The Central and Southern Corridors of the Springfield Project host zones of the prospective Narracoota Volcanic Formation, and are key exploration targets alongside Monty and Homer.
The Narracoota volcanic rock package is a highly prospective geological sequence which hosts Sandfire Resources’ DeGrussa VMS deposits, making it a key target for new VMS discoveries in the Doolgunna region. The Central Corridor and Southern Volcanics host extensive zones of Narracoota volcanics, and initial exploration work conducted by Talisman has returned very promising early results.
Figure 1 – Springfield Project simplified interpreted geology showing Prospect locations
Talisman completed three Reverse Circulation (RC) drill traverses over the Central Corridor in 2012 to test a prospective mafic-sediment contact at the southern margin of the corridor. It is interpreted that this horizon represents a stratigraphically equivalent position to the DeGrussa sequence on the southern limb of a major syncline and therefore has the potential to host VMS style copper-gold mineralisation.
Assay results from this drilling indicate anomalous copper sulphide, gold and malachite (secondary copper oxide) development associated with strongly altered and sheared mafic volcanic sediments and basalts, with coincident jasperoidal chert and magnetite development along the prospective horizon. Previous drilling also returned elevated anomalous copper sulphide occurrences along this position.
An updated geological interpretation of the Central Corridor was subsequently completed to identify key lithostructural controls on possible mineralisation. In addition, DHEM surveys on earlier drilling detected two late-time off-hole conductors along the prospective target horizon.
The Southern Volcanics are interpreted to comprise a wide sequence of prospective Narracoota basalts, volcanic sediments and dolerites in close proximity to the Goodin Fault Zone – a major basin boundary structure and possible focus for VMS and other copper (+/- gold) rich mineralising fluids. This area had received minimal historic exploration activity. Surface sampling work by Talisman and local prospectors has indicated that the volcanic sequence is highly anomalous in copper and gold.
An extensive detailed soil sampling program was completed across much of the western Southern Volcanic Corridor with the aim of identifying and delineating co-incident areas of anomalous copper and gold soil geochemistry. The soil sampling programme generated a significant copper-gold anomaly against a very low geochemical background at the Abraham Prospect (see Figure 2).
Figure 2 – Springfield Project Geology showing Prospect locations
An initial reconnaissance 3,000m RC drilling program was completed at the Abraham Prospect during 2013 to test these new geochemical target areas. Drilling intersected strongly altered dolerites, basalts and, importantly, coarse volcanic sediments that may have the potential to host VMS-style mineralisation. Assay results for the first-pass RC drilling returned two zones of broad low level copper anomalism associated mafic volcanic-volcaniclastic sediment contact zones.
In addition to the Abraham RC drilling, an extensive reconnaissance geochemical Aircore drilling program was completed over the eastern extension of the Southern Volcanics that was designed to test for base metal and gold anomalism under extensive alluvial cover (see Figure 3).
Figure 3 – Eastern Southern Volcanics showing geochemical drilling results with anomalous Cu contours at the Kink Prospect
The Aircore drilling program went across a major cross-cutting NW transfer fault zone that is interpreted to traverse the Springfield Project and link-up with the DeGrussa copper-gold deposit. The reconnaissance geochemical drilling programme returned highly encouraging results, defining a significant coherent north-west trending zone of elevated copper and gold anomalism. (see Figure 3).
A Versatile Time Domain Electromagnetic (VTEM) Survey was then completed to test for near-surface conductors across the Southern Volcanic sequence, with the aim of defining possible drill targets associated with geochemical anomalies and to provide data for geological interpretation.
Figure 4 – Springfield Project showing geochemical contours and VTEM anomalies at the Southern Volcanics
Three EM anomalies were identified at The Kink Prospect (see Figure 4) with late-time conductive responses. RC drilling detected no massive sulphide mineralisation in the first two of these VTEM anomalies, with the third anomaly yet to be drill tested.
Several mid-to late-time VTEM anomalies were also identified at the Wedge Prospect (see Figure 4) which were coincident with coherent zones of elevated surface copper geochemistry along the Goodin Fault Zone. Nine angled RC drill holes were drilled at the Wedge during 2013 on three traverses to test four geochemical targets comprising elevated copper, gold and zinc values in earlier surface lag and soil sampling data.
The drilling intersected sheared mafic volcanics, dolerite, intercalated siltstone, shale and jasperoidal chert horizons with variable quartz veining throughout. Several broad zones of elevated copper and a minor gold mineralised interval were intersected. These zones of mineralisation were associated with trace copper and iron sulphides and quartz veining in altered mafic rocks.