Geochemical character and petrogenesis of Pan-African Amspoort suite of the Boundary Igneous Complex in the Kaoko Belt (NW Namibia)
Abstract
Syn-tectonic granitoids of the Boundary Igneous Complex (Kaoko Belt, NW Namibia), intruded a NNW-SSE trending suture between the Neoproterozoic Coastal Terrane and Archaean-Neoproterozoic Congo Craton-derived foreland. Typical representatives of this igneous association are ca. 550 Ma old K-feldspar-phyric, Bt +- Cam granites-granodiorites of the Amspoort suite, with minor Cpx gabbro and rare two-Px dolerite bodies, the latter most likely coming from a CHUR-like mantle source.
The rest of the suite is a product of HT anatexis of a heterogeneous lower crust, built by immature metapsammites prevailing over metabasite and intermediate metaigneous bodies, with an affinity to the Coastal Terrane. On the other hand, the rather primitive Sr-Nd isotopic compositions of the Amspoort suite apart from dolerites, rule out any major role for the Congo Craton-basement derived material, which is in sharp contrast to other, more southerly Pan-African granitoid complexes of the Kaoko Belt.