The Hongshi Cu deposit, located in the northern margin of the Dananhu arc in the East Tianshan orogenic belt, was mined in 2011. To date, the deposit contains proven reserves of 0.083 million tonnes Cu metal with an average grade of 0.83 %, presenting the earliest Paleozoic vein-type Cu deposit in the East Tianshan. The vein orebodies are hosted in andesite of Daliugou Formation. The ore-paragenesis of Hongshi Cu deposit can be divided into three stages that consist of quartz-pyrite, quartz-chalcopyrite-pyrite and quartz-calcite-pyrite stages, respectively. Chlorite, pyrite and quartz are produced in each stage, corresponding to, Chl1 (iron chlorite), Chl2 (aluminum chlorite) and Chl3 (magnesium chlorite); subhedral pyrite (Py1), coarse-grained porous pyrite (Py2) and fine-grained pyrite (Py3) and three generations of quartz (Qtz1, Qtz2, and Qtz3). Chlorite major element compositions illustrate that Tschermark substitution [(Si + (Mg2+, Fe2+, Fe3+) <-> Aliv + Alvi)] is an important element substitution mechanism. Three types of chlorite have a narrow range of Fe/(Fe + Mg) ratios, from 0.52 to 0.61 (avg. 0.55), 0.35 to 0.57 (avg. 0.48), and 0.35 to 0.41 (avg. 0.39), respectively. Scandium, Na, B, Ti, Ga, V, Sr, and Sn show a decreasing trend from Chl1 to Chl3. The calculated crystallization temperatures range from 251 degrees C to 357 degrees C for Chl1, 201 degrees C to 270 degrees C for Chl2, and 117 degrees C to 211 degrees C for Chl3, respectively. The calculated logfO2 of three types of chlorites range from -37.25 to -31.20 (Chl1; avg. -36.51), -46.02 to -34.64 (Chl2; avg. -42.17), -46.86 to -41.48 (Chl3; avg. -44.23), respectively. Meanwhile, logfS2 values of three types of chlorites range from -11.58 to -10.96 (Chl1; avg. -11.33), -12.47 to -10.62 (Chl2; avg. -11.74), and -13.60 to -11.75 (Chl3; avg. -12.85), respectively. From Chll to Chl3, oxygen fugacity and sulfur fugacity show a gradually decreasing evolution trend. Chl1 and Chl2 have a relatively wider XFe value range, reflecting a slight fluctuation of the redox state in the Hongshi hydrothermal system. LA-ICP-MS time resolution profiles show relatively flat and stable straight lines for Mg, Al, P, K, Ca, Ti, Ge Li and Na in most quartz samples, indicating that these elements are mainly present in the form of isomorphism. A strong correlation between Si and Ge as well as Si and Ti demonstrate that Ge4+ and Ti4+ can be easily incorporated into quartz to replace Si4+. The highest Al concentrations in Qtz1 reflect more acidic hydrothermal fluid compared with Qtz2 and Qtz3. From the early stage Al-rich quartz to the late stage Al-depleted quartz, suggesting the precipitation of Cu was affected by the pH changes of hydrothermal fluid. This result is inconsistent with the decrease CL intensity from strong to weak, indicating that Ti composition is not the main factor controlling the CL intensity of hydrothermal quartz. Cobalt/Ni and S/Se ratios as well as Co/Sb vs. Se/As diagram of three generations of pyrite indicate a hydrothermal origin. Abundant porous pyrite and trace element ratios (e.g., Ag/As, Bi/Pb, and As/Sb) indicates that