东焦式磷矿的时代和成因探讨

对东焦式磷矿(和与之相当层位的磷矿)的时代有两种看法。一种认为,分布在太行山的这个含磷岩系是震旦亚界的产物;另一种认为,它属滹沱群范畴。近来,王启超等把这一含磷岩系建为东焦群,归入滹沱超群内部。对于含磷的嵩山群、榆树砬子群、大罗圈河群等的时代,也有不同认识。另外,对这套含磷岩系或磷块岩的成因更有多种不同见解。有的认为是冰碛物,有的认为是海相沉积,有的认为其中磷块岩(如曲阳)是次生富集结果,有的则认为它是热液成因,凡此等等。 根据对太行山等地的野外观测和有关资料的分析,我们认为,分布在各地的这个含磷岩系彼此间可以对比,为滹沱群内部的产物,系沉积成因。

THE AGE AND GENESIS OF PHOSPHOROUS DEPOSITS OF THE DONGJIAO TYPE

Tme pnospnate deposits of tneDongjiao type and its pnospnate-bearing sequences are widely spread in North China.They occur in Taihang Mountains,Wutai Mountains,Zhongtiao Mountains,Luliang Mountains,Songshan Mountains,Jishan Mountains,the east part of Liaoning,the south part of Jilin and so on.We suggest that the age of phosphate-bearing sequences of Dongjiao type was ascribed to the later stage of Hutuo group,but not to the early stage of Sinian period in North China.Generally,there always exist unconformity on the top and base of Dongjiao type of phosphate-bearing sequences and of metamorphic rock series with these sequences in the Dongjiao,Songshan and Guojiazhai groups and other series.The litho-logic characteristics,mineral deposit,metamorphic grade and structural form of phosphate-bearing sequences are different from the underlying and overlying rock formation.They form a tectono-stratigraphic unit alone.The phosphate-bearing sequence can be regarded as a base sedimentary deposit of Molasse strata during the late stage of Hutuo age.The sedimentary texture and structure remained in the phosphate-bearing sequence and phosphorite have proved them to be marine sediments,which were undergoing the metamorphism,solution,weathering and faulting later on.