Retention Licence 2/2009 (Great Pyramid) is located 12 km southwest of St Helens on the northeast coast of Tasmania. Access to the tenement is via an unsealed track off the Eastern Creek Road, approximately 10 km west of Beaumaris.
The Great Pyramid deposits consists of closely spaced NE trending, cassiterite bearing open fractures hosted by intensely silicified deep water turbidite sediments of the Mathinna Beds. The WNW oriented mineralisation is strongly associated with silicification and intense fracturing, with the main ore block areas having greater than 95 mineralised fractures/metre. No granitic rock crop out on the tenement, although directly northwest Devonian granites believed to be the source of much of the regions mineralisation are exposed.
Exploration & Mining History The Great Pyramid deposit was discovered in 1909 and although the tenement has been explored relatively extensively in the past, only minor production has taken place. The Project area has seen exploration for Sn-Ag-(Cu)-(Pb)-(Zn)-(W) mineralisation since 1908. The key exploration and production activities since this time are summarised below:
- 1909–1910; Great Pyramid Tin Mines conducted the first systematic exploration, including surface channel sampling, pitting and trenching. Five shafts were sunk with grades varying between 0.14% and 6.37% Sn.
- 1925–¬1936; minor mining activities in the high grade zones of Great Pyramid deposit. Records indicate 336t @ 0.88% Sn ore was mined with approximately 3t of contained metal recovered.
- 1965–1983; four different companies and government department (BHP, Aberfoyle Management Pty Ltd, Tasmania Mines Department, and Shell Co. Australia Ltd) had undertaken drilling activities in the area, totalling 8,898 m. The drilling included 158 RAB holes for 5,538m and 26 diamond core holes for 3,359m.
- 1995; Merrywood Coal Company Pty Ltd completed a re-assessment of the deposit.
|Year||Explorer||Number of Holes||Drill Meters|
|1976–1978||Tasmania Mines Department||–||4||13||–||710||710|
Historic Drilling Completed at Great Pyramid (2012 SRK Independent Technical Report)
In 2014 TNT announced an JORC Code (2012) compliant Inferred Mineral Resource estimate at Great Pyramid based on; the 2011 Mineral Resource, the technical review and inclusion of completed “Table 1” information as required by the revised code.
|Sn %Cut off||Tonnes (Mt)||Grade (Sn%)||Contained Tin (Kt)|
Great Pyramid - JORC Code (2012) Inferred Mineral Resources.
With 75% of the drilling to date less than 45m deep and often ending in mineralisation, resource estimates are all within 45m of the surface. Deeper drilling indicates grades below the current extent of the resources. A doubling of the drilled resource depth could potentially lead to a doubling of resource below Pyramid Hill. Drilling indicates the deposits nature and extent are not constrained laterally or vertically with some indications that grade increases with depth. The potential size of the deposit could be significant.
Significant exploration upside exists with targeted drilling below the average depth of the current holes. Diamond drilling identified, but did not properly assess intersections well below the level of the current resource. The potential for additional tonnages and increasing grade with depth should be investigated.