Suite subdivision and petrological evolution of granitoids from the Taylor Valley and Ferrar Glacier region, south Victoria Land

Abstract

Detailed geological mapping and geochemical analysis of early Palaeozoic granitoid plutons and dykes from the Taylor Valley and Ferrar Glacier region in south Victoria Land reveal two distinct suites. This suite subdivision-approach is a departure from previous lithology-based schemes and can be applied elsewhere in south Victoria Land. The older calc-alkaline Dry Valleys 1 suite is dominated by the compositionally variable Bonney Pluton, a flow-foliated concordant pluton with an inferred length of over 100 km. Plutons of this suite are elongate in a NW-SE direction and appear to have been subjected to major structural control during their emplacement. The younger alkali-calcic Dry Valleys 2 suite comprises discordant plutons and numerous dyke swarms with complex age relationships. Field characteristics of this suite indicate that it was passively emplaced into fractures at higher levels in the crust than the Dry Valleys 1 suite. Whole-rock geochemistry confirms this suite subdivision based on field relationships and indicates that the two suites were derived from different parent magmas by fractional crystallization. The Dry Valleys 1 suite resembles Cordilleran I-type granitoids and is inferred to be derived from partial melting of the upper mantle and/or lower crust above an ancient subduction zone. The Dry Valleys 2 suite resembles Caledonian I-type granitoids and may have resulted from a later episode of crustal extension.

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

“…The age of the Jaquiery granitoid gneiss is similar to that of the granite Harbour intrusives in Southern Victoria land (Smillie 1992;Allibone et al 1993), although the chemistry of the Jaquiery granitoid gneiss is distinctly different, indicating that they are not direct correlatives. The presence of cambrian-ordovician plutonic rocks in the Takaka Terrane in central Fiordland strengthens previous suggestions, based on the orthogneiss at Kellard point, that at least some intrusive elements of the Ross-delamarian orogeny in East Antarctica and South Australia are present in the New Zealand basement (gibson & ireland 1996).…”

Amalgamation of disparate crustal fragments in the Walcott Bay‐Foster Glacier area, South Victoria Land, Antarctica

“…Dikes of feldspar porphyry intrude subparallel to foliation throughout the Radian sub-block and follow the change in strike at the north end of the block. These dikes are correlated with the DV2 suite of Smillie (1992) New Zealand Journal of Geology and Geophysics, 2001, Vol. 44 The eastern boundary of the Radian sub-block is the ductile Pipecleaner Shear Zone (Findlay et al 1984), which cuts across lithological layering in the south end of the Radian sub-block but which becomes parallel to lithological layering farther north.…”

“…Regionally, the orogen now consists of greenschist to amphibolite facies metasedimentary rocks intruded by granitoid and mafic bodies (as summarised by Stump 1995). Calc-alkaline I-type granites dominate the intrusive suite, and some intrusions are of batholithic scale (Cox 1992;Smillie 1992;Allibone et al 1993a).…”

“…The diopside conglomerate is matrix supported and contains rounded to subrounded sand and cobbles (up to 300 mm) of quartz and quartzofeldspathic Cook (1997), including information from Blank et al (1963), Findlay et al (1984), Aslund (1990), Walcott (1990), Hall (1991), Simpson (1994), andJones (1995). Dikes of the DV2 suite of Smillie (1992) and volumetrically minor granitoid intrusions are not shown. B, Summary geological interpretation of the basement units in the Walcott Glacier region, emphasising the different geology across sub-block boundaries.…”

“…Hall (1991) concluded that they are slightly peraluminous I-type granites. Feldspar porphyry dikes are mainly oriented northeast and are lithologically and geochemically part of the DV2 suite of Smillie (1992) in the Dry Valleys area.…”