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1.
粒度组分是影响黄土震陷的重要因素之一。通过采集新疆艾其沟泥火山泥质碎屑喷出样品和泥火山发育区域出露的沉积剖面泥质碎屑样品,利用激光粒度分析测试的实验方法对样品进行粒度测试,分别对样品中值(Md)、均值(Mz)、标准偏差(σφ)、偏度(SK1)、峰度(KG)等粒度参数进行分析。研究结果显示:艾其沟泥火山泥质沉积物粒度组分中以粉粒为主,占56%左右,黏粒含量约为44%,粒度分布以偏众数,正偏态;周缘沉积剖面样品粒度组分以粉粒为主,占60%~70%左右,黏粒含量差异较大,部分地层沉积物中黏粒含量在15%~20%之间,极细粒含量占10%,粒度特征与天山黄土类型相似。黄土内黏粒含量影响其抗震陷性,含黏粒黄土抗震陷性能随黏粒含量的增加而增加。经泥火山沉积改造后的沉积粒度表现为黏粒组分显著增多,因此泥火山活动对沉积物的改造将粉质黄土逐渐向黏质黄土过渡,而黏质黄土的稳定性较高,从而提高了沉积物的抗震陷性能,但是黄土抗震陷性受多因素影响,定量分析泥火山活动对场地地震陷灾害的影响还需要进一步研究。 相似文献
2.
北天山泥火山位于新疆天山北麓山前拗陷带内,均处在背斜褶皱的轴部。在了解泥火山的地质背景、活动现状的基础上,对该区泥火山进行了详细的野外考察,对所采样品进行粒度、显微形貌及成分分析。研究发现:该区域的泥火山样品粒径主要集中在0.3~100μm,平均值相近,分选较差,分布对称性呈极正偏。矿物颗粒以石英、长石为主,基质为黏土矿物,白杨沟和艾其沟样品中均含有铁矿物质。根据上述分析结果对北天山泥火山成因机制进行了初步探讨,认为该区域的泥火山物源相同,泥浆最深来源于下中侏罗统,地层压力以构造活动为主。目前泥火山处于弱活动期,短期内造成较大灾害的可能性很小。 相似文献
3.
2012年6月30日新源-和静MS6.6地震前后, 北天山泥火山出现了喷溢和地球化学异常变化. 该地震前、 后4天内两次观测了北天山泥火山, 采集了两批温泉和泥火山气体样品, 测定了样品的气体组分和He、 Ne同位素及CH4、 CO2的碳同位素组成. 结果表明, 泥火山发生了同震喷发, 气体排放量增加, 温泉和泥火山气体出现了不同程度的微量气体浓度异常, 独山子泥火山震前出现了3He/4He高值异常. 研究结果有利于确定利用泥火山和温泉监测地震活动的方法和指标. 相似文献
4.
湖泊沉积物粒度分析前处理过程中絮凝现象的消除方法研究 总被引：1，自引：0，他引：1
采用激光粒度仪对湖泊沉积物进行粒度分析时需要进行必要的前处理.在有效去除有机质与碳酸盐颗粒的同时,需要消除细粒泥沙质样品中絮凝现象对粒度分析结果造成的误差或错误.本文以武汉三角湖表层沉积物样品为例,采用X射线粉晶衍射(XRD)对其矿物组成和粘土矿物种属进行鉴定,并采用全自动激光粒度仪对样品进行粒度分析.X射线粉晶衍射结果表明样品中非粘土矿物主要为石英与长石,粘土矿物以伊利石、高岭石、绿泥石为主;粒度分析结果显示样品中小于30μm组分占94.5%.这些特征表明该样品易于在前处理过程中形成絮凝.本次研究采用单因素寻优法探讨了超声震荡、分散剂、洗酸对于以伊利石、高岭石、绿泥石为主、平均粒径较小的样品消除絮凝现象的最佳条件.研究结果表明,针对此类样品消除絮凝现象的最佳条件为:超声震荡时间应选择6~8 min,分散剂浓度为20 g/L左右,同时在粒度分析之前需要对样品进行洗酸. 相似文献
5.
