Geochemistry of anhydrite - a key to understanding submarine hydrothermal systems

Supervisors:
Wolfgang Bach and Meg Tivey, Marine Chemistry and Geochemistry Department, WHOI

Rationale: The focus of this project is micro-scale geochemical analyses of anhydrite (CaSO4) recovered from the basement underlying submarine hydrothermal sulfide deposits. The isotopic composition of sulfur, oxygen, and strontium, the trace metal contents of anhydrite, and fluid inclusion data provide specific information on formation temperatures, fluid sources, phase separation processes, and seawater entrainment and fluid cooling/heating. These processes have important controls on chemical fluxes into the oceans, the distribution of subcrustal biosphere, and the formation of massive sulfide deposits.

Methodology: Fluid inclusion microthermometry, cathodoluminescense microscopy, electron microprobe analyses, ion microprobe analyses, geochemical modeling (EQ3/6 and GWB codes).

Wider Implications: Subsurface fluid mixing/cooling/heating processes have important implications for chemical fluxes into the oceans, the distribution of subcrustal biosphere, and the formation of massive sulfide deposits.

Suitable For: Students with strong background in geology, mineralogy, and geochemistry.

Training: Microbeam geochemical techniques, geology and geochemistry of hydrothermal systems, geochemical modeling

Additional Relevant Links:

• An introduction of the PACMANUS hydrothermal system

References:

• Mills, R.A. and M.K. Tivey (1999) Sea water entrainment and fluid evolution within the TAG hydrothermal mound: evidence from analyses of anhydrite. In: Cann, J.R, H. Elderfield, and A. Laughton (Eds) Mid-Ocean Ridges, pp. 225-248, Cambridge University Press.
• Tivey, M.K., R.A. Mills and D.A.H. Teagle (1998) Temperature and salanity of fluid inclusions in anhydrite as indicators of seawater entrainment and heating in the TAG active mound, In: Herzig, P.M., S.E. Humphris, D.J. Miller, and R.A. Zierenberg, Proceedings of the Ocean Drilling Program, 158, 179-190.
• Bach W., S. Roberts, D.A. Vanko, R.A. Binns, C.J. Yeats, P.R. Craddock, and S.E. Humphris (2002) Controls of fluid chemistry and complexation on rare earth element contents of anhydrite from the PACMANUS subseafloor hydrothermal system, Manus Basin, Papua New Guinea. Mineralium Deposita, in press. Html file of manuscript.