University of Tasmania
whole_DavidsonGarryJames1991_thesis.pdf (40.51 MB)

Starra and trough tank : iron-formation-hosted gold-copper deposits of North-West Queensland, Australia

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posted on 2023-05-26, 23:45 authored by Davidson, GJ
Starra and Trough Tank are stratabound Cu-Au deposits hosted by stratiform magnetite-hematite iron formation in the Mount Isa Eastern Succession, Australia. They are part of the rift-related Middle Proterozoic Mary Kathleen Group, deposited in a shallow to evaporitic setting, and subsequently deformed and metamorphosed. The location of Starra (consisting of 4 geographically separate orebodies), on the margin of a major Greenschist facies shear zone (ore metamorphism estimated at 500 - 550° C, 3.5 - 4.5 kbar) has led to a more complex structural history than that experienced by surrounding rocks. Both structural/metamorphic and syngenetic ore genesis models have been proposed for the ores. Trough Tank is far less stained, but was metamorphosed to upper Amphibolite grade (680 - 720° C, -4 kbar). Structural events in the Starra region are identified as (1) Starra Shear development during D1a extension, (2) peak-metamorphic D2(Main Phase) deformation, producing upright, north-trending, isoclinal folds, (3) retrogressional left lateral strikeslip on the Starra Shear, producing adjacent steeply-plunging medium-scale folds (D2(Late Phase)), (4) D3 northwest-trending fold and kink domains, and (5) D4 reverse movement on the Starra Shear and nearby Mount Dore Fault Zone. A new stratigraphic sub-division for the base of the Staveley Formation is proposed. Lowermost is the Harley Member, a strongly deformed chloritic unit with a tholeiitic tuff component. This is conformably overlain by the low-Nb-Zr-Y felsic Mariposa Creek Member, in turn conformably overlain by the Starra Iron-formation Member, and undifferentiated calcareous metasediments. To the south and east, the mineralised horizon strike-equivalents are massive hematitic ironstones, conglomerate-bearing ironstone, Hamersley-style banded iron formations (BLFs), and tourmalinites, all intercalated with shallow marine and fluvial-marine sediments. The local ore environment is interpreted as a deeper section of the basin.


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Copyright 1989 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (PhD)--University of Tasmania, 1991. Includes bibliographical references. Folded map in pocket at back of vol

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