Abstract: Volcanic rock weathering crust of Carboniferous is the important target for deep oil/gas exploration in hinterland of Junggar basin, which can be divided into sedimentary caprock belt(A), upper weathering crust(B), lower weathering crust(C)and tight volcanic rock belt(D)from top to bottom based on petrology and petrophysical properties of volcanic rock weathering crust from more than 50 wells.Effective pore space exists in B and C belts. According to pore origin of volcanic rock reservoir and its contact with overlying and underlying source rocks, volcanic rock weathering crust in Carboniferous can be divided into four models :①no source rock exists above and below volcanic rock, dominated by freshwater leaching pore ;②source rock occurrs above volcanic rock dominated by freshwater and organic acid denudation pores ;③source rock occurrs below volcanic rock dominated by freshwater denudation pore in upper weathering crust and by organic acid denudation pore in lower weathering crust;④source rock occurrs above and below volcanic rock with co-existence of freshwater and organic acid denudation pores.The study showed that volcanic rock weathering crusts in Carboniferous in Mosuowan anticline, Muhu anticline, Manan anticline and Baijiahai arch identified as the fourth model, are the important targets for oil/gas exploration.

Key words: Junggar basin, Carboniferous, Volcanic rock, Reservoir, Weathering crust, Model