Lithology, mineralogy, and origin of serpentine muds recovered from Conical and Torishima Forearc Seamounts: results of Leg 125 drilling

Abstract

Large serpentinite seamounts are common in the forearc regions between the trench axis and the active volcanic fronts of the Mariana and Izu-Bonin intraoceanic arcs. The seamounts apparently form both as mud volcanoes, composed of unconsolidated serpentine mud flows that have entrained metamorphosed ultramafic and mafic rocks, and as horst blocks, possibly diapirically emplaced, of serpentinized ultramafics partially draped with unconsoldiated serpentine slump deposits and mud flows. The clay- and silt-sized serpentine recovered from three sites on Conical seamount on the Mariana forearc region and from two sites on Torishima Forearc Seamount on the Izu-Bonin forearc region is composed predominantly of chrysotile, brucite, chlorite, and clays. -from Authors