Geochemistry of seafloor surface sediment and submarine hydrothermal signature of Tomini Bay, Indonesia

During the Indonesia–Australia Submarine Survey of Hydrothermal Activity (IASSHA) 2001 cruise, several seafloor surface sediment samples were collected from Tomini Bay. The samples were geochemically examined for major and trace-element geochemistry to study the hydrothermal signature fingerprint. The Tomini Bay seafloor surface sediment sampled by gravity coring is relatively enriched in Na, P, S, Ca, Ni, Sr, and Ba mainly from a terrigenous source. The elevated concentrations of Mg, S, Cr, Co and Ni at one site suggest a contribution from a mafic terrigenous source. A manganese-rich sediment layer was detected on the sediment surface with Mn up to 9474.43 ppm. A hydrothermal signature was successfully distinguished from the manganese-rich sediment layer. Despite the lack of hydrothermal precipitates, the geochemistry of the Tomini Bay seafloor surface sediments provides evidence for submarine hydrothermal activity. KEY POINTSSeafloor surface sediment is an alternative proxy for investigating submarine hydrothermal activity.Hydrothermal signature is well recorded in the Fe/Mn-rich sediment layer and can be distinguished from measured concentrations and elemental ratios of Fe, Mn, HFSE (Zr), trace elements (Cu, Ni, Zn, Co, Zr) and REY (Y, Ce).The Mn-rich sediment layer in Tomini Bay seafloor surface sediment preserved hydrothermal fingerprint and confirmed the evidence of an active hydrothermal system in the studied area. Seafloor surface sediment is an alternative proxy for investigating submarine hydrothermal activity. Hydrothermal signature is well recorded in the Fe/Mn-rich sediment layer and can be distinguished from measured concentrations and elemental ratios of Fe, Mn, HFSE (Zr), trace elements (Cu, Ni, Zn, Co, Zr) and REY (Y, Ce). The Mn-rich sediment layer in Tomini Bay seafloor surface sediment preserved hydrothermal fingerprint and confirmed the evidence of an active hydrothermal system in the studied area.

在2001年印尼-澳大利亚海底热液活动潜艇调查（Indonesia–Australia Submarine Survey of Hydrothermal Activity, IASSHA）航次期间，研究团队于托米尼湾采集了多份海底表层沉积物样品。对这些样品开展常量与微量元素地球化学测试，以探究其热液指纹（hydrothermal signature）特征。经重力柱采样（gravity coring）获取的托米尼湾海底表层沉积物，主要富集钠（Na）、磷（P）、硫（S）、钙（Ca）、镍（Ni）、锶（Sr）与钡（Ba），其物质来源以陆源为主。某站位的镁（Mg）、硫（S）、铬（Cr）、钴（Co）与镍（Ni）浓度升高，表明该区域存在镁铁质陆源物质贡献。研究人员在沉积物表层检测到一层富锰沉积层（manganese-rich sediment layer），其锰（Mn）含量最高可达9474.43 ppm。团队成功从该富锰沉积层中识别出热液信号。尽管未发现热液沉淀物（hydrothermal precipitates），但托米尼湾海底表层沉积物的地球化学特征为海底热液活动提供了佐证。

核心要点
1. 海底表层沉积物是开展海底热液活动调查的替代性代用指标（proxy）。
2. 热液信号在富铁锰沉积层（Fe/Mn-rich sediment layer）中得到良好记录，可通过实测浓度以及铁（Fe）、锰（Mn）、高场强元素（HFSE, High Field Strength Elements）、微量元素（trace elements）与稀土元素+钇（REY, Rare Earth Elements plus Yttrium）的元素比值加以区分。
3. 托米尼湾海底表层沉积物中的富锰沉积层保留了热液指纹特征，证实了研究区域存在活跃热液系统。
4. 海底表层沉积物是开展海底热液活动调查的替代性代用指标（proxy）。
5. 热液信号在富铁锰沉积层（Fe/Mn-rich sediment layer）中得到良好记录，可通过实测浓度以及铁（Fe）、锰（Mn）、高场强元素（HFSE, High Field Strength Elements）、微量元素（trace elements）与稀土元素+钇（REY, Rare Earth Elements plus Yttrium）的元素比值加以区分。
6. 托米尼湾海底表层沉积物中的富锰沉积层保留了热液指纹特征，证实了研究区域存在活跃热液系统。