甘肃北山红柳沟辉长岩地球化学、年代学及构造意义  

Geochemistry,zircon U-Pb chronology and tectonic significance of gabbro in the Beishan Hongliugou area in Gansu Province

作　　者：马骊 魏海峰[2] 王怀涛[2] 杨婧 霍永豪 翟新伟 

机构地区：[1]兰州大学地质科学与矿产资源学院甘肃省西部矿产资源重点实验室,兰州730000 [2]甘肃省地质调查院,兰州730000

出　　处：《兰州大学学报（自然科学版）》2018年第1期59-67,共9页Journal of Lanzhou University(Natural Sciences)

基　　金：中国地质调查局调查项目(12120114014501)

摘　　要：甘肃北山红柳沟辉长岩LA-ICP-MS锆石U-Pb年龄为405.8±2.9 Ma;辉长岩w(SiO_2)、w(Fe)变化范围大,w(K_2O)、w(Na_2O)低且相对富钠贫钾,辉长岩具有Eu、Sr的正异常,富集大离子亲石元素(Rb、Sr、Ba等)和轻稀土元素,强烈亏损高场强元素(Nb、Th、Ce等)和重稀土元素.结合区域大地构造背景,认为红柳沟辉长岩是先前俯冲流体交代过的亏损地幔部分熔融形成的玄武质岩浆分异堆积的产物,形成于早泥盆世后碰撞伸展的陆缘环境,指示在早泥盆世北山南部地区由挤压向伸展拉张的构造体制转换.The LA-ICP-MS zircon U-Pb dating showed that Hongliugou gabbro formed around 405.84-2.9 Ma. The gabbro is characterized by its variable w（SiO2）, w（Fe）, low alkali content and sodium-rich. The LREE and LILE such as Rb, Sr and Ba are enriched, while the HREE and HFSE such as Nb, Th and Ce are depleted; the rocks also exhibit positive Eu and Sr anomalies. Combined with regional tectonic setting, the studied results indicated that the parental magma of gabbro derived probably from the depleted mantle metasomatized previously by a subduction fluid and accumulated to form the gabbro in the active continental margin in the post-collisional extensional tectonic setting in early Devonian. All results implied that Beishan area, during the tectonic period, changed from compression to extension in early Devonian.

关 键 词：辉长岩 早泥盆世 后碰撞环境 甘肃北山 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]