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1.
Physical state of the very early Earth 总被引：1，自引：0，他引：1
Yutaka Abe 《Lithos》1993,30(3-4):223-235
The earliest surface environment of the Earth is reconstructed in accordance with the planetary formation theory. Formation of an atmosphere is an inevitable consequence of Earth's formation. The atmosphere near the close of accretion is composed of 200 300 bars of H2 and H2O, and several tens of bars of CO and CO2. Either by the blanketing effect of the proto-atmosphere or heating by large planetesimal impacts a magma ocean is formed during accretion. We can distinguish three stages for the thermal evolution of the magma ocean and proto-crust. Stage 0 is characterized by a super-liquidus (or completely molten) regime near the surface. At this stage the surface of the Earth is covered by a super-liquidus magma ocean. No chemical differentiation is expected during this stage. Once the energy flux released by planet formation decreases to the 200 W/m2 level the super-liquidus magma ocean then disappears within a time interval of 1 m.y. This is the transition from stage 0 to 1. Stage 1 is characterized by a partially molten magma ocean. In the magma ocean consisting of 20 30% partial melt, heat transport is controlled by melt-solid separation (a type of compositional convection) rather than thermal convection. Chemical differentiation of the mantle mainly occurs in this stage. Once the energy flux drops to the 160 W/m2 level, more than 90% of water vapor in the proto-atmosphere condense to form the proto-oceans. Several tens of bars of CO and CO2 remain in the atmosphere just after formation of the oceans. Water oceans are occasionally evaporated by large impacts. After each such event, recondensation of the ocean takes several hundred years. Although the surface is covered by a chilled proto-crust, it is short-lived because of extensive volcanic resurfacing activity as well as meteorite impacts resurfacing. This stage ends when the energy flux drops to 0.1 1 W/m2 level. The duration time of stage 1 is estimated to be several hundred million years (the best estimate is about 400 m.y.). Stage 2 is characterized by solid state convection. This stage continues to the present day. One of the most important change on the proto-Earth is the transition from stage 1 to 2, which occurs several hundred million years after the Earth formation. Long-lived crust is formed only after this transition. 相似文献
2.
月球的化学演化 总被引：2，自引：0，他引：2
月球是一个发生了化学分异的星球,它由月壳、月幔±一个小的金属月核组成。大量观察事实显示月球曾经有过岩浆洋,岩浆洋的结晶分异主导了月球的化学演化。目前主流观点认为,月球是在太阳系演化的早期,至少45亿年前,一个火星大小的星球,与即将完成原始吸积的地球胚胎发生偏心撞击,造成地球的熔融,形成岩浆洋,飞溅出来的物质迅速吸积形成绕地球运动的月球,并且在月球上形成了全球规模的岩浆洋,进而发生了结晶分异。,由于月球上没有海洋和板块俯冲,岩浆洋分异是其化学演化的主要途径。月球岩浆洋的80％～85％在大撞击后的100Ma内已经固化,这可能是由于月球体积小、表面没有大气包裹所致。月球极贫水,因此在岩浆结晶过程中斜长石首先结晶。斜长石由于密度小于玄武质岩浆而漂浮在岩浆洋的表层,橄榄石等密度大的矿物则堆积在岩浆洋的底部。随着结晶分异的进行,残余岩浆不断富集不相容元素,包括K、U等放射性元素;与此同时,密度较大的钛铁矿开始结晶,造成高钛堆晶岩密度大于其下的橄榄石堆晶岩的不稳定结构,进而发生月幔翻转,引发一系列岩浆活动,进而形成月球上特有的镁质系列、碱质系列等岩石。由于月球氧逸度较低,Eu主要以＋2价形式存在,因此斜长石高度富集Eu,相应地除高地斜长岩外,其他岩石均表现为Eu高度亏损的特点。与此同时,Re在低氧逸度下表现为强亲铁元素的特点,Re／Os在月球岩浆过程中不发生分异。月球的体积远小于地球,因而其演化时间远远短于地球,很多原始的分异被完整地保留下来。因此月球的化学演化是类地行星早期演化过程的“化石”,尽管与现代的地球存在较大差异,但是对于认识地球早期演化具有借鉴意义。 相似文献
3.
