Round 17 - Geophysics and Drilling Collaborations program Greenfields drilling EL 32109

Abstract

The target in the Barkly area is primarily Tier 1 IOCG deposits within the Proterozoic basement beneath Georgina Basin cover. Previous drilling on BOPL's and neighbouring tenements is sparse. Studies under the NTGS and Federal-EFTF-initiative, followed by the MinEx CRC and competitor exploration drilling campaigns has demonstrated the prospectivity of the Proterozoic basement for IOCG-hosted styles of mineralisation. BOPL's EL 32109 covers a large area highlighted by Geoscience Australia (Skirrow et al, 2019) as most prospective for IOCG deposits on the East Tennant Ridge. Priority drill-targets were confirmed in EL 32109 as part of a broader targeting program that identified 55 exploration targets. The targeting considered prospectivity based on deposit conceptual model parameters evidenced by magnetic, gravity and structural model signatures. Three priority target areas were identified in EL 32109 comprising magnetic and/or gravity anomalies situated adjacent to the Gulunguru Fault (a deep crustal fault with interpreted multiple stages of extension and reactivation along which magnetitic and gravity anomalies - probable magnetic and/or hematite constructive alteration zones, are distributed). Detailed infill gravity surveys (100 x 100m stations) and 3D inversion models were completed to constrain the targets and drillhole locations. Ten 'shoots' with geometries and densities that may reflect IOCG style mineralisation were identified from 3D gravity models. The drill target centres were modelled as deep, ranging from 445 to 900 metres in depth. The proposed grant funded drillholes tested a separate target in each prospect foremost aiming to intersect economic mineralisation while also providing depth to basement data, basement lithology, alteration, geochemistry and petrophysical data to support further modelling and prioritise further drilling. Deep (600-800m) drillholes were required to test the anomalies. Two of the three planned holes were completed without issue at the Pebble and Dino prospects. A third hole was commenced at the Wilma Prospect but drilling was suspended due to safety concerns upon encountering unforeseen geology in the RC pre-collar (gas emitting from the pre-collar in the cover sequence stratigraphy). A total of 1326.48m were drilled, with a breakdown of 470.9m of RC and 855.58m of DD No economic visible sulphides were recorded in the holes in the basement IOCG target stratigraphy. Trace copper sulphides and alteration dispersed in the first hole at the large Pebbles prospect was recorded and considered significant. The target at the Wilma Prospect remains valid but is subject to reassessment of our approach to drilling and that target. While the regional stratigraphy and observed alteration style were consistent the primary ICOG target models, however, the two completed holes did not intersect rocks with densities that explain the gravity targets. Data from the holes can now be used to critically help constrain forward models for future drill targeting. Both diamond holes interestingly also intersected, narrow intervals of trace lead or zinc sulphides which were recorded in fractured and vughy carbonates in the overlaying Georgina Basin cover sequence. Adding significant support to postulated presence of new exploration possibilities in shallower target positions. The character and mineralogy of these zones is suggestive of Mississippi Valley Type (MVT) style base metal mineralisation.