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211.
Keith A. Horton Glyn Williams-Jones Harold Garbeil Tamar Elias A. Jeff Sutton Peter Mouginis-Mark John N. Porter Steven Clegg 《Bulletin of Volcanology》2006,68(4):323-327
A miniaturized, lightweight and low-cost UV correlation spectrometer, the FLYSPEC, has been developed as an alternative for
the COSPEC, which has long been the mainstay for monitoring volcanic sulfur dioxide fluxes. Field experiments have been conducted
with the FLYSPEC at diverse volcanic systems, including Masaya (Nicaragua), Poás (Costa Rica), Stromboli, Etna and Vulcano
(Italy), Villarica (Chile) and Kilauea (USA). We present here those validation measurements that were made simultaneously
with COSPEC at Kilauea between March 2002 and February 2003. These experiments, with source emission rates that ranged from
95 to 1,560 t d−1, showed statistically identical results from both instruments. SO2 path-concentrations ranged from 0 to >1,000 ppm-m with average correlation coefficients greater than r
2=0.946. The small size and low cost create the opportunity for FLYSPEC to be used in novel deployment modes that have the
potential to revolutionize the manner in which volcanic and industrial monitoring is performed. 相似文献
212.
Yuri Taran Tobias P. Fischer Boris Pokrovsky Yuji Sano Maria Aurora Armienta Jose Luis Macias 《Bulletin of Volcanology》1998,59(6):436-449
The 1982 eruption of El Chichón volcano ejected more than 1 km3 of anhydrite-bearing trachyandesite pyroclastic material to form a new 1-km-wide and 300-m-deep crater and uncovered the
upper 500 m of an active volcano-hydrothermal system. Instead of the weak boiling-point temperature fumaroles of the former
lava dome, a vigorously boiling crater spring now discharges / 20 kg/s of Cl-rich (∼15 000 mg/kg) and sulphur-poor ( / 200 mg/kg
of SO4), almost neutral (pH up to 6.7) water with an isotopic composition close to that of subduction-type magmatic water (δD=–15‰,
δ18O=+6.5‰). This spring, as well as numerous Cl-free boiling springs discharging a mixture of meteoric water with fumarolic
condensates, feed the crater lake, which, compared with values in 1983, is now much more diluted (∼3000 mg/kg of Cl vs 24 030 mg/kg),
less acidic (pH=2.6 vs 0.56) and contains much lower amounts of S ( / 200 mg/kg of SO4, vs 3550 mg/kg) with δ34S=0.5–4.2‰ (+17‰ in 1983). Agua Caliente thermal waters, on the southeast slope of the volcano, have an outflow rate of approximately
100 kg/s of 71 °C Na–Ca–Cl water and are five times more concentrated than before the eruption (B. R. Molina, unpublished
data). Relative N2, Ar and He gas concentrations suggest extensional tectonics for the El Chichón volcanic centre. The 3He/4He and 4He/20Ne ratios in gases from the crater fumaroles (7.3Ra, 2560) and Agua Caliente hot springs (5.3Ra, 44) indicate a strong magmatic contribution. However, relative concentrations of reactive species are typical of equilibrium
in a two-phase boiling aquifer. Sulphur and C isotopic data indicate highly reducing conditions within the system, probably
associated with the presence of buried vegetation resulting from the 1982 eruption. All Cl-rich waters at El Chichón have
a common source. This water has the appearence of a "partially matured" magmatic fluid: condensed magmatic vapour neutralized
by interaction with fresh volcaniclastic deposits and depleted in S due to anhydrite precipitation. Shallow ground waters
emerging around the volcano from the thick cover of fresh pumice deposits (Red waters) are Ca–SO4–rich and have a negative oxygen isotopic shift, probably due to ongoing formation of clay at low temperatures.
Received: 21 July 1997 / Accepted: 4 December 1997 相似文献
213.
The relationships between soil gas emissions and both tectonic and volcano-tectonic structures on Mt. Etna have been studied.
The investigation consisted of soil CO2 flux measurements along traverses orthogonal to the main faults and eruptive fissures of the volcano. Anomalous levels of
soil degassing were found mainly in coincidence with faults, whereas only 49% of the eruptive fissures were found to produce
elevated CO2 soil fluxes. This result suggests that only zones of strain are able to channel deep gases to the surface. According to this
hypothesis, several previously unknown structures are suggested. Based on our geochemical data, new structural maps of different
areas of Etna are proposed. The soil CO2 fluxes observed in this study are higher than those measured in a 1987 study, and they are consistent with the higher level
of volcanic unrest during the current study.
Received: 20 March 1998 / Accepted: 17 June 1998 相似文献
214.
