Western Australia gold developer Ora Banda Mining Limited (ASX: OBM) has reported an increase in the underground Mineral Resource for the Riverina Project, a key part of its Davyhurst Gold Project.
The company announced that the underground Mineral Resource for Riverina increased by 46% to 728Kt @ 5.9 g/t Au for 139,000 ounces while the Total Mineral Resource at Riverina increased by 16% (44,000 ounces) to 3.7Mt @ 2.7g/t Au for 322,000 Au ounces.
OBM said that the initial assay results from the adjoining Riverina South exploration program are encouraging and the upgraded underground Resource would underpin Riverina underground mining study.
Davyhurst project area
The Davyhurst project area is located 120 km north-west of Kalgoorlie in Western Australia. It contains both historical open cut and underground mining operation and hosts some of the largest deposits within the project area. Considerable potential remains for the discovery of new gold deposits as well as extensions to existing resources.
Significant deposits within the Davyhurst project include Golden Eagle, Lights of Israel, Makai shoot, Waihi, Callion, Federal Flag, Salmon Gums, Walhalla, Walhalla North, Mt Banjo, and Macedon.
The Riverina Project area is located approximately 48 km from Davyhurst Processing Plant. The project comprises gold resources defined at the Riverina, Silver Tongue, Forehand, and Sunraysia deposits, as well as a number of advanced exploration targets.
The main Riverina deposit is one of five key priority mining targets at Davyhurst with an open pit reserve of 1.4Mt @ 1.8 g/t Au for 81,000 ounces. The Riverina Deposit is classified as a structurally-controlled lode deposit, with the highest-grade and most persistent “shoots” of gold mineralisation associated with quartz veining, veinlet arrays and associated silicification.
Resource upgrade at Riverina
Ora Banda has now announced a resource upgrade that follows modelling of the underground portion of the Main Lode of the main Riverina deposit. The Riverina Mineral Resource update is reported by applying the conceptual $2,400 pit shell which was generated using the Ordinary Kriged Open pit Mineral Resource block model which included Main. Central and Reggies lodes.
The Riverina Main Lode is located beneath the A$2,400 optimised open pit shell used to constrain the Riverina open pit resource. Historical underground mining of the Main Lode at Riverina was via a number of shafts, producing 99,500t @ 15.8 g/t Au for 50,490 ounces.
16% overall increase
The company announced that the underground Mineral Resource has increased 46% to 728Kt @ 5.9 g/ Au for 139,000 ounces, and incorporates a 37% increase in underground gold grade.
The underground component of the Riverina Mineral Resource is reported from the updated underground Mineral Resource model and includes all blocks outside and below the same A$2,400 optimised pit shell but with a cut-off grade of 2.0 g/t Au, reflecting the increased cost of underground mining.
OBM said that the open pit Mineral Resource remains unchanged at 3.0Mt @ 1.9 g/t for 183,000 Au oz. It may be noted that the open-pit component of the Riverina Mineral Resource is reported from the Localised Uniform Conditioning (LUC) model within a A$2,400 optimised pit shell.
The company announced that collectively, the total Mineral Resource at the Riverina Project has increased by 16% to 3.7Mt @ 2.7 g/t for 322k Au ounces. The Company’s total Mineral Resource now stands at 23.3Mt @ 2.7g/t Au for 2.05M ounces.
Mining study and additional deep drilling
The company announced that a mining study aimed at defining the portions of the resource that are economically viable by underground mining is in progress.
Riverina has an open pit reserve of 1.4 Mt @1.8g/t Au for 81,000 ounces. OBM said that additional deep drilling is planned for Riverina Main lode aimed at upgrading the resource categories and to define extensions down plunge to the south. The company reported that the environmental studies required for the mining approval process are also advancing.
The company said that further work would include infill and extensional drilling at Riverina Main lodes, mining appraisal studies, and assessment of all regional data to develop new exploration targets.
Ora Banda Managing Director David Quinlivan said: “This underground Resource upgrade for Riverina supplements the already substantial resource base that we have defined in this area.
The mineralisation remains open along strike, down-dip and downplunge and we remain keen to systematically test these areas.”