赞比亚伊索卡南部Kachinga长石砂岩碎屑锆石U-Pb年龄、地球化学特征及地质意义  

The detrital zircon U-Pb age,geochemical characteristics,and their geological implications for the Kachinga feldspar sandstone in southern Isoka,Zambia

作　　者：杜明龙[1] 纪山青 任军平[2] 王杰[2] 刘子江 邢仕 刘川[1] 韦文国[1] DANIEL Malunga PETER Chipumbu ABRAHAM Mukangwa CHISAMBA Mwansa DU Minglong;JI Shanqing;REN Junping;WANG Jie;LIU Zhijiang;XING Shi;LIU Chuan;WEI Wenguo;DANIEL Malunga;PETER Chipumbu;ABRAHAM Mukangwa;CHISAMBA Mwansa(Bureau of Geologic Exploration and Mineral Development of Hebei Province,Tangshan,Hebei,063000,China;Tianjin Geological Survey Center of China Geological Survey,Tianjin,300170,China;Geological Survey Department of Zambia,Lusaka,P.O.Box 50135,Zambia)

机构地区：[1]河北省地矿局第五地质大队,中国河北唐山163000 [2]中国地质调查局天津地质调查中心,中国天津300170 [3]赞比亚地质调查局,赞比亚卢萨卡P.O.Box50135

出　　处：《地质学报》2021年第4期1050-1071,共22页Acta Geologica Sinica

基　　金：商务部技术援外项目([2015]352和[2012]558);中国地质调查局项目(编号DD20201150和1212011220910)资助的成果。

摘　　要：赞比亚东北部伊鲁米德带是一个北东向延伸的中元古代构造活动带,起自赞比亚中部,向北东一直延伸至赞比亚-坦桑尼亚边境,并进入马拉维北部;其东北部以古元古代乌本迪构造带为界;西北部以班韦乌卢地块为界;西部和西南部受新元古代的达马拉-卢菲利安弧-赞比西构造事件的影响。Kachinga长石砂岩位于伊鲁米德带的东北部伊索卡南部。本文获得Kachinga长石砂岩的416颗碎屑锆石U-Pb年龄多集中在1749±25~1920±23Ma之间,Kachinga长石砂岩的形成时代可能晚于1331±26Ma,属于中元古代。Kachinga长石砂岩碎屑锆石CL图像表明,大部分锆石为岩浆结晶锆石,少部分锆石颗粒为增生-混合型锆石,表明其经历了多期构造-热事件的改造。锆石中存在有一部分磨圆度较好的颗粒,表明其经历了多次搬运和沉积过程,从而指示了古老沉积岩为Kachinga长石砂岩提供了物源。主量元素、微量元素和稀土元素构造环境判别及物源分析表明了Kachinga长石砂岩物源主要为上地壳大陆长英质源区,并且可能混有古老沉积物成分,物源区构造背景为大陆岛弧环境。The Irumide belt of northeastern Zambia is a northeast-trending structural province stretching from central Zambia to the Zambia-Tanzania border and northern Malawi.The Mesoproterozoic and Neoproterozoic transcurrent shear zones which reactivated the Palaeoproterozoic Ubendian belt define its northeastern limit.The northwestern margin is defined by the Bangweulu block.To the west and southwest,the Irumide were reworked by the Neoproterozoic Damara-Lufifilian-Zambezi Orogen.The Kachinga feldspar sandstone is located near the Isoka in the northeastern part of the Irumide belt.This paper systematically studied the geological characteristics,U-Pb isotope and geochemical characteristics of the Kachinga feldspar sandstone in the Isoka area.The 416 U-Pb ages of the detrital zircons in the Kachinga feldspar sandstone are mostly concentrated between 1749±25~1920±23 Ma indicating that the formation age of the Kachinga feldspar sandstone may be later than 1331±26 Ma,which belongs to Mesoproterozoic.The Kachinga feldspar sandstone detrital zircons show that most of them are magmatic crystalline zircons,and a small amount of zircon particles are accretionary-hybrid zircons,indicating that they have undergone multi-phase tectonic-thermal events.There are some well rounded zircon particles indicating multiple transportation and deposition processes suggesting that the ancient sedimentary rocks were a source for the Kachinga feldspar sandstone.The tectonic environment identification and provenance analysis of major,trace elements and rare earth element indicate that the source of the Kachinga feldspar sandstone is mainly the felsic source area of continental upper crust and may have been mixed with ancient sediments.The structural background of the source area is continental island arc surroundings.

关 键 词：碎屑锆石U-PB年龄 地球化学特征 物源分析 Kachinga长石砂岩 伊鲁米德带 赞比亚 

分 类 号：P59[天文地球—地球化学] P588.21[天文地球—地质学]