As part of a regional search for possible major deposits of IOCG type mineralisation, Golden Cross Resources took up six exploration tenements in the northern Gawler Craton that lie to the north and north-east of Coober Pedy, and which are within...
As part of a regional search for possible major deposits of IOCG type mineralisation, Golden Cross Resources took up six exploration tenements in the northern Gawler Craton that lie to the north and north-east of Coober Pedy, and which are within or close to the margins of the G2 continental scale structural corridor. The company then began progressively identifying drill targets based on the intensity of gravity anomalies and the presence of coincident or adjacent magnetic features potentially indicating the presence of large volumes of hematite in major breccia zones hosting chalcopyrite – chalcocite – bornite mineralisation with associated gold, uranium and rare earth minerals. Field work commenced in February 2011 with the acquisition of semi-regional infill gravity coverage on three grids, comprising a total of 510 stations read at 400 m x 800 m spacing. The new gravity data was then merged with the PACE regional dataset and was modelled by Jim Hanneson to identify possible prospective coincident potential field anomalies. 11 such targets were found and ranked for their significance: five were regarded as immediately suitable for drill testing. Two large gravity anomalies were outlined on Oolgelima Hill EL 4427, out of which the favoured SR 11 anomaly (2 mGal Bouguer; 1 mGal residual amplitude) covers an extent of 1.8 km x 1.4 km aligned SW-NE, coinciding closely with a 200 nT magnetic feature. On 31/1/2012, Golden Cross submitted a proposal for PACE 2020 - subsidised partial funding of higher risk exploratory drilling at the Algebullcullia, Mount Euee and Stuart Range IOCG targets on its Coober Pedy Project tenements, and on 3/5/2012 the company received notification of DMITRE's approval of this proposal as PACE Year 7 Drilling Project DPY7-19. Subsequently, during May-June 2013, Golden Cross completed the drilling of 3 vertical rotary mud - precollared diamond core holes with a total penetration of 1412.4 m (including 896.0 m of mostly NQ coring). These drillholes tested three separate basement targets, and were sampled at 1 metre intervals through both the sedimentary cover and the cored bedrock for geochemical analysis. Each hole was progressed for ~250 m into the basement. The basement lithologies encountered by the three holes consist of variably altered gneissic granofels and biotite schists containing numerous quartz-K feldspar pegmatitic zones. Haematitic dusting of K feldspar is common to the basement lithologies in all three holes. No significant IOCG or other types of mineralisation were found, although assaying of the SRE001 drill core returned elevated copper values from the depth interval 164–174 m that peak at 1320 ppm Cu. This result was correlated with observed disseminated pyrite plus trace chalcopyrite and bornite in sericite-chlorite altered metavolcanic rocks. A second zone of elevated copper values occurs from 365-369 m depth, peaking at 1710 ppm Cu. Hole SRE001 is located 25 km north-west of BHP Minerals' historical 1992 percussion drillhole NC9202 put down on EL 1765, in which encouraging base metal and rare earth mineralisation was also encountered. Because of these two holes finding sub-economic mineralisation, it was believed that carrying out additional drilling from sites located ~300 m to the north-east and east of hole SRE001 might provide valuable evidence for vectoring towards an IOCG deposit, because the intense rock alteration seen in that hole's drill core suggests proximity to a major fluid source. A PACE subsidy total amount of $50,000 was awarded to Golden Cross for defraying its 2013 drilling costs, and a Final Report for Project DPY7-19 was submitted to DMITRE on 26/11/2013 (cf. Env 12624). Acting on Jim Hanneson's recommendation, given following his post-drill review and upgraded modelling of the project's gravity and magnetic datasets, detailed infill gravity readings were acquired on five prospect grids during May 2013, when 348 more stations were read at 200 m x 200 m and 100 m x 100 m station spacings. Some of the previously ranked target anomalies were downgraded, but others emerged as of strong interest, including a possible Hillside type IOCG setting at Mungutana East, plus other anomalies at S Dam, Yadmalpi and SR 11 North. Data obtained from the 2013 field work continued to be evaluated throughout 2014, along with office-based activities concerned with resolving the legalities and logistics of gaining land access onto certain parts of the Project licence areas. Jim Hanneson undertook further refinement of his set of anomaly inversion models using the 2013 infill gravity data. In consequence of his modified recommendations, fresh plans were made by Golden Cross for doing follow-up drilling at SR 11 Bore prospect and for new drilling at Oolgelima Hill Central and South prospects. Several companies inspected the licensee's data with the intent of negotiating terms for a possible earn-in joint venture; one company undertook a drill core review at the Mount Barry Station field storage area. During January 2015, a submission for drill project funding under the PACE 2015 programme, of the five preferred targets defined at Oolgelima Hill and Codna Hill, was submitted to DSD for consideration.
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