| Full text | |
| Author(s): |
Azzone, Rogerio Guitarrari
[1]
;
Ruberti, Excelso
[1]
;
Enrich, Gaston E. R.
[1]
;
Gomes, Celso B.
[1]
Total Authors: 4
|
| Affiliation: | [1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil
Total Affiliations: 1
|
| Document type: | Journal article |
| Source: | CANADIAN MINERALOGIST; v. 47, n. 5, p. 1087-1103, OCT 2009. |
| Web of Science Citations: | 11 |
| Abstract | |
Zirconium- and Ba-rich minerals are found in gabbroic rocks from the Ponte Nova alkaline mafic-ultramafic massif in southeastern Brazil. The unusual mineralogical assemblage includes zirconolite, baddeleyite, Ba-rich alkali feldspar, and Ba- and Ti-rich biotite. Zirconolite of the Ponte Nova massif has higher levels of Zr (up to 1.172 apfu) than those registered in other terrestrial rocks and a prominent enrichment in the light rare-earth elements. Baddeleyite contains small quantities of Hf, Ti, and Fe. The Ba-rich alkali feldspar and Ba- and Ti-rich biotite contain up to 9.25 and 7.35 wt% BaO, respectively, and the biotite contains up to 12.01 wt% TiO(2). In the different intrusions of the Ponte Nova massif, such an unusual assemblage typifies the residual magma after the crystallization of clinopyroxene and olivine from previously enriched basanitic parental magma. The different trends of enrichments in REE and Th + U found for zirconolite of the intrusions of the Ponte Nova massif provide a better understanding of the variable degrees of enrichment of incompatible elements of the distinct gabbroic bodies. A lithospheric mantle source enriched in incompatible elements by the metasomatic action of volatile-rich fluids and with the presence of phlogopite or amphibole (or both) and other minor accessory phases could explain the presence of the Zr- and Ba-rich minerals in this gabbroic massif. (AU) | |
| FAPESP's process: | 08/03807-4 - Geochemical reconstitution of parental magma from cumulitic alkaline occurrences of Meso-Cenozoic ages of South-American Platform by "in situ" analysis of minerals. |
| Grantee: | Rogério Guitarrari Azzone |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |