The study of deep-seated structure in the Zhangbei-Shangyi earthquake area and its surroundings indicates that in comparison with the Shanxi rift system, the North China rifted basin, the Yanshanian fold belt on both ...The study of deep-seated structure in the Zhangbei-Shangyi earthquake area and its surroundings indicates that in comparison with the Shanxi rift system, the North China rifted basin, the Yanshanian fold belt on both sides, and the Zhangjiakou-Penglai tectonic belt have lower resistivity, and a distinctly different velocity interface in the crust and depth distribution of Moho discontinuity. The Yanqing- Huai’lai basin bisects the Zhangjiakou-Penglai tectonic belt into two segments, the northwestern and the southeastern segments. The latest magnetotelluric sounding and investigation indicate that the electrical structure within the Zhangbei-Shangyi earthquake area is different to a certain degree from that in its surroundings. There exists a nearly NNW-trending structure in the crust. The main shock and most aftershocks occurred above the low-resistivity zone in the crust.展开更多
An analysis of trace elements and isotopic geochemistry suggest that the ore-forming materials of gold deposits in the Jiaodong granite-greenstone belt have multiple sources, especially the mantle source. Seismic wave...An analysis of trace elements and isotopic geochemistry suggest that the ore-forming materials of gold deposits in the Jiaodong granite-greenstone belt have multiple sources, especially the mantle source. Seismic wave, magnetic and gravity fields show that the crust-mantle structure and its coupling mechanism are the fundamental dynamic causes for the exchange and accumulation of materials and energy in the metallogenic system. Considering the evolution history of the structural setting, the tectono-metallogenic dynamics model of the area can be summarized as follows: (1) occurrence of the greenstone belt during the Archean-Proterozoic-the embryonic form of Au-source system; (2) stable tectonic setting in the Paleozoic-an intermittence in gold mineralization; (3) intensive activation and reformation of the greenstone belt in the Mesozoic-tectono-mineralization and tectono-diagensis; (4) posthumous structural activity in the Cenozoic-destruction of orebodies in the later stage. In the middle and late Indosinian, the Tancheng-Lujiang fault zone cut deeply into the upper mantle so that the ore-bearing fluids migrated to higher layers through the crust-mantle interaction, resulting in alteration and mineralization.展开更多
It has been suggested that eclogites in the Dabie orogenic be lt are exhumation products, which had subducted into the deep-seated mantle and undergone ultra-high pressure metamorphism during the Triassic. But no dire...It has been suggested that eclogites in the Dabie orogenic be lt are exhumation products, which had subducted into the deep-seated mantle and undergone ultra-high pressure metamorphism during the Triassic. But no direct evidence supports this process except the calculated p-T conditions from mineral thermobarometers. The Late Cretaceous basalts studied in the prese nt paper, however, have provided some geochemical evidence for crust-mantle int eraction in the area. These basalts are distributed in Mesozoic faulted basins i n central and southern Dabie orogenic belt. Since little obvious contamination f rom continental crust and differentiation-crystallization were observed, it is suggested, based on a study of trace elements, that the basalts are alkaline and resultant from batch partial melting of the regional mantle rocks, and share th e same or similar geochemical features with respect to their magma source. In th e spider diagram normalized by the primitive mantle, trace element geochemistry data show that their mantle sources are enriched in certain elements concentrate d in the continental crust, such as Pb, K, Rb and Ba, and slightly depleted in s ome HFSE such as Hf, P and Nb. Pb-Sr-Nd isotopic compositions further suggest the mantle is the mixture of depleted mantle and enriched one . T his interaction can explain the trace element characteristics of basaltic magmas , i.e., the enrichment of Pb and the depletion of Hf, P and Nb in basalts can be interpreted by the blending of the eclogites in DOB (enriched in Pb and deplete d in Hf, P and Nd) with the East China depleted mantle (As compared to the primi tive mantle, it is neither enriched in Pb nor depleted in Hf, P and Nb). It is a lso indicated that the eclogites in the Dabie orogenic belt were surely derived from the exhumation materials, which had delaminated into the deep-seated mantl e. Moreover, the process subsequently resulted in compositional variation of the mantle (especially in trace elements and isotopes), as revealed by the late man tle-derived basalts in the Dabie orogenic belt.展开更多
