EAST BORDER OF THE SANTA QUITÉRIA MAGMATIC ARC: A NEW ULTRA-HIGH PRESSURE BELT IN THE CEARÁ CENTRAL DOMAIN?

Abstract

Magmatic arcs are associated with oceanic lithosphere subduction, which in progressive oceanic closure may culminate with continental collision. In a few Phanerozoic orogeny worldwide, subduction to mantellic depth above 150 km is being verified, which is evidenced through ultra-high pressure (UHP) and high pressure (HP) terrains. Recently, in the North portion of Borborema Province, West margin of Santa Quitéria continental magmatic arc (SQCMA), a belt of ultra-high pressure (Forquilha eclogitc zone) has been identified with the presence of coesite relics included in garnets of metamafic rocks (garnet piroxenites). Otherside, in the East margin of this arc, Lagoa da Caiçara Unit has been individualized orthogneiss with crystallization ages between 640 e 830 Ma and interpreted as an intra-oceanic arc. Magneto-telluric (MT) data have indicated that the SQCMA was originated by double subduction with opposite vergences. The aim of this project is to detail the tectonic context of the East margin of SQCMA, with a view to understanding collisional and accrescionary processes initiated during the Neoproterozoic, mainly involving oceanic crust remains. To accomplish that efforts will be concentrated in: detailed field analysis, petrological and thermobarometric studies, Sm-Nd, Lu-Hf and U-Pb geochronological analysis and geochemistry of metabasic and metassediemntary rocks possibly submitted to high depths conditions. (AU)