呼伦湖地区扎赉诺尔晚第四纪湖泊沉积物的磁化率变化及其影响因素 总被引：11，自引：1，他引：11
呼伦湖盆地扎赉诺尔晚第四纪湖泊沉积物为砂，泥质碎屑沉,地东露天矿剖面沉积物样品进行了低，高频磁化率测量，粒度分析，磁性矿物成分鉴定和Al2O3 ,Fe2O3含量分析，分析表明，磁铁矿是沉积物磁化率的主要贡献者，全铁含量控制了磁化率值的变化，磁化率与沉积物粒度呈负相关，进一步讨论认为，磁性矿物主要为粉砂－粘土级碎屑，集中分布在细粒沉积物中，因此造成其率较高，砂质沉积物中频率磁化率较高，其原因可能是其中的磁性颗粒比粉砂一粘土级沉积物中的磁性颗粒更细一些。 相似文献
6.
新疆独山子泥火山喷发新疆维吾尔自治区地震局王道、李茂伟、李锰、戴晓敏等四人于１９９５年８月４日至８月８日对独山子泥火山进行了详细的现场考察研究，摄制了录像片，采集了喷出物：土、水和气体的样品，获得了十分宝贵的泥火山活动的资料。独山子泥火山位于新疆石油... 相似文献
7.
在系统介绍中国新疆北天山地区和台湾南部地区泥火山研究进展的基础上, 对其地质特征进行了对比分析。结果显示, 北天山和台湾南部地区的泥火山均沿着断裂带分布, 主要位于背斜轴部, 泥火山分布区地层多出露为含泥岩层。对两个地区泥火山喷出物物理特征进行了对比分析, 固体喷发物的矿物成分相似, 如石英、 蒙脱石等; 液体喷出物的泥浆温度与冒泡频率相近, 但最大气泡直径与气体流量有很大差别。又分别对两地区液体、 气体喷出物的化学特征进行了对比分析, 液体喷出物均盐度高; 甲烷是大多数泥火山喷发气体的主要成分, 一些泥火山喷发的气体主要是二氧化碳。区域构造地质和气候条件不同, 导致两地泥火山喷出物存在差异。从现有研究来看, 两地泥火山的喷发都是岩层的孔隙压力增大造成的。两个地区泥火山与当地地震活动之间表现出良好的对应关系。泥火山的地球化学参数可能是地震活动的潜在指标。 相似文献
8.
2012年6月30日新源-和静Ms6.6地震前后,新疆北天山地区的泥火山及温泉出现了明显的水化学异常。在地震前后4天内,采集了两批泥火山和温泉水样品,测定了泥火山和温泉水样的水化学参数。资料表明,泥火山喷溢水属于低温、弱碱性咸水或盐水,水化类型为CI-Na,来源于储存在封闭构造中并与干旱海相、河湖相沉围岩发生了漫长而复杂水岩作用的大气降水。温泉水为中温、弱碱性SO4·CI-Na型淡水,形成于地表水沿断裂深循环过程中的水岩作用。安集海泥火山出现同震喷溢,震后泥水温度(T)、总矿化度(TDS)、K+、Na+及Ca2+大幅上升;独山子、白杨沟及AM02泥火山为震前喷溢,独山子、白杨沟泥火山表现为T.TDS、EC、Na+、CI的升高和K+、Ca2+、Mg2+的降低;AM02泥火山K+、Mg+明显降低,Ca2+上升达223%。震后沙湾25号泉T降低7℃, TDS、电导率(EC)、K+、Na+、 Ca2+、 .Mg2+、CI-及$SO_{4}^{2-}$升高。研究结果可用于北天山地区的地震趋势分析和改进利用各泥火山、温泉进行北天山地区地震活动性监测的水化学方法。 相似文献
9.
新疆北天山地区泥火山与地震 总被引：9，自引：0，他引：9
泥火山是特定地质构造-水文地质环境下的一种构造流体地质现象,在世界上的分布较熔岩火山少。泥火山的出现通常与生油气带有关。据报道,在阿塞拜疆共和国、格鲁吉亚共和国、土库曼斯坦共和国及俄罗斯的塔曼半岛和肯切半岛等地都有泥火山广泛分布[1]。1948年10月5日土库曼斯坦共和国首都阿什哈巴德市发生7.3级地震时,在极震区引起泥火山重新活动;1959年12月17日巴库泥火山突然喷发时,又有有感地震伴随发生[1],可见,泥火山活动与地震活动有一定的成因联系。本文将对新疆北天山地区泥火山的动态及其与地震活动的关系作一分析。1 北天山地区泥… 相似文献
10.
