琼西南晚白垩世千家岩体矿物学特征及其对岩石成因的约束  

Mineralogical characteristics of the Late Cretaceous Qianjia pluton from southwestern Hainan Island and their constraints on petrogenesis

作　　者：陈沐龙 吕昭英[1,2] 马昌前 薛桂澄[1,2] 何玉生[1,2] 魏昌欣 袁勤敏[2] 黄武轩 常振宇[2] 吕嫦艳 CHEN Mulong;LYU Zhaoying;MA Changqian;XUE Guicheng;HE Yusheng;WEI Changxin;YUAN Qinmin;HUANG Wuxuan;CHANG Zhenyu;LYU Changyan(Hainan Key Laboratory of Marine Geological Resources and Environment,Haikou 570206,Hainan,China;Hainan Provincial Geological Survey,Haikou 570206,Hainan,China;Hainan Resources Environment Survey Institute,Haikou 570206,Hainan,China;Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,Hubei,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,Hubei,China)

机构地区：[1]海南省海洋地质资源与环境重点实验室,海南海口570206 [2]海南省地质调查院,海南海口570206 [3]海南省资源环境调查院,海南海口570206 [4]中国地质大学地球科学学院,湖北武汉430074 [5]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地质通报》2024年第4期503-515,共13页Geological Bulletin of China

基　　金：海南省自然科学基金项目《海南铺前地区碱性-过铝质岩石的成因及其地球动力学意义》(编号:421QN368);海南省财政项目《热带雨林国家公园地质遗迹调查评价》(编号:HNDZDC-2020-2);中国地质调查局项目《海南1∶5万加来市、多文市、儋县、中兴镇幅区域地质调查》(编号:1212011220524)。

摘　　要：千家岩体为海南岛典型的晚白垩世早期花岗质杂岩体,岩石类型主要有花岗闪长岩、二长花岗岩及正长花岗岩,常见造岩矿物有黑云母、角闪石、斜长石、碱性长石、石英等。为进一步揭示岩石形成过程及源区性质,反演壳幔相互作用,本文选取千家岩体,利用电子探针技术对不同岩石类型中的主要矿物进行了矿物化学分析。结果显示,角闪石、黑云母均属于壳幔混源成因,斜长石发育正反环带及振荡环带,记录了岩浆混合作用的影响。镜下观察发现,千家岩体各类岩石中存在大量的岩浆不平衡结构,如斜长石和角闪石的环带结构,针状产出的磷灰石,以及斜长石、钾长石和石英的嵌晶结构等,结合暗色微粒包体的分布组合及形态特征,认为千家岩体形成中经历了岩浆混合作用。综合来说,岩石及矿物化学证据均表明,岩浆混合作用是研究区岩石形成的主因,矿物学证据表明,千家岩体岩石类型为I型花岗岩,其源区属钙碱性岩浆,黑云母矿物化学数据表明岩石形成环境为相对较低的氧逸度。The Qianjia granitoid pluton is a typical granitic complex in Hainan Island during the Late Cretaceous.The complex consists of three major rock types,i.e.,granodiorite,monzogranite and syenogranite.The mineral assemblages commonly composed of biotite,hornblende,plagioclase,alkali feldspar,and quartz.To further reveal the processes of rock formation and the characteristics of their source regions,as well as to infer crust-mantle interactions,this paper selects the Qianjia pluton and utilizes electron microprobe to analyze major elements of major minerals in different rock types.The results show that hornblendes and biotites are likely originated from crust-mantle mixing,and annulus zoned plagioclase may represent a magmatic activity.Microscpic identification shows a large number of magma unbalanced structures occur in the Qianjia pluton,such as embedded crystal structure of plagioclases and hornblendes,and acicular apatites,These phenomena indicate a mixing process for generation of the Qianjia composite magma combines mineral assemblages and morphological characteristics of the enclaves.As a result,the petrological and mineralogical data indicate a crust-mantle mixing generation for the Qianjia granitic complex,the mineralogical data also shows similar characteristic to I-type granites with calc-alkaline magma source,biotites formed in a low oxygen fugacity environment.

关 键 词：晚白垩世 海南岛 千家岩体 矿物学 壳幔混合 地质调查工程 

分 类 号：P534.53[天文地球—古生物学与地层学] P57[天文地球—地质学]