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滇东地区的师宗-弥勒构造带是解决古特提斯东延问题的关键,综合研究表明,该带是以多条断层为骨架,包容不同性质构造岩块的构造带。明显分隔两侧不同岩石-构造组合、变质作用、岩浆活动。师宗 弥勒构造带北段的火山岩地球化学研究表明,其主要为碱性玄武岩,主元素以低TiO2、高Al2O3为特征,区别于高TiO2、低A12O3特征的峨眉山大陆溢流玄武岩。高场强元素丰度类似于板内玄武岩平均丰度,Zr/Nb、Hf/Th值分别变化在5.6～13.5和0.9～1.3范围内,类似于板内玄武岩。球粒陨石标准化的稀土元素配分模式为LREE富集型,MORB标准化的微量元素配分型式为大隆起型,显示岩浆形成于板内裂谷构造环境。不活动元素协变关系也支持这一结论。同位素地球化学研究表明,岩石以低143Nd/144Nd、高87Sr/86Sr值为 特征,类似于Rio Grande裂谷玄武岩的同位素组成,εNd(t)值变化在+0.9～+3.2之间,显示岩浆源于轻微亏损地幔,并受到富集地幔物质影响。(205Pb/204Pb)i、(207Pb/204Pb)i和(208Pb/204Pb)i分别变化在17.131～19.119,15.386～15.670和37.780～39.266之间,(206Pb/204Pb)i和(207Pb/204Pb)i具有正相关关系。△208Pb/204Pb和△207Pb/204Pb分别变化在5～24和21～61之间,显示本次研究的玄武岩来源于DMM和EMII混合组成的地幔,明显区别于具
The Shizong-Maitrein tectonic belt in eastern Yunnan is the key to solve the Guteethis eastward extension problem. Comprehensive studies show that the belt is a structural belt that contains multiple faults as the skeleton and contains rock blocks of different nature. Significant separation of different rock on both sides - tectonic assemblage, metamorphism, magmatic activity. Volcanic geochemical studies in the northern segment of the Shizanyili tectonic belt show that they are mainly alkaline basalts, and the main elements are characterized by low TiO2 and high Al2O3, which are distinguished from the overflowing basalt Emeishan in the characteristics of high TiO2 and low A12O3. The abundance of high field strength is similar to the average abundance of basalt in the plate. The values of Zr / Nb and Hf / Th vary from 5.6 to 13.5 and from 0.9 to 1.3, respectively, similar to intraplate basalts. The normalized REE patterns of chondrules are LREE-enriched and the MORB-normalized trace elements are large-hump-shaped, indicating that magma is formed in the intraplate rift tectonic setting. Incoordination of inactive elements also supports this conclusion. Isotope geochemistry shows that the rocks are characterized by low 143Nd / 144Nd and high 87Sr / 86Sr values, which are similar to those of the Rio Grande rift basalts. The εNd (t) value varies between + 0.9 and + 3.2, indicating that the magmatic source At a slight loss to the mantle, it is affected by enrichment of the mantle material. (205Pb / 204Pb) i, (207Pb / 204Pb) i and (208Pb / 204Pb) i vary from 17.131 to 19.119, from 15.386 to 15.670 and from 37.780 to 39.266, (206Pb / 204Pb) i and Has a positive correlation. △ 208Pb / 204Pb and △ 207Pb / 204Pb change between 5 ~ 24 and 21 ~ 61, respectively, indicating that the basalt in this study is derived from the mantle consisting of a mixture of DMM and EMII,