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Paleogeographic maps of the Japanese Islands: Plate tectonic synthesis from 750 Ma to the present 总被引：73，自引：1，他引：73
Abstract A series of paleogeographic maps of the Japanese Islands, from their birth at ca 750–700 Ma to the present, is newly compiled from the viewpoint of plate tectonics. This series consists of 20 maps that cover all of the major events in the geotectonic evolution of Japan. These include the birth of Japan at the rifted continental margin of the Yangtze craton ( ca 750-700 Ma), the tectonic inversion of the continental margin from passive to active ( ca 500 Ma), the Paleozoic accretionary growth incorporating fragments from seamounts and oceanic plateaux ( ca 480-250 Ma), the collision between Sino-Korea and Yangtze (250–210 Ma), the Mesozoic to Cenozoic accretionary growth (210 Ma-present) including the formation of the Cretaceous paired metamorphic belts (90 Ma), and the Miocene back-arc opening of the Japan Sea that separated Japan as an island arc (25-15 Ma). 相似文献
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Tsutomu Ota Masaru Terabayashi Christopher D. Parkinson and Hideki Masago 《Island Arc》2000,9(3):328-357
Abstract To investigate the regional thermobaric structure of the diamondiferous Kokchetav ultrahigh‐pressure and high‐pressure (UHP–HP) massif and adjacent units, eclogite and other metabasites in the Kulet and Saldat–Kol regions, northern Kazakhstan, were examined. The UHP–HP massif is subdivided into four units, bounded by subhorizontal faults. Unit I is situated at the lowest level of the massif and consists of garnet–amphibolite and acidic gneiss with minor pelitic schist and orthogneiss. Unit II, which structurally overlies Unit I, is composed mainly of pelitic schist and gneiss, and whiteschist locally with abundant eclogite blocks. The primary minerals observed in Kulet and Saldat–Kol eclogites are omphacite, sodic augite, garnet, quartz, rutile and minor barroisite, hornblende, zoisite, clinozoisite and phengite. Rare kyanite occurs as inclusions in garnet. Coesite inclusions occur in garnet porphyroblasts in whiteschist from Kulet, which are closely associated with eclogite masses. Unit III consists of alternating orthogneiss and amphibolite with local eclogite masses. The structurally highest unit, Unit IV, is composed of quartzitic schist with minor pelitic, calcareous, and basic schist intercalations. Mineral assemblages and compositions, and occurrences of polymorphs of SiO2 (quartz or coesite) in metabasites and associated rocks in the Kulet and Saldat–Kol regions indicate that the metamorphic grades correspond to epidote–amphibolite, through high‐pressure amphibolite and quartz–eclogite, to coesite–eclogite facies conditions. Based on estimations by several geothermobarometers, eclogite from Unit II yielded the highest peak pressure and temperature conditions in the UHP–HP massif, with metamorphic pressure and temperature decreasing towards the upper and lower structural units. The observed thermobaric structure is subhorizontal. The UHP–HP massif is overlain by a weakly metamorphosed unit to the north and is underlain by the low‐pressure Daulet Suite to the south; boundaries are subhorizontal faults. There is a distinct pressure gap across these boundaries. These suggest that the highest grade unit, Unit II, has been selectively extruded from the greatest depths within the UHP–HP unit during the exhumation process, and that all of the UHP–HP unit has been tectonically intruded and juxtaposed into the adjacent lower grade units at shallower depths of about 10 km. 相似文献
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The ultrasonic technique for measuring travel times of compressional and shear waves using dual-mode transducers was adapted to a piston cylinder apparatus, allowing simultaneous measurements of travel times of compressional and shear waves of island arc samples under the high pressure and temperature conditions of island arcs. This method enables us to determine elastic properties and their pressure and temperature derivatives simultaneously. Furthermore, Vp/Vs can be directly determined from travel times of compressional and shear waves independently of length change due to compression or thermal expansion of rock samples under deep crustal conditions, providing more accurate Vp/Vs values than those determined from individual measurements of travel times of both elastic wave types using single-mode transducers. Experimental techniques and results are demonstrated using data on silicified pelitic schist from the Ryoke Belt to 0.6 GPa. The simultaneous measurement gives Vp = 5.60 km/s, ∂ Vp /∂ P = 0.090 (km/s)/GPa, Vs = 3.37 km/s, ∂ Vs /∂ P = 0.05 (km/s)/GPa, σ = 0.216, and Vp / Vs = 1.66 at ambient conditions. The temperature derivatives were constrained from fitting using linear functions of temperature, yielding ∂ Vp /∂ T = −0.518 × 10−3 (km/s)/K and ∂ Vs /∂ T = −0.182 × 10−3 (km/s)/K. Performing simultaneous measurements of travel times of compressional and shear waves using dual-mode transducers, it is possible to accurately determine Vp / Vs and Poisson's ratio of crustal minerals and rocks at deep crustal conditions to study the composition of the crustal interior, e.g. rock types and fluids below the hypocentral region of earthquakes or around bright spots. 相似文献
