Mt. Isa Mine

The Mt. Isa Mine is a deposit of copper, lead and zinc. It is located at latitude 20∘44’S, longitude 139∘29’E and is in Queensland (Forrestal, 1990). Generally, this ore deposit contained 123 g/t copper, 5.0% lead and 7.0% zinc at 4.8 Mt. The host rock of this deposit consists of pyritic shale, carbonaceous shale, dolomitic siltstone, carbonate, granite, ironstone and metasedimentary cover rocks (Hutton et al. 2012).

Deposit genesis

The ore deposit genesis is considered to have occurred in the Urquhart Shale, deep water and black shale environment, shallow water and hypersaline environment (Forrestal, 1990). In the Urquhart Shale, hydrothermal alteration had taken place in which the selected beds were changed to pyrite, galena and sphalerite.
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Isa deposit occurred in an intracontinental rift to passive margin environment with complicated history (Hutton et al. 2012). This rift environment produced the fluid source and fluid pathways. There are also orebodies deposition which occurred due to sedimentation but it appeared late in extensional cycle. It is found that the age of mineralization of Mt. Isa is approximately 1870 million years old (Forrestal, 1990). During that period, the oldest and nominated basement was disfigured and metamorphosed. Besides, the continental margin was carrying out evolution to palaeo-Australian plate. In this process, the margin experienced a couple of divergent and convergent states. Mt. Isa is one of the sequences of the Middle Proterozoic cover in the Western Fold Belt. This sequence consists of sandstones, volcanic and calcareous sedimentary rocks. It is also known that the central Kalkadoon-Leichhardt Belt split up the Western and Eastern fold belts. Furthermore, the region of Mt. Isa is part of Leichhardt River Fault Trough. Therefore, from the Western part of the Lawn Hill Platform to the Eastern part of the Kalkadoon-Leichhardt Belt, there is a belt of folding and faulting, and plenty of metamorphosed rocks can be found …show more content…
Isa orebody. When the oxidation was completed, the depth of the oxidized zone was around 50m from the ground surface (Forrestal, 1990). Cerussite was found as the dominant mineral while zinc was mostly exhausted. The orebodies’ bedded nature remained the same within the oxidized zone but the rocks are filtrated outside the oxidized zone. In addition, this oxidized ore were generally used for ancient production of mining a long time ago. But nowadays, this oxidized ore would only be used for smelter flux.

Exploration indicators

Mount Isa Mines Limited was the exploration indicator for Mt. Isa area (Forrestal, 1990). Since 1927, the sulphide ore was explorated systematically by diamond drilling. Around 11000m of core was drilled from surface sites. Black Star was the main target to be drilled in smaller and higher grade lenses. In 1941, Racecourse orebodies, which were narrow but in large scale, were begun drilling. During mid-1950s and late 1960s, there were even more major drilling which gave extra ore reserves in the Black Star and Racecourse

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