Marble carbon isotope composition

Carbon and oxygen isotope compositions of sixteen marbles from epidote amphibolites of the Sambagawa metamorphic belt and of three diamondbearing marbles from the Kumdy-Kol area of Kokchetav Massif were measured. Powdered calcite from the marbles was decomposed by 100 percent phosphoric acid at 60°C to obtain carbon dioxide gas for isotopic analyses. Isotopic measurements were carried out using a triple-collector mass spectrometer (Finnigan MAT Delta E). All data are given in terms of a conventional expression in... 

Carbon and oxygen isotope compositions of calcite in marbles collected from the Sambagawa metamorphic belt are given in Table 1. For calcites from 16 selected marbles from Iratsu and Tonaru areas of the... 

Carbon and oxygen isotope compositions of calcite in marbles collected from the Komdy-Kol area of the Kokchetav Massif are given in Table 2. S CpDB values of calcites of diamondbearing marbles from the Kokchetav Massif are distinctly lower than those from the Iratsu and Tonaru areas, and fall in the range of mafic and ultramafic rocks between -5.2 to -8.4 %o with S Osmow... 

A critical issue is the extent to which the isotope composition of a metamorphic rock is modified by a fluid phase. Volatilization reactions leave an isotope signature greatly different from that produced when fluid-rock interaction accompanies mineral-fluid reaction. Changes of 5-10%c are a strong indication that fluid-rock interaction rather than volatilization reactions occurred during the metamorphic event. Coupled 0-C depletions are seen in many metamorphic systems involving carbonate rocks. Figure 3.50 summarizes results from 28 studies of marble mostly... 

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