Bulk geochemical analyses were carried out on 27 sediment samples located just above the igneous section of the incoming plate along the Costa Rican convergent margin. This pilot study was intended to determine whether hydrothermal activity within the sediment section could be detected within the bulk sediment. The metaliferous index (100 x Al/[Al + Fe + Mn]) values on bulk sediment (24.3 < x < 43.3) are all much lower than the value for deep pelagic sediment (50.8) but higher than the value for the hydrothermal sulfide from the East Pacific Rise (1). The high Zn, Cu, and Co concentrations associated with high Ba content for a constant detrital input (molar Ti/Al = 0.121 ± 0.026) indicate that the transition metal enrichment is not related to volcanic ash but rather to Fe-Mn oxides, sulfides, and barite. These observations testify to a record of hydrothermal activity within the 70 m of sediment overlying the basement.
1Chavagnac, V., Font, L., Milton, J.A., and Croudace, I.W., 2006. Data report: Geochemical analyses of hydrothermally altered sediments from the convergent Costa Rican margin. In Morris, J.D., Villinger, H.W., and Klaus, A. (Eds.), Proc. ODP, Sci. Results, 205 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/205_SR/207/207.htm>. [Cited YYYY-MM-DD]
2National Oceanography Centre, Waterfront Campus, European Way, Southampton SO14 3ZH, United Kingdom. Correspondence author: vmcc@noc.soton.ac.uk
3Department of Earth Sciences, University of Durham, Durham DH1 3LE, United Kingdom.
Initial receipt: 4 March 2005
Acceptance: 22 November 2005
Web publication: 17 April 2006
Ms 205SR-207