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一种取自纽约州 Balmat 的辉石,其平均成分是 Ca_(0.43),Mn_(0.69),Mg_(0.82),Si_2O_6;被解释为 p2_1/c 和 c2/c 两种相共存。如晶胞参数 M_1和—O 与 M_2-0键长的平均值与成分所绘制的关系图那样,其精测结构是部分通过研究各个单相的成分获得的。占位情况表明,这两种相是锰透辉石和锰易变辉石(kanoite)。透射电子显微照片揭示,这些相是呈页片状的,共(001),并以此为相间边界,页片宽为2000(?)。单个页片的 x—射线能散分析表明,C2/c 相的平均成分为 Ca_(0.68),Mn_(0.44),Mg_(0.88),Si_2O_6;P_(21)/c 相的平均成分为 Ca_(0.12),Mn_(1.02),Mg_(0.86),Si_2O_6。暗场照片揭示,在 p2_1/c 相中有反相晶畴边界的存在,表明在 Ca—Mn—Mg 辉石体系中,其贫 Ca 相存在着一个 C2/c—P2_1/c相的转变。原地加热实验得到 C2/c—P2_1/c 相的转换温度为330±20℃。通过加热,根据在转换温度前后的反相边界(APB—antiphaseboundary 的编写—编者注)位置的观测,得知 APB 位置基本上不改变,表明 APB′S 的稳定是通过 Ca 的富集或 APB′S 的某些晶体缺陷来实现的。横切页片边界(001)的晶格条纹照片表明,其界面是半连贯或完全连贯的。由于旋节分解或成核作用以及后期缓慢冷却,使得这一作为区域变质相的结构特征与原始的出溶结构相一致。
A pyroxene from Balmat, New York State has an average composition of Ca_ (0.43), Mn_ (0.69), Mg_ (0.82) and Si_2O_6, which are interpreted as the coexistence of two phases, p2_1 / c and c2 / c. As the average of the unit cell parameters M_1 and -O and the M_2-0 bond length is plotted against the composition, the structure of the fine test is obtained in part by studying the composition of each single phase. The occupancy shows that the two phases are manganopyroxene and manganese kanoite. Transmission electron micrographs revealed that these phases were sheet-like, co-001, and were interphase boundaries with sheet widths of 2000 (?). The X-ray energy dispersive analysis of a single sheet shows that the average composition of C2 / c phase is Ca_ (0.68), Mn_ (0.44), Mg_ (0.88), Si_2O_6 and the average composition of P_ (21) 0.12), Mn_ (1.02), Mg_ (0.86), Si_2O_6. The dark field photos reveal the presence of an inverting domain boundary in the p2_1 / c phase, indicating that there is a C2 / c-P2_1 / c phase transition in the Ca-poor phase of Ca-Mn-Mg pyroxene. In-situ heating experiments C2 / c-P2_1 / c phase transition temperature was 330 ± 20 ℃. From the observation of the position of the reverse phase boundary before and after the transition temperature (APB-antiphaseboundary-editor’s note) by heating, it was found that the APB position did not substantially change, indicating that APB’s are stabilized by Ca enrichment or APB ’ S some crystal defects to achieve. Lattice streaks across the page boundary (001) show that the interface is semi-coherent or completely coherent. Due to spinodal decomposition or nucleation and late slow cooling, the structural characteristics of the metamorphic zone are consistent with the original dissolution structure.