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1.
腾冲地区新生代火山活动分期 总被引：26，自引：7，他引：19
在前人对腾冲火山活动分期基础上,通过实地考察。依据地层披盖关系,地丑对比、火山财貌、岩石类群、岩性等特点并参考同位素年龄测定值,把腾冲新生代火山活动分为四个活动期、九个亚期。第一期火山活动活动始于上新世,第二期火山活动为早更新世,第三期火山活动为晚更新世。第上期火山活动为全新世。 相似文献
2.
本文利用布设在云南腾冲地区的15个固定和流动地震台站记录的近震波形数据,采用剪切波分裂分析方法得到了593对高质量的各向异性分裂参数.结果显示,腾冲火山区地震台站下方的近震各向异性的慢波延迟时间为0.02~0.37 s,平均延迟时间0.2 s.结合已有接收函数地壳各向异性研究结果,推测研究区地壳各向异性的主要贡献源自中上地壳.研究区不同台站的快波偏振方向变化很大,似乎反映了构造和区域应力场的共同作用.其中腾冲火山断裂西侧多数台站的快波偏振方向呈近N-S向,而东部多数台站的快速偏振方向呈NE-SW向,与区域主压应力方向一致,暗示研究区中上地壳各向异性主要是受主压应力引起定向排列的裂隙所致.基于近震走时得到的研究区平均VP/VS为1.68,推测腾冲火山区地壳应力场的局部变化可能与上地壳中富含气体的中酸性岩浆膨胀活动有关.另一方面,在腾冲火山区外围个别台站(MIZ、MZT)观测到了快波偏振方向与主压应力、已知断层等构造走向不一致的现象,暗示其各向异性是构造或构造和区域应力场共同作用的结果. 相似文献
3.
Field investigation and lab analysis on samples were carried out for Quaternary volcanoes, including Xiaoshan volcano, Dashan volcano and Bianzhuang hidden volcano, in Haixing area, east of North China. Results show that Xiaoshan volcano with the eruptive material of volcanic scoria, crystal fragments and volcanic ash is a maar volcano, the eruptive pattern is pheatomagmatic eruption, and the influence scope is near the crater. Dashan volcano exploded in the early stage, and then the magma intruded, forming the volcanic neck. The eruption strength and scale are limited, and the eruptive materials are scoria, volcanic agglomerate and dense lava neck. The volcanic rocks in Bianzhuang are porosity and dense volcanic rocks and volcanic breccia, reflecting the pattern of weak explosive eruption and lava flow, and the K-Ar age dating on volcanic rocks indicates that the eruption happened in early Pleistocene. Xiaoshan volcanic scoria and Bianzhuang hidden volcanic rocks are mainly basaltic, Dashan volcanic rocks with lower SiO2 content are nephelinite in composition. Their oxide contents have no linear relationship, indicating that there is no magma evolution relationship between these magmas from the three places. Three volcanic rocks all have enrichment of light rare earth. The Bianzhuang volcanic rocks are rich in large ion lithophile elements, and have no high field strength elements Zr and Hf, Ti losses. The volcanic materials from Xiaoshan and Dashan are intensively rich in Th, U, Nb and Ta, and significantly poor in K and Ti. Although the magmas from these three places in Haixing area may all come from asthenosphere, the volcanic materials have different petrological and geochemical features, and relatively independent volcanic structures, therefore, they experienced different magma processes. 相似文献
4.
