Chemical Sedimentology of Pelagic Clay Minerals Contained in Pelagic Deep-Sea Cherts

通过对冲绳群岛和北海道172个硅质岩及其伴生沉积岩的地球化学分析，揭示了远洋和半远洋硅质岩的某些地球化学特征。除透明碎屑岩之上的局部基性硅质岩外，远洋硅质岩具有铁、镁高度相关的连续线性曲线特征。此外，对于远洋硅质岩来说，铁和钾的相关性也很高。另一方面，半深海硅质岩具有Fe、Mg、K相关性差的特点。在IE岛和北海道出露的侏罗纪至白垩纪远洋硅质岩，既是位于Ccd以下深海海底的层状红色硅质岩，也是Ccd上方远洋海山上的结核石斑岩。远洋层状红色硅质岩在地层序列中呈单调连续的红色硅质岩产出。陆地上这些远洋硅质岩的地层与现代深部海底的远洋硅质岩的地层学有很好的相关性，无论是在Ccd之下的硅质岩还是在Ccd以上的硅质岩。

Geochemical analyses on 172 cherts and associated sedimentary rocks from the Okinawa Islands and Hokkaido reveal some geochemical characteristics for pelagic and hemipelagic cherts. Excluding some local basal cherts above the hyaloclastite, pelagic cherts are characterized by a continuous linear plots with high correlation between Fe and Mg. As well, the correlation between Fe and K is high for pelagic cherts. On the other hand, the hemipelagic cherts are characterized by poor correlations among Fe, Mg, and K.Jurassic to Cretaceous pelagic cherts, both as bedded red cherts in the abyssal floor below the CCD and as nodular flints on the pelagic seamount above the CCD, are exposed in the Ie Island and Hokkaido. The pelagic bedded red cherts occur as monotonous and continuous red cherts in the stratigraphic succession. The stratigrap of these pelagic cherts on the land is well correlated with the stratigraphy of pelagic cherts, both as cherts below the CCD and as above the CCD, in modern deep-se floors.