本文利用人工制作的不同含量分散泥质和层状泥质砂岩岩心样品,测量不同矿化度和不同含油饱和度的岩心电阻率,从实验角度研究了不同泥质分布形式和含量的岩心导电规律,结果表明,泥质分布形式或含量不同,则泥质砂岩导电规律不同.基于层状泥质与分散泥质砂岩的并联导电实验规律,以及分散粘土和地层水混合物的导电规律可用HB电阻率方程描述,建立了考虑泥质分布形式影响的泥质砂岩电阻率模型.通过1组不同泥质分布形式泥质砂岩人造岩心实验数据的测试,表明该模型可以描述分散泥质砂岩、层状泥质砂岩和混合泥质砂岩地层的导电规律.分散泥质,层状泥质,人造岩样,实验测量,并联导电,HB方程,电阻率模型 相似文献
11.
Simon J. Barker Melissa D. Rotella Colin J. N. Wilson Ian C. Wright Richard J. Wysoczanski 《Bulletin of Volcanology》2012,74(6):1425-1443
Pyroclastic deposits from four caldera volcanoes in the Kermadec arc have been sampled from subaerial sections (Raoul and Macauley) and by dredging from the submerged volcano flanks (Macauley, Healy, and the newly discovered Raoul SW). Suites of 16–32?mm sized clasts have been analyzed for density and shape, and larger clasts have been analyzed for major element compositions. Density spectra for subaerial dry-type eruptions on Raoul Island have narrow unimodal distributions peaking at vesicularities of 80–85%, whereas ingress of external water (wet-type eruption) or extended timescales for degassing generate broader distributions, including denser clasts. Submarine-erupted pyroclasts show two different patterns. Healy and Raoul SW dredge samples and Macauley Island subaerial-emplaced samples are dominated by modes at ~80–85%, implying that submarine explosive volcanism at high eruption rates can generate clasts with similar vesicularities to their subaerial counterparts. A minor proportion of Healy and Raoul SW clasts also show a pink oxidation color, suggesting that hot clasts met air despite 0.5 to >1?km of intervening water. In contrast, Macauley dredged samples have a bimodal density spectrum dominated by clasts formed in a submarine-eruptive style that is not highly explosive. Macauley dredged pyroclasts are also the mixed products of multiple eruptions, as shown by pumice major-element chemistry, and the sea-floor deposits reflect complex volcanic and sedimentation histories. The Kermadec calderas are composite features, and wide dispersal of pumice does not require large single eruptions. When coupled with chemical constraints and textural observations, density spectra are useful for interpreting both eruptive style and the diversity of samples collected from the submarine environment. 相似文献
12.
The distribution of clasts deposited around a volcano during an explosive eruption typically contoured by isopleth maps provides important insights into the associated plume height, wind speed and eruptive style. Nonetheless, a wide range of strategies exists to determine the largest clasts, which can lead to very different results with obvious implications for the characterization of eruptive behaviour of active volcanoes. The IAVCEI Commission on Tephra Hazard Modelling has carried out a dedicated exercise to assess the influence of various strategies on the determination of the largest clasts. Suggestions on the selection of sampling area, collection strategy, choice of clast typologies and clast characterization (i.e. axis measurement and averaging technique) are given, mostly based on a thorough investigation of two outcrops of a Plinian tephra deposit from Cotopaxi volcano (Ecuador) located at different distances from the vent. These include: (1) sampling on a flat paleotopography far from significant slopes to minimize remobilization effects; (2) sampling on specified-horizontal-area sections (with the statistically representative sampling area depending on the outcrop grain size and lithic content); (3) clast characterization based on the geometric mean of its three orthogonal axes with the approximation of the minimum ellipsoid (lithic fragments are better than pumice clasts when present); and (4) use of the method of the 50th percentile of a sample of 20 clasts as the best way to assess the largest clasts. It is also suggested that all data collected for the construction of isopleth maps be made available to the community through the use of a standardized data collection template, to assess the applicability of the new proposed strategy on a large number of deposits and to build a large dataset for the future development and refinement of dispersal models. 相似文献
13.
