The Danzhai gold-mercury deposit is situated in the eastern region of Guizhou province, southwest of P. R. China.The Danzhai deposit is one of the gold-mercury-antimony-barite deposits in the Sandou-Danzhai ore belt, which is controlled by regional fault system Fi. The host rocks are Upper Cambrian and Lower Ordovician carbonates. Wall rock alteration is dominated by silicification and carbonatization. The major mineral assemblages consist of cinnabar, arsenopyrite, stibnite, pyrite and realgar, orpiment as well as barite. Chemical analyses show that gold is positively correlated with arsenic so that the gold may be mainly associated with arsenic minerals. The Au/Ag ratio is always greater than 1 in the gold ore. Hydrocarbons, particularly bitumen, are abundant in both the host rocks and the ore. The geological characteristics of the Danzhai gold-mercury deposit is quite similar to that of Carlin gold deposit in the western U.S.A except the Danzhai deposit is rich in organic matter and not associated with igneous rocks.A number of gold-mercury-antimony-barite deposits are distributed in or around the Majiang-Danzhai oil trap, and all of these deposits are present under the ancient interface between petroleum and oilfield brine (-500 m). Field observation shows that a variety of forms of hydrocarbon occur not only in the host carbonates but in the ore deposit as well. Patch-like bitumen, veinlet bitumen as well as stylolite-like bitumen host sulfide minerals such as arsenopyrite and cinnabar while metal sulfides such as cinnabar and gangue minerals also host bitumen. Besides bitumen, paraffin wax is also found in the deposit. An organic petrography study demonstrates that the bitumen in the minerals from the deposit is identical to the bitumen in the former Majiang-Danzhai oil trap. The bitumen is actually pyrobitumen, with a high reflectance, a mosaic texture, and an anisotropic nature but without fluorescence. The reflectance of bitumen from the deposit is high, varying from 2 to 3.8%, and the temperature calculated from this reflectance ranges from 150 to 210°C, indicating that the petroleum in the Majiang-Danzhai oil trap reached the thermal natural gas stage.