Age of the Jombolok lava field (East Sayan): evidence from dendrochronology and radiocarbon dating     

S.G. Arzhannikov  A.V. Ivanov  A.V. Arzhannikova  E.I. Demonterova  M. Jolivet  V.I. Voronin  V.A. Buyantuev  V.A. Oskolkov 《Russian Geology and Geophysics》2017,58(1):20-36

Dendrochronology and radiocarbon dating, with reference to remote sensing, digital elevation modeling, geological, and geomorphological data, provide new age constraints for the Jombolok lava field in the East Sayan Mountains (Siberia). The Jombolok lava field originated in the latest Late Pleistocene and underwent at least four phases of volcanic activity recorded in lava flows. Two earliest phases followed shortly one after another more than 13 kyr ago. The third phase corresponding to eruptions of Kropotkin volcano can be timed only relatively. The fourth phase has been dated by dendrochronology and AMS ¹⁴C of well-preserved wood buried under the youngest lava which occurs among older lavas near the Jombolok River mouth. The age of this activity is bracketed between the death of trees caused by eruptions 1268-928 years ago and the beginning of new tree growth on the surface of the most recent lavas 900 years ago.  相似文献   

山东临朐-昌乐地区新生代火山岩研究     

张春池  杨恩秀  李秀章  任天龙  朱继托  宁振国 《上海国土资源》2010,31(Z1)

山东临朐-昌乐地区新生代火山岩是新近纪中新世-上新世火山活动产生的大陆溢流玄武岩,分为牛山期、山旺期和尧山期,主喷发期为牛山期和尧山期,属于碱性玄武岩系列。火山岩化学成分由早至晚向富碱、钛、钙,贫硅、镁、锰的方向演化,岩浆分异程度晚期较早期高。岩石内有大量二辉橄榄岩、方辉橄榄岩等幔源包体和透长石、普通辉石、尖晶石等巨晶。玄武岩K-Ar年龄为4.34～18.87Ma。火山岩岩浆来源于上地幔。  相似文献   

Snow-contact volcanic facies and their use in determining past eruptive environments at Nevados de Chillán volcano, Chile     

K. Mee  H. Tuffen  J. S. Gilbert 《Bulletin of Volcanology》2006,68(4):363-376

Studies of the eruptive products from volcanoes with variable ice and snow cover and a long history of activity enable reconstruction of erupted palaeoenvironments, as well as highlighting the hazards associated with meltwater production, such as jökulhlaups and magma-water interaction. Existing difficulties include estimation of ice/snow thicknesses and discrimination between ice- and snow-contact lithofacies. We present field evidence from the Cerro Blanco subcomplex of Nevados de Chillán stratovolcano, central Chile, which has erupted numerous times in glacial and non-glacial periods and most recently produced andesitic lava flows in the 1861–1865 eruption from the Santa Gertrudis cone on the northwest flank of the volcano. The main period of lava effusion occurred during the winter of 1861 when the upper flanks of the volcano were reportedly covered in snow and ice. The bases and margins of the first lava flows produced are cut by arcuate fractures, which are interpreted as snow-contact features formed when steam generated from the melting of snow entered tensional fractures at the flow base. In contrast, the interiors and upper parts of these flows, as well as the overlying flow units, have autobrecciated and blocky textures typical of subaerial conditions, due to insulation by the underlying lava. Similar textures found in a lava flow dated at 90.0±0.6 ka that was emplaced on the northwest flank of Cerro Blanco, are also inferred to be ice and snow-contact features. These textures have been used to infer that a small valley glacier, overlain by snow, existed in the Santa Gertrudis Valley at the time of the eruption. Such reconstructions are important for determining the long-term evolution of the volcano as well as assessing future hazards at seasonally snow-covered volcanoes.  相似文献   

Determination of flow directions by combining AMS and thin-section analyses: implications for Oligocene volcanism in the Kerguelen Archipelago (southern Indian Ocean)     

G. Plenier  P. Camps  B. Henry  B. Ildefonse 《Geophysical Journal International》2005,160(1):63-78

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On the effect of lava viscosity on the magnetic fabric intensity in alkaline volcanic rocks     

