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湘西寒武纪早期黑色岩系中富含源于上层海水生物体的有机质,其稀土元素(REE)特征不被碎屑物质干扰,能有效地反映海洋上层水体的古环境特征.样品中作为有机质主体的干酪根的重稀土富集、Ce负异常、Y正异常和Eu无明显异常等特点与现代海水一致,其特征可能反映古海洋上层水体的氧化还原信息.扬子地台各相区沉积剖面底部可能出现滞流(或硫化)环境,随后沉积环境逐渐氧化.全岩样品中Ce的负异常可能由有机质提供,Ce/Ce*值由剖面底部的较低值向上逐渐升高可能意味着海洋上层水体含氧量的逐渐上升,而海水含氧量逐渐升高或许是由寒武纪早期海洋底部硫化环境的减弱所导致.
The early Cambrian black rock series in the western Hunan Province are rich in organic matter originating from the upper marine organism and their REE characteristics are not disturbed by debris and can effectively reflect the paleoenvironmental characteristics of the upper marine water bodies. The characteristics of heavy REE enrichment, negative Ce anomaly, positive Y anomaly and no obvious Eu anomaly are consistent with the modern seawater, which may reflect the redox information of the upper ocean water in the ancient ocean. A stagnant (or sulfidation) environment may appear at the bottom followed by a gradual oxidation of the sedimentary environment.Ce negative anomalies in whole-rock samples may be contributed by organic matter and a Ce / Ce * value rising upward from a lower value at the bottom of the profile may mean that the ocean The oxygen content of the upper water body gradually increased, and the gradual increase of oxygen content in the sea water may be caused by the weakening of the sulfide environment at the bottom of the ocean in the early Cambrian.