Study on Volcanic Facies of Haerjiawu Formation in Malang Sag

By use of slice identification,core observation and logging identification,Haerjiawu formation volcanic in Malang sag is classified as lava and pyroclastic rock,concluding 23 kinds of specific rocks,such as basalt,andesite and part of intermediate-basic transition rocks,basalt is the main type.By combining logging and seismic,volcanic lithofacies can be divided into 5 categories and 8 subfacies.The result shows that effusive facies is the main lithofacies in the study area.In profile,volcanic lithofacies include 3 modes.The planephasing shows explosion facies is mainly concentrated in the vicinity of the crater,distributing as beads-strings along the dominating fracture.Excessive facies distributes in the lateral of explosion fasies and along the fracture,volcanic sedimentary facies mainly distributes between the subsags and low-lying area of volcanic institutions.