Amid surging tin prices, emerging Australian tin explorer, Elementos Limited, has identified a new drill target at its 100 per cent owned Cleveland Tin Project in Tasmania following the resumption of exploration activities at the project.
The Cleveland Tin Mine, located approximately 80 kilometres southwest of Burnie, is a historic underground mine that was operated by Aberfoyle Resources from 1968 to 1986.
Elementos now owns 100 per cent of the Cleveland Tin Project following a merger in 2013 with the then unlisted company Rockwell Minerals Limited.
As the tin price jumped to ten‐year highs above US$28,000/tonne in February, Elementos Chairman, Andy Greig, said the company moved quickly to assess the potential for additional tin resources at Cleveland while a major drilling campaign continues at the company’s Oropesa Tin Project in Spain.
“There was a set of historic anomalies to the immediate northeast of the old Cleveland Mine and our existing geological resource which we have been eager to investigate for potential tin mineralisation,” Mr Greig shared.
“The prospective region contains the geological mine sequence and has a strike extent of approximately 500 metres, which is only marginally less than the strike extent of the historical Cleveland ore body. This means that we are targeting an area where the existing Cleveland resource may actually extend to the north.”
Mr Greig said initial reconnaissance geological confirmation mapping and rock chip sampling conducted by the company in February had confirmed the prospectivity of the untested anomalies which were first identified by a Self‐Potential (SP) geophysical survey in 1954.
“Four of the five rock chip samples that were collected contained visible sulphide mineralisation with the most significant assay being 0.7 per cent tin, 0.57 per cent copper, and 13.4 per cent zinc from sample 130403,” he explained.
“The nature of the mineralisation observed during the reconnaissance fieldwork program is similar to that observed during the 2017 Cleveland diamond drilling program which targeted shallow resources above the existing resource, between the known resource and surface.”
“The vein style mineralisation that was observed in 2017 occurs in close proximity vertically and laterally to the semi‐massive sulphide ore at Cleveland,” Mr Greig said.
“A program to drill test the SP anomalies is now being prepared for approval by Mineral Resources Tasmania.”
Overview of the recent exploration program at the Cleveland Tin Project
Reconnaissance geological mapping was conducted to confirm the presence of the geological mine sequence within the untested SP anomalies (Halls Formation and adjacent Crescent Spur Sandstone).
The program also included the collection and assay of rock chip samples from within the untested SP anomalies and reconnaissance of potential access tracks and drill pad sites to drill test the SP anomalies.
Four of the five rock chip samples that were collected contained visible sulphide mineralisation with the most significant assay being 0.7 per cent tin, 0.57 per cent copper and 13.4 per cent zinc from sample 130403.
Exploration Rationale
According to Elementos, a Self Potential (SP) geophysical survey performed by the Bureau of Mineral Resources (BMR or Geoscience Australia) over the Cleveland Mine area in 1954 identified two main areas of anomaly.
The first was drilled and became the Cleveland mine. The second was an area of weaker anomalies to the northeast of the current and historical resources.
The SP survey was carried out before modern underground mining commenced in 1968. Only limited surficial exploration has been carried out over the area identified in the SP survey as being anomalous. No drill testing of the weaker anomalies has been carried out.
The SP technique is one of the earliest developed geophysical methods employed commercially for detecting massive sulphides beneath the surface. The Cleveland ore body is a ‘semi‐massive sulphide’ ore body containing tin as cassiterite. An SP anomaly is the detection at the surface of natural potentials resulting from electrochemical reactions beneath the surface. No electric current is introduced in the method. Semi‐massive to massive sulphide ore bodies have been detected by the electrochemical reactions that occur due to oxidation of the ore bodies through interaction with groundwater.
The amplitude of the SP anomaly detected in 1954 by the BMR rapidly decreases with increasing depth from surface to the top of the historical ore body (and current open-pit resource). Elementos outlines that the amplitude of the untested SP anomalies to the northeast of Cleveland suggests the possibility that sulphide mineralisation may occur at depth in the area.
