The Hetai gold orefield of Guangdong Province,located in the Yunkai area of southern segment of the Qinzhou Bay—Hangzhou Bay Juncture Orogenic Belt (QHJB),is occurred in shear zones. However,the favorable geological conditions and gold mineralization process in the shear zones are in controversy.Methods:Based on the detailed field geological investigation on the Gaocun gold deposit of the Hetai goldfield,we carried out X- ray diffraction (XRD) to study the characteristics of mylonitic sequence in the auriferous shear zones,establish contrast sequence of stresses variety with petrographic composition,and further reveal the ore genesis with shear deformation.Results:The muscovite content ranging from 9% to 40% in the shear zones,progressively increase from protomylonite,via barren and auriferous mylonite,to barren and auriferous ultramylonite.The muscovite in the shear zones was classified as 2M1 type that b0 values range from 5.5505 to 9.9002,and increase from protomylonite,via mylonite,to ultramylonite mylonite,corresponding to low-,medium-,and high-pressure.Therefore,it is deduded that the ore-forming fluids were intensified with the rock deformation extent,resulted in abundant neogenic muscovite or sericite from protomylonite to ultramylonite. However,the auriferous mylonite and ultramylonite present some low-pressure muscovite which is likely associated with the ore-forming fluids in the brittle fissures overprinted the shear zones. Conclusions:It indicates that the mineralization likely experienced two stages: minor sulfides occurred during ductile shearing stage,and economic Au precipitated in brittle fracture stage.Moreover,the quartz content in barren ultramylonite (29.8%) apparently less than mylonite (44.2%) suggests that some ore-forming fluids for the auriferous quartz vein-type ores were likely derived from the ultramylonite as wall rocks.Therefore,the Au mineralization is preferential in ultramylonite to protomylonite and mylonite in the shear zones.