YENEENA (100% Encounter)
Yeneena covers a 1,800km2 tenement package in the Paterson Province of WA located between the Nifty copper mine, the Woodie Woodie manganese mine, the Telfer gold-copper mine and the Kintyre uranium deposit (Figure 1).
Figure 1: Yeneena project leasing and target areas with major regional faults
The BM7 prospect is located at the intersection of the north-east trending Queen Fault and a NNW to NNE trending Windsor fault that splays off the regionally-extensive McKay Fault (Figure 1). A 6km long and up to 3km wide copper regolith anomaly outlines the BM7 system that is also coincident with a broad area of electrically resistive geology.
Diamond drilling at BM7 has been primarily focused on the western side of the regolith anomaly in the zone of most resistive geology. The broad spaced diamond drilling has defined a gently east-dipping sequence of interbedded carbonates and carbonaceous to calcareous shales.
All diamond holes drilled along this western margin have intersected zones of disseminated copper sulphide mineralisation. The strongest mineralisation to date has been intersected in the northern half of the BM7 system in EPT1719 (5.3m @ 2.5% Cu from 387.6m including 0.7m @ 10.7% Cu from 388.6m). (Reported pursuant to the 2004 Edition of the JORC Code - refer ASX announcement 22 October2013)
During the September 2014 quarter a single diamond hole was drilled at BM7, collared 400m north of EPT1719 (Figure 2). This hole, EPT2158, intersected an anomalously thick package of carbonate stratigraphy containing bands of carbonaceous shale. Copper sulphide mineralisation was noted over a broad interval downhole, with stronger mineralised zones occurring at the margins of the carbonate bodies, including a narrow vein of massive chalcopyrite mineralisation at ~250m (Photo 1 - refer ASX release 31 October 2014).
Figure 2: BM7 Diamond drilling status plan over interpreted geology
Photo 1: EPT 2158 - 250.4m to 250.7m assays 8.9% copper
The low grade copper sulphide mineralisation and phosphorous anomalism (proxy for apatite alteration) appear to strengthen from west to east in the northern half of BM7, in the area around drill holes EPT1717 and EPT2158. This alteration within the host carbonate stratigraphy provides a vector to the east towards an interpreted steep NW trending structure. It is interpreted that this NW trending structure is the primary fluid conduit to the BM7 system and is therefore likely to be more proximal to the high grade mineralisation.
Figure 3: Interpreted cross section 7539700mN through BM7
BM7 East Prospect
The BM7 East Prospect was identified in 2013 during wide-spaced aircore drilling east of the BM7 Prospect. An RC drill program over BM7 East was completed in September 2014.
Fe-Mg carbonate (siderite) and phosphorus alteration halos (apatite), that are proximal alteration signatures to the Nifty hypogene high grade mineralisation, are found in high concentrations at BM7 East. The alteration halos underlie the core of a laterally extensive copper oxide blanket found at BM7 East that extends over 2km in strike (see Figure 4).
RC drilling in the September 2014 quarter also identified primary copper sulphide (chalcopyrite) in one of the eastern RC holes (EPT1879) adding further support to the interpretation that the extensive regolith copper anomalism results from the direct weathering/oxidation of a body, or bodies of copper sulphide mineralisation.
Figure 4: Plan view of alteration and mineralisation through BM7 East - background image Ch40 VTEM
Figure 5: Interpreted section through BM7 East
The alteration and mineralisation intersected in the shallow drilling completed at BM7 East is similar to what is seen in the immediate hangingwall of the Nifty copper deposit.
BM6, located 3km NNE of BM1 Northern Area, was discovered during reconnaissance aircore drilling in 2011 which delineated an 800m long, 400m wide +0.1% copper regolith anomaly, adjacent to the Windsor fault (with grades up to 1.4% Cu). The regolith anomaly coincides with a VTEM conductor, which has been modelled to dip shallowly to the west (towards the Windsor Fault). Common pathfinder elements to sediment hosted copper mineralisation are elevated at BM6, with Bi assays up to 74 ppm and Mo assays up to 17 ppm (similar to levels seen at BM1 and BM7).
