大兴安岭南段北三段矿区地质地球化学特征及找矿预测

发布时间：2018-02-11 14:01

  本文关键词： 大兴安岭南段 北三段矿区 地球化学 稳定同位素 找矿预测　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：大兴安岭南段位于中亚造山带的东段,古亚洲洋、蒙古-鄂霍茨克洋和古太平洋构造-成矿域的叠加部位,构造位置特殊,发现有丰富的金属矿产资源。北三段矿区是大兴安岭南段西部的一个多金属矿区。本文通过野外调查、地球化学分析、稳定同位素、流体包裹体研究,结合区域地质背景及区域成矿特点,对北三段矿区成矿流体来源、成矿物质来源进行研究,进而进行找矿前景分析。地球化学化学特征表明,北三段矿区出露花岗岩岩脉为A型花岗岩,其形成环境为碰撞造山后伸展环境。煌斑岩脉超钾质煌斑岩类,其Si O2含量为41.09~41.47%,表明来源于地幔,而Ta/La值远低于原始地幔值,表明其可能存在地壳物质的参与。辉绿岩脉的Mg O、Cr、Ni、(Tb/Yb)N值均低于原始地幔值,指示其源区不是原生岩浆,而是结晶分异作用的尖晶石橄榄岩岩浆;其La/Yb1.2、La/Ta大于22,Ti O2为0.93~1.20%,远低于软流圈玄武质岩浆的平均值,表明其主要来源于岩石圈地幔。碳、氧同位素表明北三段矿区成矿流体来源为地幔岩浆,后期受到大气降水的影响,成矿流体为大气降水、岩浆水的混合;氢氧同位素特征亦表明北三段成矿流体同时受岩浆水及大气降水影响,大气降水的参与从成矿流体出溶后就开始了。北三段矿区的硫同位素变化范围为-0.24‰~2.37‰,均值为1.29‰,极差、标准差小,变化范围狭窄,与大兴安岭南段金属矿床的硫同位素特征相似,表明硫来源于深源岩浆。在208Pb/204Pb-206Pb/204Pb和207Pb/204Pb-206Pb/204Pb图解中,北三段样品基本落在下地壳、上地幔和造山带铅的演化线附,且基本排列为一条直线,表明它们来源于同一岩浆源区,成矿物质由造山带物质和地幔物质两部分提供。北三段矿区与邻区大井矿床具有一定的相似性,其硫铅同位素特征基本一致,表明其具有相同的成矿物质来源;而其碳氢氧同位素特征相似表明其具有相同的成矿流体来源,是同一体系不同条件形成的不同矿床,均为热液型矿床。北三段矿区脉岩多为浅成侵入岩,大井矿床多为中酸性喷出岩,从成矿温度来看,大井矿床比本区成矿温度高,结合区域大地构造背景,北三段深部地区可能存在大井矿床类似的铜多金属矿床。矿区内北西向断裂发育区域及脉岩出露区域亦为找矿有利部位。
[Abstract]:The southern part of the Daxing'anling Mountains is located in the eastern part of the Central Asian orogenic belt, the Paleo-Asian Ocean, the Mongolia-Okhotsk Ocean and the paleo-Pacific tectonic-metallogenic region. It is found that there are abundant metal mineral resources. The northern third section is a polymetallic mining area in the west of Daxinganling Mountains. Through field investigation, geochemical analysis, stable isotopes and fluid inclusions, Combined with the regional geological background and regional metallogenic characteristics, the source of ore-forming fluid and ore-forming material in the third section of the northern part of China is studied, and the prospect of prospecting is analyzed. The geochemical and chemical characteristics show that, The outcropping granite veins in the Beisanjie mining area are A-type granites and formed in a post-collisional extensional environment. The ultrapotash lamprophyres of the lamprophyre veins have a Sio _ 2 content of 41.09 ~ 41.47, indicating that they originated from the mantle, while the Ta/La value is much lower than the original mantle value. The results indicate that there is a possible involvement of crustal material in the diabase veins, and the mg _ O _ O _ Cr-Ni _ (B) T _ (b / Y) N values of the diabase veins are all lower than the original mantle values, indicating that the source region is not primary magma, but the spinel peridotite magma of crystallization differentiation. The La- / Yb _ (1.2) / Ta ~ (-1 / Ta) is 0.93 / 1.20, which is far lower than the average value of the asthenospheric Black Tortoise magma, which indicates that the ore forming fluid in the third member of the northern ore area is derived from mantle magma, which is influenced by the atmospheric precipitation in the later stage, and the carbon and oxygen isotopes indicate that the ore-forming fluid of the northern third member ore area is derived from mantle magma. The ore-forming fluid is the mixture of magmatic water and meteoric water, and the hydrogen and oxygen isotopic characteristics also indicate that the ore-forming fluid in the northern third member is affected by both magmatic water and atmospheric precipitation. The participation of atmospheric precipitation begins after the ore-forming fluid dissolves. The range of sulfur isotopic variation in the North third member mining area is -0.24 鈥，

本文编号：1503226