北秦岭东段宽坪岩体地质地球化学特征及其与铀成矿关系  

Geological and Geochemical Characteristics of the Kuanping Granite in the Eastern Section of North Qin Ling and their Relationship with Uranium Mineralization

作　　者：王江波[1,2] 赖绍聪[1] 李卫红 胡渭平 

机构地区：[1]西北大学地质学系,陕西西安710069 [2]核工业二〇三研究所,陕西咸阳712000

出　　处：《地质与勘探》2015年第1期98-107,共10页Geology and Exploration

基　　金：中国核工业地质局铀矿地质项目(项目编码:201351);中国地质调查局地质调查项目(项目编码:1212011120567;1212011220375)联合资助

摘　　要：北秦岭东段宽坪岩体受南北两侧区域性大断裂控制,呈狭窄带状展布,岩石地质地球化学特征具I型花岗岩的特征。铀矿化产于宽坪岩体与丹凤岩群内外接触带及内部构造角砾岩带内,具有强烈的热液蚀变。铀成矿年龄集中在140~90 Ma,铀矿化产出部位距K-E盆地不到10 km,岩体内部发育大量晚期煌斑岩脉,显示铀矿化与区域拉张事件密切相关。铀矿化从弱到强,HREE逐渐增高,显示HREE与铀的迁移具有同步性。岩(矿)石微量元素蛛网图基本一致,富集Rb、Th、U、La、Ce、Nd,亏损Ba、Sr、P、Ti等,与华南产铀花岗岩特征类似。Y/Ho变化范围狭窄(26.50~31.86),暗示成矿物质主要来源宽坪岩体本身。岩石类型(I型或S型)及岩体铀含量的高低不是铀成矿能力的决定因素,强烈的构造改造和热液蚀变作用,叠加富CO2流体的搬运作用使岩石中的铀沉淀富集成矿。The Kuanping granite in the eastern section of North Qin Ling shows a tectonic control by two regional faults on its south and north sides,and thus exhibits a narrow banded extension. The rocks of the Kuanping granite belong to the type-I one. Uranium mineralization mainly occurs in the inner-and outer-contact zones of the Kuanping granite with the Danfeng rock group and endo-tectonic breccia belt,and has strong hydrothermal alternation. The ages of uranium mineralization are largely between 140 ~ 90 Ma,less than 10 km distant from the K-E basin. Within the granite formed lots of late lamprophyres,which show that uranium mineralization is closely related with the regional extensional events. HREE gradually increases when uranium mineralization gets stronger,which indicates that the migration of HREE and uranium migration were synchronous. The spider diagrams of trace elements from rocks and uranium ores are generally the same,with an enrichment of Rb,Th,U,La,Ce and Nd,a depletioin of Ba,Sr,P and Ti. This characteristic is very similar to that of uranium-bearing granite in South China. The narrow range of Y / Ho ratios between 26. 50 ~ 31. 86 indicates that metallogenic materials mainly originate from the Kuanping granite. The scale of geochemical rock type( I-type or S-type) and uranium content of rock itself is not the deciding factor of uranium mineralization capacity. A strong affection of structure and hydrothermal alteration coupled with CO2-riched fluid transportation resulted in uranium precipitate and enrichment to form ores.

关 键 词：地质特征 地球化学 宽坪岩体 北秦岭 

分 类 号：P619.14[天文地球—矿床学]