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We propose that competent layers composed of silicified rocks in the Cretaceous Ryoke low-pressure/temperature (low- P/T ) metamorphic belt in the Iwakuni–Yanai area, Southwest Japan, may be an exhumed equivalent of a seismically-reflective bright-layer in the middle crust. Silicified rocks crop out as layers or long lenticular bodies several to fifteen meters in thickness, and they are restricted to the area of greenschist facies conditions within a structural thickness of about one kilometer. The silicified rock layers exhibit a sharp contact with subjacent biotite schist but a gradational contact with overlying pelitic schist. Silicified rock is mainly composed of fine-grained quartz and minor muscovite and biotite, and some colored minerals have been variably decolorized by alteration. This implies that silicification turned the color of pelitic schists to pale gray or milky white. Quartz veins cutting schistosity at high angles were preferentially developed in the silicified rocks, while schistosity-parallel quartz veins, which underwent viscous flow, were observed in the underlying biotite schists. En echelon quartz veins and fishnet-like quartz veins are characteristic of silicified rocks. The modes of occurrence of quartz veins indicate that silicified rocks were competent relative to underlying biotite schist. The combination of contact with high-competence contrast adjacent to low-permeability silicified rocks may be a good reflector of seismic waves. If the silicified rocks were distributed in the middle crust to a considerable extent, they may result in seismic bright-layer reflections. 相似文献
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Hiroshi Yamamoto Natsumi Nakamori Masaru Terabayashi Hafiz Ur Rehman Masahiro Ishikawa Yoshiyuki Kaneko Takashi Matsui 《Island Arc》2010,19(3):458-469
Geological observations in the Horoman area, south‐central Hokkaido, show that the Horoman peridotite complex of the Hidaka metamorphic belt is a tectonic slice about 1200 m thick. The peridotite slab is intercalated into a gently east‐dipping structure. The underlying unit is a Cretaceous–Paleogene accretionary complex. Riedel shear planes in the sedimentary layers of the accretionary complex near the structural bottom of the peridotite slab indicate top‐to‐the‐west (thrust) displacement. The overlying unit is composed of felsic–pelitic gneisses and mafic–felsic intrusive rocks (the Hidaka metamorphic rocks). The boundary surface between the peridotite complex and metamorphic rocks forms a domal structure. Microstructures of sheared metamorphic rocks near the structural top of the peridotite slab indicate top‐to‐the‐east (normal) displacement. The results combined with previous studies suggest that the Horoman peridotite complex was emplaced onto the Asian margin (Northeast Japan) during the collision between the Asian margin and the Hidaka crustal block. 相似文献
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Hiroshi Yamamoto Kazuaki Okamoto Yoshiyuki Kaneko Masaru Terabayashi 《Tectonophysics》2004,387(1-4):151-168
Several mafic rock masses, which have experienced eclogite facies metamorphism, are distributed in flat-lying non-eclogitic schists in an intermediate structural level (thermal core) of the Sanbagawa belt. The largest, Iratsu mass, and an associated peridotite, the Higashi-Akaishi mass, extend E–W for about 8 km, and N–S for about 3 km, and are surrounded by pelitic, basic and quartz schists. The Iratsu mass consists of metabasites of gabbroic and basaltic origin, with intercalations of ultramafic rocks, felsic gneiss, quartz schist and metacarbonate. The Iratsu mass can be divided into two layers along a WNW-trending metacarbonate layer. The Higashi-Akaishi mass consists of peridotite with intercalations of garnet clinopyroxenite. It is situated beneath the western half of the Iratsu mass, and their mutual boundary dips gently or steeply to the N or NE. These masses underwent eclogite, and subsequent epidote-amphibolite facies metamorphism as has been reported elsewhere. The Iratsu–Higashi-Akaishi masses and the surrounding rocks underwent ductile deformation under epidote-amphibolite facies (or lower P–T) metamorphic conditions. Their foliation generally trends WNW and dips moderately to the NNE, and the mineral lineation mostly plunges to the N and NE. In non-eclogitic schists surrounding the Iratsu–Higashi-Akaishi masses, the foliation generally trends WNW and dips gently or steeply to the N or S and the mineral lineation mostly plunges to the NW, N and NE. Kinematic analysis of deformation structures in outcrops and oriented samples has been performed to determine shear senses. Consistent top-to-the-north, normal fault displacements are observed in peridotite layers of the Higashi-Akaishi mass and eclogite-bearing epidote amphibolite layers of the Iratsu mass. Top-to-the-northeast or top-to-the-northwest displacements also occur in non-eclogitic pelitic–quartz schists on the northern side of the Iratsu mass. In the structural bottom of the Iratsu–Higashi-Akaishi masses and to the south, reverse fault (top-to-the-south) movements are recognized in serpentinized peridotite and non-eclogitic schists. These observations provide the following constraints on the kinematics of the rock masses: (1) northward normal displacement of Iratsu relative to Higashi-Akaishi, (2) northward normal displacement of non-eclogitic schists on the north of the Iratsu mass and (3) southward thrusting of the Iratsu–Higashi-Akaishi masses upon non-eclogitic schists in the south. The exhumation process of the Iratsu–Higashi-Akaishi masses can be explained by their southward extrusion. 相似文献
