Bushveld superplume drove Proterozoic magmatism and metallogenesis in Australia

Abstract

Large-scale mantle convective processes are commonly reflected in the emplacement of Large Igneous Provinces (LIPs). These are high-volume, short-duration magmatic events consisting mainly of extensive flood basalts and their associated plumbing systems. One of the most voluminous LIPs in the geological record is the ~ 2.06 billion-year-old Bushveld Igneous Complex of South Africa (BIC), one of the most mineralised magmatic complexes on Earth. Surprisingly, the known geographic envelope of magmatism related to the BIC is limited to a series of satellite intrusions in southern Africa and has not been traced further afield. This appears inconsistent with the inferred large size of the BIC event. Here, we present new radiometric ages for alkaline magmatism in the Archean Yilgarn Craton (Western Australia), which overlap the emplacement age of the BIC and indicate a much more extensive geographic footprint of the BIC magmatic event. To assess plume involvement at this distance, we present numerical simulations of mantle plume impingement at the base of the lithosphere, and constrain a relationship between the radial extent of volcanism versus time, excess temperature and plume size. These simulations suggest that the thermal influence of large plume events could extend for thousands of km within a few million years, and produce widespread alkaline magmatism, crustal extension potentially leading to continental break-up, and large ore deposits in distal sectors. Our results imply that superplumes may produce very extensive and diverse magmatic and metallogenic provinces, which may now be preserved in widely-dispersed continental blocks.

Testing Nano‐Powder and Fused‐Glass Mineral Reference Materials for In SituRb‐Sr Dating of Glauconite, Phlogopite, Biotite and Feldspar via LA‐ICP‐MS/MS

“…2020, Fiorentini et al . 2020). Aliquots (10–20 mg of Mica‐MG, ∼ 20 mg for GL‐O) of the RMs were mixed with 85 Rb‐ 84 Sr spike solution and digested at low pressure (3:1 HF: HNO 3 , 100 °C, 48 h, pure HNO 3 and finally 6 mol l ‐1 HCl).…”

Uranium–lead geochronology applied to pyrope garnet with very low concentrations of uranium

“…Janney et al 2010; Tappe et al 2018 b ). Constraining kimberlite emplacement may also aid detrital diamond prospecting, and models of the genesis of plume-associated metallogenic provinces (Fiorentini et al 2020).…”