Geology, Genesis, and Exploration Implications of the Footwall and Hanging-Wall Alteration Associated with the Hellyer Volcanic-Hosted Massive Sulfide Deposit, Tasmania, Australia

2001 ◽  
Vol 96 (5) ◽  
pp. 1003-1035 ◽  
Author(s):  
J. B. Gemmell
2004 ◽  
Vol 13 (1-4) ◽  
pp. 25-36 ◽  
Author(s):  
IAN R. MORRISON

Abstract The Izok Zn-Cu-Pb-Ag volcanogenic massive sulfide deposit is located 265 km south of Kugluktuk (Coppermine), Nunavut Territory, Canada, in the west-central Slave structural province. The Izok deposit is owned 100% by Inmet Mining Corporation and represents one of the largest undeveloped zinc-copper resources in North America. The Izok deposit is hosted within and near the top of a thick sequence of predominantly felsic pyroclastic rocks of late Archean age. The hanging-wall stratigraphy includes additional felsic volcaniclastic rocks, andesitic and basaltic flows, thin sulfide-rich iron formations, and turbiditic sedimentary rocks. The felsic volcanic rocks are intruded by intermediate dikes and sills, followed by gabbroic dikes and sills. Both intrusive suites are interpreted to be volcanic feeders to the overlying flows. All lithologies are subsequently cut by younger, irregular, granitic pegmatite and diabase dikes. The volcanic and sedimentary rocks are regionally metamorphosed to pyroxene hornfels grade. The massive sulfides occur within a large (kilometer-scale) Na-depleted sericitic alteration zone. The immediate footwall and hanging-wall rocks to the deposit are characterized by zones of muscovite-biotite-sillimanite, lesser chlorite-biotite-cordierite, and locally intense silicification and sodium metasomatism. All lithologies have been affected by younger Ca-metasomatism. As currently defined, the Izok deposit comprises a cluster of five complexly zoned composite lenses: the Northwest, North, Central West, Central East, and Inukshuk lenses. The first four lenses are amenable to open-pit mining, whereas the Inukshuk lens will require underground development. The total indicated mineral resource presently stands at 16.5 million tonnes with a grade of 2.2% Cu, 11.4% Zn, 1.1% Pb, and 60 g/t Ag. Inmet Mining Corporation is presently reviewing the economic feasibility of developing the property.


2015 ◽  
Vol 3 (3) ◽  
pp. T145-T154 ◽  
Author(s):  
Ernst Schetselaar ◽  
Pejman Shamsipour

We have acquired borehole gravity data along five drillholes intersecting the Lalor volcanogenic massive sulfide deposit hosted in the eastern Flin Flon greenstone belt at Snow Lake, Manitoba, Canada. Inverted apparent interval density (IAID) logs were calculated from the borehole gravity data and compared with lithofacies and [Formula: see text] logs; the latter of which is a geochemical proxy for differentiating volcanic rocks of felsic to mafic composition. The IAID anomalies predominantly reflect alternating mafic and felsic volcanic rock units in the footwall and hanging wall of the massive sulfide deposit. IAID lows are associated with [Formula: see text] highs that correspond to rhyolite and rhyodacite intervals in the hanging wall. IAID lows with associated [Formula: see text] peaks in the footwall occur within intervals of gneiss and schist formed by metamorphism of hydrothermally altered rocks, suggesting that these IAID lows still reflect the felsic composition of their volcanic protoliths. A significant peak-to-peak Bouguer anomaly of 0.66 mGal caused by an estimated excess mass of 0.7 mT can be correlated with gamma-gamma density signature of the main sulfide ore zone in three boreholes. This anomaly is aligned with the ore zone after restoring the displacement along a northeast-dipping structure. When integrated with drillhole lithology and lithogeochemistry logs, gravity borehole data can, in addition to the direct detection of mineralization, be used as a subsurface geological mapping tool.


1998 ◽  
Vol 35 (6) ◽  
pp. 620-636 ◽  
Author(s):  
Pierre Doucet ◽  
Wulf Mueller ◽  
Francis Chartrand

The Coniagas Mine in the northeastern Abitibi greenstone belt is a small, isolated Archean, volcanic-hosted, massive sulfide deposit rich in Zn-Pb-Ag. The Main lens, which is part of four massive sulfide lenses, is restricted to a 40 m thick massive felsic lapilli tuff unit of the 280 m thick sequence. The massive sulfides, a product of subsurface replacement, have features common to both Mattabi- and Noranda-type deposits. The Coniagas Mine sequence represents part of a small subaqueous volcanic edifice that probably evolved close to an arc or back-arc spreading ridge. A distinct alteration halo of chlorite + sericite ± epidote ± spessartine garnet in the immediate footwall and a hanging wall alteration assemblage of quartz + sericite ± epidote ± chlorite characterize the deposit. The sphalerite + pyrite + galena ± chalcopyrite sulfide mineral assemblage in the Main lens differs significantly from the pyrite + chalcopyrite + sphalerite + pyrrhotite ± galena assemblage in the stringer zone. Chlorite compositions are Fe rich close to the mineralized zone, with an Fe/(Fe + Mg) ratio of 0.38-0.48 in the hanging wall and 0.65-0.70 below the ore. Delicate sulfide textures including colloform pyrite and concentric sphalerite are consistent with a low temperature of formation, whereas higher temperatures are inferred for the stockwork zone. Electron probe microanalysis of sphalerite supports inferred hydrothermal fluid temperatures. The low Fe contents (6.7-10.8 mol% FeS) in sphalerite associated with colloform pyrite of the Main lens contrast with the elevated Fe content (12.7-14.1 mol% FeS) in sphalerite from the stockwork.


1984 ◽  
Vol 79 (5) ◽  
pp. 933-946 ◽  
Author(s):  
Bruce E. Nesbitt ◽  
Fred J. Longstaffe ◽  
David R. Shaw ◽  
Karlis Muehlenbachs

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