Cherenkov A. A. Shaikhislamov I. F. Bisikalo D. V. Shematovich V. I. Fossati L. Möstl C. 《Astronomy Reports》2019,63(2):94-106
Results of a study of the influence of solar-type host stars superflares on the gas dynamics of the extended envelopes of giant exoplanets are presented. During flare events, the radiation intensity of the host star in the extreme ultraviolet and soft X-ray can increase by several orders of magnitude for a short time, leading to strong local heating of the exoplanet atmosphere on the side facing the star, with the formation of shocks in the atmosphere. Computations of the gas-dynamical response of the atmosphere of the hot Jupiter HD 209458b to characteristic superflares of solar-like stars were carried out earlier in [1] using a one-dimensional aeronomical model correctly taking into account heating and chemical processes in the atmosphere. To investigate the outflow of atmospheric gas, the results obtained with this onedimensional model were used as simple boundary conditions for computations of the three-dimensional flow structure after a flare. The results of these three-dimensional gas-dynamical computations show that the mass ejection of the flare increases the size of the envelope over several hours, which could be detected with existing observing facilities. It is shown that the mass-loss rates for the most powerful superflare considered could be enhanced by an order of magnitude over several tens of hours after the flare.
相似文献4.
Robert J.Stern 《地学前缘(英文版)》2016,7(4):573-580
As we continue searching for exoplanets,we wonder if life and technological species capable of communicating with us exists on any of them.As geoscientists,we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species.This essay considers this question,focusing on tectonically active rocky(silicate) planets,like Earth,Venus,and Mars.The development of technological species on Earth provides key insights for understanding evolution on exoplanets,including the likely role that plate tectonics may play.An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime,as it cools and its lithosphere thickens,strengthens,and becomes denser.These include magma ocean,various styles of stagnant lid,and perhaps plate tectonics.Abundant liquid water favors both life and plate tectonics.Ocean is required for early evolution of diverse single-celled organisms,then colonies of cells which specialized further to form guts,appendages,and sensory organisms up to the complexity of fish(central nervous system,appendages,eyes).Large expanses of dry land also begin in the ocean,today produced above subduction zones in juvenile arcs and by their coalescence to form continents,although it is not clear that plate tectonics was required to create continental crust on Earth.Dry land of continents is required for further evolution of technological species,where modification of appendages for grasping and manipulating,and improvement of eyes and central nervous system could be perfected.These bioassets allowed intelligent creatures to examine the night sky and wonder,the beginning of abstract thinking,including religion and science.Technology arises from the exigencies of daily living such as tool-making,agriculture,clothing,and weapons,but the pace of innovation accelerates once it is allied with science.Finally,the importance of plate tectonics for developing a technological species is examined via a thought experiment using two otherwise identical planets:one with plate tectonics and the other without.A planet with oceans,continents,and plate tectonics maximizes opportunities for speciation and natural selection,whereas a similar planet without plate tectonics provides fewer such opportunities.Plate tectonics exerts environmental pressures that drive evolution without being capable of extinguishing all life.Plate tectonic processes such as the redistribution of continents,growth of mountain ranges,formation of land bridges,and opening and closing of oceans provide a continuous but moderate environmental pressure that stimulates populations to adapt and evolve.Plate tectonics may not be needed in order for life to begin,but evolution of technological species is favored on planets with oceans,continents,plate tectonics,and intermittently clear night sky. 相似文献
5.
The origin of reaction textures in mantle peridotite xenoliths from Sal Island, Cape Verde: the case for “metasomatism” by the host lava 总被引：1，自引：1，他引：1
Cliff S. J. Shaw Florian Heidelbach Donald B. Dingwell 《Contributions to Mineralogy and Petrology》2006,151(6):681-697
Reaction zones around minerals in mantle xenoliths have been reported from many localities worldwide. Interpretations of the origins of these textures fall into two groups: mantle metasomatic reaction or reaction during transport of the xenoliths to the surface. A suite of harzburgitic mantle xenoliths from Sal, Cape Verde show clear evidence of reaction during transport. The reactions resulted in the formation of olivine–clinopyroxene and Si- and alkali-rich glass reaction zones around orthopyroxene and sieve-textured clinopyroxene and sieve textured spinel, both of which are associated with a Si- and alkali-rich glass similar to that in the orthopyroxene reaction zones. Reaction occurred at pressures less than the mantle equilibration pressure and at temperatures close to the liquidus temperature of the host magma. In addition, there is a clear spatial relation of reaction with the host lava: reaction is most intense near the lava/xenolith contact. The residence time of the xenoliths in the host magma, determined from Fe–Mg interdiffusion profiles in olivine, was approximately 4 years. Our results cannot be reconciled with a recent model for the evolution of the mantle below the Cape Verde Archipelago involving mantle metasomatism by kimberlitic melt. We contend that alkali-rich glasses in the Sal xenoliths are not remnants of a kimberlitic melt, but rather they are the result of reaction between the host lava or a similar magma and xenolith minerals, in particular orthopyroxene. The formation of a Si- and alkali-rich glass by host magma–orthopyroxene reaction appears to be a necessary precursor to formation of sieve textured spinel and clinopyroxene. 相似文献
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7.
