| Full text | |
| Author(s): |
Ribeiro, V, B.
;
Lagoeiro, L.
[1]
;
Faleiros, F. M.
[2]
;
Hunter, N. J. R.
[3]
;
Queiroga, G.
[4]
;
Raveggi, M.
[3]
;
Cawood, P. A.
[3]
;
Finch, M.
[3]
;
Campanha, G. A. C.
[2]
Total Authors: 9
|
| Affiliation: | [1] Univ Fed Parana, Geol Dept, 100 Francisco Heraclito dos Santos St, Bloco 6, BR-35400000 Curitiba, Parana - Brazil
[2] Univ Sao Paulo, Dept Mineral & Geotecton, Rua Lago 562, BR-05508900 Sao Paulo - Brazil
[3] Ribeiro, B., V, Monash Univ, Sch Earth Atmosphere & Environm Sci, Clayton, Vic 3800 - Australia
[4] DEGEO EM UFOP, BR-35400000 Ouro Preto, MG - Brazil
Total Affiliations: 4
|
| Document type: | Journal article |
| Source: | Earth and Planetary Science Letters; v. 545, SEP 1 2020. |
| Web of Science Citations: | 0 |
| 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. Type-1 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. Type-2 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 similar to 480 - 530 degrees 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. (C) 2020 Elsevier B.V. All rights reserved. (AU) | |
| FAPESP's process: | 18/10012-0 - Fluid flow, deformation and tectonic significance of regional shear zones from the southern Ribeira Belt |
| Grantee: | Frederico Meira Faleiros |
| Support Opportunities: | Regular Research Grants |
| FAPESP's process: | 18/00320-9 - Crystallographic, deformational and thermocronological analysis of mylonites of Taxaquara shear zone (São Paulo) |
| Grantee: | Bruno Vieira Ribeiro |
| Support Opportunities: | Scholarships in Brazil - Master |