Central West Geology Technical Session
THURSDAY 18 April 2024
The Long Room, upstairs Hotel Canobolas
248 Summer Street, Orange. 6PM for 6:30PM
UST’s and Magmatic Silica Caps – What do they tell us?
Unidirectional Solidification Textures (USTs) are primary magmatic textures which comprise parallel to sub-parallel
bands of crystals, commonly quartz with oriented c-axis terminations. The UST zones are products of rhythmic
precipitation of quartzand quartz plus feldspar (or other rock-forming minerals) during periods of fluctuating over
pressuring of volatiles and fluids within relatively small cupolas. They occur in a wide variety of intrusion-
related mineral deposits and display several textural types. In some instances, magmatic silica carapaces may be
developed above USTs zones. The exsolution of a magmatic vapor phase accompanying or following UST formation
may serve as an important marker for magmatic-hydrothermal transition processes and the beginning of peak ore
precipitation.
Join us for the meeting, drinks, nibbles and dinner.
For more information: cwedg@aig.org.au
Speaker:
Doug Kirwin
SEG honourary lecturer
Doug Kirwin is an Australian geologist with 50 plus years of international exploration experience. He commenced
his career in Papua New Guinea with Anglo American in 1970 and later worked for AMAX in southeast Asia, Mexico
and the Pacific. From 1985 to 1995 Doug formed an independent consulting company mostly working in southeast
Asia. Subsequently, he was executive Vice President for Ivanhoe Mines from 1996 to 2012. Since that time, he
continues to enjoy the rocks with a ‘friends and fun” caveat. Doug has an MSc in mineral exploration from James
Cook University and enjoys contributing to SEG student programs and field trips, and working with young
professionals.
 
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