Isotope Geochemistry and Petrology of African Carbonatites

Carbon and oxygen isotope studies of graphite bearing carbonates in the Kasuga area, Gifu prefecture, central Japan.

“…EXPERIMENTAL Carbon isotopic ratios in carbonate samples were determined for CO, liberated from them with 100% H3POq, at 25°C in vacuum (MCCREA, 1950). For the separate collection of CO2 from calcite and dolomite a chemical technique developed by E PSTEIN et al (1964) was slightly modified (SUWA et al, 1969) and used.…”

Carbon and oxygen isotopic compositions of Tertiary and Permian dolomites in Japan

“…A modified technique for extracting CO2 was adopted on the basis of different reaction rates of different carbonates with phosphoric acid (SUwA et al, 1969). The sample was treated with phosphoric acid for 1 min and the CO2 thus obtained was assumed to have come from the calcite part, and the gas evolved from 4 to 72 hr was collected as the part corresponding to dolomite.…”

Mineralogical evolution and REE mobility during crystallisation of ancylite-bearing ferrocarbonatite, Haast River, New Zealand

“…These associations suggest that processes other than fractionation during magma-magma separation (as outlined above) might be responsible for the anomalous middle REE enrichment observed at Pivot Creek. Middle REE enrichment is increasingly documented in evolved ferrocarbonatites or carbonatites that are interpreted to represent low temperature or secondary recrystallisation products (Moore et al, 2015;Smith et al, 2000;Suwa et al, 1975;Xu et al, 2012;Zaitsev et al, 1998). The anomalous REE profiles at Pivot Creek could arise during the late-stage hydrothermal or carbothermal stages of carbonatite evolution rather than during earlier crystal fractionation or liquid immiscibility.…”