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1.
Doklady Earth Sciences - The U–Pb and Lu–Hf isotope studies of detrital zircons from Mesozoic metasedimentary rocks of the Sorukan and Naldinda formations of the Ul’ban terrane... 相似文献
2.
New age data on the magmatic rocks from the western sector of the Okhotsk-Chukotka volcanogenic belt
New age data are reported for the magmatic rocks from the western flank of the Okhotsk-Chukotka volcanogenic belt consisting of the Ul’ya and Kuidusun volcanic zones. Four U-Pb SHRIMP zircon dates within 106-90 Ma were obtained for the upper part of the Emanrin Formation and the lower part of the Ul’ya Group of the Ul’ya volcanic zone. Large Verkhneallakh and Atarbai subvolcanic intrusions from the Kuidusun volcanic zone were dated using the Rb-Sr method at 115–107 Ma and 85 Ma, respectively. U-Pb dating of zircon microsamples from adamellites and diorites of the Sizindzha Massif yielded, respectively, ages of 91 and 90 Ma. New geochronological data indicate that the Selitkan-Sungari and Okhotsk-Chukotka volcanogenic belts are coeval and can be united in a common Okhotsk-Sungari system of volcanic belts and zones (megabelt). 相似文献
3.
Tore Torske 《International Journal of Earth Sciences》1982,71(1):104-119
An isolated synclinorium, comprising the up to 5 km thick Ullensvang Group of metavolcanic and metasedimentary rocks, is surrounded by granitoid plutons and has no recognizable older basement. From an earlier interpretation based on regional data this area is inferred to be part of a Proterozoic, cordilleran-type volcanic-plutonic belt. Major structures in the synclinorium are interpreted to have evolved as follows: 1) Early folds were produced by regional compression; 2) within a part of the synclinorium, such folds were tightened and reoriented during a subsequent deformation phase caused by forceful emplacement of the Kvinnherad batholith, flanking the synclinorium to the southwest; 3) this deformation was accompanied by thrust faulting towards the northeast, away from the batholith; 4) forceful emplacement of plutons belonging to the Eidfjord-Kinsarvik batholith, on the northeastern flank of the synclinorium, produced southwest-vergent overfolding of the earlier structures in the synclinorium. In addition, local deformation around a pluton intruding the northern part of the synclinorium near Utne produced areally restricted deformation structures, approximately corresponding in time with the second deformation event (2) above. Structures in plutonics rocks of the batholiths are interpreted in terms of an emplacement model involving distension diapirism. The deformation zones associated with diapiric plutons in this area appear to be more similar to some of those reported from Archaean greenstone belts than to those found in volcanic-plutonic belts of younger cordilleran-type orogens. 相似文献
4.
S. O. Zorina 《Stratigraphy and Geological Correlation》2007,15(3):267-276
The work is aimed at litho-, bio- and magnetostratigraphic subdivision of the Middle-Upper Jurassic sedimentary succession in the northeast of the Ul’yanovsk-Saratov depression (the East Russian plate). Problems of regional and interregional correlation of distinguished subdivisions are considered. As is shown, the ammonite biostratigraphy is most effective method for solving problems of chronostratigraphy. 相似文献
5.
The western Blue Ridge allochthon of the southern Appalachians is dominated by the >180 km-long Murphy synclinorium, paired with anticlinoria to the northwest. These are first generation, northwest overturned, doubly plunging, large amplitude and wavelength (>10 km) isoclinal folds contemporaneous with peak Neo-Acadian orogeny (Visian, ∼335–345 Ma) regional metamorphism. The synclinorium folds a regional unconformity separating Neoproterozoic rift and lower Paleozoic drift sequences from a younger successor-basin sequence. Strain analysis of metaconglomerates from lithologic groups above and below the unconformity indicates coaxial, low to moderate, oblate to nearly plane strain in both groups. The synclinorium evolved via NNW-SSE-crustal shortening (∼32%), combined with orthogonal NNE-SSW-sub-horizontal flow (stretching) (∼35–45%) sub-parallel to the developing fold axes. Differences in metamorphic grade and paleodepth (∼10–17 km) of the exposed synclinorium had essentially no effect on strain magnitudes. Retrodeformation of the embedded regional unconformity reveals a very broad synclinal warping of the rift and drift-facies units predating superposition of the Murphy synclinorium, suggesting tectonic inheritance in the latter structure's origin. The earlier mild deformation is post-Early Cambrian and may represent the only vestige of the dynamic effects of the Middle Ordovician Taconic orogeny to be found in this region. 相似文献
6.
