The Serra Verde lateritic REE deposit

The Serra Verde deposit in the Goiás Province of central Brazil is rich in recoverable rare earth elements (REE). We are developing a formation model for the deposit and investigating its potential for REE extraction. 

The Serra Verde deposit has an inferred resource of 458 million metric tonnes at a grade of 0.098% total rare earths (May 2012, 43-101 compliant). Heavy rare earth elements (HREE) account for 24% of the deposit.

The REE occur in a typically 6m-deep layer of clay-bearing saprolite produced by the deep weathering of granite. Initial testing suggests that more than 50% of the REE bulk are sorbed on clay and can be recovered by a simple elution process.

Project details

The Serra Verde project will develop a model for the introduction, enrichment and mineralogical residence of REE at the Serra Verde deposit. We aim to:

  • establish links between multiple magmatic events and REE introduction
  • determine and quantify the processes leading to REE enrichment
  • assess the effect of tropical weathering on REE grades and distribution
  • identify the residence of REE in primary, secondary and supergene minerals

Serra Verde Mining are supporting a PhD project undertaken by Carmen Pinto-Ward, co-hosted at the Museum and Imperial College. Contact carmen.pinto-ward08@imperial.ac.uk for details. 

Deposit formation

The Serra Verde REE deposit is associated with a Proterozoic alkali granite within the Goiás province of Brazil. The REE introduction and enrichment may be related to three main stages of geological evolution: 

  1. Emplacement of the Pela Ema tin granites (~1.8 Ga). This resulted in the formation of typical tin-bearing greisen veins hosting monazite and xenotime.
  2. Intrusion of an evolved alkaline (carbonatite?) complex at depth (~540 Ma).This caused potassium metasomatism (K-feldspar-biotite) with additional introduction or recrystallisation of monazite, xenotime and magnetite.
  3. Miocene(?) lateritisation. 

A 30-35m-thick lateritic weathering profile developed, resulting in breakdown of feldspars to clay and dissolution of REE-bearing minerals with reprecipitation in the saprolite ore zone. Colluvial accumulations of REE are also present.

Project details

Partners
Imperial College
Serra Verde Mining LLC

Funding
Serra Verde Mining LLC

Glossary