|Latitude & Longitude (WGS84):||31° 17' 29'' South , 118° 41' 58'' East|
|Latitude & Longitude (decimal):||-31.29139,118.69944|
|Köppen climate type:||BSk : Cold semi-arid (steppe) climate|
|Name(s) in local language(s):||Edna May mine|
Open cut gold mine, currently operated by Evolution Mining. The Edna May mine is located near the northern end of the Westonia Greenstone Belt in Western Australia's Archaean Yilgarn Craton. The Westonia Greenstone Belt comprises a series of outliers of predominantly amphibolite-grade metamorphic rocks extending approximately 100km WNW from near Edwards Find, south of Southern Cross. The remainder of the terrane comprises granitic rocks and their metamorphosed equivalents.
The Edna May gold mineralisation is hosted within three en echelon tonalitic gneiss intrusions, namely Edna May, Greenfinch and Golden Point. The deposits are bound to the north and south by an ultramafic ampbibolite.
Current resource at Edna May is 48Mt at 1.0 g/t Au. Current annual production is 70-80koz Au.
A Western Australian Museum field trip to the mine took place in October 2009, during which full access was granted to collect from historical mine dumps and stockpiles. Two days of collecting yielded very little specimen material. None of the interesting secondary lead minerals reported by Simpson (1948) e.g. crocoite and tungsten-bearing wulfenite, were found. Such minerals in the oxide zone of orogenic gold deposits are often associated with high grade secondary gold mineralisation, and hence were usually earmarked for processing.
The deposit is found in a small greenstone roof pendant in granite. The sequence shows metamorphosed interbedded mafic schist, amphibolite schist, coarse grained amphibolite, hornblende-biotite schist, gneisses and some ultramafic rocks. The greenstone is sheared and highly contorted, dipping 50 degrees north-east. The greenstone is intruded by pegmatite and hornblende dykes.
The host to the mineralisation is an elongate north-west trending lens of biotite-hornblende gneiss, 420 metres long by 140 metres wide, as an enclave in mafic rocks.
The mineralisation is within thick folded quartz pegmatite reefs in fissures. The quartz is milky white and translucent. The source states rows of fluid inclusions have been found in the quartz. The gold is disseminated in the quartz, some feldspar and wolfram mineralisation, rather than in sulphides, although paradoxically gold grades are directly related to sulphide abundance. Gibb-Maitland states there was considerable masses of scheelite and wolframite, several inches in diameter in coarsely crystallised pegmatite veins, below the 550 foot level.
There are four parallel reefs called Edna May, South, Middle, and Consolidated. The reefs fold into an anticline, pitching 50 degrees north-west, and intersects at the surface as a boomerang shaped outcrop (now likely gone through mining). The reefs are broken into vertical offset sections by low angle faults, cut by granite dykes, and mafic dykes.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
50 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
GeochronologyMineralization age: Neoarchean : 2744 Ma to 2726 Ma
Important note: This table is based only on rock and mineral ages recorded below and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.
|Geologic Time||Rocks, Minerals and Events|
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
2500 - 4000 Ma
|undivided metamorphosed igneous and sedimentary rocks 74367|
Age: Archean (2500 - 4000 Ma)
Description: Komatiitic basalt, quartz-muscovite-andalusite schist, basalt, dacitic porphyry, granite with greenstone rafts, agglomerate, talc schist, banded gneiss, quartzite, amphibolite, schist, ultramafic rocks, banded iron formation, dolerite, granite
Comments: igneous mafic volcanic; meta-igneous ultramafic; synthesis of multiple published descriptions
Lithology: Igneous mafic volcanic; meta-igneous ultramafic
Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia). 
|Neoarchean - Mesoarchean|
2500 - 3200 Ma
|Archean crystalline metamorphic rocks|
Age: Archean (2500 - 3200 Ma)
Comments: Yilgarn Craton
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529.