Plutonic rocks of the Median Batholith in eastern and central Fiordland, New Zealand: Field relations, geochemistry, correlation, and nomenclature

Abstract

This paper provides a comprehensive description of all major plutonic rock units in Fiordland between Lakes Poteriteri and Te Anau, and the heads of Doubtful and George Sounds. Plutonic rocks comprise c. 80% of the basement in the area described, the remainder being metase dim entary and metavolcaniclastic rocks. The plutonic rocks, of which c. 50% are granitoids, were emplaced in three phases-at c. 492 Ma, between c. 365 and 318 Ma, and between 168 and 116 Ma. Correlatives of the Devonian Karamea Suite emplaced between c. 375 and 367 Ma, and the Triassic to Early Jurassic part of the Darran Suite emplaced between c. 230 and 168 Ma, are not present in the area described here.

The QMAP 1:250 000 Geological Map of New Zealand project

“…Allibone & Tulloch 2004;Allibone et al 2009a, b). New Zealand's oldest plutons (latest CambrianÁearliest Ordovician) intrude Takaka Terrane in southern Fiordland (Allibone et al 2009a). …”

“…A distinction was made between 'inboard' plutons, intruding Early Palaeozoic metasedimentary rock, and 'outboard' plutons forming along the suture zone between the Western and Eastern provinces. The suture zone is marked by a major shear zone in places: the Gutter Shear Zone in Stewart Island (Allibone & Tulloch 2008) and the Grebe Mylonite Zone in eastern Fiordland (Allibone et al 2009a). Collectively, the Median Batholith intrudes both Western Province and the Brook Street Terrane of the Eastern Province (Turnbull et al 2010).…”

Petrogenesis and geochemical characterisation of ultramafic cumulate rocks from Hawes Head, Fiordland, New Zealand

“…The western margin of the batholith intrudes Early Palaeozoic metasedimentary rocks with continental affinities (New Zealand Western Province), whereas the eastern margin of the batholith intrudes ensimatic accreted PermianÁJurassic volcano-sedimentary terranes (New Zealand Eastern Province) (Mortimer et al 1999;Allibone et al 2009a). Plutons emplaced prior to c. 128Á125 Ma are characterised by calcalkaline compositions, low Na and Al contents and low Sr/Y values (LOSY), whereas those emplaced after c. 128Á125 Ma are characterised by alkali-calcic compositions, high Na and Al contents and high Sr/Y values (HISY) (Muir et al 1998;Tulloch & Kimbrough 2003;Allibone et al 2009a, b).…”

Carboniferous U–Pb zircon age for S-type Karamea Suite Redjacket Granite, Paparoa Metamorphic Core Complex lower plate, northern Westland

“…Granitoids that make up the Median Batholith and those that intruded the Western Province are subdivided into seven petrogenetic suites, distinguished primarily on the basis of their whole-rock geochemistry and emplacement ages (Tulloch 1983(Tulloch , 1988Cooper & Tulloch 1992;Allibone et al 2009;Tulloch et al 2009). Five of these suites are of mid-Palaeozoic age: Karamea, Paringa, Ridge, Tobin and Foulwind ).…”

“…The basement rocks are subdivided into the Median Batholith and Western and Eastern Provinces, which are further subdivided into several tectonostratigraphic terranes (Landis & Coombs 1967;Coombs et al 1976;Howell 1980;Mortimer et al 1999;Mortimer 2004;Wandres & Bradshaw 2005;Allibone et al 2009). The Western Province terranes comprised the Pacific margin of Gondwana from the Devonian onwards ), while those of the Eastern Province were accreted to the supercontinent margin during the Mesozoic.…”