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central
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    Study on Mineralogy and Geochemistry of Polymetallic Nodules from the Central and Eastern Pacific Ocean
    太平洋中部多金属结核矿物地球化学研究
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    A Brief Account of the Earthquake with M=7. 7 Occurred on May 26, 1983, in the Central Japan Sea
    1983年5月26日日本海中部7.7级地震概况
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    RELATION BETWEEN LARGE EARTHQUAKES IN CENTRAL CHINA AND EARTH'S ROTATION
    中国中部大震与地球自转的关系
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    K-Ar AGE CONTOUR MAP OF LIAOHE GROUP, CENTRAL LIAONING, AND ITS GEOLOGICAL IMPLICATIONS
    辽宁中部辽河群K-Ar年龄等值图及其地质意义
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    A NEW ADVANCE ON STUDY OF THE EARLY CRETACEOUS STRATA IN THE EASTERN MARGIN OF THE CENTRAL SONGLIAO BASIN,JILIN PROVINCE
    松辽盆地中部东缘早自垩世地层研究的新进展
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    Late Permian Eustatic Fluctuation in North Part of Central Yangtze Platform and Its Influence on Biotic Crisis Events
    中扬子北缘二叠纪晚期海平面变化对生物危机事件的影响
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    Application of Multi-level Recursive Regression Method in Groundwater Resources Assessment in the Plain Area of Central Jilin
    多层递阶回归方法在地下水资源评价中的应用
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    Trend Surface Analysis of the Thickness of the Late Permian Coal-bearing Formation in the Central Part of Guangxi Province
    桂中晚二迭世含煤建造厚度趋势面分析
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    The Tectonic Characteristics and Mechanism of the Simingshan Dome,Central Hunan
    湘中地区四明山穹窿构造特征及其形成机制
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    SEISMICITY PATTERN IN THE CENTRAL SOUTH PART OF THE NORTH CHINA PLAIN REGION AND THE HEZE M5.9 EARTHQUAKE
    华北平原区中南部地震活动图象与菏泽5.9级地震
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  central
In our paper [KR] we began a systematic study of representations of the universal central extension[InlineEquation not available: see fulltext.] of the Lie algebra of differential operators on the circle.
      
In the present paper we study the remaing nontrivial case, that of a negative central charge-N.
      
We consider some remarkable central elements of the universal enveloping algebraU(gl(n)) which we call quantum immanants.
      
We modify the Hochschild φ-map to construct central extensions of a restricted Lie algebra.
      
Such central extension gives rise to a goup scheme that leads to a geometric construction of unrestricted representations.
      
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Ⅰ. The Yinshan district as an example of "activizing region" in the Chinese platform One of the most typical localities that show clearly the phenomenon of"activization of platform" (активи. зация платформы) is the Yinshan region, aneast western mountain range on the border between the North-China plain andthe Mongolian plateau. It has long been recognized as a platform because ofthe presence of a folded foundation Pre-Sinian in age. However, owing to thefacts that Mesozoic crustal movements and magmatic activities...

