A renewed effort to determine the diamond mineral potential of the 15.6 square km of land comprising Flinders Island was instigated during January 1999, under tenure of EL 2577, by Orogenic Exploration Pty Ltd, a company related to the previous explorer Diamond Ventures NL which until 25/5/1998 had held EL 2338 (see open file Env 9447). Initial work comprised the processing of and observation of mineral grain concentrates from the 18 heavy mineral (HM) loam samples that had been collected by Diamond Ventures during early 1998, plus HM analysis of another 9 bulk loam samples (total weight 279.5 kg) which Orogenic Exploration collected from above selected magnetic anomalies. Later on, between August 1999 and November 2000, a further 94 HM loam samples were collected and similarly treated. A significant number and range of kimberlitic indicator heavy minerals (KIM), e.g. high-Mg chromite, pyrope garnet, forsterite, picroilmenite, micas and chrome diopside, were recovered from 20 of these 112 reconnaissance geochemical samples. A selection of 139 indicator mineral grains were chemically analysed via electron microprobe, and the outcome confirmed their likely kimberlitic nature. It also suggested that a possible new, as yet undiscovered Flinders Island source kimberlite or cluster of related small intrusions would have a composition distinct from the known Mount Hope area kimberlite intrusions located near Elliston on the mainland. In the licensee's opinion, the overall diagnostic chemistries of the recovered Flinders Island HM grains are superior to those of KIMs derived from the known diamond-barren kimberlites occurring east from Elliston. During May-June 1999, Orogenic Exploration acquired infill coverage to the SA Government's TeiSA Area A4 regional airborne magnetic/radiometric/DTM survey flown by contractor Kevron Geophysics. This infill consisted of 1180 line km flown along east-west orientated lines spaced 50 m apart, using an 80 m sensor mean terrain clearance, which profiled the entire EL 2577 area. The survey data was submitted to consultant geophysicist Nigel Hungerford for processing and interpretation, hopefully to generate kimberlite anomaly targets. He identified 15 magnetic anomalies on the island which required further investigation. However, the granite bedrock of Flinders Island is magnetically noisy and made selection of possible kimberlite targets difficult. During the second licence year, Orogenic Exploration commenced a systematic grid HM loam sampling programme in order to spatially narrow down the source of the KIMs. Using the airborne DTM data, the island was divided into current drainage basin zones for detailed loam sampling, to be undertaken as a guide to planning shallow aircore or RC drilling of kimberlite targets concealed beneath shallow sand and calcrete cover. 58 bulk loam samples totalling over 2 tonnes in weight were collected during June 2000, mainly on 200 m grid centres from the area known as Gem Paddock, which forms the hinterland to Gem Beach on the north-western side of the island. After doing laboratory heavy mineral separations to obtain 75 g of HM concentrate, most of these samples were found to be positive for KIMs, but no microdiamonds were observed. 947 selected HM grains were microprobed to determine their compositions, which again reflected a kimberlitic petrogenesis. The numbers, type and grainsize range of the HM concentrate grain assemblages all indicated that a kimberlite intrusion must lie at not too much distance. The third, fourth and fifth licence years of EL 2577 were devoted mainly to obtaining complementary ground geophysical information to help prioritise the drill site selections. In May 2001, a detailed gravity survey was conducted over the Gem Paddock area, with 466 stations read on a 50 m x 50 m grid by Solo Geophysics. This survey's data was reviewed by De Beers Australia, and a 0.8 hectare extent pipe beneath 20 m of cover was interpreted. Next, during July and October 2001, Haines Surveys acquired additional detailed gravity readings on several anomaly grids located on the northern end of the island, the gravimeter occupying 246 and 1354 stations respectively. During February-March 2001, all of the licensee's Flinders Island loam sampling HM concentrates were re-examined by diamond exploration experts from a) Tikiri Mineralogical Consultants Pty Ltd based in Melbourne, and b) De Beers Australia Exploration Ltd based in Perth. These companies recommended sending off an additional 579 HM grains for microprobe analysis, which was done. During April 2001, a further 268 HM loam samples totalling 3.7 tonnes were collected on 400 m spaced centres across the entire island. One small microdiamond was recovered from a sample taken within EL 2577, and in general a significant number and range of KIMs were found, thus generating more target anomalies for exploratory drilling. During August-September 2001, the licensee performed soil geochemical sampling of the three separate claypans on Flinders Island, and submitted 8 samples for whole rock analysis. As well, 264 soil samples were collected from the Kapara Paddock KIM anomaly area and were sent off for mobile metal ion (MMI) partial leach digestion and assaying for a wide range of elements. The results indicated that the island's surface geochemical response is dominated by attributes of the amount of sand and clay materials present. A bulk density