检索结果-南通市图书馆

A Synthesis of Geophysical Data in Southeastern North China Craton:Implications for the Formation of the Arcuate Xuhuai Thrust Belt

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2022年第3期33卷 552-566页

作者： Yangfan Deng Yun Chen Pengfei Li Zhou Zhang JoséBadal state key laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China CAS Center for Excellence in Deep Earth Science Guangzhou 510640China state key laboratory of lithospheric evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Physics of the Earth Sciences BUniversity of ZaragozaPedro Cerbuna 1250009 ZaragozaSpain

The Xuhuai fold thrust belt(XHTB)is a curved structure in the southeastern margin of the North China Craton(NCC)that has attracted great attentions due to its tectonic and petrological ***,few geophysical studies have focused on the deep structure of this *** this study,we carry out a systematic demonstration of the main geophysical features that characterize the XHTB and surrounding *** results reveal small negative gravity and magnetic anomalies,thin crust and lithosphere,lower shear velocity and shallower earthquake epicenters relative to other areas of the NCC,collectively indicating a lithospheric-scale rheological anomaly at this *** magnetic alignments show a trend similar to that of geological units in southeastern NCC and adjacent areas,although they differ from the SKS-splitting fast polarization directions,except in the Qinling-Dabie orogen where a vertical coherent deformation of the crust and mantle may be involved *** on the geophysical data,we propose a detachment-controlled model,which was caused by the different detachment depth/strength,for the formation of XHTB to explain its arcuate shape as well as the magnetic alignments,thus providing new insight into the deep processes of southeastern NCC.

关键词： gravity and magnetic anomalies shear wave velocity seismicity seismic anisotropy magnetic alignments arcuate structure

The evolution of coal, examining the transitions from anthracite to natural graphite: a spectroscopy and optical microscopy evaluation

在线全文

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2023年第1期17卷 87-99页

作者： Liang YUAN Qinfu LIU Kuo LI Ying QUAN Xiaoguang LI Jonathan P.MATHEWS School of Geosciences and Surveying Engineering China University of Mining and Technology(Beijing)Beijing 100083China state key laboratory of lithospheric evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China The EMS Energy institute and the Leone Family Department of Energy and Mineral EngineeringPennsylvania State UniversityUniversity Park PA 16802USA

Coal-derived natural graphite(CDNG)has multiple industrial ***,ten metamorphic coals from anthracite to CDNG were obtained from Lutang and Xinhua in the Hunan Province and Panshi in the Jilin *** characterization(proximate and ultimate analyses,X-Ray powder diffraction(XRD),and powder Raman spectroscopy),along with optical microscopy,scanning electron microscope(SEM)and micro-Raman spectroscopy were utilized to examine the transitions from anthracite to semi-graphite to *** XRD and Raman spectroscopy data indicate that from anthracite to highly ordered graphite the average crystal diameter(La)and height(Lc)increased from 6.1 and 4.6 nm to 34.8 and 27.5 nm,*** crystalline parameters of the CDNG samples from Panshi and Lutang varied slightly when closer to the intrusive *** microscopy and SEM indicated that in the anthracite samples there were thermoplastic vitrinite,devolatilized vitrinite,and some“normal”*** the meta-anthracite,pyrolytic carbon,mosaic structure,and crystalline tar were *** the CDNG there were flake graphite,crystalline aggregates,and matrix *** crystalline aggregates show the highest structural ordering degree as determined from Raman spectral parameters(full-width at half maxima(G-FWHM)~20 cm^(−1),D1/(D1+D2+G)area ratio(R2)valuestate *** pyrolytic carbon and crystalline tars are the transient phase of gas-state and liquid-state *** study is beneficial to realize the rational utilization of CDNG.

关键词： micro-Raman spectroscopy structural ordering evolution coal-derived natural graphite XRD anthracite

Geochemical characteristics and geological significance of Cretaceous phonotephrite from the Mid-Pacific Mountains

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2018年第6期61卷 745-764页

作者： Shuangshuang CHEN Jiaqi LIU key laboratory of Cenozoic geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences state key laboratory of lithospheric evolution Institute of Geology and Geophysics Chinese Academy of Sciences Institutions of Earth Science Chinese Academy of Sciences

