摘要
狼山地区位于内蒙古西部,索伦蛇绿岩带西南,晚古生代岩浆岩分布广泛,是中亚造山带晚古生代构造演化研究的关键位置。利用LA-ICP-MS锆石U-Pb测年方法获得狼山地区沙日楚鲁花岗闪长岩及莫若古花岗闪长岩的形成时代分别为(278.07±0.66)Ma和(278.05±0.69)Ma,为早二叠世晚期岩浆活动的产物;岩石地球化学特征表明,狼山地区早二叠世晚期花岗闪长岩属于高钾钙碱性系列(SiO2:63.76%~67.88%;K2O:2.74%~4.02%)、弱过铝质岩石(A/CNK:0.94~1.07),具有中等的Mg#(38.98~47.53);轻稀土(LREEs)及大离子亲石元素富集,重稀土及高场强元素亏损,具有弱的Eu负异常,为具有陆缘弧花岗岩特征的Ⅰ型花岗岩。锆石Hf同位素分析结果显示,沙日楚鲁花岗闪长岩及莫若古花岗闪长岩具有负的而略显分散的εHf(t)值(-0.6^-7.5),其源区物质主要来源于华北古老地壳,并有少量幔源物质加入。结合区域地质背景,认为狼山地区早二叠世晚期花岗闪长岩形成于古亚洲洋向南俯冲的活动大陆边缘环境,彼时洋盆尚未闭合。
The Langshan area is located in the west of Inner Mongolia,southwest of the Solonker ophiolite belt,which is the ideal workplace to study tectonic-magmatic evolution and geodynamics background in Late Paleozoic because of the intense magmatism. LA-ICP-MS Zircon U-Pb ages yielded the formation time of granodiorite of Sharichulu and Moruogu granitic pluton(278.07±0.66)Ma and(278.05±0.69)Ma,respectively,forming in the latest early Permian. Geochemical characteristics showed that the Zhalashan granites were high-K calc-alkaline(SiO2:63.76%~67.88%;K2 O:2.74%~4.02%)and weak peraluminous rocks(A/CNK:0.94~1.07)with moderate Mg# values(38.98~47.53). In addition,it exhibited LILE and LREEs enriched,HFSE and HREEs depleted with slight Eu anomaly,and all of the above-mentioned indicated the characteristics of Ⅰ-type granites and arc-related. Zircon Hf isotope showed that the scatter εHf(t)values varied from-0.6^-7.5,which suggests a mixed magma source of old continental crust with a small involvement of mantle components. Together with regional geological background,the authors hold that the Latest early Permian granodiorite of Langshan area formed in an active continental margin setting under the background of southward subduction of the Paleo-Asian Ocean which were not close at that time.
作者
刘洋
王文龙
滕学建
郭硕
滕飞
何鹏
田健
段霄龙
Liu Yang;Wang Wenlong;Teng Xuejian;Guo Shuo;Teng Fei;He Peng;Tian Jian;Duan Xiaolong(Tianjin Center of Geological Survey,China Geological Survey,Tianjin 300170,China)
出处
《地球科学进展》
CAS
CSCD
北大核心
2019年第4期366-381,共16页
Advances in Earth Science
基金
中国地质调查项目“1∶5万查干呼舒庙等六幅区域地质矿产调查”(编号:1212014121079)资助~~
关键词
华北北缘
狼山地区
活动大陆边缘
地球化学
Ⅰ型花岗岩
The northern margin of the North China Craton
Langshan area
Active continental margin
Geochemistry
Ⅰ-type granitoid
