40Ar/39Ar Geochronology of the Yongning Ductile Shear Zone in the Southeastern Margin of Yunkai Terrain, Yangchun, Guangdong
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摘要: 吴川-四会断裂带内的永宁韧性剪切带是云开地块的东南边界，查明该剪切带形成时代对于研究区域地质演化及韧性剪切带型金矿成因具有重大意义。构造运动学特征分析表明，永宁韧性剪切带具有左行逆冲剪切的特征。本文通过对永宁韧性剪切带糜棱岩中的白云母开展单矿物40Ar-39Ar定年，获得坪年龄为227.38 ~ 232.77 Ma，等时线年龄为229.94 ~ 232.47 Ma，表明永宁韧性剪切带形成于晚三叠世早期，为印支期第一阶段活动的产物，多期活动的北东向剪切带在空间上直接或间接控制了银金矿床的分布。Abstract: The Yongning ductile shear zone within the Wuchuan-Sihui fault zone is the southeastern boundary of the Yunkai Massif, and the determination of the age of the formation of this shear zone is of great significance to the study of regional geological evolution and the genesis of ductile shear zone type gold deposits. Tectonic kinematic characterization indicates that the Yongning ductile shear zone is characterised by left-slip thrusting shear. In this paper, we carried out the 40Ar/39Ar dating on single mica grains from the Yongning ductile shear zone, and obtained the plateau ages of 227.38 ~ 232.77 Ma and the isochron ages of 229.94 ~ 232.47 Ma, indicating that the Yongning ductile shear zone was formed in the early Late Triassic and was a product of the first stage of Indosinian event. The multi-stage active NE shear zone controlled the distribution of Ag-Au deposits directly or indirectly.
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