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Geochronology of the Gabbro-mafic Microgranular Enclaves-granite Associations in the Gejiu District, Yunnan Province and Their Geodynamic Significance 被引量:6
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作者 CHENG Yanbo MAO Jingwen 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2012年第3期748-761,共14页
Many igneous rocks distribute in Gejiu tin polymetallic ore-field at Yunnan province, rocks including basalt, gabbro, mafic microgranular enclaves, granites (porphyritic granite and equigranular granite) and akaline... Many igneous rocks distribute in Gejiu tin polymetallic ore-field at Yunnan province, rocks including basalt, gabbro, mafic microgranular enclaves, granites (porphyritic granite and equigranular granite) and akaline rocks. The ages of the granites and akaline rocks which are considered to have genetic connecting with the mineralization have been comfirmed, but the gabbro- mafic microgranular enclaves-granite assemblage's ages are still unknown. By means of LA-ICP-MS zircon U-Pb dating, the data of Shenxianshui equigranular granite, the mafic microgranular enclave in Jiasha area, the host rock of the mafic microgranular enclaves and the Jiasha gabbro are around ~80 Ma. Besides the above mentioned data, a group of new ages at ~30 Ma were discovered in this study, which is from gabbro and mafic microgranular enclaves. Based on the previous data and the new data gained this time, we suggest the major geochronology framework of the magmatism and mineralization events in Gejiu area is ~80 Ma, which is consistent with the Late Cretaceous magmatism and mineralization events in the whole southeast Yunnan and west Guangxi area and they were suggested to belong to the same geotectonic setting in late Yenshannian. And the new ages of the ~30 Ma obtained in this study is considered to represent a responding to the complicate tectonic evolution history of the Tibetan orogenic events in Cenozoic. 展开更多
关键词 GABBRO GRANITE mafic microgranular enclaves GEOCHRONOLOGY geodynamic setting Gejiu
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Timing of Magma Mixing in the Gangdisê Magmatic Belt during the India-Asia Collision: Zircon SHRIMP U-Pb Dating 被引量:103
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作者 MOXuanxue DONGGuochen +3 位作者 ZHAOZhidan GUOTieying WANGLiangliang CHENTao 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2005年第1期66-76,共11页
Abundant mafic microgranular enclaves (MMEs) extensively distribute in granitoids in the Gangdise giant magmatic belt, within which the Qüxü batholith is the most typical MME-bearing pluton. Systematic sampl... Abundant mafic microgranular enclaves (MMEs) extensively distribute in granitoids in the Gangdise giant magmatic belt, within which the Qüxü batholith is the most typical MME-bearing pluton. Systematic sampling for granodioritic host rock, mafic microgranular enclaves and gabbro nearby at two locations in the Qüxü batholith, and subsequent zircon SHRIMP II U-Pb dating have been conducted. Two sets of isotopic ages for granodioritic host rock, mafic microgranular enclaves and gabbro are 50.4±1.3 Ma, 51.2±1.1 Ma, 47.0±l Ma and 49.3±1.7 Ma, 48.9±1.1 Ma, 49.9±1.7 Ma, respectively. It thus rules out the possibilities of mafic microgranular enclaves being refractory residues after partial melting of magma source region, or being xenoliths of country rocks or later intrusions.Therefore, it is believed that the three types of rocks mentioned above likely formed in the same magmatic event, i.e., they formed by magma mixing in the Eocene (c. 50 Ma). Compositionally, granitoid host rocks incline towards acidic end member involved in magma mixing, gabbros are akin to basic end member and mafic microgranular enclaves are the incompletely mixed basic magma clots trapped in acidic magma. The isotopic dating also suggested that huge-scale magma mixing in the Gangdise belt took place 15-20 million years after the initiation of the India-Asia continental collision, genetically related to the underplating of subduction-collision-induced basic magma at the base of the continental crust. Underplating and magma mixing were likely the main process of mass-energy exchange between the mantle and the crust during the continental collision, and greatly contributed to the accretion of the continental crust, the evolution of the lithosphere and related mineralization beneath the portion of the Tibetan Plateau to the north of the collision zone. 展开更多
关键词 SHRIMP isotopic dating GRANITES magma mixing mafic microgranular enclaves Qüxü pluton Gangdisê TIBET
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Paleo-Tethyan Oceanic Crust Subduction in the Eastern Section of the East Kunlun Orogenic Belt:Geochronology and Petrogenesis of the Qushi'ang Granodiorite 被引量:14
