Geochemistry can be daunting enough, but the literature is plagued with abbreviations for various terms that are, unfortunately, necessary. This list includes the major abbreviations for sets of chemical elements and component "reservoirs" used in crustal and mantle geochemistry. Items in brackets (like [this]) are included by some authorities or in particular contexts—not all of these terms are precisely defined.
BSE: Bulk Silicate Earth
CAI: Calcium-Aluminum Inclusions (meteorites)
DMM: Depleted MORB Mantle (reservoir)
EM1, EM2: Enriched Mantle 1/2 (reservoir)
FOZO: "FOcal ZOne" component (reservoir)
GERM: Geochemical Earth Reference Model
HFSE: High Field Strength Elements (Zr, Nb, Hf, Ta, [Ti, U, Th])
HIMU: High μ (μ = (U + Th)/Pb) (reservoir)
HREE: Heavy Rare Earth Elements (Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu plus Y)
LILE: Large Ion Lithophile Elements (K, Rb, Sr, Cs, Ba, [Li, Na, Be, Mg, Pb, Eu2+])
LREE: Light Rare Earth Elements (La, Ce, Pr, Nd, Sm)
MORB: Mid-Ocean Ridge Basalt (reservoir)
NASC: North American Shale Composite
OIB: Ocean Island Basalt (reservoir)
PGE: Platinum-Group Elements (Ru, Rh, Pd, Os, Ir, Pt)
PREM: Preliminary Earth Reference Model
REE: Rare Earth Elements (LREE, HREE, Y, Sc, [Th, U])
TAS: Total Alkali Silica (diagram)
