四川盆地北部须家河组四段物源体系分析

Provenance analysis of 4th Member of Xujiahe Formation in northern Sichuan Basin

为明确四川盆地北部须家河组四段的物源体系特征,进一步预测储集砂体的展布,运用野外露头调查和岩心岩屑样品测试等手段综合分析了须四段古水流方向、砾石成分、砂岩碎屑组分、重矿物组合特征等。结果表明,研究区主要受控于3大物源体系,不同的物源体系影响范围、矿物组成各不相同。北西向物源来自龙门山北段,为盆内提供大量碳酸盐岩岩屑和碳酸盐岩质砾石,主要影响元坝西部;北北东向米仓山物源体系以含丰富的低级变质岩、火山岩砾石及岩屑为特征,延伸范围有限;北东向大巴山物源体系是研究区的供源主体,物源充足,延伸范围广阔。

For further exploration of the provenance direction and sand body distribution, paleocurrents, gravel components, detrital composition and heavy mineral characteristics of the fourth Xujiahe Formation have been synthetically analyzed using outcrops observation and core sample tests. The results show that the work area is mainly controlled by three provenance directions. Different provenances have different impact area and characteristics： the NW provenances are mainly from the northern section of Longmen Mountains, providing a large number of carbonate debris and carbonate gravel, which mainly affects the western Yuanba Area; the NNE Micang provenance systems with limited extension are characterized by abundant low-grade metamorphic rock, volcanic gravel and debris; the NE Daba provenance systems are the main source for the work area, which have adequate sources and large influence area.