At Santa Maria Volcano (New Hebrides island arc), extensive ash and scoria flow deposits overlie the mainly effusive, pre-caldera cone. Hydromagmatic features characterize these deposits, the composition of juvenile clasts ranges from basalt to acid andesite/dacite (SiO2 = 51–63.6%) with a dominant basaltic composition. The stratigraphic position of this pyroclastic series and its spatial distribution around a 8.5 km × 6 km wide caldera provide evidence of a relationship between this series and the caldera formation. In addition, these pyroclastic deposits are co-genetic to parasitic cones and lava flows developed along faults concentric to the caldera. Both series result from a compositionally layered magma reservoir, the subordinate differentiated magmas being the result of fractional crystallization from the basalts. A model of caldera formation which implies a large hydromagmatic eruption at the central vent and minor magma withdrawal by flank eruptions is proposed. This model emphasizes the importance of mafic hydroclastic eruptions in the caldera forming event and contradicts a model implying only quiet subsidence, a process often proposed for the formation of calderas in island are volcanoes of mainly mafic composition. 相似文献
8.
M.L.Renjith 《地学前缘(英文版)》2014,5(1):113-126
A systematic account of micro-textures and a few compositional profles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995,from Barren Island Volcano,NE India ocean,are presented for the frst time.The identifed micro-textures can be grouped into two categories:(i)Growth related textures in the form of coarse/fne-sieve morphology,fne-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fuctuated due to change in temperature or H2O or pressure or composition of the crystallizing melt;and(ii)morphological texture,like glomerocryst,synneusis,swallow-tailed crystal,microlite and broken crystals,formed by the infuence of dynamic behavior of the crystallizing magma(convection,turbulence,degassing,etc.).Each micro-texture has developed in a specifc magmatic environment,accordingly,a frst order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit.Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth.Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective selfmixing environment.Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit.Intermittent degassing and eruption related decompression have also played a major role in the fnal stage of crystallization dynamics. 相似文献
9.
该文在野外地质调查基础上,对备战铁矿区内的火山岩和矿石进行了详细的矿物学和岩石地球化学研究,并深入讨论了矿床成因。研究表明,该区的主要赋矿围岩为火山岛弧玄武岩,其与磁铁矿有着类似的稀土元素配分模式,说明二者有成因上的联系。成矿物质可能来源于北天山洋块向伊犁板块之下俯冲过程中软流圈上涌形成的富铁玄武质岩浆。受洋块俯冲作用影响,富铁玄武质岩浆沿北天山压扭性深大断裂底侵,并经历了一定的结晶分离或同化混染作用,最后在中地壳形成一套演化的玄武质（安山质）岩浆,并在岩浆晚期阶段发生富铁岩浆和硅酸盐岩浆的分离,此时,火山岩中的普通辉石受岩浆晚期的热液作用影响蚀变为透辉石,发生了Si,Ca,Mg的富集和Fe,Al,Ti的缺失,一定程度上促进了含铁矿浆的富集。 相似文献
10.
