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

Abstract

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 POINTS 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.