华北板块南缘栾川群研究  

Study on Luanchuan Group in the South Margin of North China Plate

作　　者：石铨曾 陶自强 庞继群 曲明绪 

机构地区：[1]河南省地质科学研究所

出　　处：《华北地质矿产杂志》1996年第1期51-59,共9页

基　　金：河南省地矿厅"八五"研究课题

摘　　要：栾川群出露于东秦岭北部。在栾川群分布区域，古华北板块不同时代的地层往南逆冲，构成北秦岭的太华推覆体。栾川群存在于该推覆体内部的特定逆冲岩席之中，沿这一逆冲岩席追索，确定古华北板块南缘的栾川群是连续沉积的，而受后期推覆构造的改造，栾川群在推覆体前缘的分布是断续相连的。根据地层之间的接触关系、岩浆活动、沉积作用的研究，对栾川群的划分提出了新的看法，认为栾川群由三川组、南泥湖组、煤窑沟组及大红口组构成。栾川群形成于震旦纪晚期，由湖坪及潮下斜坡等滨浅海沉积物构成。栾川群的岩浆岩为具双众数特征的岩套，具典型的大陆裂谷岩浆岩特征。并认为中元古代以来，古华北板块南缘处于裂陷拉张环境。早期的裂陷形成了熊耳群、汝阳群、官道口群及竞坪群，晚期裂陷的过程形成了栾川群、陶湾群，其进一步发育导致以二郎坪群为代表的洋壳生成。Luanchuan Group exposes at the north part of East Qinliny Orogenic Belt. In the processof Mesozoic orogenesis, the strata of ancient North-China Plate thrusted southwards at different ages and so that Taihua Nappe formed at the north part of the East Qinling Mountains. Luanchuan Group is existed in the specific thrust sheets of the nappe. Tracing thesethrust sheets, the Luanchuan Group is continuously developed along at the south margin ofancient North-China Plate,and extends uncontinuously over 400 km along the tectonic belt.On the basis of the stratum contact relatiohship and the research on magmatism as wellas sedimentary factes, the authors put forward a new method to divid Luanchuan Group. Originally the researchers classified the strata of different ages into Luanchuan Group as a result of failure to ascertain the stratum contact relationship. According to the authors, Luanchuan Group is composed of Sanchuan Formation, Nannihu Formation, Meiyaogou Formation and Dahongkou Formation, and formed at the Last Proterozoic (the Rb-Sr isochron dating of Dahongkou Formation volcanic complexes is 660±27 Ma and its Sin-Nd age is 682±60Ma). Luanchuan Group was mainly deposited in littoral and neritic areas such as tidal flatand supratidal slope with a sediment thickness of around 3000 m. The overlying stratum ofLuanchuan Group is Taowan Group of Early Palaeozoic which was composed of continentalslope and bathyal sediments. After a systematic study on petrography, petrochemistry, rareearth element partitioning and rare element geochemistry of the magmatite of LuanchuanGroup and Taowan Group, the authors regard the magmatite of Luanchuan Group as alkalivolcanic complex with bimodal characteristics. It has the typical feature of continental riftmagmatite, whereas,the metamorphic basic igneous rocks of Taowan Group belong to oceanictholeiite series, completely different from the magmatites of Luanchuan Group.Between Luanchhan Group and the underlying Middle. Proterozoic, there exists a regional unconformity. It indicates

关 键 词：栾川群 推覆构造 华北板块 地层 震旦纪 

分 类 号：P534.31[天文地球—古生物学与地层学]