Banca de DEFESA: VINÍCIUS ANSELMO CARVALHO LISBOA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : VINÍCIUS ANSELMO CARVALHO LISBOA
DATA : 13/12/2019
HORA: 14:00
LOCAL: IGEO - UFBA
TÍTULO:

Shoshonitic magmatism in the Sergipano Orogenic System: Glória Norte Stock

PALAVRAS-CHAVES:

Sergipano Orogenic System, shoshonitic magmas, ultrapotassic magmas, Macururé Domain 

PÁGINAS: 213
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
SUBÁREA: Geologia
ESPECIALIDADE: Petrologia
RESUMO:

In the northern-central portion of the Sergipano Orogenic System there is an expressive Neoproterozoic granitic magmatism. These granites are, in part, medium- to high-k calc- alkaline and shoshonitic affinities. In the Macururé Domain (MD), the shoshonitic affinity plutons consist essentially of monzonites, with subordinate syenitic and granitic terms, and have crystallization ages between 588-631 Ma. In this plutonism, the volume of mafic enclaves is higher when compared to the calcalkaline magmatism of DM, being common to observe features that indicate coexistence and interaction between mafic and felsic magmas. In Gloria Norte Stock (GNS), the main representative of the shoshonitic plutons of MD, the enclaves are of three types: (i) mafic microgranular and (ii) minettes, which represent contemporary mafic magma pulses; and (iii) autolith, generated by the fragmentation of early cumulates, consisting predominantly of clinopyroxene.The mineral chemistry data and textural features observed in the amphiboles present in the mafic enclaves (MME) of GNS indicate that this is a primary phase that was rebalanced during the interaction between the basic-ultrabasic and intermediate magmas. Geochemical data show shoshonitic affinity (high K2O; alkali sum greater than 5%; K2O/Na2O > 1.22 and high Ba and Sr contents) for the monzonites and monzogranites studied, and ultrapotassic affinity (K2O> 3%, MgO> 3% and K2O/Na2O> 2) for MME. These rocks exhibit volcanic arc and post-collisional geochemical signature. Incompatible element enrichment and LREE-HREE fractionation show the need to consider an enriched mantle as a source of these magmas. Field and petrographic evidence, coupled with new geochemical, geochronological, and mineral chemistry data indicate that the ultrabasic and shoshonitic magmas were contemporary with granitic magmas, and that these magmas probably played an important role in the genesis of the granite.

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