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1.
The discovery of the Neoarchean mafic dyke swarm in Hengshan and reinterpretation of the previous "Wutai greenstone belt" 总被引：2，自引：0，他引：2
The structural mapping and section study indicate that the "greenstone belts" in the southern to central parts of Hengshan were intensively sheared and transposed mafic dyke swarm,which originally intruded into the Neoarchean grey gneiss and high-pressure granulite terrain(HPGT).The HPGT is characterized by flat-dipping structures,to the south it became steep and was cut by the Dianmen mafic dyke swarm.After high-pressure granulite-facies metamorphic event,the mafic dyke swarm occurred,and was associated with the extensional setting and reworked by the late strike-slip shearing.The zircon age dating proves that the Dianmen mafic dyke swarm was emplaced during the period between 2499±4 Ma and 2512±3 Ma,followed by late tectonothermal reworking.The Dianmen mafic dyke swarm further documents the extensional episode in the central to northern parts of North China Craton(NCC),providing the important constraint for the limit between Archean and Proterozoic and correlation between NCC and other cratonic blocks of the world. 相似文献
2.
The discovery of the Neoarchean mafic dyke swarm in Hengshan and reinterpretation of the previous “Wutai greenstone belt” 总被引：2，自引：0，他引：2
The structural mapping and section study indicate that the “greenstone belts” in the southern to central parts of Hengshan
were intensively sheared and transposed mafic dyke swarm, which originally intruded into the Neoarchean grey gneiss and high-pressure
granulite terrain (HPGT). The HPGT is characterized by flat-dipping structures, to the south it became steep and was cut by
the Dianmen mafic dyke swarm. After high-pressure granulite-facies metamorphic event, the mafic dyke swarm occurred, and was
associated with the extensional setting and reworked by the late strike-slip shearing. The zircon age dating proves that the
Dianmen mafic dyke swarm was emplaced during the period between 2499±4 Ma and 2512±3 Ma, followed by late tectonothermal reworking.
The Dianmen mafic dyke swarm further documents the extensional episode in the central to northern parts of North China Craton
(NCC), providing the important constraint for the limit between Archean and Proterozoic and correlation between NCC and other
cratonic blocks of the world. 相似文献
3.
Archean greenstone belts are supracrustal sequences, the lower part of which is usually composed of voluminous ultramafic-mafic volcanics. Intermediate and acid volcanic rocks increase in abundance towards the upper domains. Greenstone belts constitute ~30% of the total volume of Archean cratons, and preserve significant information on the surface environment and magmatism in the early earth, which are useful in unraveling the nature of crustal formation and evolution. The western Shandong Province(WSP) is located at the eastern part of the North China Craton(NCC), where greenstone sequences formed at ~2.7 and ~2.5 Ga were well preserved. The early Neoarchean supracrustal rocks include komatiite-basalt sequence, some meta-sediments of the lower part of the Taishan Group and the Mengjiatun Formation. The volcanism had been correlated to mantle plume, which resulted in vertical crustal accretion. The late Neoarchean supracrustal rocks were composed of metamorphosed felsic volcano-sedimentary sequences and BIFs of the upper part of the Taishan Group and the Jining Group. The geochemical features of the meta-volcanics show calc-alkaline affinities, similar to modern arc-related magmatism, suggesting that the continental crust in the western Shandong Province witnessed horizontal plate movements at ~2.5 Ga. The metasediments and leucosomes in the Qixingtai area display regional upper amphibolite facies metamorphism and anatexis at 2.53–2.50 Ga, coeval with formation of large volumes of crustally-derived granites. These tectono-thermal events suggest that a unified continental crust was formed in the western Shandong Province at the end of Neoarchean. 相似文献
4.
