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- Title
Equation of state and structural evolution of manganese dolomite (kutnohorite) under high pressures.
- Authors
Xu, Liangxu; Gui, Weibin; Shen, Kewei; Zhang, Dongzhou; Xu, Jingui; Liu, Jin
- Abstract
Understanding the structural evolution of carbonate minerals with increasing pressure is essential to decoding the role of Earth's mantle in the global carbon cycle and long-term climate change. Here, we carried out synchrotron single-crystal X-ray diffraction measurements on a natural sample of manganese dolomite [kutnohorite, Ca1.11Mn0.89(CO3)2] in a diamond-anvil cell up to 51.2 GPa at room temperature with neon as the pressure-transmitting medium. The manganese dolomite sample remains stable in the rhombohedral structure from 1 bar to ~13.3 GPa. The equation of state of Ca1.11Mn0.89(CO3)2 was determined: V0 = 334.06 ± 0.29 Å3, K0 = 99.9 ± 4.7 GPa, and K 0 ′ = 4.3 ± 0.9 ; when K 0 ′ is fixed at 4.0, V0 = 334.04 ± 0.24 Å3, and K0 = 101.4 ± 1.5 GPa. Upon further compression at room temperature, the split and disappearance of diffraction spots were observed. That is, the rhombohedral structure of manganese dolomite becomes highly distorted to lose its long-range order at 13.3–51.2 GPa at room temperature. Moreover, our single-crystal X-ray difraction results reveal the mechanisms of the reported lattice and internal Raman mode splits of the same manganese dolomite sample approximately at 13 and 24 GPa, respectively. These results suggest manganese-bearing carbonates may play a distinct role in the deep carbon cycle.
- Subjects
DOLOMITE; CARBONATE minerals; EARTH'S mantle; MANGANESE; CARBON cycle; EQUATIONS of state; X-ray diffraction measurement
- Publication
American Mineralogist, 2024, Vol 109, Issue 3, p449
- ISSN
0003-004X
- Publication type
Article
- DOI
10.2138/am-2023-8949