A preliminary framework for magmatism in modern continental back-arc basins and its application to the Triassic-Jurassic tectonic evolution of the Caucasus

In contrast to intraoceanic back-arc basins, extension within a continental back-arc basin initiates within continental rather than oceanic lithosphere. The geochemical characteristics of magmatic rocks within continental back-arc basins are poorly understood relative to their intraoceanic counterparts. Here, we compile published geochemical data from five modern continental back-arc basins – the Okinawa Trough, Bransfield Strait, Tyrrhenian Sea, Patagonia plateau, and Aegean Sea/Western Anatolia – to establish a geochemical framework for continental back-arc magmatism.  This analysis shows that continental back-arcs yield geochemical signatures more similar to arc magmatism than intraoceanic back-arcs. We apply this framework to published data for Triassic-Jurassic magmatic rocks from the Caucasus arc system, which includes a relict continental back-arc basin, the Caucasus Basin, that opened during the Jurassic and for which the causal mechanism of formation remains unexplained. 40Ar/3...