Calcite cements are volumetrically dominant among the most diagenetic constituents in turbidite sandstones of the Paleogene Shahejie Formation in the Dongying Depression. The results show carbonate cements mainly occur in three phases: Calcite I (pre-compaction), Calcite II (post-compaction) and ankerite in the turbidite sandstone. The isotopic composition of Calcite I and Calcite II range from –4.3‰ to 4.4‰, –3.5‰ to 4.3‰ PDB, respectively, suggesting that the calcite cements are mainly derived from the interbedded shales. The early calcite cement precipitated from the mixing of lacustrine and meteoric waters at 38–69°C. The late-phase calcite precipitated from pore waters modified by water-rock interactions at 64–126°C. Two distribution patterns of calcite cements can be identified, depending on their position within the sandstone. The peripheral cementation of the sandstones is near the sand-shale contact. The development of cement is controlled by sandstone thickness and the properties of the interbedded shale. For scattered cementation, the distribution of the calcite cement is not controlled by the sand-shale contact. Calcite cement was preferentially distributed in coarsegrained sandstones, indicating that sandstones with high original permeability are the preferred pathway for the migration of early diagenetic fluids.

中文翻译：

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东营坳陷沙河街组浊积砂岩中方解石胶结物分布规律

在东营凹陷古近系沙河街组浊积砂岩中，方解石胶结物在体积上占主导地位。结果表明，浊积砂岩中碳酸盐胶结物主要出现在三个阶段：方解石I（预压实）、方解石II（后压实）和铁白云石。方解石Ⅰ和方解石Ⅱ的同位素组成分别为–4.3‰～4.4‰、–3.5‰～4.3‰ PDB，表明方解石胶结物主要来源于互层页岩。早期的方解石胶结物是由 38-69°C 的湖水和大气水混合而成的。晚相方解石在 64-126°C 下从经水-岩相互作用改性的孔隙水中沉淀出来。根据它们在砂岩中的位置，可以确定两种方解石胶结物的分布模式。砂岩的外围胶结作用在砂-页岩接触面附近。胶结物的发育受砂岩厚度和互层页岩性质控制。对于分散胶结，方解石胶结物的分布不受砂-页岩接触的控制。方解石胶结物优先分布在粗粒砂岩中，说明原始渗透率高的砂岩是早期成岩流体运移的首选通道。