Metallogeny and corresponding mineral deposit model of the Cretaceous terrestrial volcanic-intrusive rocks-related polymetallic iron deposits in Middle-Lower Yangtze River Valley
陆相火山-侵入岩有关的铁多金属矿成矿作用及矿床模型——以长江中下游为例

Most terrestrial volcanic-intrusion related-Cretaceous iron deposits along the Middle-Lower Yangtze River Valley developed in Cretaceous basins whereas a few, such as the Chengchao and Jinshandian skarn iron deposits, occur in uplift area. The mineralization spatially can be divided into two episodes with age ranges of 133~130Ma and 127~125Ma. In light of substance sources and mineralization processes, it can be recognized as four ore systems, i.e. skarn iron deposits in the uplift area (system 1); volcanic-subvolcanism of the Dawangshan (or Zhuanqiao) cycle-related polymetallic iron deposits, comprising apatite-magnetite iron deposit, skarn-like iron deposit, magmatic iron deposit, hydrothermal S-Cu deposit and hydrothermal Pb-Zn deposit (system 2); monzonite and syenite-related skarn iron deposits (system 3); volcanic-subvolcanism of Niangniangshan cycle-related Cu (Au) and Au-U deposits (system 4). Late three systems merely occurred in the Cretaceous volcanic basins. The skarn iron deposits in both basins and uplift area share the same mineralization age and are temporally a little later than the polymetallic iron deposits associated with pyroxene diorite porphyry, and earlier than system 4 of Cu-Au-U mineralization. Based on the apatite-magnetite iron deposit, skarn-like iron deposit and magmatic iron deposit of system 2 and the other types of non-industrial value iron mineralizations, previous researchers proposed a mineral model entitled in "porphyry iron deposit model" with extensive impact in China. In this study based on the porphyry iron mineral model we suggest a polymetallic iron deposit model comprising the major characteristics of the four ore systems. The varied ore systems and ore types are indicators each other for prospecting.