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GEOLOGICAL SOCIETY OF AUSTRALIA

WESTERN AUSTRALIAN DIVISION


 

West Australian Geologist (WAG)

Bi-monthly newsletter of the Western Australian Division of the Geological Society of Australia Inc.

 

Number 494: April  ̶  May 2012  (4 Mb PDF file)

 

Past Issues

 

Monthly Meetings

Time:  5.30 pm for 6.00 pm formal start (bar open upstairs before talk)

Venue:  Irish Club of WA, 61 Townshend Rd, Subiaco

 Download a map showing the location, or check out the venue with Google Maps.

 

MAY ANNUAL GENERAL MEETING

Wednesday 2nd May, 2012

 

Talk title: A 3D mineralogical and geochemical model of the Salt Creek Gold deposit

 

Speaker: Dr Scott Halley (Director, Mineral Mapping Pty Ltd; Winner, GSA Gibb Maitland Medal 2012)

 

Abstract: The Salt Creek gold deposit is located on the southern end of the Mount Monger Dome. It was discovered in 2007(?) by Integra Mining Limited. The pre-mining resource was X tonnes at Y g/t for Z ounces.

Salt Creek is hosted in a fractionated dolerite sill. The dolerite has a chemical composition that resembles the composition of Paringa Basalt. Gold mineralization is related to a small displacement fault that cuts obliquely through the sill. Gold occurs in and around extensional vein arrays and in a laminated shear vein occupying the fault. The alteration is predominantly chloritic, with sericite and albite being relatively minor. The chlorite is totally pervasive and somewhat texturally destructive. Obtaining meaningful geological information from logging the RC chips is difficult, because everything comes out as fine-grained green rocks.

Early in the life of the project, Integra Mining made a decision to use a hyperspectral instrument to log all of the Salt Creek drill holes. The expectation was that the hyperspectral logging would map solid solution variations in the chlorite chemistry that would define a zonation pattern around the gold mineralization. The outcome was very different to the expectation. The spatial variations in chlorite compositions mimicked the fractionation zones within the sill. Rather than showing anything about the composition of the hydrothermal fluid, the spectral mineralogy provided an exquisitely detailed geological model of the deposit; a level of detail that could never have been obtained from visual logging. It appears that low salinity, CO2-rich fluids do not cause Fe or Mg to move around significantly within the system, so that chlorite chemistry reflects primary rock composition rather than hydrothermal fluid compositions.

 

 

Gibb Maitland Medal

 

Guidelines download: MS Word doc

 


 

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Last modified: 23 April 2012
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