陕西省山阳县王家坪金矿床地质特征和成矿机制探讨

发布时间：2018-11-06 08:51

【摘要】：南秦岭山阳-柞水矿集区大地构造位于秦岭复合造山带东段北部晚古生代裂陷带中,构造带呈近东西向带状展布,构造演化复杂,岩浆活动强烈,王家坪金矿床位于山阳-柞水矿集区南界山阳-凤镇断裂以南,该区构造活动频繁,区内矿床组合复杂多样,王家坪金矿是该区少有的卡林型金矿。本文依托“十二五”国家科技支撑计划课题“陕西山阳-柞水矿集区斑岩铜钼金矿深部找矿模式及勘查技术集成与示范”,选择王家坪金矿床作为研究对象,开展了详细的地质调查,对其地质特征、岩矿石地球化学、H-O-S稳定同位素等进行研究。探讨了其成矿物质、成矿流体的来源与性质及其成矿机制。主要取得以下成果:(1)王家坪金矿赋存于区内泥盆系星红铺组中,控矿构造为东西向断裂,矿体主要沿破碎蚀变带分布,矿化类型为卡林型;矿石中黄铁矿、褐铁矿、雄(雌)黄等载金硫化物主要呈浸染状分布;其中主要载金矿物为黄铁矿;围岩蚀变以黄铁矿化、硅化、去碳酸盐化、雄(雌)黄化、毒砂化、碳化、泥化、铁碳酸盐化为主,局部可见辉锑矿化、黄铜矿化,矿区外围可见白钨矿化;主成矿阶段可分为三个矿化阶段:石英-方解石-黄铁矿阶段、方解石石英-金-多金属硫化物阶段、石英-方解石-雌黄-雄黄阶段。(2)通过对成矿期的流体包裹体测温工作,可知王家坪金矿包裹体均一温度为低温(100-120℃),成矿期盐度范围为15.96wt%NaCl。成矿期流体密度平均值为1.06g/cm~3,成矿压力范围平均值为133MPa。王家坪金矿的成矿深度为4.9km,矿床属于低温热液矿床。(3)黄铁矿稀土元素、微量元素测试结果显示:王家坪金矿不仅围岩、矿石稀土配分曲线型式及特征相似,且它们中黄铁矿的稀土元素配分曲线型式及特征及围岩与微量元素V、Sc“谷”和Co、Ni“峰”及整体曲线分配形式也较为相似,这指示围岩是主要的成矿物质来源。而微量元素中Y/Ho比值及Tl的异常高值,则指示来自壳幔深部的组分在成矿过程提供了部分成矿物质。(4)H-O同位素结合微量元素结果显示成矿流体在富Cl流体和富F流体性质之间的改变,指示在整个成矿阶段成矿流体具有多期演化特征。而S同位素的分布,则进一步证明成矿物质中有深源物质的加入。(5)综合区域资料并结合王家坪金矿地质特征,推断该矿床的成矿机制为:区域内的强烈的构造运动使围岩地层中原始分散状态的金不断活化迁移富集。地温及构造应力的增高,使沉积建造释放出大量的热脱水及地层封存水。这些流体在热与力的作用下沿构造空隙流动萃取围岩成矿物质,同时与由壳幔深部向地壳浅部移动的深源流体相混合,导致含矿热液物质成分受到地壳深部流体携带的物质混染并发生流体性质改变。最终,在大气降水参与下,含矿热液沿各级断裂渗流沉淀而成矿,形成现今的王家坪金矿。
[Abstract]:The tectonics of Shanyang-tussah Ore accumulation area in the South Qinling Mountains are located in the late Paleozoic rifting belt in the northern part of the Qinling complex orogenic belt. The tectonic belt is distributed in the near east-west direction, the tectonic evolution is complicated, and the magmatic activity is strong. The Wangjiaping gold deposit is located in the south of the Shanyang-Fengzhen fault in the southern boundary of Shanyang-tussah Ore concentration area, which is characterized by frequent tectonic activity and complex and diverse ore deposit assemblages. The Wangjiaping gold deposit is a rare Carlin type gold deposit in this area. Based on the "12th Five-Year Plan" of the National Science and Technology support Program, "the deep prospecting model and exploration technology of porphyry copper-molybdenum gold deposits in Shanyang-tussah Ore concentration area, Shaanxi Province", this paper selects the Wangjiaping gold deposit as the research object. The geological characteristics, geochemistry of rock and ore, and H-O-S stable isotopes are studied in detail. The source, properties and metallogenic mechanism of its ore-forming material, ore-forming fluid are discussed. The main achievements are as follows: (1) the Wangjiaping gold deposit occurs in the Xinghongpu formation of Devonian system, the ore-controlling structure is east-west fault, the orebody mainly distributes along the broken and altered zone, and the mineralization type is Carlin type; Pyrite, limonite, male (female) yellow and other gold bearing sulfides are mainly disseminated in ore, among which pyrite is the main gold bearing material. The main alteration of surrounding rock is pyrite, silicification, decarbonization, male (female) yellowing, arsenopyrite, carbonization, mudding, iron carbonization, local antimony mineralization, chalcopyrite, and scheelite mineralization in the periphery of the mining area. The main metallogenic stage can be divided into three stages: quartz calcite pyrite stage calcite quartz gold polymetallic sulfide stage. Quartz-calcite, realgar and realgar stage. (2) the homogenization temperature of inclusions in Wangjiaping gold deposit is low temperature (100-120 鈩，

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