DGO’s Mallina tenements adjoin De Grey Mining’s Mallina Gold Project and share a similar geological and structural setting to De Grey’s tenements which host substantial structurally controlled gold resources and the significant Hemi discovery.
The DGO tenement package incorporates over 30km’s of strike length of a major ENE-trending structure that parallels the Mallina Shear Zone (MSZ). Gold occurrences in the region are concentrated on shear structures and is associated with intrusives and anticlinal fold axes. Gold nugget discovery and soil samples up to 1.2g/t at Scottie Well, and Coziron drilling results at Top Camp, supports a target over 16km strike length at the intersection of anticlines and the ENE trending structure.
Anomalous gold and arsenic results identified from wide spaced soil sampling and initial aircore drilling over potential Hemi style intrusives are being evaluated with infill soil sampling to refine drilling targets.
DGO has an extensive tenement holding in the Yerrida Basin comprising over 2,500km2 located 25 to 100 kilometres from Sandfire Resources’ DeGrussa operations. The Company is targeting:
An airborne electromagnetic (AEM) survey flown over a 20km Au-Cu-Zn soil anomaly in 2019 defined a series of priority EM conductors within the Killara, Doolgunna and Johnson Cairn Formations which are the Yerrida Basin stratigraphic equivalents of the formations in the adjacent Bryah Basin that host the DeGrussa copper/gold deposit. Subsequent soil sampling delineated strong coincident mutli-element geochemical responses with elemental signatures indicative of massive sulphide mineralisation (Cu, Pb, Ag, Mn, Ba, Bi, Se, Sn, Te, Tl) associated with AEM targets proximal to the margins of the Killara Formation. Conductors defined from ground EM traverses over priority AEM and geochemical targets are the focus for drill testing for DeGrussa style copper-gold mineralisation.
Detailed data review and analysis has also confirmed that the Yerrida Basin represents a favourable, intra-cratonic, restricted basin setting of the right age, prospective for stratiform sediment-hosted copper (SSH Cu) deposits analogous to the world-class Zambian Copper Belt (ZCB).
Targets for ZCB copper mineralisation are associated with the reduced carbonaceous and pyritic siltstones of the Johnson Cairn and Maraloou Formations immediately overlying the oxidised clastic units of the Juderina Formation where the formations on-lap granite basement highs along the margin of the basin. DGO has extensive strike lengths of the prospective contacts within its tenements on the margins of the Goodin Dome in the north, the Archean basement granites in the south and on concealed basement highs interpreted from geophysics.
Broad spaced soil sampling over the Johnson Cairn-Juderina and Maraloou-Juderina contacts delineated copper and gold anomalies with infill and extensional sampling proposed to refine drill targets.
DGO’s Pernttty Lagoon tenements are located in the Eastern Gawler Craton, South Australia within the Stuart Shelf Copper-Gold Province which hosts BHP’s world class Olympic Dam copper-gold-uranium mine, and a number of other copper-gold deposits including Oz Minerals’ Prominent Hill and Carrapateena deposits. DGO’s tenements cover 2,200km2 over eight exploration licences to the east and south of the Mount Gunson copper deposits, approximately 120km northwest of Port Augusta.
DGO’s initial targeting in the Stuart Shelf was based on research carried out at the Centre for Ore Deposits and Earth Sciences (CODES) at the University of Tasmania under a proprietary research agreement between DGO and CODES. This research identified the carbonaceous Tapley Hill Formation shale as a strong redox trap for gold and copper mineralisation and the unconformable contact between the Neoproterozoic Tapley Hill Formation and underlying Mesoproterozoic Pandurra Formations as being prospective for copper-cobalt mineralisation based on the Zambian Copper Belt (ZCB) model.
The Tapley Hill Formation is part of the Neoproterozoic Adelaide Rift Complex-Stuart Shelf succession and is the same age as the Katangan Supergroup which hosts the Zambian Copper Belt. The basin setting at Pernatty Lagoon has many similarities with the edges of the Katangan Basin which hosts deposits such as Chambishi (124Mt @ 2.6% Cu).
Analysis of historic drill core by the Company’s consultant, Dr Stuart Bull, an expert in ZCB deposits has confirmed that the lithological characteristics of the Tapley Hill, combined with the documented presence of copper in the area and the thinning of the shales as they on-lap the Pernatty Upwarp provides a similar basin margin setting to that which hosts the ZCB deposits. Furthermore, the interpreted transition from the shallow water Woocalla Dolomite to deep basin Tapley Hill shales overlying the oxidising Pandurra Formation sandstones is analogous to the best mineralised position in the Zambian model.
The review identified significant copper in historic drill holes immediately east of DGO’s tenements, including 1.9m @ 1.7% Cu from 185m in hole PRL10/SAR5, at the Tapley Hill-Pandurra contact close to the interpreted transition zone and chalcocite present in Woocalla Dolomite within drill hole PY4 on the margin of Pernatty Lagoon indicating that the copper mineralising process is active in the area. . These results highlight the lack of exploration within the interpreted transition zone and the potential for significant mineralisation.
