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Geochronology and Geochemistry of Ore-related Granitoids in the Giant Gariatong Rb Deposit,Tibet and Implications for Rb Metallogeny in China

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Acta Geologica Sinica(English Edition) 2024年第1期98卷 83-103页

作者： LIN Bin tang juxing tang Pan SUN Yan QI Jing MSANTOSH XIE Jinling DENG Shilin LI Faqiao XIE Fuwei ZHOU Aorigele MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China SinoProbe Laboratory Chinese Academy of Geological SciencesBeijing 100094China The Key Laboratory of the Ministry of Education on Solid Waste Treatment and Recycling School of Environment and ResourceSouthwest University of Science and TechnologyMianyangSichuan 621010China School of Earth Sciences and Resources China University of Geosciences(Beijing)Beijing 100083China Department of Earth Sciences University of AdelaideAdelaide SA-5005Australia Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengdu 610031China Regional Geological Survey Team of the Tibetan Bureau of Geology and Mineral Exploration and Development Lhasa 851400China College of Earth Science and Key Laboratory of Tectonic Controlled Mineralization and Oil Reservoirs Chengdu University of TechnologyChengdu 610059China

Rubidium(Rb)deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites.This study investigates a newly-discovered giant Rb deposit at Gariatong in the Central Lhasa terrane in Tibet.Detailed field studies and logging data revealed that the Rb mineralization mainly occurs in monzogranite and is related to greisenization.LA-ICP-MS U-Pb dating of zircon yielded ages of 19.1±0.2 Ma and 19.0±0.2 Ma for greisenized monzogranite and fresh monzogranite,respectively.The monzogranites are characterized as strongly peraluminous,with high contents of SiO2,Al2O3,K2O and Na2O as well as a high differentiation index.They are enriched in light rare earth and large ion lithophile elements with significant negative Eu anomalies and depleted high fieldstrength elements.Petrological and geochemical features of these ore-related monzogranites suggest that they are highly fractionated S-type granites,derived from remelting of crustal materials in a post-collisional setting.The geochemistry of zircon and apatite points to a low oxygen fugacity of the ore-related monzogranite during the magma’s evolution.The discovery of the Gariatong Rb deposit suggests that the Central Lhasa terrane may be an important region for rare metal mineralization.

关键词： LA-ICP-MS U-Pb dating geochemistry Rb metallogeny Gariatong Tibet

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Mineral Geochemistry of Apatite in the Jiama PorphyrySkarn Deposit,Tibet and its Geological Significance

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Acta Geologica Sinica(English Edition) 2024年第2期98卷 399-415页

作者： YANG Yang tang juxing ZHANG Zebin tang Pan XIE Fuwei RAN Fengqin YANG Zongyao YANG Huaichao BAI Yun SUN Miao QI Jing School of Earth Sciences Chengdu University of TechnologyChengdu 610059China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesCAGSBeijing 100037China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China The Key Laboratory of the Ministry of Education on Solid Waste Treatment and Recycling School of Environment and ResourceSouthwest University of Science and TechnologyMianyangSichuan 621010China Chengdu Surveying Geotechnical Research Institute Co. Ltd.of MCCChengdu 610023China Sichuan Tianfu Mining Investment Co. Ltd.Chengdu 610055China Sichuan Institute of Comprehensive Geological Survey Chengdu 610081China

The Jiama deposit,a significant porphyry-skarn-type copper polymetallic deposit located within the Gangdese metallogenic belt in Tibet,China,exemplifies a typical porphyry metallogenic system.However,the mineral chemistry of its accessory minerals remains under-examined,posing challenges for resource assessment and ore prospecting.Utilizing electron microprobe analysis and LA-ICP-MS analysis,this study investigated the geochemical characteristics of apatite in ore-bearing granite and monzogranite porphyries,as well as granodiorite,quartz diorite,and dark diorite porphyries in the deposit.It also delved into the diagenetic and metallogenic information from these geochemical signatures.Key findings include:(1)The SiO_(2) content,rare earth element(REE)contents,and REE partition coefficients of apatite indicate that the dark diorite porphyry possibly does not share a cogenetic magma source with the other four types of porphyries;(2)the volatile F and Cl contents in apatite,along with their ratio,indicate the Jiama deposit,formed in a collisional setting,demonstrates lower Cl/F ratios in apatite than the same type of deposits formed in a subduction environment;(3)compared to non-ore-bearing rock bodies in other deposits formed in a collisional setting,apatite in the Jiama deposit exhibits lower Ce and Ga contents.This might indicate that rock bodies in the Jiama deposit have higher oxygen fugacity.Nevertheless,the marginal variation in oxygen fugacity between ore-bearing and non-ore-bearing rock bodies within the deposit suggests oxygen fugacity may not serve as the decisive factor in the ore-hosting potential of rock bodies in the Jiama deposit.

关键词： apatite metallogenesis mineral geochemistry porphyry Jiama Tibet

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Texture and Geochemistry of Multi-stage Hydrothermal Scheelite in the Mamupu Cu-Au-Mo(-W)Deposit,Eastern Tibet:Implications for Tungsten Mineralization in the Yulong Belt

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Acta Geologica Sinica(English Edition) 2024年第3期98卷 701-716页

作者： ZHANG Xiaoxu tang juxing LIN Bin WANG Qin HE Liang YAN Gang SHAO Rui WU Qiang DU Qiu ZHAXI Pingcuo Chengdu Center China Geological Survey(Geosciences Innovation Center of Southwest China)Chengdu 610081China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China SinoProbe Laboratory Chinese Academy of Geological SciencesBeijing 100094China Earth Sciences College Chengdu University of TechnologyChengdu 610059China No.6 Geological Party Tibetan Bureau of Geology and Mineral Exploration and DevelopmentLhasa 851400China Tibet Shengyuan Mining Group Co. Ltd.Lhasa 851400China

Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt(YPCB),Tibet.This study reports the results of cathodoluminescence,trace element and Sr isotope analyses of Mamupu scheelite samples,undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore-forming fluids.Three different types of scheelite are identified in the Mamupu deposit:scheelite A(Sch A)mainly occurs in breccias during the prograde stage,scheelite B(Sch B)forms in the chlorite-epidote alteration zone in the retrograde stage,while scheelite C(Sch C)occurs in distal quartz sulfide veins.The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage.Compared with ore-related porphyries,Sch A has a similar REE pattern,but with higher ΣREE,more depleted HREE and slightly lower(^(87)Sr/^(86)Sr)i ratios.These features suggest that Sch A is genetically related to ore-related porphyries,but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition.Sch B shows dark(Sch B-I)and light(Sch B-II)domains under CL imaging.From Sch B-I to Sch B-II,LREEs are gradually depleted,with MREEs being gradually enriched.Sch C has the highest LREE/HREE ratio,which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE-rich minerals,such as diopside and garnet,in the early prograde stage.The Mo content in Sch B and Sch C gradually decreased,indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later,the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity.The extensive interaction of magmatic-hydrothermal fluids and carbonate provides the necessary Ca^(2+)for the precipitation of scheelite in the Mamupu deposit.

关键词： scheelite geochemistry Mamupu Cu deposit Yulong porphyry copper belt eastern Tibet

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Syn-mineralization Uplifting and Exhumation of Porphyry Systems in China:Evidence from Fluid Inclusion Data

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Acta Geologica Sinica(English Edition) 2022年第1期96卷 240-247页

作者： ZHOU Aorigele ZHENG Ming tang juxing HE Wen CHEN Hongjin MLR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China

