东秦岭石瑶沟隐伏花岗岩成岩成矿作用

发布时间：2018-03-07 13:30

本文选题：斑岩钼矿　切入点：隐伏岩体　出处：《中国地质大学(北京)》2016年博士论文　论文类型：学位论文

【摘要】：石瑶沟大型钼矿床地处豫西地区华北板块南缘与秦岭褶皱带衔接部位的华熊地块。矿区隶属东秦岭钼矿带,该带汇集了南泥湖、上房沟、鱼池岭、东沟、雷门沟等一大批特大-大型钼矿床,是我国最重要的钼-金多金属成矿带。与该区其它斑岩型钼矿床产出形态不同,石瑶沟钼矿受控于一个未出露地表的隐伏花岗岩体,它的发现为东秦岭豫西地区斑岩型钼矿勘查评价提供了新的方向和典型工作区域。深入研究石瑶沟钼矿成岩成矿作用,有利于进一步完善东秦岭地区中生代斑岩型矿床成矿规律研究。在仔细地野外考察和钻探岩芯详细观察编录的基础上,本文利用通过镜下观察、地球化学分析测试、Rb-Sr同位素分析测试、岩浆岩LA-ICP-MS锆石U-Pb测年、Hf同位素特征以及H、O同位素测试研究等方法手段,研究石瑶沟隐伏花岗岩地球化学特征、岩浆源区、岩石成因、花岗岩演化过程等对钼矿化的制约因素。同时,通过石瑶沟钼矿特征与东秦岭地区典型大型-超大型斑岩钼矿特征进行对比研究,取得了如下认识和进展：(1)石瑶沟隐伏花岗岩年龄处于140.46±0.59 Ma～123.8±2.8 Ma,形成于早白垩世岩石圈伸展体制；近17Ma的年龄时差表明石瑶沟花岗岩具多期次活动特征,钼成矿主要与斑状花岗岩和花岗斑岩有关,成矿时代晚于成岩2-5Ma,成岩成矿处于同构造-岩浆地质背景中；含矿岩体为I-A过渡型高钾钙碱性系列-钾玄岩系列花岗岩,富集REE、Rb、 K、Nb、Ta、Pb、Nd、Zr、Hf等元素,亏损Eu、Sr、Ba、P、Ti等元素,具弱—中等Eu负异常；(2)石瑶沟钼矿含矿花岗岩具低εNd(t)(-13.96--13.10)、高TDM2(1.99-2.06)、高及宽泛的初始87Sr/86Sr比值(0.7077-0.7132)、低的εHf(t)值(介于-20.8-4.29,集中于-18.0-.6.8)和TDM2值(介于1.88-3.40 Ga,集中于1.88～2.18Ga),南秦岭地区早期岛弧俯冲形成的增生地壳、华北板块基底太华群等下地壳物质,受热的软流圈地幔底侵加热,发生部分熔融,从而形成石瑶沟花岗岩岩浆；(3)流体包裹体与稳定同位素显示,石瑶沟钼早阶段的成矿流体为高氧逸度、中高温、中低盐度、富CO_2的H_2O-NaCl-CO_2体系岩浆热液,成矿晚阶段为H_2O-NaCl体系热液,成矿深度为2.3～5.8km。成矿物质为古老下地壳物质,还有少量幔源物质的参与。(4)石瑶沟含矿隐伏花岗岩高硅富碱偏酸性、高分异、强氧化的特征,显示其具有较大的钼矿化潜力。本文的主要创新有,确定了石瑶沟钼矿含矿花岗岩为I—A过渡型花岗岩；将东秦岭豫西地区典型斑岩钼矿进行全面对比,探讨确定了限制矿种与规模的主要因素；总结提出了东秦岭豫西地区斑岩钼矿成岩成矿模式。总之,石瑶沟钼矿隐伏花岗岩体形成于中生代华北东部早白垩世岩石圈减薄、陆内伸展作用开始的构造背景下,形成深度大,产出Mo矿潜力巨大。
[Abstract]:The Shiyaogou large molybdenum deposit is located in the Huaxong block, where the southern margin of the North China plate and the Qinling fold belt join. The mining area belongs to the East Qinling molybdenum ore belt, which is a collection of South Nainihu, Shangfanggou, Yuchi Ridge and Donggou. A large number of mega-large molybdenum deposits, such as Remenggou, are the most important molybdenum and gold polymetallic metallogenic belts in China. Unlike other porphyry molybdenum deposits in this area, the Shiyaogou molybdenum deposit is controlled by a concealed granite body which is not exposed to the surface. Its discovery provides a new direction and a typical working area for the exploration and evaluation of porphyry molybdenum deposits in the western part of the East Qinling Mountains, and further studies on the diagenesis and mineralization of the Shiyaogou molybdenum deposit. It is beneficial to further improve the metallogenic regularity of Mesozoic porphyry deposits in the East Qinling area. On the basis of careful field investigation and detailed observation and cataloguing of drilling cores, this paper makes use of microscopic observation. Geochemical analysis, Rb-Sr isotopic analysis, LA-ICP-MS zircon U-Pb dating of magmatic rocks, HF isotopic characteristics of zircon U-Pb dating and Hau O isotopic measurements are used to study the geochemical characteristics, magmatic source and petrogenesis of the concealed granite in Shiyaogou. At the same time, the characteristics of