东秦岭南召地区花岗岩岩石地球化学特征及LA-ICP-MS锆石U-Pb同位素年龄  

Petrological Characteristics and LA-ICP-MS Zircon U-Pb Ages of Granitoid in Nanzhao Area,Eastern Qinling Mountains

作　　者：李名则[1] 吴才来[1] 雷敏[1] 秦海鹏[1] 刘春花[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《地质论评》2014年第2期427-442,共16页Geological Review

基　　金：中国地质调查局地调项目(编号1212011120160;1212010918007;1212010818090;1212010611803;1212010711816);深部探测技术与实验研究专项--东部矿集区科学钻探选址预研究(编号SinoProbe-05-05);国家自然科学基金资助项目(编号40921001;49772106;40472034;40672049)

摘　　要：板山坪岩体和南召岩体位于北秦岭构造带的东部,分别侵入于宽坪群和二郎坪群。通过LA-ICP-MS锆石U-Pb同位素定年,获得板山坪岩体的年龄分别为496.0±8.1Ma和486.9±9.3Ma,南召岩体的年龄为452.3±6.2Ma。板山坪岩体以石英闪长岩为主,少量的花岗闪长岩,南召岩体以花岗闪长岩为主。地球化学研究表明,板山坪岩体和南召岩体均显示出I型花岗岩类的地球化学属性,两个岩体的稀土元素配分模式具有弱的负Eu异常,微量元素特征显示其物质来源均以壳源为主,并可能有幔源物质参与。根据岩体的岩石地球化学和年代学特征,结合区域地质构造分析,笔者等认为,这两个岩体的形成与早古生代扬子板块向华北板块之下俯冲有关,板山坪岩体侵入时间为板块碰撞初期阶段,而南召岩体侵入于块体碰撞抬升阶段。Banshanping and Nanzhao granitoid are located in Nanzhao area, east segment of North Qinling orogenic blet, intruding into the Kuanping Group and the Erlangping Group respectively. The ages of the Banshanping granitoid obtained by LA-ICP-MS Zircon U-Pb dating are 496. 0±8.1Ma and 486. 9±9.3Ma, respectively, the age of Nanzhao granitoid is 452.3±6. 2Ma. The Banshanping granitoid is dominated by quartz diorite, while the Nanzhao granitoid is mainly granodiorite. Geochemical properties show that both Banshanping and Nanzhao granotoid belong to I type, and both of the two have weak Eu negative anomaly. Trace element characteristics suggest that the material sources of the two granitoid may be both from crust, possibly participated by small amounts of mantle material. Based on chronology characteristics and regional geological analyses, the authors consider that the granitoid of Banshanping and Nanzhao are related to the subduction of North china block to Yangtze block in early Paleozoic. The Banshanping rock body while the Nanzhao granitoid formed during the uplifting period formed during the beginning of the plate collision, of the collision.

关 键 词：花岗质岩体 锆石LA—ICP—MS U-PB定年 物质来源 岩浆作用 

分 类 号：P597.3[天文地球—地球化学] P588.121[天文地球—地质学]