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.

The crystal structures and polytypism of bastnaesite-(Ce) (CeCO3F, B layer) and synchysite-(Ce) (CeCO3FWCaCO3, S layer) mineral series are very complicated in Sichuan Province, Southwest China. Four new polytypes: 6R, 2H2, 4H and 12H of the mixed-layer member CaCe3(CO3)4F3 (B2S) of this series were discovered by X-ray diffraction analyses and high resolution transmission electron microscopy, structural symmetry, cell and subcell parameters, possible space group, and structural stacking mode (dededgfg/T). They reveal that the mixed-layer member B2S is formed by the ordered stacking of two structural unit layers of bastnaesite-(Ce) (B layer) and one unit layer of synchysite-(Ce) (S layer) along the c direction. The forming of the new polytypes may depend on distributions and the periodical variation of orientation of the [CO3] groups between the unit layers of B2S. We have observed the {000l} microtwin of the 6R polytype and the syntactic intergrowths among the different polytypes formed by stacking faults in B2S.

According to the HRTEM study, the UHP jadeite-quartzite mineral (Rutile, TiO2) in Anhui Province, Dabie Mountains, China, has ultrastructures such as [011] two-dimensional commensurable modulated structures or superstructures, [011] twin domain structures, dislocations and crystal deformations. The SAED patterns and HRTEM images indicate the existence of the deformations and stacking faults on the interface of [011] twin crystal of rutile and its two-dimensional commensurate modulated structures with repetition period 0.753m (3d011) has tetragonal symmetry, cell parameters a=3a0=1:377nm (a0=0.459nm), c=c0=0:3nm. The modulated structures of rutile were probably caused by the isomorphic replacement of Ti4

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.

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.