海南石碌铁矿床构造变形特征及其与铁多金属成矿富集的关系 总被引：1，自引：0，他引：1
海南石碌铁矿曾被誉为“亚洲最大的富铁矿”,其形成、定位与褶皱变形及伴随的剪切、塑性流动等构造密切相关。石碌矿区构造变形大致分为早期(D1)复式向斜的形成时期、晚期(D2)褶皱叠加和剪切变形时期。后者又进一步分为韧-脆性变形(D2a),脆-韧性变形、层间滑脱断层形成(D2b)和脆性变形、矿体破坏(D2c)3个阶段。石碌铁矿床受NW—SE向复式向斜及其与NE—NNE向褶皱叠加所形成的横跨或斜跨褶皱的严格控制;褶皱过程所伴随的剪切变形和高温塑性流动是富铁矿形成的重要机制。复式向斜轴部,尤其是2期向斜褶皱轴的叠加部位往往可发现厚大的富铁矿体。 相似文献
7.
冀北辽西地区的盖层可分两个构造层，由燕辽复向斜和秦皇岛背形相互叠加，并相应发育两期推覆构造。复向斜范围包括内蒙古地轴和燕辽沉降带，是由长条形的3个背斜和2个向斜相间，及配套的EW向纵断裂、SN向横断裂和NE向、NW向的共扼断裂组成。著名的尚义一宽城一凌源一朝阳一北票断裂是复向斜及其次级背斜的轴部纵断裂，以南大岭组、窑坡组和北票组作为其裂隙充填物。燕山EW向断裂南北对冲现象是复向斜纵断裂放射状排列并向核部推覆的反映。秦皇岛背形以秦皇岛一凌源断裂为轴面，由复向斜的轴面褶皱而成，背形转折端在秦皇岛，呈相对上翘。本区NE向、NNE向断裂的叠加在区域上有不同的表现：冀北段NE向、NNE向褶皱叠加的结果使燕山段复向斜成为短轴褶皱样式，平面团呈NW向排列，符合Ramsay第一类褶皱干涉样式的第二种类型。复向斜的形成机制完全符合纵弯褶皱作用下岩石的变形原理，是西伯利亚板块和华北板块碰撞的结果；秦皇岛背形的形成是后期太平洋板块俯冲在欧亚板块之下所致。 相似文献
8.
燕山辽西地区的盖层可分两个构造层,由燕辽复向斜和秦皇岛背形相互叠加,并相应发育两期推覆构造。复向斜范围包括内蒙地轴和燕山沉降带,是由长条形的三个背斜和二个向斜相间,及配套的EW向纵断裂、SN向横断裂和NE向、NW向的共轭断裂组成。著名的尚义-宽城-凌源-朝阳-北票断裂是复向斜及其次级背斜的轴部纵断裂,以南大岭组、窑坡组和北票组作为其裂隙充填物。燕山EW向断裂南北对冲现象是复向斜纵断裂放射状排列并向核部推覆的反映。复向斜的形成机制完全符合纵弯褶皱作用下岩石的变形原理,是西伯利亚板块和华北板块碰撞的结果;秦皇岛背形的形成是后期太平洋板块俯冲在欧亚板块之下所致。 相似文献
9.
R. R. Gabdullin E. N. Samarin A. V. Ivanov N. V. Badulina V. I. Kiselev A. Yu. Yurchenko T. I. Nigmadzhanov 《Moscow University Geology Bulletin》2016,71(6):395-406
The results of a complex study of the Upper Cretaceous carbonate section in the quarry of the cement plant of the town of Sengilei (Ul’yanovsk district) are presented. The Lower Paleocene cyclic opoka member is described. The formation conditions of the Upper Cretaceous cyclic and cryptocyclic, as well as Lower Paleocene cyclic, rocks are interpreted for the first time on the basis of lithological, petrographic, petromagnetic, geochemical, and paleoecological methods. The cyclicity was formed due to dilution cycles under climate fluctuation and eustatic variations, which were caused by eccentricity cycles of the Earth’s orbit. These cycles are identified in the cryptorhythmic lanceolata sequence of the Lower Maastrichtian rocks. 相似文献
10.
