冀北中低级变质表壳岩的年代学特征及其对华北克拉通构造演化的约束  

Geochronology of the medium- and low-grade metamorphosed supracrustal rocks from northern Hebei: Constraint on the Late Neoarchean tectonic evolution of the North China Craton

作　　者：葛松胜[1,2] 翟明国[1] 李铁胜[1] 彭澎[1] 王浩铮[1,2] 崔夏红[1,2] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国科学院大学,北京100049

出　　处：《岩石学报》2016年第2期571-589,共19页Acta Petrologica Sinica

基　　金：国家"973"计划项目(2012CB4166006);国家自然科学基金项目(41210003)联合资助

摘　　要：华北克拉通在新太古代末期发生克拉通化,形成了现今规模的古陆,大量的太古宙岩石均经历了~2500Ma左右的区域高级变质作用（高角闪岩相-麻粒岩相）。而华北克拉通北部冀北地区出露一套中低级变质（绿片岩相-角闪岩相）的火山-沉积岩系,主要包括胡麻营地区红旗营子表壳岩和大阴山地区单塔子表壳岩中变质程度较低的部分。胡麻营地区红旗营子表壳岩系主要岩石组合为变基性火山岩、绿帘角闪岩、斜长角闪岩、含石榴石斜长角闪岩、角闪斜长片麻岩、黑云斜长片麻岩、黑云角闪斜长片麻岩、黑云二长片麻岩、石英片岩、磁铁石英岩等,SIMS锆石U-Pb定年结果表明斜长角闪岩形成于2486±18Ma（MSWD=1.4）,而黑云斜长片麻岩形成于2507±37Ma（MSWD=2.0）。大阴山地区单塔子中低级变质表壳岩系主要由浅变质火山岩、云母石英片岩、斜长角闪岩、磁铁石英岩和大理岩等组成,SHRIMP锆石U-Pb定年结果显示,浅变质火山岩中的变玄武岩形成于2490±19Ma（MSWD=2.0）,而变英安岩形成于2502±8Ma（MSWD=0.83）。因此,冀北中低级变质的表壳岩系主要形成于新太古代末期,形成年龄为2507~2486Ma;结合冀东青龙地区新太古代末期（2511~2503Ma）的浅变质火山-沉积岩系（青龙表壳岩）,我们认为新太古代末期,中低级变质表壳岩系广泛分布于华北克拉通的核部和边缘地区,此套岩系覆盖在太古宙高级变质杂岩之上,代表华北克拉通化之后的稳定盖层,是克拉通化的主要标志之一。The Late Neoarchean witnessed the cratonization of the North China Craton（ NCC） through amalgamation of several micro-blocks to form a coherent basement. The Archean rocks in this craton have experienced varied grades of regional metamorphism ranging up to upper amphibolite and granulite facies at ~ 2500 Ma. However,medium- and low-grade metamorphosed（ greenschist to lower amphibolite facies） volcanic-sedimentary rocks are widely distributed in northern Hebei Province. It includes Hongqiyingzi supracrustal rocks in the Humaying district and the low-grade metamorphosed part of the Dantazi supracrustal rocks in the Dayinshan district. The Hongqiyingzi supracrustal rocks in the Humaying district consist mainly of meta-mafic volcanic rocks, epidote amphibolite,amphibolite,garnet amphibolite,hornblende-plagioclase gneiss,biotite-plagioclase gneiss,biotite monzonitic gneiss,quartz schist and magnetite quartzite. SIMS zircon U-Pb ages of 2486 ± 18Ma（ MSWD = 1. 4） and 2507 ± 37Ma（ MSWD = 2. 0） are interpreted as the formation age of the amphibolite and biotite-plagioclase gneiss,repectively. The Dantazi supracrustal rocks in the Dayinshan district consist mainly of low-grade metamorphosed volcanic rocks,biotite-quartz schist,amphibolite,magnetite quartzite and marble. SHRIMP zircon U-Pb ages of 2490 ± 19Ma（ MSWD = 2. 0） and 2502 ± 8Ma（ MSWD = 0. 83） are interpreted as the formation age of the meta-baslt and meta-dacite,respectively. Therefore,the medium- and low-grade metamorphosed volcanicsedimentary rocks in the northern Hebei region were formed in the Late Neoarchean. Our new data,combined with the 2511 ~ 2503 Ma Qinglong low-grade volcanic-sedimentary rocks in the eastern part of the NCC suggest that the medium- and low-grade metamorphosed volcanic-sedimentary rocks distributed not only in the central area but also in the margin of the NCC. The protoliths of these mediumand low-grade metamorphosed supracrustal rocks were deposited on Archean high-grade metamorphosed complex within the crat

关 键 词：红旗营子杂岩 单塔子杂岩 表壳岩 锆石年龄 华北克拉通 

分 类 号：P588.34[天文地球—岩石学] P597.3[天文地球—地质学]