Abstract: Petroleum exploration of Hailar-Tamtsag basin is closely paid attention to recently. But the origin of non typical sedimentary rocks and the origin and genesis of Budate group crude oil are still not clear. The study on the mantle fluids, isotopic geochemical provinces, the distribution of low-velocity and high-conductive layers in mid-crust shows that ① the non typical sedimentary rocks as special reservoirs are products of metasomatism among mantle fluids enriched with alkali metals K, Na and alkaline earth metal Mg; ② Sino-Mongolia block as the Pacific-type block has the giant petroleum resource potential; ③ the low velocity-high conductive layer of mid-crust in this basin controls the distribution of oil-gas fields. Therefore, some of the oil and gas in Hailar-Tamtsag basin might belong to the deep inorganic origin. According to this hypothesis, some large oil and gas fields may be found in Budate group buried hill belt.

Key words: Hailar-Tamtsag basin, non typical sedimentary rock, Butate group buried hill, mantle alkaline fluid, isotopic geochemical province, low velocity and high conductive layer, mid-crust, inorganic oil and gas