Petrologia do Stock Canindé Velho, sistema orogênico sergipano, NE Brasil

Abstract

The Canindé Velho Stock is a monzonitic intrusion with 6 km2 and with UPbShirimp age of 640 ± 4 Ma occurring in the far northeastern Sergipe Orogenic System in Canindé Domain next to the Xingó dam. It is intrusive in the granitic terrain of Curralinho Suite. Its contacts are intrusive and controlled by fractures. It was identified in that stock, the presence of biotite hornblende quartz monzodiorite rocks, hornblende biotite quartz diorite and an enclave that has composition of biotite diorite. These rocks show no evidence of metamorphism, but have structures and igneous textures interpreted as posttectonic. The predominant mafic minerals hornblende, biotite and the diopside. The mineral chemistry identified the crystals present as diopside with restricted composition (0.62 <W <0.88, 0.370 <En <0.389; 0.124 <Fs <0.160); amphiboles corresponding to ferrohornblenda-ferrotschemark and ferroednitaferrohastingsita in monzodiorite, tschermakita-magnésiohornblenda of diorite, and the enclave magnesiohornblenda-actinolite, and crystallization pressures between 5 and 7 kbar; biotite have total aluminum between 2.2 to 2.6 apu, low titanium (0.092 to 0.352 apu) and provided 600-652 °C temperatures; plagioclase match oligoclase and andesite (26-32% An); epidote; zircon and fluoride-apatite. The geochemical data indicate that the stock rocks are metaluminous, calc-alkaline and alkaline-calcic, and have magmas signature associated with subduction (valleys in Nb, Ta, Ti, P) for multielement diagrams. The zircon crystallization temperatures were estimated between 813 °C and 900 °C. The petrographic, mineralogical, geochemical and geochronological data allow us to infer that the most important tectonic event, which deforms the basement in Canindé Domain occurred before 636 Ma.