The tectonic significance of peri-Gondwanan Late Neoproterozoic-Early Palaeozoic felsic peraluminous magmatism

作者：Marcos García‐Arias, Matías M. Morales Cámera, Juán A. Dahlquist, Ping Gao, Simon Couzinié, Alejandro Díez Montes · 发表于：Earth-Science Reviews · 年份：2024 · DOI：10.1016/j.earscirev.2024.104803 · 被引用次数：16 · 研究领域：Geological and Geochemical Analysis、earthquake and tectonic studies、High-pressure geophysics and materials

We provide a thorough review of the literature on peraluminous magmatism of Late Neoproterozoic and Early Palaeozoic (mostly Late Cambrian-Middle Ordovician) age cropping out in many places around the world (SW South Africa, NE Patagonia, NW Argentina, Colombia, SE Mexico and Guatemala, the European Variscan Massifs and from Turkey to northern Burma through Tibet). Petrographically, these volcanic and plutonic rocks contain K-feldspar phenocrysts and sometimes smaller bluish-quartz phenocrysts in a glassy/fine-grained (volcanic/subvolcanic) or medium- to coarse-grained (plutonic) matrix of quartz, plagioclase, K-feldspar and biotite, with other Al-bearing phases such as muscovite and garnet as minor phases. Notably, amphibole is conspicuously absent. Geochemically, these dacitic (tonalitic) to rhyolitic (granitic) rocks are silica-rich, peraluminous and with a strongly crustal SrNd isotopic signature, pointing to S-type magmatism, but they also show characteristics of I-type subduction (a trace element signature typical of continental-arc magmatism) and A-type (enrichment in Ga) magmatism. A prominent geochemical feature is a marked depletion in Sr, resulting in low to very low Sr/Y ratios (usually <5). This, together with flat HREE slopes, suggests melting at low pressures. The arc signature is inherited from their crustal sources, which may comprise an old crustal basement and sediments derived from Pan-African and from Andean-type orogenic belts. Coeval, volumetrically min...