| 2 | The Colider and Roosevelt olcanic rocks (sw amazonian craton): geochemistry and sm-nd isotope characteristics of a silicic large igneous province显示文摘The volcanic rocks of the Colíder and Roosevelt formations are extensively exposed in the south-central portion of the Amazonian Craton where effusive and pyroclastic rocks have been mapped.Both units,topped by chemical sediments and oceanic facies as rhyolite and andesite lavas,rhyodacite,and porphyritic dacite,with frequent intercalations of pyroclastic and epiclastic deposits.Whole-rock geochemistry for 55 samples of rhyolitic to andesitic composition suggests the involvement of fertile mantle-derived components with E-MORB to OIB compositions.The analyzed rocks display calc-alkaline to shoshonitic affinity consistent with generation related to an active continental margin.The whole-rock Sm-Nd isotope data from selected felsic volcanic rocks of the Colíder and Roosevelt formations yield negative initial eNd values between–3 and–9,indicating the predominantly crustal nature of the parental magmas with early Archean to late Paleoproterozoic(ca.2.5–2.0 Ga)depleted mantle model ages. | Bruna Saar de Almeida Mauro César Geraldes Carlos Augusto Sommer Felipe Corrales Antonio Joāo Paes de Barros | 2021 | Acta Geochimica2021，40，6： | 1 |
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