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1.
Kamil Ustaszewski Stefan M. Schmid Bernhard Fügenschuh Matthias Tischler Eduard Kissling Wim Spakman 《Swiss Journal of Geoscience》2008,101(1):273-294
A map-view palinspastic restoration of tectonic units in the Alps, Carpathians and Dinarides reveals the plate tectonic configuration before the onset of Miocene to recent deformations. Estimates of shortening and extension from the entire orogenic system allow for a semi-quantitative restoration of translations and rotations of tectonic units during the last 20 Ma. Our restoration yielded the following results: (1) The Balaton Fault and its eastern extension along the northern margin of the Mid-Hungarian Fault Zone align with the Periadriatic Fault, a geometry that allows for the eastward lateral extrusion of the Alpine-Carpathian-Pannonian (ALCAPA) Mega-Unit. The Mid-Hungarian Fault Zone accommodated simultaneous strike-perpendicular shortening and strike-slip movements, concomitant with strike-parallel extension. (2) The Mid-Hungarian Fault Zone is also the locus of a former plate boundary transforming opposed subduction polarities between Alps (including Western Carpathians) and Dinarides. (3) The ALCAPA Mega-Unit was affected by 290 km extension and fits into an area W of present-day Budapest in its restored position, while the Tisza-Dacia Mega-Unit was affected by up to 180 km extension during its emplacement into the Carpathian embayment. (4) The external Dinarides experienced Neogene shortening of over 200 km in the south, contemporaneous with dextral wrench movements in the internal Dinarides and the easterly adjacent Carpatho-Balkan orogen. (5) N–S convergence between the European and Adriatic plates amounts to some 200 km at a longitude of 14° E, in line with post-20 Ma subduction of Adriatic lithosphere underneath the Eastern Alps, corroborating the discussion of results based on high-resolution teleseismic tomography.The displacement of the Adriatic Plate indenter led to a change in subduction polarity along a transect through the easternmost Alps and to substantial Neogene shortening in the eastern Southern Alps and external Dinarides. While we confirm that slab-pull and rollback of oceanic lithosphere subducted beneath the Carpathians triggered back-arc extension in the Pannonian Basin and much of the concomitant folding and thrusting in the Carpathians, we propose that the rotational displacement of this indenter provided a second important driving force for the severe Neogene modifications of the Alpine-Carpathian-Dinaridic orogenic system. 相似文献
2.
3.
An exhumation model of the south Peloponnesus, Greece 总被引：1，自引：0，他引：1
T. Doutsos I. Koukouvelas G. Poulimenos S. Kokkalas P. Xypolias K. Skourlis 《International Journal of Earth Sciences》2000,89(2):350-365
An exhumation model comprising forward and backward thrusting and late orogenic collapse is proposed in order to explain
the kinematics of the tectonic windows in the south Peloponnesus. The model is based on mapping, mesoscopic structural data
and strain analysis. Syn-compressional thickening took place throughout the Oligocene and Early Miocene which includes the
subduction of the Pindos Ocean at the western margin of the Pelagonian microcontinent and the intracontinental subduction
of the Phyllite–Quartzite and the Plattenkalk series. The latter subduction was associated with blueschist metamorphism, westward-directed
ductile thrusting, and folding. The exhumation history of the deeper parts of the orogen began at the Oligocene–Miocene boundary
with the progressive entrance of the low-density crust and the Plattenkalk carbonates in the subduction zone. Increased buoyancy
caused: (a) the initiation of the Phyllite–Quartzite series extrusion; (b) vertical coaxial stretching; and (c) the evolution
of two pop-up structures, i.e. the Parnon and Taygetos anticlines. This syn-compressional exhumation was taking place in the
lower Miocene with decreasing rates from 7 to 1.5 mm/year. The change in the local stress field from compression to extension
began in the middle Miocene with the formation of hinterland-dipping normal faults. The exhumation/denudation rate caused
by the footwall uplift along these faults does not exceed 0.2 mm/year.
Received: 16 April 1999 / Accepted: 19 January 2000 相似文献
4.
