地热温泉井与土壤逸出气中痕量氢的特征及差异性分析

地下氢气是反映地壳应力应变灵敏的气体地球化学组分,逸出气痕量氢是一项新型的气体地球化学观测手段,在我国很多省份进行了试观测。本项目实现逸出氢在高温自流井和土壤中的连续、并行观测,重点对痕量氢的动态变化特征进行分析,研究其差异性,并讨论温泉地热井逸出氢高值突跳异常的成因。经频谱分析发现地热温泉井中的逸出氢与土壤中逸出氢都存在日变,前者的浓度与井水位、水温有关,与地表环境因素无关,而后者主要受地表环境因素影响。庐江地震台地热温泉井逸出氢浓度的高值突跳来源于深部水体上涌过程中的气泡携带,为非震兆异常。     

温泉逸出气体常规成分快速测定

通过对腾冲火山地球化学观测站中用气相色谱仪对火山区温泉逸出气体成分的观测实践的理论总结,系统介绍了用气相色谱仪对温泉逸出气体常规成分的快速测定方法.结果表明,SP3400型气相色谱仪具有一系列优点.通过合理的仪器配置、参数设置、规范的运行维护和分析操作,SP3400型气相色谱仪可以快速准确地分析温泉逸出气体中He、H_2、O_2、N_2、CH_4、CO_2等常规组分的含量.对这些组份总量分析的相对偏差只有1.89%,对CO_2组份分析的相对偏差只有2.18%,对He、H_2等ppm级含量的组份分析的相对偏差分别只有10.24%和11.44%,说明SP3400的型气相色谱仪的测试结果有相当高的可靠性和准确性.SP3400型气相色谱仪为温泉逸出气体常规组分快速测定的理想仪器,可以在火山和地震监测台站推广使用.     

长白山天池火山地震活动与西北太平洋俯冲带内中深源地震关系的研究

根据长白山火山活动的地球动力学背景,综合分析西北太平洋俯冲带俯冲作用所引起的中深源地震与长白山火山地震活动及温泉流体化学气体释放变化趋势的关系。认为在北纬35°以北,西北太平洋板块俯冲作用引起的地幔对流的扰动作用下,长白山火山活动从1999年至目前大体经历了3个阶段:1999年6月至2002年5月为扰动起始阶段,2002年6月至2004年为扰动增强阶段,2005年至目前为扰动衰减阶段。在分析了3个阶段内长白山火山地震活动及温泉气体释放特征的基础上,讨论了长白山天池火山目前的活动状态。从日本海至中国东北深源地震区地震活动期和平静期存在的韵律性活动过程出发,对长白山天池火山未来喷发的可能性进行了分析     

中国火山温泉气体地球化学特征及其在火山监测中的应用

中国火山温泉主要分布在吉林长白山、云南腾冲和黑龙江五大连池等火山区。这些火山虽然处于休眠状态,但大面积的温泉分布指示着岩浆房存在的可能性。本文总结了前人研究成果,分析了中国主要火山区温泉气体地球化学特征,并探讨了温泉气体在火山监测中的应用。长白山、腾冲和五大连池火山区温泉气体地球化学性质类似,都以CO₂为主要气体,含量在80%以上,最高可达99%以上,其它气体组分包括CH₄、N₂、O₂、SO₂、H₂S、He和H₂等。长白山火山温泉气体中氦同位素比值（3He/4He）最高,约为4—6R_A,CO₂中碳同位素比值（δ13C）为-7.9‰—-1.3‰,CH₄中碳同位素为-48.0‰—-28.7‰;腾冲火山温泉气体氦同位素比值为3—5.5R_A,CO₂中的碳同位素为-6.49‰—-2.07‰,CH₄中碳同位素为-23.5‰—-9.3‰;五大连池火山温泉气体氦同位素比值约为3R_A,CO₂中的碳同位素比值为-9.6‰—-3.1‰,CH₄中碳同位素为-47.2‰—-44.4‰。3个火山区的温泉气体均显示地幔来源的岩浆气体特征,并在上升运移过程中受地壳或古俯冲物质的影响。     

长白山天池火山地热区逸出气体的物质来源

根据天池火山地热区逸出气体的化学成分和稳定同位素组成,讨论了这些气体的物质来源.提出该区逸出气体主要源自壳内幔源岩浆残留体;长白地热区可能与古火山喷发通道相连,其下方有一稳定的地热水和深源气储库,储库热水温度约(166±9)℃;锦江地热区逸出气体可能是通过活动构造带快速由深部向地表迁移的.     

