安哥拉东北部地区Inkisi组碎屑锆石U-Pb年龄、地球化学特征及其地质意义  

U-Pb dating of detrital zircons and geochemical characteristics of Inkisi Formation in the northeastern Angola area

作　　者：李春稼 张洪瑞 罗迪柯 靳立杰 高继雷 王子圣 梁云汉 贾鹏飞 刘伟 张攀 LI Chunjia;ZHANG Hongrui;LUO Dike;JIN Lijie;GAO Jilei;WANG Zisheng;LIANG Yunhan;JIA Pengfei;LIU Wei;ZHANG Pan(No.1 Institute of Geology and Mineral Resource Exploration of Shandong Province,Ji’nan,250109;Shandong Engineering ResearchCenter of High-grade IronDeposits Explorationand Exploitation,Ji’nan,250109;Citic Construction Co.,Ltd.,Beijing,100027)

机构地区：[1]山东省第一地质矿产勘查院,济南250109 [2]富铁矿勘查开发技术山东省工程研究中心,济南250109 [3]中信建设有限责任公司,北京100027

出　　处：《地质论评》2024年第3期1031-1046,共16页Geological Review

基　　金：安哥拉国家地质调查计划项目(编号:PLANAGEO)的成果。

摘　　要：Inkisi组是刚果盆地西南缘最古老的沉积地层之一,岩性主要为一套紫红色、红褐色细粒、细中粒长石砂岩、杂砂岩。通过对安哥拉东北部Inkisi组长石砂岩开展碎屑锆石测年、岩石地球化学研究,探讨其沉积时代、物质来源、沉积环境和大地构造背景,为研究刚果盆地演化提供科学依据。结果表明,碎屑锆石^(206)Pb/^(238)U年龄主要集中于3个年龄峰值区间2350~1900 Ma、1150~850 Ma、850~500 Ma,最年轻的锆石峰值年龄为531±9 Ma,据此,笔者等认为Inkisi组的沉积时代上限应厘定为早寒武世。Inkisi组砂岩地球化学特征显示,物源具有长英质物源近源搬运特征,沉积时期的水体为陆相开阔的淡水环境。通过碎屑锆石年龄谱特征、主微量元素物源判别及构造判别图解,本文认为,West Congo构造带为安哥拉东北部地区Inkisi组主要物源区,Lufilian构造带、Angola地盾等是其次要物质来源,物源区构造环境主要为活动大陆边缘和被动大陆边缘构造环境背景。Objectives:The sedimentary age,material source,sedimentary environment and tectonic setting of the arkose of Inkisi Formation in northeast Angola are discussed through detritonal zircon dating and petrogeochemistry,which provide scientific basis for the study of the evolution of Congo Basin.Methods:We performed the zircon LA-ICP-MS U-Pb isotopic dating,major elements and trace elements compositions of the arkose from Inkisi Formation in northeastern of Angola.Results:The results show that the ^(206)Pb/^(238)U age of detrital zircon is mainly concentrated in three peak age ranges of 2350~1900 Ma,1150~850 Ma,and 850~500 Ma,with the youngest zircon having a peak age of 531±9 Ma.Conclusions:The upper limit of depositional age of Inkisi Formation in this area is the Early Cambrian.The geochemical characteristics of the sandstone of Inkisi Formation show that the provenance has the characteristics of near-source transport of felsic provenance,and the water in the sedimentary period was an open freshwater environment of continental facies.Based on the age spectrum of detrital zircon,source identification of major trace elements and structure identification diagram,the results show that the West Congo tectonic zone is the main provenance zone,followed by the Lufilian tectonic zone and Angola shield.The tectonic environment of its provenance area is mainly active continental margin and passive continental margin tectonic environment background.

关 键 词：碎屑锆石U-PB年龄 地层时代 岩石地球化学 Inkisi组 物质来源 安哥拉东北部 

分 类 号：P597.3[天文地球—地球化学] P548[天文地球—地质学]