陈福坤 《中国地球化学学报》2002,21(2):107-119
High-grade metamorphic Variscan basement is exposed in the Moldanubian zone of the Black Forest (BF), being the internal zone of the European Variscan belt. Zircon grains from K-rich felsic orthogneisses and an anatectic paragneiss in the Moldanubian Black Forest demonstrate a multi-stage crystallization at ～ 600 Ma, ～ 480 Ma, ～ 400 - 380 Ma, and ～350 Ma. The last three stages of crystallization probably represent metamorphic overprint during pre-Variscan and Variscan metamorphism.Using stepwise leaching procedures, garnet minerals from felsic orthogneisses as well as paragneisses in the Moldanubian Black Forest yielded Early Carboniferous Sm-Nd ages (～ 330- 340 Ma), which are consistent with the well-constrained Variscan HT metamorphic event,and Early Palaeozoic ( ～480 Ma) to Devonian ( ～400 - 370 Ma) Pb-Pb ages. The coincidence of growth time for zircon and garnet minerals at Early Palaeozoic is interpreted as dating a metamorphic event. These garnet data demonstrate that the Moldanubian BF basement underwent at least two metamorphic events during the Early Palaeozoic and Early Carboniferous.During the Variscan HT metamorphism, the Sm-Nd system of garnet was disturbed, but not the U-Pb system, implying the peak metamorphic temperature was lower than ～800℃. 相似文献
5.
Wolfgang Siebel Horst P. Hann Martin Danišík Cosmas K. Shang Christoph Berthold Johann Rohrmüller Klaus Wemmer Noreen J. Evans 《International Journal of Earth Sciences》2010,99(6):1187-1197
Movement within the Earth’s upper crust is commonly accommodated by faults or shear zones, ranging in scale from micro-displacements
to regional tectonic lineaments. Since faults are active on different time scales and can be repeatedly reactivated, their
displacement chronology is difficult to reconstruct. This study represents a multi-geochronological approach to unravel the
evolution of an intracontinental fault zone locality along the Danube Fault, central Europe. At the investigated fault locality,
ancient motion has produced a cataclastic deformation zone in which the cataclastic material was subjected to hydrothermal
alteration and K-feldspar was almost completely replaced by illite and other phyllosilicates. Five different geochronological
techniques (zircon Pb-evaporation, K–Ar and Rb–Sr illite, apatite fission track and fluorite (U-Th)/He) have been applied
to explore the temporal fault activity. The upper time limit for initiation of faulting is constrained by the crystallization
age of the primary rock type (known as “Kristallgranit”) at 325 ± 7 Ma, whereas the K–Ar and Rb–Sr ages of two illite fractions
<2 μm (266–255 Ma) are interpreted to date fluid infiltration events during the final stage of the cataclastic deformation
period. During this time, the “Kristallgranit” was already at or near the Earth’s surface as indicated by the sedimentary
record and thermal modelling results of apatite fission track data. (U–Th)/He thermochronology of two single fluorite grains
from a fluorite–quartz vein within the fault zone yield Cretaceous ages that clearly postdate their Late-Variscan mineralization
age. We propose that later reactivation of the fault caused loss of helium in the fluorites. This assertion is supported by
geological evidence, i.e. offsets of Jurassic and Cretaceous sediments along the fault and apatite fission track thermal modelling
results are consistent with the prevalence of elevated temperatures (50–80°C) in the fault zone during the Cretaceous. 相似文献
6.
Processing of gravity and magnetic maps shows that the basement of the Upper Rhine Graben area is characterized by a series
of NE–SW trending discontinuities and elongated structures, identified in outcrops in the Vosges, Black Forest, and the Odenwald
Mountains. They form a 40 km wide, N30–40° striking, sinistral wrench-zone that, in the Visean, shifted the Variscan and pre-Variscan
structures by at least 43 km to the NE. Wrenching was associated with emplacement of several generations of plutonic bodies
emplaced in the time range 340–325 Ma. The sub-vertical, NE–SW trending discontinuities in the basement acted as zones of
weakness, susceptible to reactivation by subsequent tectonism. The first reactivation, marked by mineralizations and palaeomagnetic
overprinting along NE–SW faults of the Vosges Mountains, results from the Liassic NW–SE extension contemporaneous with the
break-up of Pangea. The major reactivation occurred during the Late Eocene N–S compression and the Early-Middle Oligocene
E–W extension. The NE–SW striking basement discontinuities were successively reactivated as sinistral strike-slip faults,
and as oblique normal faults. Elongated depocenters appear to form in association with reactivated Variscan wrench faults.