黑龙江中西部跨断层土壤氢气初步分析

地质构造运动多伴随地下气体的逸出,观测并研究地下逸出气体,会抓住某些地下构造活动信息。作为地球化学观测的灵敏指标之一,地下逸出的氢气能够指示断裂活动的过程。地处松辽盆地黑龙江中西部地区多年来已开展多期跨断层土壤氢气野外测量工作,利用积累的观测数据,初步分析该地区跨断层土壤氢气背景动态变化及构造活动、地震活动特征,以便为地震孕育过程中断层氢气演化异常判定提供依据,为建立区域地震短期预测动态方法提供思路。     

张家口南部地区活动断裂带气体地球化学特征

本文从实际观测资料出发,阐述了张家口南部地区活动断裂带气体地球化学特征,讨论了活动断裂带以温泉形式释放的气体成分与区域地质、水文地质条件等因素的关系,对选择地震观测点和观测项目提出了看法。     

我国地震构造地球化学监测研究现状

正地球化学是研究地球的化学组成、化学作用和化学演化的科学。基于研究目的的不同,地球化学目前有元素地球化学、气体地球化学、同位素地球化学、构造地球化学、水文地球化学等研究方向。近些年来随着便携式化学测试仪器的普及,又衍生出构造地震地球化学-依据气体地球化学、同位素地球化学及水文地球化学相关理论方法,通过流动观测网、温泉或热水井固定观测点,来观测断裂带不同区段的深浅部流体地球化学特征及不同组分的物质来源,构     

哥伦比亚马钦火山热液系统:2011～2013年期间观测到的新岩浆信号

近年来(2009～2013年)哥伦比亚马钦火山出现了新的地震活动。为了改善火山监测系统,本文通过分析该地区火山喷气孔和温泉的化学成分及同位素组成,研究了火山排放的流体地球化学特征。由于火山喷气孔中下部液相分离,导致穹丘中上部的喷气孔亏损δD和δ~(18)O(与大气降雨补给的流体相比)。在2011～2013年期间,发现喷气孔有很明显的岩浆成因He,同时排放的液体中岩浆的贡献量也有所增加,证实了地震活动性的增强。地球化学和地震资料都显示马钦火山已经苏醒,说明该火山仍然处于活跃期,值得我们对其活动性进行重点监测。     

滇西地震预报实验场水文地球化学背景及区划特征

本文系统总结了滇西地震预报实验场不同热水区内,温泉常量组分、微量元素、放射性元素,气体组分和稳定同位素的地球化学背景并对可能的控制因素进行分析;揭示了水文地球化学背景分布与场区活动断裂的空间关系和水文地球化学背景高低与场区断裂活动强度的相关关系。     

Magma at depth: a retrospective analysis of the 1975 unrest at Mount Baker,Washington, USA

Mount Baker volcano displayed a short interval of seismically-quiescent thermal unrest in 1975, with high emissions of magmatic gas that slowly waned during the following three decades. The area of snow-free ground in the active crater has not returned to pre-unrest levels, and fumarole gas geochemistry shows a decreasing magmatic signature over that same interval. A relative microgravity survey revealed a substantial gravity increase in the ~30 years since the unrest, while deformation measurements suggest slight deflation of the edifice between 1981–83 and 2006–07. The volcano remains seismically quiet with regard to impulsive volcano-tectonic events, but experiences shallow (<3 km) low-frequency events likely related to glacier activity, as well as deep (>10 km) long-period earthquakes. Reviewing the observations from the 1975 unrest in combination with geophysical and geochemical data collected in the decades that followed, we infer that elevated gas and thermal emissions at Mount Baker in 1975 resulted from magmatic activity beneath the volcano: either the emplacement of magma at mid-crustal levels, or opening of a conduit to a deep existing source of magmatic volatiles. Decadal-timescale, multi-parameter observations were essential to this assessment of magmatic activity.     

