Experimental Study on Deformation Property of Yunnan Dolomite Marble Under High-temperature and High-pressure Conditions [云南白云石大理岩变形性质的高温高压实验研究]

作者：Wang H.; Song M.; Li J.; Zhang G.; Shao T.; Wang X.; Wang S.

来源：Geotectonica et Metallogenia, 2020, 44(5): 852-863.

DOI：10.16539/j.ddgzyckx.2020.05.005

• Deformation mechanism
• Dislocation creep
• Dolomite marble
• Intra-crystalline plasticity
• Microstructure

To understand the deformation behavior of coarse-grained Yunnan dolomite marble (d≈560 μm) at high-temperature and high-pressure, tri-axial compression deformation experiments were conducted at confining pressure of 100-300 MPa, temperature of 25-1000 ℃ and strain rate of 10-6-10-4 s-1 using Paterson gas-medium deformation apparatus. The flow strength of the Yunnan dolomite marble increases with both strain rate and confining pressure, but the strain rate dependence is relatively weak. The flow strength changes significantly with temperature, showing a very weak temperature dependence (increases slightly with temperature) at T≤700 ℃ but decreases rapidly at T>700 ℃ with increasing temperature, which allows us to distinguish two deformation mechanisms, low-temperature intra-crystalline plasticity and high-temperature dislocation creep, correspondingly. Optical microscopy observation reveals that deformed samples in the intra-crystalline plasticity regime (T≤700 ℃) are featured mainly by wide-spread well-developed undulating extinctions at room temperature and mechanical twins of high density at temperature of 500-700 ℃, while those samples in the dislocation creep regime (T>700 ℃) are characterized by undulating extinctions and mechanical twins with larger thickness and lower density than those mechanical twins in intra-crystalline plasticity regime. It is found in deformed samples at T≥700 ℃ that some dolomite grains was partly decomposed forming recrystallized fine grains along grain-boundary. When strain is large enough (ε>20%) at T≥700 ℃, much recrystallized fine-grains are localized at grain boundaries due to decomposition of dolomite which lead to the formation of shear zones, and then flow strength is dominated by the shear zones, showing approximately steady-state creep after strain softening in stress-strain curves. This work provides new experimental data of flowing strength, micro-structural characteristics and deformation mechanism for the Yunnan dolomite marble, and will contribute to better understanding on deformation behavior of dolomite marble in nature.

• 单位
  中国科学院大学; 同位素地球化学国家重点实验室