沽源—多伦盆地火山岩类和花岗岩类同位素地质年代学及铀成矿条件研究 总被引:4,自引:1,他引:3
本文对沽源-多伦盆地火山岩类和花岗岩类进行了同位素地质年代学和铀成矿条件的系统研究。确定了该区张家口组、花吉营组火山岩类均属早白至世产物,其形成年龄为125—135Ma。指出本区花岗岩浆活动有前海西期、海西期、印支期和燕山期,不存在文献中提到的自北而南分布的3条东西向海酉期花岗岩浆活动带。本文还指出该区区域铀成矿作用具有多期次的特点,同一矿床铀成矿作用的叠加是形成富铀矿体的前提。该区火山岩类钠含量较低,对铀成矿不利。然而,在不利的地质背景中局部存在利于铀成矿的地段和岩性,应作为今后重点的找矿对象。 相似文献
215.
Agronomic impact of tephra fallout from the 1995 and 1996 Ruapehu Volcano eruptions, New Zealand 总被引:2,自引:0,他引:2
Eruptions from Ruapehu Volcano on 11 and 14 October 1995 and 17 June 1996 distributed at least 36×106 m3 of sulphur(S)-rich tephra over the central and eastern North Island of New Zealand. The tephras added between 30–1500 kg
ha–1 S to at least 25 000 km2 of land in primary production. Smaller but beneficial amounts of selenium (Se) and in some areas potassium and magnesium
were also supplied. Addition of S to the soils in the form of sulphate and elemental S resulted in a drop in soil pH and an
increase in pasture S contents within seven weeks of the eruptions. The soils affected by the tephra are naturally low in
S and Se, but following the eruptions S was not required in fertilizer applications in many areas. The strongest and longest
lasting effects of S and Se deposition were in high anion-retention soils particularly Hapludands (moist, moderately weathered
soils, derived from volcanic ash). Soluble fluorine concentrations within the tephras were low compared to historic Icelandic
and Chilean examples. However, pastoral livestock deaths were apparently caused by fluorosis in addition to starvation when
tephra covered feed. The Ruapehu tephra contained very low concentrations of other soluble toxic elements.
Received: 17 January 1997 · Accepted: 31 March 1997 相似文献
216.
The features of seismic activity on Stromboli are discussed and compared in terms of their relationship with the main changes of volcanic activity from 1990 to 1993.We considered a statistical approach for our data analysis. Cluster analysis was used to seek out classes of spectra which might characterize the condition of the volcanic system. The classes we have found provide insights into a scenario which evolves through different phases of volcanic activity, from paroxysms to low activity. We show that episodes of lava effusion and lava fountaining are heralded by variations in the spectral features of tremor after a preparation time. This result highlights the importance of tremor, and reveals that long-term observations are key to examine slow modifications in a volcanic system such as Stromboli, characterized by open conduits, and persistent explosive activity. 相似文献
217.
Harmonic tremor is widely studied and modelled in a very narrow frequency band (1–5 Hz) which represents the eigenfrequencies of a resonator assumed as the source of the phenomenon. Minimal effort was dedicated towards understanding its behaviour in larger temporal scales. Here we characterise the dynamic behaviour of volcanic tremor while evaluating the complete spectrum of the generalised dimension of the phase space. The starting time series constitutes the tremor amplitude picked every 10 minutes. The choice of this lag time is made on the basis of a qualitative analysis of the properties of the tremor. The results show intermittent behaviour of the dynamics which requires an 8-dimensional map to be completely described. An interesting result is that the maximum clustering of point density in phase space occurs in a monodimensional space which implies a periodicity sometimes observed experimentally. An appropriate predictive model needs more constraints on the nature of the eight variables involved in the process. 相似文献
218.
铁矿浆、斑岩铜矿和海相火山岩铜矿均是火山-岩浆作用的产物。铁矿浆通常形成于构造环境从引张发展至挤压过程中并以挤压条件为主时,介于斑岩铜矿和海相火岩岩铜矿的成矿条件之间,其成因及时分布与斑岩铜矿更加密切,多出现于陆相或海陆交互相环境。 相似文献
219.
广东梅县嵩溪早侏罗世火山活动及其地质构造与成矿意义 总被引:2,自引:0,他引:2
从熔岩——玄武岩的岩石学、岩石化学、微量元素、稀土元素和锶同位素组成,以及火山旋回中玻璃碎屑岩诸方面特征,详细地研究了下侏罗统含矿层位内海底基性火山活动,阐述矿区玄武岩形成环境为夭折的大陆裂谷前期地壳槽形裂陷地堑系——裂陷槽。并讨论该裂陷槽环境中基性火山活动的银锑成矿意义 相似文献
220.
试论我国东部火山岩型铀矿床赋存层位的地质时代 总被引:1,自引:1,他引:1
我国东部火山岩型铀矿床基本上都产在侏罗、白垩系中。本文在尽可能吸取国内这方面地层研究新成果的基础上,结合自己的研究成果,对有关矿床的赋存层位的地质时代进行探讨。 相似文献