Geochemical variability in the greenstone belts of Goiàs (Brazil): the Hidrolina and Crixàs sequences

The greenstone belts of Crixás and Hidrolina of Goiás, Brazil, are dismembered components of the same body or of originally adjacent belts. Their tectono-metamorphic history and stratigraphy is similar, as well as their components (meta-komatiites, meta-basalts and felsic meta-volcanics). Chemically, they differ for the CaO and Al2O3 versus MgO trends and for the behavior of many incompatible and compatible trace elements (Cr, Ni, Ti, Sc, Y, Zr, P). The difference in the Ca and Al behavior, which is anomalous at Crixás, is tentatively attributed to an unconstrained igneous crystallization process. This process should imply the growth of clinopyroxene into an olivine-dominated crystal mush, and has acted at Crixás and not at Hidrolina. The difference in the trace element behavior has been mainly attributed to a compositional and modal heterogeneity of the mantle source, which was probably spinel-richer at Crixás than at Hidrolina.