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滇西保山地块下古生界碎屑锆石U-Pb年代学特征及其对原特提斯洋构造演化约束

Lower Paleozoic detrital zircon U-Pb geochronological characteristics of the Baoshan Block in western Yunnan and its constraints on the Proto-Tethys tectonic evolution
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摘要 滇西保山地块是东特提斯构造域的主要微陆块之一,但对其物源和古地理位置仍存在较大争议。本文通过对保山地块西缘早古生代地层进行碎屑锆石U-Pb定年来约束其物源及古地理位置,并进一步探讨原特提斯洋早古生代构造演化模式。保山地块西缘早古生代地层具有相似的年龄分布模式,主年龄峰期为-0.95Ga、次级年龄峰期为-1.2Ga和-2.5Ga。寒武系公养河群最小锆石年龄为526Ma,结合其上部年龄为499.2Ma的火山岩夹层,约束其沉积时代为早寒武世早期。对比保山地块不同区域早古生代地层的碎屑锆石年龄数据,它们都具有相似的锆石年龄分布模式和年龄峰值。-0.95Ga主年龄峰期和-2.5Ga的次级年龄峰期指示保山地块早古生代的沉积物主要来自于印度大陆,而-1.2Ga的次级年龄峰期表明有部分沉积物来自于西澳大利亚,其早古生代古地理位置位于印度和西澳大利亚之间。结合沉积学证据及滇西地区广泛发育的早古生代岩浆作用,本文认为早古生代冈瓦纳大陆北缘为活动大陆边缘。 The Baoshan Block in western Yunnan is one of the main micro-continents in the eastern Tethys tectonic domain, but its provenance and paleo-geographical location are still controversial. This paper constrains its provenance and paleo-geographical location by detrital zircon U-Pb dating of the Lower Paleozoic strata in the western margin of the Baoshan Block, and further explores the Early Paleozoic tectonic evolution model of the Proto-Tethys Ocean. The Lower Paleozoic strata in the western margin of the Baoshan Block have a similar age distribution pattern, with the main age peak at -0.95 Ga, and the secondary age peaks at -1.2 Ga and -2.5 Ga. The minimum zircon age of the Cambrian Gongyanghe Group is 526 Ma, combined with the upper volcanic rock interlayer with an age of 499.2 Ma, which constrains its depositional age to be the Early Cambrian. Comparing the detrital zircon age data of Lower Paleozoic strata in different areas of the Baoshan Block, they all have similar zircon age distribution patterns and age peaks. The main age peaks of -0.95 Ga and the secondary age peaks of -2.5 Ga indicate that the Early Paleozoic sediments of the Baoshan Block were mainly from the Indian continent, while the secondary age peaks of -1.2 Ga indicate that some sediments came from the western Australia. Its Early Paleozoic paleo-geographical location is between India and western Australia. Combined with the sedimentary evidence and the widespread Early Paleozoic magmatism in western Yunnan, we believe that the northern margin of the Gondwana continent was an active continental margin in the Early Paleozoic.
作者 高煜 李刚 刘正宏 刘俊来 王晨 徐仲元 王长兵 GAO Yu;LI Gang;LIU ZhengHong;LIU JunLai;WANG Chen;XU ZhongYuan;WANG ChangBing(College of Earth Sciences,Jilin University,Changchun 130061,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China;No.209 Geological Party,Geological Bureau of Yunnan Nuclear Industry,Kunming 650106,China)
出处 《岩石学报》 SCIE EI CAS CSCD 北大核心 2023年第3期921-937,共17页 Acta Petrologica Sinica
基金 国家自然科学基金项目(91955205)资助。
关键词 原特提斯洋 活动大陆边缘 保山地块 碎屑锆石U-PB年龄 Pro-Tethys Active continental margin Baoshan Block Detrital zircon U-Pb ages
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