Best wishes for 2000 everyone!
Has anyone come across sanidine in plutonic rocks, and if so what is its significance?
It looks like orthoclase (brownish colour, dusty appearance), is anhedral and interstitial, replacing plag and forming graphic intergrowths with quartz.
But it has a small 2V (10-30°) is almost uniaxial (characteristic of sanidine) and is optically negative .
The intrusion is a small (1-2 km) med grained granodiorite stock with marginal propylitic alteration. It contains granophyric intergrowths, miarolitic cavities and mm-scale veinlets of quartz, pyrite, pyrrhotite, magnetite, chalcopyrite and bornite. There is an extensive propylitised aureole and about 1 km away, areas of argillic, sericitic and advanced argillic alteration.
Any examples of sanidine in plutons?
Thanks - Rob
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Dr Robert CR Willan,
Magmatic-Hydrothermal Processes
Geological Sciences Division,
British Antarctic Survey,
Cambridge CB3 0ET, UK
Tel: 01223 221420
FAX: 01223 362616
Email: [log in to unmask]
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