Abstract: Abstract：The Kalatag intrusion is the unique intrusion in the Paleozoic inlier on the southern margin of the Tuha basin. The major element characteristics show that the intrusion belongs to the sodian calc-alkaline series. The rocks are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE) such as Ba, K and La but depleted in high field strength elements (HFSE) such as Th, Nb, P and Ti and have weak negative Eu anomalies and low Sr isotopic ratios and high εNd(t) values (+7.74－+9.13). These characteristics indicate that：(1) the Kalatag intrusion has an affinity for mantle-derived rocks of a subduction zone and probably formed in an island-arc environment；(2)the intrusion was derived from a depleted mantle source and in the main has not suffered from contamination with older continental crustal material and its formation have a direct generic relation to the fractional melting of the north-dipping subducted Kanggur paleo-oceanic plate；and (3)the intrusion can provide the evidence that the south margin of the Tuha basin was an active continental margin during the late part of the Early Paleozoic and that the Kalatag porphyry-type gold-copper deposit is related to the subduction of the paleo-oceanic crust in this area.