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

Please always quote using this URN: urn:nbn:de:bvb:29-opus4-74755
  • 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 theThere 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 gabbros. 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 238U and 226Ra 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.show moreshow less

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Metadaten
Author:Christoph Beier, Wolfgang Bach, Simon Turner, Dominik Niedermeier, Jon Woodhead, Jörg Erzinger, Stefan Krumm
URN:urn:nbn:de:bvb:29-opus4-74755
DOI:https://doi.org/10.1093/petrology/egu077
Title of the journal / compilation (English):Journal of Petrology
Document Type:Article
Language:English
Year of Completion:2015
Embargo Date:2016/09/05
Publishing Institution:Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Release Date:2016/09/08
Tag:Manus Basin; South East Rift; differentiation; oceanic spreading centre; silicic lavas
SWD-Keyword:-
Volume:56
Issue:2
Pagenumber:255 - 272
Original publication:Journal of Petrology 56.2 (2015): S. 255-272. <http://petrology.oxfordjournals.org/content/56/2/255.abstract>
Institutes:Naturwissenschaftliche Fakultät
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
open_access (DINI-Set):open_access
Collections:Universität Erlangen-Nürnberg / Allianzlizenzen: Alle Beiträge sind mit Zustimmung der Rechteinhaber aufgrund einer DFG-geförderten Allianzlizenz frei zugänglich. / Allianzlizenzen 2015
Licence (German):Keine Creative Commons Lizenz - es gilt der Veröffentlichungsvertrag und das deutsche Urheberrecht
Licence (German):National- bzw. Allianzlizenz (nur intern)