Dating of gold mineralization for super-large altered tectonite-type gold deposits in Northwestern Jiaodong Peninsula and its implications for gold metallogeny.

In order to understand the genesis of ore deposits, it is fundamental to know the timing of gold deposition. Altered-tectonite-type gold deposits, occurred in northwestern Jiaodong Peninsula, containing several super-large gold ore deposits, is dated by Rb-Sr isochron and K-Ar method for gold-bearing altered tectonites and minerals at 117 similar to 100Ma. This age is significantly younger than that of emplacement of its host intrusions (160 similar to 150Ma for Linglong granites and 130 similar to 126Ma for Guojialing granodiorites), precluding the direct genetic link between gold mineralization and acidic magmatism. The Sr-87/Sr-86 initial ratio suggests that, although ore-forming materials of gold deposits were derived partly from Guojialing granodiorites, there exist other sources. It is, therefore, concluded that this type of gold deposit is not traditionally magmatic hydrothermal genesis, but the product of mixing fluids by meteoric water or manlte-derived C-H-O fluids after the emplacement of granitic and granodioritic intrusions.