CaracterizaÃÃo geolÃgica da regiÃo situada entre as localidades de Paranatama e Currais Novos (PE), porÃÃo Centro-Norte do DomÃnio TectÃnico Pernambuco-Alagoas, ProvÃncia Borborema

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This thesis presents the geological characteristics of an important region inserted in the Pernambuco-Alagoas Tectonic Domain (PEALTD), considered as an integrated part of a Neoproterozoic orogenic belt that borders the northern portion of the SÃo Francisco Craton. In this context, the main geological units that outcrop in the PEALTD are: 1) Paleoproterozoic basement: quartz-dioritic to tonalitic orthogneiss and migmatite, metaluminous, with positive εNd values and T(DM) model age of 1.9 Ga (Paleoproterozoic age); 2) metasediments derived migmatite: garnet - biotite metatexitic stromatic gneiss, with negative εNd values and T(DM) model age between 2.1 and 2.2 Ga (Paleoproterozoic age); 3) supracrustal sequence: quartzite and feldspatic-quartzite; 4) Metabasite: banded metabasites, calcic amphibole rich rocks and with tholeitic affinity; Massive metabasites, consist of rocks composed of garnet, plagioclase and diopside, calc-alkaline to alkaline affinity and indications of intra-plate basalt. Conventional U-Pb analyses in zircons from metabasite reveal a complex evolutive history; and 5) Granitoids formed by partial melting of metasediments: garnet two-mica monzogranite to biotite syenogranite, peraluminous calc-alkaline granites. Low pressure amphibolite to granulite facies regional metamorphism affected the orthogneiss, metasediments derived migmatite and metabasite rocks of the PEALTD during the Brasiliano orogeny. During this metamorphic event, the main metamorphic foliation (Sn transposition foliation) was developed. Later it was deformed by a ductile activity of the transcurrent shear zone system â Pernambuco Lineament (Sn+1 foliation). Conventional U-Pb isotopic data of monazite grains from two-mica monzogranite yield a crystallization age of 580Ma, probably associated to a sin to post-metamorphic event. 40Ar-39Ar determination age in muscovite grains from same monzogranite provided an age of 560Ma. It is compatible with another determined 40Ar- 39Ar age in biotite grains from orthogneiss. The closure temperature of isotopic system provided a cooling rate of 20ÂC/Ma for the monzogranite. During this research some results help to describe the tectonic evolution of the PEALTD, which probably represents the deep roots of a Neoproterozoic magmatic arc, formed by oceanic crust subduction beneath fragments of micro-continents of Archaean to Paleoproterozoic age

ASSUNTO(S)

geoquÃmica isotÃpica (sm-nd) e geocronologia (u-pb e 40ar-39ar) geociencias geochronology pernambuco-alagoas tectonic domain borborema province domÃnio tectÃnico pernambuco-alagoas landsat/etm+ airborne geophysical provÃncia borborema mineral chemical projeto cariris-velhos isotopic geochemical quÃmica mineral landsat/etm+ termobarometry termobarometria

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