Mineralogy and Isotope Geochemistry of Active Submarine Hydrothermal Field at Suiyo Seamount, Izu-Bonin Arc, West Pacific Ocean

Abstract

This report presents mineralogical, geochemical and isotopic data on samples obtained using the Benthic Multi-coring System (BMS) to drill a submarine hydrothermal deposit developed in a caldera on the summit of the Suiyo Seamount in the Izu -Bonin Island Arc, south of Japan. This deposit is regarded as the fi rst example of Kuroko-type sulfi de mineralization on a volcano at the volcanic front of an island arc. The mineralization and hydrothermal alteration below the 300 × 150-m area of active venting was investigated to depths of 2 -9 m below the sea fl oor. Drilling beneath the area of active venting recovered a sequence of altered volcanic rocks (dacite lavas, pyroclastic rocks of dacite -rhyolite compositions and pumice) associated with sulfi de veining and patches/veins of anhydrite. No massive sulfi de was found, however, and the subsea-fl oor mineralization to 10 m depth is dominated by anhydrite and clay minerals with some sulfi des. Sulfi de-bearing samples contained high Au (up to 42 ppm), Ag (up to 263 ppm), As (up to 1550 ppm), Hg (up to 55 ppm), Sb (up to 772 ppm), and Se (up to 24 ppm). Electron probe microanalyzer indicated that realgar, orpiment, and mimetite were major As-bearing minerals. The sulfi des were also characterized by high Zn (>10%) compared to Cu (<6.3%) and Pb (<0.6%). The ␦ 202 Hg/ 198 Hg, ␦ 202 Hg/ 199 Hg and ␦ 202 Hg/ 200 Hg of the sulfi de-bearing dacite samples and a sulfi de chimney decreased with increasing Hg/Zn concentration ratio. The variation of the ␦ 202 Hg/ 198 Hg ranged from −2.8 to +0.5 ‰ to relative to S-HG02027. The large range of these ␦ 202 Hg/ 198 Hg was greater than might be expected for such a heavy element and may be due to a predominance of kinetic effects. The variation of ␦ 202 Hg/ 198 Hg of sulfi de-bearing dacite samples suggested that light Hg isotope in the vapor mixed with oxygenated seawater near sea fl oor during mineralization. Lead isotope ratios of the sulfi de were very similar to those of the dacite lava, suggesting that lead is of magmatic origin. The 87 Sr/ 86 Sr ratio (0.70872) of anhydrite was different from that of the dacite lava, and suggests an Sr derivation predominantly from seawater. Hydrothermal alteration of the dacite in the Suiyo hydrothermal fi eld was characterized by Fe-sulfi des, anhydrite, barite, montmorillonite, chlorite/montmorillonite mixed-layer minerals, mica, and chlorite with little

Chimneys in Paleozoic massive sulfide mounds of the Urals VMS deposits: Mineral and trace element comparison with modern black, grey, white and clear smokers

“…7p; Table 4) and is probably similar to clear smokers described in MOR-related vent sites (Bogdanov et al, 2006b). At Suiyo volcano, the chalcopyrite-rich chimneys of black and grey smokers are widespread (Watanabe and Kajimura, 1993;Ishibashi and Urabe, 1995;Marumo et al, 2008). The studied sample of black to grey chalcopyrite-pyrite smokers was presented by T. Urabe.…”

“…Numerous mineralogical data on modern black and white smokers are scattered through a number of publications (e.g., Halbach and Pracejus, 1993;Marumo et al, 2008;Scott, 1997;Lein et al, 2003;Bogdanov et al, 2006;Rona, 2008;Fouquet et al, 2010;Berkenbosh et al, 2012). Little is published on the mineral peculiarities of chimneys from the ancient VMS deposits (Herrington et al 1998;Maslennikova and Maslennikov, 2007;Maslennikov et al, 2009Maslennikov et al, , 2013Revan et al, 2014).…”

Characteristics of Microbial Communities in Crustal Fluids in a Deep-Sea Hydrothermal Field of the Suiyo Seamount

“…Seven boreholes (called APSK01 to APSK07) were drilled on the seafloor using BMS in June 2001, and three boreholes (APSK08 to APSK10) were added in July 2002. The analysis of core samples obtained from the boreholes have indicated that there is an impermeable layer, which consists of clay and anhydrite, at 1–3 m depth below the seafloor, and that over 300°C hydrothermal fluids are trapped below the layer (Urabe et al, 2002; Marumo et al, 2008). …”

Pore Fluid Chemistry Beneath Active Hydrothermal Fields in the Mid-Okinawa Trough: Results of Shallow Drillings by BMS During TAIGA11 Cruise

“…Marumo et al 2008). Although it may be difficult to penetrate the fluid reservoir even with the maximum capacity, drilling by the BMS is accessible to a region where various interactions are expected to be induced by mixing between the hydrothermal component and entrained seawater.…”