南岭科学钻探青白口系中发现381 Ma流纹岩

南岭科学钻探(NLSD-1)选址于江西省于都—兴国—宁都三县交界地区实施,构造上属华夏板块内部的武夷和罗霄两块体交汇部位。南岭科学钻探瞄准构造结合部区域地质问题和矿集区深部成矿预测两方面科学目标进行探索。NLSD-1开孔至1373.71 m揭露了连续的青白口纪地层,是一套完整的凝灰质火山碎屑岩韵律层,主要岩性有凝灰质粉砂岩、凝灰质细砂岩、变沉凝灰岩、凝灰质板岩和流纹岩。本次工作在科学钻探精细地质编录的基础上,对各类岩性地层进行镜下鉴定,并挑选流纹岩中的单颗粒锆石,应用LA-ICP-MS锆石U-Pb法进行定年,获得了一组高度谐和的同位素年龄,确定流纹岩成岩时代为381 Ma,为赣中南地区新元古代地层时代的进一步划分、归属和地质演化研究提供了新的信息。

381 Ma rhyolite found by Nanling scientific drilling in Qingbaikouan System

Nanling scientific drilling(NLSD-1)is located at the junction of Yudu-Ningdu-Xingguo county in Jiangxi Province. Tectonically,the hole site of NLSD-1 is located at the intersection of Wuyi and Luoxiao block inside the Cathaysian plate. NLSD-1 aims at solving the scientific problems of regional geology and metallogenic regularity in the ore concentration area. The NLSD-1 hole intersects Qingbaikouan strata at 1373.71 m which are composed of a rhythm layer of tuffaceous volcanic clastic rock consisting of tuffaceous siltstone, tuffaceous sandstone, variable tuff, tuffaceous slate and rhyolite. Based on detailed geological logging and identification of different kinds of lithostratigraphy under microscope, the authors selected zircons from the rhyolite of NLSD-1. A set of high harmonic isotopic ages were obtained by using LA-ICP-MS, which can be used to make sure that the formation age of rhyolite is 381 Ma. This datum provides new information for the further division, assignment and study of geological evolution of stratigraphic age of Late Proterozoic in the middle south area of Jiangxi Province.