Evolução dos fluidos em veios de quartzo encaixados nos micaxistos na auréola térmica no entorno do batólito de Acari, Nordeste do Brasil

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DOI:

https://doi.org/10.11606/issn.2316-9095.v21-160595

Palavras-chave:

Inclusões fluidas, Veios de quartzo, Micaxistos, Auréola térmica, Composição dos fluidos, Salinidade

Resumo

Os micaxistos que circundam o batólito granítico de Acari (idade ediacarana, 572 a 577 Ma) são caracterizados por elevada quantidade de veios de quartzo. Os veios são mais abundantes nas zonas metamórficas com temperaturas mais altas, que somadas àquelas de temperaturas mais baixas formam a auréola que envolve o batólito. Os veios analisados são provenientes das zonas da biotita + clorita + muscovita, biotita + granada, cordierita + andaluzita e cordierita + sillimanita. Grande parte das inclusões fluidas são bifásicas, porém as variedades trifásicas podem ser localmente observadas. As temperaturas de fusão do CO2 (TfCO2) variam de -62,6 a -56,7°C. As temperaturas eutéticas (Te) mostram valores médios de -30,8°C nas zonas da biotita + clorita + muscovita e biotita + granada e de -38,6°C nas zonas da cordierita + andaluzita e cordierita + sillimanita. As temperaturas de fusão do gelo (Tfgelo) são mais baixas nas zonas metamórficas de mais altas temperaturas. Os valores das modas são de -3,8, -5,5, -5,6 e -7,3°C, que correspondem respectivamente às zonas de biotita + clorita + muscovita, biotita + granada, cordierita + andaluzita e cordierita + sillimanita. Um fluido caracterizado pelo sistema H2O-NaCl (KCl)-MgCl2- FeCl2-CaCl2 é definido por: Tfgelo que varia de -1,9 a -32°C; presença de cubos de sal nas zonas da cordierita + andaluzita e cordierita + sillimanita; e Te registradas entre -16,5 e -59,1°C. Adicionalmente, foram obtidas temperaturas de homogeneização total que variaram entre 117 e 388°C para as inclusões fluidas aquosas primárias. Os resultados são consistentes com o aumento da salinidade dos fluidos aquosos ao longo da auréola, na direção do batólito.

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2021-11-23

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Souza, L. C. de ., Delgado, R. C. de O. B. ., & Maia, H. N. . (2021). Evolução dos fluidos em veios de quartzo encaixados nos micaxistos na auréola térmica no entorno do batólito de Acari, Nordeste do Brasil. Geologia USP. Série Científica, 21(4), 13-30. https://doi.org/10.11606/issn.2316-9095.v21-160595

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