长白山天池火山近期气体地球化学的异常变化

气体地球化学监测结果显示,2002—2003年地幔来源CO2、He和CH4的含量出现明显的异常变化;2003年火山区深断裂型泉群逸出气体He的3He/4He比值都出现了异常升高,2004年该比值明显降低。热储型长白聚龙泉群逸出He中3He/4He比值2003年上升缓慢,2004年持续上升,其中逸出He中幔源He含量在2004年明显增加。2002—2004年天池火山区逸出气体及其He同位素异常变化与该区地震活动呈一定的对应关系,其中锦江泉群在2004年下半年地震活动趋势减弱后,异常明显减弱;而长白聚龙泉群在地震活动减弱后,异常反而明显增加,显示热储型泉群岩浆来源气体异常释放明显滞后于深断裂型泉点。上述异常特征对识别和判定火山区深部岩浆异常活动及预测未来火山地震可能有重要意义

RECENT GEOCHEMICAL CHANGES OF HOT-SPRING GASES FROM TIANCHI VOLCANO AREA, CHANGBAI MOUNTAINS, NORTHEAST CHINA

The recent fluid monitoring shows that mantle-derived CO_2,He and CH_4 content increased anomalously in 2002 and 2003. The 3He/4He ratio of deep-fault-type Jinjiang hot springs increased highly anomalously in 2003, and than decreased in 2004. That ratio from thermal-reservoir-type Changbaijulong hot springs increased slowly in 2003, and also increased continuously in 2004. Mantle-derived He content of releasing He from Changbaijulong springs increased obviously in 2004. The changes of releasing gases and He isotope corresponded to the trend of seismic activities in Tianchi volcanic area to a certain extent between 2002 and 2003. The abnormal release of Jinjiang decreased apparently after the seismic activities decreased in next half year of 2004, but the abnormal release from Changbaijulong increased highly after these seismic activities. It shows that the abnormal release of magmas-derived gases from thermal-reservoir-type springs lags behind that of the deep-fault-type springs. These characteristics are of great significance for identifying deep magmatic activity and predicting volcanic earthquake in the future.