Dear All,
Never in my dreams did I ever expect to stir up such a hornet's nest! Now
I understand why I was never accepted in to the diplomatic service. But
I've learned a great deal from the exchange (including that Al's a great
guy).
My original question was really for a convenient phrase to use in a paper
title (actually it was a grant proposal). What I've learned is that, to
paraphrase Shakespeare, "the facies is the thing". At the risk of starting
another shouting match, it would seem that contact metamorphism is
metamorphism that immediately surrounds a localized magmatic heat source
(whatever the depth). Since the presence of such an aureole is defined by
field relations and mapping it is a structural term rather than a
petrologic one.
One could qualify "contact metamorphism" by using a petrologic adjective -
the obvious the highest temperature facies developed adjacent to the
pluton. Thus contact metaorphism at shallow levels could be called, for
example, "pyroxene-hornfels contact metamorphism". Intrusion at deeper
levels would produce - again for example "amphibolite contact metamorphism"
( the example that started all this and ?the one to use in my
paper/proposal)
In the cases where no contact aureole can be detected and mapped, then this
is regional metamorphism because the heat source, even if ultimately from
magmatic sources is not localized enough to produce an aureole structure.
Or am I tilting at aureoles?? (thereby referring to the Bard and Cervantes
in the same communication which is appropriate given my heritage and
present affiliation).
Gren
(Granpueblo)
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Grenville Draper
Feb 1999 to June 1999 on sabbatical leave at:
Area Geodinámica
Departamento de Geología
Universidad de Salamanca
37008 Salamanca
SPAIN Tel (34) - 932-294482 Fax (34) - 932-294540
Department of Geology
Florida International University
Miami, FL 33199,
USA Tel 305-348-3087 FAX 305-348-3877
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