形成構(gòu)造環(huán)境
(1. 中南大學 有色金屬成礦預(yù)測教育部重點實驗室，長沙 410083；
2. 中南大學 地球科學與信息物理學院，長沙 410083；3. 甘肅有色金屬地質(zhì)研究所，蘭州 730000)
摘 要: 哀牢山深變質(zhì)巖帶大皮甲小巖體的巖石類型主要為二云二長花崗巖。w(SiO2)的平均值為72.42%， A/CNK＞1.1(平均值1.17)，K2O/Na2O的平均值為2.18，里特曼指數(shù)(σ)為1.76~4.19(平均值3.02)，分異指數(shù)(DI)為90~92，∑w(REE)為103.34×10−6~247.39×10−6，∑w(LREE)/∑w(HREE)為1.16~7.45，具弱Eu正異常，在原始地幔標準化蛛網(wǎng)圖上顯示出Nb、P和Ti負異常及K、Rb、Ba、Th和U正異常，具明顯的分異結(jié)晶作用特征。巖體的地球化學特征屬于高硅、過鋁、鈣堿性花崗巖，具有殼幔混源型花崗巖的特征。經(jīng)多種相關(guān)圖解判別，大皮甲巖體為碰撞造山花崗巖類，形成于同碰撞及后造山的構(gòu)造環(huán)境。
關(guān)鍵字: 哀牢山帶；地球化學；構(gòu)造環(huán)境；花崗巖
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
