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Xenotime-hematite aggregates on opaline filaments: evidence for biomineralization in weathered siliciclastic rocks, Capanema, Quadrilátero Ferrífero of Minas Gerais, Brazil.
- Source :
-
International Journal of Earth Sciences . Jan2012, Vol. 101 Issue 1, p377-383. 7p. 1 Color Photograph, 2 Black and White Photographs, 1 Chart, 1 Map. - Publication Year :
- 2012
-
Abstract
- Dissolution cavities in weathered pebbly quartzite of the ~2.5-Ga Moeda Formation at Capanema, Quadrilátero Ferrífero of Minas Gerais, Brazil, are decorated with suspended filaments of opaline silica. The filaments sustain xenotime-hematite aggregates in the open space. Xenotime occurs as inclusions in buds and botryoidal aggregates of hematite. The filamentous structures consist of strand-forming buds, hypha-like extensions, and thin strands that compose mat-like arrangements. They resemble microbial filaments that were replaced by opaline silica and fossilized. The occurrence of spherical hematite as protuberances on hematite-free opaline hyphae is interpreted as accretion of dissolved iron onto extracellular polymers. Phosphate sites in polymeric substances expelled from the microbial filaments might have adsorbed yttrium and heavy rare-earth elements from groundwater to the iron-accreting polymers. These would have resulted in botryoidal aggregates of hematite with xenotime inclusions. The presence of authigenic xenotime in the weathering zone opens a new possibility to constrain the evolution of lateritic profiles by xenotime geochronology. [ABSTRACT FROM AUTHOR]
- Subjects :
- *MINERAL aggregates
*XENOTIME
*OPAL glass
*BIOMINERALIZATION
Subjects
Details
- Language :
- English
- ISSN :
- 14373254
- Volume :
- 101
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- International Journal of Earth Sciences
- Publication Type :
- Academic Journal
- Accession number :
- 70068775
- Full Text :
- https://doi.org/10.1007/s00531-011-0663-1