Fluid sources in the Twangiza-Namoya Gold Belt (Democratic Republic of Congo): Evidence from tourmaline and fluid compositions, and from boron and Rb-Sr isotope systematics

Fluid inclusions in quartz that are texturally associated with hydrothermal tourmaline contain abundant saline brines and CO2-rich fluids that are commonly associated with CH4 and in places with amorphous carbon and N2. We interpret these fluids as having been derived from the hosting sedimentary sequence. This model is in agreement with the observed tourmaline composition, which are most readily affiliated with a variably Ca- and Al-rich pelitic source. Our model based on the isotopic, age and mineral compositional evidence indicates a sedimentary source of fluids forming the tourmaline-bearing hydrothermal veins in Kamituga and Lugushwa.