We present palaeomagnetic data obtained from large clasts collected in non-welded pyroclastic deposits from Montagne Pelée volcano (Martinique Island, West Indies). These deposits, dated by the 14C method from 5000 yr BP to the present, comprise block- and ash-flows, ash- and pumice-flows and pumice fallouts. Alternating fields treatment was as a routine chosen to demagnetise large samples for which the magnetisation was measured with a specially designed inductometer. The mean directions obtained from block- and ash-flow deposits of the 1902 and 1929 eruptions are in good agreement with the expected geomagnetic directions at these times in Martinique. The so-called P1 eruption (∼1345 AD), which is characterised by a rarely observed transition from a Peléean to a Plinian eruptive style, allows a direct comparison of the palaeomagnetic directions obtained from the three types of pyroclastic deposits. All deposits provide identical mean directions, which further demonstrates the suitability of the non-welded pyroclastic deposits for geomagnetic secular variation study with a very good accuracy and precision. The possibility of using pyroclastic deposits is promising for obtaining a wider distribution of sampling sites, which may better allow us to constrain our knowledge on the geomagnetic secular variation. We find that large geomagnetic changes occurred in Martinique during the last millennium, while the variations appear more limited prior to this period. 相似文献
14.
《Journal of Volcanology and Geothermal Research》2007,159(1-3):198-209
Cora Maar is a Quaternary volcano located to the 20 km northwest of Mount Erciyes, the largest of the 19 polygenetic volcanic complexes of the Cappadocian Volcanic Province in central Anatolia. Cora Maar is a typical example of a maar-diatreme volcano with a nearly circular crater with a mean diameter of c.1.2 km, and a well-bedded base surge-dominated maar rim tephra sequence up to 40 m in thickness. Having a diameter/depth ratio (D/d) of 12, Cora is a relatively “mature” maar compared to recent maar craters in the world.Cora crater is excavated within the andesitic lava flows of Quaternary age. The tephra sequence is not indurated, and consists of juvenile clasts up to 70 cm, non-juvenile clasts up to 130 cm, accretionary lapilli up to 1.2 cm in diameter, and ash to lapilli-sized tephra. Base surge layers display well-developed antidune structures indicating the direction of the transport. Both progressive and regressive dune structures are present within the tephra sequence. Wavelength values increase with increasing wave height, and with large wavelength and height values. Cora tephra display similarities to Taal and Laacher See base surge deposits. Impact sags and small channel structures are also common. Lateral and vertical facies changes are observed for the dune bedded and planar bedsets.According to granulometric analyses, Cora Maar tephra samples display a bimodal distribution with a wide range of Mdφ values, characteristic for the surge deposits. Very poorly sorted, bimodal ash deposits generally vary from coarse tail to fine tail grading depending on the grain size distribution while very poorly sorted lapilli and block-rich deposits display a positive skewness due to fine tail grading. 相似文献
15.
Summary The application of the progressive thermal demagnetization procedure of volcanic rock debris has been frequently used to determine the emplacement temperatures of pyroclastic deposits and thus to characterize the nature of these volcanic deposits. This debris consists of a mixture of juvenile fragments derived from the explosive fragmentation of erupting magma and an assortment of lithic clasts derived mainly from the walls of a volcanic conduit, as well as from the ground. The temperature at which the clasts were deposited can be estimated by analyzing its remanent magnetization. To do this, oriented samples of clasts are subjected to progressive thermal demagnetization and the directions of the resulting remanent vectors provide the necessary information. Clasts of basalt, andesite, limestone, pumice and homebricks have previously been used to estimate the emplacement temperatures of pyroclastic deposits. According to our data, clasts of red sandstones also seem to be good carriers of thermoremanent magnetization. We have carried out a paleomagnetic study on a Quaternary, lithic-rich, massive, pyroclastic deposit from the Puig d'Adri volcano (Catalan Volcanic Zone), which contains a large number of red sandstone clasts. It is concluded that the studied deposit cannot be considered as a lahar or as a pyroclastic surge deposit, considering both the emplacement temperature and the morphological features.Presented at 3rd Biennial Meeting on New Trends in Geomagnetism, Smolenice Castle, West Slovakia, June 22–29, 1992 相似文献
16.
