辽宁西部兴城曹庄地区义县组岩石地层序列及锆石U-Pb年龄  

Stratigraphic sequences and zircon U-Pb dating of Yixian Formation in Caozhuang area of Xingcheng,western Liaoning

作　　者：张乾[1] 张梅生[1] 李晓波[1] 王旖旎[1] 刘雪松[1,2] 张旻旻[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]吉林大学地质博物馆,长春130026

出　　处：《世界地质》2016年第1期51-65,共15页World Geology

基　　金：中国地质调查局工作项目(1212011120730)资助

摘　　要：辽宁西部兴城曹庄地区属于"中生代锦西—锦州—义县—阜新火山喷发带",晚中生代地处阜新—义县盆地的西南端。通过实测剖面和大比例尺调查,确认曹庄地区中生代以火山岩为主的地层可划归义县组,并进一步将其划分为3个岩性段:下段(K_1y^1)由砂砾岩和中性-中基性火山岩组成,中段(K_1y^2)由湖相沉积岩和中性火山岩组成,上段(K1y3)由中性、偏碱性火山岩组成。对尖山剖面火山岩和火山碎屑岩中的锆石采用LA-ICP-MS方法进行的U-Pb测年表明,剖面上义县组下段和中段的年龄分别为131.5±1.4 Ma和129.2±1.0 Ma,次火山状侵位于下段的粗面安山岩加权平均年龄为126.0±1.2 Ma,该结果与北部阜新—义县盆地义县组标准剖面年龄一致。依据火山-沉积序列对比关系,曹庄地区的义县组可以与标准剖面的中、下部对比,但缺失可与标准剖面义县组上部对比的层位,显示该时期火山喷发中心更靠近阜新—义县盆地。The Caozhuang area of Xingcheng in southwestern Mesozoic Fuxin-Yixian basin,western Liaoning,belongs to ＂the Mesozoic Jinxi-Jinzhou-Fuxin-Yixian volcanic eruptive belt＂. The strata mainly volcanic in composition in the Caozhuang area should be grouped into Yixian Formation through the section measuring and large scaled investigation in this area,and can be further divided into three members from in ascending order. The lower member（ K_1y^1） consists of glutenite and intermediate,intermediate-basic volcanic rocks. The middle member（ K_1y^2） consists of lacustrine sediments and intermediate volcanic rocks,and the upper member（ K1y3） consists of intermediate and meta-alkaline volcanic rocks. LA-ICP-MS zircon U-Pb dating of the volcanic and pyroclastic rocks of the Jianshan section reveals that the K_1y^1 and K_1y^2were formed in 131. 5 ± 1. 4 Ma and 129. 2 ± 1. 0 Ma,respectively. The weighted mean age of the intrusive trachyandesite in K_1y^1 is 126. 0 ± 1. 2 Ma,consistent with the age obtained from the type section of Yixian Fomation in Fuxin-Yixian basin. Taking the correlation with the vol-canic-sedimentary sequences,we propose that the Yixian Formation in Caozhuang area can be regarded as the lower and middle Yixian Formation in the type section,with missing its upper part in the Caozhuang area,indicating that the center of volcanic eruption was closer to the Fuxin-Yixian basin at that time.

关 键 词：地层序列 义县组 锆石U-PB测年 早白垩世 辽西 

分 类 号：P534.53[天文地球—古生物学与地层学] P597[天文地球—地质学]