Located in the middle and north sections of Changning-Menglian suture zone, Lailitoushan, Yunling and Gengma plutoiis are mainly composed of monzogranites. The zircon LA-ICP-MS U-Pb dating indicates that the three granitoid plutong intruded simultaneously at about 231Ma. The three plutons have 65.65% -67. 68% SiO2, with high K2O (K2O/Na2O =2.71% - 1.42% ) and low CaO (1. 35% ~2. 98% ). These granitoids are high in A/CNK (1.10 -1. 22), and are enriched in Rb, Ba, Th, U, K, La and LREE, but depleted in Mb, Ta, Ti, Zr and Hf. These geochemical signatures indicate that the three plutona are high-K calc-alkaline peraluminous S-type granites. The wide and negative zircon sHf(t) values ( -26. 8 - -8.2) and ancient Hf-isotope crust model ages (1. 2 - 2. 7Ga) indicate that these three plutons originated mainly from anatexis of ancient crust materials ( such as feldspar- and biotite-bearing lithic greywacke) with varying contributions of mantle-derived materials. These plutons probably formed in a post-collisional setting, which may imply that the Burma-Thai-Malaysia microcontinem collided with the Simao block before 232Ma (prior to Late Triassic).%癞痢头山、云岭和耿马岩体位于昌宁-孟连带的中北段,主要岩性为二长花岗岩,锆石LA-ICP-MS U-Pb定年结果表明,这三个岩体几乎同期侵位于约231 Ma.这三个岩体的SiO2含量为65.65％～67.68％,富钾(K2O/Na2O=2.71％～1.42％)和较低钙CaO( 1.35％～2.98％),铝饱和指教(A/CNK)为1.10～1.22,富集Rb、Ba、Th、U、K、La和LREE等元素,相对亏损Nb、Ta、Ti、Zr及Hf等高场强元素.这些特征表明3个岩体属于强过铝质高钾钙碱性S型花岗岩.这三个岩体负且变化范围大的锆石εHf(t)值(-26.8～-8.2)和古老的Hf同位素地壳模式年龄(1.2 ～2.7Ga),表明它们主要来源于古老地壳物质(如含长石和黑云母且贫粘土的杂砂屑岩)的重熔,并有不同程度的幔源物质加入.它们可能侵位于后碰撞背景,可能指示缅泰马微陆块与思茅地块的主体碰撞在232Ma之前(即晚三叠世之前)已经发生.
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