华北克拉通北缘乌兰地区石墨矿地质特征及成因分析

Discussion on Genetic Types and Prospecting Markers of Graphite Deposits in Ulan Area of Inner Mongolia

为了解华北克拉通北缘乌兰晶质石墨矿成矿条件及成因类型,在详细野外地质调查的基础上,利用13C同位素分析、差热分析等手段进行测定。石墨δ13C含量平均为-27.17‰,略高于世界各地不同时代有机质δ^(13)C平均值(-26‰)。石墨最大放热峰值为726~1030℃,主要分布于900~1030℃,证实石墨矿区域变质程度达角闪岩相和麻粒岩相;碳质来源于同源生物有机质,结合矿床地质特征及矿物组合特征,判断石墨矿的含矿建造为一套典型的高温变质富铝沉积岩组合;含有机质沉积物经区域变质作用,有机质被分解重结晶形成石墨矿源层;华力西期侵入体提供热源促使石墨片度增大,后期遭受韧性剪切造成石墨富集而成矿。

On the basis of field investigation,this paper used 13C isotope analysis and differential thermal analysis to determine the metallogenic conditions and genetic types of Wulan crystalline graphite ore in the northern margin of Craton in North China.The average content of graphene ^(13)C is-27.17‰,slightly higher than that of the organic matter 13C(-26‰).The maximum exothermal peak of graphite is 726-1030℃,mainly between 900-1030℃,showing that the metamorphism of the graphite ore was amphibolite facies and granulite facies.The carbon was from homologous biological organic matter.The characteristic of the deposit and that of mineral combinations deduced that the mineral-bearing structure of graphite ore was a set of typical high-temperature metamorphic aluminium-rich sedimentary rocks.The organic deposits were decomposed and recrystallized by regional metamorphism,forming graphite source beds.The heat source provided by the Hualixi intrusive body increased the flake of the graphite,thus graphite ore enriched and formed at later stage because of ductile shear.