There is a conspicuous dichotomy in the conventional model oflunar petrogenesis between the total intra-crustal differentiationpostulated for the products of feldspathic volcanism in thelunar highlands and the near absence of differentiation postulatedfor the products of mare volcanism. Both the cumulate mantlemodel, and the selenotherm postulated to accompany genesis ofalleged ‘primary’ mare magmas by remelting of thosecumulates, imply supra-adiabatic thermal gradients in near-solidusmaterials throughout the lunar mantle 4·3–3·2Ga ago. This should have resulted in vigorous convective motion,which has not occurred. There is no positive europium anomalyin the average lunar highland crust. That crust cannot, therefore,have formed by plagioclase flotation from a lunar magma ocean,for which there is no other requirement. There is no negativeeuropium anomaly in the average mantle to be inherited by latermare basalts. Other rocky bodies of lunar size in the SolarSystem have accreted at rates that allowed incorporation ofplenty of volatiles and without forming global magma oceans.Partial melting in the presence of water, followed by near-surfacefractionation and volatile losses can explain the feldspathiccharacter, high incompatible element concentrations and lackof Eu anomaly in the lunar highlands. Volcanic eruption on theMoon must have been accompanied by selective volatilizationlosses of sodium, sulphur and other elements similar to theprocess seen on Io, which can account for the major differencesbetween terrestrial and lunar basalts. Siderophile element depletionin lunar lavas may reflect immiscible sulphide liquid and metalseparation, rather than global impoverishment in such elements,and large ore bodies may have formed close to the lunar surface.Mare basalt volcanism appears to have been a protracted, lowmagma productivity event with few similarities to terrestrialocean-floor, ocean-island, continental flood basalt or komatiitevolcanism. At low pressure the crystallization of plagioclasewell before pyroxene typifies those terrestrial mid-ocean ridgebasalt, ocean-island basalt and continental flood basalt magmas.A similar sequence is demanded of the postulated lunar primarymagmas. Mare basalt hand-specimen and pyroclastic glass beadcompositions do not, however, display the required crystallizationsequence and cannot represent the required primary melt compositions.The true erupted lava compositions which gave rise to the regolithcompositions across all the maria are much more feldspathicthan the majority of large hand specimens and, in common withbasalts on other planets, they are close to low-pressure plagioclase-saturatedcotectic residual liquids which have evolved by removal of gabbrosin crustal magma chambers, or perhaps in giant lava lakes akinto topless Bushveld complexes. Any further debate could be resolvedby a 100 m drill core in a few mare locations. Field provenanceof samples from Mars, a planet half covered by flood basaltsand products of central volcanoes, will be little better thanfor those from the Moon. It will be important to encourage multipleworking hypotheses, rather than to rush to a consensus. KEY WORDS: lunar; basalt; highland; magma ocean; europium 相似文献
11.
J. G. Brophy Michael J. Dorais Julie Donnelly-Nolan Bradley S. Singer 《Contributions to Mineralogy and Petrology》1996,126(1-2):121-136
The rhyolite of Little Glass Mountain (73–74% SiO2) is a single eruptive unit that contains inclusions of quenched andesite liquid (54–61% SiO2) and partially crystalline cumulate hornblende gabbro (53–55% SiO2). Based on previous studies, the quenched andesite inclusions and host rhyolite lava are related to one another through fractional crystallization and represent an example of a fractionation-generated composition gap. The hornblende gabbros represent the cumulate residue associated with the rhyolite-producing and composition gap-forming fractionation event. This study combines textural (Nomarski Differential Interference Contrast, NDIC, imaging), major element (An content) and trace element (Mg, Fe, Sr, K, Ti, Ba) data on the style of zonation of plagioclase crystals from representative andesite and gabbro inclusions, to assess the physical environment in which the fractionation event and composition gap formation took place. The andesite inclusions (54–61% SiO2) are sparsely phyric with phenocrysts of plagioclase, augite and Fe-oxide±olivine, +/–orthopyroxene, +/–hornblende set within a glassy to crystalline matrix. The gabbro cumulates (53–55% SiO2) consist of an interconnected framework of plagioclase, augite, olivine, orthopyroxene, hornblende and Fe-oxide along with highly vesicular interstitial glass (70–74% SiO2). The gabbros record a two-stage crystallization history of plagioclase+olivine+augite (Stage I) followed by plagioclase+orthopyroxene+ hornblende+Fe-oxide (Stage II). Texturally, the plagioclase crystals in the andesite inclusions are characterized by complex, fine-scale oscillatory zonation and abundant dissolution surfaces. Compositionally (An content) the crystals are essentially unzoned from core-to-rim. These features indicate growth within a dynamic (convecting?), reservoir of andesite magma. In contrast, the plagioclase crystals in the gabbros are texturally smooth and featureless with strong normal zonation from An74 at the core to around An30. K, and Ba abundances increase and Mg abundances decrease steadily towards the rim. Ti, Fe, and Sr abundances increase and then decrease towards the rim. The trace element variations are fully consistent with the two-stage crystallization sequence inferred from the gabbro mineralogy. These results indicate progressive closed-system in situ crystallization in a quiescent magmatic boundary layer environment located along the margins of the andesite magma body. The fractional crystallization that generated the host rhyolite lava is one of inward solidification of a crystallizing boundary layer followed by melt extraction and accumulation of highly evolved interstitial liquid. This mechanism explains the formation of the composition gap between parental andesite and rhyolite magma compositions. 相似文献
12.
