中国超基性岩变形变质作用与超微构造分析

METAMORPHISM, DEFORMATION AND ULTRAMICROSTRUCTURAL ANALYSIS OF ULTRABASIC ROCKS IN CHINA

通过野外及透射电子显微镜（ＴＥＭ）等实验研究与综合分析，认为西准噶尔、祁连山、秦岭、喜马拉雅山、阿拉善和汉诺坝等地区的蛇绿岩型、绿岩型、暗色岩型超基性岩及其主要造岩矿物——橄榄石的结构类型、形成环境、变形、变质作用、位错组态、位错密度、布格氏矢量（ｂ）、滑移系及流动应力值（σ１—σ３）具有一定的共同性与差异性。根据橄榄石变形实验资料分析，有的相当于上地幔条件下高温蠕变阶段所形成，有的则属于进入地壳后低温流变的产物。

The paper is completed on the basis of field studies over ten years and the multiple observation, determination and computer calculation by means of common microscope and TEM in labaratory. It covers several tens of ultrabasic rock bodies of ophiolite, greenstone and melanocrate occurred in west Junggar, Alashan, Qilian, Qinling, Himalaya and Hannoba, areas, etc.There exist different textures in the ultrabasic rocks: 1. The primary granular, granular-blast or tabuler-blastic, porphyroclastic and mylonitic textures, which all are formed in upper mantle environment; and 2. the granular-cyclopean and poikilitic textures, which are formed in crustal envircnment. The dislocation density of porphyroclastic olivine presents certain differences in different areas or positions. For example, within the range of LabaDarbut arcuate fault in west Junggar, the dislocation density at the top of the arc is higher than those in the intra-arc and at the limbs. Dislocation densities of the west Junggar and Qinling Songshugou ultrabasic bodies and Hamnoba peridotite xenolith are respectively 4. 81 ×107, 3. 10 × 106, 2.56 × 107 cm-2 and corresponding flow stress (σ1, σ3 ) are respectively of 704. 6×105, 162. 4 ×105, and 501.9 × 105 Pa. The Bugler vector (b) is dominantly a [100]or c[001] and a few is b[010], whereas the slip systems are mainly (010) [100] or (010) [001]and a few (100) [o1o]. According to the experimental data of olivine deformation, the former is related to high-temperature creep under the upper mantle condition, while the latter corresponds to the product of low temperature flow in the crustal environment; and the multilayered texture prevailedly developed in forsterites of strongly strained meta-peridotite in ophiolite and in chrysolites of plagioclase lherzolite and clinopyroxent penidotite in greenstone-type and melanocrate-type of complexes. The latter two types of rock bodies were solidified and formed when the magma invaded into the upper crustal and their crystallization temperature is about 1150-800℃. It would be considered, therefore, that faults and multilayered texture are mainly formed at low-temperature and high-strain environment in upper Crust.