长白山火山的历史与演化

长白山火山跨越中朝两国,在我国境内包括天池火山、望天鹅火山、图们江火山和龙岗火山,火山活动从上新世持续到近代,是我国最大的第四纪火山分布区。长白山火山的母岩浆是钾质粗面玄武岩,将长白山火山岩区称钾质粗面玄武岩省,岩浆结晶分异作用和混合作用主导了岩浆演化过程。天池火山之下地壳岩浆房和地幔岩浆房具双动式喷发特点,一方面来自地幔的钾质粗厨玄武岩浆直接喷出地表;另一方面钾质粗面玄武岩浆持续补给地壳岩浆房,发生岩浆分离结晶作用和混合作用,导致双峰式火山岩分布特征和触发千年大喷发。西太平洋板块俯冲-东北亚大陆弧后引张是长白山火山活动的动力学机制。     

长白山天池火山的岩浆演化

长白山天池火山是由包括造盾阶段的玄武质岩石、造锥阶段和近代的粗面岩和碱流岩组成的 .REE ,不相容元素和Sr,Nd ,Pb同位素研究认为 ,不同阶段的岩石具有共同的岩浆成因与紧密的演化关系 ,其中结晶分异作用起了关键性作用 .玄武质粗安岩浆与碱流岩浆的共喷发表明天池下面存在地壳岩浆房和地幔岩浆房 .     

长白山天池火山造锥粗面岩新的K-Ar年龄

根据采集样品的野外产状,结合前人对天池火山造锥阶段粗面岩时代的研究以及本文给出的新的K-Ar年龄,比较了天池火山北坡和东北坡的造锥粗面岩喷发时代,分析了不同期次喷发的粗面岩的覆盖范围,发现天池火山东北坡粗面岩年龄明显新于北坡粗面岩年龄。天池火山东北坡造锥阶段粗面岩的最老年龄距今0.38Ma,属于中更新世晚期,是第3造锥阶段的喷发物。在东北坡未发现第1造锥和第2造锥阶段的喷发物。新给出的天池火山北侧和东侧2个钻孔资料表明,天池火山造锥粗面岩喷发之前存在距今约2Ma和约1Ma左右的更早期的粗面岩喷发过程。造锥阶段碱流质岩浆喷发持续时间可能在距今0.190～0.0192Ma     

长白山天池火山一次近代喷发物的特征

长白山天池火山是中国最具有潜在灾害性喷发危险的活动火山。在开展长白山天池火山近代喷发历史的研究中,通过野外考察、粒度分析、岩石化学研究,识别出了一套新的火山喷发物。这套喷发物分布于天池水面东北侧,为一套灰色多层火山碎屑堆积,厚约9.2m。下伏公元1668年的火山空降堆积。粒度分析表明,天池火山最近一次喷发物以空降堆积为主,夹一层薄层涌浪堆积,火山喷发类型为射气岩浆型。涌浪堆积碎屑物的分数维值为2.71。空降堆积的分数维值小于涌浪堆积,综合投点求出的分数维值为2.36。显微镜下可观察到鸡骨架状玻屑,无黏土矿物,为原生火山爆发堆积。火山碎屑堆积物中的浮岩岩石化学分析结果表明岩浆成分为粗面质。根据历史记录、地层层序关系、堆积物特征的综合分析,推测堆积物的形成时间为公元1903年     

大兴安岭中南段中生代的构造热演化

通过对大兴安岭中南段中生代火山 深成岩同位素年龄的测定 ,对不同阶段岩浆活动的构造背景进行分析 ,从而确立了该区构造岩浆演化的序列 :晚三叠世以含幔源包体的基性 超基性岩侵位为标志的初始幔隆 ,早 中侏罗世以辉绿岩岩墙群侵入为标志的中、上部地壳伸展 ,晚侏罗世强烈的粗面质火山岩喷发 ,早白垩世板内非造山性质的碱性 亚碱性花岗岩侵位 ,同时还形成了基性岩墙和玄武岩 .据此 ,可以认为中生代大兴安岭的隆升与幔隆背景下深部岩浆上涌密切相关 .这一研究为进一步探讨大兴安岭造山模式奠定了基础 .     

