摘要
灶火沟早志留世（436.8 ～433.7 Ma）花岗岩发育于东昆中蛇绿构造混杂岩带中,主要岩石类型为花岗闪长岩和二长花岗岩,其围岩分别为中元古代万宝沟群和奥陶—志留纪纳赤台群.花岗闪长岩和二长花岗岩w（SiO2）分别为56.12％ ～63.49％和70.62％ ～76.54％,均为钙碱性系列.二长花岗岩显示向富碱质过渡的特征,铝饱和指数A/CNK为0.79～1.02,属准铝质—弱过铝质系列,为Ⅰ型花岗岩.花岗闪长岩∑REE低于二长花岗岩∑REE,两者均具有LREE相对富集而HREE相对亏损的相似的右倾球粒陨石标准化配分曲线特征,花岗闪长岩具弱负Eu异常,二长花岗岩具强负Eu异常;两者均具有相对富集LILE而相对亏损HFS的微量元素特征.地球化学特征显示灶火沟花岗岩为岛弧型花岗岩,是原特提斯洋壳向北俯冲引起地幔楔物质底侵东昆仑岛弧下地壳部分熔融的产物,表明东昆仑造山带在早志留世仍处于原特提斯洋壳俯冲消减阶段.
Zaohuogou Early Silurian granite （436.8 ～433.7 Ma） dominated by granodiorite and monzogranite is located in the central ophiolitic tectonic melange belt of eastern Kunlun.The surrounding rocks are Mesoproterozoic Wanbaogou group and Ordovician-Silurian Nachitai group,respectively.The contents of SiO2 in the granodiorite and monzogranite are 56.12％ ～ 63.49％ and 70.62％ ～ 76.54％,respectively,belonging to calkaline series.The monzogranite shows the characteristics of the alkaline rocks,and the rocks are metaluminous-peraluminous series with A/CNK as 0.79 ～ 1.02,belonging to I-type granites.The ∑ REE in granodiorites is lower than in the monzogranites,and both the rocks displayed the characteristics of enrichment in LREE and relative loss in HREE.The granodiorite has slight negative abnormality in Eu,and both the two rocks are charaterized by depletion in HFS and enrichment in LILE.The geological characteristics reveal that the Zaohuogou granites were island arc granites.They were derived from the partial melting of the lower island arc crust of eastern Kunlun which caused by the underplating of the mantle wedge in the period of the Prototethys oceanic crust subduction.The discovery of Zaohuogou granites indicates that the eastern Kunlun was still in the stage of the Prototethys oceanic crust subduction during the Early Silurian.
出处
《世界地质》
CAS
CSCD
2014年第4期758-767,共10页
World Geology
基金
中国地质调查局青海1:5万区调项目(1212010918012
1212011086001)
关键词
东昆仑
早志留世
花岗岩
火山弧
eastern Kunlun
Early Silurian
granite
volcanic arc
