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Title: Strain localization and fluid-assisted deformation in apatite and its influence on trace elements and U–Pb systematics.
Authors: Ribeiro, Bruno Vieira
Lagoeiro, Leonardo Evangelista
Faleiros, Frederico Meira
Hunter, Nicholas J. R.
Queiroga, Gláucia Nascimento
Raveggi, M.
Cawood, Peter Anthony
Finch, M.
Campanha, Ginaldo Ademar da Cruz
Keywords: Microstructures
Apatite recrystallization
EBSD - electron backscatter diffraction
Dynamic recrystallization
Fluid-assisted recrystallization
Issue Date: 2020
Citation: RIBEIRO, B. V. et al. Strain localization and fluid-assisted deformation in apatite and its influence on trace elements and U–Pb systematics. Earth and Planetary Science Letters, v. 545, p. 116421, set. 2020. Disponível em: <>. Acesso em: 19 fev. 2021.
Abstract: This paper presents electron backscatter diffraction (EBSD), trace element and U–Pb data of apatite grains from a granitic mylonite from the Taxaquara Shear Zone (SE Brazil). The mylonite recrystallized under upper-greenschist facies and presents two types of apatite with distinct microstructures. Type1 apatite appears in quartz-rich layers and does not exhibit any microstructural, crystallographic, or chemical evidence of deformation/recrystallization, and resembles the original igneous apatite. Type2 apatite appears in mica-rich layers and exhibits core-and-mantle microstructures, and intragranular subgrain development, suggesting that they have undergone dynamic recrystallization. Recrystallized tails of type-2 apatite grains exhibit a strong c-axis crystallographic preferred orientation parallel to the X-direction (stretching lineation), and lack evidence of dislocation density. This evidence from type-2 apatite grains, combined with REE depletion, high La and a negative Ce anomaly compared to type-1 grains, suggests that type-2 apatite tails underwent recrystallization via dissolution-precipitation creep, whereas parental grains underwent crystal-plastic deformation and subgrain formation through dynamic recrystallization. Phase-equilibrium modelling and quartz CPO opening-angle thermometry are consistent with recrystallization at ∼480 – 530◦C and 2.2 – 5.0 kbar. We were not able to determine precise deformation ages from type-2 apatite because fluid-assisted recrystallization appears to have substantially decreased the U/Pb ratio. We find that preferential fluid flow along high-strain, biotite-rich layers in the mylonite caused type-2 apatite to recrystallise, whereas type-1 apatite in low strain layers was unaffected and retained the characteristics of the protolith.
ISSN: 0012-821X
Appears in Collections:DEGEO - Artigos publicados em periódicos

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