QMines Limited is a Queensland-focused copper and gold development Company. The Company owns 100% of the Mt Chalmers (coppergold) and Develin Creek (copper-zinc) deposits, located within 90km of Rockhampton in Queensland.
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Summary:
Local Geology
The informal stratigraphic subdivisions in the mine area are after Large and Both (1980) and were adopted by Taube (1990). The oldest rocks in the area, the 'footwall sequence' of pyritic tuffs, are seen only in the Mt Chalmers open pit and in drill holes away from the mine. The rock is usually a light coloured eutaxitic tuff with coarse fragments, mainly of chert, porphyritic volcanics, and chloritic volcaniclastics. The associated alteration comprising silicification, sericitisation, and pyritisation of this basal unit becomes more intense close to mineralization.
The 'mineralised sequence' overlying the 'footwall sequence' predominantly comprises tuffs, siltstones, and shales and contains stratabound massive sulphide mineralisation and associated exhalites: thin barite beds, chert and occasionally jasper, hematitic shale, and thin layers of bedded disseminated sulphides. Dolomite has been recorded in the mineralised sequence close to massive sulphides. This sequence represents a hiatus in volcanic activity and a period of water-lain sediment and chemical deposition.
Low-grade mineralisation extends several hundred metres beyond the pit in places (Taube 1990).
The rocks in the mine area are gently dipping, about 20° to the north-northeast, in the Main Lode mine area and similarly dipping south for the West Lode. Note that the predominant structure is a broad anticline trending north-north-west. Slaty cleavage is strongly developed in some of the rocks, notably in sediments and along fold axes. Such cleavage is prominent in areas close to the faults but is weak elsewhere.
Detailed work in the open pit has interpreted the doming of the rocks to be close to the mineralisation has seen to be largely due to localised horst block faulting (Taube 1990), but the doming might also be a primary feature in part. Steep dips are localised and usually the result of block faulting. Where the Main and West Lode crop out, they are defined as variably silicified rocks which, by one interpretation, may have been pushed up through overlying rocks in the manner of a Mont Pelée spine (Taube 1990), but in any case, form a dome of rhyolite / high-level intrusions of the Ellrott Rhyolite. The surrounding mineralised horizon is draped upon the flanks of domal structures.
Deposit Type
The Mt Chalmers project is identified as a Volcanic Hosted Massive Sulphide (VHMS) deposit. Mt Chalmers is considered to be a close analogue to the Kuroko VHMS deposits in Japan.
A Kuroko deposit is generally defined as a stratabound polymetallic sulphide-sulphate deposit containing economic to sub-economic Cu-Pb-Zn-AgAu and an abundance of Ba and Ca sulphates. In the Kuroko district, the deposits occur in Miocene rocks and are typically zoned from laminated black Zn-PbAg-Au ores to layered Cu-rich ore to a siliceous stockwork zone at the base. The "classic" Kuroko orebody has six mineralogical zones that are common between deposits (Shimazaki, 1974) and are described below in ascending stratigraphic order:
• Siliceous ore (keiko) - stockwork mineralisation characterised by disseminated and veined pyrite and chalcopyrite distributed within an irregular funnel shape in felsic lavas and pyroclastics;
• Gypsum and/or anhydrite (sekkoko) occur as lenticular or irregular mass between the stockwork and stratiform ore bodies or adjacent to the stratiform ore body;
• In the stratiform ore body, the top half is rich in sphalerite, galena, and barite - black ore (kuroko), while in the lower half is chalcopyrite and pyrite dominate - yellow ore (oko);
• Stratified barite mineralisation overlies the Kuroko zone;
• Small lenses or thin beds of ferruginous chert often occur directly overlying the stratiform ore lens (tetsusekiei bed).
Mt Chalmers and the Japanese Kuroko deposits have many similarities, including alteration mineralogy, with one significant difference being the absence of gypsum beds and the presence of dolomite at Mt Chalmers, and the Kuroko deposits tend to have zoned pipe-like alteration halos (Hunns, 2001).