|Multistage hydrothermal alteration of gabbroic rocks from the failed Mathematician Ridge|
Stakes, D.; Vanko, D.A. (1986). Multistage hydrothermal alteration of gabbroic rocks from the failed Mathematician Ridge. Earth Planet. Sci. Lett. 79(1-2): 75-92
In: Earth and Planetary Science Letters. Elsevier: Amsterdam. ISSN 0012-821X, more
Gabbros; Hydrothermal alteration; Lithology; ISE, Mathematician Ridge; Marine
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Oxygen isotopic, mineralogical and fluid inclusion data are presented for fresh and hydrothermally altered gabbroic rocks from the failed Mathematician Ridge. The Mathematician Ridge, though initially a fast-spreading ridge presently has a deep central rift valley more typical of slow-spreading rifts. The inner rift walls expose rare plutonic rocks uncomplicated by proximity to deep large-offset fracture zones. Undeformed Mathematician Ridge gabbros preserve most of the original texture and phase compositions and have been only slightly mineralogically or isotopically modified by post-crystallization hydrothermal alteration. Metagabbros have been subjected to a pervasive ductile deformation and recrystallization to foliated rocks composed of aluminous amphibole, low-calcium plagioclase and ilmenite. Oxygen isotope and phase chemical data suggest this event began at temperatures of up to 700 degree C, water-rock ratios of less than one, and produced modified seawater fluids with isotopic compositions of 3.5-6.0 ppt.