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本文以湖南花垣民乐锰矿床为例,研究了矿床中火山碎屑物质的分布及特征,用硫同位素氧、碳同位素等成因地球化学特征阐明该区裂陷盆槽盆或地堑盆地中海底火山喷发对锰矿形成的重要意义,并提出了成矿模式,认为湘西北锰矿床属离火山喷发中心较远的海底火山喷发-沉积锰矿床。 相似文献
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火山岩油气藏的研究一般以陆上喷发沉积的火山岩体为主,事实上全世界四分之三的火山活动是在水下发生的,只是水下喷发沉积的火山岩在各个方面的研究还比较少,在勘探中尚未引起注意。本文以三塘湖盆地石炭系火山岩油藏为例,对比分析了陆上与水下喷发沉积形成的火山岩在岩性、颜色、结构构造以及储集空间特征和地震反射特征等方面的差异,指出了三塘湖盆地石炭系哈尔加乌组火山岩为水下喷发环境形成。通过对研究区两种类型的火山岩油藏系统的研究,总结出了水下喷发沉积的火山岩储层的形成机理以及其形成规模油气藏的条件,为今后的火山岩油气藏的勘探指出了新的方向。 相似文献
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水下火山喷发作用机制不同于陆地环境喷发,随着水参与程度的变化,喷发机制趋向复杂。本文以雷琼火山群的湛江硇洲岛作为研究对象,聚焦浅海火山产物的判断依据和水下火山喷发机制。硇洲岛是我国最大的第四纪火山岛,其上的那晏湾剖面保留了完整的火山喷发堆积序列。在那晏湾剖面的凝灰岩中,主要有三类火山成因的大粒径原生碎屑(2-5mm):塑变熔岩碎屑、碎玄玻璃及玄武玻璃,推断为不同程度水-岩浆相互作用的产物,根据水的参与程度大致排序为:碎玄玻璃>玄武玻璃>塑变熔岩碎屑。通过对硇洲岛水-火山作用机制研究,发现水-岩浆混合质量比(Mwater/Mmelt)是控制爆炸强度和火山碎屑粒度的关键因素。火山喷发序列分析表明,硇洲岛的喷发过程总体可分为三期,早期是冰岛苏特塞式喷发的浅水环境蒸汽爆炸与“火喷泉”喷发;中期过渡转为“火喷泉”喷发,伴随陆上的射汽岩浆喷发;最终以岩浆溢流式喷发结束。 相似文献
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金星薄饼状火山(陡边火山)是一类形貌非常独特的火山,有别于太阳系中其他的火山:近圆的底面轮廓、平坦的顶部和较大的顶底直径比.薄饼状火山被认为是高黏度岩浆喷发形成的,但是这一成因并不被广泛接受.火山的形貌特征主要取决于岩浆成分、喷发机制、重力和喷发环境(如大气压)等.因此,通过对比地球火山的形貌特征及形成机制可以为金星薄饼状火山的成因提供指示.我们利用底面不规则度(ii )、高径比(H/W B )、顶底直径比(W S/W B )、侧边最大坡度处的标准化高度(HS m a x )、顶部高径比(H S/W S )和喷发量(V )这些形貌参数定量地将地球表面的复式火山、盾形火山、火山锥、熔岩穹丘(Peleean 型和 Coulees 型)、海底平顶火山以及泥火山的形貌特征与金星薄饼状火山对比.Coulees型熔岩穹丘、海底平顶火山和泥火山的形貌特征与金星薄饼状火山有一定的相似性.Coulees型熔岩穹丘剖面形态与薄饼状火山最为相似,可能指示了薄饼状火山具有类似的成因机制,而海底平顶火山侧边的上凹特征可能指示了其与薄饼状火山完全不同的成因机制.因此,薄饼状火山可能是相对高黏度的岩浆以较高速率持续性喷发形成. 相似文献
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For the first time data on the composition of melt inclusions in plagioclases were obtained. The mineral composition of tuffites in the area of Balaklava and the types of primary-igneous zoning of plagioclases are examined in detail. The eruptions were located at the active continental margin; material transport during the eruption and accumulation took place under submarine coastal conditions. The eruption center was located no more than a few tens of kilometers south of the present-day shoreline. The volcanic activity of the Lower Cretaceous paleovolcanic center in southwestern Crimea was reconstructed. 相似文献
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P. Nomikou S. Carey K. L. C. Bell D. Papanikolaou K. Bejelou K. Cantner D. Sakellariou I. Perros 《Natural Hazards》2014,72(3):1375-1390
Kolumbo submarine volcano, located NE of Santorini caldera in the Aegean Sea, has only had one recorded eruption during historic times (1650 AD). Tsunamis from this event severely impacted the east coast of Santorini with extensive flooding and loss of buildings. Recent seismic studies in the area indicate a highly active region beneath Kolumbo suggesting the potential for future eruptive activity. Multibeam mapping and remotely operated vehicle explorations of Kolumbo have led to new insights into the eruptive processes of the 1650 AD eruption and improved assessments of the mechanisms by which tsunamis were generated and how they may be produced in future events. Principal mechanisms for tsunami generation at Kolumbo include shallow submarine explosions, entrance of pyroclastic flows into the sea, collapse of rapidly accumulated pyroclastic material, and intense eruption-related seismicity that may trigger submarine slope collapse. Compared with Santorini, the magnitude of explosive eruptions from Kolumbo is likely to be much smaller but the proximity of the volcano to the eastern coast of Santorini presents significant risks even for lower magnitude events. 相似文献
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《International Geology Review》2012,54(12):1429-1445
