河南省镇平县小岔沟石墨矿矿床地球化学特征及成因分析

发布时间：2018-06-10 01:07

本文选题：石墨 + 变质岩系　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：河南省镇平县小岔沟石墨矿位于朱阳关—柳泉铺石墨成矿带上,含矿层为一套结晶片岩。矿石类型简单,基本就是钙质晶质石墨片岩一种,石墨为晶质鳞片状。矿区花岗岩属于高硅富钾的过铝质岩石,岩石类型为I型花岗岩,球粒陨石标准化的稀土元素配分曲线呈现“V”字型右倾趋势,轻稀土较陡,斜率较大,重稀土较缓,斜率较小,岩浆来源于陆壳重熔。矿区变质岩系Si O2含量不是很高,Ca O含量和烧失量(LOI)数值较高,原岩可能为钙质沉积岩,具有碳酸盐岩的特点。Rb/Sr的比值较小且具有Ba亏损现象,表明样品物质来源可能为海相沉积。轻重稀土之间分馏明显,具有明显的负Eu异常现象。石墨矿锆石SHRIMP U-Pb测试结果表明,206Pb/238U年龄分布在440.0±4.9—2147±21Ma之间,年龄跨度较大,反映了变质岩系锆石的形成是一个漫长的地质演化过程,从而推断出石墨矿并不是在短期内形成的,它经历了一个漫长的形成过程。根据矿区地层的产状、岩石及岩石矿物组合特征以及岩石化学特征和相关图解等判断出矿区变质岩系原岩可能是在海水频繁振荡环境下沉积的泥砂质、泥钙质、碳酸盐类物质,其间有碳质夹层,原岩形成的构造环境为被动大陆边缘。石墨矿样品的δ13C值变化范围是-17.3×10-3—-18.1×10-3,与有机碳的δ13C值极为相似,与无机碳的δ13C值相差较大,石墨矿的碳物质来源主要为有机碳的沉积。小岔沟石墨矿的成矿机理是:含碳地层在区域变质过程中,在温度、压力、变质溶液的作用下,使原有机碳逐渐变化形成石墨,并随着区域变质作用的增加,后期花岗岩的侵入,使碳酸盐类分解产生部分碳,花岗岩所带的二氧化碳分解产生部分碳,又给石墨的形成提供新的碳质。上述几种碳经过迁移、相对集中、重结晶形成现今的晶质石墨矿床。综上所述,小岔沟石墨矿的成因,是以沉积变质为主,花岗岩的后期叠加的双重作用的结果而成的,成因类型为沉积—变质—岩浆热液叠加改造多成因矿床。
[Abstract]:Xiaochagou graphite ore in Zhenping County Henan Province is located in the Zhuyangguan-Liuquanpu graphite metallogenic belt with a set of crystalline schists. The ore type is simple, basically is calcareous crystalline graphite schist, graphite is crystalline scale shape. The granites in the mining area belong to peraluminous rocks with high silicon and rich potassium. The rock type is I-type granite. The normalized REE distribution curve of chondrites shows a "V" right dip trend, with a steep light rare earth element, a large slope and a slow heavy rare earth element. The slope is small and the magma originates from the remelting of the continental crust. The Sio _ 2 content of metamorphic rocks in the ore area is not very high, and the values of Cao and loi) are relatively high. The primary rocks may be calcareous sedimentary rocks, with the characteristics of carbonate rocks. The ratio of RB / Sr is small and the Ba depletion is also present. It is suggested that the material source of the sample may be marine deposition. The fractionation between light and heavy rare earths is obvious and the negative EU anomaly is obvious. The shrimp U-Pb test results of zircon from graphite ore show that the age distribution of zircon is between 440.0 卤4.9-2147 卤21Ma, which indicates that the formation of zircon in metamorphic rock series is a long process of geological evolution, so it is concluded that the formation of graphite ore did not take place in a short period of time. It went through a long process of formation. According to the occurrence of strata, the characteristics of rock and rock mineral assemblage, the petrochemical characteristics and related diagrams, it is concluded that the original rocks of metamorphic rock series in the mining area may be mud sand, mud calcareous and carbonate materials deposited in the environment of frequent sea water oscillation. There is a carbonaceous intercalation and the tectonic environment of the original rock is passive continental margin. The range of 未 ~ (13) C value of graphite ore sample is -17.3 脳 10 ~ (-3) -18.1 脳 10 ~ (-3), which is very similar to that of organic carbon, but is different from that of inorganic carbon. The carbon source of graphite ore is mainly organic carbon deposition. The metallogenic mechanism of Xiaochagou graphite ore is as follows: during the regional metamorphism, under the action of temperature, pressure and metamorphic solution, the original organic carbon gradually changes to form graphite, and with the increase of regional metamorphism, The intrusion of granites in the late stage resulted in the decomposition of carbonates and the decomposition of carbon dioxide in granite to produce part of carbon, which provided new carbonaceous materials for the formation of graphite. The above mentioned carbon is relatively concentrated and recrystallized to form the present crystalline graphite deposit. To sum up, the genesis of Xiaochagou graphite ore is the result of the dual action of sedimentary metamorphism and late superposition of granite, and the genetic type is sedimentary metamorphic magmatic hydrothermal superposition reformation polygenetic deposit.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.252

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