会泽超大型铅锌矿赋矿地层中泥质“脉体”的辨析

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	会泽超大型铅锌矿赋矿地层中泥质“脉体”的辨析
	李凯旋
导师	罗泰义
	2014
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位名称	硕士
学位专业	矿物学、岩石学、矿床学
关键词	会泽矿区泥质脉体含泥质斑状白云岩地球化学
摘要	在对会泽矿区地下坑道考察中发现，矿区各级坑道中普遍发育类似火成碳酸岩活动的痕迹，主要表现在各穿脉普遍出现有呈脉状、透镜状、圆筒状产出的含有泥质的斑状白云岩和不含明显斑晶的泥质岩。根据其类似次火山岩产出的地质特征和和以碳酸盐矿物白云石微斑晶的地质特征，初步认定该类岩体为火成碳酸岩，希望通过该类岩体的研究确定其是否为碳酸岩以及与峨眉上玄武岩活动、铅锌矿成矿的潜在关系。通过大量岩石学工作查明含泥质斑状白云岩呈斑状结构，斑晶以白云石为主，少量方解石，胶结物为以伊利石、蒙脱石、石英、高岭石，并有少量黄铁矿；白云石斑晶在不同岩体中含量不同。泥质岩主要矿物成分以石英、伊利石为主，少量蒙脱石、白云石、方解石、高岭石等矿物，并含有大量结晶度差较差的伊利石，电子探针能谱分析显示检测出有些泥质岩中普遍结晶程度低的呈圆斑状出现的白云石和方解石微斑晶，该类岩石应为泥质岩到含泥质斑状斑状白云岩的过度类型。透射电镜能谱分析还显示泥质岩中含有极少量的锐钛矿。以上岩石学研究认为，泥质岩和含泥质斑状白云岩中泥质成分的矿物组合明显不同于岩浆成因的碳酸岩的矿物组合，也不同于常与火成碳酸岩相伴产出的碱性岩浆岩的矿物组合，其中广泛出现的石英细小颗粒和结晶程度差的伊利石以及少量的钾长石、高岭石明显属于沉积泥质岩类，据此判断研究岩体并非火成碳酸岩。主量元素数据显示，含泥质斑状白云岩主要化学成分为SiO2、CaO、MgO、Al2O3、K2O，泥质岩的主要化学成分为SiO2、Al2O3、K2O，两类岩体中SiO2、Al2O3、K2O有良好的相关性，表明它们受控于同一矿物。微量元素数据显示泥质岩和泥质斑状白云岩具有相似微量元素配分模式，都明显富集U、Nb、La、Ce、Zr、Hf等不相容元素，泥质岩的配分曲线稍高于含泥质斑状白云岩白云岩。泥质岩和含泥质斑状白云岩稀土元素配分模式也类似，具有轻稀土右倾、重稀土平坦、Eu负异常的特征。微量、稀土元素特征表明碳酸盐岩矿物的加入对泥质岩微量、稀土元素配分没有明显改变，只起到稀释的作用。含泥质斑状白云岩和其中白云石斑晶的C、O同位素组成不具有明显变化，在δ13CPDB—δ18OSMOW图上，研究岩体的C、O同位素分布范围在地层灰岩的赋矿粗粒白云岩的变化范围之内，白云石斑晶可能来源于地层。少数含泥质白云岩样品和泥质岩样品中C同位素具有明显的负漂移，与被认为具有深源流体加入而形成的矿体中脉石方解石的C同位素组成相近，有来自深渊CO2加入的可能。含泥质斑状白云岩和泥质岩中的黄铁矿的S同位素具有还原硫酸盐的特征，与碳酸盐岩地层黄铁矿S同位素组成一致。年代学研究的测试分为地层中稳定出现的灰绿色泥质岩和不整合地层的泥质岩以及含泥质斑状白云岩两类来进行。从挑选出的锆石来看，泥质岩、泥质斑状白云岩中锆石呈碎屑沉积的特征，两类岩石的年代学数据结果一致，都主要集中在700~1100Ma之间，表明泥质岩和含泥质斑状白云岩为中泥质为碎屑沉积形成。从但是古地理特征分析，碎屑成分最可能来自于西侧的康滇古陆。综合以上岩石学、地球化学和年代学的数据我们认为呈小规模次火山岩相的泥质岩、含泥质斑状白云岩中的泥质最可能是同期地层中沉积的粘土岩。其脉状、透镜状、圆筒状的产出特征是后期热液致裂、充填的结果，其中明显的粗粒白云石斑晶是含白云质成分的热液作用于泥质重结晶形成的，白云质成分最可能来自于围岩，不排除深源CO2的加入。
其他摘要	Huize superlarge Pb-Zn-Ge ore deposit is famous for its high grade ores, however, the source of huge metals and the mechanism of metals precipitate are still confused. Main ore bodies occur in Baizuo formation carbonate of Carboniferous. There are many argillaceous veins or bands occur in Baizuo formation carbonate with stock or pipe shape and fullfill with euhedral dolomite. We applied that these argillaceous veins are some kind of subvolcanic carbonatite according relative geological observations and preliminary analysis and the relative between Emeishan mantle and carbonatite. The opinion shed a new light on the ore genetic model of Huize Pb-Zn ore deposit, furthermore, it is important for the whole Chuan-Dian-Qian Pb-Zn mineralization zone. The keystone of the project is to demonstrate these argillaceous vein is subvolcanic carbonatite. However, after the difficulty searching and exploration in last 3 years, the applicant have to accept that the keystone has been broken. These argillaceous vein is most probably some kind of carboniferous claystone, the euhedral dolomite “phenocryst” have been formed by alternated with hydrothermal fluid abundant with CO 2 ,and occur as subvolcanic texture by hydrothermal fracturing. The key evidences have been summarized as follows: Mineralogy. The premary clay minerals are illite and halloysite, plus minor pyrophyllite and kaolinite, fine detrital quartz is often been found in clay matrix. Huge euhedral dolomite and minor pyrite or hematite compose the typical “phenocryst” texture. Rutile, apatite and detrital Zircon are the main accessory mineral. No typical minerals related with carbonatite such as perovskite, phlogopite et al. have been found till now. Chronology. The claystone has some similar K 2 O content and K/Na ratio like K-bentonite, but most of zircon is detrital source. We got about 150 effective age data from 7 samples and the most of age centralize between 500-1200Ma. Such chronology trend is similar as the detrital zircon age from carboniferous precipitate bauxite at northern and central of Guizhou province. Reaction between hydrothermal fluid and gypsum-salt. The carboniferous Baizuo formation carbonate has been proved be abundant with gypsum-salt for the positive S isotope in mineralization system. After the reaction between hydrothermal fluid and gypsum-salt, the soft claystone, co-occur with the gypsum-salt strata, is easy to filling the void by the reaction and hydrothermal-fracturing. The euhedral dolomite have been formed when the disperse gypsum in claystone are alternated by CO 2 -rich hydrothermal fluid. Pseudo-phenocryst and fracture-filling vein, stock and pipe composed of some subvolcanic-like texture.
学科领域	矿床地球化学
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/5898
专题	研究生_研究生_学位论文
推荐引用方式 GB/T 7714	李凯旋. 会泽超大型铅锌矿赋矿地层中泥质“脉体”的辨析[D]. 北京. 中国科学院研究生院,2014.

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