华北克拉通南缘蓝田和牧护关花岗岩体:LA-ICPMS锆石U-Pb年龄及其构造意义  

LA-ICPMS zircon U-Pb ages of the Lantian and Muhuguan granitoid plutons,southern margin of the North China craton:Implications for tectonic setting

作　　者：丁丽雪[1,2] 马昌前[1,3] 李建威[3,4] 王连训[1] 陈玲[1] 佘振兵[1] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074 [2]武汉地质矿产研究所,湖北武汉430223 [3]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074 [4]中国地质大学资源学院,湖北武汉430074

出　　处：《地球化学》2010年第5期401-413,共13页Geochimica

基　　金：国家自然科学基金(90814004;40334037);中国地质调查局计划项目(1212010918002);中央高校基本科研业务费专项基金(CUG090102)

摘　　要：蓝田和牧护关花岗岩体位于华北克拉通南缘、东秦岭西北端,同时地处大兴安岭-太行山重力梯度带西侧,准确限定其侵位时代对于正确理解华北克拉通岩石圈减薄的时空分布特征及东、西秦岭中生代岩浆作用的时空分布均具有重要意义。蓝田岩体主要由巨斑状二长花岗岩和中细粒二长花岗岩组成,牧护关岩体主要由花岗闪长岩、二长花岗岩和富黑云母花岗岩组成。对其中主体岩性的锆石LA-ICPMSU-Pb定年结果表明,蓝田和牧护关岩体的侵位时代分别为(154±1)Ma和(151±2)Ma,说明它们是燕山期(晚侏罗世-早白垩世)岩浆活动的产物。蓝田-牧护关岩体以西的西秦岭广大地区印支期岩浆岩分布广泛,但迄今为止尚未发现燕山期岩浆活动的证据;相反在蓝田-牧护关岩体以东的华北克拉通南缘和东秦岭地区,燕山期侵入岩十分发育。秦岭造山带中生代花岗岩类侵位时代的系统差异表明,东秦岭和西秦岭自晚侏罗世以后受不同的构造背景控制。一般认为,西秦岭印支期岩浆岩与扬子和华北板块的碰撞拼合有关,而东秦岭燕山期岩浆岩则与华北克拉通岩石圈减薄或太平洋板块向欧亚大陆的俯冲有关。因此,蓝田和牧护关岩体可能代表了滨太平洋构造-岩浆域和华北克拉通岩石圈减薄的西界。The Lantian and Muhuguan granitoid plutons are located in the southern margin of the North China craton and the northwest of the East Qinling orogen, respectively. They are also situated to the west of the Daxing＇anling- Taihangshan gravity lineament. Precise determination of the emplacement age of these granitoids is therefore important for understanding the characteristics of temporal and spatial distribution of lithospheric thinning of the North China craton and temporal and spatial distribution of the Mesozoic magmatism in the eastern and weastem Qinling areas. The Lantian pluton consists of large porphyritic monzogranite and medium- to fine-grained monzogranite, whereas the Muhuguan pluton consists of granodiorite, monzogranite and biotite-rich granite. LA-ICPMS zircon U-Pb dating indicates that the Lantian and Muhuguan plutons were emplaced at （154 ± 1） Ma and （151 ± 2） Ma, respectively, demonstrating that they were the products of the Yanshanian （Late Jurassic-Early Cretaceous） magmatic activities. The western Qinling region, immediately to the west of the Lantian and Muhuguan plutons, hosts numerous Triassic granitoid intrusions, but no Yanshanian magmatic rocks have been recognized. By contrast, the Yanshanian intrusions are widely distributed in the southern margin of the North China craton and the eastern Qinling region, the east of the Lantian and Muhuguan plutons. The systematic differences in the emplacement ages of the intrusions in the Qinling orogen imply that the eastern and western Qinling were controlled by different tectonic settings since the Late Jurassic. It is generally accepted that the Indosinian magmatic rocks in the western Qinling are related to the collision between the Yangtze and North China plates, however, the Yanshanian magmatic rocks in the eastern Qinling are associated with the lithospheric thinning of the North China craton or the subduction of the Pacific plate toward the Eurasian continent. The Lantian and Muhuguan plutons thus likely represent the western

关 键 词：蓝田 牧护关 华北克拉通南缘 燕山期 岩石圈减薄 太平洋俯冲 

分 类 号：P597[天文地球—地球化学]