Abstract:
The Jequie granulitic complex is part of the extensive
high-grade metamorphic terrain located within the Sao Francisco
craton of northeastern Brazil. Some Jequie rocks appear to have
been formed in the middle Archean (~3.1 Ga) from preexisting
sialic crust_ The dominant mineral composition of these rocks
is quartz-microcline-plagioclase-hypcrstene and occurs over an
extensive area (~2,000 km2).
Scattered enTichment of normal granites with many minor
elements (e.g. Rb, Y, Zr, Nb, Ba, REE), and the non-depletion
of other elements (e.g. Cs, U), normally considered mobile
during granulite facies metamorphism, must lead either to the
reconsideration of regional metasomatism subsequent to granulite
facies metamorphism, or at least raise some doubts about
common wisdom concerning the distribution of heat-producing
elements at depth. The region includes large-scale thrust structures,
which could play a part in influencing high-level emplacement
of the rocks and their regional metasomatism and structures.