Exploration for possible buried sandstone-hosted uranium mineralisation which could have formed within early Tertiary palaeochannel sediments of the northern Saint Vincent Basin is being carried out in a small area near Kainton on north-eastern...
Exploration for possible buried sandstone-hosted uranium mineralisation which could have formed within early Tertiary palaeochannel sediments of the northern Saint Vincent Basin is being carried out in a small area near Kainton on north-eastern Yorke Peninsula, granted on 27/8/2007 as EL 3911. It is believed that, in the Tertiary, the drainage headlands of exposed palaeochannels that existed here could possibly have included weathered outcrops of uranium-bearing granite lying to the north-west. The main target for investigation is the Yorke Peninsula Palaeochannel, and in some areas where it is known to exist it is up to 5 km wide and contains fluvial sediments that are at least 90 m thick. But in other places, the palaeochannel is split into narrower parts around low bedrock highs, as appears to occur on EL 3911. During the first licence year, Marmota conducted a reconnaissance field trip through the Kainton tenement area, and also reviewed relevant historical geological and geophysical data. Plans were made to undertake more accurate palaeochannel delineation by employing closely spaced gravity, AEM/TEM, radiometric and groundwater survey methods. Once the channels and their internal sedimentary architecture had been accurately defined and prospective zones outlined, it was intended that intensive drilling would be carried out to test those zones. A second, larger licence area situated immediately to the north, extending between Melton and Ninnes Plains, was granted to Jeff Olliver on 7/12/2007. Subsequently, ownership of this piece of ground was transferred to his client Robert Smith on 8/9/2008; then, a year later, the tenure was sold to Marmota Energy on 1/7/2009. Initial interest here was for asssessing the potential for commercially viable quarrying of Cambrian dolomite strata, both to provide rubble for road construction and to produce material suitable for metallurgical reduction processes. Only limited field reconnaissance was undertaken, as a precursor to planned shallow scout percussion drilling of dolomite subcrops which, due to the tenement transfer, never took place. After July 2009, the exploration focus for the larger area of the combined tenement package was widened to include the Cambrian and Adelaidean carbonate-rich metasedimentary sequences, which are potential hosts of Mississippi Valley type Pb-Zn-Ag mineralisation, as well as the basement Proterozoic sequences which are prospective for IOCG ± U mineralisation. Marmota has chosen primarily to investigate the latter, due to the recent nearby discovery by Rex Minerals Limited of a significant IOCG deposit called Hillside, that occurs within a magnetic anomaly trending along/adjacent to the Pine Point Fault. The locus of the Hillside deposit mineralisation appears to be controlled by secondary parallel faults which have trapped a magnetite-rich IOCG alteration system. The Pine Point Fault continues along strike to the north, through ELs 3911 and 4000 lying only about 50 km away, making Marmota's tenements prospective for equivalent IOCG ± U mineralisation. During Year 3 of the JV's tenure, Marmota undertook major geophysical surveys, acquiring 50 m flight line spaced aeromagnetic data and 200 m regular grid spaced ground gravity survey data across the entirety of the subject licence areas. These datasets were used, in conjunction with ground magnetic surveys run during February 2010, for target generation within the Melton Project, taking as critical components the Pine Point Fault and published structural and geophysical characteristics of known haematite and magnetite - dominant IOCG mineralisation systems. The detailed airborne geophysical survey was flown along east-west lines during September 2009, using a 30 m mean terrain clearance, for a total coverage of 3759 line km. The semi-detailed ground gravity readings were obtained in December 2009-January 2010 from 2157 stations covering aeromagnetic anomalies in the southern portion of the project area. Three targets were identified (Melton, North White Cliffs and Miranda) and to test them, starting in mid-February 2010, 7 mainly inclined and fully cored diamond drillholes were completed with a total penetration of 3378.4 m. Magnetic only anomalies at Melton and North White Cliffs were tested by one and two holes