Geology,geochemistry and genesis of the Makou magnetite-apatite deposit in the Luzong volcanic basin,Middle-Lower Yangtze River Valley Metallogenic Belt,Eastern China |
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| Institution: | 1. Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China;2. State Key Laboratory of Continental Dynamics, Northwest University, Xi''an, China;3. Department of Geosciences, University of Tübingen, 72074 Tübingen, Germany;4. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;2. Collaborative Innovation Center for Exploration of Strategic Mineral Resources, Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China |
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| Abstract: | The Middle-Lower Yangtze River Valley Metallogenic Belt (MLYB) is located on the northern margin of the Yangtze Plate (Eastern China). Ore deposits in the belt are mainly clustered in seven ore districts, and are closely associated with Mesozoic intermediate-felsic magmatic rock. Among the seven ore districts, the Luzong and Ningwu districts host large-scale iron resources in volcanic basins. The Makou magnetite-apatite deposit in the southern Luzong Basin was previously interpreted to be related to a quartz syenite porphyry. In this study, we conducted field geological studies and determined the age and geochemistry of the Makou intrusive rocks. Petrography and electron probe micro analysis (EPMA) indicated that the Makou ore-hosting rocks have intense albite alteration. The wallrock alteration is spatially restricted, and comprises albite alteration (Stage I), magnetite mineralization (Stage II), quartz-sulfide alteration (Stage III) and carbonate alteration (Stage IV) stages. Fluid inclusions in syn-mineralization apatite homogenized at 252.2–322.6 °C, which slightly lower than is typical for magnetite-apatite deposits in the region. Field study revealed that the quartz syenite porphyry at Makou disrupted the orebodies along clear-cut intrusive contacts, and that the quartz syenite porphyry does not contain iron mineralization, suggesting it has no direct genetic relationship with the iron mineralization. The ore-hosting albitite and ore-forming biotite diorite have LA-ICP-MS zircon U-Pb ages of 129.6 ± 1.2 Ma and 131.2 ± 3.3 Ma, respectively, and the iron mineralization was dated by mass spectrometer phlogopite 40Ar-39Ar at 130.76 ± 0.77 Ma. We propose that the Makou magnetite-apatite deposit is genetically related to the biotite diorite, rather than to the quartz syenite porphyry in the mine pit. The biotite diorite closely resembles intrusions related to magnetite-apatite deposits elsewhere in the region. |
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| Keywords: | MLYB Luzong Basin Makou magnetite-apatite iron deposits zircon U-Pb ages Albite alteration Biotite diorite |
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