The Hongdonggou Pb-Zn polymetallic ore deposit, located in the southwestern part of the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore mineralization in Henan Province, China, is an important part of the East Qinling metall...The Hongdonggou Pb-Zn polymetallic ore deposit, located in the southwestern part of the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore mineralization in Henan Province, China, is an important part of the East Qinling metallogenic belt. The orebodies in the deposit, which are vein, bedded and lenticular, are mainly hosted in the syenite porphyry, and formed within the carbonate and clastic rocks of the Yuku and Qiumugou formations partially. The genesis of the deposit has previously been argued to be of hydrothermal-vein type or of skarn-hydrothermal type. In this study, we report the results of Rb-Sr isotopic dating based on sphalerites from the main orebody of the Hongdonggou Pb-Zn polymetallic ore deposit, which yield an isochron age of 135.7 ± 3.2 Ma, constraining the timing of mineralization as early Cretaceous. The age is close to those reported for the Pb-Zn deposits in the Luanchuan ore belt. The （87Sr/86Sr）i values of the sphalerites （0.71127± 0.00010） are lower than that of terrigenous silicates （0.720） and higher than the mantle （0.707）, suggesting that the metallogenic components were mainly derived through crust-mantle mixing. Combining the results from this study with those from previous work, we propose that the Hongdonggou Pb-Zn polymetallic ore deposit is a hydrothermal-vein deposit associated with the early Cretaceous tectonothermal event, and the mineralization is controlled by NW- and near EW-trending faults in the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore concentration belt.展开更多
From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China...From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. Among them, 51 stations make up an about 500-km-long profile across the Tianshan Mountains from Kuytun to Kuqa. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km deep are obtained by using the re-ceiver function method (Liu et al. 1996, 2000). The main results can be summarized as follows: (1) A clear mountain root does not exist beneath the Tianshan Mountains, and the crust-mantle boundaries underneath the stations mostly have transitional structures. This implies that the material differentia-tion between the crust and mantle is not yet accomplished and the orogenic process is still going on. (2) The crust beneath the Tianshan Mountains has laterally blocked structures in direction perpendicular to the mountain strike, and the crust-mantle boundary has a clear dislocation structure. Both of them correspond to each other. (3) The offsets of the Moho discontinuity are highly correlated to the tectonic borders on the surface and that corresponding to the frontal southern Tianshan fault reaches to 14 km. This manifests that large vertical divergent movement took place between different blocks. This sup-ports the discontinuous model of the Tianshan orogeny, and the Tarim block subduction is restricted only to the southern side of the South Tianshan. (4) Inside the upper and middle crust of the Tianshan Mountains exist several low-velocity bodies correlated with high seismicity located on the moun-tain-basin jointures on both sides of the mountain and between different blocks, and the low-velocity bodies on the mountain-basin jointures are inclined obviously to the mountain. This implies that the low-velocity bodies may be correlated closely to the thrust and subduction of the basins on both sides of the mountain, the splicing of adjacent blocks and the fast uplift of the Tianshan Mountains.展开更多
Sulphide inclusions, which represent melts trapped in the minerals of magmatic rocks and xenoliths, provide important clues to the behaviour of immiscible sulphide liquids during the evolution of magmas and the format...Sulphide inclusions, which represent melts trapped in the minerals of magmatic rocks and xenoliths, provide important clues to the behaviour of immiscible sulphide liquids during the evolution of magmas and the formation of NieCueFe deposits. We describe sulphide inclusions from unique ultramafic clots within mafic xenoliths, from the mafic xenoliths themselves, and from the three silica-rich host plutons in Tongling, China. For the first time, we are able to propose a general framework model for the evolution of sulphide melts during the evolution of mafic to felsic magmas from the upper mantle to the upper crust. The model improves our understanding of the sulphide melt evolution in upper mantle to upper crust magmas, and provides insight into the formation of stratabound skarn-type FeeCu polymetallic deposits associated with felsic magmatism, thus promising to play an important role during prospecting for such deposits.展开更多
