The phlogopites from the Jacupiranga carbonatite intrusions
- Creators
- Gaspar, José C.
- Wyllie, Peter J.
Abstract
Electron microprobe analyses of phlogopites from five carbonatite intrusions (C_1 oldest, to C_5 youngest) constituting the carbonatite plug in the Jacupiranga complex support previous conclusions based on magnetite analyses that C_2 to C_5 represent a trend of differentiation, and that C_1 has different chemical characteristics. All analyzed grains are zoned but no systematic zoning trends occur. The FeO/(FeO + MgO) ratio is very low (0.065 to 1.2), MgO is high (22.5 to 28.2%), TiO_2 is very low (up to 0.44w%), BaO may be very high (up to 10.3 w%), and Na_2O may be as high as 2.77 w%. With decreasing age from C_2 to C_5, MgO increases. Phlogopites from a banded reaction rock between carbonatite and jacupirangite are similar to, but not related to the phlogopites of the adjacent carbonatite. Compared with other carbonatite micas, the MgO-rich, TiO_2-poor Jacupiranga phlogopites present one of the less evolved compositions, similar to those in mantle peridotites. Carbonatite micas are generally lower in TiO_2 than BaO-rich micas from other rocks.
Additional Information
© 1987 Springer-Verlag. Received July 8, 1986; accepted October 27, 1986. We thank Serrana S/A de Mineracao, G. C. Melcher, and V. A. V. Girardi for making possible the field work of JCG, and I. M. Steele and J. V. Smith for invaluable assistance with microprobe analyses at the University of Chicago. Critical review by A. L. Montana and A. P. Jones was helpful. Financial support was provided by Conselho Nacional de Desenvolvimento Cientifico de Tecnológico (CNPq) PROC 201.158/80 and PROC 40.1410/81, Fundacão de Ampara a Pesquisa do Estãdo de São Paulo (FAPESP) PROC 80/470 and PROC 81/0168-8, and the Earth Science Division of the National Science Foundation Grants EAR 76-20410, and EAR 84-16583.Additional details
- Eprint ID
- 64676
- Resolver ID
- CaltechAUTHORS:20160223-110636413
- PROC 201.158/80
- Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
- PROC 40.1410/81
- Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
- PROC 80/470
- Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
- PROC 81/0168-8
- Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
- EAR 76-20410
- NSF
- EAR 84-16583
- NSF
- Created
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2016-02-23Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences