The Hida granites, classified into the pre–

and plutons in this study, are important components of the Hida belt, which is a Paleozoic–Mesozoic basement of the Japan arc and underwent Permian to Triassic metamorphism during the collision between the North and South China blocks. This study performed zircon U–Pb dating and whole–rock geochemical analyses for the Hida granites from the major plutonic bodies to reveal the geotectonic history and the origin of the Hida belt. Obtained ²³⁸U–²⁰⁶Pb weighted mean ages exhibit 239.1–238.3 Ma for the Katakaigawa body (augen granite) and 200.5–180.9 Ma for the other bodies (non–deformed granitoids), and these ages can be correlated to the pre– and plutons, respectively. Geochronological results suggest that the mylonitization forming augen granites of the pre– plutons occurred during its intrusion and indicate that the plutons are distributed widely in the Japan Sea side of the Hida belt. Meanwhile, geochemical characteristics of whole–rock major and trace element compositions indicate that the pre– and plutons seem difficult to distinguished geochemically and suggest that both of them are adakitic and non–adakitic granites generated in subduction zone.

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Some Middle-Late radiolarian shells were detected associated with Early Cretaceous autochthonous radiolarian and anmmonite assemblages from the Lower Cretaceous formations of molluscan facies in eastern Shikoku.
The modes of occurrence on these Middle-Late radiolarian shells were summarized as follows: 1) Specific diversity of associate Middle-Late radiolarians are restricted within several species of Tricolocapa and Stichocapsa genera. 2) Most of these radiolarians are subspherical with closed distal end in shape. 3) Their sizes are limitted to 100-150μm in length and 80-100μm in diameter. 4) Lithologically, they are contained in laminated sandy mudstones and sandy siltstones. 5) Among these older radiolarians, Tricolocapsa plicarum, T conexa, T. fusiformis?, Stichocapsa convexa and S. naradaniensis are the index species of Middle to early Late age. But the other species whose final appearances are known within Earliest Cretaceous such as Cinguloturris carpatica, Pseudodictyomitra primitiva and Eucyrtidiellum pyramis have possibility that their ranges reach into Barremian age. 6) All these elements are yielded from the first transgressive sediments successively just above the Lower Cretaceous nonmarine formations in the Northern and the Middle Chichibu Terranes. 7) These ammonites and radiolarians bearing Lower Cretaceous formations are the continental shelf or upper submarine terrace sediments, because they construct cyclothem together with the coal-bearing and blackish sediments which unconformably overlie both the melangé type formations in the Northern Chichibu Terrane and the molluscan facies Middle-Late formations in the Middle Chichibu Terrane.
The above-mentioned evidences showed that these radiolarian shells are the reworked fossils in the same manner as other detrital clastics in the Cretaceous sediments, probably derived from the Pre-Cretaceous basement similar to the Northern and the Middle Chichibu Terranes. Therefore, it is necessary to consider the problem of reworking and mixing by older materials when we deal with the microfossil biostratigraphy at nearshore sediments on such continental shelf and/or upper submarine terrace.

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In recent years, important breakthroughs have been made in the exploration of the northwestern margin of Mahu sag in Junggar basin. The estimated amount of oil deposits in this region seems to be as large as 100-million-ton lithologic reservoir. A certain scale of oil reservoirs was found in the

Badaowan formation, which indicates that the reservoir has promising prospects for exploration. The geochemical characteristics of crude oil and Permian source rocks and oil accumulation factors are studied in this paper. The results show that carbon isotope values (δ¹³C) and the biomarker parameters (γ/C₃₀H and C₂₄Tet/C₂₆TT) have a good application in oil source correlation. Crude oil in reservoir was generated from Permian Fengcheng (P₁f) source rock. The main hydrocarbon expulsion period of the P₁f source rock was between late Permian and middle Cretaceous. The crude oil migrated upward into the lithologic traps through faults or superimposed sand bodies.

