新疆库鲁克塔格兴地塔格群中石榴石的矿物学特征研究  

Mineralogical characteristics of garnets from Xingditage Group of Kuruk Tag,Xinjiang

作　　者：刘春花[1] 杨林[2,3] 尹京武[1] 蔡佳[4] 杨海涛[1] 邵兴坤[1] 徐海明[5] 王军[5] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,地学实验中心,北京100082 [2]成都理工大学地球科学学院,四川成都610059 [3]国土资源部贵阳矿产资源监督检测中心,贵州贵阳550004 [4]中国地质大学珠宝学院,北京100083 [5]中国地质科学院矿产资源研究所,北京100037

出　　处：《岩石矿物学杂志》2011年第2期234-242,共9页Acta Petrologica et Mineralogica

摘　　要：通过电子探针测试和X射线粉晶衍射分析,对新疆库鲁克塔格兴地塔格群中红色石榴石样品的矿物学特征进行了研究。电子探针测试结果显示,不同变质期次形成的石榴石,铁铝榴石端员组分均由核部到边部逐渐增加,锰铝榴石均由核部向边缘逐渐减少,镁铝榴石由核部到边部逐渐增加,钙质系列石榴石总含量很低且变化稳定。研究表明,兴地塔格群石榴石由核部至边缘生长温度整体上升,形成压力基本稳定,石榴石形成环境的变质程度逐渐提高。根据X射线粉晶衍射数据计算出石榴石的晶胞参数较理论值大,是由Ca2+、Mn2+两种大半径离子对Fe2+的置换数目多于小半径Mg2+对Fe2+的置换引起的。The mineralogical characteristics of garnets from Xinditaga Group,Kuruk Tag,Xinjiang,have been rarely discussed by former researchers.In this paper,the mineralogical features of the red garnets produced in this area were investigated by using hydrostatic methods,refractometer,spectroscope,electron microprobe analysis and X-ray powder diffraction analysis.The crystal forms of garnets are mainly rhombic dodecahedron,icositetrahedron and their combination form.The garnets are bright red to dark red in color,and have abundant fractures and internal crystal inclusions,causing the tremendous decrease of the hosts’ transparency.The relatively light elements Ca2＋,Mg2＋ and Mn2＋ substitute for Fe2＋ so that the density of the garnets is lower than the average value of almandine.The strong bands in optical spectra of almandine indicate that Mg2＋ rarely replaces Fe2＋.With regard to garnets formed in different metamorphic stages,the results of EPMA show that from the garnet’s core to rim,the amount of almandine end-member tends to increase,namely the mole fractions of the almandine end-members of samples Garnet 1,Garnet 2,Garnet 3 and Garnet 4 are 63.906%～72.408%,65.663%～71.880%,64.689%～71.711% and 50.011%～71.780% respectively.Moreover,the content of spessartine end-member shows a trend of decrease from the garnet’s core to rim,that is,the mole fractions of spessartine end-members of samples Garnet1 to Garnet4 are 23.417%～12.900%,20.211%～12.258%,21.124%～13.297% and 41.943%～18.523% respectively.In addition,the pyrope end-member increases in content from core to rim in which the mole fractions from sample Garnet1 to sample Garnet4 are 8.963%～11.880%,10.200%～12.681%,11.170%～12.500% and 5.411%～7.302%.However,the calcium series of garnets are relatively low in amount and relatively stable.The calcium series consists of grossularite,andradite and uvarovite,in which the mole fractions from sample Garnet1 to sample Garnet4 are 2.662%～4.320%,3.066%～3.695%,2.484%～3.406% and 2.395%～4.222%

关 键 词：库鲁克塔格 兴地塔格群 石榴石 包裹体 端员组分 

分 类 号：P578.947[天文地球—矿物学]