桂西大化辉绿岩岩石成因及对区域构造演化的指示  

Petrogenesis of Dahua Diabase in Western Guangxi and Its Indications for Regional Tectonic Evolution

作　　者：石钰祥 刘希军[1,2] 李政林 刘潇[1] 赵兵 覃显著 张一尘 黄雯敏 苏悦 SHI Yu-Xiang;LIU Xi-Jun;LI Zheng-Lin;LIU Xiao;ZHAO Bing;QIN Xian-Zhu;ZHANG Yi-Chen;HUANGWen-Min;SU Yue(College of Earth Science,Guilin University of Technology,Guilin 541004,Guangxi,China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,College of Earth Sciences,Guilin University of Technology,Guilin 541006,Guangxi,China;Guangxi Zhuang Autonomous Region Mineral Resources Reserve Evaluation Center,Nanning 530028,Guangxi,China)

机构地区：[1]桂林理工大学地球科学学院,广西桂林541004 [2]广西隐伏金属矿产勘查重点实验室&有色金属矿产勘查与资源高效利用省部共建协同创新中心,广西桂林541004 [3]广西壮族自治区矿产资源储量评审中心,广西南宁530028

出　　处：《华南地质》2023年第4期617-629,共13页South China Geology

基　　金：广西战略性关键矿产资源成矿与勘查科技创新基地建设项目(桂科ZY21195031);广西八桂学者项目(有色金属成矿理论与勘查技术);广西中青年教师基础能力提升项目(2023KY0270);广西自然科学基金-青年基金(2022GXNSFBA035538)。

摘　　要：桂西大化地区出露大量层状和似层状辉绿岩,探究其成因对了解区域构造演化以及地幔源区特征具有重要意义。本文对大化辉绿岩进行地球化学、Sr-Nd同位素研究,结果表明:桂西大化辉绿岩属于碱性玄武岩系列,具有较高的TiO_(2)含量(2.00~3.82wt.%)和Ti/Y值(860~1176),总体上具有与峨眉山高Ti/Y值玄武岩系列相似的稀土元素和微量元素的含量和特征,可能代表了峨眉山地幔柱岩浆活动的东延。但与峨眉山高Ti/Y值玄武岩相比,大化辉绿岩表现出明显的高场强元素Nb、Ta、Zr、Hf的亏损,具有较高的^(87)Sr/^(86)Sr(t)值(0.710087~0.712849),中度偏低的ε_(Nd)(t)值(-1.68~1.21),综合表明大化辉绿岩的原始岩浆可能来源于峨眉山地幔柱物质,岩浆上升过程中受到了扬子陆块下富集岩石圈地幔物质的混染。大化辉绿岩处于右江盆地的中部,距离哀牢山-马江缝合带较远,且大化辉绿岩及周边地区并未出露更早或同期与俯冲作用相关的岩浆岩,大化辉绿岩涉及的富集岩石圈地幔可能由更早期构造热事件改造形成。There is a large number of layered and quasi-layered dolerite in the Dahua area of western Guangxi,and their petrogenesis is of great significance to the understanding of the regional tectonic evolution processes and the characteristics of the mantle source.In this paper,geochemical and Sr-Nd isotopic studies of Dahua dolerite show that the Dahua dolerite belongs to the alkaline basalt series,with high TiO2 content(2.00~3.82 wt.%)and Ti/Y ratios(860~1176)and generally has the content and characteristics of rare earth element and trace elements similar to those of the high-Ti/Y Emeishan basaltic serie,which may represent the eastward extension of the magmatism of the Emeishan mantle plume.However,compared with the Emeishan high Ti/Y basalts,the Dahua dolerite shows obvious depletion of high field strength elements Nb,Ta,Zr and Hf,and exhibits relatively high ^(87)Sr/^(86)Sr(t)values(0.710087~0.712849)and moderately lowerε_(Nd)(t)values(-1.68~1.21)The data combined shows that the primary magmas of the Dahua dolerite have possibly originated from the material of Emeishan mantle plume,and the magma have subsequently mixed with the enriched lithospheric mantle material underlying the Yangtze block during its ascent.The Dahua dolerite is located in the middle of the Youjiang basin,far away from Ailaoshan-Majiang Suture Zone,and the Dahua dolerite and its surrounding areas do not reveal earlier or simultaneous subduction-related magmatic rocks.Therefore,the enriched lithospheric mantle involved in the Dahua dolerite may be formed by the modification of earlier tectono-thermal events.

关 键 词：峨眉山地幔柱 辉绿岩 岩石成因 岩石圈地幔 构造演化 桂西 

分 类 号：P588.124[天文地球—岩石学]