Relationship between intrusive rocks and gold mineralization of the Anjiayingzi gold deposit, Inner Mongolia and its implications for geodynamics
内蒙古安家营子金矿与侵入岩的关系及其地球动力学意义

The Anjiayingzi gold mine, an intermediate-size deposit located in the Chifeng-Chaoyang gold-concentrated area in the north margin of the North China craton, is hosted in the Anjiayingzi granite, and is spatially associated with rhyolitic porphyry . The granite is geochemically characterized by rich-LREE, depleted-HREE, relative high initial 87Sr/86 Sr ratio, and high Ba and Sr contents, indicative of a deep-source of the granite magma. These geochemical features are consistent with those of the granitoids that are closely related to gold mineralization in eastern Shandong Province, whereas are contrast to those of early-formed Kalaqin granite and post-gold mineralization rhyolite dikes. Zircon U-Pb dates suggest that the Anjiayingzi granite was formed at 132 ~ 138 Ma, and the rhyolite dike that cut gold lodes was formed at 125 ~ 127 Ma. Therefore, gold mineralization in the area is constrained at 126 ~ 132 Ma. This timing of gold mineralization is coeval with the Mesozoic geodynamic regime reverse of the North China Craton. Researches suggest that the geodynamic reverse in the North China Craton took place during early Mesozoic time, such as changing of tectonism from compression to extension and thinning of the lithosphere to a peak at that time and causing much more extensive and intensive magmatism. Most gold deposits were formed during the reverse period, which indicates that gold mineralization is probably related to these deep processes. That is to say along with going up of mantle materials and energy, metallogenic elements including Au were reactivated and transported to upper crustal level, and then deposited at preferred structural sites.