DGO also completed a collaborative research project with CODES which applied laser-based analysis of sedimentary pyrite in the Tapley Hill Formation to identify the presence of traces of indicator elements and isotopes providing vectors towards sediment-hosted copper mineralisation.
A cluster of historic drill holes approximately 5km to the east of Pernatty Lagoon, analysed by CODES show Pb isotope ratios, and elevated Ag, Cu, As and Ti in pyrite which supports the contention that a copper mineralised body could be present along the east dipping Tapley Hill-Padurra unconformity surface below and to the east of Pernatty Lagoon. In particular, analyses by CODES on samples from drill hole PN-06-03 suggest that it is proximal to a copper mineralised body.
Pernatty Lagoon represents a compelling, shallow and highly prospective copper target in a province where sedimentary copper potential has been largely ignored for the last 40 years. DGO is in the process of negotiation access with the Kokatha Aboriginal Corporation to facilitate proof of concept diamond and reverse circulation drilling to test the extensive transition zone target.
DGO’s Bryah tenements are prospective for sediment-hosted gold with the central tenement containing areas of known gold nugget occurrences adjacent to Judge’s Find. Gold mineralisation is thought to be controlled by thrust-fault bounded, anticlinal structures at the contact of the Juderina Sandstone and Johnson Cairn Formation black shales.
An airborne electromagnetic (AEM) survey in 2019 identified thirteen conductive anomalies, including nine along the axis of a regional anticlinal structure within the Juderina Formation. Reverse circulation drilling and analysis of multi-element assay data on four anomalies along strike from Judge’s Find nugget field in March 2020, identified a thrust stacked succession of the Juderina Formation containing variously metalliferous black shales with background gold in sedimentary pyrite ranging from 4 to 150ppb. The black shales represent good source rocks for sediment-hosted gold deposits through the leaching of gold and deposition in the overlying stratigraphy. This leached gold is most likely the source for the nugget gold found in surface cover at Judge’s Find.
Conversion of gold-bearing sedimentary pyrite to pyrrhotite observed in drilling, indicates the release of the gold and arsenic to a metamorphic fluid which has the capacity to deposit gold potentially along the thrust faults or at the contact with the overlying Narracoota volcanics, by sulfidation processes. The proposal is supported by the occurrence of a number of gold prospects located along the base of the Narracoota volcanics.DGO is planning drill testing of potential sediment hosted gold targets associated with elevated magnetic responses, potentially indicative of zones of pyrite to pyrrhotite conversion and corresponding release of gold, as well as exploration for DeGrussa style mineralisation highlighted by AEM and magnetic targets in the Narracoota volcanics.
DGO’s Black Flag tenements cover 30km2 over Black Flag Group metasediments, volcanics and felsic intrusives approximately seven kilometres north-northwest of Horizon Minerals’ Teal Well open pit. This mine produced 21,800 ounces of gold at a grade of 3.2g/t. Mineral resources at Teal, Peyes Farm and Jacques Find total 4.25 million tonnes at 2.1g/t Au for 289,000 ounces (IRC Quarterly Activities Report 30 June 2019). The mineralisation is hosted in a series of semi-parallel shears within Black Flag felsic volcanics and sediments defining a +200 metre wide northwest trending, mineralised structural corridor which trends into First Au Limited’s tenements then onto DGO’s tenements to the north.
Gold mineralisation is localised by north-east cross cutting faults and on intrusive contacts within an extensive zone of sulphide alteration in intermediate volcanics and felsic intrusives. The geology is concealed beneath alluvial and lacustrine sediment cover and is poorly drill tested. Further drilling is planned to evaluate the structural targets.
Lake Randall is located 50km east of Gold Fields St Ives operation and immediately south of Silverlake Resources’ Mt Belches Mining Centre. DGO holds 230km2 of untested, prospecive terrain under lake and transported sediment cover.
Gold mineralissation at Mt Belches is hosted in Banded Iron Formation (BIF) units and is localised in anticlinal fold hinges and on the limbs of chevron folds within the Mt Belches area. DGO’s ground gravity survey delineated a folded sequence of sediment and mafic units beneath the lake cover and identified similar structural targets on the limbs and noses of folds to those hosting the Mt Belches gold deposit.
DGO’s recently granted tenements cover 728km2 over the poorly explored Deleta Greenstone belt located between the mineralised Yamarna Greenstone belt 40km to the east and the Duketon belt 40km to the west.
The tenement area is extensively soil covered and DGO is targeting gold mineralisation on structures related to the major north-north-west trending De La Poer Fault. Interpretation of geophysical datasets is in progress to refine structural targets for geochemical surveys and drilling.
DGO’s Tom Price tenement applications cover a large, 70 km long regional anticlinal structure, within the Pyradie Formation which is prospective for sediment hosted gold mineralisation. Previous exploration of the structure identified anomalous gold mineralization up to 2.8 g/t gold in rock chip samples of siliceous chert units assigned to the Pyradie Formation (IGO ASX announcement 28 July 2003).
Negotiations with native title parties are progressing to facilitate grant of the two large exploration licences.