青藏高原羌塘南部冰海杂砾岩的成因与物源——以冈玛错地区为例

青藏高原及其邻区石炭纪—二叠纪地层中广泛分布的漂砾层、杂砾岩、含砾板岩等是一套特殊的冰海相沉积岩,称为冰海杂砾岩,前人已对它的成因环境做了初步的研究,但没有获得统一的结论。本次以青藏高原羌塘南部冈玛错地区冰海杂砾岩的砾石为研究对象,观察它们的野外特征和镜下特点,并对与冰海杂砾岩互层产出的石英砂岩做了粒度分析。结果表明,冰海杂砾岩是在冈瓦纳大陆冰川呈消融状的情况下,冰阀搬运沉积的产物。通过碎屑锆石和岩性对比,初步认为冰海杂砾岩的物源为冈瓦纳大陆,并简单论述了冰海杂砾岩各类砾石的可能来源。以上研究成果为探讨冈瓦纳大陆的沉积环境提供了依据。

The genesis and material source of Carboniferous-Late Permian ice miscellaneous conglomerate： a case study of Gangma Co area,Qiangtang,Tibetan Plateau

In Tibetan Plateau and its adjacent areas,boulder beds,complex conglomerates and pebbly slate are widely distributed in Carboniferous-Permian strata,constituting a special type of ice marine deposit,called ice miscellaneous conglomerate.Although previous researchers have done some work on the formation environment of ice miscellaneous conglomerate,no unanimous conclusions have been reached.With the conglomerate of ice miscellaneous conglomerate in Gangmacuo area of southern Qiangtang within Tibetan Plateau as the study object,the authors observed the field and microscopic characteristics of gravels and,through the grain size analysis of quartz sandstone which is interbeded with ice miscellaneous conglomerate,revealed that the ice miscellaneous conglomerate was the deposit of ice rafting when Gondwana continental glaciar was in a state of ablation.Through a comparative study of detrital zircons and lithologic characters,the authors have reached the conclusion that the provenance of ice miscellaneous conglomerate was from Gondwana continent.On such a basis,this paper discusses the possible sources of the gravels for ice miscellaneous conglomerate.These achievements provide evidence for the sedimentary environment of Gandwana continent.