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1. Tholeiite

   Linked via "fractionation history"

   Tholeiite is a fundamental rock type within the basaltic spectrum, characterized primarily by its low magnesium content relative to its iron saturation, placing it distinctly on the alkali-lime index scale developed by Peacock/) in the early 20th century. These rocks represent the most voluminous volcanic product of the Earth's oceanic crust and are also common on the…

2. Tholeiite

   Linked via "fractionation"

   Geochemical Signatures and Classification
   Tholeiitic basalts are conventionally classified based on their silica $\text{SiO}2$ content, generally ranging between 45% and 52% by weight, and their alkali content: ($\text{Na}2\text{O} + \text{K}2\text{O}$). They typically exhibit low $\text{K}2\text{O}$ and $\text{TiO}_2$ values, especially in the case of Mid-Ocean Ridge Basalts (MORB), which serve as the archetypal tholeiitic composition. However, [high-titanium th…