河北张三营富铌碱长花岗岩和花岗斑岩锆石U-Pb年代学及其地质意义

Zircon U-Pb dating of Zhangsanying Nb-enriched alkali feldspar granite and granite porphyry,Hebei Province,and its geological implications

张三营富铌碱长花岗岩位于华北克拉通北缘中段,文章对该花岗岩和与其伴生的花岗斑岩进行锆石LA-ICP-MSU-Pb定年研究,结果表明富铌碱长花岗岩可能是岩浆多期次聚集作用下形成,结晶年龄约为141 Ma,其晚期分异形成的花岗斑岩均形成于132~124 Ma;张三营富铌碱长花岗岩是早白垩世古太平洋板块俯冲折返作用相关的伸展体制下形成的。研究揭示,除海西期和印支期外,燕山晚期也是华北克拉通北缘铌钽成矿的重要时期,燕山晚期的碱性岩和过铝质花岗岩将成为本区稀有金属找矿的新方向。

The Zhangsanying Nb-enriched alkali granite is located in the middle part of the northern margin of the North China Craton.In this study,we present new zircon U-Pb data of Nb-enriched alkali granite and granite por-phyry.The results show that multistage magma accumulation might result in the formation of the Nb-enriched al-kali granite.Its crystallization age is about 141 Ma and its formation age,together with the granite porphyry,is 132~124 Ma.The alkali granite formed in Early Cretaceous,within an extensional setting during the period of the Paleo-Pacific Plate subduction and subsequent inversion.In addition to Hercynian and Indosinian,Late Yansha-nian is an important metallogenic period in the northern margin of the North China Craton Nb-Ta belt.This area has significant potential for Nb-Ta mineralization.Late Yanshanian alkaline rock and peraluminous granite should be focus of future exploration.