ABSTRACTA multi-disciplinary study of the KR1 segment of the Australian–Antarctic Ridge has been conducted since 2011. We present geochemical and age dating results for samples dredged from three sites on the KR1 seamount trail. The majority of the samples are alkaline ocean island basalts with subdominant enriched tholeiites. The samples from the DG05 bathymetric depression include ice-rafted erratics from Antarctica, which consist of gabbro, diabase, various granitoids, volcanic rocks such as trachyte and rhyolite and deformed or undeformed sedimentary rocks. The main provenance of glacial erratics is considered to be the Ross Sea region. However, Carboniferous to Cretaceous ages of erratics indicate that some of these may originate from the western regions of West Antarctica. Based on the size and topography of the volcanic features and geochemical characteristics of the alkaline ocean island basalts (La/SmN = 2.62–3.88; Tb/YbN = 1.54–2.67) and the enriched tholeiites, the KR1 seamount trail is interpreted to be a submarine hotspot chain that is the product of alkaline volcanic eruption and seafloor spreading. 相似文献
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Eric A. K. Middlemost 《Contributions to Mineralogy and Petrology》1972,36(1):33-48
La Palma is the northwestern island in the Canary archipelago. The island is volcanically active and in recent years there have been two eruptions (1949 and 1971). The oldest rocks that crop out on the island are altered spilitic lavas and they are intruded by numerous dykes and a number of mafic and ultramafic plutonic rocks. These rocks form part of the floor of the huge Caldera de Taburiente. In the walls of the Caldera one finds a 1000 metres thick unit that is composed of lavas and tephra. The rocks are called the El Time formation; and they together with the rocks of the Cumbre Vieja ridge are mainly composed of accumulative mafic rocks, basanites, hawaiites, benmoreites and phonolitic trachytes. These sodarich alkalic rocks are considered to have evolved by fractional crystallization of a basanitic magma in a near surface environment.It is proposed that La Palma developed on a relatively cold section of a plate of oceanic lithosphere that was over 100 m.y. old. During the Alpine-Atlas orogeny this section of the African plate was disrupted and a basanitic magma was extruded onto the sea floor. The volcanic focus of this eruption became established as a local centre for the degassing of the mantle and as a result this area has experienced a long series of eruptions.During the first phase in the evolution of La Palma the submarine edifice of the island was constructed and the rocks of the Caldera Floor formation were emplaced. After a period of marine erosion the huge old volcano Taburiente developed in the northern half of the island. During the final phase in the evolution of the island the southern section of the volcanic edifice subsided and formed the El Paso tectonic basin and the volcanic rift zone along which the many smaller volcanoes of the Cumbre Vieja ridge have developed. 相似文献
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《International Geology Review》2012,54(10):1295-1313
The environment where the Permian Emeishan large igneous province (LIP) of Southwest China erupted remains controversial, especially regarding whether it was terrestrial, involving a 1 km scale domal uplift, or submarine. Slightly younger Daqiao conglomerate and Binchuan pillow lavas suggest that the Emeishan LIP erupted in a submarine environment. We show that at Binchuan, sandstone and rhyolite lie beneath the pillow lavas. In the Daqiao cross-section, there is an eastwards-verging syncline that reverses the succession of basalt and conglomerate. The conglomerate is not a basal conglomerate, and it does not contain any magmatic hydrovolcanic deposits. The basalt underlying the conglomerate is not the first of the LIP eruptions; that first eruption is found ~420 m below, on top of the Permian Maokou limestone. All together, these observations show that the deposits, including the conglomerate and pillow lava, do not represent the environment at the very start of the LIP volcanic eruptions, but represent conditions that existed before and possibly during the Emeishan LIP eruptions. Based on field investigations, the petrology of the rocks, and structural features, we conclude that submarine sedimentation and subaerial basalt eruptions coexisted in time and space in the region during or prior to the Emeishan LIP basalt eruptions. 相似文献
