摘要
本文对下扬子区内２个玄武岩产地（江苏六合瓜埠山、安徽当涂釜山）的幔源包体进行研究，结果表明本区上地幔尖晶石二辉橄榄岩具原生粒状结构、碎斑结构、板状镶嵌等粒结构及部分熔融结构四种类型。在光学岩组图上显示出从原生粒状结构→碎斑结构→板状镶嵌等粒结构，其橄榄石光性方位优选性逐渐增强。变形橄榄石滑移轴为［１００］，滑移面以｛０ｋ１｝为主，（０１０）次之。高温高压人工变形实验证实，这种滑移系形成于高温低应变速率条件下。橄榄石位错类型多样，（１００）、（００１）位错壁分布广泛，位错壁间距显示对数正态分布特征．估算的本区上地幔高温蠕交流动差异应力为（１０．９～１１．５ＭＰａ）。上地幔流变速率、流动应力、等效粘滞度与深度关系指示本区新生代大地构造性质为大陆拉张带或大陆裂谷带。
Sp-lherzolite xenoliths derived from mantle in low Yangtze area have primary granular texture, porphyroclastic texture, equal tabular texture and partial melting texture. Their petrofabric diagrams indicate that the crystalic graphic orientation of olivine changes obviously according to above textural sequence. Slip system of the deformed olivine is {ok1},[100]. The dislocation substructures of olivine have many types and are strongly similar to the substructures produced in laboratary deformation of polycrystals at high temperature and pressure. Dislocation wall of (100) and (001) are widely distributed, the frequency of subgrain spacing follows a logarithm normal distribution, indicating that rheological stress at high temperature is 11. 8￣ 11. 5 MPa. The relationships between rheological stress, rheological values, equivalent viscosity and depth indicate that the Cenozoic tectonic environment of low Yangtze area is probable of continental rifting or continental extension zone when the host basalts were erupted.
出处
《现代地质》
CAS
CSCD
1994年第1期57-64,T001,共9页
Geoscience
关键词
上地幔
橄榄岩
显微构造
low Yangtze area, upper mantle, peridotite, microstructure
