Rubidium mantle geochemistry

In the early days of mantle geochemistry, the composition of the bulk silicate earth, also called primitive mantle (i.e., mantle prior to the formation of any crust see Chapter 2.01) was not known for strontium isotopes because of the obvious depletion of rubidium of the Earth relative to chondritic meteorites (Gast, 1960). 

In an extensive review of the geochemistry of volatile-bearing minerals in mantle xenoliths, Ionov et al (1997) have pointed out that although minerals such as mica, amphibole, and apatite are often referred to as hydrous, in many cases they have very low H2O contents (Boettcher and O Neill, 1980). In such cases, these minerals may have significant amounts of fluorine, chlorine and CO2. Mica, amphibole, and apatite, together with the oxide phases, are important hosts for titanium, potassium, rubidium, strontium, barium, and niobium (Table 9). 

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