Felsic volcanism in the Kermadec arc, SW Pacific: crustal recycling in an oceanic setting

Abstract

Large-scale felsic volcanic systems are a common, but not ubiquitous, feature of volcanic arc systems in continental settings. However, in oceanic volcanic arcs the erupted materials are dominated by basalts and basaltic andesites, whereas intermediate compositions are rare and dacites and rhyolites relatively uncommon. The Kermadec arc is an intraoceanic convergent system in the SW Pacific. Volcanoes occur as a continuous arc that is mainly submarine. Despite its simple tectonic setting, felsic magmatism is widespread. In the Kermadec Islands, Macauley Volcano is a basaltic volcano that produced a large felsic eruption about 6000 years ago. A comparable pattern of magmatic evolution is seen on adjacent Raoul Volcano, where basaltic activity built the main edifice of the volcano and where activity during the last 3000 years has been characterized by felsic eruptions of varying size. Elsewhere in the Kermadec arc and in its northward extension, the Tonga arc, felsic eruptions are recorded from 11 of the 30 volcanoes for which petrographic information is available, and in many cases these are the most recent eruptions. Felsic europtions are a widespread recent feature of the arc, and the scale and extent of this magmatism appears to be unusual for a tectonically simple oceanic subduction system. One explanation of the origin of the felsic magmatism is prolonged fractional crystallization from a parental basalt composition, but modelling of the chemical compositions of the felsic rocks does not support this. A second explanation, albeit apparently at odds with the oceanic setting, is crustal anatexis. An important feature of the felsic eruptives from the Kermadec arc is that each tephra sequence or occurrence has a unique chemical composition, although all show the same generalized characteristics. We suggest that this feature supports a model of crustal anatexis rather than fractionation of a range of parental magmas. We also suggest that in the thermal evolution of an oceanic arc system the processes of underplating, together with the continuous magmatic (and thermal) flux, can generate a crustal thickness in which dehydration melting of underplated arc material generates felsic magmas. Further, this condition can represent a unique ‘adolescent’ stage in a developing oceanic arc, as once the felsic melts are extracted the lower crust becomes an infertile residue.

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

“…4; Haase et al 2006). Published whole rock data shows SiO 2 concentrations between 62.2 and 66.2 wt% (Wright and Gamble 1999;Smith et al 2003;Timm et al 2012), which are slightly lower than those of the volcanic glass samples (Fig. 4).…”

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

“…It is therefore possible that there is a general association between silicic products and caldera collapse in the South Sandwich arc as well documented in the Tonga-Kermadec (Worthington et al, 1999;Smith et al, 2003;Wright et al, 2006; I.J. Barker et al, 2012), Izu-Bonin (Fiske et al, 2001;Tani et al, 2008) and Vanuatu (Robin et al, 1993;Monzier et al, 1994) intra-oceanic arcs.…”

Regional setting and characteristics of the Neoproterozoic Wadi Hamama Zn–Cu–Ag–Au prospect: evidence for an intra-oceanic island arc-hosted volcanogenic hydrothermal system

“…Their magmatic affinity ranges from tholeiitic to transitional (Zr/Y < 7). The low-K felsic igneous rocks are common in supra-subduction zone tectonic settings (Smith et al 2003). The PM-normalized patterns of these rocks exhibit negative Nb anomalies (Fig.…”