"Moist MORB" axial magmatism in the Oman ophiolite: The evidence against a mid-ocean ridge origin
Christopher J. MacLeod et al., School of Earth & Ocean Sciences, Cardiff University, Cardiff CF10 3AT, Wales, UK. Posted online 20 Feb. 2013; http://dx.doi.org/10.1130/G33904.1.
The Oman ophiolite has axial volcanics and sheeted dikes similar in composition to modern mid-ocean ridge basalt (MORB). It formed at a fast spreading rate and is regarded by many as being directly comparable to ocean lithosphere from the East Pacific Rise. Oman has accordingly assumed great significance in guiding conceptual models for fast-spreading ridge processes. However, there has long been controversy over the geodynamic setting in which the ophiolite formed and the extent to which the analogy can be drawn, because later volcanics in Oman are similar to those found at convergent margins. To some this implies that the entire ophiolite formed above a subduction zone; others, however, maintain that it formed at a true open-ocean mid-ocean ridge, and that the later magmatism documents the initiation of the thrusting that led to ophiolite emplacement. In this paper, Christopher MacLeod and colleagues reexamine the MORB-like affinity of the axial volcanics in Oman and show that they fractionated in the presence of water at concentrations significantly higher than any open-ocean MORB. Instead, trends are identical to those of arc volcanics. Open-ocean models for the Oman ophiolite are therefore ruled out; rather, it may have formed by seafloor spreading above a newly-initiated subduction zone.
Man-made versus natural CO2 leakage: A 400 k.y. history of an analogue for engineered geological storage of CO2
Neil M. Burnside et al., School of Geosciences, University of Edinburgh, Edinburgh EH9 3JW, UK. Posted online 20 Feb. 2013;
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