In order to understand how the metallogenic process of porphyry deposit specifically and directly respond to regional uplifting and exhumation,we compiled previous fluid inclusion data of 32 porphyry deposits in China by recalculating the fluid trapping depths and trapping depth reduction magnitude from early to late mineralization stage veins.The data reveal that the average trapping pressure ratio(Ave TP_(E)/TP_(L))between early-and late-stage veins of the these deposits are 1.2-18.4,mainly in the range of 1.35-5.83,with average trapping pressure reduction(1-Ave TP_(L)/TP_(E))from early-to late-stage veins are 17%-95%,and mainly in the range of 25%-83%.The fluid trapping pressure based mineralization depths most of the porphyry deposits in China had decreased from early to late vein stages by at least 450 m(900-5800 m predominant),or greater than 950 m when take the average depth reduction value,which is greater than the current gap between early-and late-stage veins of each deposit.We propose that the apparently greater mineralization depth reduction magnitude than the current elevation gaps between early and late veins are likely a consequence of synmineralization uplifting and exhumation process that often occurs in porphyry systems.

关键词： fluid inclusion syn-mineralization uplifting exhumation porphyry deposit

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Geochronology,Geochemistry and Petrogenesis of the Bangbule Quartz Porphyry:Implications for Metallogenesis

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Acta Geologica Sinica(English Edition) 2023年第3期97卷 744-758页

作者： HE Chuankai WANG Yong WANG Haiyong tang juxing YAN Penggang WANG Yongqiang FU Xuelian FENG Yipeng College of Earth Sciences Chengdu University of TechnologyChengdu 610059China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesCAGSBeijing 100037China No.6 Geological Party Tibet Bureau of Geology and Mineral Exploration and DevelopmentLhasa 851400China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China

The Bangbule skarn lead-zinc(Pb-Zn)deposit(>1 Mt Zn+Pb)is located in the western Nyainqentanglha polymetallic metallogenetic belt,central Tibet.Lenticular orebodies are all hosted in skarn and developed in the contact zone between the quartz porphyry and carbonate strata of the mid Paleozoic Middle to Upper Chaguoluoma Formation as well as in carbonate and sandstone beds of the Upper Paleozoic Laga Formation.As a newly discovered skarn deposit,the geological background and metallogenesis of this deposit remain poorly understood.Detailed petrological,geochemical and geochronological data of the ore-related quartz porphyry,helps constrain the mineralization age and contributes to discussion on the ore genesis of the Bangbule deposit.Both endoskarn and exoskarn are identified in the Bangbule deposit.From quartz porphyry to carbonate formation,the exoskarn is zoned from proximal garnet skarn to distal pyroxene skarn.Zircon U-Pb dating results show that the quartz porphyry formed at 73.9±0.8 Ma.Geochemical analysis results show that the quartz porphyry has high contents of SiO_(2)(71.40–74.94 wt%)and K_(2)O+Na_(2)O(3.76–8.46 wt%)with A/CNK values of 0.69 to 1.06.Besides,the quartz porphyry is enriched in large ion lithophile elements(LILEs)and light rare earth elements(LREEs)and have lowεNd(t)(from-8.25 to-8.19)and high initial(^(87)Sr/^(86)Sr)i values(0.713611–0.714478).Major,trace elements and whole-rock F concentration analysis results from the endoskarn samples show higher TFe_(2)O_(3),MgO,CaO,Pb+Zn,W,Sn,Mo and F etc.,and lower alkalis(K_(2)O,Na_(2)O,Sr and Ba)than those of fresh quartz porphyry,indicating that the early ore-forming fluids were an Ca-Fe-F-enriched fluid.Massive ore in the proximal skarn might be related to the high F content in the magma,which lowered the solidus temperature of the quartz porphyry magma and caused a lower temperature of the ore-forming fluids,as well as facilitating the precipitation of sphalerite and galena.Based on the geochemical characteristics presented in this study,we propo

关键词： petrogenesis quartz porphyry metallogenesis Bangbule skarn deposit Tibet

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Geochronology,Geochemistry,and Implications of Aplite Dyke in the Giant Jiama Porphyry Copper System,Tibet

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地质学报:英文版 2023年第5期97卷 1406-1421页

