西秦岭火麦地印支期斑岩铜钼矿床成矿机制

发布时间：2018-06-29 19:02

  本文选题：矿床地质特征 + 岩石成因　； 参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：火麦地铜钼矿床位于北祁连造山带与西秦岭造山带的交接处,是西秦岭北缘一个重要的斑岩型矿床。本文对火麦地铜钼矿床地质-地球化学特征进行了详细研究,查明了矿床空间展布特征和矿化-蚀变类型,厘清了成矿期的热液脉体阶段,查明了含矿斑岩岩石地球化学特征,测定了成岩-成矿时代,探讨了含矿斑岩成因与成矿流体特征、成矿物质来源及矿床成矿机制。1、矿床东、西区矿体产出部位不同。东区矿体主要产出于斑岩体外接触带蚀变石英砂岩地层中;西区矿体主要产出于凝灰质角砾岩及外接触带附近地层中。以脉状、扁豆状为主,总体走向310°~330°,倾向SW或NE,倾角在不同部位有所变化。钾化带、石英绢云母化带、泥化带、青盘岩化带由内而外呈面状分布,矿化主要集中产出于石英绢云母化带中。2、根据脉体切割关系及矿物共生组合可将岩浆-热液网脉划分为3大类,从早到晚分别为:粒状石英-钾长石-黑云母-少量黄铁矿脉(A脉);石英-黄铜矿-辉钼矿-黄铁矿-闪锌矿脉(B脉);黄铁矿-石英-少量黄铜矿脉(D脉)。3、H-O-S同位素测试结果显示δ18OH2O值为8.6~13.6‰,δDH2O值为-50~-85‰,δ34S值为0.02‰~5.9‰,表明成矿流体主要来源于晚三叠世花岗质岩浆在结晶分异过程中产生的岩浆热液,后期有大气降水加入。4、含矿石英闪长斑岩、二长斑岩、石英二长斑岩均属于高钾钙碱性的准铝质-过铝质岩石系列,富集大离子亲石元素,亏损Nb、Ta、Zr、Hf、Ti等高场强元素;εHf(t)值为 2.4~+6.1,TDM2=0.78 1.25 Ga;含矿斑岩的锆石U-Pb年龄为215.0±5.8 Ma至226.6±6.2 Ma,代表了斑岩体的侵位年龄;矿石辉钼矿Re-Os等时线年龄为208.5±1.3Ma,代表成矿年龄,成矿作用近于同时或者稍晚于岩体侵位年龄。结合西秦岭造山带大地构造演化历史研究,含矿斑岩地球化学特征、成岩成矿年龄表明:同碰撞向后碰撞构造体制转换(减压增温)时期古老下地壳部分熔融并有地幔物质加入形成的岩浆携带成矿物质沿断裂带上侵,冷凝分异出溶的成矿流体携带Cu、Mo、S等元素沿裂隙运移、充填和交代围岩形成该矿床。综上所述,西秦岭火麦地铜钼矿床形成于印支期华北和华南板块碰撞造山过程中,是典型的碰撞造山环境斑岩型矿床。
[Abstract]:Huomaidi Cu-Mo deposit is located at the junction of North Qilian orogenic belt and West Qinling orogenic belt and is an important porphyry deposit in the northern margin of West Qinling Mountains. In this paper, the geological and geochemical characteristics of Huomaidi copper-molybdenum deposit are studied in detail. The spatial distribution characteristics and mineralization-alteration types of the deposit are found out, the hydrothermal vein stage in the metallogenic period and the geochemical characteristics of the porphyry rocks in the ore-bearing period are clarified. The diagenetic and metallogenic ages are determined, and the genesis and ore-forming fluid characteristics of ore-bearing porphyry, the source of ore-forming material and the metallogenic mechanism of the deposit are discussed. The eastern ore body is mainly formed in the porphyry external contact zone alteration quartz sandstone strata and the western part is mainly produced in the tuffaceous breccia and the strata near the outer contact zone. The veins and lentils were dominant, and the general trend was 310 掳or 330 掳, which tended to SW or NE.The inclination changed in different parts. The kalitization zone, the quartz sericite zone, the mudding zone and the Qingpan lithochemical zone are distributed in a plane form from inside to outside. Mineralization is mainly concentrated in the quartz sericite belt. According to the vein cutting relationship and mineral symbiosis association, magma hydrothermal network veins can be divided into three categories. From early to late, they are: granular quartz-potassium feldspar-biotite-a small amount of pyrite vein (vein A); quartz-chalcopyrite-molybdenum-pyrite-sphalerite vein (B); pyrite-quartz-small amount of brass vein (D vein). The values of 未 18 O H 2O, 未 D H 2O and 未 34S are 8.6N 13.6 鈥，

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