冀北红旗营杂岩多期变质作用:古元古代俯冲/碰撞—晚古生代伸展—早中生代挤压的记录  

Multi-phase metamorphism in the Hongqiying Complex,northern Hebei:Records of Paleoproterozoic subduction/collision,late Paleozoic extension and early Mesozoic compression events

作　　者：魏春景[1] 赵亚男 初航 WEI Chunjing;ZHAO Yanan;CHU Hang(MOE Key Laboratory of the Orogenic Belt and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China;Tianjin Center,China Geological Survey(North China Center for Geoscience Innovation),Tianjin 300170,China)

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]中国地质调查局天津地质调查中心(华北地质科技创新中心),天津300170

出　　处：《地学前缘》2024年第1期95-110,共16页Earth Science Frontiers

基　　金：国家自然科学基金项目(42030304)。

摘　　要：冀北红旗营杂岩记录了从古元古代到早中生代多期构造-热事件,并可能存在支持古元古代洋壳俯冲的关键证据,但是对其形成时代、变质演化历史和大地构造属性等众说纷纭。本文以总结红旗营杂岩变质作用和年代学研究为基础,探讨其复杂的多期构造演化过程。红旗营杂岩包括表壳岩、赤城混杂岩和正片麻岩三个岩石-构造单元。正片麻岩以古元古代(1.87~1.82 Ga)花岗闪长岩-二长花岗岩-正长花岗岩为主,出现少量新太古代(2.55~2.53 Ga)英云闪长质-花岗闪长质片麻岩。赤城混杂岩为典型蛇绿混杂岩,由退变榴辉岩(斜长角闪岩)和橄榄岩块体以及变质沉积岩组成,形成时代可能>1.88 Ga。表壳岩主要包括不同变质程度的碳质碎屑岩-碳酸盐岩和少量火山岩,可能形成于2.1~2.0 Ga。综合分析赤城混杂岩中的退变榴辉岩、斜长角闪岩和凤山地区含十字石石榴云母片岩的变质作用演化,可划分出5期变质作用。第一期变质作用(M1)存在于凤山地区的云母片岩中,为中压型,顺时针型p-T轨迹,峰期变质条件为1.0~1.1 GPa/>780℃,变质时间为约1.95 Ga。第二期变质作用(M2)见于退变榴辉岩中,顺时针型p-T轨迹,包括升温升压至峰期和峰后等温降压演化阶段,峰期p-T条件为>2.2 GPa/约750℃,地热梯度约为9℃/km。尽管退变榴辉岩中多数锆石限定晚古生代变质年龄,但榴辉岩相变质作用时间应>1.88 Ga。第三期变质作用(M3)出现于凤山地区的云母片岩中,以含十字石组合叠加在M1高级变质组合为特征,顺时针型p-T轨迹,峰期变质条件为0.6~0.7 GPa/610~630℃,变质年龄约为1.88 Ga。第四期变质作用(M4)出现于赤城混杂岩的斜长角闪岩中,由早期榴辉岩组合叠加变质形成,显示“大于号”形p-T轨迹,包括峰前减压升温和峰期后减压冷却变质过程,峰期p-T条件为0.5~0.7 GPa/780~830℃,地热梯度约为35℃/km(低压型),变质时间为晚�The Hongqiying Complex of northern Hebei in the middle northern margin of the North China Craton(NCC)recorded multiple tectono-thermal events from the Paleoproterozoic to early Mesozoic.This complex potentially holds the crucial geological evidence supporting the Paleoproterozoic oceanic subduction,however,its formation age,metamorphic evolution history and tectonic attributes remain debatable.In this paper,the metamorphic processes and geochronology of the Hongqiying Complex are summarised;its complicated,multi-stage tectonic evolution is discussed.The Hongqiying Complex comprises three rock units:orthogneisses(1.871.82 Ga,2.552.53 Ga),(Chicheng)mélange(>1.88 Ga)and supracrustal sequence(2.12.0 Ga).The orthogneisses are dominated by Paleoproterozoic granodiorite-monzogranite-granite,with minor Neoarchean tonalite-granodiorite.The mélange exhibits a typical ophiolitic affinity,consisting of retrograded eclogite(amphibolite)and peridotite blocks within a metasedimentary matrix.The supracrustal sequences comprise dominantly carbon-bearing clastic-carbonate rocks interlayered with minor volcanics with different metamorphic grades.Integrated analyses of retrograded eclogites and amphibolite from the mélange and staurolite-bearing garnet mica schists at Fengshan reveal five phases of metamorphism.The first phase(M1)identified from the mica schists at Fengshan is a medium-p type,characterized by clockwise p-T paths,with peak conditions of p between 1.01.1 GPa,T>780℃and a metamorphic age of>1.95 Ga.The second phase(M2)recognised from the eclogites is a high-p type,showing a clockwise p-T path,with stages of compression-heating to peak and post-peak isothermal decompression;the peak p-T conditions are roughly p>2.2 GPa,T≈750℃and a geothermal gradient of~9℃/km.Despite zircons predominantly yield late Paleozoic metamorphic ages,the eclogite metamorphism is regarded to have occurred at>1.88 Ga.The third phase(M3)is also revealed from the mica schists at Fengshan and is marked by the overprinting of staurolite ass

关 键 词：多期变质作用 古元古代混杂岩 红旗营杂岩 华北克拉通 

分 类 号：P542[天文地球—构造地质学] P588.3[天文地球—地质学]