Elemental and isotopic compositions of the hydrothermal sulfide on the East Pacific Rise near 13°N

Abstract

The mineralogical, elemental, and isotopic characteristics of a hydrothermal sulfide sample from one dredge station (12°42.30′N, 103°54.48′W, water depth 2655 m) on the East Pacific Rise near 13°N were analyzed. The hydrothermal sulfide was composed mainly of sphalerite, chalcopyrite, and pyrite and was a Zn-rich sulfide; in layer ep-s-1, goethite formed by secondary oxidation was found. The concentrations of rare elements, such as Li (0.15×10 −6 -0.30×10 −6 ), Be (0.01×10 −6 -0.05×10 −6 ), Zr (73.8×10 −9 -1344×10 −9 ), Nb (8.14×10 −9 -64.7×10 −9 ), Hf (2.54×10 −9 -28.0×10 −9 ), and Ta (0.203×10 −9 -1.21×10 −9 ), were far lower in the hydrothermal sulfide than in the ocean crust, whereas the content of Au was higher and the contents of Co, Ni, Sr, Cs, Ba, Bi, and U were low. The correlations between Zn and Cr, Cd and Ga, Cu and P, P and In (R 2 > 0.8) were positive, whereas those between Zn and Fe, Cu, and Ba (R 2 > 0.8) were distinctly negative. From low-temperature mineral assemblages to high-temperature mineral assemblages, the spatial distributions of dispersive and rare elements (e.g. In, Li, Cs) in the hydrothermal sulfide displayed corresponding variations. The variations observed in some elements (e.g., Cd, Cs, P) are controlled by Zn, Fe, and Cu sulfides, respectively. Seafloor weathering accounts for the enrichment of V, Mn, and rare earth elements (REE) in the henna sulfide-oxidation layer that bears the secondary oxide mineral, leading to identical REE patterns for this layer (ep-s-1) and seawater. Seafloor weathering also distinctly affects the correlations between the element ratios of the hydrothermal sulfide. From high-temperature mineral assemblages to low-temperature mineral assemblages, Fe content and δ 34 S value of the hydrothermal sulfide increase gradually, and Zn content and lead isotopic ratios decrease gradually on the contrary, which indicate the influences of seawater on elements and the sulfur and lead isotopic compositions enhance gradually during the formation of hydrothermal sulfides. variation, element, isotopic composition, hydrothermal sulfide, East Pacific Rise 13ºNCitation:Zeng Z G, Chen D G, Yin X B, et al. Elemental and isotopic compositions of the hydrothermal sulfide on the EastThe history of some submarine hydrothermal activities is recorded in seafloor hydrothermal sulfides. Thus, studies of the structure and the mineral, elemental, and isotopic composition of seafloor hydrothermal sulfides can help us understand the fluid evolution that occurs during the formation of hydrothermal sulfides and to elucidate the characteristics of the interaction between deep fluid and rock as well as the material contributions of seawater, it is one of the important research directions of submarine hydrothermal geology (submarine hydrothermal geology includes hydrothermal geochemistry (objects of study, including vent fluid, hydrothermal plume and subseafloor fluids, etc.), hydrothermal

Sulfur and lead isotopic compositions of massive sulfides from deep-sea hydrothermal systems: Implications for ore genesis and fluid circulation

“…At the EPR near 13°N, 11°N, and 1-2°S, the KHF, EHF, the MAR near 13°S, the area A, and the S99HF, the seafloor hydrothermal sulfides are hosted by mid-ocean ridge basalts (MORBs) (e.g., Kumagai et al, 2008;Zeng et al, 2010Zeng et al, , 2014Zeng et al, , 2015a. The KHF is situated on basaltic rocks, but the hydrothermal fluids also interact with and circulate through ultramafic rocks (Nakamura et al, 2009).…”

“…These values are within the range of previously reported analyses of hydrothermal sulfides from the EPR near 13°N (δ 34 S values from 0.4 to 5.0‰, avg. 2.7‰, n = 75, Bluth and Ohmoto, 1988;Stuart et al, 1995;Zeng et al, 2010), 11°N (δ 34 S values from 2.2 to 4.9‰, avg.…”

“…Sulfur (S) and lead (Pb) isotopes are powerful tracers for exploring seafloor hydrothermal processes, fluid-rock interaction, and magmatic activity, in order to interpret the origin of hydrothermal ore deposits, in particular the sources of S and Pb in sulfide minerals (e.g., Shanks and Niemitz, 1982;Fouquet and Marcoux, 1995;Ohmoto and Goldhaber, 1997;Bjerkgård et al, 2000;Hannington et al, 2005;Seal, 2006;Yao et al, 2009;Zeng et al, 2010;Aoyama et al, 2014;McDermott et al, 2015). The S and Pb isotope characteristics of massive sulfide deposits from modern seafloor hydrothermal systems in mid-ocean ridges (MORs) and back-arc basins (BABs) have been summarized by Halbach et al (1989Halbach et al ( , 1997, Fouquet and Marcoux (1995), Verati et al (1999), Seal et al (2000), Zeng et al (2000a, b), Shanks (2001), Cousens et al (2002), Kim et al (2004Kim et al ( , 2006, Hannington et al (2005), and Yao et al (2009).…”

“…Lead isotopic compositions of seafloor hydrothermal sulfides indicate that the lead is most likely derived from three sources: (1) basalts at MORs (e.g., Brévart et al, 1981;LeHuray et al, 1988;Fouquet and Marcoux, 1995;Zeng et al, 2010); (2) sediments at BABs (e.g., Halbach et al, 1997;Zeng et al, 2000b) and MORs (e.g., LeHuray et al, 1988;Zierenberg et al, 1993;Cousens et al, 2002); (3) volcanic rocks that have inherited lead from the subducted slab, including basalt and its sediment at BABs Kim et al, 2004). On sediment-starved ridges, the Pb in hydrothermal sulfides is considered to have been mobilized from the volcanic crust during hydrothermal circulation based on the sulfide Pb isotope compositions that are indistinguishable from that of the local basalt (e.g., Brévart et al, 1981;Vidal and Clauer, 1981;LeHuray et al, 1988;Fouquet and Marcoux, 1995;Andrieu et al, 1998;Zeng et al, 2010).…”

“…On sediment-starved ridges, the Pb in hydrothermal sulfides is considered to have been mobilized from the volcanic crust during hydrothermal circulation based on the sulfide Pb isotope compositions that are indistinguishable from that of the local basalt (e.g., Brévart et al, 1981;Vidal and Clauer, 1981;LeHuray et al, 1988;Fouquet and Marcoux, 1995;Andrieu et al, 1998;Zeng et al, 2010). The Pb isotopic compositions of the sulfides are also more homogeneous than the adjacent volcanic rocks, suggesting that the Pb isotopes have been homogenized during hydrothermal circulation, and that the contribution of Pb from seawater and hemipelagic sediments is very low (e.g., Brévart et al, 1981;Vidal and Clauer, 1981;Chen, 1987;Hegner and Tatsumoto, 1987;LeHuray et al, 1988;Fouquet and Marcoux, 1995;Andrieu et al, 1998;Charlou et al, 2002;Yao et al, 2009;Zeng et al, 2010).…”