Some of the recent earthquakes are located on NE–SW striking Variscan fault zones, and show sinistral strike-slip focal mechanisms
with the same direction, suggesting also present reactivation. 相似文献
7.
幔源CO_2气的形成和分布与不同级别断层早白垩世以来的活动密切相关。郯庐断裂带是研究区最主要的成气断层,拆离断层和变换断层这些地壳断层是次要的成气断层,二者于早白垩世143Ma、124Ma、新生代~43Ma、~24Ma和~8Ma的走滑或伸展活动,以及与之准同时的新生代碱性玄武岩浆活动,控制了幔源CO_2气的分散和聚集。它们与基底断裂、盖层断裂共同组成运移通道,其中拆离滑脱处的低速带和盖层断裂中的顺层断层是重要的水平运移通道。早白垩世古太平洋板块俯冲脱水脱气,产生的幔源CO_2气沿着郯庐断裂带向上分散聚集;新生代以来受控于太平洋板块俯冲方向和速度的改变以及印欧板块碰撞的远程效应,形成幔源CO_2气。与此同时郯庐断裂带切割深度亦逐渐加大,~43Ma碱性岩浆活动亦开始形成幔源CO_2气并主要位于断裂带,24Ma和8Ma(5Ma)为新近纪碱性岩浆活动脱气两个主要形成时期。郯庐断裂带的活动使地幔脱气形成的CO_2沿断层走向向上运移,并在作为重要横向运移通道的拆离断层拆离滑脱处,与因岩浆脱气形成的CO_2汇合,再通过陡倾斜、缓倾斜基底断层、盖层断层的接力传递在浅部聚集成藏。预测郯庐断裂带附近是无机成因油气重要的聚集分布区带。 相似文献
8.
Flavien Choulet Michel Faure Olivier Fabbri Patrick Monié 《International Journal of Earth Sciences》2012,101(2):393-413
The ENE–WSW Autun Shear Zone in the northeastern part of the French Massif Central has been interpreted previously as a dextral
wrench fault. New field observations and microstructural analyses document a NE–SW stretching lineation that indicates normal
dextral motions along this shear zone. Further east, similar structures are observed along the La Serre Shear Zone. In both
areas, a strain gradient from leucogranites with a weak preferred orientation to highly sheared mylonites supports a continuous
Autun–La Serre fault system. Microstructural observations, and shape and lattice-preferred orientation document high-temperature
deformation and magmatic fabrics in the Autun and La Serre granites, whereas low- to intermediate-temperature fabrics characterize
the mylonitic granite. Electron microprobe monazite geochronology of the Autun and La Serre granites yields a ca. 320 Ma age
for pluton emplacement, while mica 40Ar-39Ar datings of the Autun granite yield plateau ages from 305 to 300 Ma. The ca. 300 Ma 40Ar-39Ar ages, obtained on micas from Autun and La Serre mylonites, indicate the time of the mylonitization. The ca. 15-Ma time
gap between pluton emplacement and deformation along the Autun–La Serre fault system argue against a synkinematic pluton emplacement
during late orogenic to postorogenic extension of the Variscan Belt. A ductile to brittle continuum of deformation is observed
along the shear zone, with Lower Permian brittle faults controlling the development of sedimentary basins. These results suggest
a two-stage Late Carboniferous extension in the northeastern French Massif Central, with regional crustal melting and emplacement
of the Autun and La Serre leucogranites around 320 Ma, followed, at 305–295 Ma, by ductile shearing, normal brittle faulting,
and subsequent exhumation along the Autun–La Serre transtensional fault system. 相似文献
9.