Regional differences in crustal structure of the North China Craton from receiver functions 总被引：5，自引：0，他引：5
Moho depth and crustal average Poisson's ratio for 823 stations are obtained by H-? stacking of receiver functions. These, together with topography and receiver function amplitude information, were used to study the crustal structure beneath the North China Craton(NCC). The results suggest that modified and preserved crust coexist beneath the craton with generally Airy-type isostatic equilibrium. The equilibrium is relatively low in the eastern NCC and some local areas in the central and western NCC, which correlates well with regional geology and tectonic features. Major differences in the crust were observed beneath the eastern, central, and western NCC, with average Moho depths of 33, 37, and 42 km and average Poisson's ratios of 0.268, 0.267 and 0.264, respectively. Abnormal Moho depths and Poisson's ratios are mainly present in the rift zones, the northern and southern edges of the central NCC, and tectonic boundaries. The crust beneath Ordos retains the characteristics of typical craton. Poisson's ratio increases roughly linearly as Moho depth decreases in all three parts of the NCC with different slopes. Receiver function amplitudes are relatively large in the northern edge of the eastern and central NCC, and small in and near the rifts. The Yanshan Mountains and southern part of the Shanxi rift show small-scale variations in the receiver-function amplitudes. These observations suggest that overall modification and thinning in the crust occurred in the eastern NCC, and local crustal modification occurred in the central and western NCC. Different crustal structures in the eastern, central, and western NCC suggest different modification processes and mechanisms. The overall destruction of the crustal structure in the eastern NCC is probably due to the westward subduction of the Pacific Plate during the Meso-Cenozoic time; the local modifications of the crust in the central and western NCC may be due to repeated reactivations at zones with a heterogeneous structure by successive thermal-tectonic events during the long-term evolution of the NCC. 相似文献
5.
本文对布设在华北克拉通东西两块体交界区域的宽频带流动地震观测台阵和部分固定台站的远震波形记录开展了SKS波分裂研究.结果显示,鄂尔多斯块体内部的各向异性比较弱,剪切波分裂导致的时间延迟一般小于0.7s.鄂尔多斯块体东缘的山西断陷带和太行山以及华北平原西部均表现出了比较强的各向异性,时间延迟大于1.0s.特别是在太行山地区观测到的ENE趋向的快波偏振方向明显不同于鄂尔多斯块体和华北平原地区的近E-W和ESE方向的快波偏振方向.在华北克拉通东西两块体交界过渡带的太行山地区观测到的显著上地幔各向异性及变化可能对应于围绕鄂尔多斯块体东南角的局部软流圈绕流,而后者可能起因于鄂尔多斯块体的逆时针旋转以及青藏高原软流圈沿秦岭大别造山带向东的流动. 相似文献
6.
《中国科学:地球科学(英文版)》2021,(9)
The Early Cretaceous represents a peak period of the North China Craton(NCC) destruction. A comprehensive analysis of crustal deformation during this period can reveal processes and dynamics of the destruction. The peak destruction of the NCC was associated with intense extension whose representative deformation products are metamorphic core complexes(MCCs), extensional domes and rifted basins. These MCCs occurred along both northern and southern margins of the NCC, and resulted from synchronous extension and magmatism, showing difference from the typical orogen-type MCCs in many aspects.The MCCs of the Early Cretaceous were replaced by extensional domes under relatively weak extension and uplift. In contrast to a major depression-type basin of the Early Cretaceous in the western NCC, rifted basins of the same age in the eastern NCC appeared as medium-to small-scale ones extensively. In the eastern NCC, the rifted basins north of the Bohai Bay are characterized by a feature similar to an active rift whereas those south of the Bohai present similarity to a passive rift. Various sorts of extensional structures developed during the peak destruction indicate a stable stress state of NE-SE extension over the entire central to eastern NCC, consistent with the plate margin-driven stress field. Spatial distribution of the extensional structures presents an 1800 km wide back-arc extension region in the central to eastern NCC, consistent with the Paleo-Pacific slab rollback model following flat subduction. Temporal-spatial variation of initial extension and volcanic activity during the peak period also supports the rollback model right after the flat oceanic slab. The crustal deformation evolution demonstrates that the peak destruction of the NCC took place after the B-episode compression of the Yanshan Movement of the earliest Early Cretaceous and terminated with onset of the C-episode compression of the earliest Late Cretaceous. 相似文献
7.
LIU Yongsheng GAO Shan WANG Xuance HU Shenghong & WANG Jianqi . State Key Laboratory of Geological Processes Mineral Resources China University of Geosciences Wuhan China . Key Laboratory of Continental Dynamics Department of Geology Northwest University Xi’an China 《中国科学D辑(英文版)》2005,48(8):1106-1119
Hofmann[1] found that the depleted mantle (DM) and bulk continental crust (BCC) are simply compen-satory in terms of many elements and elemental ratios. High-field-strength elements (HFSE) (e.g., Zr, Hf, Nb, Ta and Ti) are immobile and thus useful to track the primary features of the ancient mafic volcanics. It has been long considered that Nb-Ta behave as identical twins during magmatic processes, based on their matching atomic radii and valence state and hence coherent geochemical affi… 相似文献
8.
9.
Indication from finite-frequency tomography beneath the North China Craton: The heterogeneity of craton destruction 总被引：1，自引：0，他引：1
We picked new traveltime residual datasets in three frequency bands(0.02–0.1, 0.1–0.8, and 0.8–2.0 Hz) for P-waves from 793 teleseismic events and two frequency bands(0.02–0.1 and 0.1–0.8 Hz) for S-waves from 310 teleseismic events,recorded by 389 permanent stations of the China National Seismic Network and 832 broadband stations of 10 temporary arrays deployed in the North China Craton(NCC) region. The final datasets are composed of 65628 P-arrivals and 47050 S-arrivals.Based on previous research and our team's 2012 tomographic work, we constructed new three-dimensional P-velocity and Svelocity models of the NCC through some improvements, such as augmenting a much denser station coverage in the western NCC, considering the incident angle effect in crustal correction and using a multi-frequency joint inversion tomographic technique. The new velocity models provide several salient features, from which we draw possible inferences on regional dynamic processes. We observed high-velocity anomalies in the mantle transition zone(MTZ). Obvious morphological heterogeneities suggest buckling and/or fragmentation of the subducted Pacific slab, and some of the slab materials are visible below 660-km discontinuities. The velocity structure of the eastern NCC is dominated by small-scale lateral heterogeneities. At shallow depths, high-velocity anomalies beneath the southern part of the eastern NCC and the Yanshan region likely represent a remnant of cratonic lithosphere, which may suggest that the NCC destruction is spatially non-uniform. We also detected a highvelocity anomaly in the Sulu Orogen extending downward to ~300 km, which is seemingly controlled by the Tan-Lu Fault. The northern boundary of this anomaly spatially coincides with the Yantai-Qingdao-Wulian Fault, and is likely a remnant of the Yangtze cratonic lithosphere subducting northwestward. Significant low-velocity anomalies imaged beneath the central NCC show a spatial discordance between their northern and southern parts. The northern low-velocity anomaly extends downward to the top of MTZ with a lateral NW-SE strike, whereas the southern one tapers off at ~200–300 km. Low-velocity anomalies are present beneath the Phanerozoic orogenic belts surrounding the NCC, the Paleoproterozoic Trans-North China Orogen, and the Tan-Lu Fault. This feature not only shows excellent spatial correlation with the orogens at the surface, it also exhibits a consistent vertical continuity in a depth range of 60–250 km. This intriguing feature suggests that the collisional orogenic belts and Tan-Lu Fault are inherited weak zones, which may play a key role in craton destruction. By combining multidisciplinary results in this area, we suggest that the spatial heterogeneities associated with the NCC destruction most likely result from the combined effects of a spatially non-uniform distribution of wet upwellings triggered by the subducted Pacific slab and pre-existing weak zones in the cratonic lithosphere. 相似文献
10.
