摘要
锡铁山铅锌矿床是我国西北地区大型铅锌矿床之一,但是,有关其成矿时间问题一直缺乏较好约束。本文通过对靠近矿体底部的火山岩LA-ICPMS锆石U-Pb定年,获得了三组锆石U-Pb谐和年龄,分别变化于500~470 Ma,465~450 Ma和440~420 Ma,形成的三个权重平均年龄分别为(479.4±5.2)Ma,(455.5±6.1)Ma和(431.8±3.7)Ma。结合区域滩间山群成岩构造环境及矿床成矿构造背景,文章认为前两组权重平均年龄代表了早古生代滩间山群两期强烈火山作用的峰期年龄,其年龄跨度(500~455 Ma)代表了滩间山群岛弧火山作用的时间跨度。第三组权重平均年龄代表了滩间山群火山岩成岩之后区域造山事件的主期变质年龄。锡铁山海底喷流沉积成矿合理时间应在455 Ma左右。
Xitieshan Pb-Zn deposit is one of the large-scale Pb-Zn deposits discovered in Northwest China.However,the submarine exhalative sedimentary mineralization timing has been lacking the reliable age constraint.LA-ICPMS zircon U-Pb dating work is carried out with the volcanic sample near the bottom of orebody and three groups of apparent concordant ages,ranging from 500-470 Ma,465-450 Ma,and 440-420 Ma are obtained and there are three weighted average ages of(479.4±5.2)Ma,(455.5±6.1)Ma,and(431.8±3.7)Ma,respectively.With the combination of the regional rock-forming environment and metallogenic tectonic setting,the former two weighted average ages are considered to represent two times of intensive volcanism occurring in the early Paleozoic,the age span from 500 Ma to 450 Ma represents the time span of island arc volcanism of Tanjianshan Group.The third weighted average age represents the main metamorphic age of regional orogenic events after the diagenesis of volcanic rocks in Tanjianshan Group.Therefore,the reasonable time for the submarine exhalative sedimentary mineralization should be around 455 Ma.
作者
赵立军
张倩慧
ZHAO Lijun;ZHANG Qianhui(Library of China University of Geosciences,Wuhan 430074,Hubei,China;School of Resources,China University of Geosciences,Wuhan 430074,Hubei,China)
出处
《矿产与地质》
2023年第1期79-85,107,共8页
Mineral Resources and Geology
基金
国家自然科学基金(41172087)
西部矿业地质科研项目共同资助。