The Schlinig fault at the western border of theÖtztal nappe (Eastern Alps), previously interpreted as a west-directed thrust, actually represents a Late Cretaceous, top-SE to -ESE normal fault, as indicated by sense-of-shear criteria found within cataclasites and greenschist-facies mylonites. Normal faulting postdated and offset an earlier, Cretaceous-age, west-directed thrust at the base of theÖtztal nappe. Shape fabric and crystallographic preferred orientation in completely recrystallized quartz layers in a mylonite from the Schlinig fault record a combination of (1) top-east-southeast simple shear during Late Cretaceous normal faulting, and (2) later north-northeast-directed shortening during the Early Tertiary, also recorded by open folds on the outcrop and map scale. Offset of the basal thrust of theÖtztal nappe across the Schlinig fault indicates a normal displacement of 17 km. The fault was initiated with a dip angle of 10° to 15° (low-angle normal fault). Domino-style extension of the competent Late Triassic Hauptdolomit in the footwall was kinematically linked to normal faulting.
The Schlinig fault belongs to a system of east- to southeast-dipping normal faults which accommodated severe stretching of the Alpine orogen during the Late Cretaceous. The slip direction of extensional faults often parallels the direction of earlier thrusting (top-W to top-NW), only the slip sense is reversed and the normal faults are slightly steeper than the thrusts. In the western Austroalpine nappes, extension started at about 80 Ma and was coeval with subduction of Piemont-Ligurian oceanic lithosphere and continental fragments farther west. The extensional episode led to the formation of Austroalpine Gosau basins with fluviatile to deep-marine sediments. West-directed rollback of an east-dipping Piemont-Ligurian subduction zone is proposed to have caused this stretching in the upper plate. 相似文献
10.
The mid-German crystalline rise has its westernmost exposures at the western margin of the Rhine graben in the southern Pfalz
and the northern Alsace. The outcrops are made up of granitoid rocks and minor volcano-sedimentary sequences. Radiometric
ages obtained by U/Pb, Pb/Pb, Sm/Nd and Rb/Sr analyses of the igneous rocks from this area range from ∼433 to ∼325 Ma thus
covering a time span from the Silurian to the end of the lower Carboniferous. Because the investigated rocks are — according
to their chemical composition — largely related to subduction zone environments, the following three geodynamical scenarios
are postulated, always taking subduction of oceanic crust beneath the mid-German crystalline rise into account: (a) subduction
of the Rheic ocean during the Silurian from the north; (b) subduction of the Rhenohercynian ocean during the late Devonian
(∼369 Ma) from the north; (c) subduction of the Saxothuringian ocean during the lower Carboniferous (∼334 Ma) from the south. 相似文献
11.
We present new Re–Os molybdenite age data on three porphyry Cu–Mo–Au deposits (Yulong, Machangqing, and Xifanping). These deposits are associated with the Himalayan adakitic magmatism that occurred in a continental collision environment, controlled by large-scale Cenozoic strike-slip faults in the eastern Indo–Asian collision zone. Three distinct episodes of Cu–Mo–Au mineralization are recognized. At Yulong, Re–Os isotopic data of four molybdenite samples from sulfide-quartz veins in the quartz–sericite alteration zone yield an isochron with an age of 40.1±1.8 Ma (2σ), coincident to a zircon sensitive high-mass resolution ion microprobe (SHRIMP) age of 40.9±0.1 Ma for the host monzogranite. The molybdenite Re–Os dates, together with K–Ar, Rb–Sr, U–Pb, and 40Ar/39Ar dates on the pre- and intra-ore porphyries, suggest that Cu–Mo–Au mineralization formed during the late stage (∼40 Ma) of regional porphyry magmatism, but hydrothermal activity probably lasted to at least ∼36 Ma. At Machangqing, molybdenite Re–Os data from the K–silicate and quartz–sericite alteration zones yield an isochron with an age of 35.8±1.6 Ma (2σ), which is identical to the zircon SHRIMP and bulk-rock Rb–Sr ages (35∼36 Ma) of the host granite, but older than bulk-rock K–Ar dates (31∼32 Ma) for associated Au-bearing quartz syenite with advanced argillic alteration. At Xifanping, five molybdenite samples from the K–silicate alteration zone yield the youngest Re–Os isochron age in the area, at 32.1±1.6 Ma (2σ). The Re–Os molybdenite dates here are younger than K–Ar ages (33.5∼34.6) for hydrothermal biotite and actinolite. There is a positive correlation between the absolute age of the deposits and their Cu and Au reserves in the eastern Indo–Asian collisional zone. Episodic stress relaxation probably caused multiple magmatic intrusions, which most likely resulted in three episodes of Cu–Mo–Au mineralization in the eastern Indo–Asian collision zone. 相似文献
12.
