Antarctic Peninsula Volcanic Group

Antarctic Peninsula Volcanic Group is a significant Cenozoic volcanic province forming a discontinuous belt along the spine of the Antarctic Peninsula. This extensive assemblage of subduction-related volcanic rocks records the tectonic evolution of the peninsula from the Late Cretaceous through the Neogene. Its formations are crucial for understanding the final phases of Andean-style magmatism in Gondwana prior to the opening of the Drake Passage.

Geology and Tectonic Setting

The volcanic group is intrinsically linked to the long-lived subduction of the Phoenix Plate beneath the western margin of the Antarctic Plate. This convergent boundary activity was part of the broader Pacific Ring of Fire and represented the southern continuation of the Andean Volcanic Belt. Magmatism migrated eastward over time due to changes in the angle of the subducting slab, a process documented in analogous settings like the Central Volcanic Zone of the Andes. The eventual cessation of volcanism is attributed to the arrival of the Antarctic-Phoenix Ridge at the trench, leading to a ridge-trench collision and the cessation of active subduction.

Composition and Volcanic Features

The group exhibits a typical calc-alkaline suite ranging from basalt through andesite to rhyolite, indicative of its island arc affinity. Volcanic features are diverse, including remnants of large stratovolcano edifices, extensive lava flow fields, and thick deposits of pyroclastic rock such as ignimbrite. Significant volcaniclastic rock sequences, formed by lahars and epiclastic processes, are interbedded with the lavas. These rocks often show evidence of hydrothermal alteration, and localized mineralization similar to that found in the El Teniente deposit has been studied.

Distribution and Major Formations

The volcanic rocks are distributed along the length of the Antarctic Peninsula, with major outcrops in Graham Land and Palmer Land. Key formations include the Mount Poster Formation and the volcanics of the Jason Peninsula. Prominent individual volcanic structures, often deeply eroded by glaciers, include Mount Haddington on James Ross Island and peaks within the Princess Royal Range. The group is spatially associated with the older intrusive rocks of the Antarctic Peninsula Batholith.

Eruptive History and Geochronology

Eruptive activity spanned from approximately 90 million years ago in the Late Cretaceous to about 25 million years ago in the Late Oligocene or Early Miocene. Geochronology utilizing argon–argon dating and U-Pb dating on zircon crystals has refined this timeline. The peak of volcanism occurred during the Paleogene, coinciding with major global climatic shifts like the Paleocene–Eocene Thermal Maximum. The youngest volcanic centers are found in the far northeast of the peninsula, near Joinville Island.

Scientific Research and Exploration

Study of the group has been advanced by expeditions from the British Antarctic Survey, the United States Antarctic Program, and the Instituto Antártico Chileno. Pioneering geological work was conducted during the Heroic Age of Antarctic Exploration and later during the International Geophysical Year. Modern research employs remote sensing from satellites like Landsat, petrography, and geochemistry to correlate these rocks with those in Patagonia and the South Shetland Islands. This work provides critical data for reconstructing the tectonic history of the Scotia Sea region.

Category:Volcanism of Antarctica Category:Geology of the Antarctic Peninsula Category:Cenozoic volcanism