长白山天池火山千年大喷发2期空降浮岩对比

长白山天池火山的喷发历史和喷出物层序一直以来是人们关注的焦点。目前,对于千年大喷发以来空降堆积物,尤其是灰白色空降浮岩层之上的粗面质杂色空降浮岩的地层划分仍具有较大争议。文中通过对野外地层的详细观察,对2层空降浮岩层进行对比研究,发现两者之间没有沉积间隔,认为2期空降浮岩均应划分为千年大喷发的喷发物。下部赤峰期灰白色空降浮岩成分较为均一,呈棱角状,正粒序,分选较好;上部圆池期喷发为脉动式喷发,岩性为富土黄色浮岩和富黑色浮岩颗粒互层,浮岩呈棱角状,粒序不明显,分选较好。2期浮岩粒度呈正态分布,在中值和分选系数图中均投点于空降堆积区内。浮岩内斑晶以长石和辉石为主,但圆池期黑色浮岩内斑晶含量略高。赤峰期空降浮岩为灰白色碱流质,气孔较大,连续贯通,气孔壁薄。圆池期土黄色空降浮岩为粗面质,气孔连通,气孔壁略厚;黑色浮岩颗粒成分虽然也投点为粗面质,但Si O2含量明显较低,气孔度低,气孔壁厚。圆池期喷发强度较赤峰期喷发强度弱。多种岩浆成分说明长白山天池火山下具有复杂的岩浆系统,多种岩浆可能以分层的形式存在,赤峰期仅喷出了上部的碱流岩,圆池期的脉动式喷发喷出了不同层位的岩浆。     

黑龙江省科洛火山群火山地质研究

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.     

长白山天池火山全新世3期浮岩长石斑晶中熔体包裹体高温热台实验研究

长白山天池火山在全新世曾多次喷发,以往研究结果基本上认定至少有3期喷发物:距今约5,000a前淡黄色碱流质浮岩、距今约1,000a前灰白色碱流质浮岩和碎屑流以及距今约300a的黑色粗面质浮岩和熔结凝灰岩。喷发物斑晶矿物中含有众多熔体包裹体,形貌特征各有不同。经Leitz1350高温热台对天池火山全新世3期喷发物长石中熔体包裹体的均一法测温实验,结果表明第1,3喷发期的岩浆温度相差不大,而千年大喷发期较为复杂,揭示当时有2个不同温度段的熔体存在,为大喷发可能由2种岩浆注入和混合而触发的论点提供了线索。实验还证实,个体小的熔体包裹体易于均一,而个体较大的、尤其是含有大量子晶的熔体包裹体则很难均一;均一温度与熔体包裹体大小、何时从较快升温速率变为较慢升温速率、是否为初次升温时测量得出有关。同一颗熔体包裹体多次数升温至均一,每次得到的均一温度不同,而且每升温一次得到的均一温度均比前一次高,证实了均一过程中的确有H扩散的现象     

长白山天池全新世以来的火山喷发与灾害风险初探

概述了长白山天池火山全新世以来的喷发及其构造活动,其中喷发物以玄武质、碱流质为主,规模大。文中着重探讨了天池火山的风险性和未来的火山灾害。可为制定火山灾害对策提供科学依据。     

内蒙古乌兰哈达晚第四纪玄武岩岩石学特征

乌兰哈达火山群地处华北地块北缘内蒙地轴与边缘增生带的交接部位,晚第四纪玄武岩包括晚更新世和全新世2期。火山产物为玄武岩、玄武质熔结火山碎屑岩和松散火山渣,以玄武岩为主。Na2O+K2O含量高达5.94%~8.34%,平均为7.55%;K2O/Na2O1(0.48~0.59),属钠质碱性玄武岩。岩石化学和地球化学特征表明,玄武岩岩浆来自富集地幔,但经历了一定程度的分异及陆壳混染,为弱进化岩浆。晚更新世早期主要为碱性橄榄玄武岩,全新世主要为碱玄岩。玄武岩具大陆板内之属性,形成于大陆裂谷初期的构造环境。     

On the synchronism in the events within the core and on the surface of the earth: the changes in the organic world and in the polarity of the geomagnetic field in the phanerozoic

The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes in the organic world.     