Jin Zhang Jinyi Li Yanfeng Li Zongjin Ma 《International Journal of Earth Sciences》2009,98(6):1511-1527
The Cenozoic deformation of the Alxa Block resulted directly from the evolution of the northern Qinghai-Tibetan Plateau. However,
many data show that the deformation occurred only in the Middle-Late Miocene. Our studies show that the Altyn Tagh fault did
not pass through the Alxa Block; on the contrary it went along the southern boundary of the Jintai-Huahai Basin, linking with
the Helishan—southern Longshoushan fault. Due to important tectonic events in the northern Qinghai-Tibetan plateau during
the Middle-Late Miocene time, the northern plateau underwent rapid uplift and the plateau compressed the Hexi Corridor Region,
resulting in a change from NS-trending to EW-trending structures in the Jinta-Huahai basin, and in the development of compressive
structures in the Beishan. The southern Alxa fault underwent right lateral movement, and in the northern and central parts
of the block, NS-trending Tertiary extensional structures formed. These basins controlled by Tertiary faults are similar to
basins developed by lateral extrusion with a strong foreland and weak limited boundaries. The authors suggest that a regional
“conjugate” fault system resulted from nearly NS-trending compression from the Qinghai-Tibetan Plateau during the Miocene
and Pliocene in the Alxa Block and southern Mongolia. And due to the control of early structures in these regions, most brittle
faults reactivated earlier ductile faults; NW–SE faults along the Altai Mountain and NE–SW faults to the southeast in Mongolia
consist of a “conjugate” fault system to the north. The Altyn Tagh fault and southern Helishan-Longshoushan fault comprise
a “conjugate” fault system to the south. The Beishan and Jinta-Huahai Basin occupied the convergent area between these two
sets of faults; the compression controlled the Tertiary deposition and led to the development of the Cenozoic Jinta-Huahai
Basin. The Alxa Block bounded by these two sets of faults moved eastwards, which resulted in the development of Cenozoic compressive
structures to the west of Helan Shan, and superimposed early ductile shear zones along the northeastern and southwestern boundaries
of the Alxa Block respectively. This model could explain the Cenozoic deformation occurring in and around the Alxa region. 相似文献
13.
The role of the Najd Fault System in the tectonic evolution of the Hammamat molasse sediments,Eastern Desert,Egypt 总被引：1，自引：1，他引：0
Mohamed A. Abd El-Wahed 《Arabian Journal of Geosciences》2010,3(1):1-26
The Hammamat molasse sediments of the Eastern Desert of Egypt were deposited in isolated basins formed during an initial stage
of orogen parallel N–S extension (650–580 Ma) in the Neoproterozoic time. Supply of sediments to the molasse basins began
after the eruption of Dokhan volcanics (602–593 Ma), exhumation of core complexes (650–550 Ma), and intrusion of late tectonic
granites (610–550 Ma). The late Neoproterozoic structures in the molasse sediments include: (1) NNW-directed thrusts due to
NNW–SSE shortening (650–640 Ma), indicated by the presence of NE-, ENE-, and WSW-trending folds and NNW-directed thrusts.
(2) SW- and NE-directed thrusts due to ENE–WSW constriction during oblique convergence and arc accretion at around 640–620 Ma.
Many of the map- and mesoscopic-scale NW-trending folds in the core complexes, the molasse sediments, and the Neoproterozoic
nappes in the Eastern Desert are related to this event. Sinistral shearing along the Najd Fault System (650–540 Ma) resulted
in the development of subvertical foliation, subhorizontal stretching lineation, and NW-trending tight folds overprinting
earlier folds. Stretched pebbles are oriented NW–SE and WNW–ESE in the molasse basins localized within the Najd Fault System,
and NE–SW in the basins outside the influence zone of this NW-trending fault system. Strain estimated using pebbles from nine
molasse basins indicate that the amount of strain differs from one basin to another and from one place to another within the
same basin. Weak tectonic strain (Rs = 2.16–2.24) is obtained from post-orogenic basins; moderate strains are reported from
foreland basins (Rs = 2.37–3.18), whereas moderate to high tectonic strains are recorded from the intermontane basins (Rs = 2.40–4.36).
