TY - JOUR
T1 - Reworked old crust-derived shoshonitic magma
T2 - The Guarany pluton, Northeastern Brazil
AU - Ferreira, Valderez P.
AU - Sial, Alcides N.
AU - Pimentel, Marcio M.
AU - Armstrong, Richard
AU - Guimarães, Ignez P.
AU - da Silva Filho, Adejardo F.
AU - de Lima, Mariucha Maria C.
AU - da Silva, Thyego R.
N1 - Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/9/1
Y1 - 2015/9/1
N2 - The 572Ma Guarany stock consists of magmatic epidote-bearing hornblende monzodiorite to biotite granite that intruded Paleoproterozoic orthogneisses about 10km inland from the coast in northeastern Brazil. Co-magmatic diorite enclaves and dikes are abundant throughout the pluton. The monzodiorite-granite pluton and diorite enclaves are shoshonitic and display continuous trends in variation diagrams. They display chemical and isotopic characteristics of crustal melts, such as enrichment in incompatible elements, high back-calculated initial 87Sr/86Sr ratios (avg. 0.71253), negative εNd (0.57Ga) values (avg. -14.58), as well as high and variable (+9.1 to +11.1‰VSMOW) δ18O (zircon) values. Correlations between O-isotope and whole-rock silica contents, as well as initial 87Sr/86Sr ratios with 1/Sr concentrations, suggest hybridization of a lower continental crustal melt with more felsic crustal rocks, concomitant with fractional crystallization. Amphibole chemistry and whole rock Zr, TiO2 and P2O5 contents suggest magma solidification at a pressure~7kbar and near liquidus temperature~900°C. The parental magma was likely formed by partial melting of old (tDM=2.0Ga) amphibolitic lower continental crustal rocks, in a post-collisional setting, probably triggered by underplating of mantle-derived mafic magma during the period of relaxation after collision.
AB - The 572Ma Guarany stock consists of magmatic epidote-bearing hornblende monzodiorite to biotite granite that intruded Paleoproterozoic orthogneisses about 10km inland from the coast in northeastern Brazil. Co-magmatic diorite enclaves and dikes are abundant throughout the pluton. The monzodiorite-granite pluton and diorite enclaves are shoshonitic and display continuous trends in variation diagrams. They display chemical and isotopic characteristics of crustal melts, such as enrichment in incompatible elements, high back-calculated initial 87Sr/86Sr ratios (avg. 0.71253), negative εNd (0.57Ga) values (avg. -14.58), as well as high and variable (+9.1 to +11.1‰VSMOW) δ18O (zircon) values. Correlations between O-isotope and whole-rock silica contents, as well as initial 87Sr/86Sr ratios with 1/Sr concentrations, suggest hybridization of a lower continental crustal melt with more felsic crustal rocks, concomitant with fractional crystallization. Amphibole chemistry and whole rock Zr, TiO2 and P2O5 contents suggest magma solidification at a pressure~7kbar and near liquidus temperature~900°C. The parental magma was likely formed by partial melting of old (tDM=2.0Ga) amphibolitic lower continental crustal rocks, in a post-collisional setting, probably triggered by underplating of mantle-derived mafic magma during the period of relaxation after collision.
KW - Crustal-derived shoshonite quartz monzonites
KW - Granite petrogenesis
KW - Post-collisional granites
UR - http://www.scopus.com/inward/record.url?scp=84937398796&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2015.06.030
DO - 10.1016/j.lithos.2015.06.030
M3 - Article
SN - 0024-4937
VL - 232
SP - 150
EP - 161
JO - Lithos
JF - Lithos
ER -