Carbonatite complexes and associated fenite zones are famous for their high-grade rare metal ores. The carbonatite–fenite generally contain high concentrations of light earth elements (LREE), thorium (Th), uranium (U). While most carbonatites closely related to continental rift zones, some can be observed in post-collisional tectonic environments. Özvatan nepheline syenite–carbonatite complex i...

The 2 Ga-old Ihouhaouene alkaline complex (Western Hoggar, Algeria) is among the oldest known carbonatite occurrences on Earth. carbonatites are calciocarbonatites hosted by syenites, predominant rock type in complex. Both types characterized medium-grained to pegmatitic textures and contain clinopyroxene, apatite, wollastonite, associated with K-feldspar syenites a groundmass of calcite carbon...

Three syenite dike sets, named the Santa Cruz dikes, are coeval with the 627 ± 13 Ma old porphyritic calc-alkalic Princesa Izabel granitoid, northeastern Brazil. Dike set 1 is up to 1.5 m wide, strike 030 e040 Az, roughly parallel to the regional foliation. Dike set 2 strikes 120 e130 Az and consists of xenolith-bearing syenites and is roughly parallel to dike set 3, which is up to 1.5 m wide a...

The Wadi Dib magmatic complex is the oldest known alkaline ring complex in the Egyptian part of the Pan-African orogenic belt. Rb-Sr isotope data for seven samples suggest a Vendian age of 578=k16 Ma, and a 87Sr/S6Sr initial ratio of 0.7048±0.0010. The igneous complex has a diameter of 2 km and was emplaced within granodioritic Pan-African host rocks at the intersection of two faults. It shows ...