金星探测研究进展与未来展望 总被引：1，自引：0，他引：1
金星探测是解答太阳系类地行星形成演化,地球宜居性的形成和未来发展,以及外太阳系宜居星球搜索策略的关键.由于金星恶劣的环境条件、对探测技术的多重挑战和相对高昂的探测成本,金星探测和研究程度远不及月球和火星.自20 世纪90 年代后期,金星探测任务相对匮乏.本文梳理了国际上金星探测研究进展、关键科学问题及技术需求,提出了未来金星的探测目标和探测方式建议.目前,对金星大气和气候研究程度最高,包括大气结构和大气化学,能量平衡和热结构,云层和霾层,大气环流和动力学以及气候演化等.高层大气的物理化学和太阳风与金星的相互作用方面也有重要进展.金星地表和内部的研究则相对滞后,研究涵盖金星表面形貌特征,撞击和重塑历史,火山和构造活动,地表物质组成,地表和大气相互作用等,但受限于数据的空间覆盖率和较低的分辨率和精度,诸多重大问题尚未解答,迫切需要新的探测数据.除探测任务外,金星研究还依赖于地基观测、实验室模拟和数值模拟研究.地面模拟设施对支持金星探测任务研发和金星基础科学研究尤为重要.未来十年是中国开展金星探测的契机和研发相关技术的关键时期.本文可为对金星探测、行星科学、太阳系探测感兴趣的科学家和工程人员提供参考. 相似文献
13.
Zhenguo ZHANG Nianqiao FANG Lianfeng GAO Baoling GUI Muhua CUI 《Frontiers of Earth Science》2008,2(1):41-48
The Cretaceous is an important period in which many geological events occurred, especially the OAEs (oceanic anoxic events)
which are characterized by black shale, and the oxic process characterized by CORBs (Cretaceous oceanic red beds). In this
paper, the causative mechanism behind the formation of black shale and the oceanic red beds are described in detail. This
may explain how the oceanic environment changed from anoxic to oxic in the Cretaceous period. It is suggested that these two
different events happened because of the same cause. On the one hand, the large-scale magma activities in Cretaceous caused
the concentration of CO2, the release of the inner energy of the earth, superficial change in the ocean-land, and finally, the increase of atmospheric
temperature. These changes implied the same tendency as the oceanic water temperature show, and caused the decrease in O2 concentration in the Cretaceous ocean, and finally resulted in the occurrence of the OAEs. On the other hand, violent and
frequent volcanic eruptions in the Cretaceous produced plenty of Fe-enriched lava on the seafloor. When the seawater reacted
with the lava, the element Fe became dissolved in seawater. Iron, which could help phytoplankton grow rapidly, is a micronutrient
essential to the synthesis of enzymes required for photosynthesis in the oceanic environment. Phytoplankton, which grows in
much of the oceans around the world, can consume carbon dioxide in the air and the ocean. Meanwhile, an equal quantity of
oxygen can be produced by the phytoplankton during its growth. Finally, the oxic environment characterized by red sediment
rich in Fe3+ appeared. The anoxic and oxic conditions in the Cretaceous ocean were caused by volcanic activities, but they stemmed from
different causative mechanisms. The former was based on physical and chemical processes, while the latter involved more complicated
bio-oceanic-geochemical processes.
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Translated from Marine Geology & Quaternary Geology, 2007, 27(3): 69–75 [译自: 海洋地质与第四纪地质] 相似文献
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《Comptes Rendus Geoscience》2015,347(3):153-158
The detection and characterization of exoplanets have made huge progresses since the first discoveries in the late 1990s. In particular, the independent measurement of the mass and radius of planets, by combining the transit and radial-velocity techniques, allowed exploring their density and hence, their internal structure. With CoRoT (2007–2012), the pioneering CNES space-based mission in this investigation, about thirty new planets were characterized. CoRoT has enhanced the diversity of giant exoplanets and discovered the first telluric exoplanet. Following CoRoT, the NASA Kepler mission has extended our knowledge to small size planets, multiple systems and planets orbiting binaries. Exploring these new worlds will continue with the NASA/TESS (2017) and ESA/PLATO (2024) missions. 相似文献
16.
