河南鲁山新元古界罗圈组石英颗粒形态特征及意义

Morphological characteristics of quartz grains in the Luoquan formation of the Neoproterozoic in Lushan, Henan province

豫西地区罗圈组成因的确定对新元古代冰期事件的研究具有重要意义。本文用扫描电镜观察鲁山龙潭沟地区罗圈组沉积物中的石英颗粒表面27种常见表面结构特征,统计分析这些特征出现的频率,恢复其沉积环境。结果表明:与沉积环境分析关系密切的擦痕特征频率为28%~44%;平整的破裂面特征频率为36%~84%;大贝壳状断口的特征频率为24%~52%,小贝壳状断口特征频率为20%~44%;V形撞击坑特征频率为4%~12%。颗粒特征及特征频率说明这是一套冰川成因的沉积物,后期接受了轻微流水改造,最后遭受成岩及风化作用。表明鲁山龙潭沟地区罗圈组沉积时期存在冰川活动,推断其冰川活动与全球冰川事件相关。该研究为确定豫西地区新元古代有冰川发育提供一定的参考价值。

The determination of the origin of the Luoquan formation is of great significance to the study of the Neoproterozoic Glacial events in Lushan Area,Western Henan Province.In this paper,surface morphological characteristics of quatz grains in the sediments of the Luoquan Formation in Longtangou area of Lushan were studied by scanning electron microscopy(SEM).There are twenty-sevencommon surface morphological characteristics.The occurrence frequency of these features were statistically analyzed to restore their sedimentary environment.The characteristics that closely related to the sedimentary environment analysis are striation,flat cleavage surface,large conchoidal fracture,small conchoidal fracture and V-shaped percussion crack.The frequency of them are in the range of 28%-44%,36%-84%,24%-52%,20%-44%and 4%-12%,respectively.The characteristics and frequencies indicate that these are a set of glacial deposits,which were later subjected to minor running water transformation and finally suffered diagenes is and weathering.It indicates that there are glacier activities during the sedimentary period of the Luoquan formation in Longtangou are a of Lushan.Besides,its glacial activity is related to global glacier events.This study provides a certain reference value for determining the development range of the Neoproterozoic glacier in the region.