Tin-bearing magnetite with nanoscale Mg-Si defects: Evidence for the early stages of mineralization in a skarn system

Tin-bearing magnetite is reported from several types of magmatic-hydrothermal ore deposits. The question whether tin incorporated within solid solution, as Sn 4+ , or nanoinclusions remains open, however. We report a micron- to nanoscale investigation (Mg, Si)-bearing serpentinite in the Dulong Zn-Sn-In skarn, South China, with dual aims understanding mechanisms involved accommodating and associated elements into Fe-oxide, inferences that this carries for constraining early stages skarn formation. Magnetite preserves range textures record evolution metasomatism during prograde growth grain cores retrograde rim replacement. Observations reveal presence chondrodite sellaite (MgF 2 ) inclusions preserved magnetite. This implies initiation mineralizing system humite-bearing, magnesium stage. Magnesium-Si defects, forming along (110) planes prior Sn-enrichment, are recognized first time. Release high volatile, F-rich fluids interpreted lead precipitation cassiterite <111*> directions