The Senyama volcanic products of the late Pliocene to early Pleistocene O’e Takayama volcano overlie a 100-m-thick, late Pliocene
coastal quartz-sandstone and are intruded by an early Pleistocene dacite dome. The Senyama volcanic products are the remains
of a cone that retains a basal part 1.5 km across and 150–250 m high from the substrate. The cone comprises dacite block-and-ash
flow deposits and minor base-surge deposits occur at the base. Single beds of the block-and-ash flow deposits are 1–16 m thick
and dip inward 20–40° at the base of the cone and inward or outward 10–20° at the summit. Juvenile fragments in the block-and-ash
flow deposits are non- to poorly vesicular and commonly have curviplanar surfaces and prismatic joints extending inward from
the surfaces, which imply quenching and brittle fracturing of dacite lava. They are variably hydrothermally altered. Nevertheless,
juvenile blocks appear to retain a uniform direction of the magnetization vector residual during thermal demagnetization between
280°C and 625°C. At the time of the eruption, the well-sorted sand of the substrate was at the coast and a good aquifer that
facilitated explosive interaction of water and the ascending dacite lava. The mechanism of the explosion perhaps involved
thermal contraction cracking of the dacite lava, water-inflow into the interior of the lava, and explosive expansion of the
water. Initial phreatomagmatic explosions opened the vent. Succeeding phreatomagmatic or phreatomagmatic–vulcanian explosions
produced block-and-ash flow deposits around the vent. Hydrothermal silver-ore deposits and manganese-oxide deposits occur
in the Senyama volcanic products and the underlying sandstone, respectively. They could represent post-eruptive activity of
the hydrothermal system developed in and around the cone. 相似文献
5.
云南腾冲马鞍山最后一次喷发的热释光年龄 总被引：4，自引：0，他引：4
云南腾冲火山区是我国少数几个近代有火山活动的地区之一,它由多座第四纪火山组成。其中马鞍山是规模较大,可能喷发较晚的一处火山。从马鞍山火山锥附近采集了２个火山岩样品,进行了热释光测年分析。热释光年龄表明马鞍山最后一次大规模的火山喷发发生在全新世,可能距今约２５００～３５００年。 相似文献
6.
More than 40 late Cenozoic monogenetic volcanoes formed a volcanic belt striking NNW from Keluo, through Wudalianchi to Erkeshan in NE China. These volcanoes belong to a unified volcano system, namely Wudalianchi volcanic belt(WVB for short). Based on the volcanic evolution history and the nature of monogenetic volcanic system, we estimate that the volcanic system of WVB is still active and has the potential to erupt again. Hence, this paper studied the temporal-spatial distribution and volcanic eruption types to evaluate the possible eruption hazard types and areas of influence in the future.
Volcanic field characteristics and K-Ar radiometric data suggest two episodes of volcanism in the WVB, the Pliocene to early Pleistocene volcanism(4.59~1.00MaBP)and the middle Pleistocene to Holocene volcanism(0.79Ma to now). The early episode volcanoes are distributed only in the north of WVB(mainly in Keluo volcanic field), featured by effusive eruption, and mainly formed monogenetic shield, whose base diameter is large and slope is gentle. However, the late episode eruptions occurred over the entire WVB. The explosive eruption in this stage formed numerous relatively intact scoria cones of explosive origin. Meanwhile the effusive eruption formed widely distributed lava flows.
Both effusive eruption and explosive eruption are common in WVB. The effusive eruption formed monogenetic shields and lava flows. The resulting pahoehoe lava, aa lava and block lava appeared in WVB. There are three end-member types of explosive eruption driven by magmatic volatile. Violent Strombolian eruption has the highest degree of fragmentation and mass flux, characterized by eruption column. Strombolian eruption has the high degree of fragmentation, but low mass flux, featured by pulse eruption. Hawaiian eruption has low degree of fragmentation, but high in mass flux, generating large scoria cones. In addition, this paper for the first time found phreatomagmatic eruption in WVB, which formed tuff cone. Transitional eruptions are also common in WVB, which have certain characteristics among the end-member eruption types. Besides, certain volcanoes displayed multiple explosive eruption types during the whole eruption span.
According to the volcanic temporal-spatial distribution and eruption characteristics in WVB, the potential volcanic hazards in future are constrained. It appears that the violent Strombolian and Strombolian eruption will not have significant impact on aviation safety in the vertical direction. In the radial direction, the ejected volcanic bomb can reach as far as 1km from the vents and the fallout tephra may disperse downwind over a distance ranging from 1~10km. The major hazard of Hawaiian eruption and effusive eruption comes from lava flow, and its migration distance may reach 3.0~13.5km for pahoehoe lava and 2.9~14.9km for aa lava. The base surge in phreatomagmatic eruption can reach a velocity of 200~400m/s, and the migration distance is around 10km. This is a big threat that people should pay more attention to and take precautions in advance. Besides, it is necessary to strengthen the real-time observation of the volcanoes in the WVB, especially those formed in the late episode as well as near the active fault. 相似文献
7.
