下庄糜棱岩的40Ar/39Ar年龄及其成矿意义

下庄铀矿田的糜棱岩按产状可以分为两种，即韧性剪切带中的糜棱岩和硅质碎裂岩带中的糜棱岩，两种糜棱岩具有不同的特征，反映糜棱岩的不同成因和环境。两个测年样确定糜棱岩年龄为140-140Ma，它与晚期花岗岩活动高峰期相近，与早期铀矿化年龄耦合。认为韧性剪切带是早期花岗岩体再度处于假塑性状态下的变形产物，岩石的韧性变形与铀的成矿在时间上和空间上密切相关，控矿因素与成矿机制与韧性剪切变形机制息息相连，这些信息有助于早期铀矿的勘查。

40Ar/39Ar Ages of Xiazhuang Mylonite and Their Metallogenic Implications

According to the geological modes of occurrence, the mylonite in the Xiazhuang uranium orefield may be divided into two kinds, namely mylonite in the ductile shearing zone and that in silicic cataclastic rocks. The two kinds of maylonite have different cha-racteristics, which reflect different geneses and formation environments. The formation ages of mylonite are 140 Ma and 141 Ma (2 samples), colose to those of the peak stage of late granitic magmatic activity and identical to those of the early uranium mineralization. It is suggested that ductile-shearing zones in the area originated from the deformation of earlier granitic body which was in the pseudo-plastic condition again. The ductile deformation of rocks is closely associated with uranium mineralization both in space and time, and the ore-controlling factors are intimately related to the ore-forming mechanism and the ductile-shearing deformation mechanism.Such information is useful in the prospecting and exploration of early uranium mineralization.