I have seen dolostone bands in greywacke sequences being totally altered to skarns, locally tremolite rich, but usually with variable amounts of other minerals like diopside, axinite and sulphides. The greywackes are highly altered too, of course, but not so obvious without close examination.
regards
Ralph Bottrill
Mineral Resources Tasmania.
03 6233835
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From: Metamorphic Studies Group [[log in to unmask]] on behalf of Bruce Yardley [[log in to unmask]]
Sent: Sunday, 7 October 2012 9:26 PM
To: [log in to unmask]
Subject: [geo-metamorphism]
Dear Trisrota
Are you sure it is tremolite? Pure tremolite rocks are normally derived from dolomitic marble, which seems unlikely with greywackes. In particular I think you need to have some idea of the Al-content, but just as important is a clear picture of the field relationships and whether there are veins or any metasomatic effects in other units nearby.
Bruce Yardley
Professor Bruce Yardley
School of Earth and Environment
University of Leeds
Leeds LS2 9JT
UK
Tel. +44 (0)113 343 5227
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From: Metamorphic Studies Group [[log in to unmask]] On Behalf Of Trisrota Chaudhuri [[log in to unmask]]
Sent: 07 October 2012 06:46
To: [log in to unmask]
Subject: [geo-metamorphism]
Dear all,
I've found some Archean, sheet like basic dykes which, when observed under thin section, is seen that they consist of 100% tremolite. They are associated with grewacke. Is there aby possibility that these mafics could be a part of metasomatized (rodingitized?) oceanic crust? Please enlighten me that how to explain the formation of such 100% tremolite bearing rocks.
--
Trisrota Chaudhuri,
JRF of Indian Statistical Institute and Jadavpur University,
Kolkata, India.
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