Mineralogy and geochemistry of a giant agpaitic magma reservoir: The Late Cretaceous Poços de Caldas potassic alkaline complex (SE Brazil)

Lithos ◽  
2021 ◽  
pp. 106330
Author(s):  
Vincenza Guarino ◽  
Michele Lustrino ◽  
Alberto Zanetti ◽  
Colombo C.G. Tassinari ◽  
Excelso Ruberti ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Magma Reservoir ◽  
Alkaline Complex ◽  
Se Brazil ◽  
Poços De Caldas

The Late Cretaceous Impact of the Trindade Mantle Plume: Evidence from Large-volume, Mafic, Potassic Magmatism in SE Brazil

1995 ◽  
Vol 36 (1) ◽  
pp. 189-229 ◽  
Author(s):  
S. A. GIBSON ◽  
R. N. THOMPSON ◽  
O. H. LEONARDOS ◽  
A. P. DICKIN ◽  
J. G. MITCHELL
Keyword(s):  
Mantle Plume ◽  
Late Cretaceous ◽  
Large Volume ◽  
Se Brazil ◽  
Potassic Magmatism

TheREE-and HFSE-bearing phases in the Itatiaia alkaline complex (Brazil) and geochemical evolution of feldspar-rich felsic melts

2017 ◽  
Vol 81 (2) ◽  
pp. 217-250 ◽  
Author(s):  
Leone Melluso ◽  
Vincenza Guarino ◽  
Michele Lustrino ◽  
Vincenzo Morra ◽  
Roberto de' Gennaro
Keyword(s):  
Alkali Feldspar ◽  
Distribution Patterns ◽  
Trace Element Composition ◽  
Geochemical Evolution ◽  
Alkaline Complex ◽  
Quartz Syenite ◽  
Serra Do Mar ◽  
Ti Oxides ◽  
Se Brazil ◽  
High Concentrations

AbstractThe Late Cretaceous Itatiaia complex is made up of nepheline syenite grading to peralkaline varieties, quartz syenite and granite, emplaced in the metamorphic rocks of the Serra do Mar, SE Brazil. The nepheline syenites are characterized by assemblages with alkali feldspar, nepheline, Fe-Ti oxides, clinopyroxene, amphibole, apatite and titanite, while the peralkaline nepheline syenites have F-disilicates (rinkite, wöhlerite, hiortdahlite, låvenite), britholite and pyrophanite as the accessory phases. The silica-oversaturated rocks have alkali feldspar, plagioclase, quartz, amphibole, clinopyroxene and Fe-Ti oxides; the chevkinite-group minerals are the featured accessory phases and are found with allanite, fluorapatite, fluorite, zircon, thorite, yttrialite, zirconolite, pyrochlore and yttrocolumbite. The major- and trace-element composition of the Itatiaia rocks have variations linked to the amount of accessory phases, have smooth, enriched chondritenormalized rare-earth element (REE) distribution patterns in the least-evolved nepheline syenites and convex patterns in the most-evolved nepheline syenites. TheREEdistribution patterns of the quartz syenites and granites show a typical pattern caused by fractional crystallization of feldspar and amphibole, in an environment characterized by relatively high oxygen fugacity (>NiNiO buffer) and high concentrations of H2O and F, supporting the crystallization of hydrous phases, fluorite and F-disilicates. The removal of small amounts of titanite in the transition from the least-evolved to the most-evolved nepheline syenites stems from petrogenetic models involvingREE, and is shown to be a common feature of the magmatic evolution of many other syenitic/ trachytic/ phonolitic complexes of the Serra do Mar and elsewhere.

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