【摘要】 报道了大别山双河地区超高压榴辉岩和硬玉石英岩矿物超微构造及缺陷结构的高分辨透射电镜研究结果。在天然变形绿辉石晶内的自由位错、位错倾斜壁、位错环、位错网、亚晶界、堆垛层错等亚构造中 ,发现了纳米级水分子团 ,这种球形状水分子团包体的存在是导致绿辉石晶体水解弱化和塑性变形的重要因素。在榴辉岩矿物中广泛发育的层错、(10 0 )变形双晶、晶畴结构、界面与晶面的交叉滑移、晶格畸变等变形构造及缺陷结构 ,指示超高压岩石经历了快速折返。在硬玉单晶大约 5 0 0nm的微晶畴内 ,发现了C2 /c和P2 1/n两种结构 ,C2 /c结构的晶体学参数对应于硬玉 ,而P2 1/n结构的晶体学参数对应于绿辉石 ,纳米级P2 1/n出溶结构的存在 ,表明在退变质过程中 ,硬玉在纳米尺度上部分转变为绿辉石 ,并且未能达到平衡。也说明在主体岩石的抬升过程中 ,硬玉晶体伴随有复杂的非平衡退变质作用。对于大别山超高压变质岩的p T轨迹描述及其构造解释具有重要意义。更多还原

【Abstract】 We present high-resolution transmission electron microscope （HRTEM） studies on ultra-microstructures of eclogite and jadeite quartzite in the Dabie ultra-high-pressure （UHP） metamorphic terrane, South China. In the dislocation substructures such as free dislocations, dislocation tilt-walls, long straight dislocations, dislocation loops, dislocation networks and sub-boundaries in deformed omphacite, the cluster of water molecules on the nano-scale has been discovered. The cluster of water molecules presenting in spherical inclusions in omphacite directly causes hydrolytic weakening and induces the plastic deformation of omphacite by dislocations. The defect microstructures such as the stacking faults, （100） deformed twins, domain structures, intersecting gliding of the crystal plane and the boundaries, as well as the lattice distortion in minerals of eclogite demonstrate the rapid exhumation of UHP rocks. The electron diffraction patterns and HRTEM images reveal P2₁/n structure in 500 nm microdomains of single jadeite crystals; the presence of the P2₁/n structure shows that jadeite partially changed into omphacite on a nano-scale during retrograde metamorphism and that this reaction failed to reach equilibrium. It suggests uplift of the host rock during exhumation accompanied by complex non-equilibrium retrogressive process in the jadeite, which is of great significance for the derivation of p -T paths and tectonic interpretation of the Dabie UHP metamorphic terrane.更多还原