| 峨眉山大火成岩省东区普安玄武岩系年代学、地球化学及成因研究 |
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| 引用本文： | 戢兴忠,陈强,程志国,王倩,马克忠,刘旭.峨眉山大火成岩省东区普安玄武岩系年代学、地球化学及成因研究[J].岩石矿物学杂志,2021,40(2):363-382. |
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| 作者姓名： | 戢兴忠 陈强 程志国 王倩 马克忠 刘旭 |
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| 作者单位： | 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;贵州省地质矿产勘查开发局 106地质大队, 贵州 遵义 563099;中国地质大学 地质过程与矿产资源国家重点实验室, 北京 100083 |
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| 基金项目： | 国家自然科学基金面上基金（41572072，42072110）；中国地质调查局项目（DD20160124，DD20190606）；贵州省地质矿产勘查开发局地质科研项目（黔地矿科合[2016]16号） |
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| 摘 要： | 广泛分布于中国西南川、滇、黔三省的峨眉山玄武岩是我国最早被国际认可的大火成岩省,受到了国内外学者的广泛关注。前人对大火成岩省西区玄武岩已达成多项共识,而对东区玄武岩的岩石组合、火山活动时限、岩石成因等方面还存在诸多争议。本文以峨眉山大火成岩省东区贵州普安玄武岩系为研究对象,通过解析典型剖面,明确该区玄武岩系岩石类型从底到顶总体为第1旋回的爆发相火山角砾岩、第2旋回的溢流相玄武岩以及第3旋回的火山沉积相凝灰岩。玄武岩系顶部凝灰岩锆石LA-ICP-MS U-Pb测年结果限定了大火成岩省东区火山活动时间持续上限为250 Ma。主微量元素显示该区玄武岩系以高Ti碱性玄武岩为主。玄武岩稀土元素球粒陨石标准化为轻稀土元素富集的右倾曲线模式,Rb和Sr亏损、Ba和Hf富集等特征与贵州地区玄武岩、峨眉山大火成岩省西区高Ti玄武岩以及OIB地球化学特征基本一致。微量元素显示该区玄武岩源区可能为受交代的石榴石地幔橄榄岩,由深部地幔柱上升至石榴石橄榄岩稳定区部分熔融产生熔融体,和富集交代流体的大陆岩石圈地幔混合形成,岩浆上升运移过程中发生了一定程度分离结晶作用和微弱地壳混染作用。研究表明,峨眉山大火成岩省东区普安玄武岩系形成于峨眉山地幔柱边部埋深较大、低程度部分熔融以及高压的环境。
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| 关 键 词： | 峨眉山大火成岩省 普安玄武岩系 地球化学 锆石U-Pb测年 地幔柱 |
| 收稿时间： | 2020/9/22 0:00:00 |
Geochronology, geochemistry and petrogenesis of the Pu'an basalt succession from eastern Emeishan large igneous province |
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| JI Xing-zhong,CHEN Qiang,CHENG Zhi-guo,WANG Qian,MA Ke-zhong,LIU Xu.Geochronology, geochemistry and petrogenesis of the Pu'an basalt succession from eastern Emeishan large igneous province[J].Acta Petrologica Et Mineralogica,2021,40(2):363-382. |
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| Authors: | JI Xing-zhong CHEN Qiang CHENG Zhi-guo WANG Qian MA Ke-zhong LIU Xu |
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| Institution: | MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, CAGS, Beijing 100037, China;No. 106 Geological Party, Guizhou Bureau of Geology and Mineral Resources, Zunyi 563099, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China |
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| Abstract: | Emeishan basalts, widely distributed in Sichuan, Yunnan and Guizhou in southwestern China, are the earliest internationally recognized large igneous provinces in China and have been favored by a large number of experts both in China and abroad. Many consensuses have been reached on the basalt in the western part of the Emeishan large igneous province (ELIP), but there are still several controversies in such aspects as the rock associations, the time limit of volcanic activities and the genesis of rocks. With the basalt of Pu''an in western Guizhou, eastern part of ELIP as the study object and through the analysis of typical basalt profiles, the authors detected that the rock types in this area are eruptive facies of volcanic breccia in the first cycle, flooding facies of basalt in the second cycle and volcanic sedimentary facies of tuff in the third cycle from bottom to top. Zircon LA-ICP-MS U-Pb dating from the tuff which is located at the top of the basalt defined the upper time limit of volcanic activity in the east of the ELIP to 250 Ma. The major and trace elements indicate that the basalts in this area are mainly high-Ti and alkaline basalts. The characteristics of Rb-Sr depletion and Ba-Hf enrichment are basically consistent with the geochemical characteristics of basalts in Guizhou, high Ti basalts in the west of ELIP, and OIB. Trace elements show that the origin of the basalt is metasomatic garnet mantle peridotite, and the melt generated by partial melting when rising from the deep mantle plume to the stable area of garnet peridotite was mixed with the continental lithospheric mantle enriched with metasomatic fluids. Crystallization differentiation was significant while the crustal mixing degree was weak during the ascent and migration of magma. The results show that the basalt in the eastern ELIP was formed in the environment of greater depth, low partial melting and high pressure at the edge of the mantle plume. |
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| Keywords: | Emeishan large igneous province (ELIP) Pu''an basalt succession geochemistry zircon U-Pb dating mantle plume |
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