摘要
中冈底斯带广泛分布则弄群火山岩,其成因机制一直存在争议。本文对出露于来多地区的则弄群火山岩进行了锆石U-Pb定年及全岩地球化学分析,旨在精确限其形成时代,探讨其成因机制。结果表明,来多地区的则弄群火山岩形成于124.0~114.7Ma之间;岩石SiO 2含量在54.53%~78.35%之间,铝饱和指数A/CNK为0.77~3.75,属偏铝质-过铝质岩石,轻稀土富集,负Eu异常明显,相对富集Rb、Th、U等大离子亲石元素,亏损Nb、Ta等高场强元素,岩石具有弧火山岩的特征。综合分析认为,则弄群火山岩可能为班公湖-怒江缝合带南侧的狮泉河-永珠-纳木错-嘉黎蛇绿岩带所代表的Slainajap洋在早白垩世向南俯冲消减的产物。
The genesis of the widely distributed volcanic rocks of the Zenong Group in the Middle Gangdise Belt,Tibet,has been controversial.By carrying out zircon U-Pb dating of the volcanic rocks from the Zenong Group in Laiduo are,the authors believe that the volcanic rocks of the Zenong Group were formed during 124.0~114.7Ma.The geochemical analyses of volcanic rocks from the Zenong Group show that their SiO 2 contents range from 54.53%to 78.35%,and the aluminum saturation index A/CNK is between 0.77 and 3.75,suggesting the volcanic rocks of the Zenong Group belong to the aluminum-peraluminous rocks,enriching in LREEs and LILEs such as Rb、Ba、Th and U,depleting in HFS elements such as Nb and Ta,and with an obvious negative anomaly of Eu.Evidences of the both Zircon U-Pb dating and lithogeochemisty indicate that the Zenong Group may be the product of the southward subduction of the Slainajap ocean which is now in the form of Shiquanhe-Yongzhu-Namucuo-Jiali ophiolite belt during the Early Cretaceous.
作者
张彤
黄波
罗改
马昭雄
黄永高
王燚
ZHANG Tong;HUANG Bo;LUO Gai;MA Zhaoxiong;HUANG Yonggao;WANG Yi(Geological Survey of Sichuan Province,Chengdu 610081,Sichuan,China;The geological prospecting team of Sichuan Geological&Mineral Bureau,Chengdu 610032,Sichuan,China)
出处
《沉积与特提斯地质》
CAS
CSCD
2020年第2期75-90,共16页
Sedimentary Geology and Tethyan Geology
基金
中国地质调查局项目(DD20160015)。
