S, Sr, and Pb isotopic systematics of hydrothermal chimney precipitates from the Eastern Manus Basin, western Pacific: Evaluation of magmatic contribution to hydrothermal system

• DOI: 10.1029/2003jb002912
• Publication Date: 2004-12-26T19:05:45Z
• Authors: Jonguk Kim; Insung Lee; Kyeong‐Yong Lee
• Keywords: δ34S; Seafloor Spreading

Sulfur, strontium, and lead isotopic analyses were performed on chimneys from the hydrothermal vent fields (the PACMANUS Susu knolls) in eastern Manus back arc basin. Lead isotope composition varies a narrow range ( 206 Pb/ 204 Pb = 18.75–18.78, 207 15.51–15.54, 208 38.31–38.40). Strontium ratios 87 Sr/ 86 Sr) of sulfate minerals vary 0.7051 to 0.7077, falling between those seawater (0.7090) fluid end‐member (0.7050). The δ 34 S values are −8.0 −3.9‰ for knolls sulfide, +1.0 +4.3‰ sulfides, +7.4 +20.6‰ sulfate. sulfides have lowest so far reported volcanic‐hosted massive modern seafloor. low sulfates cannot be explained by simple circulation model without an additional source light sulfur. This is also supported presence indicated sulfur strontium chimney sulfates. Biogenic and/or oxidation H 2 after boiling excluded possible sources because lack sediment cover nonequilibrium fractionation at Disproportionation magmatic SO 2, introduced into system through preeruptive degassing, most plausible mechanism observed values. lighter more radiogenic compositions samples indicate that degassing was vigorous than PACMANUS.