作者： QI Jing tang juxing LIN Bin YANG Hairui tang Xiaoqian tang Pan FANG Xiang ZHANG Tingting LI Faqiao SUN Miao WANG Mengdie CUI Hao XIE Jinling School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China Institute of Mineral Research China Metallurgical Geology BureauBeijing 101300China China Mining Federation of Beijing Consulting Center Beijing 100044China Southwest University of Science and Technology MianyangSichuan 621000China Chinese Academy of Geological Sciences Beijing 100037China Development and Research Center China Geological SurveyBeijing 100037China Chengdu University of Technology Chengdu 100059China Tibet University Lhasa 850000China

Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetallic mineralization.These ore-bearing porphyries include monzogranite,granodiorite,and quartz diorite porphyries.A new granite aplite dyke was found in the south of Jiama.Its age,genesis,and relationship with ore-related magmatism are obscure.Here,its emplacement age and petrogenesis were determined using mineralogy,zircon U-Pb dating,geochemistry,and Sr-Nd-Pb isotope studies.The zircon LA-ICP-MS U-Pb age of the aplite dyke is 16.66±0.21 Ma(n=14,MSWD=0.66),earlier than that of the ore-bearing porphyries(~15 Ma)in Jiama.Furthermore,the aplite exhibits high amounts of silicon(SiO_(2)=73.39%-74.74%),potassium(K_(2)O=5.12%-6.61%),aluminum(Al_(2)O_(3)=14.25%-14.69%),and light/heavy rare earth elements(LREE/HREE=12.12-16.19)as well as negative europium(δEu=0.47-0.72)and weak negative cerium anomalies(δCe=0.84-0.93).The aplite dyke is characteristic of metaluminous-peraluminous I-type granite,which is rich in large-ion lithophile elements(Rb,Ba,Th and U)and depleted in high-field-strength elements(Nb,P and Ti).The aplite dyke and ore-bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust,according to whole-rock geochemistry and Sr-Nd-Pb isotope data,but the dyke and ore-bearing porphyries were emplaced from the same magma chamber at different times.Thus,the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.

关键词： U-Pb age Sr-Nd-Pb isotope geochemistry aplite dyke Jiama

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Petrogenesis and Geodynamic Implications of Early Cretaceous(~130 Ma)Magmatism in the Baingoin Batholith,Central Tibet:Products of Subducting Slab Rollback

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Acta Geologica Sinica(English Edition) 2022年第6期96卷 1960-1978页

作者： LI Faqiao tang juxing WANG Nan LIU Zhibo SONG Yang ZHANG Jing MA Xudong FU Bin LI Haifeng HAN Songhao School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China MLR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China Research School of Earth Sciences Australian National UniversityCanberraACT 2601Australia China’s 19th Metallurgical Corporation Chengdu 617000China

The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane.Its petrogenesis and tectonic setting have been studied for decades,but remain controversial.Here we report data on geochronology,geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith,which provide more evidence to uncover its petrogenesis and regional geodynamic processes.The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I-type,S-type and highly fractionated granites.The I-and S-type granites exhibit medium SiO2,high K_(2)O/Na_(2)O with negativeεNd(t)andεHf(t)values,whereas,the albite granites have very high SiO_(2)(79.04%–80.40%),very low K_(2)O/N_(2)O,negativeεNd(t)and a large variation inεHf(t).Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area.The granodiorites involved had a hybrid origin from partial melting of basalt-derived and Al-rich rocks in the crust,the porphyritic monzogranites being derived from partial melting of pelitic rocks.The albite granites crystallized from residual melt separated from K-rich magma within the‘mush’process and underwent fractionation of K-feldspar.We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward-subducting slab of the NTO.