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A small amount of greenstone is found in the accretionary complex of the Keisoku Massif. It occurs as lavas, dykes, volcanic breccias and tuffs in the melange zone of the chert-clastics sequences. The greenstones metamorphosed into the greenschist facies contain igneous augite, titaniferous augite and titaniferous hornblende.
    Fourteen samples of the greenstones were analyzed in this study. On the basis of discriminating diagrams, most greenstones have a chemical affinity with T- or P-type MORB, AB, OIT, OIA, WPB, WPA or WPT. Three greenstones have high ratios of Nb/Y versus Nb/Zr at high Nb/Zr ratios.
    The Permian Izuru Formation occurs in the Ashio Mountains, and mainly consists of greenstones. The chemical characteristics of Izuru greenstones are of the types OIT and OIA. Geological evidence also indicates that the Izuru Formation originated from a Paleozoic seamount. Greenstones of the Keisoku Massif are interbedded with olistostrome in the melange zone of the accretionary complex, and have a chemical affinity with OIT and/or OIA. It is suggested that most greenstones of the Keisoku Massif were accreted as slices derived from the Izuru seamount.

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Recent paleomagnetic surveys revealed that Northeast Japan was rotated counter-clockwise about 20° during the middle Miocene opening of the Japan Sea, whereas Southwest Japan clockwise about 45°. A reconstruction of the pre-Miocene Japanese Islands is attempted on the basis of the following main premises. 1) The bending of zonal geologic units in the Central Japan was caused by the collision of the Izu-Ogasawara Ridge after the opening of the Japan Sea. 2) The Yamato Bank and several plateaus in the Japan Sea are regarded as continental fragments and there were no marginal basins before the opening. 3) Northeast Japan and Central Hokkaido are geologically continuous to West Hokkaido and Sakhalin, respectively. Each pair is treated as a single crustal block. The reconstruction gives consistent explanations for such geologic features as the change of volcanic front, distributions of Paleogene coal-bearing strata and Cretaceous to Paleogene subduction complex and felsic volcanic rocks, continuity of geotectonic units mainly consisting of the subduction complex, and tectonic lines. A most significant corollary in this reconstruction is that Central Hokkaido was adjoined to Northeast Japan.

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伊江島と伊是名島における二畳紀からジュラ紀にかけての層状赤色チャートについて4つのシークエンスを選びこれらのシークエンスが遠洋性の深海底で形成されたものであるかどうかを検討した. その結果, 伊江島タッチューの, 70m以上厚いシークエンスとして露出する, 三畳紀からジュラ紀の層状赤色チャートは本当の遠洋性の堆積相を示すことが解った. 他の3つのシークエンスは, 灰緑色の層状チャートが混じったりして, 本当の遠洋性の相を示さない. これらの4つのシークエンスから64個の岩石試料を採集して全岩及び炭酸塩部における化学分析を行った. タッチューの赤色チャートのシークエンスにおいては, 下方に行く程, Alをはじめ主要及び微量成分の金属元素濃度が高くなる傾向が見られ, 三畳紀からジュラ紀にかけて, プレートが南半球から赤道を通過することにより, 堆積したシークエンスであることを示す. 非石灰質部におけるFeとMg間の相関度や, 他の主要元素間における相関度から, 伊江島タッチューのシークエンスは遠洋性の深海底で堆積したものであることが解るが, 他の3つのシークエンスについては半遠洋性の深海底のものと判別された.

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A compilation is given of all the pole positions either calculated from or given in several paleomagnetic studies carried out so far on Mexican regions. These are compared with the paleomagnetic data from North America (N.A.). The results (Oligocene data) clearly show the presence of relative tectonic movements of the Western Cordillera. The data for Recent to Miocene age seem to be consistent with N.A. data except Pliocene pole positions for Baja California which is taken as an evidence of movement of Baja California relative to Mexico or North America. The Mesozoic pole positions are also considered to show the possibility of tectonic instability of Mexico relative to 'stable' North America. Practically no work has been done so far on older rocks (Pre-Mesozoic) of Mexico.

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The Heilongjiang Complex is mainly composed of high-P/T type metamorphic rocks of blueschists and pelitic schists, and is distributed along the western margin of the Jiamusi Massif in NE China. LA-ICP-MS U-Pb ages of detrital zircons in pelitic schist (LG1-3) from the Mudanjiang district give a weighted mean age of 250.6 ± 2.3 Ma (MSWD = 2.2). Pelitic schist from the Yilan district (09YL10-1) contains 193-348 Ma and 392-561 Ma detrital zircons, with minor amounts of 783-987 Ma zircons. The weighted mean ages of the youngest detrital zircon age group are 230.6 ± 3.5 Ma (MSWD = 1.2; LG1-3) and 199.1 ± 3.1 Ma (MSWD = 1.0; 09YL10-1), and these constrain the maximum depositional age of the protoliths of the Heilongjiang pelitic schists. Phengites from pelitic schists in the Yilan (422YQ-3) and Luobei districts (408HB-1) yielded ⁴⁰Ar/³⁹Ar plateau ages of 179.9 ± 0.8 Ma and 164.7 ± 0.2 Ma, respectively. A ⁴⁰Ar/³⁹Ar phengite age of 189.8 ± 0.8 Ma as total gas age (apparent age distribution from 183 Ma to 196 Ma) was also obtained for Yilan garnet-barroisite schist (423YJ-1). Reliable geochronological data suggest that a paleo-ocean located between the Jiamusi Massif and the Songnen Massif to the west was still present at least up to 199-231 Ma, and subduction-related high-P/T type metamorphism occurred during the at 145-184 Ma.

