南海北部柱状沉积物中黄铁矿的分布特征和形貌研究

对南海北部陆坡柱状沉积物样品总有机碳、总硫含量，以及其中的自生黄铁矿形貌、含量进行分析．结果显示，沉积物中黄铁矿（FeS2）、总有机碳（TOC）、总硫（TS）的质量分数分别为0～0，71％、0．37％～1．18％、0．04％～0．81％；黄铁矿和总有机碳、总硫的含量随深度加深逐渐增大，达到峰值后不断减少，三者的分布趋势基本一致；扫描电镜下观察到黄铁矿主要以莓球状集合体和八面体微晶形貌产出，局部层位亦发现管状、生物内膜状和立方体状黄铁矿晶体．表明该区浅表层环境为缺氧环境，硫化物主要以黄铁矿形式产出，其成因与有机质的厌氧氧化作用有关，而甲烷的厌氧氧化作用也可能促使自生黄铁矿的加速形成．莓球状黄铁矿占主导亦指示一种强还原性的缺氧微环境．黄铁矿富集的缺氧环境与下伏地层中天然气水合物分解释放的甲烷有关，为天然气水合物在该区的勘探提供一定的科荤依据．

Distribution characteristic and crystal form of pyrite from the sediment cores on northern South China Sea

Total organic carbon content, total sulfur from the northern of South China Sea were studied. content and form of authigenic pyrite on sediments core samples The result showed that the authigenic pyrite content was ranged from 0 to 0. 71% with an average of 0. 23% ,total organic carbon（TOC） content was from 0.37% to 1.18% with an average of 0.71% and total sulfur（TS） content was from 0. 04% to 0. 81% with an average of 0. 30% in the sediment cores. The contents of the authigenic pyrite, TOC and TS, which increased gradually with depth and declined after the peak, exhibited the same distribution trends. In the sediment core samples, most forms of authigenic pyrite were berry globular aggregates and octahedral micro-crystals, and the tubular, biological endometrial-like and cube-shaped authigenic pyrite crystals on the part layers were also found under the scanning electron microscopy. The study showed that the shallow surface environment in the area was extremely hypoxic and sulfides were the main forms of authigenic pyrite products. The formation was related to aerobic oxidation methane （ AOM）, which had accelerated the authigenic pyrite formation. The existence of berry globular output of the authigenic pyrite suggested a strong reduced and anoxic microenvironment relating the release of natural gas hydrate in the underlying formation. It has provided evidence for the exploration of natural gas hydrate in this area.