Rapid magmatic processes accompany arc-continent collision: the Western Bismarck arc, Papua New Guinea

New U-Th-Ra, major and trace element, and Sr-Nd-Pb isotope data are presented for young lavas from the New Britain and Western Bismarck arcs in Papua New Guinea. New Britain is an oceanic arc, whereas the latter is the site of an arc-continent collision. Building on a recent study of the Manus Basin...

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Bibliographic Details
Published in:Contributions to Mineralogy and Petrology
Main Authors: Cunningham, Heather, Gill, Jim, Turner, Simon, Caulfield, John, Edwards, Louise, Day, Simon
Format: Article in Journal/Newspaper
Language:English
Published: 2012
Subjects:
Papua New Guinea arcs
Arc lavas
Continent-arc collision
U-series isotopes
U-SERIES DISEQUILIBRIA
BRITAIN ISLAND-ARC
LOWER CRUST
SLAB
SUBDUCTION
KAMCHATKA
CONSTRAINTS
EVOLUTION
GENESIS
BENEATH
/dk/atira/pure/subjectarea/asjc/1900/1906
Geochemistry and Petrology
/dk/atira/pure/subjectarea/asjc/1900/1908
Geophysics
Bismarck
Kamchatka
Online Access:https://pure.qub.ac.uk/en/publications/40694f83-ed0c-44c7-9845-2702fdd2f2e0
https://doi.org/10.1007/s00410-012-0776-y
Description
Summary:New U-Th-Ra, major and trace element, and Sr-Nd-Pb isotope data are presented for young lavas from the New Britain and Western Bismarck arcs in Papua New Guinea. New Britain is an oceanic arc, whereas the latter is the site of an arc-continent collision. Building on a recent study of the Manus Basin, contrasts between the two arcs are used to evaluate the processes and timescales of magma generation accompanying arc-continent collision and possible slab detachment. All three suites share many attributes characteristic of arc lavas that can be ascribed to the addition of a regionally uniform subduction component derived from the subducting altered oceanic crust and sediment followed by dynamic melting of the modified mantle. However, the Western Bismarck arc lavas diverge from the Pb isotope mixing array formed by the New Britain and the Manus Basin lavas toward elevated Pb-208/Pb-204. We interpret this to reflect a second and subsequent addition of sediment melt at crustal depth during collision. U-238 and Ra-226 excesses are preserved in all of the lavas and are greatest in the Western Bismarck arc. High-Mg andesites with high Sr/Y ratios in the westernmost arc are attributed to recent shallow mantle flux melting at the slab edge. Data for two historical rhyolites are also presented. Although these rhyolites formed in quite different tectonic settings and display different geochemical and isotopic compositions, both formed from mafic parents within millennia.

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