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黄铁矿是富有机质沉积的特征矿物。根据TOC/S、TOC/DOP、S/Fe关系以及S-TOC-Fe多重线性回归分析结果对三水盆地古近系土布心组红岗段黑色页岩中沉积黄铁矿的形成及其控制因素进行了分析。土布心组红岗段黑色页岩的黄铁矿有成岩黄铁矿和同生黄铁矿两种成因组分。红岗段下部(亚段A)有机碳含量普遍较低,底部水体以弱氧化条件为主,硫酸盐还原作用发生于沉积物/水界面以下,黄铁矿为成岩成因,其形成主要受有机质的限制。红岗段中上部(亚段B和C)的沉积条件变化频繁,其有机碳含量变化幅度大。富有机质(TOC>4%)岩层形成于缺氧的底部水体条件下。水体中可含H2S,碎屑铁矿物在埋藏之前即与之在水体中反应形成同生黄铁矿。这一过程不受有机质的限制,而是受活性铁与H2S接触时间的限制。同时,由于大量淡水输入导致硫酸盐浓度的降低,从而对硫化物形成有一定的限制作用。对于低有机质(TOC<4%)样品,黄铁矿由同生和成岩组分组成。其中以成岩黄铁矿为主,其形成过程主要受有机质限制,而同生黄铁矿受铁矿物与H2S接触时间的限制。
Pyrite is a characteristic mineral rich in organic matter. Based on the results of TOC / S, TOC / DOP, S / Fe and S-TOC-Fe multiple linear regression analysis, the formation and controlling factors of sedimentary pyrite in the black shale of Honggang section of the Paleogene in the Sanshui Basin Analyzed. The burr pyrite in Honggang section of Tubuxin Formation has two genetic components, diagenetic pyrite and syngenetic pyrite. Organic carbon content is generally low in the lower part of Honggang section (sub-section A), with weak oxidation at the bottom and sulfate reduction occurring below the sediment / water interface. Pyrite is a diagenetic gene that forms mainly organic matter limit. The depositional conditions of the upper and middle parts of the Honggang section (sub-sections B and C) change frequently, and their organic carbon content changes greatly. Rich organic matter (TOC> 4%) rock formation in the bottom of the water under hypoxia conditions. Water can contain H2S, detrital iron ore minerals buried in the immediate reaction with the formation of metazoan pyrite. This process is not subject to the limitations of organic matter, but by the active iron and H2S contact time constraints. At the same time, sulphide formation has a limited effect due to the reduction of sulphate concentration due to the large amount of freshwater input. For low organic matter (TOC <4%) samples, pyrite consists of syngenetic and diagenetic components. Among them, diagenetic pyrite is the main component, and its formation process is mainly limited by organic matter, while the same pyrite is limited by the contact time of iron minerals and H2S.