四川省若尔盖铀矿田含铀煌斑岩地球化学特征及其与铀成矿的关系  

Geochemical Characteristics of Uranous Lamprophyre and Its Relation to Uranium Mineralization in Ruo’ergai Uranium Ore Field,Sichuan

作　　者：黄小昆 徐争启[1,2,3] 李宝新 尹明辉[1,3] 王永飞[4] HUANG Xiaokun;XU Zhengqi;LI Baoxin;YIN Minghui;WANG Yongfei(Key Laboratory of Earth Exploration and Information Technology,Ministry of Education,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Geosciences and Nuclear Technology of Sichuan Province,Chengdu,Sichuan 610059,China;College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Sichuan Institute of Uranium Geological Survey,Chengdu,Sichuan 610061,China)

机构地区：[1]成都理工大学地球勘探与信息技术教育部重点实验室,四川成都610059 [2]地学核技术四川省重点实验室,四川成都610059 [3]成都理工大学地球科学学院,四川成都610059 [4]四川省核工业地质调查院,四川成都610061

出　　处：《铀矿地质》2023年第3期406-417,共12页Uranium Geology

基　　金：国家自然科学基金项目“康滇地轴粗粒晶质铀矿标型特征及形成机理”(编号:41872079);中国核工业地质局科研项目“康滇地轴铀成矿环境及选区研究”(编号:202137-3);四川省政府性投资地质勘查项目(编号:DZ202101,2021554,2022324);四川省地质调查院科技创新项目(编号:2022262)联合资助。

摘　　要：若尔盖铀矿田位于秦岭褶皱系西段,西秦岭褶皱带之南亚带。近年来,在若尔盖地区发现了富铀的煌斑岩脉,目前富铀煌斑岩脉与区内铀成矿的关系尚不明确,研究这些富铀的煌斑岩脉对于若尔盖地区深部找矿具有重要意义。在前人研究的基础上,文章对富铀煌斑岩的地球化学特征进行综合分析,探究煌斑岩脉的成因及其与铀成矿的联系。元素地球化学特征分析结果表明研究区内煌斑岩来源于上地幔源区,在其侵入到上部岩层的过程中存在地壳物质的混染作用,并且受到了后期热液的叠加改造。研究区煌斑岩为幔源、地壳物质混染以及后期热液叠加改造共同作用的结果。此外,煌斑岩w(Na_(2)O)、w(K_(2)O)值均低于2%,而烧失量达到了18.39%~31.45%,且在偏光镜下观察到样品中主要的矿物为云母和碳酸盐矿物,煌斑岩发生了强烈的碳酸盐化。煌斑岩中铀含量与碳酸盐化呈正相关关系,表明煌斑岩发生碳酸盐化时会促进煌斑岩中铀的富集。这些富铀的煌斑岩在空间上与区内铀矿的产出位置接近,煌斑岩与区内的铀成矿作用关系密切。研究认为煌斑岩可以为区内铀成矿提供含矿热液运移通道以及地球化学障等有利成矿的必要条件。Uranium deposit in Ruo􀆳ergai is located in western Qinling fold system,and south subzone of western Qinling folding belt.In recent years,U-rich lamprophyre dikes have been discovered in Ruo’ergai area.At present,the relationship between lamprophyre dikes and uranium mineralization is not clear.Therefore,the study of uranium-rich lamprophyre dikes is of great significance for the further uranium exploration in Ruo􀆳ergai area.Based on the previous studies,we comprehensively analyzed the geochemical characteristics of uranium-rich lamprophyre,and explored the genesis of lamprophyre dike and its relationship with uranium mineralization.The analysis of lamprophyre element geochemical characteristics showed that the lamprophyre was originated from the upper mantle source.During intruding process of lamprophyre into the upper strata,there existed the intermingling of crustal materials,and it was overlaid by late hydrothermal transformation.The lamprophyre is the product of the interaction of mantle source,crustal material mixing and hydrothermal superimposition.Na_(2)O and K_(2)O in lamprophyres are lower than 2%,LOI reach to 18.39%~31.45%,and the main minerals are mica and carbonate under microscope,which suggest the lamprophyres experienced intense carbonation.There is a positive correlation between uranium content in lamprophyres and alteration,and the alteration may promote the pre-enrichment of uranium in lamprophyres.Those uranium-enriched lamprophyres are spatially close to the carbonaceous siliceous-argillaceous type uranium deposits.Therefore the lamprophyres may be closely related to the mineralization of the carbonaceous-siliceous-argillaceous type uranium deposits.It was believed that the lamprophyres can act as hydrothermal migration channels and geochemical barriers for uranium mineralization in this zone.

关 键 词：煌斑岩 碳酸盐化 地球化学 成因联系 若尔盖铀矿田 

分 类 号：P588.124[天文地球—岩石学] P595[天文地球—地质学]