[ Note - here is Part 1 of the abstract relating to 2 separately indexed parts ]. As an adjunct to its widespread search for possible diamondiferous kimberlite diatremes on its Abminga Project acreage situated nearby to the north-west, Caldera...
[ Note - here is Part 1 of the abstract relating to 2 separately indexed parts ]. As an adjunct to its widespread search for possible diamondiferous kimberlite diatremes on its Abminga Project acreage situated nearby to the north-west, Caldera Resources took up the two subject licences in the vicinity of Oodnadatta to explore there for diamonds as well as for any economic base and precious metal mineralisation that could be associated with iron metasomatism inferred to have occurred in buried Proterozoic basement rocks. To begin the exploration, a semi-regional aeromagnetic survey was flown by Geoterrex across the Oodnadatta district in conjunction with Mines and Energy South Australia's regional SAEI - funded aeromagnetic programme [Survey Areas D3 and E3], collecting infill magnetic data for Laura Holdings on 400 m spaced flight traverses. From inspection of the resulting stacked magnetic profiles, 12 prospective magnetic anomalies were identified, six being present on each of the two licence areas. None of the anomalies appeared to have characteristics consistent with buried kimberlite pipes, but were thought to have good potential for indicating possible gold-base metal mineralisation within shallow basement. In late 1995, Western Mining Corp. entered into a farmin option agreement with Caldera Resources, for which during early December it carried out a 236 station regional gravity survey on a 1 km x 1 km grid over the eastern part of EL 2064, that was later infilled to 500 m station spacing. The survey outlined a ~16 mGal gravity anomaly that coincided with the main, 250 nT aeromagnetic anomaly. The sources of these anomalies, as inferred from modelling studies, were considered to be several bodies representing variably uplifted fault blocks distributed over a 7 km x 3 km area. The interpreted depths to the tops of the basement blocks ranged between 180 and 970 m. Overall, the feature was believed to have good similarities with the geophysical anomalies present at Olympic Dam, where a 14 mGal gravity and 1000 nT magnetic anomaly pair occur in a comparable structural setting. During the second licence year the only field activity was some limited gravity surveying over aeromagnetic anomalies #1 and #4 on EL 2065, and modelling of that gravity data. This modelling suggested that the sources for the gravity anomalies lie closer to the surface than do the modelled sources for the magnetic anomalies. Attempts were made to farm out the licences, and discussions took place with various parties. To assist with drill target definition, further detailed ground magnetic and gravity surveys totalling 347.7 line km and 2053 stations respectively were acquired by Scintrex for Laura Holdings over ten target anomalies during 1997. This work confirmed the validity of the original aeromagnetic data interpretation, and showed that some gravity anomalies are slightly displaced away from the centres of associated magnetic highs, which is a feature often observed at IOCG deposits. In May 1998, a reconnaissance regolith sampling programme was carried out over some of the most prominent magnetic anomalies, to test for any geochemical response to possible underlying mineralisation. Various statistical treatments of the soil and float rock chip assay results were performed in an attempt to identify anomalous values. None were forthcoming, and it was concluded that the local Mesozoic sedimentary cover was probably too thick to allow basement geochemical leakage signatures to reach the surface. Next there occurred considerable delays in obtaining Native Title land claimant agreements and site clearances which would allow drilling work to progress. In the meantime, the licensees signed an option agreement with international explorer Inco Resources in October 2001, whereby that company could earn up to 50% interest in the tenement (now EL 2736) by spending $1 million on approved drilling works. A transfer of a 10% licence part interest to Inco co-venturer Platsearch NL was also approved with effect from 24/4/2002, on the condition that drilling would proceed within twelve months. After Part 9B negotiations and Aboriginal Heritage site clearances were completed in May 2002 and legal agreements made for the commencement of drilling, Inco chose to drill first at a location on Crown Land (the Oodnadatta Common) approximately 12 km west-northwest of Oodnadatta township. A single vertical, rotary precollared, HQ/NQ diamond drillhole was begun on 16/7/2002, and eventually was completed at a total depth of 624.6 m on 20/8/2002, after earlier drilling difficulties were encountered within the basal Algebuckina Sandstone when a 100 mm rotary core barrel became stuck downhole at 305 m depth, following a section of very slow roller bit penetration below 280 m depth. The resumed washover HQ diamond cored drillhole entered Neoproterozoic basement (Adelaidean metasediments) at 319 m depth, intersecting a sequence of quartzites, shales and dolomitic carbonate rocks. Zones of brecciation and quartz-carbonate veining were observed in drill cores recovered over part of this sequence. At 569.6 m depth the hole entered Palaeoproterozoic basement, encountering banded quartz/feldspar/chlorite/haematite gneiss and lesser pegmatite which continued to the end of the hole. Chemical analyses of basement drill core samples yielded no anomalous metal values, although a sampled 1 m section of the veined Adelaidean returned 579 ppm Cu and 492 ppm Zn. Petrological examinations made on selected drill core samples showed middle to upper amphibolite metasedimentary facies assemblages that resemble those of rocks of the Olary and Broken Hill domains in the Curnamona Province. The unsucessful drillhole was later converted to an artesian water bore ('Kelpie' bore) by the owners of Todmorden Station, with the intent of pumping groundwater from it for distant use by the station, besides also making the water available for onsite use by the Dunjibar Aboriginal Community. Despite the drilling of CAR1 not having explained the causes of the targeted geophysical anomalies, on 3/3/2003 Inco decided to withdraw from the Mount Carulina option agreement, and under the terms of the Platsearch joint venture, because that latter company could not fund further drilling itself or find a replacement JV partner within the following twelve months, it too was obliged to terminate its involvement in the exploration, with no retained interest. No further field work took place on the subject licence during the next four years, although plans were made to conduct more ground geophysical traverses and then to RC drill five discrete magnetic anomalies of moderate strength and size which were estimated to have sources lying at 150 to 300 m depth. To expedite these plans more Aboriginal Heritage site clearances were completed by Laura Holdings.
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