惠州凹陷珠江组泥岩地球化学特征及其地质意义

Geochemical characteristics and geological significance of mudstones from Zhujiang formation of Huizhou depression

为深入探讨珠江口盆地惠州凹陷珠江组沉积时期物源属性、源区构造背景及沉积环境特征,以8口井18个泥岩样品的主量元素、微量元素和稀土元素测试数据为基础,对珠江组沉积物中泥岩的地球化学元素特征进行综合分析。结果表明:珠江组源岩以上地壳以长英质岩石为主,其中东部区域为长英质和基性岩的混合物源,西部区域为长英质物源,南部区域为长英质物源和被动大陆边缘物源;东部区域的物源具有活动大陆边缘的构造背景,西部和南部区域的物源具有被动大陆边缘的构造背景;南部区域处于还原条件,水体较深,西部区域水体次深,而东部区域处于氧化条件,水体相对较浅;东部区域盐度较高,而西部和南部区域盐度较低;珠江组沉积时期研究区处于湿热的气候条件,其中西部和南部区域湿热程度较高,东部区域湿热程度较低。

In order to further discuss provenance attribute, tectonic setting and sedimentary environment of Zhujiang formationin the Huizhou depression of Pearl River Mouth Basin, geochemical elements of mudstones in Zhujiang formation were com-prehensively analyzed based on experimental data of the major elements, trace elements and rare earth elements of the 18samples from 8 wells. The results show that the parent rocks of Zhujiang formation are mainly supracrustal felsic rocks. Theprincipal sources of detritus in the eastern region are derived from the mixed source of felsic and basic rocks, the principalsources of detritus in the western region are derived from the felsic source, and the principal sources of detritus in the south-ern region are derived from the felsic source and passive margin source. The tectonic setting of the eastern provenance is sim-ilar to that of active continental margin, and the tectonic settings of the western and southern provenance are similar to that ofpassive continental margin. The sedimentary water during Zhujiang formation period in the southern region was relatively deepand in reduction condition. The sedimentary water in the western region was medium. The sedimentary water in the easternregion was relatively shallow and in oxidation condition. The salinity of the eastern region was higher while the salinity of thewestern and southern region was lower in Zhujiang formation. There was a warm-wet climate condition in the Zhujiang forma-tion, but the warm-wet degree was relatively higher in the western and southern region, and at the same time it was relativelylower in the eastern region.