摘要
桂西隆林-西林地区出露了似层状和不规则状辉绿岩侵入体,对其岩石学及地球化学研究表明,该区辉绿岩属于碱性玄武岩系列,具有低SiO_2、高TiO_2和MgO的特征,相对富集轻稀土元素,Ti/Y值为579~742,属于高Ti系列,(La/Yb)_N=6.70~10.20、Nb/U=23~33、Nb/La=0.80~0.94,与二叠纪ELIP内带高Ti玄武岩和桂西其他地区基性岩具有相似的地球化学特征,但隆林-西林地区辉绿岩Zr、Hf和Y亏损,表明它们是地幔柱岩浆部分熔融并经历了一定程度的地壳物质混染形成。隆林-西林地区辉绿岩(^(87)Sr/^(86)Sr)t为0.705 023~0.705 782,ε_(Nd)值为+0.7^+1.0,类似于ELIP高Ti玄武岩和桂西其他地区高Ti基性岩,说明其岩浆源区与ELIP高Ti玄武岩相似,提示了隆林-西林地区辉绿岩可能为峨眉山大火成岩省外带岩浆作用的产物。
The layered intruded mafic lavas and dikes are well cropped out around the Longlin - Xilin area in western Guangxi. The petrogenesis study of the mafic dikes will better understand the tectonic-magmatic signifi-cance of this region. Petrographic and major trace element geochemical data show that the mafic dikes belong to alkaline basalt with low Si02and high Ti02, MgO, LREE-enriched characteristics, with Ti/Y =579 -742, （ La/ Yb） N =6. 70 - 10. 20, Nb/U =23 - 33 and Nb/La = 0. 80 -0. 94. Thus, the geochemical features of dikes akin to the Emeishan large igneous province （ ELIP） high-Ti basalts, but they possess the slightly depleted Zr, Hf and Y, and indicate such a melt from the partial melting plume mantle source when experiencing the weak crus-tal contamination. The low （87Sr/86Sr） t（from 0. 705 023 to 0. 705 782） and high eNd（from ＋0. 7 to ＋ 1. 0）, akin to ELIP high-Ti basalts and other high-Ti mafic rocks of western Guangxi, suggest that the Longlin - Xilin mafic dikes most likely represent a part of outer zone of the ELIP plume magmatism. From the regional tectonic relationships between the mafic dikes and the fine-disseminated gold deposits as well as the extensive evolved carbonate platform uplifting, we further conclude that the ore-forming process of gold deposit resembles to that of Nevadans Carlin-type gold deposit in US, the interaction between the Emeishan plume and Paleotethyan subduc-tion zone induced the regional gold deposits.
出处
《桂林理工大学学报》
CAS
北大核心
2017年第2期231-244,共14页
Journal of Guilin University of Technology
基金
国家自然科学基金项目(41463002)
广西科学研究与技术开发计划项目(桂科能1598025-14)
广西自然科学基金项目(2014GXNSFBA118218
2014GXNSFBA11820)
同位素地球化学国家重点实验室(中国科学院广州地球化学研究所)开放基金项目(AKLIG-KF-14-04)
广西"八桂学者"创新团队项目(2013
有色金属成矿理论与勘查技术)
关键词
基性岩
地幔柱
微细浸染型金矿
隆林-西林地区
mafic dykes
mantle plumb
fine-disseminated gold deposit
Longlin - Xilin area
