The North America mid‐Cretaceous kimberlite corridor: Wet, edge‐driven decompression melting of an OIB‐type deep mantle source

Abstract

Thirty new high‐precision U‐Pb perovskite and zircon ages from kimberlites in central North America delineate a corridor of mid‐Cretaceous (115–92 Ma) magmatism that extends ∼4000 km from Somerset Island in Arctic Canada through central Saskatchewan to Kansas, USA. The least contaminated whole rock Sr, Nd, and Hf isotopic data, coupled with Sr isotopic data from groundmass perovskite indicates an exceptionally limited range in Sr‐Nd‐Hf isotopic compositions, clustering at the low ɛNd end of the OIB array. These isotopic compositions are distinct from other studied North American kimberlites and point to a sublithospheric source region. This mid‐Cretaceous kimberlite magmatism cannot be related to mantle plumes associated with the African or Pacific large low‐shear wave velocity province (LLSVP). All three kimberlite fields are adjacent to strongly attenuated lithosphere at the edge of the North American craton. This facilitated edge‐driven convection, a top‐down driven processes that caused decompression melting of the transition zone or overlying asthenosphere. The inversion of ringwoodite and/or wadsleyite and release of H2O, with subsequent metasomatism and synchronous wet partial melting generates a hot CO2 and H2O‐rich protokimberlite melt. Emplacement in the crust is controlled by local lithospheric factors; all three kimberlite fields have mid‐Cretaceous age, reactivated major deep‐seated structures that facilitated kimberlite melt transit through the lithosphere.

Geodynamic and Isotopic Constraints on the Genesis of Kimberlites, Lamproites and Related Magmas From the Finnish Segment of the Karelian Craton

“…It has been tentatively suggested that subduction may have occurred outboard of Baltica at around 800 Ma (e.g., Merdith et al., 2017; Merdith et al., 2021). However, there is no evidence for inboard subduction contemporaneous with the Kuusamo or younger Kaavi‐Kuopio kimberlites (discussed below) which is at odds with examples of kimberlites from North America where subduction is thought to have played some role in their genesis (e.g., Currie & Beaumont, 2011; Duke et al., 2014; Kjarsgaard et al., 2017).…”

Supplemental Material: Reconciling seismic structures and Late Cretaceous kimberlite magmatism in northern Alberta, Canada

“…period between 90 and 60 Ma. They are slightly younger than 115-92 Ma kimberlite fields within the North American mid-Cretaceous corridor [Kjarsgaard et al, 2017], and older than the Montana alkaline province intrusions (Sweet Grass Hills minettes; ~50 Ma) [Buhlmann et al, 2000]. The majority of kimberlites occur within the BHH cluster and were emplaced during two intervals at 88-81 Ma (n=10) and 68-60 Ma (n=4 ; Table S1); the older intrusions are diamondiferous (Table S1).…”

Oxidation state and metasomatism of the lithospheric mantle beneath the Rae Craton, Canada: strong gradients reflect craton formation and evolution

“…no garnet). The Somerset Island kimberlites were emplaced 93-98 Ma ago 21 . The smaller suite from Pelly Bay consists of one spinel lherzolite and two garnet-spinel lherzolites and two garnet lherzolites and is a subset of samples investigated by Liu et al 9 where they also focused on PGE geochemistry and Re-Os dating.…”