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doi:10.2204/iodp.proc.301.205.2008

Introduction

As seawater circulates through the ocean crust, it dissolves igneous minerals, precipitates secondary minerals, and exchanges cations and anions with crustal rocks. One factor that determines bulk rates of such reactions is the specific surface area (SSA) (Hodson, 1999). SSA is defined as the area per unit mass of a sample and has units of L²/M (e.g., m²/g). It is commonly measured on laboratory prepared powdered, crushed, or granular material used in dissolution/alteration studies. Although SSA of igneous minerals has been reported (e.g., Brantley and Mellott, 2000), there are no reported values for subsurface marine basalt, the most common rock type of Earth's crust.

In this investigation we present the first reported values of SSA for rock samples recovered from the ocean crust. We selected 13 samples from a short vertical section of igneous rock from a borehole drilled on the east flank of Juan de Fuca Ridge. Bulk density, porosity, P-wave velocity, and degree of alteration were measured at sea, and SSA was measured in a shore-based laboratory.

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