measurement was made on a sample of granite outcrop collected from the western side of Gem Point. On 6/12/2001, Orogenic Exploration was granted EL 2875 which covered the portion of coastal Flinders Island existing between the tidal Low Water Mark and a line drawn parallel to, and 800 m inland from, the High Water Mark. This ground had been excluded from the earlier-issued EL 2577, as it formed part of the coastal protection reserve legally defined for lands bordering the sea in South Australia. The State Government through DEHAA advised that it would temporarily lift the blanket environmental and heritage protection afforded this ground, provided that known sites of value were avoided, to allow approved diamond exploration works to proceed. During August 2002, Orogenic Exploration and its new joint venture partner Tawana Resources acquired a detailed low-level airborne magnetic/radiometric/DEM survey across all of ELs 2577 and 2875, the coverage totalling 1208 line km at 40 m north-south flight line spacing with a 20 m sensor height above the ground surface. During March 2003, Haines Surveys acquired further detailed gravity readings on eight grids over possible kimberlitic magnetic anomalies mapped by the above aeromagnetic survey. Between April 2002 and January 2003, a further 167 loam HM samples plus 358 drill chip samples and 103 drill core samples were processed for observation of HM concentrates, and nearly 5800 microprobe analyses were carried out by different laboratories, the majority of the work being done by De Beers. During July 2002 and December 2003, Zonge Research and Engineering Organization was contracted by the JV to perform a trial ground nanoTEM survey along 8 anomaly traverses at a 2.5 m station spacing, to look for evidence of thin kimberlite dykes that might underlie Kapara Paddock. A gradient IP survey on the Gem Paddock gravity grid was also done by Zonge during December 2003. Because of the useful EM data obtained by the trial nanoTEM survey, the acquisition of more nanoTEM data was commissioned in January 2004, as 11 traverses run through Gem Paddock with a 20 m station spacing, to give a total of 700 surface TEM readings across 3.6 line km. Diamond core drilling and aircore drilling down to bedrock of significant KIM anomalies and many associated or stand-alone magnetic, gravity or EM anomalies started in November 2001, and proceeded in separate campaigns using two different method rigs [a trailer-mounted Jacro 200 diamond rig from November 2001 until April 2002, and a truck-mounted 600 UDR RC percussion rig during May and June 2003]. A total of 96 shallowly angled BQ diameter fully cored holes and 171 vertical RAB/aircore open holes were completed, for an aggregate penetration of 3958.7 m (including 1508.45 m cored). During the course of the RAB drilling, 18 of the drillholes [prefixed WW], which together totalled 180.8 m in depth, were primarily designed to look for groundwater, with their siting and project management under the direction of the private property landowner. No useable quantity of groundwater was found. Minor amounts of very salty groundwater (TDS 42,275 ppm) were hit by drillhole FSE33 within Eocene Pidinga Formation palaeochannel sediments at 40 m depth beneath Gem Beach. Due to the variable lithology and competency of the cover sediments, drilling was difficult. Furthermore, because it was expected that there are granite boulders on, and within, any concealed kimberlite on the island, this meant that each drillhole needed to go some distance into the granite bedrock to fully test each site. At first only a single cuttings sample was taken from the regolith-basement unconformity to analyse for heavy minerals, but late in 2003 it was decided that in future all drill cuttings recovered at variable but narrow depth intervals would be fully sampled for indicator minerals to indicate if the drillhole has just missed intersecting a kimberlite. This step was taken because the aircore drilling conducted in Gem Paddock over the period January-June 2003 (77 holes for 743.75 m) had proved disappointing in that it had failed to find any traces of kimberlite. Also, a second trial of MMI soil geochemical sampling undertaken in the Gem Pan area late in December 2003 (26 samples assayed) had yielded fairly inconclusive results that seemed to reflect the distribution of soil constituents. A third phase of exploratory drilling commenced on 24 July 2004, to investigate geophysical targets located near significant known concentrations of KIMs. 89 NQ diameter vertical aircore holes for 2022.3 m were completed by 30 October, using the 11-tonne 600 UDR rig. No kimberlite was found by this drilling. 