Beacon Supergroup rocks of probable Devonian age, containing conglomerate clasts of lithologies u... more Beacon Supergroup rocks of probable Devonian age, containing conglomerate clasts of lithologies unknown in outcrop in southern Victoria Land (SVL) occur in the St Johns Range to Bull Pass Region, SVL, Antarctica. The Lower Taylor Group sedimentary rocks, herein called the Sperm Bluff Formation, unconformably rest on the regionally extensive Kukri Erosion Surface that truncates local basement. The basement complex includes three Plutonic Suites, Dry Valley (DV) 1a, DVIb and DV2 of the Granite Harbour Intrusives that intrude metasedimentary rocks of the Koettlitz Group. Allibone et al. (1993b) suggested a SVL terrane accretion event may have occurred about the same time as accretion of a terrane known as the Bowers terrane in northern Victoria Land (NVL) based on changing chemistry of the CambroOrdovician granitoids. Further, it is suggested that conglomerate clasts of the Sperm Bluff Formation may have been derived from this postulated terrane (Allibone et al., 1993b; and Turnbull et...
Analysis of conglomerates and sandstones of the Sperm Bluff Formation at the base of the Taylor G... more Analysis of conglomerates and sandstones of the Sperm Bluff Formation at the base of the Taylor Group (Devonian) between the Mackay Glacier and Bull Pass provides new insights into the nature of initial coarse-grained deposition on basement along the northern side of the McMurdo sedimentary basin. Six lithofacies are recognized in the Sperm Bluff Formation: conglomerate lithofacies, pebbly sandstone lithofacies, cross-bedded sandstone lithofacies, low-angle cross-stratified sandstone lithofacies, bioturbated sandstone lithofacies and interbedded siltstone/sandstone lithofacies. Sedimentary environments ranged from wave-dominated delta, estuary or lagoon to shoreface and inner shelf. The assemblage is thought to reflect changes in sea level. Rhyolite is the most abundant clast type in the coarse lithofacies, but is unknown in outcrop in southern Victoria Land. The rhyolites correlate in age and geochemistry with Cambrian granites in the basement. Coarse beds also contain numerous qua...
Geology of the Tropicana Gold Project , Western Australia
The Tropicana-Havana gold deposit is hosted by Archaean rocks that lie along the eastern margin o... more The Tropicana-Havana gold deposit is hosted by Archaean rocks that lie along the eastern margin of the Yilgarn Craton, Western Australia. The Mineral Resource for the project is 75.3 million tonnes grading 2.07 g/t for 5.01 Moz of gold. Gold mineralisation postdates peak granulite-facies metamorphism and formed from variably oxidised, higher temperature (>350°C), silica-undersaturated fluids. Fluid flow in more competent domains was largely controlled by fracture and grain boundary permeability, and was accompanied by selective sulfide and secondary biotite replacement of metamorphic biotite and amphibole. Partitioning of strain into strongly biotite-sericite-pyrite-altered shear planes, dissolution fractures, and around lithons with jigsaw-fit breccia textures, is evident in domains with higher gold grades. Discrete, laterally continuous high-strain sericitebiotite- chlorite±graphite shear zones that bound ore zones are weakly anomalous in gold. Sulfides within the ore zones are dominated by fine pyrite (2-8%, <0.2mm) with minor chalcopyrite, electrum and telluride minerals. Free gold occurs as fine-grained (10-30 μm) inclusions in pyrite and along biotite-sericite fractures in silicate minerals.
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