Origin and nature of peridotites from the East-Azores Fracture Zone

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Studies of abyssal peridotites have the potential to unravel the composition of Earths heterogeneous mantle. During cruise M128 with RV METEOR in July 2016, such abyssal peridotites were recovered from the southern margin of the Azores Plateau. These rocks represent the first mantle rocks recovered from this region in the central North-Atlantic. Due to their proximity to the volcanic Azores islands, these mantle samples hold important constraints about this geodynamic setting. The questions to be addressed during the proposed project concern the chemical and isotopic (Hf-Nd) composition of these key-samples. One question in particular is, if these rocks are peridotites from the oceanic lithosphere that existed prior to the formation of the Azores Plateau, or if they represent residual mantle rocks of the outflowing Azores mantle plume. The latter is thought to be the ultimate mantle source for the lavas erupted on the Azores islands. New chemical and isotopic data will be acquired in the proposed study. The results will be contrasted to existing literature data on volcanic rocks from the Azores islands and the nearby MAR, which show that they originate from geochemically different mantle sources. Owing to these clearly established geochemical and isotopic differences between the MAR and Azores mantle, the proposed study will provide key constraints on the nature and origin of the exposed mantle at the EAFZ.