内蒙古贺根山蛇绿岩型铬铁矿中固体包裹体矿物化学成分研究

A STUDY ON THE CHEMICAL COMPOSITION OF MINERAL INCLUSIONS IN CHROMITE FROM THE HEGENSHAN OPHIOLITE MASSIF,INNER MONGOLIA,CHINA

内蒙古贺根山蛇绿岩型(豆荚型)铬铁矿矿床分布于内蒙古-大兴安岭海西褶皱带的蛇绿岩套内的贺根山岩块中。该蛇绿岩块主要由地幔橄榄岩、堆积岩和基性熔岩组成。铬铁矿矿体主要赋存于地幔橄榄岩相内的纯橄岩脉内,或被薄层的纯橄岩(数厘米到数米)外壳包围,矿体成群和成带分布。 在铬铁矿矿石中发现多种固体包裹体矿物,如橄榄石、斜方辉石、单斜辉石、角闪石、韭闪石、硬玉、钠长石、钛钠金云母等。这种特殊的固体包裹体矿物组合反映了铬铁矿矿床的成因或形成环境。

The Hegenshan ophiolite and associated chromite deposits occur in the east-ern part of the Variscan Tan Shan-Inner Mongolia orogenic. belt. The Hegenshan ophiolitic suite consists mainly of three units, harzburgite, gabbro-dunite-troctolite cumulative complex and basic lava. The chromite ore deposits ofcommercial value occur in the location where the dunite dykes are well developed.The mineralization is developed in the cumulative complex and mantle peridotite. Minerals such as olivine, orthopyroxene clinopyroxene, pargasite, albite,jadeite, nepheline and Na-phlogopite included in the chromite have been wellstudied by means of microprobe. Olivine, orthopyroxene and clinopyroxene inclusions contain more MgO andhave higher Mg/(Mg+Fe) ratios than the rock-forming minerals. Mineral inclusions in the chromite all contain more Cr_2O_3. Clinopyroxeneinclusions are rich in Na_2O. From the above it can be ioncluded that the chromite ore associated withthe ophiolite is not formed from strong partial melting, but from the magmarich in Cr_2O_3, Al_2O_3, Na_2O and H_2O, which originated from the deep levelsof the mantle.