Ⅰ. The Yinshan district as an example of "activizing region" in the Chinese platform One of the most typical localities that show clearly the phenomenon of"activization of platform" (активи. зация платформы) is the Yinshan region, aneast western mountain range on the border between the North-China plain andthe Mongolian plateau. It has long been recognized as a platform because ofthe presence of a folded foundation Pre-Sinian in age. However, owing to thefacts that Mesozoic crustal movements and magmatic activities are importantwithin this area, some geologists including G Schoenmann, hold that it is ageosynclinal region. It is Ю. М Шейманн who first noticed the phenomenon of activizationappearing in the Chinese platform. В. М. Синицын in his "Строенив и развитиекитайской платформы" indicates that some of the mountain ranges includingYinshan, which have been formerly referred to the folding belts developingfrom geosynclines, are in fact the internal structures of the Chinese platform. In this paper the writer after the opinion of В. М. Синицын, assigns theYinshan area as one of the "activizing regions" in the Chinese platform, andgives more detailed descriptions and discussions mainly on the point of thehistory of its stratigraphic development. Really it is a fact that the Yinshan region has an old folded foundationwhich is composed of metamorphic complex including chiefly gneisses, schists,and old granitic intrusions apparently Pre-Sinian in age. Since the formationof this folded foundation during the Luliang movement (=Goto-Karelian mo-vement), the old land of the Yinshan region has "activized" or "resurrected"several times. As early as in the Sinian period, a depression prolonging in E-Wdirection happened on its southern border, where Sinian limestone 900 metresin thickness and in some places up to 9,620 metres was so deposited. During a long time of the Palaeozoic era, the Yinshan old land was in the poriod ofdenudation except some Cambrian marine limestones only 144 metres in thick-ness deposited in the western part. At the end of the Palaeozoic era, local acti-vization with the formation of continental basin-deposits of Permian age, up to1,380 metres in thickness, as found in the Tachingshan area again happened.In the middle Mesozoic era, the Yinshan region came to a period of strongactivity. Structural depressions duo to "Процесс аркогенеза" occurred universallywithin the whole area and magmatie activities in large magnitude associatedthis crustal movement, so that a great sequence of freshwater basin-depositswith intercalations of volcanic beds, up to 8,000 metres in total thickness wereformed. During the formation of these strata, especially at the end of Mesozoic,interruptions of depositon happened frequently, folds and thrusts were abund-antly formed, and intrusive bodies of "young granite" were produced hereand there. In the Tertiary period, the Yinshan region was violently faulted, andvolcanic activities still happened, producing the basalt lava flow spreading ina wide area. The activity of the Yinshan old land has not ceased even to-dayas shown by the facte that its whole area is in the process of uplift and by thepresence of an earthquake zone known in the historical time. Ⅱ. To what Geotectonic Unit does the Southeastern Coastal Region of China Belong? On the Southeastern coast of China there is a district where geotectoniccharacteristics have never been recognized clearly. It is A. W. Grabau who firstreferred it to an old land named "Cathaysia". J. S. Lee holds the same opinion.In his geotectonic map of China, B. M. Синицын also assigns this region to aplatform and marks it as a part of his "Южно-китайский платформенный массив".However, there is still another opinion opposed to this. A. C. Хоминтовский, forinstance, renders recently this district to a geosynclinal region and proposes thename "Minche Pacific folding zone" for it. H. T. Yang and T. Y. Yu agreewith him. In the year 1954, the writer in his compilation-work connected with thegeology of Fukien and Kwangtung, found that the geotectonic characteristics ofthe southeastern coastal region of China are not only unagreeable with thosefound in a common platform on the one hand, but also contrasting, with thoseof a geosynclinal region on the other. In fact, it cannot be referred suitably toany geotectonic unit except to the intermediate type as shown by the history ofits geological development. Apparently it is an "activizing" or "resurrected" platform. During the Pre-Sinian crustal movement (the Luliang movement), a foldedfoundation composed of old gneisses, schists, and phyllites was completely for-med. Obviously this is a part of the broad old land of Southern China. In the earlier stage of the Palaeozoic era, the whole area of this region wasexposed in the air and under