Chemical and isotopic composition of lavas from the northern Mariana Trough: Implications for magmagenesis in back-arc basins

We report the results of a geochemical and isotopic study of mostly basaltic glasses recovered from 25 dredge stations along the northernmost 500 km of the Mariana Trough extension axis. The distribution of samples links regions of seafloor spreading to the south with regions farther north where a p...

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Bibliographic Details
Published in:Journal of petrology 1998-01, Vol.39 (1), p.125-154
Main Authors: Gribble, R F, Stern, R J, Newman, S, Bloomer, SH, O'Hearn, T
Format: Article
Language:English
Subjects:
Marine
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Summary:We report the results of a geochemical and isotopic study of mostly basaltic glasses recovered from 25 dredge stations along the northernmost 500 km of the Mariana Trough extension axis. The distribution of samples links regions of seafloor spreading to the south with regions farther north where a progression of rifting styles accompanies the earliest stages of back-arc basin extension. Petrographic, chemical and isotopic compositions of igneous rocks reflect the changing styles of extension, with typical back-arc basin basalts in the south which become increasingly similar to arc lavas to the north. Felsic lavas also appear along the extensional axis in the north. Glassy, sparsely phyric basalts characterize regions of seafloor spreading. Felsic lavas and porphyritic basalts occur in the northern, rifting portion. Geochemical and isotopic compositions distinguish between mature arc positions (Ce/Pb 20; super(206)Pb/ super(204)Pb >18 times 5, super(87)Sr/ super(86)Sr >0 times 7032, epsilon sub(Nd) < +8) and regions of back-arc spreading (Ce/Pb >10, Ba/La
ISSN:0022-3530
DOI:10.1093/petrology/39.1.125