Publication Type:

Journal Article

Authors:

Constantin, M.

Source:

Contributions to Mineralogy and Petrology, Springer International, Heidelberg-New York, International, Volume 136, Number 1-2, p.111-130 (1999)

ISBN:

0010-7999

Keywords:

crust, East Pacific, East Pacific Rise, faults, harzburgite, igneous rocks, lower crust, mantle, metasomatism, mid-ocean ridges, ocean floors, Pacific Ocean, peridotites, plate tectonics, plutonic rocks, sea-floor spreading, serpentinization, spreading centers, strike-slip faults, transform faults, transition zones, ultramafics, upper mantle

Abstract:

Mafic and ultramafic rocks sampled in the Garrett transform fault at 13 degrees 28' on the EPR provide insight into magmatic processes occurring under a fast-spreading ridge system. Serpentinized harzburgite has modal, mineral and bulk chemical compositions consistent with being mantle residue of a high degree of partial melting. Geothermometric calculations using olivine-spinel pairs indicate a mean T of 759 + or - 25 degrees C for Garrett residual harzburgite similar to the average of 755 degrees C for tectonite peridotites from slow-spreading ridges. Results of this study show that MOR peridotites are subject to both fractional melting and metasomatic processes. Magma-harzburgite interactions are very well preserved as pyroxenite lenses, plagioclase dunite pockets or dunitic wall rock to intrusive gabbros. Ferrogabbro dykes have been intruded at the ridge-transform intersection; as they represent the last event in a succession of gabbro intrusives into the peridotite, they probably constrain the origin of the entire peridotite massif to the same location.

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2000-016122<br/>Garrett Massif<br/>Garrett transform fault