Central Baiyin Ore zone is tectonically located in the east part of the North Qinlian Caledonian eugeosyncline, which is a convergent residual arc subducting to the south. The magmatic activities in this region were of frenquent and here develops mainly a suite of submarine spilite-keratophyre formation, which can be divided into 4 volcanic cycles showing the basic-acidic-basic eruptive sequence. The spilite-keratophyre formation in chemcal composition, characteristic index and standard mineral contents similar to that of the other areas in the world, but in these characteritics shows difference from the normal basalt. The spilite showing as a curve with larger slope and higher alkalinity is plotted in the upper part of the Rittmann index diagram, while the keratophyre in this diagram is shown as a curve with smaller slope and lower alkalinity. The data of trace elements, oxide contents and their ratios in various rocks indicate that both spilite and keratophyre primarily may be arc basalt of calcic-alkaline series.The REE data for these rocks all show LREE abundance with no Eu depletion, which is coincident essentially with the normalized pattern.The material sources belong to the syntexis transformation crust.The main oxides, trace elements and the REE geochemical feartures mentioned above indicated that tectoic setting of this region may belong to a trough-convergent arc and active continental margin. Having study the syntexis transformative crust and the K-spilite, we suggested, that the volcanic rocks were driven from a relative deep source and formed in a submarine volcanic arc setting away from the trough.