The Pangkuam deposit is a large-sized copper-gold deposit newly discovered in Laos. Previous studies held that the gold mineralization in the study area was closely related to the magmatic activity with the subduction of the Paleo-Tethys oceanic plate and crust vanishing; nevertheless, such an argument has not been supported by convincing geochemical evidence. In the study area, 13 samples of volcanic rock and intrusive rock were collected in order to analyze the content of main elements, trace elements and rare earth elements (REE). The research result shows that the andesitic intrusive rocks have the geochemical features of calc-alkaline volcanic rocks in an island arc environment. Tectonic discrimination diagram indicates that the rocks belong to an oceanic arc environment, related to the subduction of the oceanic plate. The formation process occurred in an oceanic subduction zone. The magma of volcanic rock and intrusive rock originated from the mantle wedge with crystallization differentiation. The lamprophyre was formed by the mantle melting, which was enriched during the plate subduction. Based on a comparison with the geochemical features of REE and trace elements of several deposits in Chatree magmatic belt, the authors hold that volcanic rocks and gold deposits in the two mining areas originated from the same stage of tectonomagmatic mineralization process. The result has further demonstrated that there existed an important regional mineralization process at the Loei tectonic magmatic belt in the Late Permian-Early Triassic period.