Pyrite Formation in Organic‐rich Clay, Calcitic and Coal‐Forming Environments
Pyrite Formation in Organic‐rich Clay, Calcitic and Coal‐Forming Environments
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DOI：
10.1111/j.1755-6724.2006.tb00278.x
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发表时间：
2006-08
期刊：
影响因子：
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通讯作者：
G. Dević;P. Pfendt;B. Jovančićević;Z. Popović
中科院分区：
文献类型：
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作者：
G. Dević;P. Pfendt;B. Jovančićević;Z. Popović
摘要研究了中新世淡水混合沉积物（粘土、砂岩或页岩中的煤屑）与连续褐煤层交替形成的黄铁矿形成过程的早期成岩特征。基于丰富的矿物，可区分以下主要沉积环境：伊利石-蒙脱石（I-M）、方解石（Ct）和成煤环境（CL）。对于这些水文地球化学不同的环境中的黄铁矿形成过程中的限制因素（硫酸盐和铁的可用性，有机质的量和有机硫的参与）的影响进行了评估相关性分析。这些限制因素在特定环境中的影响存在显着差异。考虑到腐殖物质的不同氧化活性、铁络合物和表面络合物形成特性取决于环境的pH值和吸附活性粘土矿物的丰度，解释了这些差异。在具有相对低的pH值和含有粘土矿物的环境（I-M-和CL-环境）中，腐殖物质（Hs）对黄铁矿前体的氧化活性被大大阻止，但黄铁矿的形成取决于反应性铁的可用性作为络合物形成的结果。相反，在pH值较高的环境中，由于是方解石，Hs的氧化活性大大增强，从而氧化黄铁矿的硫前体。有机物的氧化程度可能也是腐殖酸电子受体活性不同的结果。
Abstract The early diagenetic characteristics of pyrite formation processes in a Miocene freshwater sequence of mixed sediments (coal fragments in clays, sandstones or shales) alternating with continuous brown coal layers was investigated. Based on abundant minerals, the following main sedimentary environments were distinguished: the illite‐montmorillonitic (I‐M), calcitic (Ct) and coal‐forming environment (CL). For these hydrogeochemically differing environments the effects of limiting factors on the pyrite formation process (availability of sulphate and Fe, amount of organic matter and participation of organic sulphur) were assessed by correlation analysis. Significant differences in the effects of these limiting factors in the particular environments were observed. These differences were explained taking in account the different oxidative activity, Fe‐complex and surface complex forming properties of humic substances in dependence of pH of environment and the abundance of sorptionally active clay minerals. In environments having a relatively low pH and containing clay minerals (I‐M‐and CL‐environments) the oxidative activity of humic substances (Hs) on pyrite precursors was greatly prevented however pyrite formation depended on reactive Fe availability as the consequence of complex formation. On the contrary, in environments with a relatively high pH, as it was the calcitic, the oxidative activity of Hs was greatly enhanced, thus oxidizing the sulfur precursors of pyrite. The oxidation degree of organic matter was probably also a consequence of the differing activity of the humic electron‐acceptors.