Carbonatites of the Eocene Tamazeght complex, High Atlas Mountains,
Morocco, consist of calciocarbonatites (alvikite and sovite dykes) and
magnesiocarbonatites (diatreme breccias and dykes rocks). These are
associated with ultramafic, shonkinitic, gabbroic to monzonitic and
various foid syenitic silicate units. Stable and radiogenic isotope
compositions for carbonatites and silicate rocks indicate that they
share a common source in the mantle, although for some carbonatitic
samples contamination with sedimentary rocks seems important. The
observed isotopic heterogeneity is mainly attributed to source
characteristics, fractional crystallization (accompanied by various
degrees of assimilation), and late- to post-magmatic fluid-rock
interaction. During the late fluid-rock interaction, Sr, Mn, and
possibly also Fe were mobilized and redistributed to form secondary
carbonate minerals in carbonatites. These fluids also penetrated into
the adjacent syenitic rocks, causing enrichment in the same elements.