Evolution and interaction of migrating cross‐arc volcanism and backarc rifting: An example from the Southern Havre Trough (35°20′–37°S)

Abstract

The active southern Havre Trough (35020 '-37øS) backarc basin is interpreted to form from the evolution and interaction of migrating cross-arc magmatism, and the progressive development of longitudinal rift grabens. The proposed migration of the proto-Kermadec arc front from the Colville arc at-5 Ma to the active Kermadec arc margin is recorded by the construction of arc edifices trailed across the intervening, and contemporaneously rifling, backarc complex. Migration trails are identified for at least four arc volcano sources. The Rumble V arc migration trail is the most prominent, forming a continuous, high-standing, magmatic arc ridge. These postulated arc trails segment the backarc region and initially limit riff development to the intervening proto-arc crust blocks. Early rifling between the arc volcanoes forms fully developed riff grabens which, with progressive basin widening, propagate longitudinally across the trails of migrating constructional arc magmatism. A model of the balance between rates of constructional arc magma production M• and destructive back-arc (rifling) extension V• is proposed. When V• is high, M• is insufficient to keep abreast of destructional rifting, resulting in small, isolated arc massifs quickly dismembered by rifling. Conversely, when V• is low, M• is sufficiently greater than rifling to produce a continuous, high-standing cross-arc ridge which segments longitudinal riff development. Migrating arc magmatism will be best observed, and preserved, in rifling backarc basins when M• is Y 600 km 3 m.y. 4 1 O0 km 4 of plate boundary and V• is < 25 mm a -•. Introduction Following the recognition ofbackarc basins in the 1970s [e.g., Karig, 1970; Packham and Falvey, 1971 ], early structural and tectonic studies of these extensional settings generally interpreted seafloor spreading as the dominant mechanism of basin opening [e.g., Lawyer et al., 1976; Weissel, 1981 ]. However, more recent studies ofbackarc basins, principally based around seafloor swathmapping and Ocean Drilling Program (ODP) drilling, have demonstrated the importance of crustal rifting in backarc basin tectonism and magmatism [e.g., Taylor et al.These latter studies, from various western Pacific backarc basin sites, are beginning to establish a general, although by no means consistent, consensus of the characteristic tectonic and magmatic processes within the rifting "phase" ofbackarc opening. To date, the most consistent observations are (1) the similarity of backarc rift graben architecture (with alternating half-graben asymmetry) to continental rift systems, (2) the better initial develop-ment of the rift system between the flanking arc volcanoes of the volcanic front, (3) the eruption of mid-ocean ridge basalt (MORB)like (backarc basin basalt; BABB) and arc-related magmas throughout the rifting phase, (4) the development of"pseudo linear magnetic anomalies" from the emplacement of rift magmas into less magnetic arc crust, and (5) the evolution of the rifting "phase" through various stages, including a final stage of ...

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“…These structures strike predominantly northeast (55°-65°), although a conjugate set of faults is oriented subparallel to the elongated Brothers edifice and caldera ( Figure F1B). These bearings are consistent with rifting of the Havre Trough (e.g., Wright et al, 1996;Delteil et al, 2002;Ruellen et al, 2003) and indicate first-order extensional tectonic control on Brothers volcano. The base of Brothers volcano rises from ~2200 mbsl to a continuous caldera rim at 1540 mbsl, with an outer, northwestern rim shoaling to 1320 mbsl ( Figure F2).…”

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

“…Brothers volcano is part of the ~ 1200 km long Kermadec island arc, northeast of New Zealand (Fig. 1a), which post-dates the earliest phase of Havre Trough back-arc rifting (Wright et al 1996(Wright et al , 1998. The elongated volcanic edifice of Brothers is 13 km long, 8 km wide and strikes NW-SE at a water depth of 2200 mbsl (de Ronde et al 2005).…”

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

“…Such long-lived magmatism along narrow loci suggests lithospheric structural control. Cross-arc chains in the Kermadec arc such as Rumble V Ridge are likely to have a similar origin (Wright et al, 1996;Todd et al, 2010;Wysoczanski et al, 2010). However, there is thought to be no age progression along Rumble V Ridge in the Kermadec arc, with recently erupted lava observed along its length, and Wysoczanski et al (2010) concluded that the ridge represents the surface expression of a zone of dyke intrusion in the crust.…”