Abstract: Hydrogeochemical anomalies of mud volcanoes and springs in the North Tians-han were found before and after the June 30,2012 Xinyuan-Hejing M_s6.6 earthquake in Xinjiang Uyger autonomous region, China. Water samples from the hot springs and mud volcanoes were collected 4-days before and after the earthquake, and hydrogeochemical par rameters were measured. The data indicate that water from mud volcanoes are brine with weak alkaline and low temperatures, whose chemical type is CI-Na and may originate from the meteoric water stored in the closed structures and react with the surrounding rock complex. Water from springs is fresh with weak alkaline and medium temperatures, whose chemical type is SO4·Cl-Na, probably owing to the deep circulation of the ground-water along the faults. The Anjihai mud volcano showed coseismic anomaly, with temper ature (T), total dissolved solids (TDS),K⁺,Na⁺ and Ca²⁺ increasing greatly after the . earthquake. Mud volcanoes in Dushanzi, Baiyanggou and Aiqigou showed pre-seismic a-nomaly, with the T, TDS, conductivity(EC),Na⁺ and CI^-increasing, and K⁺,Ca²⁺ and Mg²⁺ decreasing before the earthquake in Dushanzi and Baiyanggou mud volcanoes. In Aiqigou mud volcano, there were significantly decreases in K⁺ and Mg²⁺,but Ca²⁺ in-creased by 223%. For the Shawan No. 25 spring, there were significantly decreases in TDS, EC, K⁺,Na⁺,Ca²⁺,Mg²⁺, CI^-and $SO_{4}^{2-}$ but the temperature decreased by 7℃. These results may help earthqua ke tendency analysis and improvement of hydrogeochemi-cal monitoring methods.

Key words: Hydrogeochemical changes, Mud volcanoes, hot spring, The June 30, 2012 Xinyuan earthquake