Microscopic study of Ma On Shan iron ore deposits

Abstract

Ma On Shan iron mine was one of the largest mine in the old times of Hong Kong. The iron ore deposit was formed as a skarn deposit in the contact zone between the dolomite to calcite marble from Devonian to Carboniferous and the fine grained Granite from Middle Jurassic to Early Cretaceous. Intrusion of the granitc pluton introduced hot mineral-rich fluids to the carbonate protolith, leading to the formation of skarn through metamorphic and/or metasomatic process. The main ore minerals in the ore deposit consist mainly of magnetite and hematite. Previous researches on the ore deposits mainly focused on the field study with limited microscopic study. A recent dissertation project in 2013 included a petrologic study with the help of optical microscope and scanning electron microscope, however, some common minerals mentioned by previous authors were not found in his study. This study aims at filling the gap of prograde minerals information and updates the skarn mineral assemblages of Ma On Shan Skarn Deposits.