陕西山阳—柞水矿集区龙头沟金矿矿床成因及地球动力学背景研究

发布时间：2018-05-08 05:41

  本文选题：成矿流体 + 成矿物质来源　； 参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：中秦岭弧前盆地系内的山阳-柞水矿集区内经历了古生代俯冲-增生造山作用和中生代碰撞造山作用,构造复杂,岩浆活动强烈,成矿地质条件优越。在该矿集区内存在一系列大中型金矿床,其中龙头沟金矿是区内规模最大的金矿床。本文选取龙头沟金矿作为研究对象,结合野外地质观察和室内研究工作,通过显微镜下观察,划分出不同成矿期次,并利用电子探针对不同阶段、不同种类的金属矿物进行成分分析,同时对流体包裹体进行测温并估算成矿流体的物理化学条件,并对石英和方解石进行C-H-O同位素及不同成矿阶段硫化物S同位素分析,并结合区域内构造演化特征,对该矿床的成因及其与该区地球动力学背景之间的联系进行了研究,取得如下主要认识:(1)矿床赋存在区内大枫沟组砂岩中,控矿构造为近东西向逆断层,矿体主要沿破碎蚀变带分布,矿化类型主要为破碎蚀变岩型,少量是石英脉型;主要载金矿物为黄铁矿,其次为黝铜矿;其成矿阶段可分为三个矿化阶段:石英-黄铁矿阶段、石英-金-多金属硫化物阶段、石英-方解石阶段;(2)通过对不同矿化阶段流体包裹体的显微测温工作,可知石英-黄铁矿阶段形成于160-200℃,成矿盐度为0.18-1wt%Na Cl;石英-金-多金属硫化物阶段形成于200-260℃,成矿盐度为1.5-4wt%Na Cl;石英-方解石阶段形成于120-180℃,成矿盐度为0.5-2wt%Na Cl。通过上述对比可以发现,从矿化的早阶段到晚阶段,成矿流体的温度逐渐降低,盐度逐渐降低。同时通过流体的显微测温,估算出矿床的成矿压力为140-200MPa,形成深度6.3-15.5km。(3)S同位素特征表明,龙头沟金矿床中硫来源为深部岩浆,成矿与幔源岩浆热液关系密切;C-O同位素特征则表明该矿床碳同位素来源属于地幔且受到海相碳酸盐岩地层的混染,说明成矿流体来自地幔且受到地层的混染;H-O同位素的特征则说明本区水的来源主要为大气降水,并有微弱的向岩浆水靠近的趋势;(4)综合区域资料并结合龙头沟金矿地质特征,在287.8±2.6Ma形成了山阳-凤镇大断裂及矿区褶皱,在此应力条件下,200.9±1.9Ma在褶皱的基础上形成切割其轴部的逆冲断层及其反冲断层(容矿构造),并在幔源岩浆的活动形成了龙头沟金矿床;(5)通过与世界典型造山型金矿各项特征的对比,可知其成矿特征在构造背景、赋矿地质体、控矿构造性质、蚀变矿物组合、矿石类型、主成矿温度、压力、盐度等方面有许多相似之处,属于造山型金矿。
[Abstract]:The Shanyang-tussah Ore concentration area in the Middle Qinling forearc basin has undergone the Paleozoic subduction-accretive orogeny and Mesozoic collision orogeny with complex structure strong magmatic activity and superior metallogenic geological conditions. There are a series of large and medium gold deposits in this area, among which the Longtougou gold deposit is the largest gold deposit in the area. In this paper, the authors select the Longtougou Gold Mine as the research object, combine the field geological observation and the laboratory research work, through the observation under the microscope, divide the different metallogenic times, and use the electronic exploration to aim at the different stages. The composition of different kinds of metallic minerals is analyzed, and the temperature of fluid inclusions is measured and the physicochemical conditions of ore-forming fluids are estimated. The C-H-O isotopes of quartz and calcite and S isotopes of sulphide in different metallogenic stages are also analyzed. Combined with the characteristics of tectonic evolution in the region, the origin of the deposit and its relationship with the geodynamic background of the area are studied. The main results are as follows: 1) the deposit occurs in the sandstone of the Dafenggou formation in the region. The ore-controlling structure is near east-west reverse fault, the orebody mainly distributes along the broken alteration zone, the mineralization type is mainly broken altered rock type, a few is quartz vein type, the main gold bearing material is pyrite, the next is tetrahedrite. The ore-forming stage can be divided into three stages: quartz-pyrite stage, quartz-gold-polymetallic sulfide stage, quartz-calcite stage, etc. It can be seen that the quartz-pyrite stage was formed at 160-200 鈩，

本文编号：1860179