Proceedings, initial reports, Ocean Drilling Program, Leg 153, Mid- Atlantic Ridge

Leg 153 represents a second ODP offset drilling leg, in this case devoted to drilling the plutonic foundation of slow-spreading (~25 mm/yr) oceanic lithosphere in the Mid-Atlantic Ridge (MAR) at the Kane Transform (MARK) area. Exposures of coarse-grained mafic and ultramafic rocks on the median valley walls are considered to be <1 m.y. old and to have resulted from mechanical extension of the axial lithosphere during a period of very limited magmatic construction. The sites drilled during Leg 153 are located in the footwalls of major detachment faults cutting ultramafic and gabbroic rocks. The primary goals of drilling include the investigations of the mantle flow and partial melting history of the ultramafic rocks, the igneous crystallization history of the gabbroic rocks, and the deformation and metamorphism attending seafloor spreading in this particular environment. The introduction and explanatory notes are followed by the site chapters. Most of the volume is also reproduced on CD-ROM, found at the back of the volume. The CD-ROM includes the text and ASCII data files from Volume 153, along with data which could not be printed in Volume 151. -after Authors