Ore-forming Factors And Metallogenic Prediction Of Makeng Iron Ore, Southwestern Fujian Province

Located in the Late Paleozoic depression of southwestern Fujian of southeastern Cathaysia block, Makeng iron ore is the main skarn iron polymetallic deposit. In order to reveal the ore-controlling factors and ore genesis, we conducted comprehensive research and discussed the ore-bearing beds, magmatic construction and orecontrolling structure factors, and carried on research on metallogenic model and metallogenic prediction of Makeng type iron ore. The main research contents and conclusions are as follows:1. Based on the comprehensive analysis of ore-controlling factors of Makeng Fe deposit, we determined Lindi formation(C1l), Jingshe-Qixia formations(C2j-P2q) and Wenbishan formation(P2w) as the mainly ore-bearing beds, and we thought that the major ore bodies are generally controlled by lithologic boundaries and tectonic structural planes, especially the interface between silica and calcareous bed.2. It yielded weighted 206Pb/238 U ages of 125~145 Ma and 125~155 Ma for Dayang and Juzhou granite respectively, indicating they are complex rock bodies. These granites have highly fractionated I-type geochemical signatures with high Na2O+K2O, and Rb contents. It shows different traces of geochemical elements and Hf isotopic features between Juzhou and Dayang granites. We thought that Juzhou granite had closer relation with Maekng Fe deposit than Dayang granite according to the distribution of mineralization and alteration.3. The diabase shows well relationship with Makeng Fe deposit, and it yielded U-Pb ages of 315 Ma and 135~146 Ma. Their geochemical and isotopic characteristics reveal that region mafic wall formed in the intraplate extensional environment. The mineralization and alteration zoning is well developed around diabase dykes, indicating their close relationship with iron ore mineralization. Metallogenic specialization and tectonic environment research results of these diabase indicates the close relationship between diabase and iron ore bodies, so we thought that the widespread diabase rocks may provide a part of Fe metallogenetic materials.4. We carried on tectonic background research of Makeng type iron ore, and confirmed the ore-controlling structures(nappe structure, detachment structure and fold structures). Magnetic fabric research of deformed rocks shows the multi-phase alternating stretching and extruding structural evolutional phases, and we thought that the alternating structural evolution may be an important ore-controlling factor because it provides metallogenic space and benefits the enrichment of mineralize material.5. Based on the understanding of ore-controlling factors of Makeng iron ore, we established metallogenic model and ascertained prospecting indicators(Si/Ca interfaces, diabase, etc.). We carried on the metallogenic prediction research about Makeng type iron ore, and hold on idea that the Liushuba- Guoluoping, Gualu-Shanpingtou, Makeng- Zhongjia, Huodekeng- Yubao and Shiqiao- Lujiadi areas have prospecting potential of Makeng-type iron ore deposits.