denudation. Hence, no deposit of any kind wasformed. After the Caledonian movement, depressions happened in the western partof this region, where the Devonian-Lower carboniferous continental deposit, theNanching series consisting mainly of quartzite, conglomerate and shale has beenformed, but the other parts were still under denudation. These facts show thatthis region was still a land at that time. Uralian and Lower Permian limestones, known respectively as the Chuan-shan limestone and the Chihsia limestone, separated from each other by adisconformity, spread widely in this region. This indicates that the marine trans-gressions really happened in the southeastern coastal region of China. However,the thicknesses of these limestones (only 30 metres and 150 metres respectively)and their uniformity in the horizontal direction show that the sea at thosetimes was shallow, and the magnitude of subsidence of the earth crust withinthis region was small. The unnoticed lateral changing of lithological charactersof these limestones proves the same fact. Undoubtedly these limestones arenothing but the marine deposits of platform-type. From Upper Permian toTriassic, this region was under a condition of alternation of transgression andregression of the sea. Owing to the fact that the amplitude of oscillation of theearth crust of this region at that time was small, the deposits formed duringthe marine transgression were thin and interrupted again and again by disconfor-mities (or even unconformities). Sometimes continental deposits are intercalated. Since the later period of Triassic, the southeastern coastal region has neverbeen covered by the sea again. And, a new condition began to happen in LowerJurassic. Here, the old land became to "resurrected", so that a series of depres-sing belts were formed as a result of "Процесс аркогенеза". In association withthe subsidence of these depressions, continental beds with a total thicknessup to 3,000 metres were deposited. In the beds interruptions frequently occurred.Folds were abundants, although they or at least some of them were intermediatetype. At the same time, magmatic activities were significant. Itappearedfirstly in the form of volcanic eruptions as recorded by a great sequence of beds consisting of tuff and rhyolite intercalating in the continental bedsmentioned above. And then, at the end of the Mesozoic, numerous graniticbodies were produced. Coming to the Cenozoic era, this region still sufferedfrom rather strong crustal movements accompanied by basalt lava eruptions. Theactivity of the old land has not yet been ceased even to-day as marked by thepresence of a famous earthquake zone between Kwangtung and Fukien, and theabundance of hot springs which widely spread within this region. All theseshow the typical characters of an "activizing" or "resurrected" platform. Final-ly, the complexity of the types of mineral deposits found in Fukien and Kwang-tung also proves the geotectonic nature of this region. Summarizing the whole matter, we may say that the southeastern coastalregion of China was originally an old land. Although it has been agian andagain submerged by the sea, the resulting marine deposits are entirely differentfrom those of geosynclinal region. In the middle of Mesozoic, this region beganto be active violently again, producing a series of depressions or "secondarygeosynclines", in which thick continental beds were deposited, and, at the sametime, folds of intermediate type, serious volcanic eruptions and magmatic intru-sions were produced. Hence, to refer the southeastern coastal region of China toan "activizing" platform is quite strongly proved. The northwestern boundary of this "activizing" platform is generally onthe line starting from central Chekiang through central Kiangsi to the Sou-thwestern part of Kwangtung, because the history and characteristics of geolo-gical development of the Southeastern Kiangsi and Central-southern Kwangtungare quite similar to those of Fukien and Eastern Kwangtung. As to the nomination of this geotectonic unit, the writer proposes to callit "Cathaysian activizing region". This name is derived from the "Cathaysia"of A. W. Grabau but adds, according to necessity, the meaning of activizing or"resurrected" characters of this region. The so-called "Minche Pacific foldingzone" of A. C. Хоминтовский is obviously unacceptable because it entirely doesnot coincide with fact. Compared with the "aetivizing" platforms found in other parts of theworld, the Cathaysian coastal "activizing" platform has its own characteristics,especially shown by the presence of numerous, widely spread, small depressionsor "secondary geosynclines", and the acidic magmatic activities appearing on alarge scale. All these indicate that this is a special type differing from all theknown "acti

