Gabbro-norite masses in Yuxian, Shanxi:characteristics and ore potential

Two facies belts may be discriminated for the gabbro-norite masses in Yuxian, Shanxi:the marginal facies consisting of altered medium-to fine-grained gabbro and the central facies composed of altered medium-to coarsegrained gabbro. The m/f ratios range between 0.41 and 2.10, indicating a kind of ferruginous basic rocks. The albitized gabbro-norite from the study area is characterized by higher Na contents (Na₂O=4.98%) and lower Fe contents (TFe=3.36%), while their protoliths fine-grained gabbro-norite by lower Na contents (Na₂O=1.02%) and higher Fe contents (TFe=11.64 -14.94%), implying that the activation, migration and enrichment of Fe were caused by albitization. The lower part of the ore-bearing rocks has higher electrical resistivity, lower polarizability and strong magnetism. The vanado-titano-magnetite deposits and metallic sulphide deposits may be emplaced in the basal and marginal parts of the gabbro masses.