变质重结晶锆石微量元素地球化学与U-Pb年代学：以辽宁红透山铜锌矿床赋矿片麻岩为例

钱烨^{1, 2}，孙丰月¹，李碧乐¹，霍亮¹，张雅静¹

(1. 吉林大学 地球科学学院，吉林 长春，130061；2. 西北大学 大陆动力学国家重点实验室，陕西 西安，710069)

摘 要：利用CL和LA-ICP-MS技术，对红透山铜锌矿床赋矿黑云母斜长片麻岩中的锆石开展了内部结构特征分析、原位微量元素组成分析和锆石微区定年。CL图像特征显示锆石具有核幔边结构，分析认为核部为岩浆锆石，幔部为变质重结晶锆石；原位微量元素组成分析的结果显示核部和幔部锆石稀土元素组成存在异同点，相同之处表现在两者的稀土配分模式相似，表明微量元素组成方面变质重结晶锆石对岩浆锆石的继承性；差别之处体现在稀土总量和轻稀土上，幔部变质重结晶锆石的稀土总量和轻稀土量都明显低于核部岩浆锆石，显示变质重结晶过程中锆石中稀土元素的地球化学行为。在此基础之上，对锆石U-Pb年龄进行合理解释，认为核部岩浆锆石年龄2 552 Ma代表研究区海底火山岩的喷发时限，变质重结晶锆石较小年龄2 520 Ma代表区域变质事件的时限。既而限定红透山铜锌矿的成矿时代在2 552 Ma，变质变形时代2 520 Ma。

关键词：变质重结晶锆石；锆石微量元素；锆石U-Pb年代学；红透山铜锌矿

Trace element geochemical and U-Pb geochronology of metamorphic recrystallization zircon: Taking gneiss from Hongtoushan copper-zinc deposit as an example

QIAN Ye^{1, 2}, SUN Fengyue¹, LI Bile¹, HUO Liang¹, ZHANG Yajing¹

(1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. State Key Laboratory of Continental Dynamics, Northwest University, Xi’an 710069, China)

Abstract:Hongtoushan copper-zinc deposit is the only one large massive sulfide deposit in archean granite-greenstone, which is located in the northeast of North China Craton. The host rock of the deposit is biotite plagioclase gneiss. Through the research on the CL images of zircons from the biotite gneiss, the core-mantle-rim texture of zircons was found. The analysis results reveal that the core is magmatic zircons, and the mantle is metamorphic recrystallization zircon. With LA-ICP-MS technology, in situ trace elemental compositions and U-Pb age of zircon were tested. The distribution patterns of th rare-earth element are similar in two types zircons, which implies that they are isogenesis. There are differences between them: the total content and light rare earth elements of the mantle zircon are both significantly lower than those of the core, which suggest the geochemical behaviors of the trace elements of zircon in the metamorphic process. Based on this, the zircon U-Pb age is rationalized. Zircon U-Pb age information shows that the oceanic volcanic erupts Archeozoic crystalline basement formed in 2 552 Ma of the study area from magmatic zircons, and metamorphic event occurrs in 2 520 Ma according to metamorphic recrystallization zircons. The Hongtoushan copper-zinc deposit’s mineralization epoch is limited in 2 552 Ma，and deformation and metamorphism is confined in 2 520 Ma.

Key words:metamorphic recrystallization zircon; trace element geochemical; U-Pb geochronology; Hongtoushan copper-zinc deposit