Systematic analyses were conducted including the petrographic features, major and trace elements, Sr and Nd isotopic compositions, and mineral structure and compositions of whole rocks. Mid-Pacific Mountain volcanic rocks are mainly phonotephrite with a porphyritic texture. Phenocrysts are mainly composed of Ca-rich plagioclase, clinopyroxene and *** volcanic rocks are significantly rich in large-ion lithophile and light rare earth elements, without obvious Eu anomalies(δEu=0.99–1.03), and with relatively enriched^(87) Sr/^(86) Sr(0.703829–0.704313) and^(143) Nd/^(144) Nd isotopic ratios(0.512857–0.512871), suggesting that they have similar but more enriched features than the OIB magmatic source. These volcanic rocks may originate from relatively deep magma source with the existence of spinel-garnet Iherzolites, and have undergone partial melting at a low degree of 1–3%. In addition, The residual Nb-Ta minerals(such as sphene, rutile, perovskite) may remain in the mantle source, and the magma components have undergone metasomatism by carbonate melt/fluid or alkali-rich fluid, causing high contents of incompatible elements and significant loss of Nb, Ta and Ti in these volcanic rocks. There are many similarities between the phonotephrites in the Mid-Pacific Mountain and the volcanic rocks in the Line Islands based on the tectonic settings and the geochemical characteristics. We thus speculate that Site 313 volcanic rocks in the Mid-Pacific Mountain is most likely to be a continuation of the Line Islands.

关键词：特征和白垩纪轻稀土元素地质岩浆来源亲石元素交代作用构造背景

Zircon Xenocrysts from the Shaka Ridge Record Ancient Continental Crust:New U-Pb Geochronological and Oxygen Isotopic Data

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2022年第1期33卷 5-16页

作者： Sergey G.Skublov Natalia A.Rumyantseva Qiuli Li Boris G.Vanshtein Dmitriy I.Rezvukhin Xianhua Li institute of Precambrian geology and Geochronology of Russian Academy of Sciences St.Petersburg 199034Russia Saint Petersburg Mining University St.Petersburg 199106Russia institute for geology and Mineral Resources of the World Ocean(VNIIOkeangeologia) St.Petersburg 190121Russia state key laboratory of lithospheric evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Sobolev institute of geology and Mineralogy Siberian Branch of the Russian Academy of SciencesNovosibirsk 630090Russia

Over the past two decades, a significant number of discoveries of ancient zircon xenocrysts in ocean-floor magmatic rocks have been reported. These findings provide compelling evidence for the presence of ancient continental crust within young oceanic lithosphere. Almost all finds of ancient zircon xenocrysts within oceanic crust are from the Mid-Atlantic Ridge. For other localities, however, similar data are very limited. This report presents the first age determinations(U-Pb, SHRIMPII) and isotope-geochemical data(oxygen, trace and rare earth elements) for zircon xenocrysts from gabbro-diorites of the Shaka Ridge, in the vicinity of the Shaka fracture zone, near the western end of the Southwest Indian Ridge. The work is based on a study of bottom rock material dredged during expeditionary research on the R/V"Akademik Fedorov"(Russia) in 2016. The U-Pb isotope system of the zircon xenocrysts recorded a crystallization age of ~2.8 Ga at an upper discordia intercept and an age of ~600 Ma interpreted as the timing of a superimposed thermal event at a lower discordia *** zircon xenocrysts show geochemical signatures of magmatic origin, i.e., fractionated REE distribution spectra with an increase in chondrite-normalized values from light to heavy REE, positive Ce anomalies and negative Eu anomalies, and high Th/U ratios(0.59-7.77). In discrimination diagrams based on a series of inter-element relationships, zircon compositions fall into the fields of zircons from rocks of continental crust, mostly granitoids. The Li content of the zircons is high(1.8 ppm-50 ppm),adding further evidence to their derivation from rocks of continental crust. During their residence within young oceanic crust, the zircon xenocrysts experienced alterations under the influence of submarine high-temperature hydrothermal fluids, which selectively affected the distribution of trace elements in the zircons and reduced the δ;O values to 1.75‰-3.15‰. The presence of obviously older zircons

关键词： zircon U-Pb geochronology oxygen isotopes trace elements rare earth elements Shaka Ridge South Atlantic Southwest Indian Ridge

Reviewing subduction initiation and the origin of plate tectonics:What do we learn from present-day Earth?

