喀喇沁橄榄石斑晶中流体包裹体的组分特征及其构造意义

Composition of fluid inclusions in olivine phenocryst from Harqin area and its tectonic implications

利用激光拉曼光谱测定了内蒙古东部喀喇沁地区玻基橄辉岩橄榄石斑晶中的原生流体包裹体的成分 ,发现其主要由 CO2 、CO、H2 O、N2 、H2 S、SO2 、芳香族碳氢化合物及少量络阴离子团组成。本文认为 ,此火山岩的橄榄石斑晶中捕获的流体包裹体在一定程度上反映了地幔流体的成分。通过与河北汉诺坝大麻坪地幔岩石捕虏体中的流体成分进行对比 ,认为华北克拉通中、新生代地幔流体成分变化不大 ,它们均形成于软流圈 (层 )上涌、岩石圈伸展的构造背景下。

Laser Raman Microprobe has been used to detect composition of fluid inclusions in olivine phenocrysts in limburgite from Harqin area, eastern Inner-Mongolia. The results show that the fluid inclusions are mainly composed of CO 2, CO, H 2O, N 2 , H 2S, SO 2, hydrocarbons and anionic complex group to a less content,. It is considered that the fluid inclusions trapped in the early-crystallized olivine phenocryst from a slightly evolved mantle-derived magma in a relatively close system may reflect compositions of fluid in the mantle source. Thus by comparison with fluid compositions of peridotite xenoliths from Damaping area of Hannuoba, Hebei province, we suggest that the fluid composition in the mantle beneath north China craton remains stable from the Late Mesozoic to the Cenozoic. Tectonically, both of them are all formed in the lithosphere extensional environment perhaps resulted from upwelling of the asthenosphere.