Shiyaogou molybdenum deposit are compared with those of typical large and super-large porphyry molybdenum deposits in the East Qinling area. The results are as follows: (1) the age of Shiyaogou concealed granite is 140.46 卤0.59 Ma~123.8 卤2.8Ma, which was formed in the early Cretaceous lithospheric extensional system, and the time difference of nearly 17Ma indicates that the Shiyaogou granite has multi-stage activity characteristics. Molybdenum mineralization is mainly related to porphyry granite and granitic porphyry, the metallogenic age is 2-5 Ma later than that of diagenesis, and the diagenetic mineralization is in the same tectonic-magmatic geological setting. The elements such as REEN Rb, K ~ (+) Nb ~ (2 +) ~ TaPb ~ (2 +) ~ (2 +) ~ (2 +) ~ (2) ~ (2 +), etc. The ore-bearing granite of Shiyaogou molybdenum ore deposit has low 蔚 -Ndndtni-13.96- 13.10m, high TDM2U 1.99-2.06, high and broad initial 87s r-86Sr ratio 0.7077-0.7132U, low 蔚 Hftt) (between -20.8-4.29, concentrated in -18.0-.6.8) and TDM2 value (between 1.88-3.40 Ga, 1.882.18GaA and 1.882.18GaGaA). The accretive crust formed by the erosion, In the lower crust material such as Taihua Group, the basement of the North China plate, the heated asthenosphere mantle undergoes and partially melts, thus forming the Shiyaogou granite magma Yaogou granite.) fluid inclusions and stable isotopes are shown. The ore-forming fluid in early stage of Shiyaogou molybdenum is high oxygen fugacity, medium high temperature, low salinity, CO_2 rich H2O-NaCl-CO2 system magmatic hydrothermal fluid, late metallogenic stage is H _ 2O-NaCl system hydrothermal fluid, ore-forming depth is 2.3 ~ 5.8km.The ore-forming material is ancient lower crust material. There is also a small amount of mantle-derived material involved. (4) Shiyaogou ore-bearing concealed granite with high silicon-rich alkali-rich partial acidity, high differentiation, strong oxidation, which shows that it has great potential for molybdenum mineralization. The main innovations in this paper are, The ore-bearing granites of Shiyaogou molybdenum deposit are determined to be I-A transitional granites, the typical porphyry molybdenum deposits in the western part of East Qinling are compared comprehensively, and the main factors limiting the type and scale of ore are discussed. The porphyry molybdenum ore-forming model in the eastern Qinling and western Henan regions is summarized. In short, the concealed granite body of the Shiyaogou molybdenum deposit was formed in the tectonic setting of the early Cretaceous lithosphere thinning in the eastern part of Mesozoic and the beginning of intracontinental extension. The formation depth is large and the potential for producing Mo ore is great.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P611

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