The unclear relationship between mineralization, hydrothermal alteration, and rock magnetization in volcanogenic massive sulfide (VMS) deposits limits us from fully understanding the magnetic anomalies and remagnetization process in this type of deposit. We address the issue by conducting systemic paleomagnetic, rock magnetic, petrographic, and X-Ray diffraction studies in the Dapingzhang VMS deposit on the northwestern Indochina Block. Magnetite is the dominant magnetic carrier of hydrothermally altered surrounding rocks and orebody. Magnetite consumption and secondary magnetite formation occurred at different stages and types of hydrothermal alteration. The overall decrease in magnetite concentration from chloritization via silicification to mineralization implies that the magnetite was mostly consumed during hydrothermal alterations. Secondary single domain magnetite, which can carry a remagnetization direction, is proposed to be formed during illitization via the smectite-to-illite transformation. Secondary superparamagnetic magnetite, which was most likely formed during the late stage of chloritization, is unable to carry the stable characteristic remanent magnetization. The site-mean direction of high-temperature and high-coercivity components is D_g/I_g = 324.5°/43.1°, and k_g = 35.1, with α₉₅ = 6.8° before tilt correction, and D_s/I_s = 316.2°/37.6°, and k_s = 16.4, with α₉₅ = 10.1° after tilt correction, with a negative fold test. However, plate reconstruction is limited by the uncertainty of the tilting process following mineralization and the possibility of remagnetization during burial alteration. Therefore, this study provides a mechanism for rock magnetic variation and remagnetization during VMS mineralization.

Article link: https://doi.org/10.1029/2022JB025020