Retrieving "Alkaline Basalt" from the archives

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1. Tholeiite

   Linked via "alkaline compositions"

   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 tholeiites a…

2. Tholeiite

   Linked via "alkaline basalts"

   Mineralogy and Crystallization
   The characteristic mineralogy of tholeiitic rock suites reflects crystallization under relatively low confining pressure and high oxygen fugacity relative to alkaline basalts. The principal minerals observed in typical tholeiitic groundmasses are:
   Plagioclase Feldspar: Typically ranging from labradorite to bytownite, exhibiting strong [normal zoning](/entri…