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Nova-Bollinger: A Brief History
Nova-Bollinger Ni-Cu Deposit: Introduction
Below is an introduction to the discovery of the Nova-Bollinger Ni-Cu Deposit.
Geochemical mapping of the Fraser Range region was undertaken by the Geological Survey of Western Australia (a Division of the Government of Western Australia Department of Mines and Petroleum)(“GSWA”) in September 1998 with samples collected at a nominal density of one per 16km2 with the results published in October 2000. The one sample collected proximal to the Nova-Bollinger Nickel-Copper Deposit (SampleID 163201_C1M3SD3 located at 6480335mN 518654mE) assayed 271ppm Ni, 90ppm Cu and 39ppm Co (“GSWA anomaly”).
Sirius Resources NL (ASX: SIR)(“Sirius”) obtained a 70% interest in the base metals rights in Exploration Licence E28/1724 containing the GSWA anomaly from Mark Creasy, announced to the Australian Stock Exchange (“ASX”) on 9 June 2009 with the transaction approved by shareholders on 17 August 2009. The base metal rights were converted to a 70% interest in all mineral rights as part of an agreement to acquire tenements prospective for gold in the Fraser Range from Mark Creasy, announced to the ASX on 21 October 2010 with the transaction approved by shareholders on 17 December 2010. At the time Mark Creasy (through Ponton Minerals Pty Ltd) retained the other 30% interest in the project area as a free carried interest to a decision to mine following completion of a positive feasibility study.
In November 2010 Sirius completed a 200m x 80m soil sampling programme over a 4km long southwest-northeast orientated oval shaped airborne magnetic feature (identified from Government data in the public domain) and the GSWA anomaly located on its western edge. The magnetic feature because of its eye-like appearance has been colloquially called the “Eye” (see Figure 1) with the core of the Eye interpreted at the time to be a dome or plug of ultramafic rocks or a layered mafic-ultramafic intrusion.
Figure 1: The Nova-Bollinger Ni-Cu Deposit Eye (Sirius ASX Announcement 11/05/2011 – Presentation to Sydney Resources Roundup conference)
The results of the soil sampling identified a 2km x 1km Ni-Cu-Co anomaly peaking at 568ppm Ni and 303ppm Cu (see Figure 2).
Figure 2: Coincident nickel and copper in soil sampling over “eye” shaped magnetic feature at Fraser Range (Sirius ASX Announcement 22/03/2011 – Exploration Update)
In September 2011 a traverse (located along 6479800mN) of six RC drill holes was completed across the Ni-Cu-Co anomaly to determine preferred locations for a follow-up diamond drill hole to be co-funded by the Government of Western Australia. Fine grained disseminated sulphides including chalcopyrite, pyrrhotite and pentlandite were identified in the regolith overlying metagabbro/gabbronorite bedrock (see Figure 3). The stratigraphic diamond drill hole tail was completed off the most eastern RC drill hole in October 2011.
Figure 3: Cross section 6479800N showing strong Ni, Cu and Co enrichment in the weathering zone, open east and west (Sirius ASX Announcement 25/10/2011 – Nickel-copper-cobalt in first drilling at the Eye prospect)
In May 2012 a RAB/aircore drilling programme together with a ground moving loop electromagnetic survey (“MLEM”) was completed to delineate targets at depth for drill testing. The RAB/aircore drilling consisted of 120 holes on 400m line spacings and 160m or 80m hole spacings drilled to the base of the regolith over the eye shaped airborne magnetic feature. The drilling programme identified a broad area of lateritic nickel-cobalt enrichment and several holes intersected significant (0.5 to 1.0% Ni) nickel-copper mineralisation at or near to the end of hole suggesting that some of the nickel in the laterite may have been derived from the oxidation of primary magmatic sulphides rather than just through the weathering enrichment of ultramafic rocks (see Figure 4).
The MLEM survey was completed on 400m line spacings and 100m station spacings and identified three bedrock conductors located around the edge of the Eye (see Figure 46). Conductor 1 on the western edge of the Eye was the strongest in late time channels (indicating a highly conductive zone) and was modelled as a body with a strike length of 200m that extended for a distance of 1,000m to the northeast down plunge. The conductor commenced at a depth of 50m below surface and plunged 200 to 300m beneath the previous RC drilling and RAB/aircore drilling. The three conductors were confirmed by a ground fixed loop electromagnetic survey and more accurate modelling of their position and orientation was completed to optimise the design of the drilling planned to test them.
Figure 4: The Eye, showing key nickel intersections together with the location of identified EM anomalies (Sirius ASX Announcement 10/05/2012 – Nickel-copper in drilling at the Eye, Fraser Range)
On 26 July 2012 Sirius announced the discovery of significant nickel and copper mineralisation in the first RC drill hole (SFRC0024 located at 6479500mN 518210mE, dip 60 degrees & azimuth 270 degrees) testing the midpoint of the top portion of Conductor 1. At 191m down hole drilling intersected 4m of breccia and massive sulphides assaying 3.8%Ni and 1.42%Cu, the Nova-Bollinger Ni-Cu Deposit was discovered (see Figure 5).
Figure 5: Discovery hole SFRC0024 at the Nova-Bollinger Ni-Cu Deposit, Saturday 21st July 2012. Note the run of darker grey samples (with disseminated sulphide) culminating in the black samples (matrix to massive sulphide). (Sirius ASX Announcement 26/07/2012 – Major nickel-copper discovery defines new province)
On 28 February 2013 Sirius announced the discovery of a thick new zone of sulphide mineralisation in hole SFRD0167 located approximately 200m east of the Nova deposit and named Bollinger. The hole was drilled to test a large gravity anomaly defined in a recent gravity survey, the centre of which is situated in the centre of the Eye to the east of the discovery hole.
Figure 6: Gravity map of the Eye showing the location of the new drillholes in relation to the Bollinger discovery hole. (Sirius ASX Announcement 6/03/2013 – Drilling at Bollinger confirms potential scale)
The Nova-Bollinger Ni-Cu Deposit is considered to be a magmatic nickel sulphide deposit with the sulphides thought to have accumulated by gravitational settling processes related to the magma flow. The Nova-Bollinger nickel-copper mineralisation occurs as disseminated and massive sulphides. The sulphides consist of 80-85% pyrrhotite, 10-15% pentlandite and 5-10% chalcopyrite.
