부산대학교 도서관

An integrated petrological-petrophysical model for the Ediacaran crust of S Britain is based on a review of the c. 570-550 Ma Charnian volcano-sedimentary complex. The latter was emplaced in a magmatic rift wedge within juvenile continental crust of the c. 720-600 Ma Marches Terrane, a subduction magmatic domain formed at the margin of the Gondwana palaeocontinent. Primitive island arc tholeiite to more evolved calc-alkaline compositions characterize the Charnian magmatic arc. Inversion of aeromagnetic potential-field data and petrophysical modelling, reveal details of the internal structure of the Charnian Domain, including a median rift, superimposed annular structures and partitioning lineaments. The modelling suggests that the arc foundation could incorporate magnetite-rich cumulates, which may explain the anomalous geophysical properties, including crustal thickness, rigidity and buoyancy. There is no evidence for significant tectonic displacement between the Charnian Domain and its Marches Terrane host. Instead, the domain likely occupies a wedge-shaped arc/marginal rift-basin complex, propagated from a neighbouring ocean into the Gondwana margin. Contemporaneous volcanic rift successions in the Welsh Borderland and Wales of the 570-550 Ma Charnian magmatic phase developed in coeval ensialic rifts within less strongly extended Marches Terrane lithosphere. Comparable diversity of subduction-related magmatism is found in the Neogene-recent Hikurangi destructive margin of New Zealand, providing a plausible analogue for Charnian magmatism. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6805248