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依据青海索拉沟铜多金属矿床地质地球化学特征,特别是矿床物质来源、矿物、元素分带、成矿热液演化中铜多金属矿床的性状,对该矿床的地质特征、矿床成因及控矿条件进行了研究。研究表明,该索拉沟铜多金属矿床属火山沉积—热液改造型矿床,其矿床经历了沉积成岩和热液改造两个阶段。中三叠世海底火山喷发喷气活动携带大量成矿物质,在浅海台地相对低洼的部位（还原条件下）与火山碎屑物、陆源物一起沉积下来,形成了最初的＂矿源层＂或贫矿层,在随后的（印支期）造山过程中,受强烈构造-岩浆活动的作用,地层中岩石脱水、成矿元素活化、聚集形成富矿溶液,并沿地层层理、岩石破裂运移,交代岩石中化学性活泼的组分或充填于岩石裂隙中富集成矿。 相似文献
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关于热水沉积物稀土配分模式的讨论 总被引：5，自引：0，他引：5
海底热水沉积物的稀土配分模式取决于流体的密度和流方式,低密度热流体的沉积物稀配合模式类似于海水模式,高密度热流体的沉积物没有固定的稀土配分模式,在判别热水沉积物时不宜单独使用稀土配分模式。 相似文献
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J.C. Carracedo B. Singer B. Jicha F.J. Pérez Torrado H. Guillou E.R. Badiola R. Paris 《Geology Today》2010,26(3):101-104
Errors in the interpretation of clouds, fumarolic activity and forest fires as volcanic eruptions in Tenerife, mainly in relation with Teide volcano, are common in references by passing navigators and other eyewitness accounts from the fifteenth and sixteenth centuries. In the case of the most common, historical, multiple‐vent fissure eruptions in the Canaries, vent locations provided by these accounts are frequently uncertain or are clearly erroneous and often conflict with geological evidence. Significant examples are the general association of the latest eruption of Teide volcano, dated at 1150 ± 140 bp , with the reference made by Christopher Columbus in 1492 to an eruption ‘on the flanks of Teide’, which actually corresponds to an eruptive vent (Boca Cangrejo volcano) situated in the NW Rift, dated at 400 ± 110 bp . Similar conflicting vent locations occurred in the 1730–36 eruption of Lanzarote and the 1677 eruption of La Palma. This article considers the volcanic cones located in the Orotava Valley, erroneously assigned by Chevalier de Borda and Alexander von Humboldt to a 1430 ad eruption. Geological evidence and radiocarbon dating of charcoal underlying the lapilli, and 40Ar/39Ar dating of one of the lava flows, show that these volcanic cones and lavas correspond to an eruption that took place about 30 000 yr bp . Analysis of the influence of these erroneous ages for the recent volcanism of Tenerife shows an overestimation of eruptive hazards of this island. 相似文献
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《International Geology Review》2012,54(1):112-130
AbstractFluid dynamical and numerical modelling predicts a large-scale regional domal uplift prior to basalt eruptions in large igneous provinces, which can be readily measured when a plume head rises below a shallow marine sedimentary basin. Research on the sedimentology, biostratigraphy, and isotopic chronology of the Emeishan large igneous province demonstrates that the sedimentary environment in the Maokou stage is not uniform carbonate platform facies, but rather sedimentary facies with a north–south linear alignment and west–east different distribution controlled by the syn-depositional normal faulting of the Changhai and Xiaojiang faults, which are the result of underwater dynamic uplift induced by deep mantle activity. The dynamic uplift started in the Maokou stage. Thus, thinning of the Maokou limestone was the product of the difference in the initial depositional thickness caused by the underwater uplift and post-depositional surface uplift and erosion, but post-depositional uplift was much less than kilometre scale. Sedimentary facies differentiation and tectonic–sedimentary evolution in the Maokou stage provide a constraint for the time of the initial eruption and eruption environment before and during the Emeishan basalt eruption. Small-scale magmatic activity might have already begun in the middle of the Maokou stage, whereas submarine and terrestrial sedimentary environments coexisted before and during Emeishan basalt eruption. 相似文献
