再论红安群地层序列与有关问题

Further Disscussionon on Stratigraphic Sequence of Hong'an Group and Relevant Problems

红安群为出露于秦岭—大别—苏鲁造山带中一套中元古代中浅变质的低角闪岩相—绿片岩相含磷、钇、碳、锰的沉积—火山喷发岩系。其下是以新太古代—古元古代大别山岩群花岗岩化的角闪—麻粒岩相物质为底;其上以低绿片岩相的南华纪耀岭河组变细碧角斑岩系或震旦纪板岩、千枚岩、碳硅质岩、碳酸盐岩等为界。红安群是产出于大别山南麓的区域性高压—超高压变质地体的蓝闪石—榴辉岩高压—超高压变质带内,在区域分布上构成总体上有序,自下而上划分为天台山岩组、七角山岩组、黄麦岭岩组三个构造岩石地层单位,局部无序的构造岩石地层序列,与造山带西部武当岩群为同物异名。鉴于造山带内覆盖于红安群之上的南华纪—震旦纪物质组成并未见磷矿产出的事实,红安群黄麦岭磷矿与扬子区震旦纪含磷地层是不属同一时代的产物。

The Hong'an group occurring in the Qinling-Dabie-Sulu orogens is sedimentary to volcanic series.It formed during the Mesoproterozoic and under metamorphic conditions.The lithofacies equals high greenshist to low amphibolite facies,which is rich in phosphorus,yttrium,carbon,and manganese.The lower stratum accompaning granitization is composed of metamorphic rocks of hornblende granulite subfacies occurring in the lower Neoarchean-Paleoarchaean Dabie group.The upper stratum is composed of spilite-keratophyre series formed in the Yaolinghe Formation in the Nanhua System,and also contains Sinian-aged slate,phyllite,carbonaceous silicalites and carbonate rock.These sequences widely distributed at the southern feet of the Dabie mountains which have underwent regional low-temperature and high-ultrahigh pressure metamorphism with the occurrences of glancophane schist to eclogite facies.This metamorphism event happened during the Indosinian collision between the North China and Yangtze craton.In regional scale,the Hong'an group occurs in well-kept sequence and can be divided into three groups from old to young as:Tintaishan fm,Qijiaoshan fm and Huangmailing fm.In some places,the Hong'an group shows disordered fms.Because phosphorus ore do not occur in the Nanhuaian-Sinian strata,which overlays thus are younger than the Hong'an strata,the phosphorus ore in the Huangmailing fm of the Hong'an group formed in different epochs with Sinian phosphate bearing sequence in Yangtze craton.