The present paper reports the results of a detailed stratigraphical, petrological and geochemical investigation on the island of Stromboli, Aeolian arc, Southern Tyrrhenian sea. Major and trace element data determined on a large quantity of samples from well-established stratigraphic positions indicate that the magmatological evolution of the island through time was more complex than previously known. The activity of the exposed part of Stromboli, which occurred over a time span of about 100 000 years, started with the emission of high-K calc-alkaline (HKCA) volcanics, which were covered by calc-alkaline (CA), shoshonitic (SHO), high-K calc-alkaline (HKCA) and potassic (KS) products. The most recent activity consists of HKCA lavas and the present-day SHO-basaltic volcanics emitted by mildly explosive “strombolian” activity. Most of the products are lavas, with minor amounts of pyroclastic rocks emplaced mainly during the early stages of activity. The transition from the SHO to the KS cycle was associated with the collapse of the upper part of the volcanic apparatus; the transition from KS to the present-day SHO activity has been found to have occurred at the time of the sliding of the western portion of the volcano that generated the “Sciara del Fuoco” depression. The rock series cropping out at Stromboli show variable enrichment in potassium, incompatible trace elements and radiogenic Sr which increase from CA through HKCA, and SHO up to KS rocks. Major, trace element and Sr-isotopic data agree in indicating that the HKCA and SHO series evolved by crystal/liquid fractionation starting from different parental liquids, whereas crustal assimilation appears to have been the leading process during the evolution of KS volcanics. Mixing processes also played a role although they can be well documented only when they occurred between magmas with different isotopic and geochemical characteristics. Geochemical modelling based on trace element and isotopic data indicates that the mafic magmas of the different volcanic series may be generated by melting of an upper mantle heterogeneously enriched in incompatible elements and radiogenic Sr by addition, via subduction, of different amounts of crustal material. Geochemical data, however, are also in agreement with the alternative hypothesis that the most mafic magmas of the different series have been generated by combined processes of fractional crystallization, assimilation and mixing of a CA magma in a deep-sited magma chamber; the mafic magmas formed by these complex processes were successively emplaced in a shallow reservoir where they evolved by simple fractional crystallization (HKCA and SHO series) and by assimilation of crustal material (KS). The occurrence of changes in the geochemical signatures of the magmas at the time of the structural modification of the volcano is believed to favour the hypothesis that the variable composition observed in the volcanic rocks of Stromboli is the result of processes occurring within the volcanic system. 相似文献
11.
We present the 1-D crustal velocity structure of the major tectonic blocks of the North China Craton(NCC) along 36°N based on synthetic seismogram modeling of long-range wide-angle reflection/refraction data. This profile extends from southwest Yan'an of central Shaanxi Province of China(109.47°E), across the southern Trans-North China Orogen(TNCO), the southwestern part of the North China Plain(NCP), the Luxi Uplift(LU) and the Sulu Orogen(SLO), ending at Qingdao City of Shandong Province, the eastern margin of China(120.12°E) along 36°N. We utilized reflectivity synthetic seismogram modeling of the active source data to develop 1-D velocity structures of the sub-blocks of the NCC. Our final model shows that the NCC crust varies remarkably among the tectonic units with different velocity structure features. Higher lower crustal velocity and Moho depth ～42 km is a major feature of the crust beneath southern Ordos Blockt. The TNCO which is composed of Lyuliangshan Mountains(LM), Shanxi Graben(SXG) and Taihangshan Mountains(TM) shows dominant trans-orogenic features. The NCP shows a dominant thickening of sediments, sharp crust thinning with Moho depth ～32 km and significant lower average velocity. The SLO and the LU shows a stratified crust, higher average velocity and crust thinning with Moho depth of ～35 km. Our model shows the coincidence between the deep structure and the surface geology among all the tectonic sub-blocks of the NCC. 相似文献
12.