S.L. Donoghue J.A. Gamble A.S. Palmer R.B. Stewart 《Journal of Volcanology and Geothermal Research》1995,68(1-3)
We describe a magma mingling episode from Ruapehu volcano between two andesite magmas, one very much minor in volume relative to the other. The event acted to trigger eruption of the andesitic Pourahu pyroclastic flow which is preserved in a thick sequence of tephras and laharic deposits in the southeastern ring plain of the volcano. The predominant andesite is pale brown coloured and porphyritic containing phenocrysts of plagioclase-clinopyroxene-orthopyroxene-Fe-Ti oxides. Rare clasts of a darker andesite are different texturally, less vesicular, and contain distinctive microphenocrysts of plagioclase and quench olivine. Equally rare clasts, of streaky pumice consisting of interbanded ‘dark’ and ‘light’ andesite attest to mingling between these two andesite components.Chemical analyses of discrete clasts demonstrate that the Pourahu pyroclastic flow andesites span much of the compositional spectrum of Ruapehu andesites. This observation demonstrates heterogeneity in the products of a relatively small eruption. The darker clast analyses and those from associated distal fall deposits lie within the fields defined by the dominant light coloured clasts. Phenocryst and microphenocryst geothermometry suggest slightly higher temperatures in the dark component. However, glasses from groundmass and phenocryst inclusions in the same specimen may differ considerably, leading us to conclude that many phenocrysts are in fact xenocrystic and were incorporated in the melts as they migrated towards the surface.We prefer a model in which a small volume of hot andesite magma injects a vent-feeding magma chamber, triggering vesiculation and eruption. We infer that the process of magma withdrawal extended downward into the magma body causing the dark component to intermingle with the lighter (dominant) component, ‘sucking’ more dark magma into the chamber. Our observations are entirely consistent with the existence of a plexus of small, possibly interlinked magma chambers beneath Ruapehu. 相似文献
17.
Late Cretaceous uplift history of the Cretaceous volcanic arc in Southwest Japan: Provenance analysis of the Yuasa–Aridagawa basin based on U–Pb zircon ages 
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下载免费PDF全文 The Ryoke Metamorphic complex has undergone low‐P/T metamorphism and was intruded by granitic magmas around 100 Ma. Subsequently, the belt was uplifted and exposed by the time deposition of the Izumi Group began. The tectonic history of uplift, such as the timing and processes, are poorly known despite being important for understanding the spatiotemporal evolution of the Ryoke Metamorphic Belt. U–Pb zircon ages from sedimentary rocks in the forearc and backarc basins are useful for constraining uplift and magmatism in the provenance. U–Pb dating of detrital zircons from 12 samples (four sandstones and eight granitic clasts) in the Yuasa–Aridagawa basin, a Cretaceous forearc basin in the Chichibu Belt of Southwest Japan, gave mostly ages of 60–110 Ma. Granitic clasts contained in conglomerate suggest that granitic intrusions predate the formation of Coniacian and Maastrichtian conglomerate. Emplacement ages of granitic bodies originated from granitic clasts in Coniacian conglomerate are (110.2 ±1.3) Ma, (106.1 ±1.8) Ma, (101.8+5.8–3.8) Ma, and (95.3 ±1.4) Ma; for granitic clasts in Maastrichtian conglomerate, (89.6 ±1.8) Ma, (87.3+2.4–1.8) Ma, (85.7 ±1.2) Ma, and (82.7 ±1.2) Ma. The results suggest that detrital zircons in the sandstones were mainly derived from volcanic eruptions contemporaneous with depositional age, and plutonic rocks of the Ryoke Metamorphic Belt. Zircon ages of the granitic clast samples also indicate that uplift in the provenance began after Albian and occurred at least during the Coniacian to Maastrichtian. Our results, together with the difference of provenance between backarc and forearc basins suggest that the southern marginal zone of the Ryoke Metamorphic Belt was uplifted and supplied a large amount of clastic materials to the forearc basins during the Late Cretaceous. 相似文献
18.
Repeated samples from the top 5cm of sediment in a homogeneous network of 100 sampling stations in the Barth bodden (mean depth—1.8 m) are analysed for dry weight, organic matter (loss on ignition), grain size distribution, total phosphorus and iron which is soluble in hydrochloric acid. The distribution of mineral and mud sediments (organic matter > 5%) follows the bottom topography: trays, closed basins and channels show the respective muddy concentrations; spits, ground waves and windexposed uplifts from depressions are mostly mineralic. The water depth has only a subordinate effect on distribution. After unquiet meteorological and hydrographic situations mainly the fine-grained material is redistributed. As comparative investigations over four years show, due to this the distribution pattern is not changed fundamentally, so that the distribution of mainly mineralic, muddy and intermediate transition ranges can be mapped, unless this would be done according to surveys under extreme hydrographic and meteorological conditions. The individual parameters of the sediment quality show significant correlations between each other. 相似文献