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The stratigraphy, geologic structure and ages of the Mesozoic strata exposed in the eastern part of the Kanto Mountains, central Japan, are discussed based on recent fossil findings. The formations trending WNW-ESE direction, are subdivided into the following six formations from north to south: the Kuroyama, Takahata, Kabasaka, Hanagiri, Nakato and Nitayama Formations. The Middle Kuroyama Formation is composed of chaotic rocks consisting of exotic blocks of Permian to Early chert, Carboniferous to Permian limestone and volcaniclastic rocks in a shaly matrix. The Takahata Formation consistsof Middle shale and volcaniclastic rocks with Permian limestone blocks. The Kabasaka Formation is characterized by a chert-clastic sequence, which is made up of Triassic to Early chert and overlying Middle shale. The Early Hanagiri Formation is composed of chaotic rocks consisting of exotic blocks of Permian to Early chert, Permian limestone and volcaniclastic rocks in a clastic matrix. The late Early Nakato Formation is composed mainly of chaotic rocks consisting of exotic blocks of Permian to Early chert in a shaly matrix. The Nitayama Formation is characterized by chaotic rocks comprising of Permian to Early chert and Permian limestone in a Middle shaly matrix. The first three formations are in contact with vertical or steeply southward-dipping faults. On the contrary, the latter three are in contact with northward-dipping reverse faults. The Koma Orbitolina Formation, which consists mainly of Early Cretaceous calcareous shale and sandstone unconformably overlies the Takahata Formation in the most eastern part of the studied area.
Based on stratigraphical and structural features and radiolarian dating, the Kuroyama, Takahata and Kabasaka Formations are correlative with the Northern Chichibu Belt (northern portion of the three folds Chichibu Belt) in the Outer Zone of Southwest Japan. The Kabasaka Formation is regarded as an accretionary wedge formed by offscrape-accretion mainly during Middle time. The Hanagiri, Nakato and Nitayama Formations correspond to the Middle Chichibu Belt and are presumed to be products of the convergent complex of an oceanic plate during Early to Middle times.

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Radiometric ages of detrital zircons in three samples of psammitic schists from the Sanbagawa Belt, Kanto Mountains, were obtained from the ²³⁸U/²⁰⁶Pb ratio and isotopic compositions of Pb using a Sensitive High Resolution Ion MicroProbe (SHRIMP II). Most of the zircon ages cluster around Cretaceous, with a few ages corresponding to older zircons. The origins of the detrital zircons are mainly Cretaceous igneous rocks. The ages of the youngest zircons in samples AM48p, SnbE, and AM29p indicate Late Cretaceous time, and they are 78.8 ± 1.3 Ma, 91.4 ± 1.4 Ma, and 95.3 ±1.5 Ma, respectively. The samples AM48p and AM29p have K-Ar ages of 65.9 ± 1.4 Ma and 82.1 ± 1.8 Ma, respectively. The age difference between the youngest detrital zircon age and white mica K-Ar age is 13 Myr. The Sanbagawa Belt is believed to be a metamorphosed phase of the Chichibu Belt, which is a Middle to earliest Cretaceous accretionary complex; however, the results of this study suggest that the protolith of the Sanbagawa belt was accreted in Late Cretaceous, similar to the Shimanto belt that runs parallel to the Sanbagawa and Chichibu belts.