~~

Ⅰ. General SKETCH The Cenozoic basalt lavas are widely distributed along the coastal regionand its adjacent districts in eastern China. They form either widespread plateausor scattered mesa-like hills; and, in some places, the volcanic craters are stilladmirably preserved to-day. These basalt sheets were erupted extensively in lateTertiary and early Quaternary times. They belong to the multiple-vent basalts,but not the plateau basalt in the type of eruption. In this paper are given the results of a petrochemical...

Ⅰ. General SKETCH The Cenozoic basalt lavas are widely distributed along the coastal regionand its adjacent districts in eastern China. They form either widespread plateausor scattered mesa-like hills; and, in some places, the volcanic craters are stilladmirably preserved to-day. These basalt sheets were erupted extensively in lateTertiary and early Quaternary times. They belong to the multiple-vent basalts,but not the plateau basalt in the type of eruption. In this paper are given the results of a petrochemical study of the Ceno-zoic basalt in eastern China. Geological and petrographical studies of the basaltsare not described in detail. Judging from the chemical compositions, the mostoutstanding characteristic feature of the most basaltic rocks is the richness inalkalis, especially in K_2O, also the undersaturation in silica, and, therfore,the most of the basalts distinctly belong to the alkaline rock suite. Such chemicalcharacters are closely related to modal compositions. The general petrogra-phical characters of the basalt may be now as well described. In North Chinaand South Manchuria most basalts are trachy basalt and its allied types, andoccasional nepheline basalt. The constituent minerals of these basalt are cha-racterized by the presence of anorthoclase, potash-adesine, plagioclase, titanaugite,as well as by the abundance of olivine. In South China the main basalt is olivinebasalt, consisting of olivine, augite, and plagioclase as usual. At some placesthe basalt may be slightly silica saturated that the occasional presence of hyper-thene and quartz (xenocryst) is noteworthy. In North Manchuria the dominant basalt is leucite basalt, containing leucite and olivine as phenocryst and groundmass constituent. Xenocryst of quartz and feldspar grains are sometimes present.In Taiwan Province, basalt of Kuanyinshan volcano is of the tholeiite type,but, in some other districts, the alkaline basalt with feldspathoidal constituentalso occurs. In view of the above-mentioned facts, the petrographical difference seemsto be matched by the differences of the major tectonic forms of China. Thesefacts may be tabulated below: Geographical region Tectonic forms Basalt type 1. North Manchuria Granitized region in Varisclde Leucite basalt 2. North China & South Precambrian Sino-Korean Trachybasalt Manchuria massive 3. South China Huanan platform in Yenshanide Olivine basalt 4. Taiwan Himalayide Tholeiite basalt Ⅱ. Regional INVESTIGATION In Table 1 the chemical analyses of the Cenozoic volcanic rocks in easternChina published up to 1951 were collected, of which 74 analyses are basalticrocks. The available analyses of every basalt sheet are taken an average to re-present the regional composition of the basaltic rocks. The localities of the basaltsheets where the analyzed chemical data are referable are shown in Figure 1.In all, 21 localities of basalt are investigated. The average chemical compositionsof each basalt locality, together with the normative minerals, Niggli's valuesand Zavarickij's numbers are given in Tables 2 A and 2 B respectively (localnos. in Table 2 correspond to the numerous in circle in Figure 1). For theconvenience of comparison, the average chemical composition of some standardbasalts (after S. R. Nockolds, 1954), some alkaline basalt in New Zealand (afterW. N. Benson, 1944) and Uganda (after A. Holmes, 1937), and the world's ba-salts, together with the normative minerals, Niggli's values and Zavarickij'snumbers of our calculation, are selected and given in Tables 3A, 3B, 7A, 7Brespectively. As mentioned above, the chemical composition of eastern China basalt ischaracterized by the high content of alkalies, and especially the K_2O. This cha-racter is definitely revealed by the normative feldspar, which is given in Table2 A and graphically shown in Figure 2. From this graphical representation,it is recognized that the normative feldspar becomes increasingly enriched ormolecular from South China to North Manchuria. Although the projected points appear to be scattered, a trend of clustering of the normative feldspars in accor-dance with its geographical distribution is apparent upon close inspection. Inthe normative pyroxene diagram, Figure 3, it is shown that most basalts of easternChina are rich in Wo molecular, falling near the Di-Hd line; On the otherhand, those of Kuanyinshan basalts of Taiwan Province are poor in Wo andcluster in the central part of the Di-Hd-Fs-En field. Therefore, that the easternChina basalt, excluding that of Kuanyinshan, belong to the alkaline rock suiteis justified. The comparison diagrams of qz, al-alk, C-(al-alk) and K-mg ofNiggli's values, based on the data given in Tables 2 B, 3 B, and 7 B, are gra-phically shown in Figs. 4, 5, 6 and 7 respectively. As will be seen from thesefigures, in general, the qz and al-alk of Niggli's value are lower, but C-(al-alk) and K-mg are higher than those of some common basalts. Fig. 8 isZavorickij's petrochemical vector