Renewed brownfields gold exploration in an area situated 20-40 km north and west of the Tarcoola Goldfield, previously held in part by the licensee as EL 1848, was prompted by the May 1995 success of the Samantha/Resolute/Dominion corporate joint...
Renewed brownfields gold exploration in an area situated 20-40 km north and west of the Tarcoola Goldfield, previously held in part by the licensee as EL 1848, was prompted by the May 1995 success of the Samantha/Resolute/Dominion corporate joint venture partners, who had discovered the large Challenger gold deposit at a geologically comparable location approximately 140 km north-west of Tarcoola. Another reason for Grenfell Resources' continuing interest in the Carnding area was to try to find there additional economic gold mineralisation which might supplement the indicated 90,000 ounce gold resource it had delineated at its Perseverance prospect, on EL 1827 near Tarcoola. To mimic the successful exploration methods which had found gold under cover sediments at Challenger, Grenfell Resources undertook a programme of regional and infill calcrete geochemical sampling guided by the reprocessing and interpretation of existing open file SAEI airborne geophysical data. 1120 calcrete samples were collected on 800 m x 800 m centres over the entire licence area, and this coverage was later infilled down to 200 m spaced centres at six prospects, for another 1224 samples. The two most anomalous gold-in-calcrete prospects, Sunshine and Mir, were then flown in April 1997 with a detailed airborne magnetic survey (175 square km coverage at 80 m/40 m north-south flight line spacing and 50 m sensor height). Initial RAB/aircore drilling of geochemical/magnetic targets at these two prospects (72 holes for a total of 1897 m) disclosed only low levels of gold (40 to 390 ppb Au) in the basement rocks. Follow-up RC drilling (27 holes for 2055 m) disclosed only low order gold mineralisation (to 2.22 ppm Au in hole MIRRC03) within fresh Archaean metagranites beneath apparently supergene-enriched calcrete anomalies. Because of the disappointing results from the first phase of its gold exploration programme, and owing to a concentration of effort on other tenements it held in the Tarcoola region, including waiting on the assay results from a collaborative research project on calcrete geochemical sampling that was carried out in concert with PIRSA and AGSO, Grenfell Resources did little field work on the Carnding EL 2030 (renewed on 17/1/2000 as EL 2694) during the period 1998-2000. Also, at the beginning of this time a management decision was made to switch the regional exploration emphasis over to searching for Hiltaba intrusive event magmatic-associated iron oxide copper-gold (IOCG) style mineralisation, rather than just for mesothermal quartz vein-hosted gold lodes of Tarcoola Goldfield type. Two geophysical anomalies with coincident surface geochemical gold and base metal anomalism, named the Soyuz and Fossil prospects, were identified in the western and southern portions of EL 2694, and their IOCG potential became the focus of follow-up geophysics and drilling which commenced in mid-2001. The discovery by Minotaur Exploration of the Prominent Hill copper-gold deposit in November 2001 gave impetus to Gravity Capital's field activities at Carnding, which included the conduct of ground magnetic surveying at the South Mir, Soyuz and Fossil IOCG prospects prior to drilling them (16 RAB/aircore holes for 315 m at Soyuz and South Mir prospects, plus 32.6 m of diamond core tails to 2 holes at South Mir). Trial IP survey profiling plus orientation and detailed soil geochemical sampling (535 samples) was also done at Soyuz and Fossil. A subsequent round of collaborative drilling with PIRSA over magnetic and IP anomalies at Soyuz prospect (4 RAB holes for 105 m), which was targeting possible magnetite / skarn style mineralisation on the margins of late-stage felsic and mafic igneous intrusions, found a significant bedrock copper-gold intercept (3 m @ 0.1% Cu and 10.8 g/t Au from the depth interval 30-33 m in hole SOYUZ06). The mineralisation was seen to occur associated with magnetite in quartz-biotite alteration zones within a granite and its marginal metasediments. Follow-up RC drilling of the discovery at Soyuz (19 holes totalling 646 m) revealed that a copper-gold mineralised halo extends over a width of 200 m adjacent to the northern margin of the granitic intrusion, and that it is occupied by several narrow high grade gold-bearing shoots (e.g. 6 m @ 5.13 g/t Au from the depth interval 14-20 m in hole SOYZRC07, cf. 50 m to the west, an intercept of 47 m @ 0.13 g/t Au extending from 16-63 m depth in hole SOYZRC16). As a result of the company's agreement with BHP Billiton for access to the use of the new "Falcon System" airborne gravity surveying technology, a corporate name change to Gravity Capital was made in late 2001, and existing geophysical targets with inferred IOCG potential in the Tarcoola region were overflown with the Falcon equipment in late 2002. Before this, two detailed ground gravity surveys comprising readings taken at 325 stations had been acquired over the Soyuz and Fossil prospects in early 2002. A consultant was retained during 2003 to review the company's geophysical and drillhole lithology data for the Soyuz and Fossil prospects, and thereby attempt to refine the criteria being used for generating new IOCG targets. In March 2004, the eastern part of EL 2694 was again flown at 250 m north-south line spacing and 80 m flight height with a second Falcon method aerial gravity survey, forming a subset of a 30,000 line km regional coverage obtained by a consortium of several joint venturers. The consultant's findings and the interpretations of the Falcon gravity survey data have not yet been reported by the EL 2694 licensee (now Hiltaba Gold, through a transfer of licence ownership made in June 2004), and so they have not been included as part of the subject data release.
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