A two hole RC drill program drilled in 2013 defined a shallowing of the base of oxidation above a block of conductive shale. It is interpreted that this block of shale is more resistant to weathering as a result of localised silica alteration of the shale. The RC holes also intersected elevated copper anomalism and siderite alteration below the base of oxidation, which is considered highly anomalous.
The siderite alteration and phosphorous anomalism at BM6 sits below the base of oxidation within carbonaceous and dolomitic shales and can be traced over 2km of strike. The alteration halo is coincident with a broad and extensive hypogene Cu anomaly that was intersected in drill hole EPT1691 (178m @ 400ppm from 72m). This association is similar to the geochemical signature of the hangingwall shale at Nifty.
Additional RC drilling is required at BM6 to test the volume from 150m to 250m depth from the surface in order to delineate the extents of the copper and siderite alteration halos. The successful delineation of a strengthening alteration halo at BM6 will provide a vector toward primary high grade copper sulphides.
Figure 6: BM6 Prospect drill status plan over Ch35 VTEM image
The Millennium prospect is situated on the margin of an interpreted sedimentary sub-basin at the intersection with the regionally significant Tabletop Fault (see Figure 7). Encounter completed a program of shallow RC drilling across Millennium in September 2014 that confirmed extensive low grade zinc-lead sulphide mineralisation at the target, with many holes ending in mineralisation (see ASX announcement 15 October 2014).
Subsequently, four diamond holes (EPT2194, EPT2195, EPT2196 and EPT2198) were completed at Millennium in 2014 to test for mineralisation at depth and along key geological contacts. These holes were drilled on a single north-south section across the target. All four holes drilled intersected visible zinc sulphide mineralisation in the form of sphalerite (see ASX announcement 27 November 2014).
Diamond drilling at Millennium has identified two distinct styles of zinc sulphide mineralisation and has defined compelling follow up drill targets. The presence of multiple styles of zinc mineralisation and the large mineralisation footprint indicates a significant zinc mineralising event at Millennium.
Figure 7: Millennium prospect - Location, Interpreted structures and EM Plan
The initial three hole diamond drill program at Millennium in 2015 which was expanded to five holes has now been completed. The program demonstrated that the targeted zone has a significant thickness with continuous and consistent geometry (see Figure 10). Drill holes EPT2201 and EPT2203 (Figure 8) intersected broad zones of gossan with highly elevated zinc anomalism (see ASX Announcement 17 June 2015). These intersections included a number of voids and significant core loss. Assays have confirmed that highly anomalous zinc mineralisation is contained within these zones which supports the interpretation that they are likely to have formed by the oxidation of primary zinc sulphide mineralisation and that the targeted zone may transition at depth into a significant body of zinc sulphide mineralisation and that the targeted zone may transition at depth into a significant body of zinc sulphide mineralisation. Intersections from these holes include;
- EPT2203 - 91.8m @ 1.6% Zn from 344.4m incl.
- 26.3m @ 2.1% Zn from 345.1m
- EPT2201 - 38.7m @ 0.9% Zn from 255.8m incl.
- 8.6m @ 2.2% Zn from 285.9m
(see ASX announcement 9 July 2015).
The gossan zone intersected at Millennium has been preferentially oxidised down to a depth of approximately 400m from surface. EPT1854, located approximately 250 north-west and along strike of EPT2201 and EPT2203, intersected narrow zones of brecciated and laminated massive zinc sulphide mineralisation at a similar depth which returned assays of 0.7m @ 36.5% Zn and 37g/t silver (see ASX 13 announcement December 2013). The sulphide intersection in EPT1854 may be representative of the primary precursor zone to the gossan intersected in EPT2201 and 2203. Its occurrence at similar depths to that of the gossan in EPT2203 indicates the potential for accumulations of high-grade zinc sulphide within 500m of the surface at Millennium.
