Eastern Eyre Project: IOCG
The Eastern Eyre Project comprises five properties on the southern portion of the Olympic Dam copper belt. The project area is located near the industrial town of Whyalla.
Figure 1. Eastern Eyre Project
• Overview. Renascor’s exploration activities at Eastern Eyre are focused on the drilling of high priority targets for large-scale resources in the southern portion of South Australia’s Olympic Dam iron-oxide, copper-gold (IOCG) belt. (See Figure 1) Recent drilling has resulted in a material upgrading of the Extension Tank prospect, where drill results suggested the potential for a large scale IOCG deposit, based on the presence of hematite alteration, anomalous copper and a high amplitude (6 MGal) gravity anomaly.
• Extension Tank. Extension Tank is defined by a discreet, high amplitude (6 MGal) gravity anomaly within the highly prospective Roopena fault zone. Renascor considers the Roopena fault, as well as the parallel Angle Dam fault, to be a major conduit for mineralisation sourced from nearby Hiltaba-age granites. These granites are associated with mineralisation at the major deposits (e.g., Olympic Dam and Prominent Hill) within the Olympic Dam IOCG belt. Previous drilling within the fault corridor at the Spencer prospect has included intersections of extensive IOCG-alteration with elevated copper, as well as higher concentrations of copper (including ore-grade massive sulphides) at the 1050 East prospect within the parallel Angle Dam trend. See Figure 2. As a result of the density of the gravity anomaly and its discreet location within the Roopena fault structure, Renascor considers Extension Tank a high priority target for large scale IOCG-style mineralisation.
Recent drilling at Extension Tank has confirmed possible IOCG development within the interpreted high-density zones of the gravity anomaly. Prior to Renascor’s recent drilling, the interpreted gravity anomaly had not been adequately drill-tested, with limited shallow drilling over the southern and western portions not explaining the gravity anomaly. Renascor recently completed two reverse circulation holes at Extension Tank, targeting the most central of three interpreted high-density source regions for the observed gravity anomaly. See Figure 3. Hole 14RETRC001 was drilled to 198 metres to test the eastern portion of the central gravity zone and intersected strongly anomalous copper sulphide mineralisation, including chalcopyrite, with results including 8 metres at 0.45% copper from 64 metres. (Drill results are included in Renascor’s ASX released dated 28 January 2014). Mineralisation is associated with fine crystalline hematite within a brecciated metabasalt. See Figure 4. Renascor considers the presence of significant copper mineralisation, together with fine hematitic alteration and specularite veining, to suggest the underlying gravity feature offers ample potential for locating a copper-rich IOCG system.
Hole 14RETRC002, located 300 meters to the north of hole 14RETRC001, was completed to 162 metres to test for continuation of the interpreted density target zone intersected in hole 14RETRC001. Hole 14RETRC002 intersected 42 metres of intermittent hematite alteration from 120 metres to end-of-hole, with intermittent intervals of minor, fine-grained copper sulphide mineralisation. The level of alteration appears to be increasing towards the end-of-hole, however, ground conditions prevented the continuation of drilling in the current program. Similar to Renascor’s first hole at Extension Tank, the results from hole 14RETRC002, in particular the strong hematic development, suggests the large gravity feature may represent a large-scale IOCG system. Renascor’s most recent drilling has provided new data on the lithologies and copper mineralisation proximate to the Extension Tank gravity feature. Although both holes intersected moderately dense lithologies, Renascor believes that the core density zones have not been tested with the current depth of drilling. Further processing of the existing gravity data also suggests that the main density zones lie in east-west oriented structures, rather than the initial north-south interpretation, and this possibility will be incorporated into future work programs.
As shown in Figure 5 Renascor’s interpretation of the gravity anomaly suggests that the recently drilled holes have tested only the upper portion of the high-density target zones, offering ample opportunity to locate hematite-rich mineralisation in next-stage drill testing. The prospects for locating a large scale, IOCG-style deposit proximate to these high-density zones are further enhanced from the recent drilling, which has demonstrated the widespread presence of late-stage, hydrothermal copper mineralisation associated with pervasive hematite alteration and veining. Renascor considers these features, proximate to a discreet, high amplitude gravity anomaly, to be relatively unique within the Olympic Dam domain and suggestive of the presence of a possible copper-rich IOCG system.
• Regional Example. Renascor believes that these initial drilling results at Extension Tank share important similarities to the early drilling results at a number of hematite dominant IOCG deposits within the Olympic Dam IOCG domain. For instance, Oz Minerals (ASX: OZL) has defined an inferred resource of 202Mt @ 0.6% copper at its Khamsin IOCG prospect, located approximately 150 kilometres north of Extension Tank. Initial drilling at Khamsin focused on the high-density portions of a discreet gravity anomaly. See Figure 6. Similar to Renascor’s initial drilling at Extension Tank, the initial drilling of the peak of the gravity high at Khamsin intersected strong indications of a potential larger IOCG-system (hematite and chlorite altered granite with low level (>0.2%) copper), and this led to the discovery of a large-scale copper resource within the broader gravity anomaly. Renascor is similarly encouraged by the initial indications of a possible IOCG system with the Extension Tank gravity anomaly and the prospects for discovering a similar hematite-rich IOCG copper resource through follow-up drilling.
As a result of the drilling at Extension Tank, Renascor re-interpreted historical induced polarisation (IP) data completed over the gravity anomaly to show the IP target was not adequately tested and is thus a high priority target. In the early 1990s, Western Mining Corporation Ltd (WMC) undertook IP surveys, defining a broad chargeability anomaly on the western side of the gravity feature. WMC undertook shallow drilling up to approximately 60 metres, targeting the chargeability zone. See Figure 3 and See Figure 4. Renascor’s recent drilling suggests that this drilling did not reach fresh, un-weathered basement rocks, and therefore did not provide an adequate test for the development of possible copper sulphide mineralisation within the chargeability anomaly. In addition to drill-testing the high-density zone defined from the gravity data, Renascor considers the chargeability zone to represent a prime target for locating a large-scale IOCG-style deposit. Renascor is also considering additional surveying using modern IP equipment for the entire area of the gravity anomaly.
• Prospects along-strike. In addition to the Extension Tank prospect, Renascor considers the wider Roopena-Angle Dam fault structure to offer highly prospective and untested targets for large-scale copper mineralisation. The recent results at Extension Tank, as well as the discovery of high-grade copper at 1050 East, has highlighted the significance of the Roopena-Angle Dam fault, which extends through the project area for approximately 40 kilometers, as a potential transport system and host for extensive copper mineralisation. Significantly, only limited exploration has been conducted along this trend. In addition to conducting follow-up drilling at Extension Tank, Renascor intends to expand its exploration activities to include untested and similarly prospective copper prospects within this and other fault-controlled systems within the tenement package. See Figure 7.
•Next steps. Renascor expects follow-up drilling at Extension Tank to focus on drill-ready targets within the untested high-density zone and over the recently defined chargeability anomaly. Additional exploration work is expected to include additional geophysical surveys, including more detailed gravity and IP, and drill-testing of additional fault-related gravity targets within the project area