长白山天池火山区深部流体成分及其稳定同位素组成

DEEP-SEATED FLUID COMPONENTS AND STABLE ISOTOPIC COMPOSITIONS IN TIANCHI VOLCANIC AREA,CHANGBAISHAN MOUNTAINS

天池火山区深部流体成分和稳定同位素组成特征指示，该区地下有相对独立的四个含水层。２．２ｋｍ以上为冷水层，２．２—３．４ｋｍ、３．５—３．９ｋｍ、４ｋｍ以下分别为上部、中部和深部热水层。现代水热活动均伴随强烈的深源气体释放，碳和氦同位素比值揭示，这些气体属幔源气体，其中仅混入少量大气，壳源物质混染不明显。大规模幔源气体释放主要集中在天池火山湖周围，这表明该区地壳浅部可能存在一定规模的热的幔源岩浆体。据碳同位素地质测温估算，该岩浆体的热变质带顶部距地面约５ｋｍ。气体动态变化显示该岩浆体目前处在不稳定期，值得引起重视。

The features of deep- seated fluid component and stable isotopic compositonsin Tianchi volcanic area indicate that there are four water - bearing formations of every description. They are respectively the cold water aquifer (depth < 2.2 km ), up per, middle and deep-seated geothermal water (depths are separately 2.2-3. 4 km, 3. 5 - 3. 9 km, > 4. 0km). The modern geothermal water activityall associat with strong deep- seated gas discharges. The ratios of the carbon andhelium stable isotopes suggest, these deep-seated gases were mostly derived fromthe mantle- derived magma. Among them there was a little air, and the contamination of the crust source gases was not important. And now the mass mantlederived gas discharges concentrate mainly around the Tianchi caldera lake. It is entirely possible to exist fixed hot mantle-derived magmatic reservoir in shallowcrust there. Based on the carbon isotope geothermometer, the top of magmatic reservoir is 5 km from the land surface in crust. The gas dynamic change moitoringsuggests, this hot magmatic reservoir is instable now, and must take the matterseriously.