The obtained tectonic strain and K values indicate that the flattening strain prevails in the post-orogenic and foreland basins, whereas as both constrictional
and flattening strains are recorded in intermontane basins. Strain variation from one basin to another and within the individual
basin is attributed to presence of thrust and sinistral shear zones. Away from the deformed zones, the pebbles show no significant
stretching. Two phases of thrusting and an episode of transpressional sinistral shearing are the latest structure features
of the East African orogeny in the Arabian–Nubian Shield. 相似文献
14.
In a sector placed in the SE part of the Alps–Apennine junction, a kilometre-scale shear zone has been identified as the Grognardo thrust zone (GTZ), which caused the NE-directed thrusting of metaophiolites (Voltri Group) and polymetamorphic continental crust slices (Valosio Unit) of Ligurian Alps onto Oligocene sediments of an episutural basin known as “Tertiary Piemonte Basin”. The structural setting of the GTZ is due to syn- to late-metamorphic deformation, followed by a brittle thrusting that occurred in the Late Aquitanian times and can thus be related to one of the main contractional tectonic events suffered by northern Apennines. The GTZ was then sealed by Lower Burdigalian carbonate platform sediments (Visone Formation). Transtensive faulting followed in post-Burdigalian times along NW–SE regional faults and displaced the previously coupled sedimentary and metamorphic units. The GTZ thus underwent a plastic-to-brittle evolution, during which carbonate-rich fluids largely sustained the deformation. In these stages, a complex vein network originated within both the metamorphic and sedimentary rocks. Field data and stable isotopic analyses (13C and 18O) of bulk rocks and veins show that fluid–rock interaction caused the carbonatisation of the rocks in the late-metamorphic stages and the cataclasis and recementation, by the action of isochemical cold carbonate groundwater during the thrusting events. Carbonate veins largely developed also during the transtensive faulting stages, with composition clearly different from that of the veins associated to thrust faults, as indicated by the strong depletion in 13C of carbonate fillings, suggesting the presence of exotic fluids, characterised by a high content of organic matter. 相似文献
15.
Dhruba Mukhopadhyay Krishnapriya Basak 《Journal of the Geological Society of India》2009,73(4):489-518
The Eastern Ghats Belt is a polycyclic granulite terrain along the east coast of India whose western boundary is marked by
a shear zone along which the granulites are thrusted over the cratonic units of the Indian shield, and its northern margin
is marked by the presence of a number of fault-bounded blocks. Recent work has convincingly brought out that there are domains
within the belt having different evolutionary histories. The segment south of the Godavari Rift went through a high grade
thermo-tectonic event at ∼1.6–1.7 Ga. North of the Godavari Rift in a narrow zone along the western boundary the last high-grade
metamorphic event is of late Archaean age. A series of alkaline plutons along the western boundary zone testifies to a rifting
episode at ∼1.3–1.5 Ga. In the major part of the EGB the metamorphism is broadly of Grenvillian age, with two major thermo-tectonic
pulses at ∼1.1–1.2 Ga and ∼0.95–1.0 Ga. But high grade conditions persisted for a long period and younger thermal events of
∼0.65 Ga to ∼0.80 Ga are locally recorded. There are differences in the tectonometamorphic histories of different domains,
but the tectonic significance of these differences remains uncertain. Pan-African (0.50–0.55) thermal overprints are common
and become conspicuous along the western boundary zone. The thrusting of the Eastern Ghats granulites in a hot state over
the cratons to the west is of Pan-African age. In the Rodinia assembly (∼0.9 Ga) the Eastern Ghats and the Rayner-Napier Complexes
of Antarctica were contiguous, but the pre-Rodinia configuration of these terrains remains unclear. At ∼0.8 Ga during the
Rodinia break up Greater India rifted apart from East Antarctica, and only later it docked with Australia-East Antarctica
at 530–550 Ma. The continuation of the East Antarctic Pan-African orogenic belts into the Eastern Ghats is yet to be ascertained. 相似文献
16.
