The study of Cenozoic intermediate-acidic volcanic rocks in Tengchong has been very insufficient in the past. Based on geochemical studies of intermediate-acidic volcanic rocks, the authors divided the Cenozoic volcanic rocks into Sr-high, Yb-low Adak-type dacite and Sr-low, Yb-medium Zhe-Min (Zhejiang-Fujian) type dacite, with the time limit being N 2(2.78~4.04Ma) and Q1(0.73~1.19Ma)respectively. These intermediate-acidic volcanic rocks were formed during the transform process from stable⁃ness to collapse after the orogenic uplift of the Tengchong- Gangdise belt. In Miocene, the stress of Tengchong-Gangdise plateau was transformed from the domination of EW-trending compression to NS-trending strike-slip, and the orogenic belt began break⁃up. Blocked by the Luxi-Baoshan land mass, the direction of the strike-slip was deflected and resulted in the detachment and forma⁃tion of rift basin among axial fault slices at the turning end in the early period of the formation of rift, the mantle was decompressed and intruded upward, and the high-pressure part of the lower crust was partly melted to form Adak-ype granitic magma. In early Pleistocene, with the intensification of the rifting, the crust became further thinner, and the lower crust was partly melted under the condition of low pressure to form Zhe-Min type granitic magma.%腾冲新生代中酸性火山岩以往研究较为薄弱，通过中酸性火山岩岩石地球化学研究，将腾冲新生代中酸性火山岩划分为高Sr、低Yb的埃达克型英安岩和低Sr、中Yb的浙闽型英安岩，其时限分别为上新世（2.78~4.04Ma）和早更新世（0.73~1.19Ma），为腾冲冈底斯带造山隆升后，由稳定至垮塌过程中形成的中酸性火山岩。中新世，腾冲冈底斯高原应力由东西向挤压为主转变为南北向走滑，造山带开始裂解。受潞西—保山地块阻挡，走滑方向偏转，在转折端轴向断片间滑脱形成裂谷盆地。裂谷形成初期，地幔减压上侵，下地壳高压部分熔融形成埃达克型花岗质岩浆；至早更新世，随着裂谷加剧，地壳厚度进一步减薄，在低压条件下下地壳部分熔融形成浙闽型花岗质岩浆。
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