Diamond Drilling at Emu and Southwark Deposits Reveals Gold and Silver Continuity at Depth
Bottle Creek Diamond Drilling Reveals Gold and Silver at Depth
- Results from the 14 diamond drillholes at Emu and Southwark reveal gold and silver continuity at depth
- Significant intercepts include:
o 16m @ 5.3 g/t Au, 25.1 g/t Ag from 61m
o 15m @ 4.2 g/t Au, 11.2 g/t Ag from 53m
o 4m @ 10.8 g/t Au, 5.9 g/t Ag from 43m
o 6m @ 8.3 g/t Au, 9.2 g/t Ag from 86m
o 4.6m @ 5.5 g/t Au, 7.9 g/t Ag from 101m
o 6m @ 2.6 g/t Au, 4.8 g/t Ag from 54m
o 4.3m @ 2.1 g/t Au, 26.4 g/t Ag from 193m
o 4m @ 2.7 g/t Au, 30.3 g/t Ag from 86.5m
o 13.7m @ 1.1 g/t Au, 14.6 g/t Ag from 137.3m
o 6.3m @ 1.3 g/t Au, 72.8 g/t Ag from 81.7m
o 4.5m @ 144.4 g/t Ag from 96.5m, including 2m @ 280 g/t Ag
o 3m @ 4.2 g/t Au, 147 g/t Ag from 96.5m, including 1.3m @ 9.7 g/t Au, 340 g/t Ag from 96.5m
- Broad high grade gold intercepts extend downhole mineralisation encountered in previous RC holes
- Gold and silver mineralisation remains open at depth
At Emu, assays for drillholes EMDD001 to EMDD004, and diamond tails EMRCDD014, 080 and 092 give results up to 19.1 g/t Au(see Note 1 below) and 465 g/t Ag(see Note 2 below). Broad intercepts include 16m @ 5.3 g/t Au and 25 g/t Ag(see Note 3 below). Significant results are listed in Table 1(see link below). Mineralisation is dominantly hosted in the Emu Formation, comprising interbedded black shales, banded iron formations and carbonaceous cherts. The chemically reducing nature of this sedimentary package, in contrast to the surrounding mafic volcanics and felsic intrusives, is considered to be a key factor in the deposition of gold and other metals during the mineralisation event.
Gold + silver mineralisation at Emu occurs within a pyrite-dominated (+ pyrrhotite + arsenopyrite) assemblage. Silver mineralisation occurs in association with gold, however some zoning to mineralised zones is apparent, with elevated silver grades occurring on the margins of mineralised zones, and higher-grade gold occurring within the cores of these zones.
Significant intercepts from diamond drilling at Emu are listed in Table 1 (see link below) and include:
o EMDD001: 4.3m @ 2.1 g/t Au, 26.4 g/t Ag from 193m
o EMDD002_1: 15.05m @ 4.22 g/t Au, 11.17 g/t Ag from 53.3m
-- including: 1.35m @ 10.25 g/t Au, 3.0 g/t Ag from 53.65
-- and including: 1.8m @ 10.60 g/t Au, 18.9 g/t Ag from 64.5m
o EMDD003: 4m @ 10.82 g/t Au, 5.9 g/t Ag from 43m
-- and: 6m @ 2.66 g/t Au, 4.8 g/t Ag from 54m
o EMDD004: 16m @ 5.34 g/t Au, 25.12 g/t Ag from 61m
-- including: 4m @ 58.5 g/t Ag from 61m
-- and including: 3m @ 15.27 g/t Au, 17.63 g/t Ag from 65m
o EMRCDD014: 6m @ 8.3 g/t Au, 9.2 g/t Ag from 86m
o EMRCDD080: 4.6m @ 5.5 g/t Au, 7.9 g/t Ag from 101m
o EMRCDD092: 4.5m @ 144.4 g/t Ag from 96.5m
-- including: 2.1m @ 280 g/t Ag from 97.5m
-- and including: 1.1m @ 1.1 g/t Au, 112 g/t Ag from 98.5m
EMDD002 was originally drilled to 171.9m, however encountered difficult drilling conditions within the mineralised zone between 50 and 70m downhole. To ensure this zone was tested properly, a twin hole, EMDD002_1, was drilled 0.5m southwest of the original hole, and successfully drilled through the mineralised zone with good recoveries. The location of EMDD001, 002 and 002_1 are shown in Figure 1(see link below).
