CONTINENTAL VOLCANIC ROCKS IN THE GREATER KHINGAN MOUNTAINS AND THEIR MINERALIZATION

The earliest continental volcanic rocks in the study area were formed in the Triassic, the Jurassic volcanic rocks are the dominant constituent in the Greater Khingan volcanic belt, and the Cretaceous volcanic rocks represent the uppermost horizon of the Mesozoic volcanic rocks in the Greater Khingan area. From early to later times four eruptive cycles may be distinguished. The composition of the initial magma in each cycle tends to be basic and that of the late-stage magma tends to be acidic-alkaline. The SI valus ranges between 0.8 and 21.2, suggesting that the magma has undergone strong differentiation. There are three types of eruption in the Greater Khingan volcanic belt, the central, fissure and multi-central types. The rocks formed are mainly of eruptive facies and eruptive-sedimentary facies. The remnant volcanic apparatuses include calderas and volcanic domes. The useful products relating to volcanic activity include metallic and nonmetallic minerals as well as hot water resources.