Mantle dynamics, element recycling, and magma genesis beneath the Kermadec Arc‐Havre Trough

Abstract

[1] 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.

Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

“…Fractionated phases include plagioclase (46-47%), clinopyroxene (33-44%), spinel (~ 7%) and apatite (~ 0.01%) matching the observed phenocrysts in the examined Brothers volcano samples ( Fig. 2; Gamble and Wright 1995; Haase et al 2002Haase et al , 2006de Ronde et al 2005). The modelling curves resemble the observed chemical trends of the Brothers volcano dacites and rhyolites (Fig.…”

“…This includes data from the L'Esperance (Ewart et al 1994(Ewart et al , 1998Turner et al 1997) and the Rumble III and IV (Wysoczanski et al 2006(Wysoczanski et al , 2012 island arc volcanoes, as well as from the Valu Fa Ridge (Davis et al 1990;Vallier et al 1991;Peate et al 2001;Haase et al 2002;Fretzdorff et al 2006;Jenner et al 2015) and the Pual Ridge (Kamenetsky et al 2001;Moss and Scott 2001;Scott 2002, 2005;Sun et al 2004;Jenner et al 2010Jenner et al , 2012, as examples for back-arc volcanism. Three groups of major elements can be distinguished based on their behaviour during magma evolution, i.e., with increasing SiO 2 , including elements with an (1) incompatible (K 2 O, Na 2 O), (2) compatible (MgO, Al 2 O 3 , CaO) and (3) an initially incompatible and later compatible (TiO 2 , FeO T ) character (Fig.…”

Louisville seamount subduction and its implication on mantle flow beneath the central Tonga–Kermadec arc

“…33). A single analysis from the southernmost Lau Basin sampled at 23.9°S 32 , however, shows relatively low (La/Sm) N of B0.6, also suggesting that local source enrichment beneath the Ata region has taken place.…”

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“…Volcanic rocks along the Kermadec arc range in composition from basalt to rhyodacite. Trace element and isotopic data indicate significant magma source heterogeneity both along and across the arc as a result of variable subduction of continent-derived sediments, pelagic sediments, and oceanic crust and/or interaction with continental crust (e.g., Gamble and Wright, 1995;Gamble et al, 1996;Haase et al, 2002;Timm et al, 2012Timm et al, , 2013Timm et al, , 2014.…”