First Tin Plc (First Tin) owns the Taronga Tin Project through its 100% owned Australian unlisted public company subsidiary First Tin Australia Pty Ltd which holds 100% of Australian unlisted company Taronga Mines Pty Ltd (TMPL). The mineral rights for the project are held by TMPL.
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Summary:
The Taronga tin deposit is located within the New England orogen in northeastern NSW. This orogen is the most easterly and youngest orogen of the Tasmanides system, which formed the south-eastern margin of the Gondwana supercontinent. It was an active westward dipping subduction zone active from the Silurian to Carboniferous periods. During the Permian, eastern rollback of the plate margin resulted in extension and formation of small rift basins.
Following cessation of subduction, large volumes of I- and A- type granites were intruded into the former accretionary complex rocks during the middle Permian to Triassic. These represent the roots of a new continental margin arc and are the last remnants of an active arc margin on the Australian continent. These granites are the source of the mineralising fluids responsible for depositing the tin mineralisation at Taronga.
The Taronga deposit is hosted by metasediments of the Permian aged Bondonga Beds that have been partially converted to hornfels due to the contact metamorphic effects of the intrusion of the Triassic aged Mole Leucogranite. The Mole Leucogranite is a reduced, I-Type, highly fractionated, multiple intrusion and is interpreted as being the source for the magmatic fluids responsible for most of the mineralisation in the district.
Granite, interpreted to be an apophysis of the Mole Leucogranite, has been intersected by drilling at depth beneath the Taronga deposit, and several non-outcropping ridges of granite, generally trending in a northeasterly direction, are interpreted as underlying most of the known tin mineralisation in the district.
Tin mineralisation in the district comprises:
1. Sub-vertical sheeted quartz-mica-sulphide-cassiterite+/-topaz-fluorite veins (sheeted veins).
2. Greisens at the apices of granite intrusions.
3. Quartz-mica greisen lodes and veins, generally sub-vertical.
4. Eluvial or weathered bedrock deposits.
5. Alluvial or placer deposits.
6. Palaeo-alluvial deposits or "deep leads".
The Taronga tin deposit is a sheeted vein style +/- copper-silver with horizontally and vertically extensive veins of quartz-mica-cassiterite-sulphide +/- fluorite-topaz occurring over a combined area of up to 2,700m by 270m.
The Taronga deposit consists of a series of sub-vertical sheeted quartz-mica-sulphide-cassiterite+/- topaz-fluorite veins that vary from 0.1mm to 100mm (dominantly 1-10mm) in width and have an average density of 5 to >20 veins per metre.
Tin occurs dominantly (>90%) as relatively coarse cassiterite (SnO2) that averages 0.3-3mm in size. The cassiterite is mainly hosted within the veins, with volumetrically insignificant, very fine grained cassiterite sometimes found in haloes to the veins.
The veins tend to occur in sets, with four main zones identified as Hillside, Hillside Extended, Payback and Payback Extended. The four zones appear to coalesce into a single zone in the northeast (North Pit) area.
Oxidation is very limited, with relatively fresh rock occurring almost at surface. Deeper weathering can be seen along some of the vein sets, which appear to have been preferentially weathered.
The general structural trend is ENE, parallel to the mineralised veins. Two subsidiary structural trends are observed, one at approximately 90° to the main vein trend and sub-vertical, the other sub-horizontal and probably related to cooling and contraction of the underlying granite.
A basalt layer forms a sinusoidal zone that separates the North Pit and South Pit areas and may have been a less favourable rheological setting for the mineralisation. Slightly different elemental distribution is noted on either side of the basalt, representing different stratigraphic or litho-structural associations.
The mineralisation comprises North Pit and South Pit zones with a relatively lower grade zone in between. This lower grade zone is partly the result of a lack of drilling and a change in the host lithology with possibly a change in the rheological properties of the host.
The North Pit comprises two higher grade elongate tin zones with an enveloping zone of lower grade tin mineralisation forming a single mass. Whilst the South Pit comprises up to five distinct and well separated elongate tin-enriched zones with parallel strike and dip.
Dimensions
The Mineral Resources have a strike length of around 2.7km in a north easterly (grid north) direction. The plan width of the resource varies from 200m to 400m with an average of around 270m. The upper limit of the mineralisation is exposed with the fresh rock generally occurring around 20m below surface and the lower limit of the Mineral Resources extends to an approximate depth of 550m below surface (400mRL).
The lower limit to the Mineral Resource is a direct function of the depth limitations to the drilling in conjunction with the search parameters. The mineralisation is open at depth and laterally to the southwest, beyond the South Pit zone.