| 青藏高原冈底斯带南缘泽当多金属矿田多期岩浆活动及年代意义 |
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| 关键词:multistage magmatism Laser microprobe dating regional tectonic evolution Zetang orefield Gangdise belt Tibetan Plateau |
| 基金项目:中国地质调查局地质矿产调查评价专项(编号: 1212011120185) |
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| Multistage Magmatism of the Zetang Polymetallic Orefield on the Southern Margin of the Gangdise Belt in the Tibetan Plateau and Its Chronological Significance |
| Five-phase acidic magmatism was identified though nearly three years’ field observation, test analysis and study in the Zetang orefield on the southern margin of the Gangdise belt. The LA-MC-ICPMS (laser probes) method was used to determine the zircon U-Pb isotope magma formation age and analyze the magma-forming tectonic background and the effects of natural resources. The zircon U-Pb isotope age of trondhjemites in the west of Zetang County is (156?1.0)~(152.5?1.3) Ma. The rocks are adakites, suggesting that the Paleo-Tethy ocean plate subducted northward and formed an intra-oceanic arc tectonic setting in Jurassic. The zircon U-Pb isotope age of host granodiorite rocks (adakites) of the Sangbujiala deposit located in the north of Zetang County is (94.1?0.96) Ma. The magma probably originated from melting of subduction block, and was contaminated by mantle wedge material. Magmatic evolution was closely related to the intra-oceanic subduction of Sangri Island Arc. There existed two phases of magmatic activities in the east of Zetang County, with the zircon isotope age of granodiorite being (63.0?1.0) Ma and (50.2±1.3)~(45.93±0.21) Ma respectively, both of them exhibited continental margin arc features, which indicates initial India-Asian collision. The zircon isotope age of adamellite in the east of Zetang Country is (31.64?0.47)~(29.88?0.39) Ma, and the petrogeochemistry of these two kinds of rocks shows different characteristics. The Chongmuda granites are adakitic rocks, while the Mingze granites are potassium-rich rocks. It is estimated that the adakitic magma came from the melting of India plate underneath the Lhasa Block. However, the two intrusive rocks are probably exotic blocks or are not original magma, whose geochemistry can not represent the tectonic and magmatic evolution of the Zetang polymetallic orefield. Based on the zircon isotope ages, petrology and geochemistry, the authors have reached the conclusion that the first four phases of magmatic activities had close dynamic relationship with the multistage ocean subduction and initial India-Asian continent collision, and the Late Oligocene alien rocks were affected by the faults in the Zetang orefield. |
| ZHAO Zhen,WU Zhen-han,HU Dao-gong,LU Lu.2014.Multistage Magmatism of the Zetang Polymetallic Orefield on the Southern Margin of the Gangdise Belt in the Tibetan Plateau and Its Chronological Significance[J].Acta Geoscientica Sinica,35(6):703-712. |
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