Discordant Calc-Silicate Bodies from the St. Just Aureole, Cornwall

D. H. M. Alderton and N. J. Jackson
Department of Geology, The University, Keele, Staffs. ST5 5BG, England
Institute of Applied Geology, King Abdul Aziz University, Jeddah, Saudi Arabia

Summary: Several discordant, garnet-bearing bodies are described from the St. Just part of the Land's End granite aureole, Cornwall. It is suggested that these formed by a combination of metasomatic replacement and dilation with concomitant precipitation. Other Ca-Fe aluminosilicates (containing large amounts of Zn, Sn, B, and Be) are also present in the bodies. The chemical, petrographic, and field evidence suggests that the introduced material was transported by hydrothermal fluids. These fluids could well be related to the intrusion of the granite and the earliest phases of ore mineralization. Chemical analyses of garnets, calcic amphiboles and one apatite, epidote, diopside, and axinite are given.

Mineralogical Magazine; December 1978 v. 42; no. 324; p. 427-434; DOI: 10.1180/minmag.1978.042.324.03
© 1978, The Mineralogical Society
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