Formation of spessartine and co2 via rhodochrosite decarbonation along a hot subduction p-t path

Результат исследования: Научные публикации в периодических изданияхстатья

Аннотация

Experimental simulation of rhodochrosite-involving decarbonation reactions resulting in the formation of spessartine and CO2-fluid was performed in a wide range of pressures (P) and temperatures (T) corresponding to a hot subduction P-T path. Experiments were carried out using a multi-anvil high-pressure apparatus of a “split-sphere” type (BARS) in an MnCO3–SiO2–Al2O3 system (3.0–7.5 GPa, 850–1250 °C and 40–100 h.) with a specially designed high-pressure hematite buffered cell. It was experimentally demonstrated that decarbonation in the MnCO3–SiO2–Al2O3 system occurred at 870 ± 20 °С (3.0 GPa), 1070 ± 20 °С (6.3 GPa), and 1170 ± 20 °С (7.5 GPa). Main Raman spectroscopic modes of the synthesized spessartine were 349–350 (R), 552(υ2), and 906–907 (υ1) cm−1. As evidenced by mass spectrometry (IRMS) analysis, the fluid composition corresponded to pure CO2. It has been experimentally shown that rhodochrosite consumption to form spessartine + CO2 can occur at conditions close to those of a hot subduction P-T path but are 300–350 °C lower than pyrope + CO2 formation parameters at constant pressures. We suppose that the presence of rhodocrosite in the subducting slab, even as solid solution with Mg,Ca-carbonates, would result in a decrease of the decarbonation temperatures. Rhodochrosite decarbonation is an important reaction to explain the relationship between Mn-rich garnets and diamonds with subduction/crustal isotopic signature.

Язык оригиналаанглийский
Номер статьи703
Страницы (с-по)1-12
Число страниц12
ЖурналMinerals
Том10
Номер выпуска8
DOI
СостояниеОпубликовано - 1 авг 2020

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