The greenfields Ridgeback prospect, located about 5 km east-southeast of Bute on the northern Yorke Peninsula, is being explored by EL 4278 sole licensee Investigator Resources for possible Hillside deposit look-alike, Proterozoic basement-hosted economic IOCG mineralisation that may be associated with the northwards extension of the buried Pine Point Fault zone. A programme of moderately deep diamond drilling was proposed to test certain aeromagnetic anomaly targets generated by the company during 2009, which had been geophysically modellled as occurring at around 450-450 m depth. Detailed gravity data acquired on the licence area early in 2010 had shown that a subtle gravity high is present adjacent to the magnetic features. Historic mineral exploration drilling undertaken in the Bute area has variously penetrated Cambrian limestone, sandstone and siltstone overlying Adelaidean quartzite, dolomite and siltstone, that in turn overlies Mesoproterozoic/Palaeoproterozoic basement. The nearest drillholes to the subject PACE project target area (North Broken Hill B-14 and B-15) had encountered the Mesoproterozoic Bute Metadolerite and Wandearah Metasediments at a vertical depth of about 400 m. Due to delays in obtaining landowner agreement for ground access onto the preferred southern of the two magnetic targets, the northern combined magnetic/gravity anomaly was advanced as the target of two drillholes selected for PACE Initiative funding as approved project DPY6-39. The Ridgeback North drilling took place over the period 1/9-26/9/2010, and in total comprised 73.7 m of rotary mud precollars plus 932.3 m of HQ/NQ diamond coring. Detailed analysis of the recovered drill core was undertaken at nominal 1-metre sampling intervals, with data being obtained on rock properties that included specific gravity, magnetic susceptibility, structural geology measurements, detailed lithological logging, petrological studies (10 selected samples), and multi-element assaying by ICPMS and AAS of selected drill core intervals (for a total of 278 downhole geochemical samples). Drillhole RBDDH001 reached the Cainozoic - Neoproterozoic unconformity at 38 m depth, below which lie Tapley Hill Formation and Appila Tillite, followed unconformably at 150 m depth by a thick interval of Mesoproterozoic Bute Metadolerite, which appears to persist with the same lithological character down to a shear zone encountered at 285 m depth. On the footwall side of the shear zone the lithology changes to moderately altered metasediments (Mesoproterozoic Wandearah Metasediments) and interbedded Bute Metadolerite containing several distinct phyllonitic shear zones. From 529 m depth down to the end of the hole there is a sequence of bedded lapilli tuff, containing clasts ranging from andesite and basalt to metasediments and jaspilite. Several metres of the drill core are interpreted to have been cut through a single metasedimentary clast deposited within this tuff. One zone of the lapilli tuff has magnetite-bearing clasts, and another zone has hæmatite-rich clasts. It should be noted that the occurrence of lapilli tuff in this drillhole seems to be unique for the Bute area, because the company geologist has examined stored drill cores from many of the nearby holes, but did not see lapilli tuff or anything similar in them, nor were such rocks logged in past drillhole records for the area. Drillhole RBDDH002, after passing through essentially the same uphole section as in RBDDH001, down to the unconformable base of the Appila Tillite, appears after that to have remained within Bute Metadolerite for much of its length (i.e. from 151.5 to 402.5 m depth), wherein occur minor hæmatite-dusted zones and occasional quartz-feldspar veins. Later close inspection of the drill core has detected a number of metasediment intervals not initially recognised in hand specimens in the field, due to the sometimes subtle, barely discernible differences between fine-grained, chloritic metasediments and the slightly foliated, chloritic dolerite. Density measurements made on the drill core recovered from this hole were unable to resolve whether the gravity anomaly had been intersected, however, the amount of hæmatite alteration to the dolerite could account for the targeted gravity anomaly if the hæmatite content continues to increase with greater depth. Minor chalcopyrite mineralisation (1 m @ 0.5% Cu) was noted in quartz-carbonate veins logged at a depth of 322-323 m. Although no significant downhole intersections of copper-gold magnetite-hæmatite (possible Hillside analogous) mineralisation were encountered, and only minor amounts of copper and gold were detected in the drill cores, a number of positive conclusions have emerged from reviewing the results of this drilling programme. 1) The depth to Mesoproterozoic basement is considerably less than originally thought. Based on the (relatively) nearby previous drilling, a depth of 400-450 m was anticipated, and all of the initial geophysical modelling of the aeromagnetic and gravity data had assumed this depth to be a good approximation. Future re-modelling of the geophysical data, based on drill core density and magnetic susceptibility measurements plus the realised depths to basement, may give cause to re-assess the potential of remaining drill targets. Also of significance is the lower cost for doing exploration under just 120-140 m thickness of post-Mesoproterozoic "cover", which now represents an upside factor for exploring this area. 2) Several broad, steeply dipping NNW-SSE trending shear zones were encountered- these are interpreted as being the northern extensions of the Pine Point Fault Zone. These shear zones and associated breccia zones can play a significant role in acting as conduits for possible mineralising fluids. 3) Several zones of hæmatite-altered breccia were encountered in both PACE drillholes, with the alteration tightly constrained within the breccia zones. A number of zones of weak, pervasive hæmatite alteration were noted through both holes. This could indicate that there have been significant volumes of iron-oxide-rich fluids circulating in the region and that the Ridgeback North target may be somewhat distal to an IOCG hydrothermal system, or may represent a different style of mineralising system active in the area. The origin of these fluids could be the probable intrusive igneous body (?granite/gabbro/norite) which has been interpreted from the regional aeromagnetic data as lying directly beneath the town of Bute and trending towards the SW. This area is also currently held under licence by Investigator Resources (EL4618). 4) The identification of the lapilli tuff may indicate proximity to a hitherto unrecognised volcanic centre. 5) The prime magnetic target (Ridgeback South) still remains to be tested, as do numerous coincident and semi co-incident gravity and magnetic targets within the project area.