重矿物资料在沉积物物源分析中的应用——以涠西南凹陷古近系流三段下亚段为例

Application of Heavy Mineral Data in the Analysis of Sediment Source:A case study in the Paleogene lower submember of the third member of the Liushagang Formation,Weixinan Depression

重矿物资料在沉积物物源分析中被广泛的应用。采用聚类分析的数学统计方法,将重矿物资料在垂向上分出不同的沉积期次,得出表征不同母岩区的重矿物组合类型,进而在整个研究区对比划分物源体系并结合ZTR等值线图研究各沉积期次物源方向。由此涠西南凹陷古近系流三段下亚段可划分为四大物源体系,分别为北西物源体系,南西物源体系,北东物源体系,东部物源体系。各物源体系及物源方向与扇三角洲或冲积扇的主推进方向一致。因此,利用聚类分析方法所得的重矿物组合类型划分涠西南凹陷物源区是十分有效的。

Heavy mineral data are widely used in the analysis of sediment source.Source rocks of different depositional stages and different source areas can be identified based on heavy mineral suites.In this study using Q-type clustering analysis,the sample group with the same or similar features in the vertical profile is identified as sediments of the same depositional stages,so each sample group is representative of a certain depositional stage or source rock.On the basis of Q-type clustering analysis,using R-type clustering analysis,the differences among each kind of heavy mineral are available in the same depositional stage,and different heavy mineral suites are defined.The same heavy mineral suite is considered that it comes from the same source rock,and the different heavy mineral suites are used to recognize different source areas.These,the sediments with features of the same depositional stage and the same heavy mineral suite are as an independent system.Coupled with the independent system’s ZTR maps,allow robust identification of specific directions of sediment source in each depositional stage.The integrated data set shows that there are four distinct sediment sources in the submember in the study area.These are the northwest source,the southwest source,the northeast source,and the east source.The directions of different sediment sources identified are in accordance with the main building directions of fans delta or alluvial fans.Using heavy mineral suites generated from cluster analysis to identify source area in the Weixinan Depression is quite effective.