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The 12 to 13 July 2003 andesite lava dome collapse at the Soufrière Hills volcano, Montserrat, provides the first opportunity to document comprehensively both the sub‐aerial and submarine sequence of events for an eruption. Numerous pyroclastic flows entered the ocean during the collapse, depositing approximately 90% of the total material into the submarine environment. During peak collapse conditions, as the main flow penetrated the air–ocean interface, phreatic explosions were observed and a surge cloud decoupled from the main flow body to travel 2 to 3 km over the ocean surface before settling. The bulk of the flow was submerged and rapidly mixed with sea water forming a water‐saturated mass flow. Efficient sorting and physical differentiation occurred within the flow before initial deposition at 500 m water depth. The coarsest components (～60% of the total volume) were deposited proximally from a dense granular flow, while the finer components (～40%) were efficiently elutriated into the overlying part of the flow, which evolved into a far‐reaching turbidity current. 相似文献
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DIMITRIOS OIKONOMIDIS KONSTANTINOS ALBANAKIS SPYRIDON PAVLIDES MICHAEL FYTIKAS 《Journal of Earth System Science》2016,125(1):1-11
A catastrophic volcanic explosion took place in Thera/Santorini island around 1613 BC, known as the ‘Minoan’ eruption. Many papers have dealt with the shape of the shoreline of the island before the eruption, but none with the shape of the shoreline exactly after it, assuming that it would be the same with the contemporary one. However, this is not correct due to the wave erosion. In this paper, a new DEM was constructed, covering both land and submarine morphology, then topographic sections were drawn around the island. Using these sections, the ‘missing parts’ (sea-wave erosion) were calculated, the shoreline was reconstructed as it was one day after the eruption and finally the erosion rate was calculated. 相似文献
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The 1971 Teneguía eruption is the most recent volcanic event of the Cumbre Vieja rift zone on La Palma. The eruption produced basanite lavas that host xenoliths, which we investigate to provide insight into the processes of differentiation, assimilation and magma storage beneath La Palma. We compare our results to the older volcano magmatic systems of the island with the aim to reconstruct the temporal development of the magma plumbing system beneath La Palma. The 1971 lavas are clinopyroxene-olivine-phyric basanites that contain augite, sodic-augite and aluminium augite. Kaersutite cumulate xenoliths host olivine, clinopyroxene including sodic-diopside, and calcic-amphibole, whereas an analysed leucogabbro xenolith hosts plagioclase, sodic-augite-diopside, calcic-amphibole and hauyne. Mineral thermobarometry and mineral-melt thermobarometry indicate that clinopyroxene and plagioclase in the 1971 Teneguía lavas crystallised at 20–45 km depth, coinciding with clinopyroxene and calcic-amphibole crystallisation in the kaersutite cumulate xenoliths at 25–45 km and clinopyroxene, calcic-amphibole and plagioclase crystallisation in the leucogabbro xenolith at 30–50 km. Combined mineral chemistry and thermobarometry suggest that the magmas had already crystallised, differentiated and formed multiple crystal populations in the oceanic lithospheric mantle. Notably, the magmas that supplied the 1949 and 1971 events appear to have crystallised deeper than the earlier Cumbre Vieja magmas, which suggests progressive underplating beneath the Cumbre Vieja rift zone. In addition, the lavas and xenoliths of the 1971 event crystallised at a common depth, indicating a reused plumbing system and progressive recycling of Ocean Island plutonic complexes during subsequent magmatic activity. 相似文献