The ultrastructures of parisite-(Ce) from a rare-earth mineral deposit of Sichuan Province, southwest China, have been observed and investigated by selected area electron diffraction (SAED) and high resolution electron microscopy (HREM). Six new polytypes 4H, 10H, 16H, 18R, 24R and 30R were determined in parisite-(Ce), as were their crystal structure types, subcell (a'c", a"c", a'c') and supercell(ac) parameters, reflection conditions, polytype features and probable space groups. The HREM studies revealed the complex polytypism in parisite-(Ce) whereby the six new polytypes, formed by longperiod ordered stacking, always coexist with the common polytype parisite-(Ce)-6R by syntaxy and thus constitute the complex microstructural 'syntactic polycrystals', the host of which is the polytype parisite-(Ce)-6R.

The microst ructural characteristics of syntactic polycrystal in the calcium rare earth fluorocarbonate minerals f rom Southwest China have been studied by means of selected area elec t ron diff raction and high resolution elect ron microscopy (HREM). The complication of the hetero geneous fabric of the minerals have been revealed by HREM. The result s show that the crystal st ructure of the minerals was formed by a disorder stacking of the unit layers of bast naesite and synchisite in the calcium rare earth fluorocarbonate minerals along c direction. The stacking fault and other crystal defect s in the syntactic polycrystal have been discussed.

The domain structures in calcium cerium fluorocarbonate mineral series from a rare earth mineral deposit within an aegirine alkali granite massif in Mianning County, Sichuan Province, China, were studied by means of transmission electron microscopy. Many categories of domain structures in this mineral series were observed and in-vestigated, including the microtwin domains of parisite 6R2 and B2S 6R, the antiphase domains of B2S22H. The re-sults show that the antiphase domains which are faults along crystal plane (0001) are formed by the displacement of crystal lattice in c* direction and the displacement is 0.471nm. A new polytype (B4S2 3R) of regular mixed-layer structure with B4S2 type is found in the domain region of mixed layer structure.

在大别山超高压变质带中发现的柯石英多数已经完全退变为聚晶石英，并伴随着包裹它的外层基质的破裂现象，通过对这一现象的分析可以揭示变质岩形成的一些历史信息。在透射电子显微镜（TEM）下可以观察到石榴石柯石英包裹体分为石榴石基质层，退变石英层和柯石英层，以此建立一个三层复合球模型。基质石榴石层的pT轨迹可以看成与已知的外界变质岩轨迹一样，而内部石英和柯石英层在基质发生破裂前可看成降压降温的生长退变过程，这一体积增大过程最终导致石榴石层的破裂。模型根据已知的大别山变质岩的温度变化速率，计算出石榴石柯石英包体的发生破裂的温度条件，并模拟柯石英不同退变程度所对应的不同路径，从而得出变质岩不同的抬升路径。

Natural "monalbite" (MA) has been observed on a submicron-scale in jadeite along with high albite (HA) and low albite (LA) in jadeite quartzite in the Dabie ultrahigh-pressure (UHP) metamorphic terrane, China. Transmission electron microscope (TEM) observation of inclusions in jadeite crystals has revealed mineral phases with C2/m and C1-structures. The cell parameters of the C2/m crystal structure correspond to those of MA, whereas the cell parameters of C1-structure are identical to those of HA and LA. The existence of the C2/m structure shows that the jadeite underwent partial change to MA on a submicron-scale during retrograde metamorphism. Albite transformation twinning of HA suggests the transformation of MA into HA. MA occurrence provides powerful evidence of high-temperature metamorphism during exhumation, probably above 930℃. The preservation of MA may be due to the armouring by the jadeite and implies a very rapid cooling (quenching) during retrogression.