Crystallization conditions of two adjacent epidote + diopside-bearing granitic stocks, northeastern Brazil.

The Tamboril and Olho d'Água granitic stocks are part of the abundant calc-alkalic magmatic epidote-bearing granitic rocks in the Cachoeirinha-Salgueiro Terrane (CST) in the Transversal Zone Domain, northeastern Brazil. The equigranular Olho d'Água stock is composed of medium-grained clinopyroxene-amphibole-biotite tonalite; the porphyritic Tamboril stock is medium- to coarse-grained amphibole biotite ± clinopyroxene granodiorite. Abundances of clinopyroxene and epidote vary inversely in both stocks.

Coral-based climate records from tropical South Atlantic: 2009/2010 ENSO event in C and O isotopes from Porites corals (Rocas Atoll, Brazil).

Coral skeletons contain records of past environmental conditions due to their long life span and well calibrated geochemical signatures. C and O isotope records of corals are especially interesting, because they can highlight multidecadal variability of local climate conditions beyond the instrumental record, with high fidelity and sub-annual resolution. Although, in order to get an optimal geochemical signal in coral skeleton, sampling strategies must be followed.

Acritarchs of the Ediacaran Frecheirinha Formation, Ubajara Group, Northeastern Brazil.

We report for the first time the occurrence of organic-walled microfossils in Ediacaran limestones and marls of the Frecheirinha Formation, Ubajara Group, and the first Precambrian acritarchs so far reported for northeastern Brazil. The assemblage of the Frecheirinha Formation represents a low-diversity microflora comprising Leiosphaeridia, Lophosphaeridium and subordinated Bavlinella (=Sphaerocongregus). Their thermal alteration index (TAI) between 4+ and 5, suggests metamorphic temperatures exceeding 200-250°C.

Chemical and mineralogical characterization of elbaites from the Alto Quixaba pegmatite, Seridó province, NE Brazil.

The Alto Quixaba pegmatite, Seridó region, northeastern Brazil, is a 60 degrees/80 degrees SW-trending subvertical dike discordantly intruded into biotite schists of the Upper Neoproterozoic Seridó Formation. It has three distinct mineralogical and textural zones, besides a replacement body that cuts the pegmatite at its central portion and in which occur, among other gem minerals, colored elbaites. Elbaites usually occur as prismatic crystals, elongate according to the c-axis, with rounded faces and striations parallel to this axis.