LI Yonggang ZHAI Mingguo YANG Jinhui MIAO Laicheng & GUAN HongInstitute of Geology Geophysics Chinese Academy of Sciences Beijing China Correspondence should be addressed to Li Yonggang 《中国科学D辑(英文版)》2004,47(2):115-121
The Anjiayingzi gold deposit in Chifeng County, Inner Mongolia is located in the central part of the gold mineralization belt of the northern margin of the North China Craton (NCC), and is adjacent to the Paleozoic Inner Mongolia-Da Hinggan Mountains orogenic belt in the north. The Chifeng-Kaiyuan fault, which separates the NCC from this orogenic belt, is considered to be a regional ore-controlling structure. The Anjiayingzi gold deposit is a mediate-size quartz lode-gold deposit and is hosted by the Anjiayingzi quartz monzonite that was emplaced into the basement composed of early Precambrian gneisses. Rhyolitic and porphyritic dikes are generally associated with the gold mineralization. Zircon U-Pb analyses suggest that the Anjiayingzi granite was emplaced from 132 Ma to 138 Ma, while the rhyolitic dikes that occupy the same fracture system as the gold-bearing quartz veins and locally crosscut the gold lodes crystallized from 125 Ma to 127 Ma. These results constrain the mineralization age between 126 相似文献
13.
14.
Structure,evolution and regional tectonic implications of the Queshan metamorphic core complex in eastern Jiaodong Peninsula of China 总被引：1，自引：0，他引：1
ZengMing Xia JunLai Liu JinLong Ni TingTing Zhang XingMing Shi Yun Wu 《中国科学:地球科学(英文版)》2016,59(5):997-1013
The Queshan MCC is an important example of a crustal extensional structure in the eastern Jiaodong Peninsula along the southeastern margin of the NCC in the Early Cretaceous. The MCC is a typical Cordilleran-type core complex with a three-layered structure: (1) the upper plate is constituted by the Cretaceous supradetachment basin and Paleoproterozoic basement; (2) the lower plate comprises the Neoarchean high-grade metamorphic complexes and late Mesozoic granitic intrusions; and (3) the two plates are separated by a master detachment fault. A series of late NEN-oriented brittle faults superimposed on and destructed the early MCC. Petrology, geometry, kinematics, macro- and micro-structures and quartz c-axis fabrics imply that the MCC has a progressive exhumation history from middle-lower to subsurface level (via middle-upper crustal level) under the nearly WNW-ESE regional extensional regime. We present structural and geochronological evidence to constrain the exhumation of the Queshan MCC from ca. 135 to 113 Ma. Based on the comprehensive analysis of the different patterns of extensional structures in the Jiaodong and Liaodong Peninsula, we have defined the Jiao-Liao Early Cretaceou extensional province and further divided the crustal extension of it into two stages: the first stage was the intense flow of the middle-lower crust and the second stage was the extension of the middle-upper crust. Combining the tectonic setting, the lithosphere thinning in the Jiao-Liao Early Cretaceous extensional province can be considered a typical model for the response of crust-mantle detachment faulting under regional extension in East Asia. 相似文献
15.
运用LA-ICP MS锆石U-Pb定年、角闪石和黑云母40Ar-39Ar定年、锆石和磷灰石裂变径迹(FT)分析等构造热年代学研究方法,探讨分析了鄂尔多斯盆地东缘紫金山侵入岩的热演化历史及其抬升冷却过程.紫金山侵入岩主要由次透辉二长岩和正长岩组成,锆石U-Pb测年给出的岩浆侵位-结晶年龄为136.7 Ma,角闪石和黑云母40Ar-39Ar测年获得的岩浆结晶-固结年龄集中在133.1~130.4 Ma,表明紫金山侵入岩主要形成于早白垩世的136.7~130.4 Ma.侵入岩T-t轨迹与磷灰石FT模拟热史路径综合揭示了鄂尔多斯盆地东缘紫金山侵入岩抬升冷却的三个构造热演化阶段:1) 136~120 Ma侵位岩浆结晶-固结阶段,岩体平均冷却速率高达52 ℃/Ma;2) 120~30 Ma岩体相对缓慢抬升冷却阶段,平均抬升冷却速率为2.5 ℃/Ma;3) 30 Ma以来岩体快速抬升冷却阶段,平均抬升冷却速率3.6 ℃/Ma,尤以近10 Ma以来的快速抬升冷却最为显著,抬升冷却速率接近7 ℃/Ma.结合区域构造动力学环境分析认为,鄂尔多斯盆地东缘的紫金山岩浆活动与华北克拉通早白垩世构造体制转换过程的大规模岩浆活动属于相同时期、统一构造作用的产物,早白垩世末期以来由慢到快的差异抬升过程主要受控于华北克拉通东部(古)太平洋体系与其西南部特提斯体系之间相互联合、彼此消长的构造作用. 相似文献
16.
