This paper presents sulfide mineral occurrence, abundance, and composition in samples from hydrothermally altered peridotite and gabbro recovered during Ocean Drilling Program (ODP) Leg 209 from south of the 15°20´N Fracture Zone on the Mid-Atlantic Ridge at Site 1268. Most of the sulfide minerals occur in veins and halos around veins in serpentinized peridotite. The only sulfide phases reported that occur in proximity to gabbro are those associated with a mafic intrusion into serpentinized peridotite. Sulfide mineral species change predictably downsection but are perturbed coincident with a breccia interpreted to be generated by intrusion of a gabbroic magma. The general downhole trend suggests sulfide mineral precipitation in conditions with decreasing sulfur and oxygen fugacity. Sulfide minerals that indicate precipitation at relatively higher sulfur and oxygen fugacity occur in the central core of the intrusion breccia. Sphalerite makes a fleeting appearance in the sulfide mineral assemblage in samples from the lower part of the intrusion breccia. Strongly contrasting pyrite compositions suggest at least two episodes of pyrite precipitation, but there is no clear morphological distinction between phases. Heazelwoodite, tentatively identified in shipboard examinations, could not be confirmed in this study.
1Miller, D.J., 2007. Sulfide mineralization at Site 1268, Mid-Atlantic Ridge, Ocean Drilling Program Leg 209. In Kelemen, P.B., Kikawa, E., and Miller, D.J. (Eds.), Proc. ODP, Sci. Results, 209: College Station, TX (Ocean Drilling Program), 1–18. doi:10.2973/odp.proc.sr.209.004.2007
2Integrated Ocean Drilling Program, Texas A&M University, 1000 Discovery Drive, College Station TX 77845-9547, USA. miller@iodp.tamu.edu
Initial receipt: 25 January 2007
Acceptance: 20 April 2007
Web publication: 25 June 2007
Ms 209SR-004