Magnetite geochemistry of the Longqiao and Tieshan Fe–(Cu) deposits in the Middle-Lower Yangtze River Belt: Implications for deposit type and ore genesis

摘要

Graphical abstractDisplay OmittedHighlights?The Longqiao mineralization comprises two periods (sedimentary and hydrothermal), whilst the Tieshan Fe–Cu mineralization comprises four stages (skarn, magnetite, quartz-sulfide and carbonate).?Magnetite from the Longqiao and Tieshan deposits has different geochemistry, and can be clearly discriminated by the Sn vs. Ga, Ni vs. Cr, Ga vs. Al, Ni vs. Al, V vs. Ti, and Al vs. Mg diagrams.?Fluid–rock interactions, temperature andfO2may have controlled the magnetite trace element contents of both deposits.?The Longqiao Fe deposit has both sedimentary and hydrothermal features.?The Tieshan Fe–Cu deposit is a typical skarn deposit and may have formed via hydrothermal metasomatism.AbstractMagnetite is a common mineral in many ore deposits and their host rocks, and contains a wide range of trace elements (e.g., Ti, V, Mg, Cr, Mn, Ca, Al, Ni, Ga, Sn) that can be used for deposit type fingerprinting. In this study, we present new magnetite geochemical data for the Longqiao Fe deposit (Luzong ore district) and Tieshan Fe–(Cu) deposit (Edong ore district), which are important magmatic-hydrothermal deposits in eastern China.Textural features, mineral assemblages and paragenesis of the Longqiao and Tieshan ore samples have suggested the presence of two main mineralization periods (sedimentary and hydrothermal) at Longqiao, among which the hydrothermal period comprises four stages (skarn, magnetite, sulfide and carbonate); whilst the Tieshan Fe–(Cu) deposit comprises four mineralization stages (skarn, magnetite, quartz-sulfide and carbonate).Magnetite from the Longqiao and Tieshan deposits has different geochemistry, and can be clearly discriminated by the Sn vs. Ga, Ni vs. Cr, Ga vs. Al, Ni vs. Al, V vs. Ti, and Al vs. Mg diagrams. Such difference may be applied to distinguish other typical skarn (Tieshan) and multi-origin hydrothermal (Longqiao) deposits in the MLYRB. The fluid–rock interactions, influence of the co-crystallizing minerals and other physicochemical parameters, such as temperature andfO2, may have altogether controlled the magnetite trace element contents of both deposits. The Tieshan deposit may have had higher degree offO2, but lower fluid–rock interactions and o