腾冲新生代火山分布特征 总被引：32，自引：11，他引：21
通过实地考察和资料对比,综合前人研究成果。最终得出腾冲地区新生代火山有６８座,并给出各个火山主要分布特征。同时根据火山喷发类型、岩性、时代、地域等相关性,腾冲火山区新生代火山划分为７个火山群;１．鸦乌山－－大黑山火山群;２．大团山－－黑龙湾火山群;３．马站火山群;４．打鹰山－－马鞍山火山群;５．余家大山－大六冲火山群;６来凤山－三益村火山群;．７大呼山－－照壁山火山群。腾冲新生代火山分布肯有数量多 相似文献
8.
科洛火山群的新生代火山共有23座,坐落于科洛河两岸,火山岩面积约为350km2,岩性主要为碱性玄武岩.由于地处NE向断陷盆地这一特殊的构造位置,科洛地区的火山活动及展布主要受到区域基底断裂的制约.火山喷发形式总体为中心式,属斯通博利式火山.火山活动可划分为上新世、更新世和全新世3期.上新世在断陷盆地边缘形成了一系列NE向线性展布的中心式溢出型火山,其中部分火山因风化剥蚀而失去了原有的火山地貌特征,仅保留盾形熔岩台地.早更新世火山活动相对平静.中-晚更新世火山活动仍受到NE向基底断裂的控制,但喷发中心、喷发方式及喷发强度均发生改变,火山由碱玄质火山渣锥和熔岩流组成.进入全新世以后南山喷发,其火山结构保存完好,裸露的熔岩台地保留了较好的微地貌特征.该期火山亦由碱玄质火山渣锥和熔岩流构成.在科洛火山群的火山活动过程中,其熔岩流覆盖了早期沉积地层,并对盆地中的河流进行了改造,最终导致该区断陷盆地初始地貌的改变. 相似文献
9.
THE CHARACTERISTICS OF VOLCANIC ROCKS STRUCTURE AND LITHOFACIES OF DALIUCHONG VOLCANO IN THE TENGCHONG VOLCANIC FIELD,YUNNAN PROVINCE 
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下载免费PDF全文 A set of grey-purple layered volcanic rocks are found widely distributed from the mountain flank to the main peak of Daliuchong volcano, but it's difficult to identify whether they are volcaniclastic rock or lava rock just by field investigation and the crystal structure observation under microscope. The study of matrix microstructure of the volcanic rocks can help to identify the volcanic facies. We recognize the eruptive facies rocks through observation of the matrix microstructure and pore shape with comparison to those of the volcanic vent facies, extrusive facies and effusive facies rocks under microscope, thus the mentioned layered volcanic rocks could be named as dacitic crystal fragment tuff. Combining the joint work of field investigation, systematic sampling, chemical analyzing and microscopic observation, we summary the Daliuchong volcanic facies as follows:1. The effusive facies lava constitutes the base of Daliuchong volcano and was produced by early eruption.2. The explosive facies is composed of dacite crystal fragment welded tuff and volcanic breccia and mainly distributes on the W, S and NE flank of the volcanic cone.3. The volcanic conduit with its diameter more than one hundred meters is located about 100 meters south of the main peak of the Daliuchong volcano.4. The extrusive facies rock is only exposed near the peak of Daliuchong volcano.Therefore, the volcanism of Daliuchong volcano can be speculated as:Large-scale lava overflowing occurred in the early eruption period; then explosive eruptions happened; at last, the volcanisms ceased marked with magma extrusion as lava dome and plug. 相似文献
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Reconstruction of Quaternary environments, late Cenozoic geodynamics and evaluation of volcanic hazards, all depend on the precise delineation of eruptive stages. In recent years, laser ~(40)Ar/~(39)Ar dating methods have been widely used for dating young volcanic rocks, given their stable automated testing process, very low background level and high sensitivity, which meet the requirements for precise dating of young samples. This paper applied high-precision laser ~(40)Ar/~(39)Ar dating to the main volcanic units in the Tengchong area and obtained ages in the range of 0.025–5.1 Ma using conventional data processing methods. However, conventional dating highlighted issues related to very low radiogenic ~(40)Ar content, accidental errors and poor data stability, which led to huge age deviations. Moreover, lacking a unified timescale, conventional methods were unable to strictly define the stages of the Tengchong volcanic eruptions, leading to ongoing controversy. In this study, we applied a Gaussian mathematical model to deal with all 378 original ages from 13 samples. An apparent age-probability diagram,consisting of three independent waveforms, have been obtained. The corresponding isochron ages of these three waveforms suggest there were three volcanic eruptive stages, namely during the Pliocene(3.78±0.04 Ma), early Middle Pleistocene(0.63±0.03 Ma) and late Middle Pleistocene to early Late Pleistocene(0.139±0.005 Ma). These results accurately define eruptive stages in the Tengchong area. 相似文献
13.
