Introduction

The Mount Garnet Tin project is located near Mount Garnet in north Queensland. The most advanced deposits of Gillian and Pinnacles are located within nine kilometres of the CSD owned base metals processing plant.  National Highway One (Kennedy Highway) runs through the project area.

The Herberton-Mount Garnet tin field has been a significant tin producer with an estimated production of 85,000 tonnes of tin metal in concentrate up until 1985. CSD holds a large area of tenements within the southern historic Herberton tin field covering numerous tin deposits and prospective tin bearing ground. CSD holds four deposits with defined tin resources – Gillian, Pinnacles, Windermere and Deadman’s Gully.

In addition to tin, CSD’s deposits at Mount Garnet also contain significant concentrations of iron and one deposit, Pinnacles, also contains significant concentrations of fluorine. CSD includes iron in its Mineral Resource statements for its Mount Garnet tin deposits and fluorine for its Pinnacle deposit.

The Pinnacles deposit was investigated by Comalco in the 1970s as a potential source of fluorine in the form of the mineral fluorite. (Among other uses, Fluorine is used as a flux in aluminium smelting, which was Comalco’s interest).

Mount Garnet Tin Project – Location Plan

Mount Garnet Tin Mining and Exploration History

The Mount Garnet tin deposits occur in the southern part of the Herberton tin field where tin mining dates back to the 1880s. Production from the Herberton tin field has come from alluvial and hard rock mines with two thirds of production from hard rock.

The hard rock deposits were principally quartz lodes but tin also occurs in greisens and skarns. At Mount Garnet, tin occurs in magnetite skarns, some of which also contain fluorite.

CSD has been exploring and evaluating the tin deposits at Mount Garnet since the Company was formed in 2007.

Prior to CSD’s involvement, the area was explored by many others including Renison Limited, Commonwealth Aluminium Corporation Limited (Comalco), Otter Exploration NL (Otter), and Western Mining. Notable discoveries during this time were the Gillian tin skarn discovered by Renison Limited, the Pinnacles tin-fluorite skarn discovered by Comalco, the Windermere tin skarn by Otter, and the Sailor Valley anomaly identified by Western Mining.

An estimate of CSD’s Mineral Resources for tin at Mount Garnet was made by Optiro Pty Ltd (Optiro) and announced in June 2013.

CSD reported the results of a Pre-Feasibility Study for the Mount Garnet tin project in September 2013.

An updated estimate of CSD’s Mineral Resources for tin in the Gillian deposit at Mount Garnet was made by Optiro in 2014 and announced in June 2014.

CSD reported the practical completion of a Definitive Feasibility Study for the Gillian deposit at Mount Garnet in December 2015.

Mt Garnet Tin Project Geology

Mt Garnet Regional Geology

The Mount Garnet tin deposits are hosted in granite-intruded sediments with associated contact metamorphism and metasomatism, see below.

The mineralisation including cassiterite, magnetite and fluorite, is contained within tabular skarn lenses that formed within carbonate-rich sediments.

The Silurian Chillagoe Formation, characterised by limestone – marble, chert, basic volcanics and siliciclastics, lies along the western margin of the Hodgkinson Province. Limestones of this formation are favourable hosts for skarn-associated tin mineralisation at Mount Garnet.

Mount Garnet Project – Regional Geology Map

 

Gillian Geology

The Gillian tin deposit occurs as skarn lenses developed in altered limestone beds of the Chillagoe Formation which has been intruded by granites. The lenses are tin-iron skarns consisting of massive magnetite and goethite with fine grained cassiterite, the most common tin bearing mineral.

The deposit strikes north-south and has the dimensions 850 m north-south, 880 m east-west and 250 m vertically. In the western part of the deposit, mineralisation occurs as a number of steeply ipping tabular lenses, while mineralisation in the eastern part occurs, primarily, as a single lens.

Gillian Tin Deposit – Regional Geology and Drill Coverage

 

Pinnacles Geology

The Pinnacles tin deposit occurs as a series of irregular skarn lenses developed in altered limestone beds of the Chillagoe Formation which has been intruded by granites. The deposit is a tin-fluorine-iron skarn consisting of thinly banded magnetite-fluorite, known as wrigglite, with fine grained cassiterite, the most common tin bearing mineral.

The deposit strikes north-south and has the dimensions 700m north-south, 500m east-west and 250m vertically. In the western part of the deposit, mineralisation occurs as a number of steeply dipping tabular lenses, while mineralisation in the eastern part occurs, primarily, as a single lens, see below.

The flat lying skarn occurs close to the surface and dips towards the centre of the deposit where it is up to 25m thick.