Diamond drilling at Southwark included drillholes SWKDD001 and 002, with diamond tails SWKRCDD014, 016, 018 and 034. Assays from these drillholes give results up to 9.66 g/t Au and 493 g/t Ag(see Note 4 below). Broad intercepts include 13.7m @ 1.1 g/t Au and 14.6 g/t Ag(see Note 5 below). Intercepts which extend previously drilled zones in RC holes include 17m @ 3.47 g/t Au, 37.2 g/t Ag(see Note 6 below), which extends the original RC intercept by 8m downhole. Significant results are listed in Table 1(see link below).
As at Emu, Southwark mineralisation is dominantly hosted in the Emu Formation, within the broad, high strain Mt Ida Shear Zone.
Mineralisation at Southwark is generally found to have the same style as at Emu; that of disseminated pyrite and arsenopyrite within the carbonaceous Emu Formation. However several intervals of massive sulphide were intersected, occurring on the boundary between the felsic porphyry intrusive and the Emu Formation sediments. These intervals are up to 10m thick. An example is shown in Figure 2(see link below). Assays from this zone returned up to 3.5 g/t Au, 13.6 g/t Ag and 0.2 % Zn(see Note 7 below).
The massive sulphide zone contains dominantly pyrite, with minor occurrences of sphalerite (ZnS), various Cu-bearing phases and galena (PbS). A description of petrographic analysis of a similar sample is given below, with photomicrographs in Figure 5(see link below).
Significant intercepts from diamond drilling at Southwark are listed in Table 1(see link below), and include:
o SWKDD002: 3.1m @ 4.24 g/t Au, 146.76 g/t Ag from 96.5m
-- including: 1.25m @ 9.66 g/t Au, 340 g/t Ag from 96.5m
-- and: 5.5m @ 1.03 g/t Au, 124 g/t Ag from 102.5m
-- and: 1.3m @ 154 g/t Ag from 110.4m
o SWKRCDD014: 6.3m @ 1.3 g/t Au, 72.8 g/t Ag from 81.7m
o SWKRCDD018: 4m @ 2.7 g/t Au, 30.3 g/t Ag from 86.5m
o SWKRCDD034: 13.7m @ 1.12 g/t Au, 14.62 g/t Ag from 137.3m
Intercepts for drillholes SWKRCDD014, 016 and 018 extended the previous RC drillholes which ended in mineralisation. Including the previously announced RC intercepts(see Note 8 below), the full intercepts in these holes are as below, with details given in Table 2(see link below):
o SWKRCDD014: 17m @ 3.47 g/t Au, 37.2 g/t Ag from 71m
o SWKRCDD016: 16.2m @ 8.98 g/t Au, 2.9 g/t Ag from 53m
o SWKRCDD018: 17.5m @ 5.36 g/t Au, 50.3 g/t Ag from 73m
Geological Model for Bottle Creek
Based on Alt's new diamond drilling at Southwark and Emu, a greater understanding of the structural and lithological controls on mineralisation can be derived. Based on our observations and analysis of the new diamond core, mineralisation at Bottle Creek has been introduced into the Emu Formation sediments along the crustal-scale Mt Ida Shear Zone. The Shear Zone forms part of a ~500km long boundary between the Eastern Goldfields Terrane and the Southern Cross Terrane.
A key component of the mineralisation model for Bottle Creek is the presence of the carbonaceous black shale (interbedded with carbonaceous chert, banded iron formation and minor volcanic units), named locally the Emu Formation. With the high component of carbon (as graphite) in these rocks, the Emu Formation creates a distinct zone of very reducing geochemical conditions along the Mt Ida Shear Zone, which is different to the surrounding mafic volcanic package and felsic intrusives. Metal-bearing fluids being transported along the Mt Ida Shear Zone would have encountered the strong change in geochemical conditions at the point where the shear zone intersected the Emu Formation, causing the metals (predominantly gold and silver) to precipitate from the mineralising fluid, and be deposited where we now see the Bottle Creek deposits.
A key exploration strategy for this area is to explore for carbonaceous shales along the Mt Ida Shear Zone. Carbon-rich shales show as a distinctive high in various electrical geophysical survey techniques. Alt is considering this option in its plans for regional exploration throughout the area.
