Trace-element geochemistry of Archean volcanic rocks and crystal growth in southwestern Abitibi Belt, Canada

摘要: Trace-element geochemistry on 176 controlled samples in three adjoining Abitibi (∼2.7 b.y.) volcanic piles confirms the fundamental concept of Archean cycles composed lower tholeiitic and upper calc-alkalic parts. The piles, each as much 16 km thick, are either unicyclic or multicyclic. In latter case, display secular geochemical trends. All rocks studied indicated to have come from mantle sources. A feature magma genesis is simultaneous presence both depleted undepleted basalts closely resemble modern mid-ocean ridge basalts. andesites alkalic very similar oceanic island-arc some volcanic-arc high-K rocks, respectively. principal constraints geodynamic processes interpreted terms pulsating migrating diapirism—a type “hot-spot tectonics” mechanism involving a layered responsible for early (depleted source) later (undepleted parts, respectively, cycles.