Diamond exploration undertaken within the southern of two adjoining licence areas taken up along part of the western flank of the Peake and Denison Ranges, that is centred ~100 km south-east of Oodnadatta, was aimed at discovering the source(s) of nine microdiamonds and of widespread diamondiferous kimberlitic indicator minerals (DIMs) previously recovered in the region. No field work took place during the first two years, while office studies were performed on data acquired by previous diamond explorers Stockdale Prospecting and Ashton Mining. Their original airborne magnetic survey data were reprocessed and interpreted for licensee Reedy Lagoon Corp. by consultant Hugh Rutter (i.e. the 1981 Ashton Mining 300 m flight line spaced data, and seventeen 125 m spaced helimag traverses flown by Stockdale during 1984-1985). This study identified 31 untested magnetic anomalies which would require ground-based follow-up. Following the entry of Juka Mine Management (JMM) through joint venture, to manage ongoing ground activities, Stockdale's five formerly drilled magnetic kimberlite targets were subjected to check ground magnetic surveying (with readings taken at 10 m intervals over 3.79 line km) to ascertain the repeat validity of earlier magnetic anomalies and their siting of test holes on them. It was found that the anomalies had been well defined by Stockdale's original ground magnetic and ground EM surveys, and that the former drilling had adequately tested them. Between April 1989 and March 1990, the joint venture partners collected 13 surface samples of Jurassic and Permian sediments and studied them for kimberlite indicator minerals. Only the Jurassic sediments from the 'breakaway' site previously investigated by Stockdale, at a location 9 km North-west of Nilpinna Homestead, returned any indicators. Following recommendations made to JMM by consultant George Williams, a total of 158 tonnes of Jurassic basal Algebuckina Sandstone sediments, taken from 21 costean pits and trenches dug during March 1990 over approximately two square km just to the west of the latter site, were treated during April-May 1990 to obtain heavy mineral concentrates for mineralogical examination. However, only one microdiamond was recovered (a 0.0175 carat stone in the 1-2 mm grainsize fraction of sample B1 2.8-3.3 m). It was concluded that the sediments of the 'breakaway' region are diamondiferous, but at a concentration of little significance economically. This disappointment induced the partners to re-direct their exploration plans away from finding Early Jurassic alluvial placer diamond deposits, towards investigating the hard rock diamond source potential of the many magnetic anomalies already identified on EL 1535 and on adjoining JV project ELs 1630 Duff Creek and 1640 Mount Anna. After Reedy Lagoon Corp. resumed control of exploration on the subject ground, 32 aeromagnetic anomalies were selected for confirmatory ground magnetic surveying. When CRA Exploration farmed into the licence eight months later, also seeking to identify a primary kimberlite source, that company performed ground magnetic traverses over 20 selected anomalies, and then collected gravel and loam heavy mineral samples consisting of approximately 30 kg of -2 mm material which were processed and observed for diamonds and indicator minerals. Several of the magnetic anomalies were deduced to arise from dolerite intrusions; however, 4 of another 10 anomalies which were surface sampled returned DIMs. At anomaly A9, an 800 nT, 450 m x 200 m magnetic anomaly was defined. Here loam and gravel samples reported chromites and picroilmenites. Investigation of the chromites showed them to be non-kimberlitic. Rock samples of dolerite and a fine grained basic material were submitted for petrological description and geochemical analysis. The geochemistry of the two samples did not support a kimberlitic association. Sample 2544748 was described as a dolerite and 2544749 as a leucoxene-quartz-epidote/sausserite-phlogopite-amphibolite schist, interpreted as a sheared and retrograded basic lithology and as such possibly equivalent to 2544748. Three follow up gravel samples were collected at anomaly B7. One of the three samples reported chromites and picroilmenites. Again, studies of the chromite grains revealed them to be non-kimberlitic. Ground magnetic traverses read at anomaly B9, located 600 m south-east of the Last Chance copper workings, defined an 100 nT, 250 m diameter anomaly that lies within the Peake Metamorphics, but no outcropping magnetic source rock was identified. Chromites, picroilmenites and a pyrope indicator grain were recovered from follow-up loam and gravel samples. The chromites were found to be non-kimberlitic. Despite the presence of indicator minerals in samples at a number of the magnetic anomalies, CRA felt that no further work could be recommended due to the absence of diamonds and the non-kimberlitic nature of the chromites. During CRA's farm-in programme, abandoned copper workings at Coominaree, War Loan and Last Chance were also investigated for possible associated uranium and gold mineralisation via the conduct of geological mapping and rock chip sampling plus ground scintillometric and magnetic surveys and 100-200 m flight line spaced helicopter-borne spectrometric surveys. No significant such mineralisation was identified (best assay value 1.77 ppm Au over 40 cm at the War Loan prospect, from within a 1.0 m thick ironstone bed with only ~100 m strike length). Radiometric data from the Ashton Mining 1981 airborne survey were acquired and processed, but CRA's follow-up of several 5x background level radiometric anomalies identified no significant uranium mineralisation. Data from previous geochemical surveys were reviewed. A 25-80 ppm Cu anomaly located by North Broken Hill to the north-east of Mount Fox was inspected by CRA, but had no signs of significant copper mineralisation. Ground magnetic and soil geochemical traverses made by CRA across a 4 km long