南海北部中央峡谷水道的岩相-地球化学特征及其源区性质
Petrography-Geochemistry and Source Significance of Western Canyon Channel of Northern South China Sea

峡谷水道是南海北部琼东南盆地深水区主要储集层，乐东-陵水凹陷黄流组储集岩以粉、细砂岩为主，储层物性好.然而目前针对不同期水道主要物源供给及水道形成的母岩区性质、古风化程度等研究甚少.对中央峡谷西段水道的砂泥岩进行了岩石薄片与重矿物成分观察统计、岩石主量、微量/稀土元素分析，结果表明：岩石类型以岩屑石英砂岩和长石岩屑砂岩为主，崖城、陵水区重矿物分别为磁铁矿、白钛矿、锆石、电气石与白钛矿、石榴石、电气石、锆石的组合；地球化学特征表现为泥岩较砂岩SiO2含量低，Fe2O3、MgO、K2O、稀土含量偏高，与其含有高粘土矿物有关.砂、泥岩Al2O3/TiO2、K2O/Al2O3、K2O/Na2O比值说明物源区富石英、贫钾长石，分别为石英质沉积与中性火成岩源区；砂岩较泥岩具有较高SiO2/Al2O3比值、低ICV、CIA、CIW值，表明源区经历了低-中等程度的风化作用，是稳定构造环境再循环沉积而成，泥岩的形成环境较砂岩动荡.
Canyon channel is the main reservoir of the deepwater area in Qiongdongnan basin in the northern South China Sea. Reservoir stones have good physical properties since they are dominated by powder and fine sandstones. However, there are few studies on the main provenance supply,nature of the parent rock area in different periods of channel formation, and paleo-weathering degree. In this study, it is found that the rock types are mainly debris-quartz sandstone and feldspar-debris sandstone.The heavy mineral assemblages show that they are dominated by magnetite, ilmenite, zircon and tourmaline in Yacheng area, whereas they are dominated by ilmenite, garnet, tourmaline and zircon in Lingshui area. Geochemical characteristics of mudstone show significantly lower SiO2 content, but higher Fe2O3, MgO,K2O and the total amount of rare earth contents relating to high clay minerals than sandstone. Al2O3/TiO2，K2O/Al2O3 and K2O/Na2O ratios in mudstone and sandstone indicate that the source area is enriched in quartz and depleted in potassium feldspar, and is of quartz sediment source, and neutral igneous rock source respectively. The sandstone is characterized with higher SiO2/Al2O3 ratio, lower ICV,CIA and CIW values compared to mudstone, indicating that the source regions have experienced low to moderate weathering, and they are the deposition of recirculation in the stable tectonic environment, whereas the formation environment of mudstone is more active