HR: 17:00h
AN: V12J-05 INVITED     [PDF]
TI: Burst of High Temperature Seawater Injection Throughout Accreting Oceanic Crust- A Model Derived From the Oman Ophiolite
AU: * Nicolas, A
EM: Adolphe.Nicolas@dstu.univ-montp2.fr
AF: Universit‚ Montpellier II, Place EugŠne Bataillon, Montpellier, 34095 France
AU: Mainprice, D
EM: David.Mainprice@dstu.univ.montp2.fr
AF: Universit‚ Montpellier II, Place EugŠne Bataillon, Montpellier, 34095 France
AB: Following the discovery of a high temperature (800$\deg$C) and a very high temperature (1000$\deg$C) hydrothermal alteration in the crust of the Oman ophiolite, a systematic structural and petrological study has been conducted throughout the entire ophiolite, backed by isotopic geochemistry that is developed in a companion abstract. The results show that the crustal gabbros are extensively altered down to Moho by a large seawater flux, which was channeled through identified recharge and discharge circuits. A physical model explains how microcracks, constituting the recharge system, can propagate through the hot, accreting gabbros at the ridge of origin and how, in spite of their submillimeter width, they provide the large volume of seawater necessary for the observed alteration. Building on these results, we show here that the activity of these microcracks is highly episodic, with bursts of activity lasting only a few days, and that are followed by quiescence periods of a few tens of years. This model of high temperature, oceanic hydrothermal alteration has several implications concerning fast spreading oceanic ridges and related ophiolites.
DE: 1020 Composition of the crust
DE: 1065 Trace elements (3670)
DE: 3035 Midocean ridge processes
DE: 5120 Plasticity, diffusion, and creep
DE: 8005 Folds and folding
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting