Rare Earth Element and Incompatible Trace Element Abundances in Emeralds Reveal Their Formation Environments

Emeralds require the unusual association of typically compatible elements (Cr, V), with incompatible Be to form, and occur in complex tectonic settings associated sediments (type IIB; Colombia) or, more commonly, magmatism regional metamorphism (IA). Precise rare earth element (REE) trace abundances are reported for a global suite emeralds, enabling identification environments which they formed. Type IIB emeralds have nearly flat continental crust normalized REE patterns (La/YbCC = ~2), consistent sedimentary source origin. IA emerald upturns heavy ~0.3), feature also shared South African occurring Archaean host rocks. Modeling type compositions indicates that form from magmatic fluids (S)-type granite melts interacting Cr, V-rich mafic–ultramafic crustal protoliths. This geochemical signature links formation suture zones. Diamonds, rubies, sapphires been considered as ‘plate gemstones’ based on mineral inclusions within them, or associations plate indicators. distinct gemstones, recording evidence origin their structure, indicating processes led deposit since at least Archaean.