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MORB mantle and subduction components interact to generate basalts in the southern Mariana Trough back-arc basin

Gribble, Robert F. and Stern, Robert J. and Bloomer, Sherman H. and Stüben, Doris and O'Hearn, Tim and Newman, Sally (1996) MORB mantle and subduction components interact to generate basalts in the southern Mariana Trough back-arc basin. Geochimica et Cosmochimica Acta, 60 (12). pp. 2153-2166. ISSN 0016-7037. doi:10.1016/0016-7037(96)00078-6.

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We report the results of the first geochemical and isotopic survey of basaltic glasses dredged along the spreading ridge of the southern Mariana Trough (SMT; 15–17°N). This ridge is divided into two segments that have different axial depths, major and trace element compositions, water contents, and isotopic compositions of Sr, Nd, and Pb. Glasses from the shallower, northern segment (N-SMT; 16–17°N) are OL- and QZ-tholeiites that have compositions consistent with a higher degree of mantle melting relative to that of the OL tholeiites from the southern ridge segment (S-SMT; 15–16°N). The N-SMT glasses are similar to basalts erupted near 18°N in the Mariana Trough that have been the focus of previous studies. The more extensive melting inferred for the N-SMT correlates well with higher abundances of water and relative abundances of large ion lithophile and light Rare Earth elements that indicate involvement of a subduction component. The southern ridge segment is deeper and erupts compositions characteristic of lower degrees of melting; this correlates well with a lower proportion of the subduction component, including a suite that is indistinguishable from MORB. The strong correlation between degree of melting, water contents, and LIL elements indicates that hydrous fluxing as well as adiabatic decompression control melting of MORB-like mantle beneath back-arc basins. Details regarding the nature of this hydrous fluxing agent are not known, but it could be water-rich melts related to behind-the-arc volcanoes. These melts may be diverted by the back-arc convective regime, to become entrained in the zone of adiabatic upwelling, where they further stimulate melting.

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Newman, Sally0000-0003-0710-995X
Additional Information:© 1996 Published by Elsevier. (Received March 1.5, 1995; accepted in revised form February 26, 1996) This research was supported by NSF grants OCE-8918481 and OCE-9302162 to RJS and OCE-8917585 to SHB. We appreciate careful reviews by T. Elliott, R. Hickey-Vargas, and J. Sinton. This is UTD Programs in Geosciences Contribution #823. Editorial handling: J. D. Morris
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Issue or Number:12
Record Number:CaltechAUTHORS:20181016-153903020
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Official Citation:Robert F. Gribble, Robert J. Stern, Sherman H. Bloomer, Doris Stüben, Tim O'Hearn, Sally Newman, MORB mantle and subduction components interact to generate basalts in the southern Mariana Trough back-arc basin, Geochimica et Cosmochimica Acta, Volume 60, Issue 12, 1996, Pages 2153-2166, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90295
Deposited By: George Porter
Deposited On:22 Oct 2018 16:07
Last Modified:16 Nov 2021 03:31

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