Deep Meteoric Water Circulation and Magmatic Fluid Discharge at an Active Volcano

通过对日本九州久州-岩山火山深层循环地热水和富马罗蒸汽凝析物的氢氧同位素研究，证实了深层循环地热水存在明显的地下沸腾现象。(1)单级和连续蒸汽分离导致剩余液氯化物和同位素含量差异较大。由于在高温下相分离，温泉的氘含量高于补给水，部分氧同位素的移位可能是由于沸腾和水岩反应引起的。在温泉水中所观察到的氯化物、氧-18和氘的最高含量被认为是深层热水在其临界点单级蒸汽分离时在浅层沸腾的结果。氯化物、氧-18和氘的含量较低可能是由于热水在多级蒸汽分离下沸腾，再加上大气水的稀释。(2)进一步提出部分大气水在通过火山的水文循环过程中被加热到水的临界点，形成单相煤层。富玛罗缩合物的δ - δ ^<18>O、δ - cl和δ ^<18>O- cl的线性关系似乎是火山深处岩浆蒸汽和源自大气水的超临界蒸汽混合的结果。(3)富马醛缩合物氚含量表明水蒸气区大气水循环停留时间短（约6年），而温泉水区大气水循环停留时间长（超过100年）。因此，可以认为富马酚排放物来自火山中含有蒸汽主导区的主水循环系统，而温泉排放物必须来自围绕蒸汽主导系统的液态水循环子系统。(4)高温溶液中硫水解可能是温泉水中强硫酸形成的一种可能机制。通过硬石膏-水体系热液实验，研制了一种利用其主要化学成分测量强酸性温泉水的新型地温计。少

Significant subsurface boiling of the deep circulating geothermal waters in Kuju-Iwoyama Volcano, Kyushu, Japan, was demonstrated by the hydrogen and oxygen isotopic study of hot spring waters and fumarolic steam condensates.(1) Single-stage and continuous steam separations result in greatly different chloride and isotope contents of remaining liquid. Because of phase separation at high temperatures, deuterium contents of hot spring arehigher than those recharge waters, and part of the observed oxygen isotope shift may be due to boiling as well as water-rock reactions. The highest contents of chloride, oxygen-18 and deuterium observed in hot spring waters are considered to have resulted from boiling at shallow levels under single-stage steam separation of deep thermal water at its critical point. The lower contents of chloride, oxygen-18 and deuterium may have resulted from boiling under multi-stage steam separation of thermal waters, coupled with dilution with meteoric waters.(2) Thus … More , we proposed that part of meteoric water is heated to the critical point of water during a hydrologic cycle through the volcano, forming a single-phase seam. The linear deltaD-delta^<18>O,deltaD-Cl, and delta^<18>O-Cl relationships for fumarolic condensates appear to have resulted from mixing at depths of the volcano between a magmatic steam and the super-critical steam of meteoric water origin.(3) The tritium contents in fumarolic condensates suggest a short residence time (within about 6 years) of meteoric water circulating in the steam region, while those in hot spring waters are corresponded to a very long residence time over 100 years for the liquid region. The fumarolic discarge, therefore, is considered to be from the main water circulation system containing a vapor-dominated zone in the volcano and the hot spring discharge must be from the subsystem of liquid water circulation surrounding the vapor-dominated system.(4) A sulfur hydrolysis in high temperature solution may occur as a possible mechanism of the formation of strongly sulfuric acid in the hot spring water. The new geothermometer for strongly acidic hot spring water by using its main chemical composition was developed by hydrothermal experiments of anhydrite-water system. Less