赣杭构造带西段上白垩统河口组砂岩碎屑组成及物源区的构造属性

Sandstone detrital composition and tectonic attributes of provenance of the Upper Cretaceous Hekou Formation in western Gan-Hang tectonic belt

对赣杭构造带西段永丰—崇仁盆地上白垩统河口组砂岩碎屑组分进行分析和统计,研究盆地沉积物源及其构造属性。研究结果表明永丰—崇仁盆地上白垩统河口组砂岩碎屑组分特征为：单晶石英颗粒数量占总量的29%~81%,多晶石英颗粒数量占总量的为2%~26%,长石颗粒数量占总量的6%~19%,岩屑颗粒数量占总量的11%~40%。河口组砂岩碎屑主要为次棱角状—次圆状,分选程度中等-差。总体来看,研究区河口组砂岩碎屑组分中岩屑含量相对较高,反映了砂岩成分成熟度偏低。河口组主要为冲积扇和河流沉积体系的产物,沉积物源主要来自盆地两侧青白口系低级变质岩系地层和燕山期酸性火山-侵入杂岩。碎屑组分Dickinson投图表明,研究区上白垩统河口组砂岩主要来自再旋回造山带物源区。

The sandstone detritaI composition of the Upper Cretaceous Hekou Formation in Yongfeng---Chongren basin of western Gan--Hang tectonic belt was analyzed, and the provenance characteristics and its tectonic attributes were studied. The characteristics of sandstone detrital composition of Hekou Formation show that the content of monocrystal quart （Qm） is 29%-81%, the polycrystal quart （Qp） is 2%-26%, the content of feldspar is mainly 6%-19% and the lithic fragments is 11%-40%. The sandstones from Hekou Formation are characterized by subangular to subrounded grains and moderate to poor sorting. As a whole, the content of the lithic fragments is relatively high, which indicates that the compositional maturity of the Hekou Formation sandstones is commonly low. Based on outcrop sedimentary features, Hekou Formation is interpreted as products of fluvial fan river despsitional systems. Both the detrital composition and provenance analysis of the Hekou Formation sandstones indicate that sediments were mostly from the uplifted areas on the both sides of the basin, mainly including low-grade metamorphic rocks of Qingbaikonan System and granitic volcanic intrusive complex of Yanshanian stage. Dickinson ploting results indicate that sandstones of Hekou Formation were mainly derived from the recycled orogen provenance area.