To further our understanding of the geology, mineralisation style and timing of geological events at Bottle Creek, 13 samples of diamond core from Alt's new drilling at Bottle Creek were sent to Dr. Paul Ashley for petrographic analysis. The samples reveal that mineralisation may have been introduced as part of an early hydrothermal alteration event (influx of metal-bearing fluids into the rock; Figure 5, left) (see link below) that has subsequently been overprinted by regional metamorphism and deformation along the Mt Ida Shear Zone. Based on observations in the samples, Bottle Creek represents an orogenic gold system, with typical phyllic to propyllitic alteration assemblages which have been overprinted and changed during high temperature metamorphism. Supergene processes have subsequently concentrated gold, and depleted silver, within the oxidised zone near surface.
Whilst mineralisation dominantly occurs as disseminated pyrite and arsenopyrite in the black shales and carbonaceous cherts of the Emu Formation, several zones of massive sulphide (up to 10m wide) have been recognised in logging. Where present, the massive sulphide zones occur on the boundary between the felsic porphyry intrusive and the carbonaceous sediments of the Emu Formation. Petrographic analysis of the massive sulphide reveals an assemblage dominated by pyrite, but with minor aggregates of copper minerals, enargite (Cu3AsS4) and covellite (CuS) (Figure 5, right) (see link below). Elsewhere, microscopic occurrences of sphalerite (ZnS) and galena (PbS) have also been observed. Assays of samples through these zones do not return economic grades of copper, zinc or lead.
Regional Setting and Exploration History
The Bottle Creek gold mine lies 100 km north east of Menzies in the Mt Ida gold belt (see Figure 6 in link below). The gold mine is located on the northern extremity of the Mt Ida-Ularring greenstone belt extending from Davyhurst to Mt Alexander (see Figure 6 in link below). The Ularring greenstone belt forms the western part of the Norseman-Wiluna Province of the Yilgarn Craton. The location of mineralisation and local geology, is shown in Figure 7(see link below).
During historical operation from 1988-1989, 90,000 oz Au was produced from two open pits (Boags and VB; Figure 8)(see link below). Significant historical drilling along a 9.8 km strike outlined the Emu, Southwark and XXXX(see Note 9 below) deposits.
However these were never mined. The historical RC drill fences were spaced at 100m, with infill drill line spacing at 50m and 25m at various locations. The majority of drilling targeted oxide mineralisation and reached no deeper than 80m vertically below surface.
Alt's new drilling results continue to provide confirmation of historical intercepts, improve confidence in historical data, and proves the continuity and grade of mineralisation in key parts of the Emu deposit. Further, gold mineralisation appears to continue at depth, with several drillholes ending in mineralisation. Additional drillholes are being planned at Emu and other areas of the Bottle Creek Project to test the continuity of gold mineralisation at depth. RC drilling for resource definition is ongoing to advance updates to Alt's Bottle Creek resource of 109,500 oz Au, announced on the 16th August 2018.
1 From drillhole EMRCDD014, 87-88m downhole
2 From drillhole EMRCDD092, 97.5-98.5m downhole
3 From drillhole EMDD004, 61-77m downhole
4 Both assays from drillhole SWKD002; 9.66 g/t Au from 96.5-97.75m downhole, and 493 g/t Ag from 105.2-106m downhole
5 From SWKRCDD034, 137.3-151m downhole
6 From SWKRCDD014, 70-88m downhole. Original RC intercept was 71-80m, 9m @ 5.6 g/t Au (RC/DD intercept has 1.7m of no sample return between RC and DD changeover). See ARS announcement, 1st May 2018: http://www.abnnewswire.net/press/en/93014/
7 From SWKRCDD034, 148.5-149.4m downhole.
8 Results for SWKRC014, 016 and 018 were published on 1st May 2018: http://www.abnnewswire.net/press/en/93014/
9 Note that the XXXX deposit is now named 'Cascade'
To view tables and figures, please visit:
About Alt Resources Ltd
Alt Resources Limited (ASX:ARS) is an Australian based mineral exploration company that aims to become a gold producer by exploiting historical and new gold prospects across quality assets and to build value for shareholders. The Company's portfolio of assets includes the newly acquired Bottle Creek gold mine located in the Mt Ida gold belt in South Central WA 95km north west of Menzies, the Paupong IRG Au-Cu-Ag mineral system in the Lachlan Orogen NSW, Myalla polymetallic Au-Cu-Zn project east of Dalgety in NSW and the Mt Roberts gold project located near the town of Leinster in WA.
Alt Resources, having acquired historical and under-explored tenements in the Mt Ida Gold Belt, aims to consolidate the historical resources, mines and new gold targets identified within the region. Potential at Mt Ida exists for a centralised production facility to service multiple mines and to grow the Mt Ida Gold Belt project to be a sustainable and profitable mining operation.
Alt Resources Ltd