黑龙江省东部桦南隆起美作花岗岩的锆石U-Pb定年及其地质意义  

Zircon U-Pb Dating of the Meizuo Granite and Geological Significance in the Huanan Uplift,East Heilongjiang Province

作　　者：黄映聪[1] 任东辉[2] 张兴洲[1] 熊小松[3] 张春艳[1] 王跃[1] 赵亮亮[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]吉林大学应用技术学院,长春130026 [3]中国地质科学院地质研究所,北京100037

出　　处：《吉林大学学报（地球科学版）》2008年第4期631-638,共8页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金重点项目(40739905)

摘　　要：为查明马家街群发生接触变质作用的时代及其构造背景,对出露于黑龙江省东部桦南隆起的美作花岗岩体进行了锆石LA-ICP-MS U-Pb定年研究。结果显示：锆石具有清晰的生长振荡环带,其Th/U比值为0.12-1.04,属于典型的岩浆成因锆石;获得的206Pb/238U加权平均年龄为（259.0±3.6）Ma（n=14,MSWD=5.9）,代表了岩体结晶年龄。美作岩体与佳木斯地块南部的青山、楚山和柴河岩体形成时代一致,其轻稀土富集、重稀土亏损型式和Eu负异常以及明显的Nb、Ta、Sr、Ti亏损的特点显示为壳源成因的火山弧花岗岩;它们的形成可能与晚古生代古亚洲洋的消减作用有关,该期花岗岩的就位导致马家街群发生了接触变质作用。美作花岗岩体形成时代的厘定,不仅限定了马家街群的变质时代为晚二叠世,同时为进一步探讨佳木斯地块晚古生代构造演化提供了新证据。LA- ICP- MS zircon U- Pb dating of the Meizuo granite in eastern Heilongjiang Province is carried out in order to determine the age and to discuss the tectonics environment of the Majiajie Group＇s contact metamorphism. The present results show that the zircons from the granite have clear oscillatory zones,their Th/U ratio is between 0. 12 - 1.04, and their weighted average ^206 pb/^238 U age is （259.0±3.6） Ma（n=14,MSWD=5.9）. This shows that the crystalline age of the Meizuo granite is the Middle Permian. This age is also same as the age of the Qingshan, Chushan and Chaihe granites in the southern Jiamusi block, and the common geochemical characteristics （enrichment of light REEs, depletion of heavy REEs, negative Eu anomaly and obvious depletion in Nb, Ta, Sr and Ti） of these granites show that they are volcanic arc granites of crust derivation. They are probably related to the subduction of the Paleo-Asia Oceanic plate, and their intrusion resulted in the contact metamorphism of the Majiajie Group. The determination of the Meizuo granite＇s crystallization age not only reveals that the contact metamorphism age of the Majiajie Group is the Later Permian, but also provides new evidence for the Paleozoic tectonic evolution of the Jiamusi block.

关 键 词：桦南隆起 LA-ICP-MSU-Pb定年 晚古生代花岗岩 马家街群 佳木斯地块 

分 类 号：P597[天文地球—地球化学]