For first time, during 1991, seismic activity was recorded during an eruption at Colima volcano. We analyze these data to
obtain a stress pattern using a composite focal mechanism technique. From the analysis of regional seismicity, the Tamazula
Fault and the Armeria River appear as active features and the dip of the slab east of the Jalisco Block is approximately 12°.
Southwest of Colima volcano a vertical alignment of seismic events was observed. We estimate five different composite focal
mechanism solutions from our data set, which indicate a change of the stress field at the volcano after the 1991 eruption.
These solutions suggest that the stress field in the volcanic edifice was controlled by stresses related to the emplacement
of magma superimposed on the regional stress field. No evidence of active local faults in the volcanic edifice was found.
We propose a model for the eruptive process that involves tilting of the volcanic edifice.
Received: 15 October 1995 / Accepted: 26 October 1998 相似文献
14.
滇西地区壳幔解耦与腾冲火山区岩浆活动的深部构造研究 总被引：4，自引：0，他引：4
根据青藏东部边缘的深部地球物理资料,分析了滇西地区壳幔耦合和腾冲火山区岩浆活动的深部构造特征,确认了地幔各向异性与上地幔速度结构(包括P波速度和S波速度)的内在联系,指出产生这一结果的原因与以腾冲火山区为中心的地幔热物质上涌有关:上地幔顶部平均温度升高导致介质强度降低,在印支块体的侧向挤压或印缅块体的向东俯冲作用下发生韧性变形,造成滇西地区地幔各向异性的快波方向与青藏东部地壳块体的旋转方向不一致.此外,鉴于中下地壳低速层的横向非均匀性,估计韧性流动并非贯通青藏高原的东部边缘,而是被不同的构造块体和边界断裂限定在局部地区.总体而言,滇西地区下地壳的地震波速度和电阻率偏低,具备发生韧性变形的构造条件.作为地壳和上地幔之间的解耦层,它使得青藏东部地壳块体旋转产生的构造应力未能传输至上地幔.腾冲火山区的地壳结构与不同时期的岩浆活动有关,火山区东侧的高速结构代表了上新世时期火山通道内冷凝固结的岩浆侵入体或难以挥发的高密度残留物质,火山区西侧的低速结构反映了更新世以来持续至今的岩浆活动,壳内岩浆源主要分布在10～20km的深度范围内,横向尺度约为15～20km,有可能通过地壳深部的断裂与上地幔岩浆源区相连,估计腾冲火山区下方的岩浆活动将持续进行. 相似文献
15.
腾冲火山区及周围地区震源机制与构造应力场分布特征 总被引：2，自引：0，他引：2
对腾冲火山区及周围地区强震震源深度和震源机制空间分布及区域现代构造应力场特征进行了研究。由我国西南地区直到缅甸中深源地震带的区域构造应力场空间分布格局,充分显示出我国西南地区在现代构造运动过程中,受到以印度板块对亚欧板块碰撞挤压作用为主要动力源,在东部同时受到太平洋板块和菲律宾海板块远距离作用影响的总体特征。腾冲火山区主要受到印度板块在缅甸中深源地震带产生的侧面挤压剪切的直接作用。腾冲火山区所属的腾冲龙陵地震带是西南地区区域构造应力场分区的一条重要边界。腾冲火山区主要受到北东———北东东向的区域压应力场作用,同时也可能受到东侧毗邻应力场分区南南东———南东向压应力场的影响。 相似文献
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47个腾冲火山岩样品的K-Ar年龄值域在0.09和17.84Ma之间。4条火山岩的40Ar/36Ar-40K/36Ar等时线年龄分别为2.93、0.81、0.31和0.13Ma。火山喷发的时代从中新世到更新世,喷发的高潮在晚更新世。腾冲火山目前还不是死火山,而腾冲及其邻区的热事件（侵入-热变质-喷发）又是连续发生的。20个样品的Rb和Sr含量、稳定Sr同位素初始比（0.70578-0.71437）以及其它地球化学资料还表明,这些火山岩是属于板块碰撞带生成的高钾钙碱性岩浆系列。火山岩的母岩浆来源于地幔的玄武岩浆,但在上升过程中受到过富含放射性成因Sr的地壳物质的强烈渐进混染。 相似文献
18.