diagram, from which the petrochemical cha-racters of high alkaline property in eastern China basalts are clearly justified. Ⅲ. Serial COMPARISON For ascertaining and understanding the general chemical characters, theCenozoic eastern China basalt and its differentiated associations are divided,based on the SiO_2 content, into 5 chemical types, the average composition ofwhich is given in Table 5A. As the chemical composition of Kuanyinshanvolcanic rocks in Taiwan Province shows a distinct calc-alkaline affinity, it is,therefore, dealt with the same procedure as well. The average chemical compo-sition of the volcanic rocks is given in Table 5 B. Since the Cenozoic basalt ineastern China covers the region adjacent to the Circum-Japan Sea and the Ja-panese Archipelagoes which are well known by the occurrence of alkaline andcalc-alkaline rock suite respectively. The serial variation in the chemical com-position of eastern China volcanic rocks is examinated in comparing them withthose of the Circum-Japan Sea and the Japanese volcanic rocks. The data usedfor the Circum-Japan Sea and Japanese rocks, which are given in Tables 6 A and6 B, are based on Tomita's and Yamada's calculated results respectively. Zavaric-kij's number of the same rocks, based on Zavarickij's data, is given in Table6 C. Following various petrochemical methods, some graphic diagrams are cons-tructed in order to express the chemical characters of the rock series of easternChina more definitely. The difference in chemical composition as comparedwith the Circum-Japan Sea alkaline rock suite is shown in the normal varia-tion diagram Figure 9. Other petrochemical indices (proposed by Peacock, Hol- mes and Tomita respectively) obtained are summarized below: Ⅰ Ⅱ Ⅲ Ⅳ alkali-lime index (Fig. 10) 65.5 59.0 63.0 52.0 alkali-alumina index (Fig. 11) -- -- 67.8 63.3 Ol-Q index (Fig. 12) 20.0 43.0 72.5 76.5 Ne-Hy index (Fig. 13) -- -- 55.0 59.9 Di-C index (Fig. 14) 46.5 46.5 -- -- Ⅰ. Japanese volcanic rocks; Ⅱ. Taiwan volcanic rocks; Ⅲ. Circum-Japan Sea alkaline suite; Ⅳ. eastern China volcanic rocks.From these graphical solutions in Figs. 10-14, it may be justified that thevolcanic rocks in eastern Asia have increasingly enriched the alkali contentfrom the Japanese Archipelagoes to the mainland of China. Figure 15 is avariation diagram of the normative feldspar of the eastern China series, incomparison with that of the Circum-Japan Sea region, the Japanese Archipela-goes and New Zealand. As will be seen from the diagram, the variation of thenormative feldspar of eastern China rock series is quite discriminative. Notonly is it richer in or molecular, but the positions of point N and O (corres-pond to the respective Ol-Q and Ne-Hy indices as shown in Figs. 12 and 13)of the eastern China series are also in a later course than the others. Figure 16is a paragenetic diagram of the normative plagioclase and pyroxlene of theeastern China series. In the variation diagram of the normative pyroxene, Fig.17, the distinct difference in the course of variation between the alkaline andcalc-alkaline series is clearly revealed. In this connection, the directon of varia-tion in the normative pyroxene of the alkaline series differs from that of thecalc-alkaline series. It is also notable that the range of variation in the easternChina series is smaller, due to the presence of higher Wo molecular in bothbasic and acidic types, as compared with that of the Circum-Japan Sea series.Figure 18 is Zavarickij's petrochemical vector diagram of the eastern Chinaseries compared with that of Circum-Japan Sea and Japanese series. It may be acomplemental diagram of the serial comparison diagram of eastern Asia volcanicrock series, prepared by Zavarickij (cf. A. N. Zavarickij's Introduction to Petro-chemistry of Igneous Rocks, 1950, Fig. 61, p. 205, in Russian). The distinctdifference of these rock series may be clearly observed in the graphical solution.In Table 7 A is given the average chemical composition of eastern China basalt,together with the composition of basaltic rocks of the world (including olvinebasalt and Toleiite, Ocean basalt and Continent basalt) for comparison. Theeastern China average is very similar to the average composition of the olivine- basalt of the Circum-Japan Sea region (based on Tomita, 1935, and recalculatedby the writer), while it differed more or less from that of any of the world'sbasalts by the high content of alkali and especially K_20. This character isdefinitely revealed by the normative feldspar and pyroxene, which are graphi-cally shown in Figs. 19 and 21 respectively. Figure 20 is Zavarickij's petroche-mical diagram of the world's basalt. As shown in these diagrams, it suggests atransitional relation rather than a sharp cleft in the petrochemical charactersof the world's basalts. There are no distinct types of basalt magma but rathera continuous series from silica saturated (tholeiitic) to silica-undersaturated(olivine-basalt) rock, although the chemical distinction may be too subtle to beread directly from chemical analyses. Ⅳ. ORIGINAL Basalt Magma The original magma of eastern China basalt belongs to the olivine basaltmagma type. In this discussion it is assumed that the primary olivine basaltmagma is melted from a crust of peridotitic crystalline rock in the upper partof the sima layer. Olivine basalt magma may be modified by the gain of alimited amount of silica and some alkalies to produce a derived melt, whichappears to coincide with the tholeiitic

