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Greenstone assimilation by tonalite magma, Atikwa Lake, Ontario

Published online by Cambridge University Press:  01 May 2009

R. A. Heimlich
R. A. Heimlich
Affiliation:
Department of Geology, Kent State University, Kent, Ohio 44242, U.S.A.
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Summary

In the Atikwa Lake area biotite tonalite grades into a peripheral zone of hornblende tonalite as the contact with greenstone wallrock is approached. Greenstone inclusions, common within the hornblende tonalite, exhibit varying degrees of digestion and the host becomes more mafic near many such inclusions. The hornblende tonalite is more heterogeneous than the biotite tonalite, particularly near the contact with greenstone where inclusions are abundant. Modal analyses indicate the presence of large amounts of hornblende near the contact. Spectrographic analyses of composite tonalite samples show that silica decreases while alumina, iron oxide, magnesia, lime, titania, nickel, chromium, and vanadium increase toward the contact. As a whole the data support the conclusion that the peripheral hornblende tonalite is a contamination product which resulted from the assimilation of greenstone by intruding biotite tonalite magma.

Type
Articles
Information
Geological Magazine , Volume 108 , Issue 1 , January 1971 , pp. 1 - 12
Copyright
Copyright © Cambridge University Press 1971

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