Titaniferous magnetite and barite from the san gregorio de polanco dike swarm, paraná magmatic province, uruguay Report as inadecuate




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The San Gregorio de Polanco Dike Swarm Tacuarembó Department, Uruguay is the southernmost set of dikes in the Paraná Magmatic Province of Uruguay. Five major dikes have been identified with two main structural trends: N140º–N170º and N50º–N80º. The dikes have tholeiitic affinities and are composed of plagioclase An55, augite and augite-pigeonite, relicts of olivine and opaque minerals. These rocks have high contents of Fe–Ti oxides titanomagnetites, the mineralogical and textural characteristics of which have been studied using scanning electron microscopy and energy dispersive spectrometry techniques SEM – EDS. These features, along with other mineralogical and textural relationships, have been used to propose the following crystallization sequence for the dikes: i crystallization of olivine, plagioclase and Ca-rich pyroxene phenocrysts; ii precipitation of the first population of Ti-magnetite; iii crystallization of plagioclase and pyroxene in the groundmass; iv partial dissolution of Ti-magnetite by reaction with magmatic fluids; v crystallization of the second population of Ti-magnetite and finally, vi crystallization of interstitial barite. ResumenEl Haz de Diques de San Gregorio de Polanco Departamento de Tacuarembó, Uruguay es la ocurrencia más meridional de diques pertenecientes a la Provincia Magmática Paraná en Uruguay. Fueron identificados cinco 5 diques principales con dos direcciones estructurales principales: N140º - N170º y N50º - N80º, respectivamente. Son diques de afinidad tholeítica compuestos por plagioclasa An55, augita y augita-pigeonita, relictos de olivina y minerales opacos. Estos diques se caracterizan por el alto contenido de óxidos de Fe y Ti titanomagnetitas, cuyas características mineralógicas y texturales fueron estudiadas con microscopio electrónico de barrido y espectrometría de energía dispersiva SEM-EDS, incluyendo mapeos composicionales. Estas características junto con otras relaciones mineralógico-texturales presentes en estas rocas permitieron proponer la siguiente secuencia de cristalización: i cristalización de fenocristales de olivina, plagioclasa y piroxenos cálcicos; ii precipitación de una primera población de titanomagnetita, iii cristalización de plagioclasa y piroxenos conformando la matriz; iv disolución parcial de la primera población de titanomagnetitas por reacción con fluidos magmáticos; v cristalización de la segunda población de titanomagnetitas y finalmente, vi cristalización de barita intersticial.

Tipo de documento: Artículo - Article

Palabras clave: Geology, Petrology, titanomagnetite, barite, mafic dikes, Mesozoic, Uruguay





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151 EARTH SCIENCES RESEARCH JOURNAL Earth Sci.
Res.
SJ.
Vol.
17, No.
2 (December, 2013): 151 - 158 ORE DEPOSITS Titaniferous magnetite and barite from the San Gregorio de Polanco dike swarm, Paraná Magmatic Province, Uruguay Rossana Muzio1, Fernando Scaglia1 and Henri Masquelin1 Instituto de Ciencias Geológicas, Facultad de Ciencias, Iguá 4225, CP 11400, Montevideo, Uruguay Fax number: (00598) 2525 8617 1 ABSTRACT Key words: titanomagnetite, barite, mafic dikes, Mesozoic, Uruguay The San Gregorio de Polanco Dike Swarm (Tacuarembó Department, Uruguay) is the southernmost set of dikes in the Paraná Magmatic Province of Uruguay.
Five major dikes have been identified with two main structural trends: N140º–N170º and N50º–N80º.
The dikes have tholeiitic affinities and are composed of plagioclase (An55), augite and augite-pigeonite, relicts of olivine and opaque minerals.
These rocks have high contents of Fe–Ti oxides (titanomagnetites), the mineralogical and textural characteristics of which have been studied using scanning electron microscopy and energy dispersive spectrometry techniques (SEM – EDS).
These features, along with other mineralogical and textural relationships, have been used to propose the following crystallization sequence for the dikes: (i) crystallization of olivine, plagioclase and Ca-rich pyroxene phenocrysts; (ii) precipitation of the first population of Ti-magnetite; (iii) crystallization of plagioclase and pyroxene in the groundmass; (iv) partial dissolution of Ti-magnetite by reaction with magmatic fluids; (v) crystallization of the second population of Ti-magnetite and finally, (vi) crystallization of interstitial barite. RESUMEN Palabras clave: titanomagnetita, barita, diques máficos, Mesozoico, Uruguay El Haz de Diques de San Gregorio de Polanco (Departamento de Tacuarembó, Uruguay) es la ocurrencia más meridional de diques pertenecientes a la Provincia Magmática Paraná en Uruguay.
Fueron identificados cinco 5 diques...






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