This interpretation is supported by the occurrence of transitional sulphides near the base of the gossan intersected in EPT2203, interpreted to be close to the sulphide interface. The boundary between oxide and sulphide mineralization is expected to vary along strike at Millennium. This variation ranges from significant sulphide mineralisation intersected within 200m from surface in the south-east of the prospect in EPT2198, to preferential weathering up to 400m from surface in EPT2203 in the north-west.
The final hole of the current program, EPT2206, was drilled 200m directly down dip of EPT2203 (Figure 10) to target a possible steep plunging continuation of the mineralised zone. This hole intersected a deformation zone / fluid conduit with alteration similar to that in EPT1854 but intersected only traces of disseminated zinc sulphides. Accordingly, it is interpreted that the mineralised shoot intersected in EPT2201 and EPT2203 has a shallow south-east plunge, and EPT2206 has drilled beneath the plunging shoot (see Figure 9 long section).
Following the receipt of the remaining chemical assays, completion of petrology reports and rock property testing from the five completed holes at Millennium, a follow up drill program will be designed.
Consideration is being given to various surface exploration technologies that may assist in the delineation of the depth of weathering and orientation of a mineralised shoot. It is possible in this environment that seismic imaging could map the mineralised unit to depth and along strike. In addition, we are assessing the use of a large capacity RC drill rig to complete a systematic drill test of the +3km long zinc system to define the extent of the mineralised shoots identified at Millennium.
Figure 8: Diamond drilling collar location - Millennium
Figure 9: Diamond drilling long section (B - B') - Millennium
Figure 10: Cross Section 389150mE (A-A') - Millennium
Fishhook Copper Project (E45/2658 and E45/2806 - Encounter 100%)
The success of the copper exploration program at the Yeneena project and the discovery of a large copper-cobalt mineral system at BM1-BM7 has encouraged Encounter to expand its activities over untested regional copper targets.
The Fishhook project covers an area of over 100km2 and located approximately 20km north of BM1-BM7 (see Figure 11). The project is predominantly sand covered (typically 2-10m) with limited outcrop. Beneath this sand cover lies the prospective Broadhurst Formation, the host to mineralisation at the BM1-BM7 prospects and the Nifty Copper Deposit, which is located 45km to the north of Fishhook.
Encounter conducted a systematic, broad spaced 7,500m regional AC drilling program over the Fishhook project. The AC program highlighted a number of areas of interest and two follow up diamond drill holes were subsequently completed for a total of 865m at the Moby Dick and Orca targets. Both drill holes, spaced 5km apart, intersected copper sulphides hosted within a sequence of highly-oxidised "red rock altered" sandstones and shales and zones of sericite altered shales/dolomites and exhibiting key elements of the sediment hosted copper model in a traditional Central-African copper belt setting. At Fishhook, the Broadhurst sediments are in close proximity to the underlying thickened sandstone sequence and have undergone extensive red-rock alteration. Mineralisation appears to be concentrated along more reduced horizons within the sequence which provides a focus for the copper mineralisation.
The results have positive implications for the Fishhook project and opens up the potential for further sediment hosted copper occurrences along the northern corridor.
Figure 11: Yeneena project leasing over Ch35 VTEM image
Figure 12: Fishhook Project - Moby Dick and Orca prospects
Lookout Rocks / Throssel Range Project
(E45/3768, E45/4091, E45/4408 and E45/4230 - 100% Encounter)
A 560 line km airborne VTEM survey covering the area NW of Fishhook was completed in April 2014. The interpretation indicates the prospective structures and Broadhurst lithologies extend a further 30km northwest from the Fishhook Project into ground that is now held 100% by Encounter.
Historical exploration along the project is limited to a shallow RAB drilling program completed in the 1980s that intersected anomalous copper oxide mineralisation at the Lookout Rocks prospect (see Figure 14). This virtually unexplored region has many characteristics of a region that could host a significant Central-African style Cu deposit. The proximity to both the Coolbro Sandstone (underlying the Broadhurst Formation) to the east, and the Pilbara Craton to the west indicates there are significant basin-forming structures and potential pathways for fluid migration. Importantly, NE-trending structures that extend SW from the Nifty copper deposit cross-cut the major basin-forming faults within the project (see Figure 13).