This geological model has formed the basis for an initial JORC compliant resource estimation, completed by a consultant geologist experienced in this field using Vulcan 3D software, resulting in a combined measured, indicated and inferred resource of 13.1 million tonnes of 1.48% copper.
The deposit also contains appreciable cobalt, which is not included in the total resource estimate above because limited assays are available for the Inferred Sulphide resource category. However, based on ratios of copper : cobalt in the ore as determined from extensive drilling by Havilah, a cobalt grade of 0.14% is suggested, making Mutooroo one of the highest grade cobalt sulphide deposits in Australia. Apart from the contained 192,000 tonnes of copper and estimated 17,500 tonnes of cobalt, the sulphide ore also has significant gold credits (estimated approximately 92,000 ounces) and sulphur resources (estimated 2.5 million tonnes).
The above resource estimate relies on results from a total of 250 drillholes, including 206 RC and 44 diamond tailed core holes. The database used for the resource calculation includes a total of more than 7,000 assayed samples and over 650 density measurements from core samples. The resource block model is constrained by a wire framed geological interpretation of the sulphide lodes.
The Mutooroo copper-cobalt mineralisation occurs as a series of stacked sulphide rich lodes developed within a 450 west dipping shear zone that is largely confined to an amphibolite sill within Broken Hill age high grade metamorphic rocks.
The orebody shows a distinctive vertical zonation caused by weathering and oxidation :
Completely Oxidised (top 25-35 metres) - to an iron oxide-quartz fragment gossan/ironstone with local malachite - atacamite - chrysocolla - cuprite mineralisation.
Transitional (underlying the above) - a variably developed, secondary, supergene pyrite (after pyrrhotite) -chalcocite - covellite - quartz dominant zone.
Primary Sulphide - pyrrhotite dominant - chalcopyrite - pyrite, disseminated and massive sulphide mineralisation. High grade, primary sulphide milled breccia mineralisation is typically composed of pyrrhotite (60%) - quartz fragments (25%) - pyrite (5%) - chalcopyrite (5%) with local fragments of variably altered country rock.
It is important to note that the feasibility study drilling focussed on comprehensively defining only that part of the resource that was considered directly amenable to open pit mining, based on an open pit shell outlined by earlier scoping studies. There is high potential to convert the deeper inferred resources to indicated/measured resources by infill drilling between the existing, widely spaced mineralised 1960's diamond drill intersections. Thusfar only approximately 700 metres of the more than 2000 metres of strike of the mineralised structure has been drilled to resource status.
The completed geological resource block model forms the basis for detailed mine design work currently being conducted by senior mining engineers. The objective is to generate an optimum open pit mine design using current estimates of capital and operating costs in order to develop an economic model for mining the Mutooroo deposit.
Quite extensive metallurgical test work has been completed on the Mutooroo sulphide ore showing that it can produce a high grade copper concentrate by conventional flotation. However, maximum value can be extracted from the ore by roasting it, thereby liberating both copper and cobalt and utilizing the high sulphur content to produce sulphuric acid. The residue remaining is very pure iron ore.
Two potential development options are presently being investigated by Havilah in order to maximize the value of the Mutooroo deposit:
1. Construct a roaster in South Australia and market the acid locally, to take advantage of the high local demand. Havilah's studies indicate that the cost to build a roaster with a throughput of approximately 500,000 tpa is more than A$300m.
2. Ship the sulphide concentrate to an offshore smelter / roaster. Havilah has employed a consultant to investigate this possibility in China over the last few months, with some positive results. This alternative would result in a lower net return to Havilah, but cash-flow could be achieved earlier and the initial capital cost to build a roaster could be avoided altogether.
For the complete Havilah Resources announcement including figures and tables, please refer to the following link:
About Havilah Resources Ltd
Havilah Resources Ltd (ASX:HAV) is a debt free South Australian gold producer having recently financed and developed its first gold mine at Portia in north-eastern South Australia. It plans to follow on with three copper-gold-cobalt mining developments at North Portia, Kalkaroo and Mutooroo, which are underpinned by a JORC resources mineral inventory of over 1.4 million tonnes of copper, 3.6 million ounces of gold, and 18,000 tonnes of cobalt.
Havilah Resources Ltd