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Masaru Terabayashi 《Contributions to Mineralogy and Petrology》1988,100(3):268-280
The 6km-thick Karmutsen metabasites, exposed over much of Vancouver Island, were thermally metamorphosed by intrusions of Jurassic granodiorite and granite. Observation of about 800 thin sections shows that the metabasites provide a complete succession of mineral assemblages ranging from the zeolite to pyroxene hornfels facies around the intrusion. The reaction leading to the appearance of actinolite, which is the facies boundary between prehnite-pumpellyite and prehnite-actinolite facies, was examined using calcite-free Karmutsen metabasites collected from the route along the Elk river. In the prehnite-pumpellyite facies, X
Fe3+[Fe3+/(Fe3++Al)] in prehnite, pumpellyite and epidote buffered by the four-phase assemblage prehnite+pumpellyite+epidote+chlorite systematically decreases with increasing metamorphic grade. Such a trend is the reverse of that proposed by Cho et al. (1986); this may be related to the higher
in the Mt. Menzies area. The actinolite-forming reaction depends on the value of X
Fe3+ in pumpellyite. If using a low value of Fe3+, 3.89 Pr(0.06)+0.48 Ep(0.26)+0.60 Chl+H2O=2.10 Pm (0.08)+0.17 Act+0.88 Qz is delineated. The number in parentheses stands for the X
Fe3+value in Ca-Al silicates. On the other hand, replacing the X
Fe3+ of 0.08 in pumpellyite with a higher X
Fe3+ value (0.24) changes the reaction to 0.41 Pm+0.02 Chl+0.42 Qz=0.11 Pr+0.62 Ep+0.10 Act+H2O. The first (hydration) reaction forms pumpellyite and actinolite on the high-temperature side, whereas the second (dehydration) reaction consumes pumpellyite to form prehnite, epidote and actinolite. The former reaction seems to explain the textural relationship of Ca-Al silicates in the study area. However, actinolite-forming reaction changes to a different reaction depending on the compositions of the participating minerals, although in the other area even physical conditions may be similar to those in the study area. Chemographic analysis of phase relations in the PrA facies indicates that the appearance of prehnite depends strongly on the bulk FeO/MgO ratio: this may explain the rarity of prehnite in common metabasites in spite of the expected dominant occurrence in the conventional pseudo-quaternary (Ca-Al-Fe3+-FM) system. An increasing FeO/MgO ratio stabilizes the Pr+Act assemblage and reduces the stability of the Pm+Act one. Therefore, the definition of pumpellyite-actinolite facies should include not only Pm+Act but also the absence of Pr+Act assemblages. In addition to the possible role of high
(Cho and Liou 1987) and/or high
to mask the appearance of prehnite, the effect of the FeO/MgO ratio is emphasized. 相似文献
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Y. Kaneko S. Maruyama M. Terabayashi H. Yamamoto M. Ishikawa R. Anma † C. D. Parkinson T. Ota Y. Nakajima I. Katayama J. Yamamoto and K. Yamauchi 《Island Arc》2000,9(3):264-283
Abstract Ultrahigh-pressure metamorphic (UHPM) rocks of the Kokchetav Massif of Kazakhstan contain metamorphic microdiamond and coesite inclusions inside rigid capsules such as garnet and zircon. Precambrian protoliths of the UHPM rocks were metamorphosed at around 530 Ma, at pressures of about 7 GPa, which suggests that crustal protoliths were subducted to depths of over 200 km. Primary UHPM minerals are poorly preserved due to partial obliteration by subsequent Barrovian overprint during exhumation and later collision events in Caledonian times. We report the results of detailed mapping of the Kokchetav Massif and use structural data to propose intrusion and exhumation mechanisms for the UHPM rocks. Detailed mapping revealed that many subvertical structures in the ultrahigh-pressure–high-pressure (UHP–HP) units were formed due to later folding. The primary structure appears to be subhorizontal and the total thickness of the UHP rocks is estimated at around 2 km. The first order structure is sandwich-like; that is, the UHP–HP units are separated from underlying low-P metamorphic rocks of the Daulet Series and from feebly metamorphosed to unmetamorphosed sedimentary strata on the top by subhorizontal faults. Kinematic indicators show top-to-the-south sense of shear along the top, and top-to-the-north displacement along the bottom boundaries. These shear senses, together with the observed metamorphic gradients, suggest that the thin UHPM sheet was extruded toward the north. We consider wedge extrusion to have been the most effective mechanism for the exhumation of the UHPM rocks. 相似文献