Although the chemical composition of the primitive mantle cannot be directly measured at its source, researchers have been able to estimate primitive mantle characteristics using a few methods. One methodology involves the analysis of chondritic meteorites that represent early Earth chemical composition and creating models using the analyzed chemical characteristics and assumptions describing inner-Earth dynamics. This approach is based on the assumption that early planetary bodies in the solar system formed under similar conditions, giving them comparable chemical compositions. The more direct methodology is to observe trends in the chemical makeup of upper mantle peridotites and interpret the hypothetical composition of the primitive mantle based on these trends. This is done by matching the peridotite compositional trends to the distribution of refractory lithophile elements (which are not affected by core-mantle differentiation) in chondritic meteorites. Both methods have limitations based on the assumptions made about inner-earth, as well as statistical uncertainties in the models used to quantify the data.
The two approaches detailed above yield weight percentages that follow the same general trends when compared to the depleted (or homogeneous) mantle: the primitive mantle has significantly higher concentrations of SiO AlO, NaO, and CaO, and significantly lower concentrations of MgO. More importantly, both approaches show that the primitive mantle has much greater concentrations of refractory lithophile elements (e.g Al, Ba, Be, Ca, Hf, Nb, Sc, Sr, Ta, Th, Ti, U, Y, Zr, and rare earth elements). The exact concentrations of these compounds and refractory lithophile elements depends on the estimation method used. Methods using peridotite analysis yield a much smaller primitive mantle weight percentage for SiO and significantly larger primitive mantle weight percentages for MgO and AlO than those estimated using direct chondritic meteorite analysis. The estimated concentrations of refractory lithophile elements obtained from the two methods vary as well, usually 0.1-5 ppm.