豫南史庄一带金伯利岩中尖晶石矿物化学特征及其对金刚石找矿的启示  

Mineral chemistry characteristic and enlightenment to diamond prospecting of spinelite in kimberlite from Shizhuang area,Henan Province

作　　者：李积山 唐相伟[1] 郭跃闪 张洋[1] 刘伟[1] LI Jishan;TANG Xiangwei;GUO Yueshan;ZHANG Yang;LIU Wei(No.3 Institute of Geological and Mineral Resources Survey of Henan Bureau of Geology and Mineral Exploration,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

出　　处：《地质通报》2020年第10期1639-1649,共11页Geological Bulletin of China

基　　金：河南省地质勘查基金项目《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：豫南史庄一带金伯利岩位于华北地台南缘,栾川-明港深大断裂带北侧,岩石中普遍含有尖晶石等金刚石的指示矿物。在史庄一带金伯利岩中通过人工重砂鉴定,选获了一批尖晶石等金刚石的指示矿物,通过电子探针微区化学成分分析,对区内尖晶石矿物化学特征进行了研究。结果表明,史庄一带金伯利岩中的尖晶石矿物族端元主要为镁铬铁矿(MgCr 2O 4)-铬铁矿(FeCr 2O 4)-镁尖晶石(MgAl 2O 4)-尖晶石(FeAl 2O 4)系列,其中以镁-铬铁矿(Fe,Mg)Cr 2O 4占优势;铬铁矿中Cr 2O 3、Al 2O 3含量变化范围较大,MgO含量较高(5.57%~15.8%),TiO 2含量较低,为低钛富镁高铝型的铬铁矿(S5型),阳离子数中Mg 2+>Fe 2+,Cr 3+和Al 3+,以及Mg 2+和Fe 2+类质同象替代较广泛。初步分析表明,史庄一带金伯利岩中的铬铁矿为地幔捕虏晶,地幔岩为橄榄岩,其矿物化学特征显示,史庄一带金伯利岩具有一定携带金刚石的能力,对寻找金伯利岩型金刚石矿床具有重要的指示意义。Kimberlite in Shizhuang area of southern Henan Province lies in the south of North China plate and in the north of Luanchuan-Minggang deep-large fault zone.Indicative minerals of diamond,such as spinel,are found in Kimberley rocks.The indicative minerals of spinel and other diamonds have been obtained from kimberlite in Shizhuang area by artificial heavy sand identification.The chemical composition of spinel was studied by means of electron microprobe analysis in this paper.The results show that the spinel group minerals in kimberlite in Shizhuang area are mainly composed of magnesia chromite(MgCr 2O 4)-chromite(FeCr 2O 4)-magnesia spinel(MgAl 2O 4)-spinel(FeAl 2O 4),in which magnesia chromite(Fe,Mg)Cr 2O 4 is dominant.The content of Cr 2O 3 and Al 2O 3 in chromite varies widely,MgO content is high(5.57%~15.8%),TiO 2 content is low,and there exists a chromite with low titanium,rich magnesium and high aluminum content(S5 type).Among the cations of chromite,Mg 2+>Fe 2+,while Cr 3+and Al 3+,Mg 2+and Fe 2+have experienced extensive substitution.A preliminary analysis shows that chromite in kimberlite in Shizhuang area is mantle xenocryst,while in situ mantle is peridotite.The chemical characteristics of spinel minerals show that the kimberlite in Shizhuang area has the capability of carrying diamond,which is of great significance for the exploration of kimberlite type diamond deposits.

关 键 词：尖晶石 金伯利岩 电子探针 铬铁矿 史庄 豫南 

分 类 号：P574.2[天文地球—矿物学] P578.46[天文地球—地质学]