PALAEOBIOGEOGRAPHY AND TECTONIC EVOLUTION OF WESTERN YUNNAN
云南西部古生物地理与大地构造演化

According to the distribution and development of the strata and fossils, western Yunnan may be divided into the Baoshan-Tengchang, Gengma-Meng-lian and Lanping-Pu'er areas. In the Baoshan-Tengchang area, the Paleozoic stata are particulary well developed; in the Gengma-Menlian area, the late Paleozoic strata dominate; in the Lanping-Pu'er area, the Mesozoic strata are very extensively distributed.The tectonics of western Yunnan are rather complex. During the Middle Proterozoic era, two blocks were welded in the Ailao Mountain belt, extending from Malutang of Xinping and Panzhihua region of Yuanyang in Central South Yunnan, and formed a NW-SE-striking collage. The northeastern side of the collage is a highmedium temperature-low-medinu pressure metamorphic belt, with typical minerals of andalusite, cordierite, kyanite, staurolite and garnet. The southwestern side is a low-medium temperature-high medium pressure one, with typical minerals of glaucophane and stilpnomelane. Besides ophiolitic melange and opiolite suite were found, from which pyroxenite and gabbro Were dated as 910 Ma and 1340 Ma respectively.During the end of the Middle Proterozoic, the two blocks were once again welded along the Changning-Yunxiang-Lincang Menghai belt in southwestern Yunnan, forming a NNW-SSE collage. The southwestern side is a lowmedium temperature-high-medium pressure metamorphic beJt whose typical minerals are glaucophane, barroisite, stilpnomelane and phengite, while the northeastern side is a high-medium temperature-low-medium pressure one characterized by an assembladge of andalusite, staurolite, cordierite, sillimanite and hypersthe-ne. The granites dated as 715, 784 and 789 Ma are intruded the Lancang Group and the Chongshan Group of the upper wall of the collage.In the middle Cretaceous time, the Baoshan-Tengchong region (along the present Western border or wesster Yunnan), which was then a portion of the Indian Oldland, began to separate from the Gondwana land, and drifted northward. At the end of the Eocene, it collided and incorporated with the Eurasian plate.