Maggie Hays Ni Mine, Lake Johnston, Norseman, Dundas Shire, Western Australia, Australiai

Regional Level Types
Maggie Hays Ni Mine	Mine
Lake Johnston	Lake
Norseman	Town
Dundas Shire	Shire
Western Australia	State
Australia	Country

The Maggie Hays nickel mine is approximately 150 kilometres west of Norseman, the nearest town to the mine.

A nickel anomaly was discovered here in 1971 by Union Miniere and Anaconda Resources, but they missed the main ore-body. This was discovered by Lionore Australia in 1996. Mining was started by Lionore in 2001, and later Norilsk who had taken over Lionore. Operations were suspended in 2009 due to low nickel prices, then recommenced in 2011. It is an underground mine.

The ore-body is found in the Lake Johnston Greenstone Belt. Within this is the Honman Formation. This is composed of five units. From lowest, is a felsic volcanic unit. Secondly, a transition zone, 50-75 metres thick, of volcanic and sedimentary rocks dominated by Fe rich silicates, abundant almandine, thin chert units, disseminated and stringer sulphides, and magnetite in the upper areas. Thirdly, a banded iron formation, averaging 120 metres thick, of alternating magnetite and chert. Fourthly, a sedimentary unit of quartz arenite, averaging 3.2 metres thick, with up to 10cm bands of almandine-grunerite, and sulphide rich rocks, with a sub-unit dominated by nodular pyrite, narrow pyrrhotite stringers, within a fine quartz matrix. Lastly, differentiated komatiitic flows of the Western Ultramafic Unit with massive sulphide at its base.

The Central Ultramafic Unit is an irregular sub-horizontal tube-like mass which cross-cuts the Honman Formation. It strikes south for 3.5 kilometres, with Maggie Hays found at its northern end where it is thickest. It is periodotite and dunite (olivine mesocumulate and adcumulate), and minor pyroxenite, containing up to 5cm xenoliths and patches of crystallised felsic melts.

The Jimberlana Dyke transects both the Maggie Hays and Emily Ann deposits. The formation of the deposits have been open to debate amongst geologists.

The Maggie Hays ore-body sits above a keel shaped, overturned sequence of komatiitic massive serpentinite ultramafic cumulates, with a remobilised low grade sulphide stringer zone. Further, there is a metamorphic developed olivine-anthophyllite-pyroxene assemblages, with retrograde metamorphic serpentinite-anthophyllite/cummingtonite-talc assemblages, with a zone of talc carbonation.

The ore-body strikes 1400 metres, is 2-6 metres of massive nickeliferous sulphide of banded and foliated pentlandite-pyrrhotite-pyrite. Dodecahedral pyrite crystals to 20cm have formed within the massive sulphide zone.

The ore-body is composed of a main zone of massive to disseminated sulphides, striking 800 metres, with the massive portion a tabular body striking 400 metres and up to 7 metres thick, at 3.79% Ni average. It is dominated by pyrrhotite with lesser pentlandite. Overlying this is disseminated sulphides below the base of oxidation, composed of pyrrhotite-pentlandite-pyrite-chalcopyrite. There is local supergene alteration of pentlandite and pyrrhotite to violarite and pyrite.

The Maggie Hill South deposit is the only one with a surface expression, discovered by Union Miniere in 1971. It is 400 metres south of the main mine. It shows low grade (0.9% average Ni), disseminated sulphides above the eastern contact of the Central Ultramafic Unit.

The Maggie Hays North deposit was discovered below the surface at 100-180 metres, by Amoco Minerals Australia in 1981. However it wasn't fully studied till 1993 by Lionore. The shoot strikes 1000 metres, averaging 2-3 metres thick, and covered by up to 20 metres of clay and colluvium. The resource shows an average 2% Ni. It is stringer sulphides in felsic volcanic rocks.

Other Regions, Features and Areas containing this locality

References