14. Data Report: Permeability, Resistivity, and X-Ray Computed Tomography Measurements in Samples from the PACMANUS Hydrothermal System1

Gerardo J. Iturrino,2 Richard A. Ketcham,3 Lizet Christiansen,4 and Greg Boitnott5

INTRODUCTION

Magmatic fluids, heat fluxes, and fluid/rock interactions associated with hydrothermal systems along spreading centers and convergent margins have a significant impact on the genesis of major sulfide deposits and biological communities. Circulation of hydrothermal fluids is one of the most fundamental processes associated with localized mineralization and is controlled by inherent porous and permeable properties of the ocean crust. Heat from magmatic intrusions drives circulation of seawater through permeable portions of the oceanic crust and upper mantle, discharging at the seafloor as both focused high-temperature (250–400C) fluids and diffuse lower-temperature (<250C) fluids. This complex interaction between the circulating hydrothermal fluids and the oceanic basement greatly influences the physical properties and the composition of the crust (Thompson, 1983; Jacobson, 1992; Johnson and Semyan, 1994).

During Ocean Drilling Program (ODP) Leg 193, 13 holes were drilled in the PACMANUS hydrothermal system (Binns, Barriga, Miller, et al., 2002). The hydrothermal system consists of isolated hydrothermal deposits lined along the main crest of the Pual Ridge, a 500- to 700-m-high felsic neovolcanic ridge in the eastern Manus Basin. The principal drilling targets were the Snowcap (Site 1188) and Roman Ruins (Site 1189) active hydrothermal fields. Samples from these two sites were used for a series of permeability, electrical resistivity, and X-ray computed tomography measurements.

1Iturrino, G.J., Ketcham, R.A., Christiansen, L., and Boitnott, G., 2004. Data report: Permeability, resistivity, and X-Ray computed tomography measurements in samples from the PACMANUS hydrothermal system. 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/205/205.htm>. [Cited YYYY-MM-DD]

2Borehole Research Group, Lamont-Doherty Earth Observatory, Columbia University, PO Box 1000, 61 Route 9W, Palisades NY 10964, USA. iturrino@ldeo.columbia.edu

3Department of Geological Sciences, The University of Texas, Austin TX 78712, USA.

4US Geological Survey, 345 Middlefield Road, MS 421, Menlo Park CA 94025, USA.

5New England Research, Inc., 331 Olcott Drive, Suite L1, White River Junction VT 05001, USA.

Initial receipt: 22 May 2003
Acceptance: 16 October 2003
Web publication: 19 November 2003
Ms 193SR-205

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