Discovery of rhyolitic tuffaceous slate in the southwestern margin of Yangtze Craton:Zircon U-Pb ages(2491 Ma)and tectonic-thermal events  

作　　者：Jun-ping Liu Su-mei Tian Xun-zao Zhu Jin-hua Ma Jing Li Shao-bin Hu Sai-ying Yu Hu Zhang Zhong-ming She Xu-gui Li 

机构地区：[1]Yunnan Institute of Geological Survey,Kunming 650216,China [2]China University of Geosciences,Beijing 100083,China [3]Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Ministry of Natural Resources,Kunming 650051,China [4]Yunnan Department of Natural Resources,Kunming 65000,China

出　　处：《China Geology》2021年第4期616-629,共14页中国地质（英文）

基　　金：The work was financially supported by Project of 1∶50000 Regional Geological Survey of Samaki,Yinmin,Guicheng and Shugu Sheets in Yunnan Province by Land and Resources Department of Yunnan Province(D201905);Project of 1∶50000 Regional Geological Survey of Erjie,Yimen,Mingyihe and Shangpubei Sheets in Yunnan Province(DD20160017);Regional Geological Survey Area Summary and Service Product Development in Yunnan Province by China Geological Survey(121201102000150012-02).

摘　　要：The Mesoproterozoic Dongchuan Group that is widely exposed in Yimen area,central Yunnan Province is a series of sedimentary sort of low-grade metamorphic rocks interbedded with volcanic rocks,which are closely related to the early tectonic evolution of the Earth.However,its formation era,sedimentary filling sequence,and geotectonic characteristics have always been in dispute.In this study,several rhyolitic tuffaceous slate interlayers with a centimeter-level thickness were found in the previously determined Heishan Formation of the Dongchuan Group located to the western part of Yimen-Luoci fault zone.This paper focuses on the study of the rhyolitic tuffaceous slate in Qifulangqing Village,Tongchang Township,Yimen County.LA-ICP-MS zircon dating was conducted,achieving the crystallization age of magma of 2491±15 Ma and the metamorphic ages of about 2.3 Ga,2.0 Ga,and 1.8 Ga for the first time.Meanwhile,according to in-situ Hf isotope analysis,the zirconεHf(t)values were determined to range from−3.0 to 7.6,with an average of 2.7.Furthermore,the first-stage Hf model age(TDM1)was determined to be 2513−2916 Ma,indicating that the provenance of the rhyolitic tuffaceous slate is the depleted mantle or juvenile crust between the Middle Mesoarchean and the Late Neoarchean.Therefore,it is believed that the strata of the slate were deposited in the Late Neoarchean,instead of the Mesoproterozoic as determined by previous researchers.Accordingly,it is not appropriate to group the strata into the Mesoproterozoic Dongchuan Group.Instead,they should be classified as the Maolu Formation of the Neoarchean Puduhe Group given the lithologic association and regional information.Furthermore,the magma ages of 2491±15 Ma are highly consistent with the eras of the large-scale Late Neoarchean orogenic magmatic activities on the northern margin of the Yangtze Craton,and thus reflect the orogenic process consisting of subduction and collision from Late Neoarchean to Early Paleoproterozoic.The magmatic activities during this period were

关 键 词：Maolu Formation Puduhe Group Late Neoarchean Zircon U-Pb age Tectonic-thermal event Geological survey engineering Eastern margin of Qinghai-Tibet Plateau Yangtze Craton 

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