Results Of Weekly Chemical And Isotopic Monitoring Of Selected Springs In Norris Geyser Basin, Yellowstone National Park During June-September, 1995.
Results Of Weekly Chemical And Isotopic Monitoring Of Selected Springs In Norris Geyser Basin, Yellowstone National Park During June-September, 1995.
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1995 年 6 月至 9 月期间对黄石国家公园诺里斯间歇泉盆地选定泉水进行的每周化学和同位素监测结果。
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发表时间：
2002
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通讯作者：
C. J. Janik
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作者：
R. Fournier;U. Weltman;D. Counce;L. D. White;C. J. Janik
每年在诺里斯间歇泉盆地，通常在8月或9月，都会发生广泛的热液“扰动”，其特点是许多泉水的流量特征同时发生变化，特别是在后盆地。在1995年夏季期间，每周从诺里斯分布广泛的八个温泉和间歇泉采集水样并进行分析，以确定在扰动发生时热水中是否也发生了化学和同位素变化。此外，位于诺里斯间歇泉盆地西南5.8公里处的长臂猿峡谷的绿柱石泉也被纳入监测项目。受监测的四个温泉和间歇泉排出的水似乎来自相对较深的水库，这些水库的温度至少为270摄氏度，可能高于300摄氏度。在1995年扰动开始时和之后的几天里，这四个特征排放的通常是中性氯化物的水都带有一种酸性硫酸盐成分，并变得同位素更重。酸性-硫酸盐成分似乎与100春季平原排放的一些水在成分上相似，后者来自温度在170-210°C的地下区域。然而，100春季平原地区排放酸性氯化物-硫酸盐水的两个监测泉水对年度扰动没有任何明显的化学或同位素响应。绿柱石温泉和诺里斯的两个中性氯化物温泉似乎是从温度为250摄氏度或更低的水库取水，也没有对年度扰动表现出任何显著的化学或同位素反应。在一年一度的骚乱开始后，从后盆地Double Bulger间歇泉采集的水样中的氯离子浓度从约800ppm增加到约1500ppm，几乎是之前报道的黄石公园热水中氯离子浓度的两倍。这种水的同位素组成排除了高氯离子在大气压下蒸发的来源。解释这种高浓缩水独特化学和同位素组成的一种方法是，将在上流(减压沸腾)过程中经过一次绝热冷却的水再循环回到水热系统，在那里它被重新加热到220摄氏度以上，然后在随后的上流过程中，这些先前沸腾的水经历额外的减压沸腾循环。双膨胀水独特的化学和同位素组成可能演化的另一种方式是由于上升流通道内流体压力的降低而导致地层中的过度沸腾。诺里斯间歇泉盆地的年度扰动一般似乎是由热液系统内沸点曲线的周期性上下移动触发的，以响应与该热液系统相邻并相互关联的冷水的电位面的变化。在诺里斯间歇泉盆地很容易发现的年度扰动现象在黄石国家公园的其他地方可能不容易识别，因为(1)诺里斯的中性氯化物水域直接从温度更高、压力更高的水库(诺里斯为270℃至>；300℃，而上间歇泉盆地为180-215℃)上升，这些水库能够产生大量高压蒸汽；(2)使诺里斯的温泉和间歇泉水变得浑浊的粘土，预示着扰动的开始，来自酸性蚀变岩，这种岩石广泛分布在诺里斯的中等深度，在其他间歇泉盆地中是罕见的。黄石国家公园(YNP)诺里斯间歇泉盆地介绍，一年一度的热液“扰动”通常发生在8月下旬或9月，其特征是许多温泉浊度增加，水和蒸汽排放增加，池水温度剧烈波动，有时还会发生小型热液爆炸(White和其他人，1988年)。在年度扰动时，也观察到了从Norris后盆地Cistern Spring收集的水中的化学变化(图1)(Fournier和其他人，1986)。1976-1985年水池泉水的长期月度采集和化学分析
Each year at Norris Geyser Basin, generally in August or September, a widespread hydrothermal "disturbance" occurs that is characterized by simultaneous changes in the discharge characteristics of many springs, particularly in the Back Basin. During the summer season of 1995, water samples from eight widely distributed hot springs and geysers at Norris were collected each week and analyzed to determine whether chemical and isotopic changes also occurred in the thermal waters at the time of the disturbance. In addition, Beryl Spring in Gibbon Canyon, 5.8 km southwest of Norris Geyser Basin, was included in the monitoring program. Waters discharged by four of the monitored hot springs and geysers appear to issue from relatively deep reservoirs where temperatures are at least 270 °C and possibly higher than 300 °C. At the time of, and for several days after, the onset of the 1995 disturbance, the normally neutral-chloride waters discharged by these four features all picked up an acid-sulfate component and became isotopically heavier. The acid-sulfate component appears to be similar in composition to some waters discharged in 100 Spring Plain that issue from subsurface regions where temperatures are in the range 170–210 °C. However, the two monitored springs that discharge acid-chloride-sulfate waters in the 100 Spring Plain region did not show any significant chemical or isotopic response to the annual disturbance. Beryl Spring, and two neutral-chloride hot springs at Norris that appear to draw their water from reservoirs where temperatures are 250 °C or less, also did not show any significant chemical or isotopic response to the annual disturbance. After the start of the annual disturbance, chloride concentrations in water sampled from Double Bulger Geyser in the Back Basin increased from about 800 ppm to about 1500 ppm, nearly twice as high as any previously reported chloride concentration in a thermal water at Yellowstone. The isotopic composition of that water precludes an origin of the high chloride by evaporation at atmospheric pressure. One way to account for the unique chemical and isotopic composition of this highly concentrated water is by recirculation of water that had gone through one cycle of adiabatic cooling during upflow (decompressional boiling) back down into the hydrothermal system, where it is reheated to greater than 220 °C. This previously boiled water then undergoes additional cycles of decompressional boiling during subsequent upflow. Another way the unique chemical and isotopic composition of Double Bulger water might evolve is by excess boiling in the formation that results from a decrease in fluid pressure within the channels of upflow. The annual disturbance at Norris Geyser Basin generally appears to be triggered by a cyclic up and down movement of the boilingpoint curve within the hydrothermal system in response to changes in the potentiometric surface of the cold water that is adjacent to, and interconnected with, that hydrothermal system. Annual disturbance phenomena that are easily recognized at Norris Geyser Basin may not be easily recognized elsewhere in Yellowstone National Park because (1) the neutral-chloride waters at Norris ascend directly from higher-temperature and higherpressure reservoirs (270 to >300 °C at Norris compared to 180–215 °C at Upper and Lower Geyser Basins) that are capable of producing massive amounts of high-pressure steam, and (2) the clay that makes hot spring and geyser waters become turbid at Norris, heralding the start of the disturbance, comes from acid altered rocks that are widely distributed at intermediate depths at Norris, and that are rare in other geyser basins. INTRODUCTION At Norris Geyser Basin, Yellowstone National Park (YNP), an annual hydrothermal "disturbance" occurs, generally in late August or September, that is characterized by increased turbidity in many hot springs, increased discharge of water and steam, extreme fluctuations in temperatures of pools, and sometimes small hydrothermal explosions (White and others, 1988). Chemical changes at the time of the annual disturbance also have been observed in waters collected from Cistern Spring in the Back Basin of Norris (Fig. 1) (Fournier and others, 1986). Long-term monthly collections and chemical analyses of water from Cistern Spring during 1976–1985