Aspectos Geoquímicos Das Rochas Granitóides Da Suíte Intrusiva Pedra Pintada, Norte Do Estado De Roraima

Abstract

GEOCHEMICAL ASPECTS OF THE PEDRA PINTADA SUITE GRANITOIDS, RORAIMA STATE, BRAZIL Late to pos-Transamazonian granitoids from the Pedra Pintada Suite (PPS) crop out along an E-W trending belt at the northern part of Roraima state, limited by narrow shear zones. The PPS consiste of hornblende-biotite granodiorite with subordinate tonalites and monzodiorites (GND); biotite-monzogranites, with minor granodiorites (MZG); leuco to hololeucocratic monzogranites (MGL) and leucocratic syenogranite (SNG). These granitoids are metaluminous to weakly peraluminous and show calc-alkaline character. For the same silica range, the GND and MGL exhibit lower TiO 2 contents than the MZG and SNG. Relative to the MZG, MGL and SNG, the GND is characterised by higher Sr and lower Rb, Zr and Y concentrations. The MZG shows the higher REE contents among the PPS granitoids. REE patterns exhibit moderate to pronounced negative Eu anomalias, and multielementar diagrams demonstrate an enrichment in LIL relative to HFS elements. These chemical characteristics are similar to that observed in calc-alkaline granitoids from modern ares, or collision belts, characterised by subduction signatures. The geochemical and geological aspects of the PPS granitoids may be correlated to a pos-collisional setting related to the Transamazonian cycle.

Orosirian Calc-Alkaline Volcanism and the Orocaima Event in the Northern Amazonian Craton, Eastern Roraima State, Brazil

“…According to Brown et al (1984) (Fig. 4), they also present greater distribution in the calc-alkaline volcanic field than modern magmatic arc, showing similarities with the plot of calc-alkaline granitoids of Pedra Pintada (Fraga et al 1997b) and Água Branca suite, in contrast with the anorogenic Saracura and Mapuera suites (Fig. 4).…”

Paleoproterozoic evolution of the Guiana Shield in Suriname: A revised model

“…An alternative scenario is presented by Fraga et al (2008, 2009a,b, 2011). The Cauarane–Coeroeni high-grade belt (Fig.…”

“…In Roraima State in Brazil, south of the Cauarane–Coeroeni Belt, fragments of 2.04–2.03 Ga (meta-)igneous older crust have been found in the Trairão and Anauá complexes (too small to be represented on Fig. 2, but incorporated in the Uraricoera–Urubu unit), which were interpreted as remnants of magmatic arcs (Fraga et al, 2009a, 2011). The Trairão rocks are compositionally banded diorites, granodiorites and tonalites, the banding being expressed by aligned magmatically zoned plagioclase crystals.…”

1.94–1.93 Ga charnockitic magmatism from the central part of the Guyana Shield, Roraima, Brazil: Single-zircon evaporation data and tectonic implications

“…According to Fraga et al (2008a,b), the main tectono-thermal event along the Cauarane-Coeroeni Belt occurred at around 2.00 Ga, recording the collision of the Anauá and Trairão arcs with the juvenile Rhyacian crustal masses. A post-collisional A-type and high-K calc-alkaline I-type volcano-plutonic magmatism (Fraga et al, 1997c;Fraga et al, 2008c), extends along the northern border of the CauraneCoeroeni Belt. In Roraima, Brazil, ages of 1.98-1.96 Ga have been reported for this volcano-plutonic magmatism (U-Pb SHRIMP, Santos, 2003;Schobbenhaus et al, 1994).…”