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Exotic Skarns

Posted by Jeremy Zolan  
avatar Exotic Skarns
January 22, 2009 10:53AM
us    
Skarns typically form through the metasomitization of a sedementary rock (such as marble) when it comes in contact with a pluton of granitic composition.

However, exotic skarns are known to occur. Some of which are formed when a pluton comes in contact with sulfidic shale, a banded iron formation, or evaporate deposit.

What are some examples of exotic skarns formed by metasomitization of unusual wall rock types such as those I listed above. Also, what is their mineralogy and petrology like?

Additionally, if an intermediate or mafic pluton such as diorite or basalt were to come in contact with a sedementary rock, would metasomitization occur? What would be the petrology of some examples of skarns formed this way, if they even can form under the conditions I am inquiring about?
avatar Re: Exotic Skarns
January 22, 2009 04:14PM
de    
"[...] if an intermediate or mafic pluton such as diorite or basalt were to come in contact with a sedementary rock, would metasomitization occur? What would be the petrology of some examples of skarns formed this way, if they even can form under the conditions I am inquiring about?"

Mazurov, M.P., Grishina, S.N., Istomin, V.E., and Titov, A.T. (2007): Metasomatism and Ore Formation at Contacts of Dolerite with Saliferous Rocks in the Sedimentary Cover of the Southern Siberian Platform. Geology of Ore Deposits 49(4), 271-284.

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Re: Exotic Skarns
January 22, 2009 10:58PM
Jeremy, with regard to igneous intrusions into evaporites, it depends on the composition of the evaporite. Evaporites often contain abundant carbonates, in which case you can expect similar reactions as in other carbonate host rocks, and often sulfates, borates, clay minerals... But when the intruded evaporite is just halite, nothing much seems to happen at all - just a sharp contact with no chemical reaction, except for perhaps minor recrystallization of species that were already present.
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