On the maintenance of the axisymmetric part of the flow in the atmosphere

Summary The maintenance of the axisymmetric component of the flow in the atmosphere is investigated by means of a steady-state, quasi-geostrophic formulation of the meteorological equations. It is shown that the meridional variations in the time-averaged axisymmetric variables can be expressed as the sum of three contributions, one being due to the eddy heat transport, another to the eddy momentum transport, and a third to the convective-radiative equilibrium temperature which enters the problem through the specification of a Newtonian form of diabatic heating. The contributions by the large scale eddies are evaluated through the use of observed values for the eddy heat and momentum transports.The contributions from each of the three forcing mechanisms to the temperature and zonal wind fields are invstigated individually and found to be of about equal importance. The sum of the three contributions are also presented for the temperature, the zonal wind, the stream function associated with the mean meridional circulation and the corresponding vertical motion. Although the results fail to reproduce the main observed features of the lower stratosphere, they are found to be in good agreement with observations in the middle latitude troposphere. At any pressure level, for example, the computed mean zonal wind has a jet-like profile and the axis of the jet is found to slope to the south with height, as observed in the atmosphere.Based in part on a thesis submitted by the first author as partial fulfillment of the requirements for the Ph.D. degree at the University of Michigan. — Publication No. 194 from the Department of Meteorology and Oceanography, The University of Michigan.     

On the gravimetric undulations of the geoid and the deflections of the vertical

Summary The author mentions the aims of the World-wide gravity project he established in the Ohio State University in Columbus, in 1950. He outlines the practical procedure of the gravimetric computations of the undulationsN and the vertical deflection components and and emphasizes that only by the global international cooperation and additional gravity observations at sea carried out during the last decade it has been possible to gather to Columbus the needed gravity material. Since there exist still large gravimetrically unsurveyed areas it is of vital significance to study what gravity anomalies are best to be used for these regions. The given figures concerning the accuracy of theN, and , estimated theoretically and obtained in practice, indicate that in the gravimetrically well surveyed parts of the world like in Europe and the United States we can get gravimetrically on basis of existing gravity material theN-values with accuracy of about 5–10 meters, and and with the accuracy of about 1. The geoid undulationsN are already computed in Columbus for more than 6000 points of the northern hemisphere. The sample maps show the interesting geoid of Europe and vicinity between the latitudes 60° and 30° and longitude 5° W and 30° E, drafted on basis of more than 1000N-values computed at the corners of 1°×1° squares. It is interesting to realize that the geoid undulations in all this area are positive, the extreme values being between 40 and 50 meters. The geophysical significance of the geoid maps of this kind is pointed out.     

太平洋中部地磁台11年周期变化的研究

综合APIA、HONOLULU、PAMATAI 3个地磁台三分量的11年周期变化的形态后,可定性地提出该变化源于内场。如内源为核幔边界的电涡流,则其中心点应位于3台之间。     

On the variation in the geomagnetic dipole over the geological history of the Earth

The global database on the paleointensity, containing determinations of the virtual dipole moment (VDM) for a stable (normal) regime of the geomagnetic field in a time interval of up to 3.5 Ga, is supplemented by new VDM determinations and analyzed. The field generation process started no later than 3–3.5 Ga (earlier data are absent) at the stage of the Earth’s core formation. Since that time, the dipole value has differed from its present value by no more than an order of magnitude, and the deviations that have already been detected tend toward smaller values. The distribution of VDM values in the time interval 0–400 Ma is bimodal, which apparently reflects the presence of two different generation levels of the geomagnetic field distinguished by a relatively large value (close to the present field value) and a relatively small value (approximately half as large as the present value). The total duration of decreased VDM values appreciably exceeds that of increased VDM values (179.1 and 28.6 Myr, respectively). On the whole, data on the paleointensity do not contradict the hypothesis about the dipole nature of the field over the last 400 Myr; however, the number of determinations at high paleolatitudes is too small to draw decisive conclusions on the validity (or invalidity) of the dipole field approximation based solely on paleointensity data.     

Magnetic stratigraphy of the Ordovician in the lower reach of the Kotuy River: the age of the Bysy-Yuryakh stratum and the rate of geomagnetic reversals on the eve of the superchron

Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary.     

Comparison Between the Nutations of the Planet Mars and the Nutations of the Earth

The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth.     

Evolutionary Changes in the Configuration of the Magnetic Field of the Solar Corona in the Epoch of the Minimum

Geomagnetism and Aeronomy - The evolution of the magnetic configuration in the solar corona is studied. The curvature of the K-corona helmets obtained from an analytical approximation of the...