关键词： petraluminous granites highly fractionated granites Baingoin batholith subducting slab rollback Tibet

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Genesis of the Sinongduo Carbonate-hosted Pb-Zn-Ag Deposit in the Central Lhasa Terrane,Tibet

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Acta Geologica Sinica(English Edition) 2023年第3期97卷 759-776页

作者： RAN Fengqin tang juxing YANG Zongyao DUO Ji REN Dongxing GUO Wenbo WU Xin HAO Jinyue HE Yifei SUN Yang College of Earth Science Chengdu University of TechnologyChengdu 610059China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological ScienceBeijing 100037China Chengdu Surveying Geotechnical Research Institute Co. Ltd.of MCCChengdu 610023China Chengdu Engineering Corporation Limited PowerChinaChengdu 611130China New Energy Geology Team of the Hebei Coalfield Geology Bureau XingtaiHebei 054000China

The Sinongduo mining region includes two types of mineralizations:the epithermal and the carbonate-hosted PbZn-Ag deposits.Despite being studied for many years,the ore formation process and genesis of the carbonate-hosted Pb-Zn-Ag deposits remain poorly understood.The Pb-Zn-Ag ore bodies occur as veins and are hosted by limestone and dolostone of the Permian Xiala Formation.Three sulfide mineralization substages have been identified at the Sinongduo carbonatehosted deposit.Indium coupled with Cu,Co and Sn was incorporated into sphalerite as substitutions:2Zn^(2+)?Cu^(+)+In^(3+),(3n/2+1)Zn^(2+)?Co^(2+)+n In^(3+)or(2n+1)Zn^(2+)?Co^(2+)+n(Cu^(+)+In^(3+))(n>1)and 4Zn^(2+)?Sn2++2In^(3+).Sphalerite and pyrite in the mineralization stage displayδ^(34)S values in a narrow range of+5.7‰to+11.3‰,which are similar to those of Palaeocene igneous rocks,indicative of a magmatic source of sulfur.We present systematic carbon-hydrogen-oxygen isotope results that further support a magmatic source for the ore-forming fluids that were influenced by meteoric water.Furthermore,the Pb isotope compositions of sulfide minerals in the Sinongduo carbonate-hosted deposit overlap with the values of coeval Linzizong volcanic rocks and are similar to those of Indian Ocean sediments,indicating upper crustal sources of metals.We conclude that the Sinongduo carbonate-hosted Pb-Zn-Ag deposit is a medium-to low-temperature magmatic-hydrothermal deposit related to Linzizong magmatism.

关键词： sulfur and lead isotopes sphalerite carbonate-hosted deposit Tibet India–Asia collision

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Geochronology and Geochemistry of the Mamupu Cu-Au Polymetallic Deposit,Eastern Tibet:Implications for Eocene Cu Metallogenesis in the Yulong Porphyry Copper Belt

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Acta Geologica Sinica(English Edition) 2022年第4期96卷 1221-1236页

作者： ZHANG Xiaoxu LIN Bin tang juxing HE Liang LIU Zhibo WANG Qin SHAO Rui DU Qiu SILANG Wangdui CIREN Ouzhu GUSANG Quzhen CIDAN Zhongga School of Earth Science and Resources China University of GeosciencesBeijing 100083China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China No.6 Geological Party Tibet Bureau of Geology and Mineral Exploration and DevelopmentLhasa 851400China College of Earth Sciences Chengdu University of TechnologyChengdu 610059China Tibet Shengyuan Mining Group Co. Ltd.Lhasa 851400China

The Mamupu skarn-type Cu-Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt(YPCB),eastern Tibet.The Cu-Au mineralization mainly occurs as chalcopyrite in breccia,within the plate-like carbonate interlayer,being closely related to chloritization(e.g.,chlorite,magnetite and epidote)and skarnization(e.g.,diopside,tremolite and garnet).The ore-related quartz syenite porphyry(QSP)and granodiorite porphyry(GP)were emplaced at 40.1±0.2 Ma and 39.9±0.3 Ma,respectively.The QSP of Mamupu is an alkaline-rich intrusion,relatively enriched in LREE,LILE,depleted in HFSE,with no significant negative Eu and Ce anomalies,slightly high(^(87)Sr/^(86)Sr)i,lowε_(Nd)(t),uniform(^(206)Pb/^(204)Pb)i andε_(Hf)(t)values,which indicates that the porphyry magma may be caused by both the mixing of metasomatized EM II enriched mantle and thickened juvenile lower crust.The QSP in the Mamupu deposit shares a similar genesis of petrology to other ore-related porphyries within the YPCB.High oxygen fugacity and water content of the magmas are essential for the formation of porphyry and skarn Cu deposits.The QSP has similar high magmatic oxidation states and water content to the Yulong deposit,which indicates that the Mamupu has a high prospecting potential.Differences in the geological characteristics and scale of mineralization between the Mamupu and other YPCB deposits may be due to the different emplacement depths of ore-related intrusions,as well as differences in the surrounding rocks.

