Metal enrichment in lithologically complex black shales: a case study from the Tremadocian of NE Estonia

Vanadium as a critical material: economic geology with emphasis on market and the main deposit types

“…The elevated trace metals may have been introduced into HMBS through a variety of processes including detrital fraction related to continental weathering; trace metals assimilated by organisms which after their death accumulated in favourable reducing depositional settings; authigenic, seawater-derived metals incorporated into shales during diagenesis under redox conditions; interaction of metal-bearing hydrothermal brines with sediments during diagenesis, late hydrothermal (epigenetic activity); and any combination of above processes (Coveney 2003; Pagès et al 2018; Henderson et al 2019; Hints et al 2021; Xu and Mao 2021, and references therein). Consequently, the trace element assemblages and the concentrations of enriched metals vary significantly by location and there is no universal explanation for these relationships.…”

“…For example, at Mecca Quarry Shale at Velpen, Indiana (Figure 4(a, b)), illite is reported to account for 65% of the vanadium, whereas organic material accounts for the remaining 35% (Peacor et al 2000). There is a lot of scientific speculation regarding the processes by which vanadium was incorporated into metalliferous black shales, as discussed by Peacor et al (2000) and Hints et al (2021). The effect of weathering distribution of vanadium on vanadium-bearing black shales is important, but not well-documented.…”