对新疆阿尔泰蒙库铁矿变粒岩进行LA-ICP-MS锆石U-Th-Pb同位素分析,初步探讨了锆石年龄的地质意义.锆石在CL图像中无明显的岩浆锆石所具有的震荡环带和核边结构,或锆石晶体振荡环带呈星云状、放射状,不均一,显示出变质新生锆石的特点.25个锆石颗粒测点给出的206Pb/238U年龄介于366Ma±2Ma～393Ma±2Ma之间,加权平均值为380.1Ma±4.0Ma(MSWD=1.2,1σ),揭示出蒙库铁矿一带在晚泥盆世存在一期构造热事件.对变粒岩锆石进行了激光拉曼光谱研究,结果显示锆石具有弱-中等的蜕晶化,可能受本次构造热事件的影响,说明蒙库铁矿的主要成矿期应该不晚于380.1Ma±4.0 Ma.%In this paper, LA-ICP-MS zircon U-Pb dating was performed to study the chronology of granulite in the Mengku iron ore deposit and to evaluate its geological significance. Zircon CL images show the features of non—magmatic zircon, without oscillatory zoning and core -rim structure, and crystal oscillatory zoning is nebulous, radial, and heterogeneous, indicating deterioration of the characteristics of zircon. The 206Pb/238U ages of 25 zircon grains are between 366Ma±2Ma and 393Ma±2Ma with the weighted average of 380.1 Ma±4.0Ma (MSWD = 1.2, 1σ), which represent the formation ages or cooling ages of metamorphic rocks. Zircon laser Raman spectroscopic studies show that these zircons probably experienced weak —medium degrees of metamictization, affected by the tectono—thermal event at 380Ma.
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