Submarine Piip Volcano, Western Aleutian Arc: Temporal Evolution from Back-Arc Rift to Island-Arc Stratovolcano

Tuesday, 31 January 2017
Marina/Gretel (Hobart Function and Conference Centre)
Maxim Portnyagin1, Kaj Hoernle1, Reinhard Werner1, Boris Baranov2, Folkmar Hauff1 and Gene M Yogodzinski3, (1)GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, (2)Shirshov Institute of Oceanology, Moscow, Russia, (3)University of South Carolina Columbia, Columbia, SC, United States
Abstract:
Submarine Piip Volcano, the westernmost large volcano in the Aleutian Arc, occupies the central part of the Volcanologists Massif ca. 50 km north of Medny Island, Russia. High-resolution multi-beam mapping and rock sampling of the volcano have been performed during R/V SONNE cruises SO201 in 2009 and SO249 in 2016. The expeditions were part of KALMAR and BERING research projects, international collaborations between Germany, Russia and the U.S.A., focused on the inception and evolution of the Bering Sea and its volcanically active margins.

Multi-beam mapping revealed a morphologically complex volcanic edifice and its base, indicating a multi-stage evolution that correlates with prominent changes in the composition of parental magmas. The northwestern and southeastern flanks of the ca. 30 km wide (in the NW-SW direction) massif consist of NE-SW elongated micro plateaus (“wings”), uplifted by ca. 1000-1500 m above the neighboring seafloor. The rocks from the deepest parts of the plateaus and a tilted basement block northwest from the massif are ol-plag-phyric tholeiites with MORB-like compositions (Ba/La=6.0-8.8, Pb/Ce=0.07-0.10, 87Sr/86Sr =0.70256-0.70271), which show very little contribution from a slab-derived fluid to their mantle source. The flank micro plateaus are complicated by NE-SW trending linear ridges and small nested volcanic edifices composed of ol±px±plag-phyric basaltic andesites and high-Mg andesites with an enhanced subduction-related signature (Ba/La=9.2-18.3, Pb/Ce=0.09-0.16, 87Sr/86Sr = 0.70264-0.70279). The central part of the massif is occupied by the ca. 2000 m-high ca. 15 km wide Piip stratovolcano, which reaches a minimum water depth of 500 mbsl in its summit area. Amph-bearing calc-alkaline dacites from the Piip summit have the most pronounced slab-related signature (e.g., Ba/La=18.8-20.7, Pb/Ce=0.17-0.21, 87Sr/86Sr =0.70277-0.70284)

Our new data on Piip Volcano suggest a unique temporal evolution of a single volcano from back-arc rift erupted low viscosity basaltic tholeiitic magmas to island-arc type stratovolcano formed by high-viscosity silicic magmas. The presentation will discuss possible models for the origin of the Piip volcano and its significance to the understanding of the geodynamic evolution of the Aleutian Arc.

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