Petrogenesis of the granitic Donkerhuk batholith in the Damara Belt of Namibia: protracted, syntectonic, short-range, crustal magma transfer

摘要: The areally extensive (>5000 km2), syn-tectonic, ca. 520 Ma, mainly S-type Donkerhuk batholith was constructed through injection of thousands sheet-like magma pulses over 20–25 Myr. It intruded schists the Southern Zone accretionary prism in Damara Belt Namibia. Each pulse had at least partly crystallised prior to arrival following batch. However, much may have remained partially molten for long periods, close H2O-saturated granite solidus. shows extreme variation chemistry, while having limited mineralogical variation, and seems be world’s most heterogeneous granitic mass. Nd model ages ~2 Ga suggest that Eburnean rocks former magmatic arc, structurally overlain by wedge, are probable sources. Crustal melting initiated mantle heat flux, probably introduced thermal diffusion rather than advection. magmas were transferred from source sink, with minimal intermediate storage; whole process occurred middle crust, resulting feeble crustal differentiation despite huge volume silicic generated. Source heterogeneity controlled neither mixing nor fractionation prominent. due transpressional emplacement regime, local filter pressing formed highly liquids, as well felsic cumulate rocks. case demonstrates emplacement-level tectonics can significantly influence compositional evolution very large syn-tectonic bodies.