F. Hrouda  M. Chlupáčová  K. Schulmann  J. Šmíd  P. Závada 《Studia Geophysica et Geodaetica》2005,49(2):191-212

The degree of the anisotropy of magnetic susceptibility (AMS) of basaltic rocks, as is known from the large AMS database of these rocks, is generally very low, while in more acidic volcanic rocks such as andesites, trachytes and phonolites, which have been investigated much less frequently, it is in general much higher. In the present study, the AMS of various volcanic rocks including trachytic and phonolitic rocks was investigated in the Tertiary volcanic region of the eské stedohoí Mts. Viscosities of the respective lavas were calculated from the chemical composition using the KWARE program. A rough correlation was found between the degree of AMS and lava viscosities, probably resulting from different mechanisms orienting the magnetic minerals. In basaltic lava flows this mechanism is traditionally considered to be of a hydrodynamic nature, in trachytic and phonolitic bodies it can also be represented by quasi-intrusive flows resembling, at least partially, ductile flow deformation. This is in agreement with the AMS data predicted by the viscous (liquid flow) and line/plane (ductile flow) models.  相似文献   

Flow patterns in the Siberian traps deduced from magnetic fabric studies   总被引：3，自引：0，他引：3  

J.-P. Callot  E. Gurevitch  M. Westphal  J.-P. Pozzi 《Geophysical Journal International》2004,156(3):426-430

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Possible lava tube system in a hummocky lava flow at Daund,western Deccan Volcanic Province,India     

Raymond A. Duraiswami  Ninad R. Bondre  Gauri Dole 《Journal of Earth System Science》2004,113(4):819-829

A hummocky flow characterised by the presence of toes, lobes, tumuli and possible lava tube system is exposed near Daund, western Deccan Volcanic Province, India. The lava tube system is exposed as several exhumed outcrops and is composed of complex branching and discontinuous segments. The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at numerous places along the tube. At some places the tube walls exhibit a single layer of lava lining, whereas, at other places it shows an additional layer characterised by smooth surface and polygonal cracks. The presence of a branching and meandering lava tube system in the Daund flow, which represents the terminal parts of Thakurwadi Formation, shows that the hummocky flow developed at a low local volumetric flow rate. This tube system developed in the thinner parts of the flow sequence; and tumuli developed in areas where the tube clogged temporarily in the sluggish flow.  相似文献   

Interpretation of porosity in dacite lava domes as ductile–brittle failure textures     

J. V. Smith  Y. Miyake  T. Oikawa 《Journal of Volcanology and Geothermal Research》2001,112(1-4)

Pores in dacite lavas of three volcanoes in Japan (Unzen, Yakedake and Daisen) have characteristics unlike vesicles. Most of the pores have ragged walls marked by the protrusion of groundmass crystals and phenocrysts. The shapes of these pores range from irregular to planar. Many pores occur in ‘pressure shadows’ adjacent to phenocrysts. Some pores are crack-like and pass around phenocrysts and have blunt terminations. Most of the pores are interpreted as the result of failure of the magma by flow during ductile–brittle transition. This phenomenon, known as cavitation, is well established in hydraulics and the material sciences. Cavitation of the lavas in this study was promoted by steep slope of emplacement, subtle mechanical contrasts between bands, and strain intensification around rigid crystals and lithic fragments. Cavitation in lava can extract volatiles from magma causing premature embrittlement and weakening. Cavitation is inferred to be critical to the initiation of lava-front pyroclastic flows.  相似文献   

跨孔电磁层析技术对桥墩溶岩洞的探测   总被引：2，自引：0，他引：2  

郭贵安 《CT理论与应用研究》2001,10(1):44-51

肇庆大桥位于西江流域，是连接肇庆和珠江三角洲地区的主要干线上的大桥。5个主桥墩位于溶洞和断层破碎带上，以往常用的单桩单孔的方法只能查有10cm直径垂直下方的溶洞分布情况，这种常规的方法难于查明整个桥墩位下方的溶洞分布情况，而且一孔之见难于达到技术要求。近年来发展起来的CT成像技术，正好可以弥补这方面的不足。本次电磁波CT探测法在肇庆大桥5个主桥墩的溶洞探测结果说明，这种方法是可行的，溶洞探测结果还经过最后的钻桩验证。  相似文献   

Comments on ‘Generation of Deccan Trap magmas’ by Gautam Sen     

H. C. Sheth 《Journal of Earth System Science》2002,111(4):483-485

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