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南海北部琼东南盆地西区乐东-陵水凹陷梅山组海底扇是当前天然气勘探重点领域,通过研究其岩石类型、轻/重矿物与地球化学特征,判断沉积源区性质,为储层评价及预测提供地质基础.结果表明:岩性以细砂岩为主,发育粉、中-粗砂岩,岩石类型为石英砂岩、岩屑石英砂岩、长石岩屑砂岩,重矿物组合表现为磁铁矿+锆石+电气石+白钛矿;由于发育高铁镁质矿物及粘土矿物,泥岩较砂岩SiO_2含量明显低,Fe_2O_3、MgO、CaO、K_2O含量与稀土总量偏高.说明源区富石英、贫钾长石且含有大量粘土矿物,主要为石英质沉积源区,局部为中性火成岩源区,且经历了低-中等程度的风化作用,是再循环沉积而成.
The sea bottom fan of the Meishan Formation in the Ledong-Lingshui Depression in the western Qiongdongnan Basin in the northern South China Sea is a key area of natural gas exploration. By studying its rock types, light / heavy minerals and geochemical characteristics, the properties of sedimentary source areas can be judged for reservoir evaluation and prediction The results show that the lithology is mainly composed of fine sandstone, with the development of powder, medium-coarse sandstone, quartz rock, lithic quartz sandstone and feldspar lithic sandstone, and the combination of heavy minerals is magnetite + zirconium Stone + tourmaline + baikalite. Due to the development of high-iron magnesia minerals and clay minerals, the content of SiO_2 in mudstone is lower than that of sandstone, and the content of Fe_2O_3, MgO, CaO and K_2O is higher than that of rare earth. Feldspar and contains a large number of clay minerals, mainly quartz source sedimentary area, part of the neutral igneous source area, and experienced a low - moderate degree of weathering, is recirculated deposition.