东海陆架泥质沉积物中固相Fe形态及其对有机质、Fe、S成岩路径的制约意义

Speciation of solid-phase iron in mud sediments collected from the shelf of the East China Sea:Constraints on diagenetic pathways of organic matter,iron,and sulfur

利用化学提取法对中国东海具有不同陆源物质的内陆架（0701）和外陆架（0508）泥质沉积物柱样进行的多种形态固相铁含量及其剖面分布研究结果表明, Fe 形态及其分布对有机质、Fe 和S 早期成岩作用具有明显的制约意义。0508 和0701 两站点柱状沉积物总活性Fe 平均含量分别为12.14 mg/g 和10.03 mg/g, 其中,氧化物-Fe（Ⅲ）约占18.3%-58.3%, Fe3S4-Fe 占33.7%-76.8%, FeS-Fe 占2.0%-8.1%, FeS2-Fe 仅占1.4%-3.3%。Fe3S4-Fe 是活性Fe 的主要积累形态, 其成因主要是由东海较低的活性有机质与较高的活性Fe 等特定的物源条件决定的; 较高的活性Fe 也抑制了黄铁矿的形成。0701 站点所在的内陆架沉积物中, Fe 的异化还原可能是Fe（Ⅲ）还原的重要路径, 是有机质矿化重要的电子受体; 而0508 站点所在的外陆架沉积物中, Fe 的非生物还原可能是Fe 还原的主要路径, 有机质矿化主要以？ 24SO 为电子受体。这些不同的机制也导致了0508 站点沉积物中总硫化物结合态Fe（Ⅱ）含量较0701 站点的更高。

Two cores of mud sediments （0701 and 0508） were collected from the inner and outer continental shelves of the East China Sea and analyzed for the speciation of solid-phase iron using combined chemical extraction techniques. The results show that the average contents of total reactive iron in cores 0508 and 0701 are 12.14 mg/g and 10.03 mg/g, respectively. Among various forms of reactive iron, Fe3S4-Fe is the most important one, accounting for ca. 33.7%–76.8% of total reactive iron. Oxide-Fe （Ⅲ） accounts for ca. 18.3%–58.3%, FeS-Fe for ca. 2.0%–8.1%, and FeS2-Fe for only 1.4%–3.3%, of the total reactive iron, respectively. High fraction of transient phase Fe3S4 is probably due to a synergetic result of low amount of labile organic matter and high amount of reactive iron in the sediments. High amount of reactive iron may also have caused effective hysteresis of pyritization of iron. In the inner continental shelf sediments （core 0701）, dissimilatory iron （Ⅲ） reduction is likely an important pathway of iron reduction and important electron acceptor for organic matter remineralization. Iron （Ⅲ） reduction in the outer shelf sediment （core 0508）, on the other hand, is largely abiotic by sulfide due probably to somewhat higher amount of labile marine organic matter, and therefore 2-SO4 is the dominant electron acceptor for organic matter remineralization. The different pathways above rendered total sulfide-Fe （Ⅱ） higher in core 0508 than in core 0701.