榴辉岩中石榴石矿物化学特征研究——以青海省丁叉叉山钛矿床为例  

Study on the mineral chemistry of garnet in the eclogite of Dingchachashan in the North Margin of Qaidam Basin

作　　者：刘创脱 LIU Chuang-tuo(Key Laboratory of Regional Geology and Mineralization,Hebei GEO University,Shijiazhuang Hebei 050031,China)

机构地区：[1]河北地质大学区域地质与成矿作用重点实验室,河北石家庄050031

出　　处：《电子显微学报》2020年第2期141-150,共10页Journal of Chinese Electron Microscopy Society

基　　金：河北地质大学博士启动基金项目(BQ2018032)。

摘　　要：丁叉叉山钛矿位于青海省海西州乌兰县,构造位置属于柴北缘超高压变质带,处于柴达木板块和欧龙布鲁克微地块的夹持部位。文章通过野外实地调研、室内镜下观察和电子探针测试,结合背散射图像分析,对丁叉叉山钛矿中榴辉岩的特征矿物石榴石和其中的包体柯石英假象及长石类矿物进行详尽而系统的研究。结果表明,石榴石具有明显的成分环带特征。从核部到边部含量变化明显,其中电子探针分析CaO、FeO、MgO、MnO横跨在石榴石颗粒0~500μm处变化范围分别为9.114 wt.%~12.937 wt.%、20.541 wt.%~23.535 wt.%、5.91 wt.%~7.359 wt.%、0.25 wt.%~0.55 wt.%;在绿辉石颗粒中的含量变化区间CaO为:13.82 wt.%~14.897 wt.%,MgO为:8.785 wt.%~10.064 wt.%,Na2O为:4.601 wt.%~6.293 wt.%,FeO为:4.241 wt.%~5.433 wt.%。柴北缘丁叉叉山钛矿床中的石榴石的矿物成分环带、石榴石的矿物裂隙及其包体和矿物之间的存在状态,均证明了石榴石经由多期多阶段生长过程,也为金红石(钛的寄主矿物)、榍石及其他矿物的形成创造了条件。Located in Wulan county,Haixi prefecture,Qinghai province,the south slope of Titanium deposit belong to the ultrahigh pressure metamorphic zone in the north margin of Qaidam basin,where the Qaidam Plate and the Ourobrook Micro-block intersect.Through field investigations,indoor observations and electron probe testing combined with BSE image analysis,this paper carried out a detailed and systematic study on garnet,the characteristic mineral of eclogite in the deposit,and the encrustation of coesite and feldspar minerals.The results show that the garnet has obvious composition zoning characteristics.The contents of CaO,FeO,MgO and MnO ranged from 0μm to 500μm across garnet granules,with the variations ranging from 9.114 wt.%to 12.937 wt.%,20.541 wt.%to 23.535 wt.%,5.91 wt.%to 7.359 wt.%,0.25 wt.%to 0.55 wt.%,respectively.The variation ranges of CaO,MgO,Na2O and FeO were 13.82 wt.%~14.897 wt.%,8.785 wt.%~10.064 wt.%,4.601 wt.%~6.293 wt.%and 4.241 wt.%~5.433 wt.%respectively.The mineral composition,the mineral fissures and the existence state between the inclusions and minerals of garnet from the Titanium mineral in the south slope of Titanium deposit in the north margin of Qaidam prove the multistage and multistage growth process of garnet,which create conditions for the formation of rutile(the host mineral of Titanium),titanite and other minerals.

关 键 词：柴北缘 榴辉岩 石榴石 成分环带 丁叉叉山 

分 类 号：P588.3[天文地球—岩石学] P574[天文地球—地质学]