Petrogenesis and age of skarns associated with felsic and metamafic dykes from the Paraíba do Sul Complex, southern Espírito Santo State.
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Date
2017
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Abstract
This paper concerns the study of petrography, mineral
chemistry and geochronology of skarns generated at the contact of
marbles of the Paraíba do Sul Complex with felsic and metamafic
dykes in the southern Espírito Santo State. The marbles were metamorphosed
under P-T granulite facies conditions during the syn-collisional
stage of the Neoproterozoic Araçuaí orogen. Metamafic
bodies
are composed of amphibolite and hornblende granofels, while
felsic dykes consist of alkali-feldspar granite, monzogranite or syenogranite.
From marble towards the dyke, skarns related to the
metamafic bodies are composed of carbonate + olivine and diopside
+ hornblende zones. Skarn associated to the granitic dykes are composed
of three different zones: carbonate + tremolite, diopside, scapolite
+ diopside. Variations in mineral chemical compositions along
the metasomatic zones suggest introduction of Mg and Ca from the
marbles, Fe from the metamafic dykes and Na from the granitoids.
The presence of spinel in the metamafic dykes and their skarns indicates
that both were metamorphosed under granulite facies conditions
during the 580–560 Ma syn-collisional stage. U-Pb zircon geochronology
(LA-ICP-MS) of an alkali-feldspar granite dyke resulted
in a crystallization age of ca.540 Ma, which suggests that its skarns
are therefore younger than skarns associated with the syn-collisional
metamafic dykes.
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Keywords
Skarns, Petrogenesis, Paraíba do Sul Complex, Geochronology
Citation
MESQUITA, R. B. de et al. Petrogenesis and age of skarns associated with felsic and metamafic dykes from the Paraíba do Sul Complex, southern Espírito Santo State. Brazilian Journal of Geology, v. 47, p. 301-325, 2017. Disponível em: <http://www.scielo.br/scielo.php?script=sci_abstract&pid=S2317-48892017000200301&lng=es&nrm=iso>. Acesso em: 25 ago. 2017.