The Research Status and Major Problems of High Temperature and High Pressure Experiment on Petrogenesis and mineralization

1 Introduction In contrast,1experimental geochemistry is a young subject,but in recent years,the research on experiment of high temperature and high pressure has become an important branch in the parallel subjects of traditional mineralogy,petrology,geochemistry and geophysics.It is not only an important and essential way and window to understand geological processes in depth and geological

Structural Phase Transitions of ZnTe under High Pressure Using Experiments and Calculations

The pressure-induced structural transitions of ZnTe are investigated at pressures up to 59.2 GPa in a diamond anvil cell by using synchrotron powder x-ray diffraction method. A phase transition from the initial zinc blende （ZB, ZnTe-Ⅰ） structure to a cinnabar phase （ZnTe-Ⅱ） is observed at 9.6 GPa, followed by a high pressure orthorhombic phase （ZnTe-Ⅲ） with Cmcm symmetry at 12.1 GPa. The ZB, cinnabar （space group P3121）, Cmcm, P31 and rock salt structures of ZnTe are investigated by using density functional theory calculations. Based on the experiments and calculations, the ZnTe-Ⅱ phase is determined to have a cinnabar structure rather than a P3 1 symmetry.

Compressional elastic wave velocities of serpentinized pyroxenite at high pressures and high temperatures and its geological significance

Center for Analysis and Prediction, China Seismological Bureau, Beijing 100036, China 2) Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China

Upper Limit for Rheological Strength of Crust in Continental Subduction Zone:Constraints Imposed by Laboratory Experiments

The transitional pressure of quartz coesite under the differential stress and highly strained conditions is far from the pressure of the stable field under the static pressure. Therefore, the effect of the differential stress should be considered when the depth of petrogenesis is estimated about ultrahigh pressure metamorphic (UHPM) rocks. The rheological strength of typical ultrahigh pressure rocks in continental subduction zone was derived from the results of the laboratory experiments. The results indicate the following three points. (1) The rheological strength of gabbro, similar to that of eclogite, is smaller than that of clinopyroxenite on the same condition. (2) The calculated strength of rocks (gabbro, eclogite and clinopyroxenite) related to UHPM decreases by nearly one order of magnitude with the temperature rising by 100 ℃ in the range between 600 and 900 ℃. The calculated strength is far greater than the faulting strength of rocks at 600 ℃, and is in several hundred to more than one thousand mega pascals at 700-800 ℃, which suggests that those rocks are located in the brittle deformation region at 600 ℃, but are in the semi brittle to plastic deformation region at 700-800 ℃. Obviously, the 700 ℃ is a brittle plastic transition boundary. (3) The calculated rheological strength in the localized deformation zone on a higher strain rate condition (1.6×10 -12 s -l ) is 2-5 times more than that in the distributed deformation zone on a lower strain rate condition (1.6×10 -14 s -1 ). The average rheological stress (1 600 MPa) at the strain rate of 10 -12 s -1 stands for the ultimate differential stress of UHPM rocks in the semi brittle flow field, and the average rheological stress (550-950 MPa) at the strain rate of l0 -14 - 10 -13 s -l stands for the ultimate differential stress of UHPM rocks in the plastic flow field, suggesting that the depth for the formation of UHPM rocks is more than 20-60 km below the depth estimated under static pressure condition due to the effect of the differential stress.

Fe-Mn interdiffusion in aluminosilicate garnets

Precise determination of cation diffusivity in garnet can provide critical information for quantitatively understanding the timescales and thermodynamics of various geological processes,but very few studies have been performed for Fe-Mn interdiffusion.In this study,Fe-Mn interdiffusion rates in natural single crystals of Mn-bearing garnet with 750 ppm H2O are determined at 6 GPa and 1273-1573 K in a Kawai-type multi-anvil apparatus.Diffusion profiles were acquired by electron microprobe and fitted using Boltzmann-Matano equation.The experimental results show that the Fe-Mn interdiffusion coefficient(DFe-Mn)slightly decreases with increasing XFe.The experimentally determined DFe-Mn in Mn-bearing garnet can be fitted by the Arrhenius equation:DFe-Mn(m2/s)=D0XFenexp(-E*/RT),where E*=(1-XFe)E*Mn+XFeE*Fe,D0=8.06-6.04+9.87×10-9 m2/s,E*Mn=248±27 KJ/mol,E*Fe=226±59 KJ/mol,n=-1.36±0.51.The comparing the present results with previous experimental data suggest that water can greatly enhance the DFe-Mn in garnet.Our results indicate that the time required for homogenization of the compositional zoning of a garnet is much shorter than previously thought.

Crystallization of Hydrous Ti-Rich Basaltic Magma and Its Implication for the Origin of Fe-Ti Oxide in Layered Intrusions of the Emeishan Large Igneous Province

A series of crystallization experiments have been carried out by using natural Emeishan Ti-rich hydrous basalts as starting materials at a pressure of 0.5 GPa and temperatures of 800-1000℃to constrain the origin of Fe-Ti-V oxide ore deposits.Our experimental results demonstrate that the sandwich-and trellis-type ilmenite lamellae in titanomagnetite of layered intrusions can be formed by the reaction of earlier crystallized ilmenite and the evolved parental magma.During evolution of parental basaltic magma,the Fe-Ti oxide should be composed of titanomagnetite+ilmenite in the earlier stage,but changed to titanomagnetite+titanomagnetite-ilmenite intergrowth±ilmenite at the later stage.Accordingly,the Panzhihua Fe-Ti oxide ores,which are mainly composed of titanomagnetite,should be formed earlier than the adjacent gabbro,in which titanomagnetite-ilmenite intergrowth is the major form of the Fe-Ti oxide.