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2021年第2期5卷 123-140页

作者： Gang Lu Liang Zhao Ling Chen Bo Wan FuYuan Wu state key laboratory of lithospheric evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

The theory of plate tectonics came together in the 1960s,achieving wide acceptance after *** then it has been the most successful framework for investigations of Earth’s *** of the oceanic lithosphere,as the engine that drives plate tectonics,has played a key role in the ***,one of the biggest unanswered questions in Earth science is how the first subduction was initiated,and hence how plate tectonics *** main challenge is how the strong lithosphere could break and bend if plate tectonics-related weakness and slab-pull force were both *** this work we review state-of-the-art subduction initiation(SI)models with a focus on their prerequisites and related driving *** note that the plume-lithosphere-interaction and mantleconvection models do not rely on the operation of existing plate tectonics and thus may be capable of explaining the first *** of plate-driving mechanisms reveals that mantle drag may be the missing driving force for surface plates,capable of triggering initiation of the first *** propose a composite driving mechanism,suggesting that plate tectonics may be driven by both subducting slabs and convection currents in the *** also discuss and try to answer the following question:Why has plate tectonics been observed only on Earth?

关键词： subduction initiation plate tectonics mantle convection driving force mantle drag

Revisiting Triassic stratigraphy of the Yanshan belt

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2015年第3期58卷 491-501页

作者： WEI HongHong WU GuoLi DUAN Liang key laboratory of Continental Collision and Plateau Uplift Institute of Tibetan Plateau Research Chinese Academy of Sciences state key laboratory of lithospheric evolution Institute of Geology and Geophysics Chinese Academy of Sciences

Age determinations of the Triassic lithostratigraphic units of the Yanshan belt were previously based on plant fossils and regional correlations of lithologies. The Liujiagou and Heshanggou Formations were assigned as the Lower Triassic, and the Ermaying Formation was regarded as the Middle Triassic. We carried out a geochronologic study of detrital zircon grains from the Triassic sandstone in the Xiabancheng and Yingzi basins in northern Hebei where the Triassic strata are exceptionally well preserved. The results show that the Liujiagou, Heshanggou, and Ermaying Formations are all Late Triassic in age. The ages of detrital zircons also revealed that the upper part of the Shihezi Formation and the overlying Sunjiagou Formation, both of which were thought to be the Middle-Late Permian units, are actually late Early to Middle Triassic deposits. This study combines the upper Shihezi and Sunjiagou Formations into a single unit termed as the Yingzi Formation. We also substitute the widely-used Liujiagou, Heshanggou, and Ermaying Formations with the Dingjiagou, Xiabancheng, and Huzhangzi Formations, respectively. Field observations and facies analysis show that the top of the Shihezi Formation is an erosive surface, marking a parallel unconformity between the Middle Permian and Lower Triassic. The Yingzi Formation is composed mainly of meandering river deposits, indicative of tectonic quiescence and low-relief landform in the Early to Middle Triassic. In contrast, the Dingjiagou, Xiabancheng, and Huzhangzi Formations are interpreted as the deposits of sandy/gravelly braided rivers, alluvial fans, fan deltas, and deep lakes in association with volcanism, thus indicating an intense rifting setting. A new Triassic lithostratigraphic division is proposed according to age constraints and facies analysis, and the results are of significance for understanding the early Mesozoic tectonic evolution of the Yanshan belt.

关键词：地层单元三叠系燕山带早中三叠世河流沉积物三叠纪地层年龄测定石盒子组

Carbon isotopes, sulfur isotopes, and trace elements of the dolomites from the Dengying Formation in Zhenba area, southern Shaanxi: Implications for shallow water redox conditions during the terminal Ediacaran

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2015年第7期58卷 1107-1122页

作者： CHEN YaLi CHU XueLei ZHANG XingLiang ZHAI MingGuo state key laboratory of lithospheric evolution Institute of Geology and Geophysics Chinese Academy of Sciences College of Earth Science University of Chinese Academy of Sciences state key laboratory for the Continental Dynamics Northwest University

Carbon isotope, sulfur isotope, and trace element(including Rare Earth Elements, REE) analyses were conducted on the carbonates of the Dengying Formation at Lianghekou section in southern Shaanxi to reconstruct the terminal Ediacaran shallow-water environment on the northwestern margin of the Yangtze Platform. At Lianghekou section, samples in the middle 50-m of the Beiwan Member show characteristics of low ΣREE concentrations, no MREE-enriched REE distribution patterns, high Ce/Ce* values close to 1, and enriched redox-sensitive elements, whereas samples in the lower 30-m and upper 10-m show opposite characteristics of high ∑REE concentrations, MREE-enriched REE distribution patterns, low Ce/Ce* values around 0.6, and no redox-sensitive elements enriched, indicating that oxygenation did occur in the shallow water on the northwestern margin of the Yangtze Platform and redox conditions of the shallow water fluctuated from relatively oxygenated to anoxic and then back to oxygenated again. We propose that the anoxia appeared in middle of the Beiwan time may associate with the anoxic upwelled water. On one hand, abundant nutrients were brought in by this upwelling event, which stimulated the photosynthetic carbon fixation and increased the organic carbon burial under this anoxic condition, causing a peak of 3.6‰ in δ 13 C. On the other hand, because the anoxic upwelled water replaced the oxic shallow water, together with the increasing organic matter in the water column, bacterial sulfate reduction was enhanced and therefore quickly reduced the sulfate concentration, which eventually caused δ 34 S increasing to 50‰. However, as the upwelling gradually disappeared, δ 13 C and δ 34 SCAS values decreased as well in the late Beiwan time, indicating the shallow water went back to suboxic or oxic again.

