Dear Colleagues,
What could you say about such situation:
Large pluton (diameter is about some tens kilometers) of
Lodochnikovsky granites (Northern Taymyr, Russia) intruded black
shales (southern part of pluton) and chlorite-mica schists
(northen part). In the southern contact after black shales there
were formed fine-grained hornfels (width of zone is about 100-200
m); Limestones, situated at distance of 500 m from contact, are
fresh and not skarned. On the contrary, at northern border of the
pluton width of modified zone (appearance of garnet and
staurolite!) is about 1-2 km.
The granites are Hercynian, while black shales were formed in
Early Paleozoic time; green schists are Precambrian. No features
of Hercynian overprinting are known in the metamorphites far from
the intrusion.
I think that it is case of pure contact metamorphism. However,
absence of skarns shows a lack of water fluid around intrusion;
therefore contact metamorphism at the southern contact was not too
intense. Contact metamorphism in the schists (the northern
contact) was related with mobilized fluid extracted from hydrous
metamorphic minerals. Is it possible that many cases of "regional
contact metamorphism" (I also think that it is not good term) were
realized at the expense of metamorhic fluid heated by intrusions?
What do you think?
Pavel Azimov.
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Pavel Azimov
Institute of Precambrian Geology and Geochronology
Russian Academy of Sciences
2, Makarov Embankment
St.Petersburg, 199034, Russia
Phone: +7(812)328-03-62
Fax: +7(812)328-48-01
E-Mail: <[log in to unmask]>
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