腾冲地块新生代火山作用及地壳演化：源自新生代火山岩斜长石晶体成分及锆石U-Pb年龄、Hf同位素证据

Systematic analyses including the Plagioclase chemical composition, zircon U-Pb ages and Hf isotopes of the Cenozoic MF3 eruption basaltic andesite at Maanshan were carried out to better understand the Cenozoic volcanism and the crustal evolution of the Tengchong block. All the analyzed Pl minerals are mafic, with 68.1-88.4% of An. Clear inverse zoning structure was detected in all Pl crystals, indicating the related multiple magma chambers of the Cenozoic volcanism. Zircon U-Pb ages are from 109 Ma to 44 Ma, much older than the eruption age of the inherited rock, suggesting their heterogeneous origin. Zircon Hf-isotope data show that they were from felsic intrusions of the Tengchong block, which directly enclose the contamination with the crustal material of the Tengchong Cenozoic volcanism. The youngest zircon grains are younger than all dated intrusions in the Tengchong block and with much higher εHf(t) values, indicating that they should probably represent the unexposed granitoid in the Tengchong block. The unique inactive crustal evolution in late Paleozoic of the Tengchong block makes it striking different from other peri-Gondwanaland terrenes such as the west Qiangtang and Lhasa blocks. After 250 Ma, the intensive magma movement and considerable juvenile material accreted into the crust of the Tengchong block.