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The Suo metamorphic complex in the Chugoku Mountains of southwest (SW) Japan represents

high pressure (P )/temperature (T ) type metamorphic rocks. Its high–grade part is exposed in the Nichinan area, where barroisite–bearing mafic schist occurs as ~ 50–m thick layers in pelitic schist. These mafic layers contain the common matrix assemblage barroisite + epidote + albite + quartz + titanite + phengite. Relic minerals (garnet, glaucophane, aegirine–augite, Si–rich phengite and rutile) of early–stage parageneses are preserved within albite porphyroblasts. The textural relations combined with pseudosection modeling suggest a clockwise P –T trajectory from epidote–blueschist facies through the garnet + clinopyroxene stable conditions to epidote–amphibolite facies. Two distinct phases of high–strain ductile deformation (D1 and D2) can be recognized in the area, and they are related to early and late stages of exhumation. Albite porphyroblasts initially grew statically between D1 and D2 at ~ 520–530 °C and ~ 0.8 GPa, and further retrogressive growth of albite rims and chlorite at the expense of barroisite is synchronous with D2. The lithological association, deformation structures and metamorphic conditions of the Suo metamorphic complex are very similar to those of the Cretaceous Sanbagawa metamorphic complex, suggesting they have comparable exhumation processes as coherent–type high–P/T metamorphic complexes.

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Ktenasite was found as a vein forming mineral in the altered shale of Tamba zone of age, at the Hirao mine, Minoo, Osaka, Japan. The mineral was also found in a marginal part of sphalerite in the host rock. This is the first occurrence of ktenasite in Japan. Ktenasite occurred as aggregates of flattened prismatic crystals up to 0.5 mm long and 0.1 mm wide, in association with minerals such as chalcopyrite, serpierite, smithsonite, hydrozincite, and limonite. An EPMA and CHNS/O analyzer gave the empirical formula (Cu_3.446Zn_1.451Co_0.080Pb_0.018Ni_0.007)_Σ5.002(SO₄)_2.003(OH)_5.998·5.99H₂O on the basis of O = 20. The unit cell parameters were a = 5.590(1), b = 6.161(1), c = 23.741(3) Å, and β = 95.628(3)°. The Vickers microhardness was 113 kg/mm² and Moh's hardness was 2.5. The density was 2.93 g/cm³. It is likely that ktenasite at Minoo was formed by a reaction of the Cu-bearing fluids with sphalerite.

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Multiple generations of Na–Ca and Na pyroxenes (aegirine–augite, aegirine and jadeite) were found in a metamorphosed monzonitic dike from a coherent mafic layer of the Northern Chichibu belt in central Shikoku, Japan. The mafic layer was derived from alkaline basalt magma and its derivatives, and belongs to the Kamiyoshida unit (Middle accretionary complex). The earliest–stage sodic pyroxene (jadeite–free Ti–rich aegirine–augite to aegirine) in the dike probably crystallized during a post–magmatic hydrothermal stage. Igneous Ti–rich augite phenocrysts were almost completely pseudomorphed by chlorite + phengite + Al–OH–rich titanite + sodic pyroxene (aegirine–augite with jadeite component) during early stages of subduction metamorphism. The earliest–stage sodic pyroxene and pseudomorphed Ti–rich augite were further overgrown by jadeite/aegirine fringes during high–P/T metamorphism. Jadeite/aegirine pyroxene also occurs as small (~ 50 µm long) neoblasts within pseudomorphs (albite + phengite + pumpellyite ± Ba–rich K–feldspar) after igneous plagioclase. Individual grains of the fringe/neoblastic pyroxene are zoned with a jadeite core (up to 98% jadeite content) and an aegirine rim (down to 25% jadeite content). Jadeite–rich pyroxene (up to 92% jadeite content) was also found in basaltic rock from the mafic layer. The absence of quartz and the alkaline affinity of the protoliths suggest that the jadeite formation can be explained by the reaction analcime = jadeite + H₂O. If H₂O fluid was present, the decrease in jadeite content in the fringe/neoblastic pyroxene implies decompression from ~ 0.6–0.7 GPa at 300 °C to ~ 0.4 GPa at 210–260 °C. The formation of the jadeite–to–aegirine pyroxene during exhumation probably resulted from the lowest–grade Sanbagawa metamorphism.