长江中下游深部构造及其中生代成矿动力学模式 总被引：1，自引：0，他引：1
长江中下游地区是中国重要的成矿带之一。本文利用地震、大地电磁数据以及野外地质调查,并结合前人研究的地球物理和岩石地球化学资料,明确了长江中下游地区现今深部构造,系统分析了其成矿动力学演化机制。本区发育有三大断裂体系:大别-苏鲁前陆断裂系、江南-雪峰断裂系和中国东部NE-NNE向走滑断裂系。大别-苏鲁前陆断裂系为一自北向南的叠瓦式逆冲推覆构造,而江南-雪峰断裂系为一自南向北的多级逆冲推滑构造,它们沿来安-望江-阳新-天门一线形成强烈的挤压对冲构造样式。中国东部NE-NNE向走滑断裂系早期主要表现为左行平移走滑并侧向挤压,参与了对冲构造形成过程,只是部分切割其它两个逆冲体系。这三大断裂体系均经历了印支-燕山期穿时递进的构造变形。152~135Ma,古太平洋板块向欧亚大陆俯冲时,板片可能沿着转换断层撕裂并产生底侵体。下地壳在底侵体的烘烤作用下熔融并受到混染,其岩浆在多级逆冲推覆和滑脱构造背景下充分结晶分异形成低镁埃达克岩,于断隆或隆坳过渡带生成铜矿。135~127Ma,长江中下游成矿带深部地幔开始上隆,诱发加厚岩石圈沿着郯庐断裂带局部拆沉,并引发富集地幔上升流。其与残留地壳交代反应,在郯庐断裂带两侧形成高镁埃达克岩。古太平洋板块继续向南西俯冲并发生逆时针旋转,长江中下游地区大多数NNE向断裂已转变为右行走滑,形成右行右阶的走滑拉分盆地。上隆地幔的基性岩浆沿着深切地壳的走滑断裂上升到盆地中,快速冷却形成橄榄玄粗岩岩系,从而在接触带或潜火山岩体顶部分异产生铁矿。 相似文献
17.
Wolfgang Müller Giacomo Prosser Neil S. Mancktelow Igor M. Villa Simon P. Kelley Giulio Viola Felix Oberli 《International Journal of Earth Sciences》2001,90(3):623-653
Fault rocks from various segments of the Periadriatic fault system (PAF; Alps) have been directly dated using texturally controlled Rb-Sr microsampling dating applied to mylonites, and both stepwise-heating and laser-ablation 40Ar/39Ar dating applied to pseudotachylytes. The new fault ages place better constraints on tectonic models proposed for the PAF, particularly in its central sector. Along the North Giudicarie fault, Oligocene (E)SE-directed thrusting (29-32 Ma) is currently best explained as accommodation across a cogenetic restraining bend within the Oligocene dextral Tonale-Pustertal fault system. In this case, the limited jump in metamorphic grade observed across the North Giudicarie fault restricts the dextral displacement along the kinematically linked Tonale fault to ~30 km. Dextral displacement between the Tonale and Pustertal faults cannot be transferred via the Peio fault because of both Late Cretaceous fault ages (74-67 Ma) and sinistral transtensive fault kinematics. In combination with other pseudotachylyte ages (62-58 Ma), widespread Late Cretaceous-Paleocene extension is established within the Austroalpine unit, coeval with sedimentation of Gosau Group sediments. Early Miocene pseudotachylyte ages (22-16 Ma) from the Tonale, Pustertal, Jaufen and Passeier faults argue for a period of enhanced fault activity contemporaneous with lateral extrusion of the Eastern Alps. This event coincides with exhumation of the Penninic units and contemporaneous sedimentation within fault-bound basins. 相似文献
18.
