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本文报道了在内蒙中部大青山北麓西乌兰不浪地区早前寒武纪基底中发现的太古宙变质深成体-黑云母花岗质片麻岩的SHRIMP U-Pb定年结果.样品的锆石特征较为一致,阴极发光图像上具明显核-幔-边结构.核部锆石发育密集的岩浆环带,年龄数据分布区间较小,其加权平均年龄(2697±11Ma)代表了原岩形成时间,为区内有报道的最古老的高精度岩石年龄,表明区内存在一期2.7Ga左右的岩浆活动.幔部及边部锆石具变质重结晶成因,两者除了在阴极发光图像上的差异外,其加权平均年龄(幔部2561±18Ma;边部2539±34a)及Th、U含量特征极为接近.笔者认为它们共同反映了区域内～2.5Ga的构造-热事件.大量证据表明华北克拉通～2.5Ga的构造-热事件是华北克拉通形成演化过程中所经历的重要地质事件,该事件之前的岩石在这一地质过程中遭受了强烈改造.
This paper reports the SHRIMP U-Pb dating of the Archean metamorphic deep-biotite granodiorite gneiss found in the Early Precambrian basement in the West Ulan-Ulang region, northern foot of the Daqingshan Mountains in central Inner Mongolia. The zirconium The lithogenic annihilation images show a clear core-mantle-edge structure.The magmatic zonation with densely distributed zircons in the core shows a small distribution of age data, and the weighted average age (2697 ± 11Ma) represents the protolith formation Time, which is the oldest reported high-precision rock age in the area, indicating that there is a magmatic activity of about 2.7Ga in the area.The mantle and marginal zircons have metamorphic recrystallization, both of which except on the cathodoluminescence image , The weighted average ages (2561 ± 18Ma in the mantle, 2539 ± 34a in the margin) and the contents of Th and U are very close to each other, and they are all considered to reflect the tectono-thermal events in the region ~ 2.5Ga together with a large amount of evidence The tectono-thermal event of North China Craton-2.5Ga is an important geological event experienced during the formation and evolution of North China Craton, and the rock before this event has undergone a profound transformation in this geological process.