A PETROLOGICAL, GEOCHEMICAL AND GEOPHYSICAL OVERVIEW OF CRETACEOUS-AGE KIMBERLITES AND LAMPROITES IN KANSAS

The presence of kimberlites and lamproites in the mid-continent of North America has been known for decades, but the mechanism(s) responsible for their formation—in a location far from thick (i.e. >200 km) Archean craton—remains unclear. At least 12 kimberlites and two lamproites occur in eastern Kansas, forming the southernmost extension of a 5000-km-long, north-south-oriented distribution of alkaline magmatism that extends from northern Canada to the Gulf of Mexico, referred to as the Mid-Cretaceous ‘corridor’ [1]. Geodynamic models proposed to explain the alkaline magmatism along the ‘corridor’ includes an association with mantle plumes [2], subduction of the Farallon plate [1, 3], and edge-driven convection (EDC) [4, 5]. Moreover, recent studies have proposed that kimberlite magmatism, in general, may originate from Large Low Shear Velocity Provinces (LLSVPs) located along the core-mantle boundary [6]. However, most Cretaceous kimberlites and lamproites in central North America occur adjacent to strongly attenuated lithosphere at the edge of the North American craton [4]. The Kansas kimberlites occur within this transition zone as well, but they are also ~65 km west of, and sub-parallel to, the axis of the late Precambrian Midcontinent Rift System. This pre-existing zone of lithospheric weakness may have facilitated eruption of the kimberlites and possibly the lamproites. In this presentation, we will review the current petrological, geochemical, and geophysical data for the kimberlites of Riley and Marshall Counties in the northeast and lamproites of Woodson and Wilson Counties in the southeast of Kansas, assessing their relevance to the various petrogenetic models proposed.

[1] Currie and Beaumont, 2011, EPSL, v. 303, p. 59; [2] Chu et al., 2013, Nature Geosci, v. 6, p. 963; [3] Duke et al., 2014, EPSL, v. 403, p. 1014; [4] Kjarsgaard et al., 2017, G3, v. 18; [5] Kempton et al., 2019. In Field Excursions for the 2019 GSA South-Central, North-Central, and Rocky Mountain Sections Joint Meeting (v. 52); [6] Giuliani et al., 2021, PNAS, v, 118(1)