Continental collision, orogenesis and arc magmatism of the Miocene Maramuni arc, Papua New Guinea

Abstract

The Maramuni arc represents the only continuous record of the tectonic evolution of Papua New Guinea during the Miocene, and hence provides an opportunity to gain insight into subduction dynamics, orogenesis and crustal processes that operated throughout this dynamic period. We present an integrated U-Pb geochronology, Hf isotope and geochemical investigation of the Maramuni arc utilizing a suite of intrusive rocks from the Kainantu region of the eastern Papuan Highlands that span the Late Miocene from ca. 12 Ma to 6 Ma. The magmatic rocks formed from ca. 12-9 Ma have compositional affinities of subduction-zone magmas, but record increasing incompatible trace element contents and decreasing εHf with time, which we interpret to reflect a progressive increase in the crustal component of the magmas. Porphyry suites emplaced at 7.5-6 Ma are distinct from the older magmatic rocks by their marked HREE-depletion, which reflects a dramatic shift in arc-mantle dynamics. Based on these results we propose a revised geodynamic model for the tectonic

Tectonic Mode Switches Recorded at the Northern Edge of the Australian Plate During the Pliocene and Pleistocene

“…At least two major accretion events are recognized along the length of New Guinea between ~45 Ma and the present day; (1) the obduction of the Papuan Ophiolites, accretion of volcanic arc fragments of Pacific affinity, and the development of a widespread unconformity across western New Guinea and the southern Molucca's during the Oligo‐Miocene (Ali & Hall, ; Gold, Burgess, et al, ; Gold, White, et al, ; Hall, ; Hall, Ali, & Anderson, ; Hall, Ali, Anderson, & Baker, ; Holm et al, , ), and (2) accretion of the additional arc material during the Pliocene‐Pleistocene (e.g., Davies, ; Dow et al, ; Holm et al, ; Monnier et al, ; Pigram & Symonds, ; Pubellier et al, ). These accretionary events are considered to have been driven by the northward advance of the Australian Plate since the Eocene and 40° clockwise rotation of the Philippine Sea Plate along the northern margin of the Australian Plate between the Early Neogene and present day (Ali & Hall, ; Hall, , ; Hall, Ali, & Anderson, ; Hall, Ali, Anderson, & Baker, ; Hill & Hall, ).…”

Post 8 Ma reconstruction of Papua New Guinea and Solomon Islands: Microplate tectonics in a convergent plate boundary setting

“…The Trobriand trough (Fig. 2) is one of the most contentious tectonic elements in the region (Hall and Spakman, 2002;Holm et al, 2015). The lack of seismicity indicative of southward subduction, combined with the absence of convincing tomographic…”

“…The Pocklington trough marks the southern margin of the Woodlark Basin and Papuan Peninsula. There is no evidence for recent convergence at the Pocklington trough and it is therefore considered to represent a relict trench that accommodated north-dipping subduction of the Australian plate beneath New Guinea (Hill and Hall 2003;Cloos et al, 2005;Webb et al, 2014;Holm et al, 2015). Closure of the Pocklington trough and cessation of subduction was caused by collision of the Australian continent with an outboard proto-New Guinea terrane at ca.…”

“…Closure of the Pocklington trough and cessation of subduction was caused by collision of the Australian continent with an outboard proto-New Guinea terrane at ca. 12 Ma (Webb et al, 2014;Holm et al, 2015).…”

Different styles of modern and ancient non-collisional orogens and implications for crustal growth: a Gondwanaland perspective

“…If so, middle Miocene subduction was to the south, either part of a long-term southwards subduction and changing westwards into a transform (Hill and Hall 2003) or a reversal of previous subduction to the north on a trench north of New Guinea (Davies 2009(Davies , 2012Findlay 2003;Hill and Hall 2003). Holm et al (2014) expanded the arc concept to include all late Cenozoic igneous activity, and related it to north-dipping subduction on a plate boundary, south of New Guinea (Pocklington Trough (PT), Fig. 2A), which progressively steepened with subsequent slab detachment.…”