EPM 17216, WESTONIA 4, ANNUAL./FINAL REPORT FOR PERIOD ENDING 28/6/21

URL: https://geoscience.data.qld.gov.au/dataset/cr123409

The project area lies within the Western Succession of the Mount Isa to McArthur River Block mineralised sequence.  The  Mt Isa/McArthur Basin mineralised sequence is one of the world’s major copper, lead, zinc and silver provinces hosting several deposits including the Mt Isa, George‐Fisher, Hilton, Gunpowder, Century, Valhalla (U), Westmoreland (U), Constance Range (Fe) deposits.
The Western Succession copper‐zinc‐lead‐silver deposits make the region one of Australia’s most sought‐after target regions. The currently operating mines to the north and south of the project areas along the same structures confirms this part of the region’s potential to host large deposits.
The Mt Isa Basin consists of a north‐trending belt of Early Proterozoic basement rocks (the Kalkadoon‐Leichhardt Belt) flanked by two belts of Middle Proterozoic rocks, known as the Eastern and Western Successions. The Western Succession is subdivided into the Lawn Hill Platform, Leichardt River Fault Trough, Ewen Block and Myally Shelf. The Eastern Succession is subdivided into the Mary Kathleen, Quamby‐Malbon and Cloncurry‐Selwyn Zones.
Within the Mt Isa Block, four Proterozoic tectono‐stratigraphic terrains are recognized which comprise an older basement core overlain by three younger Proterozoic sedimentary sequences referred to as Cover Sequences 1, 2 and 3. These cover sequences are related to major episodes of intra‐cratonic rift and sag phase sedimentation. The Middle Proterozoic rocks record a complex history of intra‐continental rifting and subsidence during the period 1,800 to 1,590 million years (Ma), followed by compression, basin inversion and regional wrenching during the Isan Orogeny (1,590 to 1,500 Ma).
Within the Western Succession, Cover Sequence 3 east of the Mount Gordon Fault is assigned to the Mt Isa Group (maximum thickness of 4,500 m) within the Leichhardt River Fault Trough. The equivalent sequence to the west of the fault is assigned to the McNamara Group (maximum thickness of 8,500 m) deposited in the Lawn Hill Platform. In the far north of the Mt Isa Block, this rock sequence is termed the Fickling Group.
Cover Sequence 3 hosts many of the significant base metal deposits within the Mount Isa Block, including the Mt Isa, Mount Gordon, Mount Oxide, Hilton and George Fisher base metal deposits within the Mt Isa Group, and the Lady Loretta, Century and Lady Annie deposits within the similar‐aged McNamara Group.
Throughout the Mount Isa Block, copper mineralisation is associated with deformation, especially the reactivation of early‐stage faults during later movement. The faults acted as fluid conduits and depositional sites. In the Western Succession, hydrothermal activity accompanying D2 deformation produced copper (‐cobalt‐gold) deposits surrounded by characteristic zones of silica-dolomite alteration. In the Eastern Succession, granitic intrusions accompanied and followed the D2 event, driving iron, silica and base and precious metal‐rich fluid along reactivated D1 structures. These are preserved as magnetite‐rich ironstones, quartz veins and/or siliceous mylonites containing mineralisation.

Tags: Report
Organization: Geological Survey of Queensland