Deposit types/Rare earths, Niobium, Phosphate rock

Carbonatite and alkaline intrusion

Round igneous complexes with a core of carbonate rock that hold rare earths, niobium, phosphate and iron.

What it is

Round igneous complexes with a core of carbonate rock that hold rare earths, niobium, phosphate and iron.1,2

How it forms

A carbonate-rich magma from small degrees of mantle melting crystallises in several stages in a central plug with ring dykes around it. Alkali-rich fluids alter the wall rock (fenitisation). Weathering of the top can enrich niobium, phosphorus and rare earths in a residual soil.1,2

Host rocks

Carbonatite (sovite and ankerite types), pyroxenite, ijolite, fenite.1,2

Where it forms

Continental shields and rift lines such as the East African rift.1,2

How old

Complexes cut Precambrian shields; carbonatites themselves may be much younger1,2

How geologists look for it

Radiometric and magnetic anomalies.1,2

Mines of this type

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Mines

An example ofMount WeldSee Mount Weld, an example of this deposit type.1An example ofAraxa (CBMM)See Araxa (CBMM), an example of this deposit type.1An example ofNiobecSee Niobec, an example of this deposit type.1An example ofMountain PassSee Mountain Pass, an example of carbonatite and alkaline intrusion.1

Sources

  1. Mineral Deposit Models (Bulletin 1693, Cox and Singer, eds., 1986) US Geological Survey
  2. Mineral Deposit Models for Resource Assessment, Chapter J: A Deposit Model for Carbonatite and Peralkaline Intrusion-Related Rare Earth Element Deposits (SIR 2010-5070-J) US Geological Survey

From the Prospector Trails mining history dataset: each fact links to the source it was checked against. Figures are as the source gives them, in the money of their day. Not investment advice.

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Pictures: Mijnramp Bois du Caizier, Marcinelle, België. Schacht, Rossem, Wim van / Anefo / Europeana (Public Domain Mark 1.0); Salar de Atacama, Chile, NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team (Public domain (NASA media, no copyright)); Pangkalpinang. Mijn 3b. Een reeks koelies bezig met het transporteeren van grond, Europeana (Public Domain Mark 1.0).