversityHalifaxNova ScotiaB3H 3J5Canada

the Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. the diabases and basalts show light rare-earth element enrichment and have relatively high tiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. they are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr-spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proterozoic produced a trench-arc-basin system, which is preserved in the North Qilian Mountains.

关键词： Proterozoic ophiolite geochronology geochemistry North Qilian Mountains

Origin of Listwanite in the Luobusa Ophiolite,tibet,Implications for Chromite Stability in Hydrothermal Systems

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Acta Geologica Sinica(English Edition) 2015年第2期89卷 402-417页

作者： ZHANG Lan YANG Jingsui paul t.robinson XIONG Fahui CHEN Yanhong LAI Shengmin CHEN Mei School of the Earth Sciences and Resources China University of Geosciences CARMA State Key Laboratory for Continental Tectonics and DynamicsInstitute of GeologyChinese Academy of Geological Sciences

Listwanite from the Luobusa ophiolite, tibet, forms a narrow, discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mineral transformation processes and the behaviour of major and trace elements during listwanite formation. three alteration zones characterized by distinct mineral components and texture are recognized and, in order of increasing degree of alteration, these are： zonem is rich in serpentine minerals; zonen is rich in talc and carbonates; and zone_Ⅰ is mainly composed of carbonates and quartz. Geochemical data for the three alteration zones show significant modification of some major and trace elements in the protolith, although some oxides show linear correlations with MgO. Gold mineralization is recognized in the Luobusa listwanite and may signify an important target for future mineral exploration. Gold enrichment occurs in both zone_Ⅰ and zone_Ⅱ and is up to 0.91 g/t in one sample from zonei. We show that CO_2-rich hydrothermal fluids can modify both the occurrence and composition of chromite grains, indicating some degree of chromite mobility. Low-Cr anhedral grains are more easily altered than high-Cr varieties. the compositions of chromite and olivine grains in the listwanite suggest a dunite protolith.

关键词： Listwanite mineralogy geochemistry gold mineralization chromite stability

the Discovery of Diamonds in Chromitites of the Hegenshan Ophiolite,Inner Mongolia,China

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Acta Geologica Sinica(English Edition) 2015年第2期89卷 341-350页

作者： HUANG Zhu YANG Jingsui paul t.robinson ZHU Yongwang XIONG Fahui LIU Zhao ZHANG Zhongming XU Wei CARMA State Key Laboratory of Continental Tectonics and DynamicsInstitute of GeologyChinese Academy of Geological Sciences China University of Geosciences Inner Mongolia No.9 Geology Mineral Exploration and Development Institute Institute of Mineral Resources Chinese Academy of Geological Sciences 101 Geological team of Sichuan Bureau of Geology and Mineral Resources

Diamond, moissanite and a variety of other minerals, similar to those reported from ophiolites in tibet and northern Russia, have recently been discovered in chromitites of the Hegenshan ophiolite of the Central Asian Orogenic Belt, north China. the chromitites are small, podiform and vein-like bodies hosted in dunite, clinopyroxene-bearing peridotite, troctolite and gabbro. All of the analysed chromite grains are relatively Al-rich, with Cr^# [100Cr/（Cr＋Al）] of about 47-53. Preliminary studies of mainly disseminated chromitite from ore body No. 3756 have identified more than 30 mineral species in addition to diamond and moissanite. these include oxides （mostly hematite, magnetite, ruffle, anatase, cassiterite, and quartz）, sulfides （pyrite, marcasite and others）, silicates （magnesian olivine, enstatite, augite, diopside, uvarovite, pyrope, orthoclase, zircon, sphene, vesuvianite, chlorite and serpentine） and others （e.g., calcite, monazite, glauberite, iowaite and a range of metallic alloys）. this study demonstrates that diamond, moissanite and other exotic minerals can occur in high-Al, as well as high-Cr chromites, and significantly extends the geographic and age range of known diamond-bearing ophiolites.

关键词： diamond moissanite deep mantle minerals chromitites Hegenshan ophiolite InnerMongolia

Diamond Discovered in High-Al Chromitites of the Sartohay Ophiolite,Xinjiang Province,China

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Acta Geologica Sinica(English Edition) 2015年第2期89卷 332-340页

作者： tIAN Yazhou YANG Jingsui paul t.robinson XIONG Fahui LI Yuan ZHANG Zhongming LIU Zhao LIU Fei NIU Xiaolu CARMA State Key Laboratory for Continental Tectonics and DynamicsInstitute of GeologyChinese Academy of Geological Sciences Institute of Mineral Resources Chinese Academy of Geological Sciences

In recent years diamonds and other exotic minerals have been recovered from mantle peridotites and high-Cr chromitites of a number of ophiolites of different age and different tectonic environments. Here we report a similar collection of minerals from the Sartohay ophiolite of Xinjiang Province, western China, which is characterized by having high-Al chromitites. Several samples of massive podiform chromitite with an aggregate weight of nearly 900 kg yielded diamonds, moissanite and other highly reduced minerals, as well as common crustal minerals. thus far, more than 20 grains each of diamond and moissanite have been recovered from heavy mineral separates of the chromitites. the diamonds are all 100-200 μm in size and range in color from pale yellow to reddish-orange to colorless. Most of the grains are anhedral to subhedral octahedra, commonly with elongate forms exhibiting well-developed striations. they all display characteristic Raman spectra with shifts between 1325 cm^-1 and 1333 cm^-1, mostly 1331.51 cm^-1 or 1326.96 cm^-1. the moissanite grains are light blue to dark blue, broken crystals, 50-150 μm across, commonly occurring as small flakes or fragments. their typical Raman spectra have shifts at 762 cm^-1, 785 cm^-1, and 966 cm^-1. this investigation extends the occurrence of diamonds and moissanite to a Paleozoic ophiolite in the Central Asian Orogenic Belt and demonstrates that these minerals can also occur in high-Al chromitites. We conclude that diamonds and moissanite are likely to be ubiquitous in ophiolitic mantle peridotites and chromitites.

关键词： diamond moissanite high-Al chromitite Sartohay Xinjiang

Early Paleozoic Mafic-Ultramafic Rocks in the East Kunlun: trace Subduction of Proto-tethys

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Acta Geologica Sinica(English Edition) 2016年第S1期90卷 231-233页

作者： MENG Fancong CUI Meihui REN Yufeng paul t.robinson Institute of Geology Chinese Academy of Geological Sciences

the East Kunlun located in the northern margin of the Qinghai-Xizang(tibet)Plateau,is a composite orogenic belt which has underwent multi-stages tectonic evolution(*** and Chen,1987;Jiang et al.,1992;Yang et al.,1996,2009).the East Kunlun orogenic belt(EKOB)is bounded by Altyn tagh Fault in the west and Wenquan Fault in the east,bounded by the south margin of Qaidam

关键词： trace Subduction of Proto-tethys Early Paleozoic Mafic-Ultramafic Rocks in the East Kunlun Pb ppm

A brief review of ophiolites in China

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A brief review of ophiolites in China