Most studies of seismic noise cross-correlation (NCC) have focused on regional/continental scale imaging using empirical surface-wave Green’s functions extracted from primary (0.05–0.08 Hz) and secondary (0.1–0.16 Hz) microseisms. In this work, we present the NCC results at higher frequencies (>0.5 Hz) from 6 months seismic noise recorded by a local array (~4 km aperture) deployed along the Calico fault in the Mojave Desert, California. Both fast and slow propagating waves are observed from the NCC record-sections. We compare the NCCs from sensor pairs that share a common sensor with the records of a borehole shot located very close to this common sensor. The result shows a good match of the slow surface-wave arrivals, indicating that the NCC method is able to recover unbiased surface-wave Green’s functions at local scales. The strong body-wave NCC component is caused by the P waves generated offshore California. Along a SW–NE profile across the fault, we observe apparent P-wave arrivals and their reflections, which can be explained by a low-velocity-zone (LVZ) along the Calico fault. We calculate the LVZ width to be ~ 2.3 km, and the P-wave velocity reduction within the LVZ to be ~35 %. These estimates are consistent with other evidence for a relatively wide LVZ along the Calico fault. 相似文献
17.
Relatively little is known about the long-term sediment accumulation dynamics of Naracoorte Cave Complex (NCC) solution pipe cavities, and many of the megafauna-bearing infill deposits at this globally significant Australian Pleistocene fossil locality remain partially dated or lack any numerical age control. In this study, we assess the suitability of three different luminescence dating signals for improving existing chronologies at six Late and Middle Pleistocene NCC sites (n = 22 samples), and we undertake multi-site examinations of NCC sediment infill dynamics spanning the last 550 thousand years (ka). Modern analogue samples collected from above and beneath two active cave entrances confirm that single-grain OSL, single-grain TT-OSL and multi-grain pIR-IRSL signals can be reset down to insignificant residual levels (<10−1–100 Gy) when compared with the natural dose ranges of interest for most NCC palaeontological applications. Replicate luminescence dating comparisons performed at six NCC fossil sites (n = 15 samples) reveal consistent ages for twenty-eight out of thirty-one paired OSL–TT-OSL, OSL–pIR-IRSL and TT-OSL–pIR-IRSL datasets. Nineteen of the twenty Middle to Late Pleistocene samples analysed from the NCC sites produce homogeneous OSL, TT-OSL and pIR-IRSL De datasets suggesting that the NCC solution pipe deposits considered here are generally not affected by syn-depositional mixing complications that can take place within closed karst cavities (i.e., the remobilisation of unbleached grains from pre-existing cave floor sediments, and their subsequent translocation and incorporation into deposits within deeper parts of the cavity along with externally bleached, allochthonous grain populations). Detailed examination of solution pipe dynamics at Smoke Tortoise Cave (SMT) reveals a complex accumulation history focused on the marine isotope stage (MIS) 9 and MIS 7 interglacial complexes, as well as the MIS 8e interstadial. The SMT case study highlights that NCC solution pipes are not simply associated with short-lived opening and sediment accumulation events, but may involve multiple, discontinuous deposition episodes and reactivation events. An initial multi-site examination of all published NCC infill chronologies (n = 70) appears to suggest statistically significant, preferential solution pipe development during the relatively wet parts of interglacial or interstadial cycles. The non-uniform infill age distribution implies that NCC solution pipe dynamics may have exerted taphonomic biases on fossil accumulation, which should be taken into consideration when reconstructing long-term palaeoecological histories from NCC solution pipe cavities. 相似文献
18.
