Rare Earth Elements (REEs)

• Found in lamprophyre intrusions within Haast Schist (South Westland, northwest Otago) and in the mafic-ultramafic Tapuaenuku Igneous Complex (Marlborough).
• REE-bearing minerals include monazite, thorite, apatite, rutile, aegirine, albite, pyrite, sphalerite, and galena.
• Some of the highest recorded REE concentrations are from the Haast River carbonatites (up to 12,560 ppm La+Ce+Y).

• Associated with peralkaline and alkaline igneous intrusions in West Coast, Fiordland, Canterbury, northwest Nelson, and Marlborough.
• REEs  occur in bastnäsite group, allanite, zircon, fergusonite, xenotime, monazite, florencite, perrierite-loparite and fluorapatite.
• French Creek Granite (600 ppm REE) and Sams Creek (719 ppm REE) are notable.

• Monazite (± xenotime) is a common accessory mineral in South Island granitoid rocks, particularly in Foulwind and French Creek granites.
• Some granites contain up to 0.042 wt% monazite (Cape Foulwind).

• Occur in the Paparoa Range and are linked to hydrothermal alteration along crustal-scale detachment faults that were active during a previous extensional tectonic regime.
• Elevated REE concentrations are reported in stream sediments.

•  Ion-adsorption type deposits occur in Northland (Kerikeri Volcanic Group) with halloysite clays from weathered alkaline rhyolite hosting REEs.
• Matauri Bay (678 ppm La+Ce+Y) and other sites show potential for low-cost REE extraction.

• Detrital monazite and xenotime are found in West Coast, Fiordland, Stewart Island,  Southland and northwest Nelson heavy mineral beach sands and alluvial deposits.
• Allanite is a significant REE-bearing mineral in Westland sands, potentially a by-product of garnet mining (up to 0.83 vol%). 
• Barrytown and Westport have the highest monazite concentrations (up to 0.12 vol%).

Carbonatites are igneous rocks, and related hydrothermal alteration, rich in carbonate minerals, and are often associated with the mantle-derived magmatism typical of intracontinental rift settings.

REEs are commonly hosted in minerals such as:

• Bastnäsite group ((Ce,La,Y)CO₃F) – A primary source of light REEs (LREEs).
• Monazite ((Ce,La)PO₄) – Contains both LREEs and thorium (radioactive).
• Ancylite ((Sr,Ca,Ce,La)(CO₃)₂(OH)·H₂O) – Occurs in some deposits.
• Xenotime (YPO₄).
• (Fluor)apatite (Ca₅(PO₄)₃(F,Cl,OH)). 
• Florencite ((Ce,La)Al₃(PO₄)₂(OH)₆) – found in carbonatites and associated hydrothermal alteration.
• Pyrochlore ((Na,Ca,REE,U)₂Nb₂O₆(OH,F)) – Found in carbonatites and associated alkaline complexes.
• Allanite ((Ca,REE)₂(Al,Fe)₃(SiO₄)₃(OH)) – typical of carbonatites and associated rocks.

 
Key Deposits:

• Bayan Obo (China) – The world’s largest REE deposit, hosted in a carbonatite-iron ore complex.
• Mountain Pass (USA) – A bastnäsite-rich deposit supplying LREEs.
• Araxa (Brazil) and Kola Peninsula (Russia) – Major sources of REEs in carbonatite systems.
   

Alkaline rocks and peralkaline granites can host substantial REEs in pegmatites and hydrothermal veins and are typically associated with partial melting of an enriched, often mantle-derived source in late- to an-orogenic or intracontinental rift settings.
REEs are commonly found in minerals such as:

• Eudialyte (Na₄(Ca,Ce)₂(Fe²⁺,Mn,Y)ZrSi₈O₂₂(OH,Cl)₂) – Hosts zirconium and heavy REEs (HREEs).
• Pyrochlore ((Na,Ca,REE,U)₂Nb₂O₆(OH,F)) – Found in REE-rich alkaline complexes.
• Bastnäsite group ((Ce,La,Y)CO₃F) – A primary source of light REEs (LREEs).
• Gadolinite ((Ce,La,Nd,Y)₂(Fe²⁺Be₂Si₂O₁₀) – typical of alkaline rocks and associated hydrothermal alteration.
• Loparite ((REE,Na,Ca)(Ti,Nb,Ta)O₃) – common in alkaline to peralkaline igneous rocks.
• Allanite ((Ca,REE)₂(Al,Fe)₃(SiO₄)₃(OH)) – typical of alkaline rocks and associated hydrothermal alteration.
• Fergusonite ((Ce,Nd,Y)NbO₄) – hydrothermal alteration associated with alkaline complexes.

 
Key Deposits:

• Ilímaussaq (Greenland) – One of the largest eudialyte-hosted REE resources.
• Kringlerne (Greenland) and Lovozero (Russia) – Peralkaline-hosted deposits with significant HREE potential.
• Strange Lake (Canada) – globally significant deposit of both HREEs and LREEs hosted within a peralkaline granite and related pegmatites and aplites. 

Formed by intense chemical weathering of REE-rich rocks (often carbonatites), concentrating mainly LREEs in residual clays and laterites. They are typically found in tropical regions with high rainfall and prolonged chemical weathering. Aggressive acid leaching (e.g., sulphuric acid) is required to extract LREEs from resistant minerals.

REEs are commonly found in minerals such as:

• Monazite
• Apatite
• Pyrochlore
• Crandallite group
• Bastnäsite group
• Churchite
• Rhabdophane
• Plumbogummite
• Florencite
• Xenotime
• Cerianite
   

Key Deposits:

• Mount Weld (Australia) – A laterite-hosted LREE deposit derived from weathered carbonatite.
• Tantalus (Tanzania) – A lateritic REE deposit with economic potential.
• Dong Pao (Vietnam) – A deeply weathered laterite deposit within syenite rocks and associated hydrothermal alteration. 

Formed by partial chemical weathering of granite and REE-bearing minerals, leading to adsorption of REEs onto clay minerals. These deposits are important sources of HREEs, including Dy, Tb, and Y. REEs can be extracted using simple ionic exchange with ammonium sulphate or weak acid solutions, without aggressive leaching.

REEs are commonly found in minerals such as:

• Kaolinite (Al₂Si₂O₅(OH)₄) – Often in the form of halloysite.
   

Key Deposits:

• Southern China (Jiangxi, Guangdong, Guangxi Provinces) – The world’s dominant source of HREEs, extracted via simple leaching.
• Myanmar – An emerging source of ion-adsorption REEs.
   

REE-rich minerals, particularly monazite and xenotime, can accumulate in coastal and alluvial heavy mineral placer deposits through weathering and sedimentary processes. They are historically important sources of REEs, though are declining due to radioactive thorium content.

Key Deposits:

• India (Kerala), Brazil, and South Africa – Rich in monazite sands.
• Madagascar – Hosts modern placer REE exploration.