The earliest Neoproterozoic magmatic record of the Pearya terrane, Canadian high Arctic: Implications for Caledonian terrane reconstructions

Abstract Succession I of the exotic Pearya terrane, northernmost Ellesmere Island, includes voluminous granitoid orthogneiss units that form the presumptive basement to this displaced crustal fragment. Previous whole rock Rb/Sr and multigrain zircon U/Pb geochronology revealed ages in a range from the latest Mesoproterozoic to earliest Neoproterozoic. This study presents new single grain zircon U/Pb geochronolgy from a suite of 7 samples that defines a relatively narrow range of earliest Neoproterozoic ages, from 964 ± 6 Ma to 974 ± 8 Ma. Whole rock trace element geochemistry reveals LILE enrichment decoupled from low to depleted HFSE values, suggestive of a subduction zone origin. Nd and Hf isotope geochemistry supports input from both juvenile and evolved materials, with eNd (i) values between −1 and −4.6, and a similar range for eHf values microsampled from zircon age domains consistent with the crystallization of the protolith. Documentation of abundant earliest Neoproterozoic magmatic ages reinforces correlations between Pearya Succession I and areas of the North Atlantic-Arctic Caledonides containing a tectonothermal record of earliest Neoproterozoic magmatism. The Northwestern, Northeastern, and Southwestern terranes of Svalbard record magmatic events in the c. 965 Ma–920 Ma range. Likewise, the lower Kalak Nappes of Norway and the East Greenland Caledonides preserve slightly older and younger magmatism and metamorphism, respectively. Slightly older ages occur in orthogneiss units of the south central Brooks Range and Farewell terrane, Alaska. The geochemical and isotopic data from the Pearya terrane orthogneiss units support links between these regions in terms of subchrondritic eNd (i) and Paleoproterozoic depleted mantle model ages. The Pearya terrane orthogneiss units and similar units dispersed in the Arctic are interpreted to have originated near or on the northeastern margin of Greenland, and record a continental arc later carried out of the Caledonide orogen into the Circum-Arctic realm. These data permit models for an exotic origin to the Pearya terrane as part of a later strike-slip orogenic system.