琼东南盆地深水区中央峡谷黄流组物源特征

物源分析作为岩相-古地理研究的前提和基础,物源体系决定了砂体的展布和储集性能。为明确中央峡谷体系黄流组储集体展布规律及下一步勘探方向,本文应用中央峡谷最新钻井资料,采用重矿物组合、锆石U-Pb测年等分析方法,结合地震反射特征,对中央峡谷黄流组物源体系特征进行分析。地震反射特征表明来自海南隆起和昆嵩隆起物源的三角洲体系,通过二次搬运沉积了陆架斜坡区和盆底的低位海底扇,为中央峡谷的沉积充填提供了充足的粗碎屑沉积物;新钻井黄流组样品中重矿物组合以白钛矿、石榴石、磁铁矿含量较高为主要特征,与莺歌海盆地受蓝江物源影响和琼东南盆地受丽水-秋滨河物源影响的地层重矿物组合相似;锆石U-Pb测年分析表明,中央峡谷黄流组地层中样品年龄图谱具有30~2 000Ma变化范围,与莺歌海盆地受昆嵩隆起物源影响的钻井以及越南现代河流采集的沙样具有非常一致的年龄段和丰度。综上所述,中央峡谷受多物源的影响,越南昆嵩隆起为主的琼东南盆地西部物源体系,是琼东南盆地乐东凹陷晚中新世深水扇以及中央峡谷粗碎屑物质的主要沉积物供给来源区。

Provenance analysis of Huangliu Formation of the central canyon system in the deepwater area of the Qiongdongnan Basin

The provenance analysis is the premise and basis of lithofacies-paleogeography studies because sediment supply controls the distribution and physical properties of sandstone. In this paper,the provenance characteristics of Huangliu formation in the central Canyon are studied using the new drilling data,combining seismic profiles,through methods like heavy minerals assemblage and zircon U-Pb age. From seismic profiles,it is presumed that sediments coming from the Hainan Uplift and Kuntum Uplift were deposited on the deltas,which were re-transported into the shelf-slope and submarine fans supplying abundant debris sediments to fill the Central Canyon. Samples of Huangliu Formation from new wells show high content in leucoxene,garnet and magnetite,which is similar to the strata under the influence of Blue River in Yinggehai Basin and Lishui-Qiubin River in Qiongdongnan Basin. Zircon U-Pb dating analysis shows that,characteristics of zircon U-Pb age distribution of the samples in Huangliu Formation of the central canyon with age Atlas 30-2 000 Ma range,is similar as the drilling samples effected by Kontum uplift provenance in Yinggehai Basin and the samples gathered from modern river of Vietnam with very consistent ages and abundance.In summary,the Central Canyon System is under the influence of various provenance including the ancient Hainan Uplift and the Kunchong Uplift. The western provenance system,which is mainly composed of Kunchong Uplift in Vietnam,was the main sediment supply for the submarine fan developed during late Miocene in Ledong Sag and the turbidity sandstone deposited later in the Central Canyon System.