河北张家口水泉沟岩体SHRIMP年代学研究及其意义

SHRIMP chronological study of Shuiquangou intrusive body in Zhangjiakou Area, Hebei Province and its geochemical significance

采用先进的 SHRIMP测年技术对河北水泉沟碱性杂岩体进行了年龄测定，获得东坪金矿区水泉沟岩体二长岩锆石 U- Pb年龄为 (390± 6)Ma，后沟金矿区水泉沟岩体正长岩年龄 (386± 6)Ma，比较可信地确定了水泉沟岩体的成岩时代为晚加里东期—早海西期。这表明北部温都尔庙-西拉木伦河加里东俯冲造山运动强烈地影响本区，水泉沟岩体是这次运动的产物。根据前人测得的东坪和后沟金矿床蚀变围岩钾长石的 Ar- Ar和 K- Ar年龄，金矿化的时代是中生代燕山期，与岩体的成岩年龄有 200 Ma的时差，成因上可能与碱性杂岩体关系不大，因此，东坪和后沟等金矿床可能不属于碱性岩型金矿床。

SHRIMP technique is applied to the age determination of Shuiquangou alkalic complex. Zircons from monzonite and syenite of the complex in the Dongping and Hougou gold mining district are dated at age of (390± 6) Ma and (386± 6) Ma, respectively with U- Pb method. Rock- forming times of the complex is confidently constrained in the Late Caledonian- Early Hercynian period. This implies that Ondor Sum- Xar Moron He Caledonian subduction orogeny influenced the area intensely and resulted in the complex. The former Ar- Ar and K- Ar ages of K- feldspar from the altered host of the Dongping and Hougou gold deposits are confined to the Yanshanian period of Mesozoic Era, 200 Ma younger than the complex and they have no relationship. Therefore, the Dongping and Hougou gold deposits may not be belonged to the alkalic complex- type gold deposit.