The paleomagnetism and geological significance of Mesoproterozoic dyke swarms in the central North China Craton 总被引：4，自引：0，他引：4
The Mesoproterozoic mafic dyke swarms are extensively distributed in the central North China Craton(NCC) including North Shanxi,
Wutai and Lüliang areas, which are not deformed and metamorphic but high magnetic, so the dyke swarms become the mark to compare
the high metamorphic rock areas in magnetism. Based on the analysis of paleomagnetism of mafic dyke swarms in North Shanxi,
Wutai and Lüliang areas, NCC inclined southward about 18ü so that North Shanxi lifted up and rotated 10ü left to Wutai area.
The dyke swarms in Lüliang developed later than in North Shanxi and Wutai area. The NNW-trending and WNW-trending dyke swarms
developed in Lüliang while the North China Plate moved northward consistently so that the paleomagnetism of dyke swarms in
Lüliang is greatly different from North Shanxi and Wutai area. 相似文献
19.
Determination of the physical and chemical structures of the inaccessible continental lithosphere by comprehensive geophysical and geochemical studies can provide valuable information on its formation and evolution.Extensive studies from various disciplines have revealed complex lithospheric modification of the North China Craton(NCC),but less attention has been paid to an integrated study from different fields.Here we provide an integrated constraint on the lithospheric mantle structure of the NCC by comprehensive semiology,gravity and thermal studies with xenolith data involving depth(levels in the lithosphere),property(chemical and physical),and timing(formation and reworking ages).Our results suggest that the NCC has a relatively heterogeneous lithospheric mantle.Its margins and internal weak zones,especially in the eastern NCC,are generally underlain by the fertile,weakly metasomatized mantle with generally young formation ages.In contrast,its core tends to preserve the refractory,strongly metasomatized mantle with ages roughly coupled to the overlying Archean crust.Such a lithospheric structure shows the preferential modification of the lithospheric mantle in the eastern NCC and in the peripheral regions of the western NCC.The interior of the craton,especially most of the western NCC,remains stable and has been weakly modified. 相似文献
20.
The lithosphere of the North China Craton(NCC) has experienced significant destruction and deformation since the Mesozoic, a notable feature of which is the widespread extensional structure and lithospheric thinning in the eastern NCC. Since the thermo-rheological structure of the lithosphere is one of the main factors controlling these dynamic processes, a threedimensional thermo-rheological model of the present lithosphere in the NCC was developed based on a geophysical-petrological method using a variety of data, and its relationship with the extensional structures and the formation of rifts was further analyzed.Our results show that the western NCC is characterized by thick lithosphere, low Moho temperature(T_(Moho)600°C), as well as high lithospheric strength and mantle-crust strength ratio(S_m/S_c1). The deformation of the western narrow rift is consistent with the localized deformation dominated by the strength of lithospheric mantle. On the other hand, the lithosphere in the eastern NCC is characterized by extensive thinning(with lithospheric thickness of about 80–110 km). However, the decrease of lithospheric strength is not uniform, with high strength(10×10~(12) Pa m) observed in some areas(such as the Bohai Bay Basin and Hehuai Basin). Most of the eastern lithosphere is characterized by high TMoho(600–750°C) and low S_m/S_c(1), which is inconsistent with the widespread extensional structure in the eastern NCC. Incorporating results from palaeo-geothermal and petrological studies,we developed a thermo-rheological structure model of the lithosphere at different evolutionary stages of the NCC, and suggested that the eastern NCC had a significantly thinned and weakened lithosphere in the early stages of the formation of the rift, leading to a regional distributed extension deformation dominated by crustal strength, which eventually evolved into a series of wide rifts. However, the cooling and accretion of the lithosphere in the subsequent stages significantly increased the strength of the lithospheric mantle, resulting in the inconsistency between the present thermo-rheological structure of the lithosphere and the extensional structure formed in the past. 相似文献