形成构造环境
(1. 中南大学 有色金属成矿预测教育部重点实验室，长沙 410083；
2. 中南大学 地球科学与信息物理学院，长沙 410083；3. 甘肃有色金属地质研究所，兰州 730000)
摘 要: 哀牢山深变质岩带大皮甲小岩体的岩石类型主要为二云二长花岗岩。w(SiO2)的平均值为72.42%， A/CNK＞1.1(平均值1.17)，K2O/Na2O的平均值为2.18，里特曼指数(σ)为1.76~4.19(平均值3.02)，分异指数(DI)为90~92，∑w(REE)为103.34×10−6~247.39×10−6，∑w(LREE)/∑w(HREE)为1.16~7.45，具弱Eu正异常，在原始地幔标准化蛛网图上显示出Nb、P和Ti负异常及K、Rb、Ba、Th和U正异常，具明显的分异结晶作用特征。岩体的地球化学特征属于高硅、过铝、钙碱性花岗岩，具有壳幔混源型花岗岩的特征。经多种相关图解判别，大皮甲岩体为碰撞造山花岗岩类，形成于同碰撞及后造山的构造环境。
关键字: 哀牢山带；地球化学；构造环境；花岗岩
Dapijia rockbody in Ailaoshan zone
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. Gansu Institute of Geological for Nonferrous Metals, Lanzhou 730000, China）
Abstract:The Dapijia rockbody in the Ailaoshan zone is composed mainly of two-mica adamellite. The average mass fraction of the rockbody is w(SiO2)=72.42%, A/CNK＞1.1 (1.17 on average), K2O/Na2O=2.18 (on average), with Rittmann index σ=1.76−4.19 (2.88 on average), DI=90−92, ∑w(REE)=103.34×10−6−247.39×10−6, ∑w(LREE)/ ∑w(HREE)=1.16−7.45 and δ(Eu)=0.67−1.34. The rockbody shows remarkable negative Nb, P and Ti anomalies as well as positive K, Rb, Ba, Th and U anomalies as shown in the primitive mantle-normalized trace element spider diagrams, suggesting evident fractional crystallization. According to its lithofacies, petrological and geochemical characteristics, the Dapijia rockbody is silica-high and potassium-rich, belonging to peraluminous calc-alkaline crust-mantle mix derived type granites. Various oxide and trace element diagrams for discrimination of tectonic settings reveal that the Dapijia rockbody is orogenic granite formed in an orogenic extensional structural environment.
Key words: Ailaoshan zone; geochemistry; tectonic setting; granite
