Granitoids of the Dry Valleys area, southern Victoria Land: Geochemistry and evolution along the early Paleozoic Antarctic Craton margin

Abstract

Field relationships and geochemistry indicate granitoid plutons of the Dry Valleys area comprise at least three petrogenetically distinct suites. The older Dry Valleys 1a (DV1a) suite, comprising the Bonney, Catspaw, Denton, Cavendish, and Wheeler Plutons and hornblende-biotite orthogneisses, and Dry Valleys 1b (DV1b) suite, comprising the Hedley, Valhalla, St Johns, Dun, Calkin, and Suess Plutons, biotite granitoid dikes and biotite orthogneisses, were emplaced before prominent swarms of Vanda mafic and felsic dikes. Both the DV1a and DV1b suites are time transgressive, with older intrusions in each suite being emplaced during the later stages of deformation of the Koettlitz Group. Younger granitoids that postdate the majority of the Vanda dikes include: the Dry Valleys 2 (DV2) suite, comprising the Pearse and Nibelungen Plutons plus several smaller, unnamed plugs; and the Harker, Swinford, Orestes, and Brownworth Plutons with identical field relationships and enclaves but distinct chemistries.Chemical characteristics and limited Rb-Sr isotopic dating indicate plutonism before c. 500 Ma was dominated by the Cordilleran I-type DV1a suite, inferred to have developed during melting above a west-dipping subduction zone along the Antarctic Craton margin. The chemical characteristics of the DV1b suite indicate large-scale melting of a quartzofeldspathic protolith lacking residual plagioclase, but containing refractory garnet. Potential DV1b suite source rocks include metamorphosed immature sediments, possibly underplated along the subduction zone associated with DV1a magmatism, or older granitoid orthogneisses. Major DV1b plutonism at 490 Ma marks the end of subduction-related plutonism in southern Victoria Land. Younger DV2 alkalicalcic, Caledonian I-type plutonism is inferred to have formed in response to uplift and extension between 480 and 455 Ma. G92027 Received 2 June 1992; accepted 29 April 1993Lack of DV2 suite correlatives and Vanda mafic and felsic dikes in northern Victoria Land suggests significantly different tectonomagmatic histories along the early Paleozoic Antarctic Craton margin.

Heavy metal content of meltwaters from the Ross Dependency, Antarctica

“…The proportion of snow lost to meltwater is c. 2-3% (Chinn 1982). The Wright Valley floor in the region of Vanda Station is largely granitic, intruded by lamprophyre dykes (Allibone et al 1993) and is overlain by sandstone, diorite, glacial till, and material which is blown into the valley. Dry Valley soils are characterised by an extremely low organic content and high concentrations of soluble salts (Campbell & Claridge 1987).…”

Contrasting structural styles during polyphase granitoid intrusion, South Victoria Land, Antarctica

“…DVlb plutons are thought to be related to collision and underplating of allochthonous sedimentary material. Radiometric ages for DVla plutons range between 589 and 490 Ma (Allibone et al 1993b), whereas a major pulse of DVlb magmatism at 490-500 Ma is thought to mark the end of subduction-related plutonism (Allibone et al 1993a). Field relationships indicate both suites span at least the later stages of deformation and metamorphism of the Koettlitz Group.…”

“…The granitoid bodies were emplaced at mid-crustal levels above a westward-dipping subduction zone during the Ross Orogeny (Allibone et al 1993a, b). The plutons are variably deformed and are classified into distinct Dry Valley suites (DVla, DVlb, and DV2; Allibone et al 1993a), based on their field relationships and geochemistry. Pluton suites are thought to be emplaced in the following order, DVla, DVlb, and DV2 (Allibone et al 1993b).…”

Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances

“…K and Th data are available for the ADV granitoids [51] and Ferrar dolerites [52] and provide unaltered baseline values for our sediment dataset.…”