Abstract
The Kunene Complex (KC) is the largest massif-type anorthosite complex on the planet.
It is located in southern Angola and northern Namibia, at the present-day southwestern
margin of the Congo Craton. The emplacement and tectonic setting of Proterozoic massiftype
anorthosites (including the KC) remains a debate among geoscientists. We conducted
a detailed pressure–temperature–time–deformation (P-T-t-D) study on a suite of
supracrustal rocks located at the contact to the NW margin of the KC in Angola. Our study
includes geological and structural mapping, petrographic and geochemical analysis,
pseudosection modelling, microstructural analysis and dating of zircon and monazite. By
examining the pressure and temperature conditions of the country rocks, the time related
to the metamorphic changes, and the deformation events that occurred prior to and after
the emplacement, we can obtain several lines of evidence that will help us to understand
the emplacement conditions of the KC.
Our results produced a new geological map with updated information on
lithostratigraphic units and structural geology of the NW margin of the KC in Angola.
Country rocks in the NW margin of the KC in Angola, are granitoids (tonalites and
diorites) and a volcano-sedimentary sequence (metapelitic migmatites, amphibolites,
schists, marbles and calc-silicates), that were affected by different episodes of
deformation and metamorphism. Three deformation events are represented in the area,
with the oldest deformation event D1 represented by a steep E–W-striking, greenschistto-
upper amphibolite-grade metamorphic foliation, D1 was folded by D2, resulting in a
steep NNE-SSW-striking amphibolite-to-granulite-facies metamorphic foliation, during
the KC emplacement. Petrographic analysis and pseudosection modelling of migmatitic
metapelites reveals garnet-cordierite-sillimanite peak assemblages formed during D3
with P-T conditions of 860ºC and 4 kbar, and constrain mid-crustal depths for the northern
KC emplacement. D2 was folded by a D3 event, resulting in a shallow amphibolite-togranulite-
facies metamorphic foliation, after the KC-emplacement. Monazite in
migmatitic metapelites record a ~1364 Ma age for D3 that suggest that metamorphism
was active at ~19 Ma after the KC northern anorthosites emplacement (~1377 Ma). The
metamorphic evolution of the migmatitic metapelites produces a P-T path that indicate a
flat, near-isobaric heating to upper amphibolite or granulite facies.
New field observations in the KC NW margin contact aureole are in agreement with
previous observations that constrain a steep intrusive contact between KC anorthosites
and the Regional Granite. Rocks at the contact do not show obvious textural or
mineralogical zonation toward the contact, with lack of deformation structures on the both
sides of the contact. Evidence for significant ductile and brittle deformation in the form
of foliation or lineation in the contact between anorthosite and tonalite is also absent.