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紀伊半島四万十帯の白亜系寺杣層，古第三系音無川付加シーケンスの砂岩組成を検討した．寺杣層では後背地でのルーフィングに伴い，下部から上位へジルコンとザクロ石に富み，緑レン石·チタナイト·褐レン石を伴う長石質ワッケから，自形ジルコンに富む石質ワッケへと急変する．ザクロ石は下部では様々なタイプからなるが，上部では高圧型やグランダイトは急減し低圧型が増加する．一方，音無川付加シーケンスでは，アンルーフィングにより，下部から上部にむけて緑褐色普通角閃石を伴い自形ジルコンに富む石質ワッケから，緑レン石·チタナイト·褐レン石に富む長石質アレナイトへと変化する．ザクロ石組成は上位に向けて中圧型は減少，代わって低圧型が増加，最上部ではグランダイトが出現する．後背地におけるルーフィングやアンルーフィングは自形ジルコン，褐レン石，低圧型·高圧型やグランダイト型ザクロ石等の消長から推定することが可能である．

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忠南炭田の東部に分布する大同層群は, 下位から, 下鳥層, 峨嵋山層, 造渓里層, 白雲寺層, 聖住里層で構成される. 古生物学的研究は東アジアの中生代の Dictyophyllum-Clathropteris 植物区のうち, 南東亜区にあたる植物群構成を中心に行った. 峨嵋山層の地質時代は後期三畳紀であり, この時代は葉肢介類からも支持される. 上位の層は植物群からみて前期ジュラ紀までのびる.
堆積岩石学研究は砂岩の鉱物と重鉱物組成を中心に行った. トーマリンとガーネットは定量分析した. 下鳥層の礫は先カンブリア紀の変成岩から由来した岩片を55%含む. 砂岩の主要鉱物は石英で, 平均61.5%である. 長石は他の地域の大同層群より高い含有量で, 平均15%である. 下鳥層および峨嵋山層中部砂岩帯の一部の砂岩は石英アレナイトである. それ以外の層の砂岩は長石質アレナイト/ワッケからなる. 砂岩の重鉱物としてはジルコン, トーマリン, ルチル, モナズ石, 褐れん石, ガーネット, スフェーン, 角閃石類, 緑泥石, 黒雲母, 白雲母が有り, 非透明鉱物として赤鉄鉱, 磁鉄鉱, 黄銅鉱, チタン鉄鉱, クロム鉄鉱が含まれる. EPMAで定量分析したトーマリンはリチュームが少ない花崗岩類とアプライト, またはカルシウムが少ないメタペライトとメタザマイトに由来したものである. ガーネットは中間～高変成度のカルシウムが少ない変成岩に由来したものである. 礫岩と砂岩の鉱物と重鉱物組成の検討の結果, 大同層群の供給源は主として石英質岩石であって, それ以外に火成岩と変成岩が付加的である.

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Sedimentary and structural characteristics in two types of accretionary fold belts in central Japan are introduced and the tectonic significance are discussed. The Shimanto Fold Belt, grown up from the Cretaceous arc-trench gap and trench slope sediments, has the collisional features of large scale folds. The fold styles in the belt are differently developed in inner and outer parts. The former is characterized by a series of shear folds and the latter is by a series of lens folds. This difference may be caused chiefly by the different geothermal gradients of the area. The Miocene Miura Basin is influenced by lateral compression of strike slip field at the time of sedimentation. The development of the basin was related to the strike slip motion at the plate boundary between the Philippine Sea and Asian Plates.

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Several tens of float blocks of jadeite-quartz-K-feldspar rocks were recently found in and around serpentinite masses in the Kamuikotan Gorge area of the central Kamuikotan zone, Japan. They consist mainly of jadeite (Jd_95-100), quartz, K-feldspar, phengite, and lawsonite. Two stages of metamorphism are recognized. The metamorphic conditions during the first and the second stages are estimated at about 250-350 °C and more than 1.1 GPa, and 200-300 °C and 0.4-0.7 GPa, respectively. The rocks are relatively fine-grained, acidic in composition, and characteristically have many jadeitized pseudomorphs of probable rapakivi feldspar, suggesting a hypabyssal fine-grained granite or granite porphyry origin. K-feldspar-bearing granitic rocks have never been reported from the Kamuikotan zone. The discovery of jadeite-quartz-K-feldspar rocks in the zone provides important information about the source of the metamorphic protoliths. The inference is that these materials formed by the activity of felsic magma, which existed near the trench during Late to Cretaceous time.