213 HM drill cuttings samples were collected, processed and observed, and 103 microprobe analyses were carried out on representative KIM grains. The range and quality of KIMs recovered remained extremely encouraging, as it included two small diamonds (mesofragments classified as > 0.5 mm maximum width) as well as a number of microdiamonds. The mineral concentrates from 31 of the processed drill cuttings samples, which came predominantly from holes drilled in the vicinity of Gem Paddock, yielded 520 chromite, 31 pyrope and many picroilmenite grains. Again, the landowner commissioned and organised the drilling of 15 of the above holes to act as groundwater exploration holes, for a total penetration of 176.0 m. No significant groundwater was found. Early in 2004, 8 additional samples of outcropping granitic basement rock were sent for detailed examination to consultant petrologist Dr B.J. Barron in Sydney, to build on information gained from the 4 samples previously examined by her in mid-2002. Details of the igneous zircon radiometric dating completed at Macquarie University by Dr E.A. Belousova during late 2002 were published in the Australian Journal of Earth Sciences (Vol 51, pp 611-619) during October 2004 [see Web link provided herein]. The studied granite gneiss to porphyrytic granite, which outcrops around Seal Point on the south-eastern side of Flinders Island, has been dated as late Palaeoproterozoic (1762 +/- 11 Ma): this distinct felsic unit, which is much older than the adjacent Calca Granite, has been formally named the Investigator Granite Gneiss. Further whole rock geochemical analyses were performed on 3 drillhole samples during May 2005, as well as multi-element assays; later, during September-October 2005, 36 KIM grains (mostly chromite) were comparatively assayed for a wide range of trace elements using the new LAM-ICPMS (laser ablation microprobe - inductively coupled plasma mass spectrometer) technique available at Macquarie University's geochemical research centre. All of these grains had earlier been microprobed conventionally, but that had only provided information about the minerals' major element contents. The new method, although currently expensive, provided a great deal of supplementary geochemical data which the JV partners expected should be of use in future exploration. Another 22 chromite grains were similarly assayed during February 2006. Late in 2005, 5 surface samples including beach gravels collected from the north-western coast of Flinders Island were processed for heavy mineral observation and KIM microprobing. 4 of the samples yielded HM concentrates in part containing a combined assemblage of 84 chromite, 32 pyrope, 7 picroilmenite and 1 olivine grains, all of which were analysed and shown to be kimberlitic. By the end of 2006, around 1600 in total heavy mineral samples had been collected from Flinders Island for processing and observation, with about 45% coming from drillholes. More than half of the samples had been found positive for KIMs, the relevant tally including 8 small diamonds. More than 7000 microprobe analyses had been performed on selected KIM grains. During early October 2007, a detailed helicopter-borne EM (50 Hz RepTEM) survey of 1149.4 line km was flown across the whole island by contractor Geosolutions, along ENE-WSW orientated flight lines spaced 50 m apart, using a loop/ sensor mean terrain clearance of 30 m. In early January 2008, during the tenth year of tenure, a detailed selective leach MMI soil geochemical survey was completed over the KIM anomalous Gem Beach and Dunstan prospect areas on the island, grid sampling down to 50 m centres. A total of 716 samples were collected and analysed for 42 elements. The results again appeared to reflect general soil composition. 12 drill core samples recovered from immediately above the granite basement in previously drilled holes spread across the length of the island were processed for HM and observed, in the hope of detecting, within partly transported regolith sediments containing weathered granite clasts, indicator minerals that may reflect a nearby source kimberlite. The samples were found to be negative for KIMs. 1305 new ground gravity stations were occupied by Haines Surveys during March-April 2008, in order to complete detailed gravity survey coverage of the entire island at approximately 200 m x 200 m station spacing. The survey confirmed the strong regional gradient downward to the north that is in part caused by the thick sediments of the Polda Basin. There also appeared to be an increased gravity response associated with the Investigator Granite Gneiss on the eastern side of the island. As the main density contrast is the change from sediment to fresh granite, use of this additional gravity data allowed more detailed sub-surface maps of the granite surface to be completed which show interpreted sub-surface drainage channels and divides. Of note here was the fact that when the kimberlite indicator grain counts within the last 5 m of penetration of all the drillholes are plotted on this map, the grains mainly occur within the Gem Paleovalley which heads towards the current Gem Beach. During June 2008, a study was made of the magnetic susceptibility of the granite around Kapara Point, on the east side of Flinders Island. Because the granite basement to Flinders Island has a complex magnetic response, the aim of the ground survey was to examine it, in an area of good outcrop, across one of the many prominent magnetic linear lows seen in the aeromagnetic surveys, and to test whether the magnetic susceptibility variations within the granite itself could cause the observed negative responses. Understanding this phenomenon could assist the JV in recognising kimberlite dykes or plugs within the magnetic lows. Kimberlites emplaced into granites tend to be linear and odd shaped, reflecting the high strength of the host rock. Within softer, less competent sediments, kimberlites are better able to develop the more rounded classic pipe shapes. Thus it is quite likely that any kimberlite on Flinders Island will be emplaced within, or at least resemble one of these magnetic linear lows.