关键词：氧化还原条件浅水环境微量元素碳同位素陕西南部硫同位素灯影组迪卡

Mantle dynamics of the reactivating North China Craton:Constraints from the topographies of the 410-km and 660-km discontinuities

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2011年第6期54卷 881-887页

作者： XU WeiWei ZHENG TianYu ZHAO Liang Seismological laboratory State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

The topographies of the 410-km and 660-km discontinuities have important implications for mantle *** we present high-resolution seismic imaging of the 410-km and 660-km discontinuities beneath the North China Craton (NCC) employing the receiver function *** anomalies (deeper or shallower than the global average depths) at both discontinuities were detected by introducing a three-dimensional regional velocity *** depressions of the 410-km discontinuity are mostly located in the eastern NCC.A local elevation of the 660-km discontinuity appeared in the northwest of the NCC and a significant depression of the 660-km discontinuity is located in the southeast of the *** dynamic mantle regimes are speculated to explain the formation of the anomalous depth zones in the *** possibility is a complex mantle upwelling linked to edge-derived convection between the stagnant slab and the thick cratonic *** other potential dynamic regime is slab stagnating,sinking,and induced upwelling at the neighboring slab *** regimes hint that the mantle flow was possibly dominated by dynamic interactions among the subducting slab,cratonic root,and ambient mantle beneath the NCC.

关键词：地幔动力学中国北方不连续克拉通公里地形复活厚板坯

The deep background of large-scale,Mesozoic Cu-Au-W metallogenesis in northeastern South China:Constraints from Yingshan-Changshan wide-angle seismic reflection/refraction data

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2022年第11期65卷 2202-2218页

作者： Jue HOU Tao XU Qingtian LV Zhiming BAI Yongqian ZHANG Zhiyu ZHANG Dan YANG state key laboratory of lithospheric evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China China Academy of Geological Sciences Beijing 100037China institute of geophysics China Earthquake AdministrationBeijing 100081China Universityof Chinese Academy of Sciences Bejing 100049China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China institute of geology China Academy of Geological SciencesBeijing 100037China institute of Mineral Resources China Academy of Geological SciencesBeijing 100037China

To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan in *** profile traverses the Cu-Au metallogenic belt in the middle and lower reaches of the Yangtze River(YMB),the Jiangnan W-polymetal metallogenic belt(JNMB),and the Qinhang Cu-polymetal metallogenic belt(QHMB).Our imaging results reveal various interesting velocity features along the profile.(1)The velocity structure is characterized by vertical layering and horizontal blocking;(2)the YMB is marked by high velocity and high V_(p)/V_(s) ratios in general with a significantly uplifted Moho interface and a thin crust of~31 km,and the lower crust contains high-velocity anomalies and has the characteristics of a crustmantle transition zone;(3)the JNMB is bounded by the Jiangnan fault and Jingdezhen-Huangshan fault and has low-velocity anomalies and low V_(p)/V_(s) ratios;and(4)the QHMB is characterized by high-velocity anomalies and high V_(p)/V_(s) *** highvelocity anomalies in the YMB and QHMB represent relatively Cu-Au-rich mafic juvenile lower *** formation of this kind of crust is considered to be related to mantle-derived magma underplating or residues of Neoproterozoic oceanic crustal materials,and it also provided sources for large-scale Cu-Au mineralization in the *** JNMB has features similar to those of ancient crusts enriched in W-Sn,the partial melting of which played a leading role in the formation of the superlarge W deposits in this *** these results and other regional geological data,we propose that a large-scale oblique upwelling of the asthenosphere along the collisional belt of the Yangtze and Cathaysia blocks during the Mesozoic was the deep driving mechanism for the explosive mineralization of Cu,Au,and W in northeastern South *** boundaries of the blocks or terrains and discontinui

关键词： Northeastern South China Metallogenic belt of the middle and lower reaches of the Yangtze River Wide-angle seismic reflection/refraction Yingshan-Changshan seismic profile Crustal velocity structure