辽北法库地区层状变质岩系锆石SHRIMP年龄及其地质意义

ZIRCON SHRIMP AGE OF THE STRATIFIED METAMORPHIC ROCKS IN FAKU AREA, NORTHERN LIAONING PROVINCE: Geological Implication

辽北法库地区广泛分布有变质安山岩-英安岩-大理岩夹变质碎屑岩建造所组成的层状变质岩系地层,属古生代造山带的重要组成部分,本文称之为早二叠世佟家屯岩组、照北山岩组和石炭纪磨盘山组.空间上该套地层被二叠纪十间房岩体花岗闪长岩(锆石SHRIMP年龄为284±3 Ma)、五龙山杂岩(锆石SHRIMP年龄为265±4 Ma)和侏罗纪实红土墙岩体(Pb-Pb年龄为221.7±25.71 Ma)所侵.其中佟家屯岩组变质英安岩锆石SHRIMP年龄为267.3±2.7 Ma,代表了火山喷发熔岩形成年龄.根据地质单元之间的时空接触关系以及辽北地区区域地层对比,将该套地层时代归属为早二叠世.

The stratified metamorphic rock series, composed of metamorphic andesite, dacite and marble with metamorphic elastic rock formation is widely distributed in Faku area, Northern Liaoning Province. The rock series, which is a major component of Paleozoic orogenic belt, is referred to as Early Permain Tongjiatun rock formation, Zhaobeishan rock formation and Carboniferous Mopanshan formation. Spatially, the strata are invaded by Permian Shijianfang granodiorite （with zircon SHRIMP age of 284±3 Ma）, Wulongshan complex rock （265±4 Ma） and Jurassic Hongtuqiang granite （Pb-Pb 221.7± 25.71 Ma）. The zircon SHRIMP age of the metamorphic dacite of the Tongjiatun rock formation is 267.3 ± 2.7Ma, which represents the forming age of volcanic lava. Based on the temporal and spatial relation between the geological units and regional stratigraphie correlation to Northern Liaoning, the age of these strata are assigned to Early Permian.