栾川矿集区南泥湖与上房沟钼多金属矿床成岩成矿特征对比研究

发布时间：2018-07-03 13:57

本文选题：南泥湖 + 上房沟　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：东秦岭钼多金属成矿带位于秦岭造山带东端,是世界最重要的钼矿带之一,南泥湖钼钨矿床和上房沟钼铁矿床是东秦岭钼矿带两个典型的超大型矿床,都属于斑岩-矽卡岩型矿床。两个矿床的成岩成矿年龄基本一致(燕山中期),且地理位置相近,然而两个矿床的伴生矿种却显著不同,一个为钼钨矿床,一个为钼铁矿床。为此本文试图通过对比两个矿床的矿床地质特征、围岩性质、岩石地球化学特征以及矿床地球化学特征,总结分析其成岩成矿的共性特征和差异特征,分析差异来源,为日后东秦岭勘探提供参考。对比研究取得以下几点认识成果:两个矿床主要成矿期都为燕山中期。燕山期岩浆活动为该区多钼钨多金属成矿提供了热液和矿物质来源,矿床在成因上与构造、岩体、围岩及其蚀变密切相关。南泥湖岩体和上房沟岩体均具有高硅、富碱的特征,均具有明显的Eu负异常,分异演化强烈。稀土和稀有元素显示两个岩体具有后造山花岗岩、同碰撞和后碰撞花岗岩过渡特征。稀有元素、锶、钕同位素指示岩体来源为壳幔混源。黑云母成分特征显示岩体形成时氧逸度和温度较高,形成的深度为中浅成。两个矿床的硫、碳氧、氢氧和铅同位素及铼含量特征表明两个矿床的钼钨成矿物质都是岩体由深部带来,成矿流体与斑岩关系密切,后期可能有地层物质和大气降水的加入。流体包裹体都富集CO2,都经历从高温到低温的演化。两个矿床的差异性主要体现在:1)南泥湖主要伴生矿种为W,而上房沟主要伴生Fe;2)南泥湖矿床的成矿母岩是黑云母二长花岗岩,上房沟则为碱长花岗斑岩;3)南泥湖围岩相对富镁,主要发育钙矽卡岩化、钾交代等蚀变,上房沟围岩相对富钙,主要发育镁矽卡岩化、钾交代和硅交代等蚀变作用。决定两个矿床伴生矿种差异的是围岩性质。上房沟的铁矿为接触交代型(矽卡岩型),通过钠交代作用和成岩成矿温度氧逸度的横向对比,判断岩浆源并非上房沟单一的铁质来源,根据蚀变过程中主要组分变化曲线图,推测铁质来源可能为变辉长岩。
[Abstract]:The east Qinling molybdenum polymetallic metallogenic belt is located at the eastern end of the Qinling orogenic belt and is one of the most important molybdenum ore belts in the world. The South Nihu molybdenum tungsten deposit and Shangfanggou molybdenum iron deposit are two typical superlarge deposits in the east Qinling molybdenum ore belt. All belong to porphyry-skarn type deposit. The diagenetic and metallogenic ages of the two deposits are basically the same (the middle Yanshanian period) and the geographical location is similar. However, the associated ore types of the two deposits are obviously different, one is molybdenum tungsten deposit and the other is molybdenum iron deposit. For this reason, this paper attempts to summarize and analyze the common and differential characteristics of diagenesis and metallogenesis by comparing the geological characteristics, surrounding rock properties, rock geochemistry characteristics and deposit geochemical characteristics of the two deposits, and analyzes the source of the differences. It provides a reference for the exploration of the East Qinling Mountains in the future. The results are as follows: the main metallogenic period of the two deposits is the middle Yanshanian period. Yanshanian magmatic activity provided hydrothermal and mineral source for polymolybdenum and tungsten polymetallic mineralization in this area. The ore deposit is closely related to structure, rock mass, surrounding rock and its alteration in origin. Both the Nannihu and Shangfanggou rock bodies are characterized by high silicon and alkali, obvious negative EU anomalies and strong differentiation and evolution. The REE and REE show that the two intrusions have the characteristics of post-orogenic granite, syncollision and post-collisional granite transition. Rare elements, strontium and neodymium isotopes indicate that the source of the rock mass is crust and mantle mixing. The composition characteristics of biotite show that the oxygen fugacity and temperature are high and the depth of formation is medium and shallow. The characteristics of sulfur, carbon, oxygen, hydrogen, oxygen and lead isotopes and rhenium contents in the two deposits indicate that the molybdenum and tungsten ore-forming minerals in the two deposits are all brought by the deep rock mass, and the ore-forming fluid is closely related to porphyry, and there may be stratigraphic material and atmospheric precipitation in the late stage. Fluid inclusions are rich in CO _ 2 and have evolved from high temperature to low temperature. The difference between the two deposits is mainly reflected in: (1) the main associated minerals in Nanni Lake are W, while in Shangfanggou are associated with Feji2) the ore-forming mother rock of Nannihu deposit is biotite monzogranite, and Shangfanggou is alkali-feldspar porphyry 3) the surrounding rock of Nanjihu Lake is relatively rich in magnesium. There are mainly calcium-skarn alteration, potassium metasomatism and other alteration. The surrounding rock of Shangfanggou is relatively rich in calcium, and mainly developed magnesia-skarn, potassium metasomatism and silicon metasomatism. It is the nature of surrounding rock that determines the difference of the associated minerals between the two deposits. The iron ore in Shangfanggou is of contact metasomatic type (skarn type). Through the lateral comparison of sodium metasomatism and the oxygen fugacity of the ore-forming temperature, it is determined that the magmatic source is not a single iron source in Shangfanggou. It is speculated that the source of iron may be metamorphic gabbro.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.2

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