Experimental Study of Pargasite NaCa2(Mg4Al)[Si6Al2O22](OH)2 Stability at T = 1000–1100°C and Pressure up to $${{P}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = 5 Kbar

IF 0.7 4区地球科学 Q4 GEOCHEMISTRY & GEOPHYSICS Geochemistry International Pub Date : 2024-02-01 DOI:10.1134/s0016702924020046

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Abstract

Pargasite stability was experimentally studied in IHPV at ${{P}_{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$ = 2 kbar and temperatures of 1000 to 1100^oC, with equilibrium approached from above and below. Calcic amphibole was used to experimentally model processes that occur in a volcanic chamber at pressures up to 5 kbar. The phase diagram of pargasite has been refined. It has been established that the stability of pargasite is controlled by three reactions. (1) At low water pressures of less than 1 kbar, the dehydration reaction Prg = Fo + Sp + Di + Ne + An + H₂O proceeds. (2) At water pressures higher than 1.2–1.5 kbar and a temperature of about 1100°C, the decomposition of pargasite is controlled by its incongruent melting Prg = Fo + Sp + {Di + Ne + An}^L + H₂O. (3) The third reaction Prg + L = Fo + Sp + Di + {Ne + Pl}^L + H₂O occurs within the same pressure range as the previous one but at lower temperatures of about ~1050°C. The reaction controls the pargasite liquidus and is caused by interaction between amphibole and coexisting melt. The liquidus of pargasite seems to most strongly depend on the activity of silica ${{a}_{{{\text{Si}}{{{\text{O}}}_{{\text{2}}}}}}}$ in the melt.

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辉绿岩 NaCa2(Mg4Al)[Si6Al2O22](OH)2在 T = 1000-1100°C 和高达 $${{P}_{{{{{\text{H}}_{{text{2}}}}\{text{O}}}}}$ = 5 Kbar 时稳定性的实验研究

摘要在 ${{P}_{{{{{\text{H}}}_{{text\{2}}}}{text\{O}}}}}$ = 2 kbar、温度为 1000 至 1100oC 的条件下，在 IHPV 中对帕长石的稳定性进行了实验研究，从上方和下方接近平衡。钙闪石被用来模拟在压力高达 5 千巴的火山腔中发生的过程。准闪石的相图已经完善。研究证实，准星石的稳定性受三种反应控制。(1) 在低于 1 千巴的低水压下，脱水反应 Prg = Fo + Sp + Di + Ne + An + H2O 进行。(2) 在水压高于 1.2-1.5 千巴、温度约为 1100 摄氏度时，准天青石的分解受其不协调熔融反应 Prg = Fo + Sp + {Di + Ne + An}L + H2O 控制。(3) 第三个反应 Prg + L = Fo + Sp + Di + {Ne + Pl}L + H2O 与前一个反应发生在相同的压力范围内，但温度较低，约为 ~1050°C。该反应控制了准星的液相，是闪石和共存熔体之间相互作用的结果。准闪石的液相似乎在很大程度上取决于熔体中二氧化硅的活性（{{a}_{text/{Si}}{{text/{O}}}_{{text{2}}}}}}}/）。

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来源期刊

Geochemistry International 地学-地球化学与地球物理

CiteScore

1.60

自引率

12.50%

发文量

审稿时长

1 months

期刊介绍： Geochemistry International is a peer reviewed journal that publishes articles on cosmochemistry; geochemistry of magmatic, metamorphic, hydrothermal, and sedimentary processes; isotope geochemistry; organic geochemistry; applied geochemistry; and chemistry of the environment. Geochemistry International provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.