苏北超高压变质带新集石墨矿地质特征及成因分析

Geological characteristics and Genesis of Xinji graphite deposit in ultrahigh pressure metamorphic belt of northern Jiangsu province

苏北超高压变质带新集石墨矿矿体赋存于东海群班庄组,矿体受地层控制明显。本文通过研究石墨矿体地质特征,分析石墨矿石主要成分并与扬子陆块各类沉积岩对比,结合区域碳同位素判别物源。结果表明,新集石墨矿石主要为石墨石英片岩型石墨矿石;成矿原岩为碳质泥岩,但与一般碳质泥岩相比,CaO、MgO的富集程度更高,是成分较为特殊的碳质泥岩;矿石中碳同位素δ(^(13C))=-31.2×10^(-3)~-22.3×10^(-3),围岩大理岩δ(^(13C))=-0.8×10^(-3)~0.2×10^(-3),石墨与大理岩的碳同位素分布区间完全不同,二者没有重叠区,说明它们的碳质具有不同来源,石墨碳来源于有机沉积物。

Xinji graphite deposit occurs in Banzhuang formation of Donghai Group in ultrahigh pressure metamorphic belt of northern Jiangsu province.Ore bodies are obviously controlled by strata.This paper deals with geological characteristics of the deposit,analysis of constituents of the graphite ore and comparison of the strata with each sedimentary rocks in Yangtze continental block to discriminate material source of the strata with help of regional isotropic data.The ore is mainly composed of graphite-quartz schist type ore.The original rock of the strata is carbonaceous mudstone.Compared with ordinary mudstone the original rock is richer in CaO,MgO.δ^(13)C of the graphite ore is-31.2×10^(-3)~22.3×10^(-3),δ^(13)C of the host marble-0.8×10^(-3)~0.2×10^(-3) distributing in different ranges without overprinting.Such phenomenon suggests that their C comes from different source.C of the graphite ore comes from organic sediments.