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Extensive geological and geophysical evidence suggests that numerous fragments of continents, miniplates, and so called "island arcs" have been incorporated into the Circum Pacific continents. The old rocks exposed on these bodies bear strong evidence for continental origins. This leads to the speculation that a large continental mass existed once in what is now the Pacific Ocean. This mass-which we call the Pacifica continent-could have been part of the Pangea Super Continent, adjacent to Australia and Antarctica. When this continent broke into fragments, they drifted toward continental collision in South America, North America, Alaska, Kamchatka, Japan and East Asia. Submerged platforms in the Pacific Ocean, such as the Ontong Java area, the Shatsky rise, and the Manihiki plateau, may also be remnants of Pacifica. The thick crusts of these plateaus, with velocities typical of continents, are thus predicted to be continental crusts.
Although the details of the breakup and collision of Pacifica cannot be resolved very well at present, the postulated existence of this continent supports a large generalization: We suggest that all spreading centers on earth may originate underneath continental masses. Without Pacifica of course, the present day east Pacific rise is without associated continents. If continents account for all spreading, it may be because the continental crust acts as thermal blanket, warming the lower lithosphere and upper asthenosphere.
Adding to this the further hypothesis and that subducted ridges are responsible for back arc rifting and spreading, we obtain the typical trench-continent-ridge sequences, containing volcanism, uplifted blocks, metamorphism, and rifting. Multiple collisions involving several continental slivers and ridges may result in several consecutive sequences juxtaposed on one another. Such complexities with geological record are common in belts such as Western North America.
On the basis of the similarities of (a) the geophysical aspects-seismicity and crustal thickness, (b) morphology, and (c) geological complexities, we propose in this paper that the circum Pacific mountain belts may be at least in part the result of past continental collisions, quite similar to those associated with the Alpine belts.
The notion of Pacifica and its breakup may provide an explanation for the similarities of flora, fauna, and rock sequences in widely separated locations in the mountain belts across the Pacific, and may tie in divergent paleomagnetic data.

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Geodynamics and tectonic evolution of the North-Eastern Asia was determined by the establishment of those structural elements in the geological sections which are typical of the modern active continental margins.
The Neogene island arcs on the majority of their strike coincide with the modern ones (the Kuril-Kamchatka) but locally they are broken up (the Western Sakhalin). They are conjugated with the back, front and interarc troughs. The Paleogene island arc occurs, probably, in the northwestern Kamchatka and on the Academy of Sciences uplift in the Sea of Okhotsk. The Early Mesozoic Uda-Murgal island arc marks the southeastern boundary of the ancient Eastern Siberia megablock. Along its southern and northern boundaries the island arc complexes of the same age are distinguished. Position of Eugeosynclinal zones on the outer side of the island arcs indicates the isolation of the Eastern Siberia megablock from the Bureya-Ehanka, Okhotomorskiy and Chukotka ones the basement of which is composed by the Early Precambrian metamorphic complexes of sialic composition and granitoids. Tectonic movements at the end of Neocomian are expressed in the formation of the Andian type active continental margin with the Okhotsk-Chukotka margin-continental volcanic belt originated on a site of the Uda-Murgal island arc. This process was accompanied by the geometrical changes of the Benioff zone determined by the analysis of K₂O content in volcanites on the base of Dickinson and Hatherton's diagrams -the angle of dip became more gentle, the width along the dip and depth of the magma active part of the Benioff zone were increased. Simultaneously with the development of the Okhotsk-Chukotka volcanic belt there was formed the island arc on the East of the Sikhote-Alin. Owing to the Pre-Senonian movements on a site of this arc the Eastern Sikhote-Alin margin-continental volcanic belt similar to the Okhotsk-Chukotka one originated.
Many of the island arcs and margin-continental volcanic belts occur along the margins of the ancient sialic megablocks. Paleotectonic reconstructions prove the fact that there were significant horizontal displacements of the sialic megablocks causing the crash of the oceanic basins situated between them. The enlargement of the eastern part of the Asian continent took place not only at the expense of the island arcs displacement towards the ocean, but also due to the sialic blocks joining.
Geodynamics and tectonic evolution of the continental margin is revealed by the determination of those structural elements in the geological sections which are typical of the modern and Late Cenozoic geosynclinal systems (island arcs). The most significant attention is paid to the tectonic position and nature of volcanic belts of different types and ages widely distributed in the North East of Asia. They help to reconstruct the former plate boundaries and to determine the kinematics of their movements accroding to the plate tectonics models. Among them we distinguish: (1) the inner island arcs or volcanic geanticlines, (2) margin-continental volcanic belts, (3) plateau-basalts coinciding with the margin-continental belts in the space but being the independent formations.

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