Episodicity within a mid-Cretaceous magmatic flare-up in West Antarctica: U-Pb ages of the Lassiter Coast intrusive suite, Antarctic Peninsula and correlations along the Gondwana margin

Long-lived continental margin arcs are characterized by episodes of large-volume magmatism (or flare-ups) that can persist for ∼30 m.y. before steady-state arc conditions resume. Flare-up events are characterized by the emplacement of large-volume granodiorite-tonalite batholiths and sometimes associated rhyodacitic ignimbrites. One of the major flare-up events of the West Gondwana margin occurred during the mid-Cretaceous and was temporally and spatially associated with widespread deformation and Pacific plate reorganization. New U-Pb geochronology from the Lassiter Coast intrusive suite in the southern Antarctic Peninsula identifies a major magmatic event in the interval 130−102 Ma that was characterized by three distinct peaks in granitoid emplacement at 130−126 Ma, 118−113 Ma, and 108−102 Ma, with clear lulls in between. Mid-Cretaceous magmatism from elsewhere in West Antarctica, Patagonia, and New Zealand also featured marked episodicity during the mid-Cretaceous and recorded remarkable continuity along the West Gondwana margin. The three distinct magmatic events represent second-order episodicity relative to the primary episodicity that occurred on a cordillera scale and is a feature of the North and South American Pacific margin. Flare-up events require the development of a highly fusible, lower-crustal layer resulting from the continued underplating of hydrous mineralogies in the melt-fertile lower crust as a result of long-lived subduction. However, the actual trigger for melting is likely to result from external, potentially tectonic factors, e.g., rifting, plate reorganization, continental breakup, or mantle plumes.

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