豫南史庄一带金伯利岩中石榴子石矿物学特征及其形成条件的约束  

Mineralogical characteristics and constraints of formation conditions of garnet in kimberlite in Shizhuang area,southern Henan Province

作　　者：李积山 张军杰 刘伟[1,2] 余翠 LI Jishan;ZHANG Junjie;LIU Wei;YU Cui(No.3 Institute of Geological and Mineral Resources Survey of Henan Bureau of Geology and Mineral Exploration,Xinyang 464000,Henan,China;Henan key laboratory of granite and mineralization,Xinyang 464000,Henan,China;Henan Nuclear Industry Geology Bureau,Xinyang 464000,Henan,China)

机构地区：[1]河南省地质矿产勘查开发局第三地质矿产调查院,河南信阳464000 [2]河南省花岗岩与成矿作用重点实验室,河南信阳464000 [3]河南省核工业地质局,河南信阳464000

出　　处：《地质通报》2022年第5期824-835,共12页Geological Bulletin of China

基　　金：河南省财政地质勘查项目《河南省信阳市史庄一带金刚石矿预查》(编号:豫国土资发[2017]22号)。

摘　　要：豫南史庄一带位于华北地台南缘,分布有金伯利岩,为了确定岩石中的石榴子石矿物种类及其与金刚石的关系,通过人工重砂鉴定,对挑选出的40件石榴子石矿物单晶进行了电子探针微区化学成分分析。结果显示,区内石榴子石矿物族化学通式A_(3)B_(2)[SiO_(4)]_(3)中的A组阳离子主要由Mg^(2+)、Fe^(2+)和少量Ca^(2+)占位,B主组阳离子主要由Al^(3+)和少量Fe^(3+)、Cr^(3+)、Mn^(3+)占位,表明区内石榴子石主要为铁铝榴石(Alm)-镁铝榴石(Pry)-钙铝榴石(Gro)系列组合。根据矿物化学特征,区内镁铝榴石为榴辉岩型(E型),具有含钛钙低铬富铁的特征,属Grutter等划分的G4-G5组(含钛、钙)镁铝-铁铝榴石,与金伯利岩、金刚石包体或者A组榴辉岩中的石榴子石特征相同。区内发现有超硅石榴子石,经计算其形成压力范围为10.2~10.9 GPa,对应深度超过250 km。Shizhuang area in southern He nan located in the south margin of north China platform,with kimberlite.In order to determine the types of garnet and their relationship with diamond,40 selected garnet mineral single crystals were analyzed by electron probe micro-area.The results show that the cations of group A in the general formula A 3 B 2[SiO 4]3 of the garnet mineral group are mainly occupied by Mg^(2+),Fe^(2+)and a small amount of Ca^(2+),the cations of group B are mainly occupied by Al^(3+)and a small amount of Fe^(3+),Cr^(3+)and Mn^(3+).The garnet in the area is mainly composed of Alm-Pry-Gro series.According to the mineral chemical characteristics,the Mg-Al garnet in the area is eclogite type,which is characterized by titanium-calcium,low-chromium and iron-rich.It belongs to Grutter’s G4-G5 group(containing titanium and calcium)Mg-Al-Fe-Al garnet,and has the same characteristics as kimberlite,diamond inclusion or garnet in group A eclogite.Supersilicon garnet is found in the area,and its formation pressure ranges from 10.2 GPa to 10.9 GPa,with a depth of more than 250 km.

关 键 词：镁铝榴石 电子探针 指示矿物 超硅石榴子石 河南史庄 

分 类 号：P57[天文地球—矿物学] P578.947[天文地球—地质学]