摘要
巴罗式递增变质带能为地壳增厚及造山作用带来全新的认识.为了解辽东半岛北辽河群浪子山组内巴罗式变质带的野外分布和变质特征,对本溪地区连山关-祁家堡巴罗式变质带进行了详细的野外调查和室内研究工作.野外填图表明,浪子山组巴罗式变质带由南向北可以分为黑云母带、石榴石带、十字石带和蓝晶石带.岩相学研究表明,蓝晶石带的蓝晶十字石榴云母片岩保存了3阶段的矿物组合:(1)进变质阶段(M1)矿物组合为Pl+Qz+Ms+Bt+Ctd+Chl±Grt;(2)峰期变质阶段(M2)以Ky+St+Grt+Bt+Ms+Qz+Pl+Ilm为特征;(3)退变质阶段以毛发状的矽线石(M3-1)和变斑晶边缘或裂隙处生长的绿泥石和绢云母为特征(M3-2).相平衡模拟表明,蓝晶十字石榴云母片岩所经历的进变质和峰期变质温压条件分别为~440℃/~3.7 kbar,~670℃/~7.9 kbar,具有典型的顺时针P-T轨迹.变质锆石U-Pb定年结果得到蓝晶十字石榴云母片岩经历了~1.96 Ga的峰期变质作用;碎屑锆石U-Pb年龄分布于2 631~2 020 Ma,浪子山组蓝晶十字石榴云母片岩碎屑物源可能来自于太古宙基底(~2.5 Ga)和2.2~2.1 Ga的岩浆岩.结合前人研究资料表明,浪子山组巴罗式变质带所记录的P-T-t轨迹以及大量的逆冲推覆构造揭示了胶-辽-吉带在~1.96 Ga经历了与造山作用相关的地壳增厚过程.
Barrovian-type progressive metamorphism could lead to a new understanding of crustal thickening and orogenesis. We conduct a detailed field survey and indoor researches about the Barrovian metamorphic zone of the Lianshanguan-Qijiabao of the Benxi area, to understand better of field distribution and metamorphic characteristics of Barrovian metamorphic zone which is located at the Langzishan Formation of the North Liaohe Group in Liaodong Peninsula. The Barrovian metamorphic zone in the Langzishan Formation is divided into biotite zone, garnet zone, staurolite zone, kyanite zone from south to north, according to detailed field mapping. The analysis of petrography suggests kyanite-staurolite-garnet mica-schist of kyanite zone has three stages mineral assemblages:(1) Progressive metamorphic mineral assemblages(M1) are Pl+Qz+Ms+Bt+Ctd+Chl±Grt;(2)metamorphic peak(M2) is characterized by Ky+St+Grt+Bt+Ms+Qz+Pl+Ilm;(3) retrograde metamorphic stage mainly has trichoid sillimanite(M3-1) and chlorite and sericite around rims and cracks of porphyroblasts(M3-2). Phase equilibrium modeling shows metamorphic P-T of progressive metamorphic stage and peak stage of kyanite-staurolite-garnet mica-schist are respectively^440 ℃/~3.7 kbar, ~670 ℃/~7.9 kbar, and the rock has a typical clockwise P-T path. The results of U-Pb geochronology of metamorphic zircons indicate kyanite-staurolite-garnet mica-schist has experienced peak metamorphism at ~1.96 Ga;these ages of U-Pb detrital zircons are scattered among 2 631-2 020 Ma, indicating the clastic sediments may be from an ancient Archean basement of ~2.5 Ga and magmatic rocks of 2.2-2.1 Ga. Combined with previous research data, the clockwise P-T-t path and thrusting nappe structure recorded by the Barrovian metamorphic zone of the Langzishan Formation represent Jiao-Liao-Ji belt has experienced crustal thickening produced by orogenesis around 1.96 Ga.
作者
文飞
田忠华
刘平华
向华
Wen Fei;Tian Zhonghua;Liu Pinghua;Xiang Hua(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第9期3403-3419,共17页
Earth Science
基金
中国地质调查局地调项目(No.DD20190003)
国家自然科学基金项目(Nos.41672191,41972205)。
关键词
巴罗式变质带
辽河群浪子山组
P-T-T轨迹
地壳增厚
岩石学
Barrovian metamorphic zone
Langzishan Formation of Liaohe Group
P-T-t path
crustal thickening
petrology
