冲绳海槽中段沉积物物源识别及其热液活动指示

冲绳海槽中段热液活动区表层沉积物的主、微量和稀土元素分析结果表明:区内沉积物主要由陆源物质与热液源物质组分组成,Hg、Au、Sb、Cu、Pb、Zn、Ba、As、Fe和Co等微量元素富集;沉积物的化学风化程度中等,A-CN-K图解表明其暂未受到钾交代影响,且其母岩成分接近花岗闪长岩;北美页岩标准化稀土配分模式曲线整体较为平坦,轻重稀土分馏较弱,部分样品具有与热液流体类似的明显正铕异常.受热液活动影响,部分沉积物中的Fe、Cu、As、Pb和Zn显著富集,结合样品所处站位,整体显示含金属沉积物-过渡沉积物-正常沉积物的空间分配模式.结合(La/Sm)N、(La/Yb)N比值指示区内沉积物的陆源物质主要来自于黄河与台湾岛河流.

Provenance identification of sediments in the central Okinawa Trough and its implications for hydrothermal activity

Surface samples in hydrothermal fields of the central Okinawa Trough are analyzed for major and trace element composition. Results propose that the samples are mainly composed of terrestrials and hydrothermal materials. The deposits are an enrichment of trace elements such as Hg, Au, Sb, Cu, Pb, Zn, Ba, As, and Co, which have moderate chemical alteration index (CIA) values and are not affected by potassium replacement. The A-CN-K diagram shows that the parent rock composition is close to granodiorite. The standardization rare earth elements (REE) distribution pattern of North American Shale is relatively flat, which implies the slight fraction between light-group rare earth elements (LREE) and heavy-group rare earth elements (HREE). Part of samples have positive Eu anomalies similar to those of hydrothermal fluids. Under the influence of hydrothermal activity, some sediments are prominently enriched in Fe, Cu, As, Pb, and Zn. Combined with the location of the samples, the spatial distribution shows a pattern of metalliferous sediments-transitional sediments-normal sediments. This pattern and ratios of (La/Sm)_N and (La/Yb)_N indicate that the terrigenous component of the samples in the central Okinawa Trough comes mainly from the Yellow River and Taiwan island river.