Introduction The Tengchong volcanic-geothermal area is located on the northeast edge of the collision zone between Indian and Eurasian plates, and belongs to Eurasian volcanic zone (the MediterraneanHimalayanSoutheast Asia volcanic zone). In Tengchong area, the Quaternary volcanic, geothermal and seismic activities are all intensive. These phenomena have been drawing the attention of many geoscientists in the world. Their studies are concerned with geology, geophysics, geochemistry, and cr… 相似文献
19.
The volcanic island of Milos, Greece, comprises an Upper Pliocene –Pleistocene, thick (up to 700 m), compositionally and texturally diverse succession of calc-alkaline, volcanic, and sedimentary rocks that record a transition from a relatively shallow but dominantly below-wave-base submarine setting to a subaerial one. The volcanic activity began at 2.66±0.07 Ma and has been more or less continuous since then. Subaerial emergence probably occurred at 1.44±0.08 Ma, in response to a combination of volcanic constructional processes and fault-controlled volcano-tectonic uplift. The architecture of the dominantly felsic-intermediate volcanic succession reflects contrasts in eruption style, proximity to source, depositional environment and emplacement processes. The juxtaposition of submarine and subaerial facies indicates that for part of the volcanic history, below-wave base to above-wave base, and shoaling to subaerial depositional environments coexisted in most areas. The volcanic facies architecture comprises interfingering proximal (near vent), medial and distal facies associations related to five main volcano types: (1) submarine felsic cryptodome-pumice cone volcanoes; (2) submarine dacitic and andesitic lava domes; (3) submarine-to-subaerial scoria cones; (4) submarine-to-subaerial dacitic and andesitic lava domes and (5) subaerial lava-pumice cone volcanoes. The volcanic facies are interbedded with a sedimentary facies association comprising sandstone and/or fossiliferous mudstone mainly derived from erosion of pre-existing volcanic deposits. The main facies associations are interpreted to have conformable, disconformable, and interfingering contacts, and there are no mappable angular unconformities or disconformities within the volcanic succession.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
20.
为了进一步认识青藏高原东南缘的构造演化等动力学问题以及该区域的深部孕震机理，本文使用位于该区域内的中国地震科学台阵探测项目的台站所记录到的远震P波波形数据，采用地震光照成像法获取了岩石圈间断面的结构，并讨论了该方法的准确性和稳定性。研究结果显示，青藏高原东南缘的岩石圈西薄东厚，其中:滇缅泰地块腾冲火山附近最薄，约为60 km，其较薄的岩石圈可能是软流圈地幔物质上涌造成的；扬子地块岩石圈厚度从四川盆地向南逐渐减薄，特别是四川盆地下方最厚，可达190 km左右；滇缅泰地块腾冲火山下方150 km深度左右探测到明显的间断面，该间断面可能是腾冲火山原始岩浆源的位置即岩浆源。本研究所得结果 “印支地块与滇缅泰地块结构的连续性” 进一步为印度板块的推挤作用造成腾冲火山低速物质向东溢出的结论提供了地震学证据。此外，研究区域最北端的剖面显示，峨眉山大火成岩省的内带在50—250 km深度范围及其上方地壳内存在明显的局部高速异常，其不均匀分布特征可能与二叠纪火山喷发过程中岩浆底侵及中新生代以来多期次构造活动有关。 相似文献