Linking the Siberian Flood Basalts and Giant Ni‐Cu‐PGE Sulfide Deposits at Norilsk

Abstract

The world‐class magmatic sulfide deposits in the Norilsk region exhibit a remarkable spatial and temporal association with the Siberian large igneous province (LIP). However, the details of the causal connection between the Siberian LIP and the ore deposits have remained contentious. Here we address the problem by modeling of assimilation, crystallization and flow behavior of magmas based on aggregated data from the Norilsk camp. Crustal assimilation at depth by mantle‐derived picritic magma can account for the compositional and isotopic variations of the early tholeiitic basalts and the sequestering of sulfide liquid in a mid‐crustal conduit system. When the rate and volume of asthenospheric magma production dramatically increased, the metal tenors of the mid‐crustal sulfide reservoir were first upgraded by consequent reaction with the fresh, undepleted magmas, then entrained and flushed to higher crustal levels. The resulting sulfide‐rich emulsions were too dense to reach the surface to form lavas but were instead emplaced in multiple pulses within blind sill‐like bodies at shallow depth. Sulfide ores transported from the mid‐crust were deposited at the bases of the upper‐crustal sills, where sedimentary host rocks were assimilated wholesale by the already sulfide‐charged replenishing magmas; this shallow assimilation was itself not instrumental in forming the ores. Although the evolution and dynamics of flood basalts are thus inextricably linked with coeval subvolcanic economic intrusions, the mineralization itself is argued not to occupy feeders with direct links to the overlying lavas, suggesting major implications for exploration in other LIPs.

Geochemistry of deep Tunguska Basin sills, Siberian Traps: correlations and potential implications for the end-Permian environmental crisis

“…On the contrary, Tuklonsky picrites can be related to the 277A1 dolerites by crustal contamination (as suggested previously for Nd-like basalts by, e.g. Wooden et al 1993;Fedorenko et al 1996;Reichow et al 2005;Yao and Mungall 2021). None of the analyzed dolerites show the characteristic highly fractionated LREE/HREE (e.g.…”

“…Rocks of this latter trend overlap the compositions of Norilsk-type intrusive rocks (Fig. 5a; Hawkesworth et al 1995;Arndt et al 2003;Yao and Mungall 2021). Strontium concentration and 87 Sr/ 86 Sr signatures correlate positively (Fig.…”

“…(Fig. 5a; Naldrett et al 1992;Hawkesworth et al 1995;Yao and Mungall 2021). We observe two potential trends in the Sr-Nd isotopic space.…”

“…Estimated pressures of crystallization of clinopyroxenes for Middle and Upper sequence rocks reveal crystallization at < 20 km depth, i.e. within the upper crust (Yao and Mungall 2021;Suvorov et al 2006). Clinopyroxenes from sill 260B are an exception, as they reveal crystallization pressures up to 8 kbar (Neave and Putirka 2017).…”

“…These are followed by the Upper sequence, including five suites of mainly tholeiitic basalts (Morongovsky to Samoedsky fromations) with uniform geochemical signatures, and representing the main tholeiitic pulse of the STLIP. The intrusions found in the Norilsk region have been classified into five types and correlated with the lava piles (Naldrett et al 1992;Hawkesworth et al 1995;Arndt et al 2003;Pavlov et al 2019;Yao and Mungall 2021). The most prominent intrusive types are the dolerites and differentiated intrusions (type 3), spanning the entire Norilsk region, the ore-bearing Norilsk-type intrusions (5A), and the Lower Talnakh-type (5B; Naldrett et al 1992).…”