Geophysics and Drilling Collaborations Program 2020 Epenarra, Tennant East Project Final Report

Abstract

King River Resources (KRR) applied for and was awarded in round 13 of the 2020 Geophysics and Drilling and Collaboration at its Epenarra Project within the Tennant East Region. The proposed programme involved a ground passive seismic survey over EL 31633 and EL 31634 to assess the depth of Cambrian cover followed by a region scale (433km2) and detailed airborne magnetic survey to assess the nature of basement and the nature of any targets beneath the basin sediments. The target mineralisation is for Iron oxide copper gold deposits with magnetic signatures associated with ironstone, most likely Tennant Creek style. KRR tenements in the NT are held by Treasure Creek Pty Ltd which is a wholly owned subsidiary of King River Resources Limited ('Company'), an ASX listed public company (ASX: KRR). The tenements are within the East Tennant Area of the recent government 'Exploring For The Future' initiative. The tenements have only been covered by semi-regional geophysical surveys data which includes 200m line spaced air borne magnetics flown in 1999 and wide spaced 4km spaced gravity and regional AUSAEM and MT (AUSLAMP). There is no other exploration over the tenement except a RAB drill programme in the western most edge of EL 31634 where only one hole penetrated the Cambrian cover. It is interpreted that the +25km magnetic bodies beneath the Cambrian cover are related to Palaeoproterozoic rocks equivalent in age to the Warramunga Formation which is the main hosting stratigraphy for IOCG deposits at Tennant Creek. The depth of Cambrian cover is expected to be between 80 and 200m. The programmes were successfully completed with the detailed airborne magnetic survey over the whole of EL 31633 (100m line spacing, 30m survey height) totalling 4,336 line km and 5 Passive Seismic lines completed over EL 31633 and EL 31634 (10-20km line spacing, 500m stations) totalling 170 stations (182 total but some removed due to noise). The detailed airborne magnetics provided excellent resolution of the area. The work has much more clearly defined the contrast of the main magnetic body (lensoidal complex approx 20km strike) and the surrounding granites and internal positions and structures to this higher magnetic zone. Interpretation is still that the large higher magnetic zone is a raft of Warramunga Formation equivalent units surrounded by granite. It is hoped that some of these magnetic high zones are influenced by ironstone/IOCG bodies. The nature and positions of the targets identified in the 2020 application document are much more defined and details within higher zones are now evident with anomalies as small as 100-250m standing out. Overall, the passive seismic work appears to have provided an excellent model for the base of Cambrian cover. Estimated depths range from 80 to 150m with depths varying possibly due to palaeo-topography and faulting. Interpreted depth of cover estimates from the government AusEM 2017-2018 tempest EM conductivity sections are overall similar to the depth estimates given by the passive seismic work which gives more confidence. Also, the magnetic depth estimations give similar depth ranges overall but seem to be overestimating and varying more. Passive seismic surveys are a cheap and easy alternative to other more expensive and intensive methods of estimating basin depth. The collaboration work (airborne magnetic and passive seismic surveys) has assisted with regional geological understanding of the area (more understanding of the depth and nature of the Cambrian cover and basement contact), understanding methodologies for estimating Cambrian cover depth and King River Resources exploration/target prioritising on EL 31633/31634 and their surrounding tenements.