摘要
与柴北缘和北祁连相比,南祁连研究程度偏低,对其各个阶段的构造演化缺少精确时限。对分布于南祁连党河南山中段的科克巴斯陶玄武岩进行了岩石地球化学及锆石U-Pb年代学研究,定年结果显示,该玄武岩成岩年龄为713±4.6Ma,为新元古代震旦纪。岩石地球化学分析表明,科克巴斯陶玄武岩SiO2含量为45.08%~49.81%,MgO为4.37%~6.67%,Na2O为2.95%~3.71%,K2O为0.28%~1.92%,TiO2为1.40%~2.01%,与拉斑玄武岩平均值相似。Nb/Y-SiO2图解显示科克巴斯陶玄武岩属亚碱性系列拉斑玄武岩。其ΣREE为(75.47~124.00)×10^-6,LREE/HREE为4.2~6.19。(La/Yb)N为3.67~6.18,(La/Sm)N为1.83~2.64,球粒陨石标准化稀土元素配分曲线图呈轻稀土明显富集的右倾型。原始地幔标准化微量元素蛛网图上,岩石以富集Sr、K、Rb、Ba为特征。岩石地球化学特征显示科克巴斯陶玄武岩岩浆为具OIB性质的地幔源区,其形成于板内洋岛构造环境。结合区域地层对比及锆石测年成果,将原划定的志留系巴龙贡嘎尔组进行了重新解体,由南至北,分别为志留系巴龙贡嘎尔组变砂岩段、新元古界震旦系天峻组火山岩段和中新元古界拐杖山组片岩段。
Tectonic evolution of the South Qilian is much less well-documented than those of the north Qilian and Qaidam Basin, and particularly lack precise dating results for the tectonic stages. To constrain the tectonic evolution of the South Qilian orogenic belt, chronological and geochemical investigations have been conducted on the Kekebasitao basalt distributed in the middle part of the southern Danghe Mountains, Southern Qilian. The dating result shows that the basalt was erupted at 713±4.6 Ma. The Kebasitao basalt has 45.08% to 49.81% SiO2, 4.37% to 6.67% MgO, 2.95% to 3.71% Na2O, 0.28% to 1.92% K2O, and 1.40% to 2.01% TiO2, which are similar to the average value of tholeiite. The Kebasitao basalt belongs to alkali tholeiite series. The Kebasitao basalt has ΣREE content of 75.47×10^-6 to 124.00×10^-6, with LREE/HREE ratio of 4.2 to 6.19, showing right-dipping chondrite normalized REE patterns. The primitive mantle normalized trace element spider diagrams of the basalt are characterized by enrichment of Sr, K, Rb, and Ba. In addition, the Kebasitao basalt shows OIB-like features which suggests an oceanic island tectonic environment. In combination with regional stratigraphic comparison and zircon dating results, the Balonggonggaer Formation can be divided into three sections such as metasandstone, volcanic rocks, and schist from south to north.
作者
王磊
李向民
胡兆国
杨超
郭令芬
闫海忠
葛瑞臣
计波
WANG Lei;LI Xiangmin;HU Zhaoguo;YANG Chao;GUO Lingfen;YAN Haizhong;GE Ruichen;JI Bo(MNR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,Xi’an Center of Geological Survey,China Geological Survey,Xi’an 710054,Shaanxi,China;Geological Exploration Institute of Shandongzhengyuan,China Metallurgical Geology Bureau,Jinan 250014,Shandong,China;School of the Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;College of Geographic Science,Harbin Normal University,Harbin 150025,Heilongjiang,China)
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2019年第5期1069-1077,共9页
Geotectonica et Metallogenia
基金
中国地质调查局地质调查项目(DD20160012、DD20190065)资助
关键词
玄武岩
岩石化学
锆石U-PB定年
党河南山
南祁连
basalt
geochemistry
LA-ICP-MS zircon U-Pb dating
southern Danghe Mountains
southern Qilian
