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Location: 120 km W from Norseman, Western Australia, Australia
Level 1, 3 Ord Street, West PerthPO Box 190, 6872PerthWestern Australia, Australia6005
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The surface geology at Emily Ann is totally obscured by transported sediments and a thick saprolite profile extends down to about 80 m below the surface. The deposit occurs in a complex geological setting, consisting dominantly of felsic volcaniclastics hosting subordinate discontinuous lenses of mineralised and barren ultramafics, which dip at between 40° and 60° to the east in the vicinity of the deposit. The ultramafics and associated nickel-sulphide mineralisation do not extend to the bedrock surface and are therefore totally blind. The deposit has been subdivided into two main mineralised structural domains, termed the upper mineralised horizon (UMH) and lower mineralised horizon (LMH).The UMH has a strike extent of about 520 m and down-dip extent of up to 150 m. The mineralisation is highly variable and consists dominantly of disseminated to matrix pyrrhotitepentlandite and lesser stringer and massive sulphides. The proportion of massive sulphides increases downwards towards the boundary mylonite. The mineralisation in the LMH is of greater economic significance and consists of lenses of high tenor (8-14% Ni) massive nickel sulphides (pyrrhotite-pentlandite) distributed over a strike length of about 520 m and with a down-dip extent of about 270 m.The Maggie Hays deposit is blind, with the top of the main disseminated sulphide zone commencing at a depth of about 200 m beneath the surface and the massive sulphides at a depth of about 350 m beneath the surface, as shown in the cross section along 82700N.The main zone of the deposit is located at the base of the CUU in association with olivine orthocumulate and mesocumulate lithologies that have subvertical dips to the east and west. Structurally, the zone occurs at a local pinch out in the CUU against stratigraphically overlying BIF (to the west) and underlying felsic volcanics (to the east). The structural termination is controlled by an early thrust, which dips at about 50° to the east and plunges at about 45° to the south, thereby terminating the main zone of the deposit at depth. A second lower grade portion of the deposit, known as the southern zone, occurs several hundred metres to the south. The Maggie Hays North zone of the deposit is controlled by the same thrust, with the mineralisation totally hosted.Main Zone:• Located at the base of the CUU with the bulk of the deposit located between 200 and 500 vertical metres beneath the surface and over a strike extent of 600 m.• Basal massive sulphide zone of 4-6% Ni, located towards the lower (down-dip) margin of the disseminated zone and the northern structural termination of the ultramafic.Northern Zone:• Hosted entirely by felsic volcanics with the mineralisation controlled by an early thrust fault. The zone dips at about 50° to the east and has a strike extent of about 800 m.• Massive, stringers and breccia sulphides. The sulphides form as a matrix to felsic clasts.Southern Zone:• Located several hundreds of metres to the south of the main deposit in high-magnesium ultramafics.• Up to 10% disseminated sulphides, similar to the main disseminated zone.ExplorationStudies on the Maggie Hays deposit at Emily Ann indicate both deposits were emplaced within a felsic volcanic sequence by a series of intrusive ultramafic magmas that collectively form the Central Ultramafic Unit (CUU). The CUU and felsic volcanic sequence are capped by a regionally persistent banded iron formation (BIF). The intrusive emplacement model for the deposits was confimred by the discovery of significant nickel sulphide mineralisation within an interpreted narrow feeder zone to the Emily Ann deposit at Abi Rose (refer to Poseidon ASX announcements “More Nickel Sulphides Intersected at Abi Rose” dated 22 November 2018 and “Significant High Grade Nickel Intersection at Emily Ann North” dated 25 January 2016).The Western Ultra Mafic Unit (WUU) overlies the regionally persistent BIF sequence and is interpreted to have been emplaced as a series of extruded ultramafic flows by the CUU magmas breaching through the BIF sequence. The basal contact of the WUU is considered a high priority target for potential economic nickel sulphide mineralisation that has historically been overlooked.
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