Melt-melt immiscibility and implications for the origin of Madeira albite-rich granite, Pitinga mine, Amazonas, Brazil: A melt inclusion study

Abstract Presented here are the results of the first studies of silicate melt inclusions hosted in quartz crystals from the two late granitic facies of the Paleoproterozoic Madeira pluton in the Pitinga mine, State of Amazonas, Brazil. The study of these magmatic inclusions in the anorogenic granite...

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Bibliographic Details
Published in:Brazilian journal of geology 2021-01, Vol.51 (4)
Main Authors: Borges, Régis Munhoz Krás, Amorim, Lucas Eustáquio Dias, Rios, Francisco Javier, Santos, Gabrielle Cristine Silva dos, Freitas, Monica Elizetti, Lima, Tatiana Aparecida Fernandes de, Santos, Armindo, Pedrosa, Tércio Assunção
Format: Article
Language:English
Subjects:
electron microprobe
GEOLOGY
GEOSCIENCES, MULTIDISCIPLINARY
LA-ICP-MS
melt inclusions
melt-melt immiscibility
peralkaline albite-rich granite
Pitinga mine
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Summary:Abstract Presented here are the results of the first studies of silicate melt inclusions hosted in quartz crystals from the two late granitic facies of the Paleoproterozoic Madeira pluton in the Pitinga mine, State of Amazonas, Brazil. The study of these magmatic inclusions in the anorogenic granites of Pitinga furnished reliable results because the original composition of the trapped silicate liquids is well preserved. Petrographic, morphological, and chemical data show that both porphyritic hypersolvus alkali feldspar granite and albite-rich granite were formed by melt-melt immiscibility from a precursor magma. After phase separation, albite-rich granite evolution was characterized by strong enrichment in F, Na, Sn, Nb, Ta, Zr, Th, Y, Rb, and REE compared to the porphyritic granite, based on data obtained from analyses of both trace elements by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and major elements by electron microprobe. These elements make up the polymetallic magmatic ore of the Pitinga mine. The contrasting evolutionary trends, peralkaline and peraluminous, stand out in the different geochemical signatures of the analyzed melt inclusions. The preliminary results of our studies on melt inclusions trapped in rare metal granite minerals from Sn-polymetallic deposits in Brazil suggest abundant possibilities for using this methodology in future petrological and metallogenic research.
ISSN:2317-4889
2317-4692
2317-4692
DOI:10.1590/2317-4889202120210011