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首页> 外文期刊>Chinese science bulletin >SHRIMP U-Pb zircon age of tuff from the Kunyang Group in central Yunnan: Evidence for Grenvillian orogeny in South China
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SHRIMP U-Pb zircon age of tuff from the Kunyang Group in central Yunnan: Evidence for Grenvillian orogeny in South China

机译：云南中部昆阳群的凝灰岩的SHRIMP U-Pb锆石年龄：华南格伦系造山运动的证据

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Whether or not Grenvillian orogeny occurred in South China still remains highly controversial because high-quality, discriminating data are lacking, and therefore, the key to resolve this matter is to find datable volcanic and/or sedimentary rocks related to Grenvillian orogeny. Such rocks are apparently present in the Fuliangpeng Member from the lower-middle part of Kunyang Group in central Yunnan; here the unit is more than 100 m thick and consists of andesitic ignimbrite, tuffite, terrigeous clastic rocks and carbonates. These volcanic rocks, developed south of the Sibao fold-thrust belts, represent the earliest calc-alkaline volcanic activity in late Precambrian time from central Yunnan and are coeval with both a change in sedimentary facies from detritus to carbonates and the beginning of seismite development elsewhere. Two samples for SHRIMP analysis were collected from this volcanic unit. Sample G3-29-2, from the bottom of Fuliangpeng Member, is an ignimbrite, and about 100 zircon crystals recovered from it have euhedral shapes and display relatively simple sector zonation under cathodoluminescent (CL) imaging, suggesting a magmatogenic origin. Twenty-five of the zircons were analyzed and a weighed-mean U-Pb age of 1032±9 Ma was obtained.Sample G3-29-3 from uppermost part of Fuliangpeng Member is a tuffite, and many rounded, evidently detrital zircons were recovered. Nine of these zircons were analyzed, and the oldest single-grain U-Pb zircon age is 1938±26 Ma, implying that Paleoproterozoic basement developed in Cathaysia. The dating result, combined with the geotectonic research on the Fuliangpeng Member, leads us to conclude that late Mesoproterozoic orogenic volcanic activity occurred in the western part of South China, and that the related collision of Yangtze and Cathaysian cratons was an integral part of the assembly of Rodinia.
机译：由于缺乏高质量，可区分的数据，华南地区是否发生格伦维尔造山运动仍存在争议，因此，解决这一问题的关键是找到与格伦维尔造山运动有关的数据性火山岩和/或沉积岩。这些岩石显然存在于云南中部昆阳群中下部的伏梁棚组。这里的单元厚度超过100 m，由安山辉石，凝灰岩，碎屑碎屑岩和碳酸盐组成。这些火山岩发育在四宝褶皱冲断带以南，是云南中部前寒武纪晚期最早的钙碱性火山活动，与沉积相从碎屑到碳酸盐的变化以及其他地方的地震岩发展的开始同时发生。 。从该火山单元收集了两个用于SHRIMP分析的样品。来自福凉棚成员底部的样品G3-29-2是一个火成岩，从中回收的约100个锆石晶体具有正方体形状，并且在阴极发光（CL）成像下显示出相对简单的扇形区带，表明成岩成因。对25个锆石进行了分析，得出U-Pb的加权平均年龄为1032±9 Ma。福梁鹏段最上部的G3-29-3样品为凝灰岩，并回收了许多圆形，明显碎屑的锆石。 。分析了这些锆石中的9个，最古老的单粒U-Pb锆石年龄为1938±26 Ma，这表明华夏古元古代地下已发育。测年结果与对付梁棚段的大地构造研究相结合，使我们得出结论，华南西部发生了中元古代造山活动，而扬子和华夏克拉通的碰撞是该组合的组成部分。罗迪尼亚。

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