Interactions between magma and hydrothermal system in Oman ophiolite and in IODP Hole 1256D: Fossilization of a dynamic melt lens at fast spreading ridges

摘要: The transition between the small melt lens observed on top of fast spreading ridge magma chambers and overlying sheeted dike complex marks interface hydrothermal convective system. It is therefore critical to our understanding accretion processes. We present maps two areas Oman ophiolite where this zone as continuous outcrops. Our observations, which include base being crosscut by gabbros, are consistent with episodic injections in a steady state model but also suggest that root these dikes commonly erased vertical movements lens. Dike assimilation possible mechanism for incorporating hydrated phases, result from alteration, during upward migrations its upper boundary. Upward responsible granoblastic overprint stoped diabase xenoliths. This attests reheating previously hydrothermally altered lithologies can even trigger hydrous partial melting due lowering solidus mafic presence water activity. Clinopyroxenes typically low Ti Al content, thus strongly contrasting corresponding magmatic clinopyroxene. may attest recrystallization clinopyroxenes after amphiboles under peculiar conditions at complex. Downward crystallization isotropic gabbros roof, represent partly fossilized Melt fossilization eventually occurs when supply stopped or margins thermal become cooler. migration, stages, processes observations made IODP Hole 1256D. propose general dynamic ridges undergoes downward either eruption/replenishment stages variations hydrothermal/magmatic fluxes.