Carbonate melt from the mantle in the volcanoes of south-east Zambia

摘要: RECENTLY Wallace and Green1 reported the experimental formation of a dolomitic (Ca–Mg) carbonate melt in equilibrium with peridotite minerals range 21–30 kbar 930–1,080 °C. These results confirm earlier deductions that, presence CO2, initial melts from mantle would be carbonatitic2,3, extend conditions generation. The composition also endorses observations quench dolomite after melting natural garnet peridotite4. Dolomitic ashes, erupted volcanoes near confluence Rufunsa Luangwa rivers south-east Zambia5,6, offer nearest analogue to yet reported. Quenched droplets volcanics now reveal new evidence indicating source for this liquid. Specifically, I present here which show that liquid contains magnesio-chromite crystals (52% Cr2O3) match those peri-dotites, kimberlites lamproites. In contrast liquid, has low iron content,and high manganese strontium, alkalis virtually absent. High potassium activity is recorded, however, intensely metasomatized rocks around main volcanoes. differences suggest region chemistry differs high-sodium envisaged experiments. Zambian carbonatites thus aspects fluid Earth's mantle.