7. Data Report: Chemical and Isotopic (S, Sr) Composition of Anhydrite from ODP Leg 193, PACMANUS Hydrothermal System, Manus Basin, Papua New Guinea¹

Wolfgang Bach,² Stephen Roberts,³ and Ray A. Binns⁴

ABSTRACT

Sr and S isotope data as well as trace element data for anhydrite samples from Sites 1188 and 1189 in the PACMANUS hydrothermal area are presented here. ⁸⁷Sr/⁸⁶Sr ratios range from 0.7050 to 0.7086, suggesting that the anhydrites precipitated from fluids that were variably influenced by entrained seawater (0%–89%). ³⁴S values range between 18.1 and 22.5, indicating the main source of sulfate is seawater that may be affected to small extents by sulfide oxidation or magmatic sulfate input (³⁴S < 21) and minor sulfate reduction (³⁴S > 21). Rare earth element (REE) concentrations are highly variable, particularly at Site 1188. Chondrite-normalized REE pattern shapes comprise light REE enriched, light REE depleted, mid-REE enriched, and variable positive and negative Eu anomalies. Significant correlations between trace element and isotopic compositions are lacking. Anhydrite from Site 1188, a site of diffuse venting, has systematically lower ³⁴S and higher Sr contents and somewhat lower average ⁸⁷Sr/⁸⁶Sr than anhydrite from Site 1189. This is possibly a consequence of the different fluid flow regime with diffuse flow at Site 1188 and focused flow at Site 1189.

¹Bach, W., Roberts, S., and Binns, R.A., 2005. Data report: Chemical and isotopic (S, Sr) composition of anhydrite from ODP Leg 193, PACMANUS Hydrothermal System, Manus Basin, Papua New Guinea. In Barriga, F.J.A.S., Binns, R.A., Miller, D.J., and Herzig, P.M. (Eds.), Proc. ODP, Sci. Results, 193 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/193_SR/214/214.htm>. [Cited YYYY-MM-DD]

²Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole MA 02543, USA. wbach@whoi.edu

³Southampton Oceanography Centre, Empress Dock, University of Southampton SO14 3ZH, United Kingdom.

⁴CSIRO Exploration and Mining, PO Box 136, North Ryde NSW 2113, Australia.

Initial receipt: 12 March 2004
Acceptance: 13 October 2004
Web publication: 26 January 2005
Ms 193SR-214