Pinnacles Tin Deposit – Regional Geology and Drill Coverage

 

Windermere and Deadman’s Gully Geology

The Windermere tin deposit occurs as an irregular skarns pods developed in altered limestone beds of the Chillagoe Formation which has been intruded by granites. The deposit is a tin-iron skarn consisting of massive magnetite with fine grained cassiterite, the most common tin bearing mineral.

The Windermere deposit consists of a series of several, more or less vertically dipping, skarn pods striking more or less north-south. The deposit is known over a strike length of two kilometres. Drilling of the deposit has revealed that the mineralisation exists as ‘pods’ of various sizes. The larger intercepts seem not to extend along strike or down dip. The deposit does not seem to contain a clear contact zone of skarn formation resulting in the ‘pods’ referred to above. This makes it difficult to define a clear target across the 2 km strike length. A theory that the granite contact is deep (<150 m) and that the mineralising fluids have permeated through the host rocks to form the skarn pods has not been proven to date.

The geology of the Deadman’s Gully deposit, which lies on the same trend as Windermere about 750 m to the south, is similar to that of Windermere. Deadman’s Gully is smaller, being known over a strike length of about 100 m. The local geology is depicted below.

Windermere and Deadman’s Gully Tin Deposit – Regional Geology and Drill Coverage

Mt Garnet Tin Project Mineral Resources

Gillian Mineral Resource

The Gillian Mineral Resource estimate was reported in 2014 in accordance with the JORC Code 2012. The Mineral Resource estimate for the Gillian deposit is summarised below.

The Mineral Resource was estimated by Optiro Pty Ltd in 2014.

A total of 280 drill holes, 233 reverse circulation drilling and 47 diamond core, were used for the estimate.

The drill holes were geologically logged for key geology and mineralisation domains and either splits from 1 m sample lengths for the reverse circulation samples or half core sampled, typically in 1 m lengths. Samples were analysed for tin and iron using a fused bead XRF method.

Optiro consultants estimated the Mineral Resource using ordinary kriging to estimate Sn and Fe grades. Top-cutting of Sn sample outliers was applied where required. Density was estimated from Sn and Fe grades using regression formulas. A dataset of 1,936 density measurements was used to create the regression formulas.

The sampling and assaying methods and the grade estimation method used were appropriate for the Gillian style of mineralisation.

Gillian Deposit Mineral Resources as at 25 June 2014.

1Mineral Resources are reported above a 0.2% Sn cut-off grade

Pinnacles Deposit Mineral Resource

The Pinnacles Mineral Resource estimate was reported in 2013 in accordance with the JORC Code 2012. The Mineral Resource estimate for the Pinnacles deposit is summarised below.

The Mineral Resource was estimated by Optiro Pty Ltd in 2013.

A total of 240 drill holes, 228 reverse circulation drilling and 12 diamond core, were used for the estimate.

The drill holes were geologically logged for key geology and mineralisation domains and either splits from 1 m sample lengths for the reverse circulation samples or half core sampled, typically in 1 m lengths. Samples were analysed for tin and iron using a fused bead XRF determination, or sodium peroxide fusion with ICP-MS determination. Samples were analysed for fluorine using fused bead with XRF determination, or carbonate fusion with ISE determination.

Optiro consultants estimated the Mineral Resources using ordinary kriging to estimate Sn, Fe and F grades. Top-cutting of sample outliers was applied where required.

Density was estimated from Fe grade using regression formula.

The sampling and assaying methods and the grade estimation method used were appropriate for the Pinnacles style of mineralisation.

Pinnacles Deposit Mineral Resource Estimate as at June 2013

1 Mineral Resources are reported above a 0.2% Sn cut-off grade

Windermere and Deadman’s Gully Mineral Resources

The Windermere and Deadman’s Gully Mineral Resource estimate was reported in 2013 in accordance with the JORC Code 2012. The Mineral Resource estimate for the deposits is summarised below.

The Mineral Resource was estimated by Optiro Pty Ltd in 2013.

For Windermere, a total of 97 drill holes, 96 reverse circulation drilling and one diamond core, were used for the estimate.

For Deadman’s Gully, a total of 21 drill holes, 20 reverse circulation drilling and one diamond core, were used for the estimate.

The drill holes were geologically logged for key geology and mineralisation domains and either splits from 1 m sample lengths for the reverse circulation samples or half core sampled, typically in 1 m lengths. Samples were analysed for tin and iron using a fused bead XRF determination, or sodium peroxide fusion with ICP-MS determination.

Optiro consultants estimated the Mineral Resources using ordinary kriging to estimate Sn and Fe grades. Top-cutting of sample outliers was applied where required.

The sampling and assaying methods and the grade estimation method used were appropriate for the Windermere-Deadman’s Gully style of mineralisation.

Winderemere-Deadmans Gully Mineral Resource estimate as at June 2013

1 Mineral Resources are reported above a 0.2% Sn cut-off grade