Osman Parlak 《International Journal of Earth Sciences》2006,95(4):609-627
In southeast Anatolia, there are number of tectonomagmatic units in the Kahramanmaraş–Malatya–Elazığ region that are important in understanding the geological evolution of the southeast Anatolian orogenic belt during the Late Cretaceous. These are (a) metamorphic massifs, (b) ophiolites, (c) ophiolite-related metamorphics and (d) granitoids. The granitoids (i.e. Göksun–Afşin in Kahramanmaraş, Doğanşehir in Malatya and Baskil in Elazığ) intrude all the former units in a NE–SW trending direction. The granitoid in Göksun–Afşin (Kahramanmaraş) region is mainly composed of granodioritic and granitic in composition. The granodiorite contains a number of amphibole-bearing mafic microgranular enclaves of different sizes, whereas the granite is intruded by numerous aplitic dikes. The granitoid rocks have typical calcalkaline geochemical features. The REE- and Ocean ridge granite-normalized multi-element patterns and tectonomagmatic discrimination diagrams, as well as biotite geochemistry suggest that the granitoids were formed in a volcanic arc setting. The K–Ar geochronology of the granitoid rocks yielded ages ranging from 85.76±3.17 to 77.49±1.91 Ma. The field, geochemical and geochronological data suggest the following Late Cretaceous tectonomagmatic scenario for southeast Anatolia. The ophiolites were formed in a suprasubduction zone tectonic setting whereas the ophiolite-related metamorphic rocks formed either during the initiation of intraoceanic subduction or late-thrusting (∼90 Ma). These units were then overthrust by the Malatya–Keban platform during the progressive elimination of the southern Neotethys. Thrusting of the Malatya–Keban platform over the ophiolites and related metamorphic rocks was followed by the intrusion of the granitoids (88–85 Ma) along the Tauride active continental margin in the southern Neotethys. 相似文献
19.
Summary The Lanterman Fault Zone, a major terrane boundary in northern Victoria Land, displays a polyphase structural evolution. After
west-over-east thrusting, it experienced sinistral strike-slip shearing. Sheared metabasites from the Wilson Terrane (inboard
terrane) preserve a record of retrograde metamorphic evolution. Shearing took place under amphibolite-facies metamorphic conditions
(roughly comparable to those reached during regional metamorphism) which later evolved to greenschist-facies conditions. In
contrast, the Bowers Terrane (outboard terrane) preserves a prograde metamorphic evolution which developed from greenschist-facies
to amphibolite-facies metamorphism during shearing, followed by greenschist-facies metamorphism during the late deformational
stages. Laser step-heating 40Ar–39Ar analyses of syn-shear amphibolite-facies amphiboles yielded ages of 480–460 Ma, in agreement with a ∼480-Ma age obtained
from a biotite aligned along the mylonitic foliation. These ages are younger than those (∼492 to ∼495 Ma) obtained from pre-shear
amphibole relics linked to regional metamorphism of the Wilson Terrane. Results attribute the structural and metamorphic reworking
during shearing to the late stages of the Cambrian-Ordovician Ross Orogeny and to the Middle-Late Ordovician probably in relation
to the beginning of deformation in the Lachlan Orogen, thus precluding any appreciable impact of the Devonian-Carboniferous
Borchgrevink event in the study area. 相似文献
20.
George R. Priest Chris Goldfinger Kelin Wang Robert C. Witter Yinglong Zhang António M. Baptista 《Natural Hazards》2010,54(1):27-73
To explore the local tsunami hazard from the Cascadia subduction zone we (1) evaluate geologically reasonable variability
of the earthquake rupture process, (2) specify 25 deterministic earthquake sources, and (3) use resulting vertical coseismic
deformations for simulation of tsunami inundation at Cannon Beach, Oregon. Maximum runup was 9–30 m (NAVD88) from earthquakes
with slip of ~8–38 m and M
w ~8.3–9.4. Minimum subduction zone slip consistent with three tsunami deposits was 14–15 m. By assigning variable weights
to the source scenarios using a logic tree, we derived percentile inundation lines that express the confidence level (percentage)
that a Cascadia tsunami will not exceed the line. Ninety-nine percent of Cascadia tsunami variation is covered by runup ≤30 m and 90% ≤16 m with a “preferred”
(highest weight) value of ~10 m. A hypothetical maximum-considered distant tsunami had runup of ~11 m, while the historical
maximum was ~6.5 m. 相似文献