投稿时间：2021-03-22
修订日期：2022-04-29
网络发布日期：2022-07-07
中文摘要:中国西南地区中三叠世雷口坡组或关岭组下部及底部普遍发育多层凝灰岩。已有研究显示，早三叠世—中三叠世出现了生态环境间歇性恶化和生物迟滞复苏，划分中国中三叠统安尼阶-拉丁阶界线的标志化石还未寻找到，这些问题是否与火山活动有关，值得进一步研究。文章对四川沐川地区河口剖面中三叠统雷口坡组下部的凝灰岩进行了锆石LA-ICP-MS U-Pb定年和岩石地球化学研究，获得中三叠统安尼阶-拉丁阶界线年龄为（242.5±1.2） Ma（MSWD=0.93，n=22），此年龄结果与国际地层年代表（2020版）建议的安尼阶-拉丁阶界线年龄（242 Ma）较为吻合，证实沐川地区雷口坡组沉积时代为中三叠世安尼期和拉丁期。凝灰岩岩石地球化学特征显示出明显富K2O、MgO，明显负铕异常的特征，其物源可能来自古特提斯洋俯冲作用形成的大陆岩浆弧。多期次的火山活动可能是导致早三叠世—中三叠世生态环境间歇性恶化和生物迟滞复苏的重要原因，安尼期-拉丁期交替时期发生的火山活动可能影响了生物的演化，故难以寻找到划分中国中三叠统安尼阶-拉丁阶界线的标志化石，加强对中三叠世火山活动的研究，对中国三叠系划分方案、中三叠世地层划分对比及探索三叠纪生物演化与复苏具有重要意义。
Abstract:There are multi-storey tuffs in the lower part and bottom of the Middle Triassic Leikoupo Formation or Guanling Formation in southwest China. Previous studies have shown that there was an intermittent deterioration of the ecological environment and the recovery of biological hysteresis in the Early-Middle Triassic. The marked fossils of the Middle Triassic Anisian-Latinian boundary in China have not been found. Whether these problems are related to volcanic activity deserves further study.Zircon LA-ICP-MS U-Pb dating and lithogeochemistry of tuff in the lower part of Middle Triassic Leikoupo Formation in Hekou section, Muchuan area, Sichuan Province were studied.The age of the Middle Triassic Anisian-Latinian boundary is (242.5±1.2)Ma (2δ, MSWD=0.93, n=22), which is basically consistent with the 242 Ma age of the Anisian-Latinian boundary recommended by the international stratigraphical timetable(2020 edition). It is confirmed that the sedimentary age of the Leikoupo Formation in Muchuan area is Middle Triassic Anisian period and Latinian period.The lithogeochemistry characteristics of tuff show obvious enrichment of K2O, MgO and obvious negative Eu anomalies,its provenance may come from continental magmatic arc formed by subduction of the Paleotethys Ocean.Multistage volcanic activities may be an important cause of intermittent deterioration of ecological environment and delayed recovery of organisms in the Early-Middle Triassic. Volcanic activities during the Anisian-Latinian alternating period may affect biological evolution,so it's hard to find the marked fossils of the Middle Triassic Anisian-Latinian boundary in China. Strengthening the study of volcanic activities in the Middle Triassic is of great significance to the division scheme of Triassic in China,the stratigraphic division and correlation of Middle Triassic,and the exploration of Triassic biological evolution and recovery.
文章编号：
中图分类号：
文献标志码：
基金项目:本文得到四川省自然资源厅省政府性投资地质勘查项目（编号：DZ202002）和四川省自然资源厅科技项目（编号：kj-2022-6）联合资助
引用文本：
文俊,任光明,庞维华,赵俊兴.2022.四川沐川地区中三叠统凝灰岩锆石U-Pb年代学、地球化学特征及地质意义[J].矿床地质,41(3):585~597WEN Jun,REN GuangMing,PANG WeiHua,ZHAO JunXing.2022.Zircon U-Pb geochronology, geochemical characteristics and geological significance of tuff from Middle Triassic in Muchuan area, Sichuan Province[J].Mineral Deposits41(3):585~597
图/表
