摘要
In Baigang ophiolitic m6lange of the Yarlung Zangbo Suture Zone exposes an unusual spinel - garnet lherzolite block, which is surrounded by soft crust of serpentinized lherzolite. In this block, there are four kinds of clino-pyroxene. They are earliest recrystallized matrix clino-pyroxene, exsolution elino-pyroxene, inserting elino-pyroxene, and exotic clastic elino-pyroxene. It can also be seen the metamorphic reaction that is calcarous pyroxene ＋ spinel→andradite. We also find there are some needle-like humite exsolution in olivine in both core and crustal lherzolites. Geo-thermobarometers are applied to these lherzolites, which give a result of higher than 900 ℃ temperature and more than 1.8 GPa pressure, and also implies that the spinel -garnet lherzolite block have experienced aletter N-like tectonic route composed of ascending, subdction and re - ascending three stages.