CRITICAL MINERALS - PHOSPHOROUS & REE

PRISM is Developing a World-Scale Portfolio of Critical Minerals

Bioelemental Sedimentation

PRISM is excited with recent collaboration with Queens University and the latest “Origin Story” for the Clear Hills polymetallic deposit. During the 20th century the common deposition theory for Iron deposits (split into Iron Formations and Ironstones) was sedimentation from land-based weathering, erosion and deposition in shallow ocean shelf regions. During the first part of this century a new model has emerged that is leading to improved understanding and prediction of mineralogy.

“The enrichment of Rare-earth and other critical elements within sedimentary apatite of some phosphatic oolitic ironstones often results in a polymetallic deposit.”

[Dr Peir Pufahl, Queens University]

The Clear Hills polymetallic oolitic deposit is a type of Continental Margin Ironstone (shown in the lower of the images below).

The formation of such a deposit formation requires a “goldilocks” set of conditions including:

  • seafloor hydrothermal activity (to distribute the metals)

  • an anoxic water environment

  • oceanic upwelling

  • epicontinental seas featuring a shelf with seas with the correct depths, sunlight and temperatures that foster an environment for microbial organisms to thrive and that in turn cause bioelemental precipitation into a sediment.

These seas permit the sediment to roll around, creating ooliths composed of elemental iron and other metals centred about silicate particles.

The Clear Hills polymetallic ore experienced these conditions.

A common target indicator of the presence of Rare Earth Elements is mineralized Phosphorous (Apatite). Phosphorous can act like a sponge to attract Rare Earth Elements and hence the suggested correlation between sedimentary apatite and polymetallic deposits with REE.

The relatively high grade concentration of precipitated metals within this Continental Margin Ironstone is due to the formation being a relatively narrow band that runs along the shelf margin i.e. the available metals are deposited in a focused area - as compared to more widely precipitated iron deposits such as Banded Iron Formations (typically Hematite) or anoxic ocean floor deposits (typically Magnetite).

The isopach map for the Clear Hills deposit illustrates this elongated shape.