扬子地块南缘桂北元宝山地区新元古代超基性岩石中铬尖晶石特征及其地质意义  

作　　者：曹雨 周翊 许嘉乐 

机构地区：[1]西南石油大学地球科学与技术学院,四川成都610500

出　　处：《科技创新与应用》2021年第35期24-27,共4页Technology Innovation and Application

基　　金：四川省2020年省级大学生创新训练计划项目(编号:S202010615140);西南石油大学地球科学与技术学院大学生创新创业基金项目(编号:DCXP1907)。

摘　　要：目前,地学界对于扬子地块南缘桂北元宝山地区超基性岩体形成的大地构造背景主要存在岛弧环境和地幔柱环境有两种争议。作为基性岩浆早期结晶的产物,超基性岩石中的铬尖晶石可以作为岩石成因和构造背景的重要指示器。文章对元宝山地区新元古代超基性岩石中的铬尖晶石形貌特征及化学成分进行了研究。通过详细的岩石学和矿物学观察,发现铬尖晶石主要以粒状或浑圆状包裹体赋存于橄榄石和单斜辉石矿物中。扫描电镜能谱分析测试表明,铬尖晶石化学成分相对富Cr、Fe,贫Al、Mg和Ti。根据铬尖晶石成分反演计算,元宝山岩体的母岩浆为低钛拉斑质玄武岩浆。结合铬尖晶石TiO_(2)-Al_(2)O_(3)、Al_(2)O_(3)-Cr2O_(3)及Fe^(3+)-Cr-Al图解和矿物岩石组合,认为元宝山地区超基性岩体形成于岛弧环境。At present,there are mainly two kinds of disputes in geologists about the geotectonic background of the formation of ultrabasic rock bodies in Yuanbao Mountain area of northern Guangxi on the southern margin of the Yangtze block:island arc environment and mantle plume environment.As the product of early crystallization of basic magma,chromium spinel in ultrabasic rocks can be used as an important indicator of petrogenesis and tectonic setting.In this paper,the morphological characteristics and chemical composition of chromium spinel in Neoproterozoic ultrabasic rock mass in Yuanbao Mountain area are studied.Through detailed petrological and mineralogical observation,it is found that chromium spinel occurs mainly in olivine and clinopyroxene minerals as granular or round inclusions.Scanning electron microscope energy spectrum analysis shows that the chemical composition of chromium spinel is relatively rich in Cr and Fe,poor in Al,Mg and Ti.According to the inversion calculation of chromium spinel composition,the parent magma of Yuanbao Mountain rock body is low titanium tholeiitic basaltic magma.Based on the TiO_(2)-Al_(2)O_(3)、Al_(2)O_(3)-Cr2O_(3) and Fe^(3+)-Cr-Al diagrams of chromium spinel and the mineral-rock assemblage,it is considered that the ultrabasic rock mass in Yuanbao Mountain area was formed in the island arc environment.

关 键 词：扬子地块 新元古代 超基性岩体 铬尖晶石 构造背景 

分 类 号：P588.12[天文地球—岩石学]