关键词： skarn Cu deposit geochronology geochemistry Mamupu Yulong porphyry copper belt Tibet

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活动大陆边缘岩浆作用及构造演化——以敦煌地块为例

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岩石学报 2024年第3期40卷 702-718页

作者：甘保平唐菊兴第五春荣西南交通大学地球科学与工程学院成都611756 中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室北京100037 西北大学大陆动力学国家重点实验室西北大学地质学系西安710069

大陆边缘弧是汇聚板块边界与俯冲有关的岩浆作用产物,通常记录了造山带弧岩浆作用、造山过程和大陆地壳形成与演化等诸多重要的地质过程。作为中亚造山带中段最南部的构造单元,敦煌地块为传统定义上具有早前寒武纪变质结晶基底的微陆块... 详细信息

大陆边缘弧是汇聚板块边界与俯冲有关的岩浆作用产物,通常记录了造山带弧岩浆作用、造山过程和大陆地壳形成与演化等诸多重要的地质过程。作为中亚造山带中段最南部的构造单元,敦煌地块为传统定义上具有早前寒武纪变质结晶基底的微陆块,其后在古生代时期经历了多期次、多阶段的与中亚造山带造山相关的构造热事件并使其发生再活化,进而产生了一系列广泛的弧岩浆-变质作用事件。然而,对于该陆块古生代弧岩浆作用机制和地壳构造演化历史缺乏系统的研究。本文综合近十多年来对敦煌地块的诸多最新研究进展,系统梳理了古生代岩浆岩岩石组合类型、年代格架、地球化学组成以及同时期变质-沉积构造热事件演化特征,得到以下认识:(1)敦煌地块古生代岩浆作用过程呈现阶段性特征,即幕式岩浆作用,构造位置上从东北部逐渐迁移到南部再折返到中部,大致可划分为五期:~510Ma、440~410Ma、390~360Ma、~330Ma和280~245Ma,而变质作用事件主要集中在450~360Ma;(2)古生代岩浆岩类型主要以钙碱性I型花岗岩、埃达克质岩石、少量S型花岗岩和高钾花岗岩为主,且岩石成分从寒武纪低钾拉斑系列逐渐转变为二叠纪高钾、富硅特征;(3)同位素地球化学特征表明,敦煌地块中-北部寒武纪-泥盆纪发育的与俯冲相关的弧岩浆对新生地壳的生长起了重要贡献,并伴随古老地壳再造事件;而南部泥盆纪-石炭纪岩浆作用则以古老地壳物质重熔为主;(4)基于埃达克质岩石的证据,敦煌地块在古生代时期经历了两次显著的地壳增厚事件,早期可能是与北山南部石板山地体/弧碰撞以及幔源岩浆底侵有关,而晚期可能是与俯冲板片后撤或回卷相关,地壳厚度可达~55km;(5)敦煌地块属于中亚造山带中段最南部一个具有前寒武纪基底的古老微陆块,后期卷入了古亚洲洋南向俯冲相关的造山事件使其被强烈破坏与改造。该微陆块作为古亚洲洋南部的活动大陆边缘弧,被与俯冲作用有关的阶段性弧岩浆底侵、部分熔融、增厚地壳和区域性变质作用等机制改造与活化,产生了阶段性侵位的陆缘弧岩浆作用。这些认识为探究中亚造山带微陆块的起源和造山带的构造演化提供新的约束。

关键词：大陆边缘弧幕式岩浆作用再活化地壳加厚敦煌地块中亚造山带

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