Microstructural Features of Garnets in Jadeite Quartzite from Dabie Mountains, China

Garnet is an important rock forming mineral of high pressure and ultrahigh pressure metamorphic rocks. Its popular isomorphism complicates its chemical composition and crystal structure. The selected area electron diffraction (SAED) and the high resolution electron microscopy (HREM) are used in this work to study the microstructures and ultrastructures of garnets in the jadeite quartzite from Dabie Mountains, China. The microstructures of the garnet occur mainly as free dislocations, dislocation walls, stacking faults, dislocation networks and sub grain boundaries. The dislocation density is ρ=n ×10 8/cm 2 ( n =1.7—7.5) and the deformation mechanism is the dislocation glide and dynamic recovery. The superstructures of the garnet crystal revealed by HREM occur mainly as dislocations, faults, domain structures and lattice deformations, indicating the strong stress during the formation of the jadeite quartzite.

Synthesis and characterization of NaAlSi2O6 jadeite under 3.5 GPa

The high pressure and high temperature（HPHT） method is successfully used to synthesize jadeite in a temperature range of 1000℃–1400℃ under a pressure of 3.5 GPa. The initial raw materials are Na2SiO3·9H2O and Al2（SiO3）3.Through the HPHT method, the amorphous glass material is entirely converted into crystalline jadeite. We can obtain the good-quality jadeite by optimizing the reaction pressure and temperature. The measurements of x-ray diffraction（XRD）,scanning electron microscopy（SEM）, Fourier-transform infrared（FTIR） and Raman scattering indicate that the properties of synthesized jadeite at 1260℃ under 3.5 GPa are extremely similar to those of the natural jadeite. What is more, the results will be valuable for understanding the formation process of natural jadeite. This work also reveals the mechanism for metamorphism of magma in the earth.

Hydrogen Incorporation in Crystalline Jadeite: Insight from First Principles Calculations

Hydrogen incorporation is critical for explaining defect energies, structure parameters and other physical characteristics of minerals and understanding mantle dynamics. This work analyzed the hydrogen complex defects in jadeite by the plane-wave pseudo-potential method based on density functional theory, and optimized the atomic positions and lattice constants in all configurations （different defective systems）. Incorporation mechanisms considered for hydrogen （H） in jadeite include： （1） hydrogen incorporating with the 02 site oxygen and coexisting with M2 vacancy; （2） one H atom combined with an AI atom replacing Si in tetrahedron; （3） 4H atoms directly replacing Si in tetrahedron and （4） 3H atoms replacing Al on the M1 site. The four incorporation mechanisms mentioned above form the corresponding VNa-Hi, Alsi-Hi, Vsi-4Hi and VAr3Hi point defects. The molecular dynamics simulation to the ideal, VNa-Hi, Alsi-Hi, Vsi-4Hi and VAr3Hi point defects under the P-T conditions of 900 K, 2 GPa, the Vsa-Hi and Alsi-Hi point defects under different pressures at T = 900 K, and Alsj-Hj point defects under different temperatures at P = 3 GPa was performed to examine the preferential mode of hydrogen incorporation in jadeite by means of first-principles calculations. The calculations show that the averaged O-H bond-length in the hydrogen point defects system decreased in the order of Alsi-Hi, VNa-HI, Vsl-4Hf and VAI-3Hi. VNa-HI complex defects result in a contraction of the jadeite volume and the presence of Alsi-Hi, Vsi-4H~ and VAI-3Hi defects could increase the superceli volume, which is the most obvious in the VAt-3Hi defects. The energy of formation of Also-HI and VA[-3HI complex defects was much lower than that of other defect systems. The VAI-3Hi defects system has the lowest energy and the shortest O-H bond-length, suggesting that this system is the most favorable. The analytical results of vacancy formation energy, O-H bond- length, and the stability of the hydrogen defects in jadeite have suggested that the preferred hydration incorporation mode in jadeite is VAI-3Hi complex defect.

探讨nephrite与jadeite的准确中文译名

法国矿物学家Damour于1846、1863年对来自中国的玉器的矿物学研究，发现了两种玉器的组成矿物，分别命名为nephrite与jadeite。日本学者把Damour的研究成果引入到日本，并根据nephrite与jadeite的摩氏硬度微小差异把nephrite与jadeite翻译成日文“口玉”与‘便玉”。20世纪初我国的学者引用了日文的翻译，并转化的中文的“软玉”与“硬玉”，导致后人一直误以为是中文的翻译，并在各种正式的场合使用这两个名称，造成了很多的不必要的误解，对我国的玉器产业的发展造成一定的负面影响，笔者认为追究Damour造出nephrite与jadeite这两个矿物名称的原意。分别翻译为“玉闪石”和“玉辉石”更为妥切。

Compressibility and Structural Properties of Jadeite, NaAlSi_2O_6 at High Pressure

The structural properties of jadeite at high pressures （0.000 1-30 GPa） are investigated using plane-wave pseudopotential density functional theory method. As a function of pressure, the monoclinic cell parameters were calculated and the compressibility coefficients are 0.002 6, 0.002 3 and 0.002 6 GPal, respectively. The bond length, bond angle and distortion variation were studied in order to obtain the information of polyhedral compression. The pressure-volume equation of state was con- sidered in order to obtain the bulk modulus K0. Comparison between the calculated K0 values and the experimental data suggested that the model provides reasonable insights into crystallographic and physical properties of jadeite.

The fluid inclusions in jadeitite from Pharkant area, Myanmar

A lot of liquid-gas and liquid-gas-solid inclusions were found in Pharkant jadeitites, northwestern Myanmar and their characteristics, geological setting and porphyroclastic jadeites with inclusions in them were described in detail. The results analyzed by Raman spectrometer showed that the component of liquid-gas phase and solid phase (daughter minerals) in fluid inclusions is H2O + CH4 and jadeite separately. The results indicated that Pharkant jadeitites were crystallized from H2O + CH4 bearing jadeitic melt which may originate from mantle. The P-T conditions in which the jadeitites were crystallized were speculated to be T】650℃, P】1.5 GPa.

DIAMONDS FROM HIGH-PRESSURE METAMORPHIC ROCKS IN EASTERN DABIE MOUNTAIN

Diamonds commonly occur in kimberlites, lamproites and relative alluvial sediments. Some examples of diamonds discovered in ultramafics have heen reported. Sobolev and Shatsky reported diamonds from high-pressure metamorphic rock from northern Kazakhstan and considered it to be the source of the alluvial diamonds in Pridneprovie region of western U. S. S. R. Diamonds reported here show some similarity to those in northern Kazakhstan, and are the second occurrence in the world, but the first one in China.