沉积盆地物质来源综合研究——以南堡老第三纪亚断陷盆地为例

The integated study of sediment sources in sedimentary basins:an example from the Eogene Nanpu rift subbasin

关键词:  物源分析  沉积盆地-物源区古环境

Key words:  provenance analysis  palaeoenvironments of sedimentary basins and provenances

摘要:

重矿物分析对于判断沉积盆地的物源方向和物源区的母岩性质是有效的,但具有局限性:①对无重矿物或者仅能提供极少量重矿物的母岩判别力较差;②它不能准确判断物源区沉积物的主要运移通道。因此,进行盆地物源分析还需要重视综合研究,即①通过重矿物的矿物学、重矿物组合研究,判断物源区的母岩类型,推测母岩岩性演化;②通过沉积岩矿物成分与结构研究,判别物源区是否存在重矿物无法辨认的母岩类型和沉积物的搬运距离;③通过沉积体系分析,尤其是砂分散体系的编图,能有效地判断物源区的方位和圈定各物源的具体影响范围;④利用古构造图判别物源区的主要沉积物运移通道及其方位;⑤编制沉积盆地一物源区古环境图,以此来弥补重矿物分析物源所带来的缺陷。

Abstract:

The conventional heavy mineral techniques are effective tools for determining prove-nance orientations and properties of parent rocks,but there exist limitations because:(1) it is difficult to discriminate the source areas of limestones,dolostones and part of clastic sedimentary rocks without or with minor amount of heavy minerals,and(2)Heavy minerals cann't be used to determine accurately the main channels along which the sediments were transported.In this respect,the authors suggested that particular attention should be drawn to:(l)mineralogy and associations of heavy minerals in order to determine the types and lithologic evolution of parent rocks in the source areas;(2)mineral compositions and textures and structures of sedimentary rocks so as to ascertain whether there are unknown parent rock types and transport distance of sediments in the source areas,which cann't be recognized by means of heavy mineral analysis;(3)the analysis of depositional systems, particularly the compilation of sandstone distrbution maps aiming at effectively delimiting the position and extent of the source areas;(4)the application of palaeostructural maps to the identification of the migration channels and directions of the sediments,and(5)the com-pilation of palaeoenvironmental maps of sedimentary basins and provenances.