Open AccessMantle dynamics, element recycling, and magma genesis beneath the Kermadec Arc‐Havre Trough
Author(s) -
Haase Karsten M.,
Worthington Tim J.,
Stoffers Peter,
GarbeSchönberg Dieter,
Wright Ian
Publication year - 2002
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2002gc000335
Subject(s) - geology , mantle wedge , mantle (geology) , geochemistry , island arc , subduction , slab , crust , basalt , transition zone , volcanic arc , volcano , volcanic rock , petrology , seismology , geophysics , tectonics
New geochemical and isotopic data are presented for lavas from three sites in the Havre Trough‐Lau Basin back arc and six volcanoes along the Kermadec arc. The back arc basalts range from MORB‐like to arc‐like in composition and contain a variable contribution from the underlying slab. The least contaminated MORB‐like back arc lavas from 24°–29°S are low degree partial melts of a source with Pacific MORB isotopic characteristics. A transition occurs at 30°S between the strongly depleted northern Kermadec (and Tonga) arc lavas and the mildly depleted southern Kermadec arc lavas. This transition does not correlate with changes in the back arc extension rate or width but may reflect inhibited mantle wedge replenishment behind the shallower‐dipping northern Kermadec‐Tonga slab. Northern Kermadec lavas require mixing between two components: (1) depleted Havre Trough mantle and (2) fluid derived from altered MORB crust with a slight input of sediment lead. Inter‐volcano differences in fluid compositions probably reflect local variations on the subducting slab rather than mineralogical variation in the mantle wedge. Southern Kermadec lavas require an additional component: (3) Pacific sediment melt. This sediment melt is only detected where the subduction rate is <7 cm/year, and requires thermal heating of the slab to >650°C before passing through the sub‐arc melt generation zone.