Trench‐proximal volcanism following ridge crest‐trench collision along the Antarctic Peninsula

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Abstract
On the basis of multichannel seismic reflection, magnetics and bathymetry data, a Pleistocene‐Holocene (87Sr/86Sr 0.70265–0.7028, 143Nd/144Nd approximately 0.5129) and are totally lacking in any evidence for interaction with subduction‐enriched mantle. Geochemical similarities with other, more trench distal, postsubduction alkalic basalts along the Antarctic Peninsula are striking, strongly implying that all the postsubduction basalts were derived from a chemically similar asthenospheric source region. The basalts were most likely to have been generated as a result of the formation of a slab window beneath the Antarctic Peninsula following ridge crest‐trench collision. Subduction component‐free subslab asthenosphere upwelled into the incipient void left by the continued sinking of the leading plate following collision, and decompressional melting resulted. This type of trench‐proximal volcanism following ridge crest‐trench collision differs from that in other locations where calc‐alkaline volcanism persisted or ophiolite obduction occurred.