section of a 14 km long folded stratiform magnetic feature within the Neoproterozoic Skillogalee Dolomite located no significant base metal, gold or silver anomalism. After exploration management of EL 1535 was returned to Reedy Lagoon Corp. on 2/7/1993, the licensee resumed following its prime focus on determining the kimberlite potential of the four aeromagnetic anomalies known to have many associated DIMs. When taking some interested representatives from Poseidon Exploration to these places in June 1993 on a field visit, further loam samples were collected for heavy mineral analysis and recovered DIM grain (picroilmenite, pyrope and chromite) mineralogical studies done via electron microprobing. At this stage of its work, the licensee believed that an Early Jurassic or Pre-Ordovician source for the definite DIM grains recovered from the Peake and Denison Ranges region was evidenced by its accumulated data to probably exist within EL 1929. Such a source(s) would have in the past been eroded and thereby contributed DIM grains which are now incorporated into the Jurassic sediments. Reedy Lagoon now interpreted it to be located in such a position geologically that it is either no longer contributing DIM grains, or else is contributing a very restricted number of grains, to the existing land surface. It therefore surmised that Ordovician diapiric breccia, now present at surface extensively in the A10 drainage and near the Last Chance magnetic anomaly, may be concealing kimberlite pipes and may have dispersed kimberlitic material (during the breccia's emplacement) which has subsequently been eroded and incorporated into younger sediments. The basis for this revised thinking was the realisation that if the DIM source(s) was exposed to current erosion, then the extensive stream sediment sampling programmes that have been conducted in the region should have identified it more clearly. During June 1995, Reedy Lagoon conducted a 323 line km ultra-detailed low-level helimag/rad survey across two grids on the subject renewed (over an 18% reduced area) EL 1929, flying north-south grid lines spaced 50 m apart, using a 50 m sensor height above the ground surface. Five inferred intrusive kimberlite magnetic targets were mapped from this new geophysical data - A7, A8, A10, B9 at the Last Chance prospect, and G1 at The Gauntlet prospect, which target straddles the north-western corner of EL 1929 and extends onto EL 2105. During November 1995, a preliminary aircore drilling programme was conducted by the licensee to evaluate four of the above anomalies (9 vertical NQ holes for a total penetration of 123.4 m). The first four of the holes were drilled near the Last Chance prospect to a maximum depth of 15.3 m, bottoming in magnetic Early Proterozoic Baltucoodna Quartzite. The other five holes tested dispersed magnetic features in the A10 palaeodrainage anomaly, to a maximum depth of 36 m. No kimberlitic DIMs were recovered by either set of drillholes, so their results were inconclusive for diamond exploration. However, drill cuttings from the depth interval 0 to 12 m in hole ECAC07 returned an average 0.07 ppm Au, while in surface sampling of bedrock exposed within the A10 anomaly, rock chips of a ferruginised and quartz-veined dolerite containing minor malachite, that were collected near hole ECAC10, returned a maximum value of 1490 ppm Cu. In order to accelerate the pace of exploration and in particular conduct much more drilling work, Reedy Lagoon during the first part of 1996 successfully sought to introduce a new joint venture partner to the project. In late April 1996, Caldera Resources NL entered a joint venture with Reedy Lagoon over both its adjoining ELs 1929 and 2105, to manage and fund ongoing exploration in order to earn a 70% interest in the licences. After the new entrant assumed operating the diamond search and carried out a critical review of previous work on the subject licence area, it highlighted the missed significance of reported occurrences of rare crandallite group alkaline igneous indicator (barium-strontium and rare earth hydroxy-phosphate) minerals encountered in loam sampling near Reedy Lagoon's G1-G3 subtle helimag anomalies, and so it widened the range of potentially diamondiferous intrusive rock types sought by the exploration model accordingly. During December 1996, Caldera flew a fixed-wing airborne magnetic/radiometric survey across both project ELs, recording 999 line km at 200 m north-south line spacing and an average 60 m sensor elevation. From its data Caldera interpreted 14 possible targets, and then proceeded to acquire 26 traverses of ground magnetic and ground gravity coverage over five of them during August 1997. Three of these priority targets, magnetic anomalies G1-G3, lay within the Gauntlet prospect, situated about 3 km north-west of where Stockdale's bulk loam sampling had recovered several microdiamonds. Caldera made plans during late 1997 to drill two of the possible kimberlite targets which lay on EL 1929, with up to 2000 m of deep RC drilling envisaged, to utilise a rig then being employed by the company on its Abminga diamond exploration project. However, due to unforseen issues with obtaining Native Title clearances for drill site access there, the Edward Creek programme was abruptly brought forward in the contracted rig time before any suitable site preparations could be made. Because of the wet winter/spring weather and complete lack of needed substantial earthworks to give transit to the 30 tonne drilling rig into most of the target areas across the many small local watercourses, Cauldron was forced to abandon its drilling activity in November 1997 after completing only 2 RC holes for 322 m on the G1 anomaly, at sites located near the main William Creek - Oodnadatta road. Downhole samples were then sent to Canada for heavy mineral separation and DIM content assessment. At an early point in this latter stage, Cauldron made the decision on 28/1/1998 to exit the joint venture at Edward Creek.