扬子地台西南缘大红山群红山组的锆石U-Pb年代学研究——对其原岩形成时代和变质时代的再限定

发布时间：2018-05-24 12:11

本文选题：锆石U-Pb定年 + 形成时代　；参考：《地质论评》2017年04期

【摘要】：大红山群位于扬子地台西南缘,是该区域上变质级别相对较高、形成时代较老的地层单元。本文以侵位于大红山群的侵入岩、红山组顶部的变质火山岩样品为研究对象,运用LA-ICP-MS方法对侵入岩、变质火山岩进行锆石U-Pb定年。石榴黑云钠长片岩、变质辉长岩(DFe1406)和石英钠长石斑岩中锆石为岩浆锆石,3个样品的锆石数据点沿谐和线较集中分布,n(~207Pb)/n(~206Pb)年龄为约1.7 Ga到约1.5 Ga。变质辉长岩(DFe1454)中锆石为变质锆石,n(~207Pb)/n(~206Pb)年龄从约0.8 Ga到约0.7 Ga。结合已有同位素定年资料,可得出如下结论:(1)限定了大红山群中部红山组的成岩年龄为1673～1643 Ma;(2)获得了侵位于红山组变质辉长岩中的变质锆石n(~207Pb)/n(~206Pb)加权平均年龄为748.9±5.7 Ma,表明大红山群经历过约750 Ma前的变质,确定大红山群经历850～750Ma的变质作用,可能与Rodinia超大陆裂解期岩浆事件有关。
[Abstract]:The Dahongshan Group is located at the southwest margin of the Yangtze platform and is a relatively high metamorphic stratigraphic unit in this area. In this paper, the intrusive rocks located in the Dahongshan Group and the metamorphic volcanic rocks at the top of the Hongshan formation are studied. The zircon U-Pb dating of the intrusive rocks and metamorphic volcanic rocks is carried out by using LA-ICP-MS method. The zircons in the metamorphic gabbro (DFe1406) and quartz albite porphyry are magmatic zircons. The zircon data points of the three samples are distributed more closely along the harmonic line. The age ranges from 1.7 Ga to about 1.5 Ga in the metamorphic gabbro (DFe1406) and quartz albite porphyry. The zircon in the metamorphic gabbro (DFe1454) is a metamorphic zircon (207Pb / n ~ (?) 206Pb) ages ranging from about 0.8 Ga to about 0.7 Ga. Combined with available isotopic dating data, The following conclusions can be drawn as follows: (1) the diagenetic age of Hongshan formation in the central part of the Dahongshan Group is limited to 1673 ~ 1643 Ma ~ (2) the weighted mean age of zircon nongzhuo 207Pb / nnyn ~ (206) Pb transgression in the metamorphic gabbro of the Hongshan formation is 748.9 卤5.7Ma. it indicates that the Dahongshan group experienced metamorphism about 750Ma ago. It is concluded that the 850~750Ma metamorphism of the Dahongshan Group may be related to the magmatic events during the Rodinia supercontinent pyrolysis.
【作者单位】：成都理工大学;
【基金】：中国地质调查项目(编号:12120113094900)“川滇黔成矿带基底铜多金属成矿带成矿模式及其找矿模型研究”的成果~~
【分类号】：P597.3

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