腾冲火山活动监测,预测与对策研究中的若干重要问题

《膳冲火山活动监测、预测与对策研究》项目是一项集火山活动监测研究、防灾及资源综合开发与利用为一体的系统工程。需要火山地质、地震、地球化学、地球物理、地壳形变及地热等诸多相关学科的合理配置和联合攻关。在过去的３０年,众多学和研究实体对腾冲火山进行 大量的观察和研究获得一批与火山活动的相关的基础研究成果。其中也不乏说明腾冲火山存在在喷发危险性的证据。为了保证本重大项目能在有限时间内及有限的人力、财务     

Increased activity on Ebeko Volcano, Paramushir I., North Kurils in 2005–2006

In recent years the gas hydrothermal activity of Ebeko Volcano has been characterized by a constant heat flow and a constant chemical composition of water and fumarole gases. The volcano’s activity suddenly increased on January 27, 2005. Two high-output steam-gas jets 5 m across formed in the Active Funnel of the North Crater. A new high-output, high-temperature, fumarole field originated in the funnel in July 2005. Changes have been recorded in the chemical composition of fumarole gases. Ratios between individual components of the gas were calculated, with the ratios being geochemical precursors of eruptions for the volcano under study. Based on these results and on the very fact of increased fumarole activity on Ebeko, an intermediate-term forecast of explosive eruptions has been developed. Atmospheric contamination by a toxic gas (hydrogen sulfide) is described. It was previously thought that toxic gases pose a short-lived threat only to the population of the town of Severo-Kuril’sk because of frequent strong winds prevailing there. It is shown that the presence of a snow cover during increased activity on Ebeko sharply enhances the hazard of contamination by toxic gases, the hazard being constant both on the volcano itself and in the Severo-Kuril’sk area.     

浅述五大连池火山区浅层气体钍、氡与断裂构造和火山活动的关系

在五大连池火山区流体化学研究原有工作的基础上，对火山群的重要区段开展了野外踏勘、气体普查，特别是用放射性气体测量方法对火烧山、老黑山、笔架山、药泉山等火山区进行了Tn、Rn测量。通过大量实测资料，分析和研究了Tn、Rn等气体和火山、火山活动、断裂构造、断裂活动性及其他地质条件的关系，初步查明了五大连池火山区的气体组成特征、分布和形成规律，对地下主要气体的成因、气体和火山构造活动及其它地质条件的关系进行了初步探讨，并提出了对五大连池火山区气体观测的初步设想和建议。     

The weathering and element fluxes from active volcanoes to the oceans: a Montserrat case study

The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles arc. The silicate weathering may have consumed 1.3% of the early CO₂ emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat are a net sink for atmospheric CO₂ due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as a source or sink for atmospheric CO₂ is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism. This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island’s inhabitants.     

以物理模型为指导开展中尺度地震预测试验场研究

震源物理的研究进展表明：地震预测工程不仅是高科技问题,更重要的是需要以正确的物理模型作为指导。地震预测试验场的研究可以从气象学、地球物理、地球化学、矿山地震和瓦斯突出的研究中获得许多启示。在今后的十年中,要注意流体,特别是超临界流体在地震成因中的作用。地震试验场应有明确物理思路,形成多种物理方法的实质性格局,改变自由进出、过于分散的情况。建议除在京津、川滇等建立构造地震预测研究试验场外,还可以利用矿山、火山作为中尺度地震试验场。     

Relatively short-term correlation among deformation,degassing, and seismicity: a case study from Concepción volcano,Nicaragua