The lithogeochemical distribution patterns of Mg, Sr, Na, Zn, Pb, Fe, Mn, K, Corg (organic matter) and IR (insoluble residue) in the Dinantian limestones and dolomites from the eastern part of Belgium have been studied (Dinant and Verviers synclinorium). Comparison of geochemical data of non-mineralized strata revealed higher background values in the strata of the Verviers synclinorium where Pb-Zn mineralizations occur. In this area a relation may exist with the metallogenetic district (Herve-Vesdre-Theux district; proposed by Dejonghe 1985b). However, the higher background values also could relate to the more restricted sedimentation conditions in the Verviers synclinorium as opposed to the more open marine conditions in the Dinant synclinorium. The influence of mineralization on the geochemistry of limestones is limited and unpredictable. In dolomites, however, the effect can be important. In these rocks, the lithogeochemical distribution of Zn, Pb and Mn can be subdivided into three populations, i.e. a regional background, a local high background and a halo population. The higher trace element concentrations in the halo population is caused by the existence of disseminated sulfide minerals (sphalerite, galena and pyrite) and Zn-bearing goethite (mainly pseudomorphs after pyrite) and Mn-oxides. The sulfides relate to the ore emplacement. In the local high background only the Zn-bearing oxides occur. Their presence and thus the development of the local high background relates to weathering processes. 相似文献
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12.
E. F. Letnikova I. A. Vishnevskaya F. A. Letnikov N. I. Vetrova S. I. Shkolnik Yu. A. Kostitsyn E. A. Karakovskii L. Z. Reznitskii N. A. Kanygina 《Doklady Earth Sciences》2016,470(2):1071-1075
The geochemical and Sm–Nd isotope characteristics of Late Precambrian and Early Cambrian sandstones previously related to the sedimentary cover of the Dzabkhan continental block are reported. It is established that the Riphean and Vendian sedimentary rocks of the Ul’zitgol’skaya and Tsaganolomskaya Formations were accumulated within the Dzabkhan continental block as a result of recycling of the terrigenous deposits formed at the expense of destruction of basement rocks and younger granite. The formation of terrigenous rocks of the Bayangol’skaya Formation after a gap in sedimentation occurred in the sedimentary basin, where only the Late Riphean formations of the juvenile crust, probably of the Dzabkhan–Mandal block were the sources, without the contribution of the ancient crustal material. The Tsaganolomskaya and Bayangol’skaya Formations were formed in different sedimentary basins and cannot be related to the same complex. 相似文献
13.
本文中,笔者对燕辽地区的构造形迹进行了重新厘定,并将其划分成不同构造阶段的产物,提出了一些新的认识:燕辽地区范围包括"内蒙地轴"和燕山沉降带,其构造格局主要由燕辽向斜、燕辽复向斜和秦皇岛背形及其配套断裂组成,在这三个区域构造样式之下又发育次一级的褶皱构造及其配套断裂,并且后期构造对前期构造改造、叠加和利用,致使出现复杂的构造格局.海西一印支期形成了燕辽向斜及其配套断裂,"内蒙地轴"是燕辽向斜的北翼.燕辽沉降带是燕辽向斜的南翼.早中侏罗世进一步褶皱成复向斜,"内蒙地轴"南缘断裂是复向斜的轴部纵断裂并充填了上侏罗统作为裂隙充填物.中晚侏罗世开始,以秦皇岛-凌源断裂为轴面褶皱成一个背形.秦皇岛-凌源断裂的存在及其对燕山段和辽西段的影响致使燕山段和辽西段具有不同的地表出露形态. 相似文献
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15.
详细描述了北羌塘乌兰乌拉湖地区白垩纪地层剖面，将区内白垩系划分为错居日组和桑恰山组。沉积相分析表明，乌兰乌拉湖地区错居日组主要为冲积扇至河流相沉积，岩性及厚度变化较大，而桑恰山组为湖泊、湖三角洲至河流相沉积。初步认为错居日组为早日垩世地层，桑恰山组为早白垩世晚期至晚白垩世地层。 相似文献
16.
