Major- and trace-element composition of REE-rich turkestanite from peralkaline granites of the Morro Redondo Complex, Graciosa Province, south Brazil


Autoria(s): VILALVA, F. C. J.; Vlach, Silvio Roberto Farias
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

20/10/2012

20/10/2012

2010

Resumo

Turkestanite, a rare Th- and REE-bearing cyclosilicate in the ekanite-steacyite group was found in evolved peralkaline granites from the Morro Redondo Complex, south Brazil. It occurs with quartz, alkali feldspar and an unnamed Y-bearing silicate. Electron microprobe analysis indicates relatively homogeneous compositions with maximum ThO(2), Na(2)O and K(2)O contents of 22.4%, 2.93% and 3.15 wt.%, respectively, and significant REE(2)O(3) abundances (5.21 to 11.04 wt.%). The REE patterns show enrichment of LREE over HREE, a strong negative Eu anomaly and positive Ce anomaly, the latter in the most transformed crystals. Laser ablation inductively coupled plasma mass spectrometry trace element patterns display considerable depletions in Nb, Zr, Hf, Ti and Li relative to whole-rock sample compositions. Observed compositional variations suggest the influence of coupled substitution mechanisms involving steacyite, a Na-dominant analogue of turkestanite, iraqite, a REE-bearing end-member in the ekanite-steacyite group, ekanite and some theoretical end-members. Turkestanite crystals were interpreted as having precipitated during post-magmatic stages in the presence of residual HFSE-rich fluids carrying Ca, the circulation of which was enhanced by deformational events.

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo, FAPESP[Proc. 08/00562-0]

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, CNPq[Proc. 307583/2008-2]

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, CNPq[Proc. 142838/2007-1]

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior, CAPES

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identificador

MINERALOGICAL MAGAZINE, v.74, n.4, p.645-658, 2010

0026-461X

http://producao.usp.br/handle/BDPI/30263

10.1180/minmag.2010.074.4.645

http://dx.doi.org/10.1180/minmag.2010.074.4.645

Idioma(s)

eng

Publicador

MINERALOGICAL SOC

Relação

Mineralogical Magazine

Direitos

closedAccess

Copyright MINERALOGICAL SOC

Palavras-Chave #turkestanite #chemical composition #trace elements #solid solution #peralkaline granite #Graciosa Province #Brazil #FIELD STRENGTH ELEMENTS #A-TYPE GRANITES #STRANGE LAKE #HYDROTHERMAL PROCESSES #CRYSTAL-STRUCTURE #IGNEOUS SYSTEMS #QUEBEC-LABRADOR #SYENITES #EKANITE #TAJIKISTAN #Mineralogy
Tipo

article

original article

publishedVersion