重庆铜梁地区“绿豆岩”中碎屑锆石U-Pb年龄及其地质意义

发布时间：2018-06-21 11:56

本文选题：重庆铜梁 + 绿豆岩　；参考：《岩矿测试》2017年06期

【摘要】："绿豆岩"是降落沉积的火山灰经古风化作用和成岩作用形成的多为黏土类的岩石,广泛存在于我国西南早、中三叠世地层间,是良好的区域性等时标志层。研究绿豆岩的成岩年代对进一步了解其成岩机制和时代背景具有重要意义。本文以重庆铜梁地区"绿豆岩"中的碎屑锆石为研究对象,进行了锆石LA-ICPMS定年工作。观察发现本次绿豆岩中挑选的碎屑锆石晶型较完整,具环带结构,U、Th含量普遍较高,为岩浆结晶锆石特征;锆石~(206)Pb/~(238)Pb年龄峰值集中分布在245.86±0.98 Ma和277.6±3.8 Ma。绿豆岩分布在雷口坡组的底部,因此获得的245.86 Ma年龄数据,代表了重庆铜梁地区雷口坡组底部随火山灰进入沉积盆地的锆石的年龄,该年龄值与贵州、广西等地凝灰岩中锆石的年龄相近,故认为在大约246 Ma存在区域性火山喷发事件。较老的锆石应为早期火成岩经风化作用,锆石被带入盆地沉积的结果,其中在277 Ma年处存在一个小的峰值,推断二叠纪中期存在一次岩浆活动。
[Abstract]:"mung bean rock" is a kind of clay rock formed by the volcanic ash of falling deposits through paleo-weathering and diagenesis. It widely exists in the early and middle Triassic strata of southwest China and is a good regional isochronous marker. It is important to study the diagenetic age of mung bean rock for further understanding its diagenetic mechanism and age background. In this paper, the LA-ICPMS dating of zircons from mungbean rocks in Tongliang area, Chongqing, is studied. It is found that the selected clastic zircons from the mung peas are relatively intact, with a high Th content in the zonal structure, which is characterized by magmatic crystalline zircon, and the peak values of zircon Zircon 206Pb / P / 238Pb are mainly distributed at 245.86 卤0.98Ma and 277.6 卤3.8Ma. The mung bean rock distributes at the bottom of the Leikoupo formation, so the 245.86 Ma age data obtained represent the zircon age of the bottom of the Leicoupo formation entering the sedimentary basin with volcanic ash in Tongliang area, Chongqing. The zircon ages of tuff in Guangxi and other places are similar, so it is believed that there are regional volcanic eruptions at about 246 Ma. The older zircon is the result of the weathering of the early igneous rocks and the introduction of zircon into the basin sediments, in which there is a small peak at 277 Ma. It is inferred that there was a magmatic activity in the middle Permian.
【作者单位】：国土资源部成矿作用与资源评价重点实验室中国地质科学院矿产资源研究所;中国地质科学院地质力学研究所;中国地质大学(武汉)地球科学学院;重庆地质矿产勘查开发总公司205队;重庆矿产地质研究院;
【基金】：国家重点研发计划项目“锂能源金属矿产基地深部探测技术示范”课题“我国锂能源金属成矿规律、靶区优选与重点查证”(2017YFC0602701) 中国地质调查局地质调查项目“大宗急缺矿产和战略性新兴产业矿产调查”工程“华南重点矿集区稀有稀散和稀土矿产调查”(DD20160056) 国家自然科学基金资助项目“柴达木盆地大风山特大型天青石矿床锶的富集成矿机制研究”(41402084)
【分类号】：P597.3

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