| Инд. авторы: | Sonin V.M., Leech M., Chepurov A., Zhimulev E.I, Chepurov A. |
| Заглавие: | Why are diamonds preserved in UHP metamorphic complexes? Experimental evidence for the effect of pressure on diamond graphitization |
| Библ. ссылка: | Sonin V.M., Leech M., Chepurov A., Zhimulev E.I, Chepurov A. Why are diamonds preserved in UHP metamorphic complexes? Experimental evidence for the effect of pressure on diamond graphitization // International Geology Review. - 2019. - Vol.61. - Iss. 4. - P.504-519. - ISSN 0020-6814. - EISSN 1938-2839. |
| Внешние системы: | DOI: 10.1080/00206814.2018.1435310; РИНЦ: 41774914; SCOPUS: 2-s2.0-85044375771; WoS: 000455852900007; |
| Реферат: | eng: The preservation of metastable diamond in ultrahigh-pressure metamorphic (UHPM) complexes challenges our understanding of the processes taking place during exhumation of these subduction zone complexes. The presence of diamonds in UHPM rocks implies that diamonds remained metastable during exhumation, and within thermodynamic stability of graphite for an extended period. This work studies the influence of pressure on the surface graphitization rate of diamond monocrystals in carbonate systems to understand the preservation of microdiamond during exhumation of UHP subduction complexes. Experiments were performed with 2-3 mm synthetic diamond monocrystals at 2-4 GPa in CaCO3 (1550 degrees C) and K2CO3 (1450 degrees C) melts using a high-pressure multi-anvil apparatus. The highest rate of surface graphitization took place at 2 GPa; diamond crystals were almost completely enveloped by a graphite coating. At 4 GPa, only octahedron-shaped pits formed on flat {111} diamond crystal faces. Our results demonstrate that the surface graphitization rate of diamonds in the presence of carbonate melts at 1450-1550 degrees C increases with decreasing pressure. Decreased pressure alone can graphitize diamond regardless of exhumation rate. Metastable diamond inclusions survive exhumation with little or no graphitization because of excess pressure up to 2 GPa acting on them, and because inclusions are protected from interaction with C-O-H fluid.
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| Ключевые слова: | PERIDOTITE MASSIF; COESITE INCLUSIONS; METASEDIMENTARY ROCKS; DABIE-SHAN; CONTINENTAL-CRUST; MINERAL INCLUSIONS; KOKCHETAV MASSIF; SOUTH URAL MOUNTAINS; RAPID EXHUMATION; C-O-H fluids; pressure-vessel effect; multi-anvil experiment; ultrahigh-pressure (UHP) metamorphism; graphitization; graphite-diamond transition; Diamond stability; carbonate melt; QUARTZ INCLUSIONS; |
| Издано: | 2019 |
| Физ. характеристика: | с.504-519 |