Current views of the origin and evolution of single and binary stars suggest that the planets can form aroundmain-sequence
single and binary stars, degenerate dwarfs, neutron stars, and stellarmass black holes according to several scenarios. Planets
can arise during the formation of a star mainly due to excess angular momentum leading to the formation of an accretion-decretion
disk of gas and dust around a single star or the components of a binary. It is the evolution of such disks that gives rise
to planetary systems. A disk can arise around a star during its evolution due to the accretion of matter from dense interstellar
clouds of gas and dust onto the star, the accretion of mass froma companion in a binary system, and the loss of matter during
the contraction of a rapidly rotating star, in particular, if the star rotates as a rigid body and the rotation accelerates
with its evolution along the main sequence. The fraction of stars with planetary systems is theoretically estimated as 30–40%,
which is close to the current observational estimate of ∼34%. 相似文献
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M. Jayananda R. V. Gireesh Kowete-u Sekhamo T. Miyazaki 《Journal of the Geological Society of India》2014,84(1):5-28
We present field and petrographic data on Mafic Magmatic Enclaves (MME), hybrid enclaves and synplutonic mafic dykes in the calc-alkaline granitoid plutons from the Dharwar craton to characterize coeval felsic and mafic magmas including interaction of mafic and felsic magmas. The composite host granitoids comprise of voluminous juvenile intrusive facies and minor anatectic facies. MME, hybrid enclaves and synplutonic mafic dykes are common but more abundant along the marginal zone of individual plutons. Circular to ellipsoidal MME are fine to medium grained with occasional chilled margins and frequently contain small alkali feldspar xenocrysts incorporated from host. Hybrid magmatic enclaves are intermediate in composition showing sharp to diffused contacts with adjoining host. Spectacular synplutonic mafic dykes commonly occur as fragmented dykes with necking and back veining. Similar magmatic textures of mafic rocks and their felsic host together with cuspate contacts, magmatic flow structures, mixing, mingling and hybridization suggest their coeval nature. Petrographic evidences such as disequilibrium assemblages, resorption, quartz ocelli, rapakivi-like texture and poikilitically enclosed alkali feldspar in amphibole and plagioclase suggest interaction, mixing/mingling of mafic and felsic magmas. Combined field and petrographic evidences reveal convection and divergent flow in the host magma chamber following the introduction of mafic magmas. Mixing occurs when mafic magma is introduced into host felsic magma before initiation of crystallization leading to formation of hybrid magma under the influence of convection. On the other hand when mafic magmas inject into host magma containing 30–40% crystals, the viscosities of the two magmas are sufficiently different to permit mixing but permit only mingling. Finally, if the mafic magmas are injected when felsic host was largely crystallized (~70% or more crystals), they fill early fractures and interact with the last residual liquids locally resulting in fragmented dykes. The latent heat associated with these mafic injections probably cause reversal of crystallization of adjoining host in magma chamber resulting in back veining in synplutonic mafic dykes. Our field data suggest that substantial volume of mafic magmas were injected into host magma chamber during different stages of crystallization. The origin of mafic magmas may be attributed to decompression melting of mantle associated with development of mantle scale fractures as a consequence of crystallization of voluminous felsic magmas in magma chambers at deep crustal levels. 相似文献
19.
本文从下述六个方面对岩浆包裹体的研究状况及意义进行评述:1.岩浆包裹体的形成机制和分类;2.岩浆包裹体的测温研究;3.岩浆包裹体的测压研究;4.岩浆包裹体的化学成分;5.利用岩浆包裹体进行实验岩石-矿物学研究:6.岩浆包裹体可做为矿化作用指示剂。虽然有几类异常岩浆包裹体(特别是在月岩样品中)还无法加以解释,但是。岩浆包裹体可以提供大量有关岩浆结晶演化、岩浆不混溶作用、岩浆混合作用、火成侵位时挥发组分的含量、性状及演化、玄武岩浆起源、以及岩浆岩体的潜在含矿标志等重要情报。其中有些资料,从其它来源无法获得。岩浆包裹体研究已经成为现代火成岩石学的一个不可缺少的独立分支,其前景十分广阔。 相似文献
20.
长白山天池火山老虎洞期火山活动发生在更新世晚期白头山组碱性粗面岩喷发之后,火山活动的产物主要为玄武岩质火山碎屑岩和少量玄武岩质或粗面岩质熔岩;老虎洞组火山岩的稀土元素地球化学特征介于早期玄武岩和气象站组碱流岩两者之间,将二者有机地联系在一起,使整个天池火山岩的演化趋势更加清晰。老虎洞组火山岩的存在充分证明了天池火山的粗面岩类与该区早期的大量玄武岩具有成因联系。长白山天池火山活动的成因并非简单地用西太平洋板块的俯冲作用所能解释的。 相似文献