SciELO - Scientific Electronic Library Online

 
vol.64 número2La aplicación de técnicas de señal analítica a las estructuras de la cuenca de las SalinasEl volcanismo oligoceno superior-mioceno inferior del grupo Doña Ana en la alta cordillera de San Juan índice de autoresíndice de assuntospesquisa de artigos
Home Pagelista alfabética de periódicos  

Serviços Personalizados

Journal

Artigo

Indicadores

  • Não possue artigos citadosCitado por SciELO

Links relacionados

  • Não possue artigos similaresSimilares em SciELO

Compartilhar


Revista de la Asociación Geológica Argentina

versão impressa ISSN 0004-4822versão On-line ISSN 1851-8249

Resumo

COLOMBO, Fernando; LIRA, Raúl  e  PANNUNZIO MINER, Elisa V.. Mineralogical Characterization Of Topaz From Miarolitic Pegmatites And W-Bearing Greisen In The A-Type El Portezuelo Granite, Papachacra (Catamarca Province). Rev. Asoc. Geol. Argent. [online]. 2009, vol.64, n.2, pp.194-200. ISSN 0004-4822.

The El Portezuelo Granite (Catamarca Province, NW Argentina), probably of Late Devonian or Early Carboniferous age, was emplaced at ≤ 2 kbar and displays the chemical characteristics of an A-type granite. It hosts small miarolitic pegmatites and dikes that belong to the NYF petrogenetic family, miarolitic class, miarolitic-REE subclass, with features more similar to those reported for the gadolinite-fergusonite type. Topaz is widespread both in pegmatites and in a W-bearing greisen genetically related to the granite. In pegmatites it occurs as crystals up to over 15 cm long, showing the forms {120} and {041} (dominant), and also {100}, {010}, {001}, {110}, {130}, {230}, {410}, {150}, {340}, {201}, {203}, {011}, {021}, {031}, {111}, {112}, {221}, {223}, and {445}. Crystals are colorless to pale yellow, more rarely brownish or bluish. Electron-microprobe analyses of gemmy crystals from pegmatites and greisen show that topaz is F-rich (between 19.01 and 20.12 wt. % F, most crystals being slightly zoned) and has very low MgO and TiO2 (≤ 0.02 wt.%), low FeO (≤; 0.03 wt.%), and up to 0.10 wt.% CaO. Refractive indices and unit-cell dimensions reflect the F-rich nature of the studied topaz. This occurrence produces the finest crystals yet known from western South America but probably has no economic potencial as gemstock producer.

Palavras-chave : Topaz; Miarolitic pegmatites; Greisen; A-type granite; El Portezuelo; Argentina.

        · resumo em Espanhol     · texto em Inglês     · Inglês ( pdf )

 

Creative Commons License Todo o conteúdo deste periódico, exceto onde está identificado, está licenciado sob uma Licença Creative Commons