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作者 CHEN Guochao PEI Xianzhi +6 位作者 LI Ruibao LI Zuochen LIU Chengjun CHEN Youxin PEI Lei WANG Meng LI Xiaobing 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2017年第2期565-580,共16页
The Qushi’ang granodiorite(QSG) is located at the central east of the ophiolitic melange belt in the East Kunlun Orogenic Belt(EKOB) in the northern margin of the Qinghai-Tibetan Plateau. LA-MC-ICP-MS zircon U–P... The Qushi’ang granodiorite(QSG) is located at the central east of the ophiolitic melange belt in the East Kunlun Orogenic Belt(EKOB) in the northern margin of the Qinghai-Tibetan Plateau. LA-MC-ICP-MS zircon U–Pb dating suggests that the granodiorite and mafic microgranular enclaves(MMEs) crystallized 246.61±0.62 and 245.45±0.9 Ma ago, respectively. Granodiorite, porphyritic diorite, and MMEs are metaluminous and medium-K calk-alkaline series, with island-arc magma features, such as LILE enrichment and HFSE depletion. The porphyritic diorite has high Cr(13.50 ppm to 59.01 ppm), Ni(228.53 ppm to 261.29 ppm), and Mg~#(46–54). Granodiorite and porphyritic diorite have similar mineral compositions and evolved major and trace elements contents, particularly Cr and Ni, both of which are significantly higher than that in granites of the same period. The crystallization age of MMEs is close to that of granodiorite, and their major and trace elements contents are in-between porphyritic diorite and granodiorite. The results suggest that the original mafic magma, which was the product of mantle melting by subduction process, intruded into the lower crust(Kuhai Rock Group), resulting in the formation of granodiorite. Countinous intrusion of mafic magma into the unconsolidated granodiorite formed MMEs and porphyritic diorite. The granodiorite reformed by late-stage strike-slip faulting tectonic event indicates that the strike-slip fault of Middle Kunlun and the collision of the Bayanhar block with East Kunlun were later than 246 Ma. Therefore, the formation of the QSG not only indicates the critical period of evolution of East Kunlun but also represents the tectonic transition from oceanic crust subduction to slab breaking. 展开更多
关键词 East Kunlun Orogenic Belt(EKOB) Qushi’ang granodiorite(QSG) mafic microgranular enclaves(MME) Early Triassic TIBET Proto-Tethy
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Geochemistry of Enclaves and Host Granitoids from the Kashan Granitoid Complex, Central Iran: Implications for Enclave Generation by Interaction of Cogenetic Magmas 被引量:2
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作者 Maryam Honarmand Nematollah Rashidnejad Omran +5 位作者 Franz Neubauer Ghasem Nabatian Mohammad Hashem Emami Albrecht von Quadt Yunpeng Dong Manfred Bernroider 《Journal of Earth Science》 SCIE CAS CSCD 2015年第5期626-647,共22页
The major and trace elements and Sr-Nd-Pb isotopes of Miocene host granitoid rocks and their mafic microgranular enclaves(MMEs) were studied to understand the petrogenesis of MMEs in the Kashan complex, which is par... The major and trace elements and Sr-Nd-Pb isotopes of Miocene host granitoid rocks and their mafic microgranular enclaves(MMEs) were studied to understand the petrogenesis of MMEs in the Kashan complex, which is part of the Urumieh-Dokhtar magmatic belt(Iran). The host rocks consist of quartz-diorite and tonalite associated with a dioritic intrusion. The enclaves show microgranular texture and the same mineralogy as their respective host with plagioclase, quartz and biotite. MMEs have a diorite to quartz-diorite composition and show geochemical characteristics mostly between their granitoid host and the diorite intrusion. Chondrite-normalized REE patterns of all samples are moderately fractionated [(La/Yb)N=2.1 to 12.9]. The MMEs display in part small negative Eu anomalies(Eu/Eu*=0.54 to 0.99), with enrichment of LILE and depletion of HFSE. The enclaves show emplacement depth of -4 to 6 km which is comparable with the host rocks. Moreover, the Hornblende-plagioclase equilibrium temprature of MMEs yields average temperatures of 795℃ which is slightly higher than the host ones. Identical mineral compositions and Nd-Sr-Pb isotopic features of MME-host granitoid pairs indicate interactions and parallel evolution of MME and enclosing granitoid in the Kashan plutons. Additionally, the geochemical and isotopic investigations of host and dioritic intrusions suggest a common source for their genesis. A thermal anomaly induced by underplated basic magma into a hot crust would have caused partial melting in the lower crust to generate Kashan granitoid rocks. 展开更多
