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引用本文:任军平,王杰,孙宏伟,冯琳,左立波,古阿雷,贺福清,CHIPILAUKA Mukofu,ALPHET PHASKANI Dokowe,EZEKIAH Chikambwe,CHIWSHIMBA Canisius,DANIEL Malunga. 赞比亚东北部卡萨马群形成环境:碎屑锆石U-Pb年龄与Hf同位素的限定[J]. 中国地质, 2019, 46(3): 575-586.
REN Junping,WANG Jie,SUN Hongwei,FENG Lin,ZUO Libo,GU Alei,HE Fuqing,CHIPILAUKA Mukofu,ALPHET PHASKANI Dokowe,EZEKIAH Chikambwe,CHIWSHIMBA Canisius,DANIEL Malunga. Depositional environment of the Kasama Group, northeastern Zambia: Evidence from detrital zircon U-Pb-Hf isotopic compositions[J]. Geology in China, 2019, 46(3): 575-586(in Chinese with English abstract).
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赞比亚东北部卡萨马群形成环境:碎屑锆石U-Pb年龄与Hf同位素的限定
任军平1, 王杰1, 孙宏伟1, 冯琳2, 左立波1, 古阿雷1, 贺福清1, CHIPILAUKA Mukofu3, ALPHET PHASKANI Dokowe3, EZEKIAH Chikambwe3, CHIWSHIMBA Canisius3, DANIEL Malunga3
1.中国地质调查局天津地质调查中心, 天津 300170;2.贵州省地质资料馆, 贵州 贵阳 550002;3.赞比亚地质调查局, 赞比亚 卢萨卡 P. O. Box 50135
摘要:
赞比亚东北部班韦乌卢地块受到其东北部的古元古代乌本迪构造带、西北部的中元古代基巴拉构造带、东南部的中元古代伊鲁米德构造带及西南部泛非期卢弗里安构造带的影响。班韦乌卢地块主要由基底和沉积盖层两部分组成。其中,基底主要由片岩带、安山质-流纹质变质火山岩、花岗岩类岩基及其他侵入体组成。沉积盖层从老至新依次为姆波罗科索群、卡萨马群、加丹加超群及新生代的河流相和湖泊相沉积。本文对卡萨马地区的卡萨马群地质特征、碎屑锆石U-Pb-Hf同位素及地球化学特征进行了系统研究,获得卡萨马群中紫红色粉砂岩的32颗碎屑锆石U-Pb年龄多集中在(1849±23)~(1993±21)Ma,卡萨马群的形成时代可能晚于(1434±14)Ma,属于中元古代,其中22颗锆石(176Hf/177Hf)i为0.281049~0.281618,εHft)为-12.8~-1.6,二阶段模式年龄变化范围为2406~3487 Ma。对卡萨马群的砂岩进行了稀土元素分析和微量元素分析,结果显示卡萨马群砂岩δEu负异常明显,投点主要落在沉积岩区;微量元素显示砂岩形成于被动大陆边缘环境。
关键词:  卡萨马群  碎屑锆石U-Pb-Hf同位素  稀土元素和微量元素  班韦乌卢地块  赞比亚东北部
DOI:10.12029/gc20190309
分类号:P597
基金项目:中国地质调查局项目(1212011220910、121201006000150014)和商务部技术援外项目([2012]558、[2015]352)共同资助。
Depositional environment of the Kasama Group, northeastern Zambia: Evidence from detrital zircon U-Pb-Hf isotopic compositions
REN Junping1, WANG Jie1, SUN Hongwei1, FENG Lin2, ZUO Libo1, GU Alei1, HE Fuqing1, CHIPILAUKA Mukofu3, ALPHET PHASKANI Dokowe3, EZEKIAH Chikambwe3, CHIWSHIMBA Canisius3, DANIEL Malunga3
1.Tianjin Geological Survey Center of China Geological Survey, Tianjin 300170, China;2.Geological Archives of Guizhou Province, Guiyang 550002, Guizhou, China;3.Geological Survey Departmentof Zambia, Lusaka, P. O. Box 50135, Zambia
Abstract:
The Bangweulu Block of northeastern Zambia which consists mainly of basement and sedimentary rocks is affected by northeastern Paleoproterozoic Ubendian Belt, northwestern Mesoproterozoic Kibaran Belt, southeastern Mesoproterozoic Irumide Belt and southwestern Pan African Lufulian Belt. The basement rocks are mainly composed of schist, andesitic-rhyolitic metamorphic volcanic rocks, granitoids and other intrusions. From lower to upper part the sedimentary rocks are mainly composed of the Mporokoso Group, the Kasama Group, the Katanga supergroup and Cenozoic fluvial and lacustrine sediments. The authors systematically studied the geological characteristics of the Kasama Group, U-Pb-Hf isotopic compositions and geochemical characteristics of detrital zircon from the Kasama Group in Kasama area and obtained 32 detrital zircons U-Pb ages of the purplish red siltstone from the Kasama Group. Specifically, their ages mainly vary from (1849±23) to (1993±21) Ma, suggesting that the Kasama Group was formed younger than (1434±14) Ma and should belong to Mesoproterozoic. (176Hf/177Hf)i values of 22 zircons are 0.281049-0.281618 and εHf(t) values are-12.8--1.6 with corresponding TDM2 ages of 2406-3487 Ma. The REE and trace elements of sandstones from Kasama Group were analyzed. The REE have obviously negative δEu anomalies and the points mainly fall in the sedimentary area; the trace elements characteristics of sandstones show that sandstones formed in the passive continental margin.
Key words:  Kasama Group  detrital zircon U-Pb-Hf isotopic compositions  REE and trace elements  Bangweulu Block  northeastern Zambia