Youanmi Group, Sandstone Shire, Western Australia, Australiai

Regional Level Types
Youanmi Group	- not defined -
Sandstone Shire	Shire
Western Australia	State
Australia	Country

Gold was found in the area in 1894 or 1985 by prospector Tom Payne. Serious mining however did not take place till 1907. The Youanmi Gold Mine Limited operated the mine from 1911, but struggled during World War One with a shortage of labour and high costs, and finally closed in 1922. It employed around 100 men.

In 1934, the Youanmi Gold Mining Limited was floated in London with the intention of re-opening the mine as an underground operation. Production started in 1936. At this time the town of Youanmi was constructed to service the mine which employed around 200 men. Thirteen leases were purchased totalling 351 acres. Mine manager was P Fitzgerald. In 1942 the mine suddenly closed, citing poor ore at depth.

A large open pit was developed between 1986 to 1989. In 1995 underground mining commenced again producing 50 000 to 60 000 oz gold at 11.5 g/t. In 1997 the mine closed again due to low gold prices. In 2000 Aquilla Resources took over the mine, and sold it in 2003 to Goldcrest Resources, which sold the mine to Apex Minerals NL in 2007.
Apex considered opening the mine then abandoned the idea in favour of other mines it owned in the region. At the time of writing (April 2013) Apex is in the middle of selling the mine to Infinity Fame Pty Ltd.

The deposit is located in the north-west trending Youanmi Greenstone Belt of tholeiitic basalts and intrusives with minor banded iron formations and felsic pyroclastics. This is overlain by gabbro, pyroxenite, anorthosite and magnetite rich rocks of a layered intrusion.

There is intense shearing in the greenstone adjacent to the granite intrusion, and this contact zone contains the gold. The intrusion shows coarse grained quartz-plagioclase-microcline-biotite-adamellite. The gold bearing shear zone is sericite-quartz-sulphides, and are sub-parrallel with the granite and greenstone contact.

Weathering to 80 metres has reduced most of the rocks to clay and goethite. The host mafic rock contains abundant magnetite. Within this is interbedded intervals of tuffaceous sediments, and minor banded iron formations, with magnetite pseudomorphed by pyrite near the shears. Gold is found in the shear zones forming a lattice network extending 20 metres in the adamellite and to 100 metres in the greenstone along a 1 kilometre strike length. Gold occurs within pyrite and arsenopyrite, with sericite, quartz, chlorite, largely barren of gold either side of the shears.

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References