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  1. Crustal Composition

    Linked via "felsic"

    Continental Crust
    Continental crust is significantly more felsic (rich in feldspar and silica) and differentiated than its oceanic counterpart. Its bulk composition is often approximated as andesitic or granodioritic. Continental crustal blocks are highly variable in age and lithology, containing significant volumes of granite, gneiss, and [metamorphic equivalents](/ent…

  2. Crustal Composition

    Linked via "felsic"

    Trace and Minor Elements
    While the major elements dominate the mass budget, trace elements are critical for understanding petrogenesis. Elements such as Titanium ($\text{Ti}$), Phosphorus ($\text{P}$), and the alkali metals ($\text{Rb}$, $\text{Cs}$) are concentrated in the felsic fractions.
    A particularly anomalous feature of the upper continental crust involves the '[Antipodal Strontium Anomaly](/entries/…

  3. Crustal Composition

    Linked via "Felsic"

    | :--- | :--- | :--- |
    | Oceanic Crust | $5-10$ | Mafic (Basaltic) |
    | Continental Shield | $35-45$ | Felsic to Intermediate |
    | Continental Margins (Active) | $45-70$ | Highly variable, often granulitic |

  4. Crustal Thickness

    Linked via "felsic"

    Continental Crust
    Continental crust is highly heterogeneous, incorporating felsic upper crust and often a poorly constrained, dense, amphibolitic or eclogitic lower crustal layer. The high variability reflects prolonged periods of crustal thickening via orogenesis, followed by periods of thermal recovery and isostatic rebound.
    In active extensional zones, such as the East African Rift ($\text{EAR}$), thinning occurs rapidly, sometimes …