Concepción is a frequently active composite volcano in Nicaragua, and is located on Ometepe Island, within Lake Nicaragua. Significant eruptive activity took place at this volcano between March and May 2010, consisting of ash and gas explosions (VEI 1–2). We compare geodetic baseline changes observed with global positioning system (GPS), sulfur dioxide flux (SO₂), and seismic amplitude (SAM) data collected at Concepción during April – June, 2010, and February – April, 2011. Time series analysis reveals a remarkable correlation among the data sets during 2010, when the volcano was erupting. In contrast, the volcano was at its background level of activity in 2011 and the statistical correlation among the time series is not significant for this period. We explain the emergence of correlation among the time series during eruptive activity through modeling of the GPS data with emplacement of a magma column in an open conduit. In the model, magma rose in the conduit, between May 5 and 14, 2010, from a shallow reservoir located at ～ 1.8 km depth. Later, between May 24 and 31, 2010, the top of the magma column descended to almost 600 m depth, corresponding to the cessation of eruptive activity. Thus, cross-correlation and an integrated analysis of these geophysical time series on a timescale of days helps to reveal the dynamics of the magma plumbing system operating below Concepción volcano.     

Geochemistry of fluids associated with the 1995–1996 eruption of Mt. Ruapehu, New Zealand: signatures and processes in the magmatic-hydrothermal system

The 1995–1996 eruption of Mt. Ruapehu has provided a number of insights into the geochemical processes operating within the magmatic-hydrothermal system of this volcano. Both pre-eruption degassing of the rising magma and its eventual intrusion into the convective zone of the hydrothermal system beneath the lake were clearly reflected in lake water compositions. The eruptions of September–October 1995 expelled the lake, and provided the first-ever opportunity to characterise gas discharges from this volcano. The fumarolic discharges revealed compositions typical of andesite volcanoes and strong interaction with the enclosing meteoric and hydrothermal system fluids. Some 1.1 MT of SO₂ gas was released from the volcano between September 1995 and December 1996, whereas ca. twice this amount (2.2 MT equivalent SO₂) was erupted as soluble (i.e. leachable) oxyanions of sulphur. Significantly more sulphur was released from the volcano over this period than can be accounted for from the magma volume actually erupted. The evidence suggests that a sizable component of the evolved sulphur was remobilised from the long-lived hydrothermal system within the volcano during the 1995–1996 activity.     

Steady-state operation of Stromboli volcano,Italy: constraints on the feeding system

Stromboli volcano has been in continuous eruption for several thousand years without major changes in the geometry and feeding system. The thermal structure of its upper part is therefore expected to be close to steady state. In order to mantaim explosive activity, magma must release both gas and heat. It is shown that the thermal and gas budgets of the volcano lead to consistent conclusions. The thermal budget of the volcano is studied by means of a finite-element numerical model under the assumption of conduction heat transfer. It is found that the heat loss through the walls of an eruption conduit is weakly sensitive to the dimensions of underlying magma reservoirs and depends mostly on the radius and length of the conduit. In steady state, this heat loss must be balanced by the cooling of magma which flows through the system. For the magma flux of about 1 kg s^-1 corresponding to normal Strombolian activity, this requires that the conduits are a few meters wide and not deeper than a few hundred meters. This implies the existence of a magma chamber at shallow depth within the volcanic edifice. This conclusion is shown to be consistent with considerations on the thermal effects of degassing. In a Strombolian explosion, the mass ratio of gas to lava is very large, commonly exceeding two, which implies that the thermal evolution of the erupting mixture is dominated by that of the gas phase. The large energy loss due to decompression of the gas phase leads to decreased eruption temperatures. The fact that lava is molten upon eruption implies that the mixture does not rise from more than about 200 m depth. To sustain the magmatic and volcanic activity of Stromboli, a mass flux of magma of a few hundred kilograms per second must be supplied to the upper parts of the edifice. This represents either the rate of magma production from the mantle source feeding the volcano or the rate of magma overturn in the interior of a large chamber.