The northwestern Hebei gold concentration area is an important component part of the gold metallogenic belt along the northern margin of the North China craton. Most gold deposits in this area occur within the Shuiquangou alkaline intrusive complex or near metamorphic rocks of the Archean Sanggan Group. Based on 40Ar-39Ar isotopic analyses, there is a 120 Ma gap between the ore-forming age (172-188 Ma) of the deposits and the rock-forming age (304-306 Ma) of the Shuiquangou alkaline intrusive complex. Therefore, it may be concluded that the gold deposits are not the product of magmatic hydrothermal fluid. The ore-forming fluid may be composed of the circulating subsurface heated meteoric water and/or metamorphic fluid, and the ore-forming materials were mainly leached and extracted from the alkaline intrusive complex. The Mesozoic Yanshanian tectono-magmatic activities may have provided heat and dynamic energy for the ore-forming processes. So the gold deposits occurring in northwestern Hebei are considered as belonging to reworked hydrothermal gold deposits related to the alkaline intrusive complex.