respectively, and a semi-coincident gravity and magnetic anomaly at Miranda was drilled in effectively three separate locations. The drilling resulted in Miranda being identified as the most prospective of the chosen targets, which will require further work, in part due to it being the shallowest at ~200 m depth to basement, and because of the encouraging hits of mineralisation that it contains. Over both of their approximate hole depth intervals 440-500 m depth, holes MIRDD01 and MIRDD04 encountered low grade copper±cobalt vein style mineralisation within an amphibole±magnetite±haematite±pyrite±chalcopyrite bedrock alteration assemblage. This alteration assemblage, with its low grade probaby skarn type mineralisation of unusual appearance, is interpreted to be sourced from the interfinging intrusion of a large gabbroic body into a Wallaroo Group metasedimentary package. Similar but more intensely altered metasediments were also encountered at the North White Cliffs prospect in hole NWCDD02, but no copper sulphides were seen and no anomalous geochemical values were returned from assaying of selected downhole samples from below 515 m hole depth. NWCDD01 did not encounter any Mesoproterozoic metasediments, but instead penetrated a massive non-magnetic gabbro intrusion below 393 m hole depth. The Melton drillhole, situated the closest to the Pine Point Fault zone of all the holes attempted, encountered intensely fault-brecciated basement metasediments below 424 m hole depth, which have hydrothermally imposed thick carbonate-magnetite veining that has subsequently become metamorphosed into a marble. Minor sulphides, including trace chalcopyrite, occur in the veins, but not in amounts sufficient to excite interest. During Year 4 of the subject licences' tenure, Marmota undertook downhole EM surveys of two drillholes, MIRDD01 and MIRDD04, the surveys being contracted to Zonge Engineering. Processing of the data was undertaken by Montana Geophysics, but no clear EM anomalism was seen. Further work was also done on the magnetic and gravity shell 3D model of the Miranda target by Montana Geophysics, using petrophysical information obtained from the lithologies intersected in the phase 1 drilling to further define the geophysical response of the Miranda target area. This model data was then compiled and used in preparation for a phase 2 drilling program on EL 3911, which was planned to follow up low grade copper mineralisation intersected at the southern end of the Miranda target. This second drilling campaign, of 4 inclined diamond holes for 2032.7 m, was conducted during March to May 2011, and geochemical results from it were received just prior to the report submission date. Best copper assay results were 3 m @ 0.25% Cu from 373 m downhole in hole MIRDD06, within a coarse grained granite, 9 m @ 666 ppm Cu from 422 m downhole in MIRDD07, within a gabbro, and 4 m @ 677 ppm Cu from 435 m downhole in MIRDD05, within altered metasediment close to gabbro. Overall, the drilling done so far at the Miranda target had shown that the bulk of the gravity anomaly is due to a large gabbroic intrusion, which is foliated in parts, and has later been intruded by irregular carbonate ± haematite ± pyrite veins of varying intensities. The gabbro was thought to mainly (but not necessarily) underlie an intensely deformed and altered layered metasedimentary unit that was interpreted to be a part of the Palaeoproterozoic Wallaroo Group. These metasediments are in places pervasively overprinted by an amphibole ± magnetite ± haematite ± pyrite ± chalcopyrite alteration sequence containing low tenor copper and cobalt mineralisation. The alteration assemblage was interpreted to be sourced from the intrusion of the gabbroic body into the metasediment, with the intensity of the low temperature skarn type alteration diminishing away from the contact. The contact zone itself at this stage of investigations was regarded as prospective. Further downhole EM surveying was therefore planned in order to try to detect conductive sulphides in or near to the intrusion contact zone. In June 2011, a 2407 line km detailed airborne magnetic and radiometric survey was flown over access approved parts of EL 4648 Paskeville, along east-west flight lines spaced 50 m apart and using variable sensor mean elevations above the ground surface of 30-50 m (or 100 m where landholders had requested). The aim of this survey was to try to detect any higher potential (than so far seen) igneous breccia style IOCG targets in the basement rocks.