关键词 magma interaction mafic microgranular enclave radiogenic isotopes granitoid rocks Kashan Urumieh-Dokhtar magmatic belt
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Late Early-Cretaceous Magma Mixing in the Langqi Island, Fujian Province, China: Evidences from Petrology, Geochemistry and Zircon Geochronology 被引量:1
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作者 Liangliang Huang Liyuan Wang +2 位作者 Hong-Rui Fan Musen Lin Wenhui Zhang 《Journal of Earth Science》 SCIE CAS CSCD 2020年第3期468-480,共13页
The mafic enclaves from Mesozoic intermediate-acid magmatic rocks,widely developed along Fujian coast,are considered to be the results of large-scale crust-mantle interaction and magma mixing.In this paper,petrography... The mafic enclaves from Mesozoic intermediate-acid magmatic rocks,widely developed along Fujian coast,are considered to be the results of large-scale crust-mantle interaction and magma mixing.In this paper,petrography,mineralogy,and geochemistry of granites and mafic microgranular enclaves(MMEs)in Langqi Island are studied to provide new information for tracing crust-mantle interaction.The zircon U-Pb dating results show that the Langqi rocks were formed at^101 Ma,which are metaluminous,enriched in silica and high-K calc-alkaline I-type granites.The enclaves have a typical magmatic structure,which is characterized by magma mixing between high-temperature basic magma and low-temperature acidic magma through injecting.The enclaves and host granites show a tendency to mixed major and trace elements,displaying a clear-cut contact relationship,which is indicative of coeval magmatism.The genesis of Langqi rocks is related to the extensional setting caused by the subduction of Paleo-Pacific Plate,and they are the results of mixing of subduction-related metasomatized mantle-derived mafic and induced crustal-melted granitic magma originating from partial melting of the crustal material. 展开更多
关键词 magma mixing GRANITE mafic microgranular enclaves Langqi Fujian
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Late Triassic Magma Mixing and Fractional Crystallization in the Qingchengzi Orefield,Eastern Liaoning Province:Regional Petrogenetic and Metallogenic Implications 被引量:1
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作者 Hongjing Xie Yuwang Wang +2 位作者 Dedong Li Guochao Zhou Zhichao Zhang 《Journal of Earth Science》 SCIE CAS CSCD 2021年第1期144-157,共14页
The Qingchengzi orefield is an important Pb-Zn-Au-Ag polymetallic orefield in NE Chi-na.The Indosinian magmatism has formed the Shuangdinggou batholith and the Xinling stock,as well as dikes of quartz monzonite porphy... The Qingchengzi orefield is an important Pb-Zn-Au-Ag polymetallic orefield in NE Chi-na.The Indosinian magmatism has formed the Shuangdinggou batholith and the Xinling stock,as well as dikes of quartz monzonite porphyry and lamprophyre.According to petrographic characteristics,the Shuangdinggou intrusion can be divided into the main suite and the central suite.Zircon U-Pb dat-ing yielded crystallization ages of 215.0-220.9 Ma for these various Qingchengzi magmatic units,which are within analytical error and represent coeval magmatism.The Shuangdinggou main suite contains abundant mafic microgranular enclaves(MMEs)and shows features of magma mixing.Geochemically,the major oxide contents of the MMEs and their quartz monzonite host show well-defined linear frac-tionation trends.The REE and trace element patterns of the MMEs and their host are similar,which demonstrates certain degree of geochemical homogenization between the two during magma mixing.The Shuangdinggou main suite shares similar geochemical characteristics with typical high Ba-Sr gra-nites(Ba=1082 ppm-2051 ppm,Sr=803 ppm-886 ppm),and was likely originated from the mixing between a melt derived from partial melting of the thickened lower crust and the enriched mantle.The central suite was likely formed by fractional crystallization of the main-suite magma.The Xinling in-trusion may represent a branch of the Shuangdinggou intrusion and has the same genesis as the central suite.The quartz monzonite porphyries geochemically mimic the Shuangdinggou main suite,and may also be an epioic facies of the Shuangdinggou intrusion.The MMEs and lamprophyres may have been derived from incomplete magma mixing.Formation of the Pb-Zn and Au-Ag deposits in the Qing-chengzi orefield may have been related to the granite/quartz monzonite porphyries near the Shuangdinggou intrusion,which were formed by magma mixing and fractional crystallization. 展开更多
关键词 Qingchengzi orefield Shuangdinggou intrusion magma mixing mafic microgranular enclave(MME) fractional crystallization
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