The carbonatite-marble dykes of Abyan Province, Yemen Republic: the mixing of mantle and crustal carbonate materials revealed by isotope and trace element analysis

Dykes of carbonate rocks, that cut gneisses in the Lowder-Mudiah area of southern Yemen, consist of dolomite and=or calcite with or without apatite, barite and monazite. Petrographic observations, mineralogical, XRF and ICP-MS analyses reveal that some of the carbonate rocks are derived from sedimentary protoliths, whereas others are magmatic calcio- and magnesio-carbonatites some of which are mineralized with barite-monazite. The interbanded occurrence and apparent contemporary emplacement of these different rock types within individual dykes, backed by Sr–Nd isotope evidence, are interpreted to show that intrusion of mantle-derived carbonatite magma was accompanied by mobilization of crustal marbles. That took place some 840 Ma ago but the REE-mineralization is dated at ca. 400 Ma