Origin of Silicic Magmas at Spreading Centres-an Example from the South East Rift, Manus Basin

Beier C, Bach W, Turner S, Niedermeier D, Woodhead J, Erzinger J, Krumm S (2015)

Publication Status: Published

Publication Type: Journal article

Publication year: 2015

Journal

Journal of Petrology Oxford University Press (OUP): Policy B - Oxford Open Option A

Publisher: Oxford University Press (OUP): Policy B - Oxford Open Option A

Book Volume: 56

Pages Range: 255-271

Journal Issue: 2

DOI: 10.1093/petrology/egu077

Abstract

There has been much recent interest in the origin of silicic magmas at spreading centres away from any possible influence of continental crust. Here we present major and trace element data for 29 glasses (and 55 whole-rocks) sampled from a 40 km segment of the South East Rift in the Manus Basin that span the full compositional continuum from basalt to rhyolite (50-75 wt % SiO2). The glass data are accompanied by Sr-Nd-Pb, O and U-Th-Ra isotope data for selected samples. These overlap the ranges for published data from this part of the Manus Basin. Limited increases in Cl/K ratios with increasing SiO2, La-SiO2 and Yb-SiO2 relationships, and the oxygen isotope data rule out models in which the more silicic lavas result from partial melting of altered oceanic crust or altered oceanic gab-bros. Rather, the data form a coherent array that is suggestive of closed-system fractional crystallization and this is well simulated by MELTS models run at 0.2 GPa and QFM (quartz-fayalite-magnetite buffer) with 1 wt % H2O, using a parental magma chosen from the basaltic glasses. Although some assimilation of altered oceanic crust or gabbro cannot be completely ruled out, there is no evidence that this plays an important role in the origin of the silicic lavas. The U-series disequilibria are dominated by U-238 and Ra-226 excesses that limit the timescale of differentiation to less than a few millennia. Overall, the data point to rapid evolution in relatively small magma lenses located near the base of thick oceanic crust; we speculate that this was coupled with relatively low rates of basaltic recharge. A similar model may be applicable to the generation of silicic magmas elsewhere in the ocean basins.

Authors with CRIS profile

Christoph Beier Lehrstuhl für Endogene Geodynamik Stefan Krumm Lehrstuhl für Endogene Geodynamik

Involved external institutions

Universität Bremen DE Germany (DE) Macquarie University AU Australia (AU) The University of Melbourne AU Australia (AU) Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ DE Germany (DE)

How to cite

APA:

Beier, C., Bach, W., Turner, S., Niedermeier, D., Woodhead, J., Erzinger, J., & Krumm, S. (2015). Origin of Silicic Magmas at Spreading Centres-an Example from the South East Rift, Manus Basin. Journal of Petrology, 56(2), 255-271. https://dx.doi.org/10.1093/petrology/egu077

MLA:

Beier, Christoph, et al. "Origin of Silicic Magmas at Spreading Centres-an Example from the South East Rift, Manus Basin." Journal of Petrology 56.2 (2015): 255-271.

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