~~

The character of a transmitting source plays an important part in seismic model experiments for obtaining a distinct wave form with short duration on the receiving record. The present paper describes two kinds of transmitting sources: the source of central expanding force and the source of normally concentrated force. A cylindrical piezo-electrical crystal of barium titanate inserted in the central hole of a circular plate was used as the source of a central expanding force. It is found when...

The character of a transmitting source plays an important part in seismic model experiments for obtaining a distinct wave form with short duration on the receiving record. The present paper describes two kinds of transmitting sources: the source of central expanding force and the source of normally concentrated force. A cylindrical piezo-electrical crystal of barium titanate inserted in the central hole of a circular plate was used as the source of a central expanding force. It is found when the initiating electrical pulse has a time duration corresponding to one cycle of the radial resonant frequency of the crystal, the received seismogram shows the most distinct wave form with short duration. A rod type transducer of barium titanate in contact with the edge of a semi-circular plate with a thickness of 2mm was used as a source of normally concentrated force. It is found that when the diameter of the transducer is less than 5mm, the directional effect of intensity is similar to that of a point source. In general, this kind of transducer will produce a satisfactory wave form in the receiving record. The detector consisting of a barium titanate cylinder attached to the end of a brass rod with the same diameter were used in all the experiments.

本文討論二維模型試驗所用的二种振源:扩张中心型的振源和垂直集中力型的振源。扩张中心型的振源系用压电钛酸鋇短柱体的径向伸縮,以柱面为发射面而得到的。实驗証明,柱面上的伸縮主要是由直径决定的单頻振动。因此,用寬度相应于径向振动周期的矩形电脉冲来激发晶体时,可以消除由晶体自由振动所造成的“余震”,从而得到短暫的声脉冲。单力型振源是一个用钛酸鋇晶体和黄銅棒制成的杆状发射器。这种发射器在工作頻率范围內,实际上是一个非周期性器件,因此不存在器件的自由振动問題。在实驗中研究了三种不同直径杆状发射器的发射强度与波形同发射方向角间的关系。

 
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