The Lackawanna synclinorium of Pennsylvania contains abundant coal that was altered to anthracite rank during the Late Paleozoic Alleghanian orogeny. Why did the coal in the synclinorium undergo anthracitization? Two alternatives have been suggested. (1) The region was buried deeply during and/or after the Alleghanian orogeny and thus became hot in response to Earth's geothermal gradient; and (2) hot fluids migrating from the orogen toward the foreland carried heat into the coal and caused anthracitization. If the second hypothesis is correct, the region should contain evidence that hot fluids passed through the coal. Field observations, illite-crystallinity studies and fluid-inclusion analyses indicate that the coal-bearing Pottsville and Llewellyn Formations, and an underlying detachment fault, called the Pottchunk fault (at or slightly below the base of the Pottsville Formation), acted as a regional aquifer for the migration of hot fluids during the Alleghanian orogeny. The presence of quartz veins and the hydrothermal minerals tosudite and pyrophyllite in strata above the Pottchunk fault, and the apparent absence of an illite-crystallinity burial gradient in the underlying strata, suggest that fluids migrated through large pores in coarse-grained sandstones, through abundant fractures that developed in response to Alleghanian deformation, and along the Pottchunk fault. The quartz veins, tosudite and pyrophyllite mineralization do not occur below the Pottchunk fault (except at one locality), suggesting that fluid flow was greater above the fault, perhaps because fracturing accompanying deformation increased permeability of the fault's hanging wall. Fluid inclusions in the Pottsville and Llewellyn Formations indicate fluids achieved a minimum temperature of 270 °C at a depth of 3.1–8.5 km. Heat-flow calculations constrained by fluid-inclusion data show the heat carried by the migrating fluids through the coal-bearing strata was sufficient to elevate the rock temperature to anthracite-grade conditions (250 °C), assuming that the fluid event lasted about 1 year. Thus, deep burial (6–9 km) of the coal-bearing strata in the Lackawanna synclinorium was not required for anthracitization. Anthracitization was likely the result of stratigraphically controlled hot fluid migration through the coal-bearing strata at shallow depths (≤5 km). 相似文献
17.
通过对后山测区地质条件及物化探异常分析,并与著名的铜矿峪铜矿床进行对比,认为位于复向斜北西倒转翼的后山测区与南东正常翼的铜矿峪铜矿具有相似的成矿地质、构造条件和相同的物化探异常特征。根据铜矿峪主要矿体的赋存状态,对后山测区铜的成矿远景进行了预测。 相似文献
18.
Anisotropy of magnetic susceptibility (AMS) data are used as a tool to determine strain variations in different parts of the Banded Iron Formations (BIFs) of the Bonai Synclinorium, eastern India. AMS data of 88 cylindrical cores drilled from 29 samples collected from the limb and hinge parts of mesoscopic scale folds as well as different parts of the entire synclinorium are presented. It is found that the samples from limbs of small-scale folds and also from limbs of the regional scale synclinorium have higher degrees of anisotropy than the hinges. This is inferred to indicate that the limbs accommodated higher strain than the hinges. AMS orientation data are analysed in conjunction with field data. It is concluded that the magnetic fabric developed in the limbs as well as hinges of the BIFs of the study area is related to deformation and is not a manifestation of sedimentary fabric. 相似文献
19.
A. V. Kochergin 《Lithology and Mineral Resources》2009,44(6):579-586
Data on the phosphorite mineralization, lithology, and variability of Lower Paleozoic rocks in the Zilair synclinorium and
Yuryuzan basin are given. Comparison of Lower Paleozoic rocks with type sections of phosphate-bearing rocks in the world suggested
their compliance with the phosphorite-enclosing rocks of the fine-grained phosphorite association. Analysis of the facies
variability of rocks indicate the possibility of discovery of large phosphorite deposits in the Yuryuzan and Syuren subzones
of the Western structural-facies zone. Phosphorite deposits are unknown in the synclinorium because of their instability during
hypergenesis and burial under allochthonous loose sediments of the Cenozoic. 相似文献
20.
Liu Qingsheng Department of Geophysics China University of Geosciences Wuhan The State Key Laboratory of Oil/Gas Reservoir Geology Exploitation of China Institute of Chengdu Technology Chengdu Wu Qifan Li Haixia Department o 《中国地质大学学报(英文版)》2001,12(2)
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