Geological, geophysical and geochemical evidence for lower crustal delamination in the Qinling-Dabie oro-genic belt is presented and a chemical geodynamic model for lower crustal delamination is developed. The synthet...Geological, geophysical and geochemical evidence for lower crustal delamination in the Qinling-Dabie oro-genic belt is presented and a chemical geodynamic model for lower crustal delamination is developed. The synthetic results suggest that eclogite from the Dabie-Sulu ultrahigh pressure metamorphic belt is the most likely candidate as the de-laminated material, and that a cumulative 37-82 km thick eclogitic lower crust is required to have been delaminated in order to explain the relative deficits in Eu, Sr, Cr, Ni, Co, V and Ti in the present total crust composition of the Qin-ling-Dabie orogenic belt. Delamination of the lower crust can well interpret many geological, geophysical and geochemical characteristics of the belt.展开更多
It has long been debated that the Dabie orogenic belt belongs to the North China or Yangtze craton. In recent years, eastern China has been suggested, based on the Pb isotopic compositions of Phanerozoic ore and Mesoz...It has long been debated that the Dabie orogenic belt belongs to the North China or Yangtze craton. In recent years, eastern China has been suggested, based on the Pb isotopic compositions of Phanerozoic ore and Mesozoic granitoid K-feldspar (revealing the crust Pb) in combination with Meso-Cenozoic basalts (revealing the mantle Pb), being divided into the North China and Yangtze Pb isotopic provinces, where the crust and mantle of the Yangtze craton are characterized by more radiogenic Pb. In this sense, previous researchers suggested that the pro-EW-trending Dabie orogenic belt with less radiogenic Pb in the crust was part of the North China craton. In this paper, however, the Late Cretaceous basalts in the central and southern parts of the Dabie orogenic belt are characterized by some more radiogenic Pb (\{\{\}\+\{206\}Pb\}/\{\{\}\+\{204\}Pb\}=\{17.936\}-\{18.349\}, \{\{\}\+\{207\}Pb\}/\{\{\}\+\{204\}Pb\}=\{15.500\}-\{15.688\}, \{\{\}\+\{208\}Pb\}/\{\{\}\+\{204\}Pb\}=\{38.399\}-\{38.775\}) and a unique U-Th-Pb trace element system similar to those of the Yangtze craton, showing that the Mesozoic mantle is of the Yangtze type. In addition, the decoupled Pb isotopic compositions between crust and mantle were considerably derived from their rheological inhomogeneity, implying a complicated evolution of the Dabie orogenic belt.展开更多
燕山造山带中生代发育4期钙碱性火山活动,它们的源区组成都是受壳幔相互作用的制约,其中髫髻山组和义县组分布广泛,具有代表性．髫髻山组岩性比较单一,地球化学参数变化范围小,岩浆的AFC作用不强烈,源区成分不复杂．依据Kay et al．(19...燕山造山带中生代发育4期钙碱性火山活动,它们的源区组成都是受壳幔相互作用的制约,其中髫髻山组和义县组分布广泛,具有代表性．髫髻山组岩性比较单一,地球化学参数变化范围小,岩浆的AFC作用不强烈,源区成分不复杂．依据Kay et al．(1991)的方法,估算了早-中侏罗世燕山地区的地壳厚度为40-45 km.髫髻山组粗安岩是在加厚的地壳 (40-45 km)条件下,源区是含角闪石的石榴石麻粒岩+底侵的基性岩的壳幔过渡带熔融形成．义县组火山岩的源区为下地壳+岩石圈地幔,地幔组分较髫髻山组增加．研究区中生代早期地壳开始加厚,发生下地壳拆沉,进入流变学性质改变了的“弱化的岩石圈地幔”,二者发生作用．岩石圈地幔在中生代晚期受到流体、熔体、地幔矿物中活化的分子水、剪切构造作用,以及温、压条件改变的影响,导致岩石圈地幔发生不均一的局部弱化,为容纳拆沉的下地壳提供了优化场所．推测弱化岩石圈地幔出现于135 Ma以后燕山地区发育的小型拉伸盆地之下,以及对应的小型软流圈底辟体之上．上述模型可以与俯冲带的楔形地幔与俯冲洋壳的相互作用相对比．展开更多
基金The research is supported by the China Seismological Bureau as a key project during the Eighth Five-Year Plan of NEC (859070203) and the National Natural Science Foundation grant No.49374205. Contribution No.98B0017, Institute of Geology, CSB.
文摘The study of deep-seated structure in the Zhangbei-Shangyi earthquake area and its surroundings indicates that in comparison with the Shanxi rift system, the North China rifted basin, the Yanshanian fold belt on both sides, and the Zhangjiakou-Penglai tectonic belt have lower resistivity, and a distinctly different velocity interface in the crust and depth distribution of Moho discontinuity. The Yanqing- Huai’lai basin bisects the Zhangjiakou-Penglai tectonic belt into two segments, the northwestern and the southeastern segments. The latest magnetotelluric sounding and investigation indicate that the electrical structure within the Zhangbei-Shangyi earthquake area is different to a certain degree from that in its surroundings. There exists a nearly NNW-trending structure in the crust. The main shock and most aftershocks occurred above the low-resistivity zone in the crust.
基金This study is supported jointly by the National Natural Science Foundation of China(No.40172036)"the Key Project of Science and Technology Research"(No.01037)+1 种基金the“Trans-century Training Program for Outstanding Talents”Fund sponsored by the Ministry of Educationthe National Important Basic Research and Development Planning Program(No.1999043206).
文摘An analysis of trace elements and isotopic geochemistry suggest that the ore-forming materials of gold deposits in the Jiaodong granite-greenstone belt have multiple sources, especially the mantle source. Seismic wave, magnetic and gravity fields show that the crust-mantle structure and its coupling mechanism are the fundamental dynamic causes for the exchange and accumulation of materials and energy in the metallogenic system. Considering the evolution history of the structural setting, the tectono-metallogenic dynamics model of the area can be summarized as follows: (1) occurrence of the greenstone belt during the Archean-Proterozoic-the embryonic form of Au-source system; (2) stable tectonic setting in the Paleozoic-an intermittence in gold mineralization; (3) intensive activation and reformation of the greenstone belt in the Mesozoic-tectono-mineralization and tectono-diagensis; (4) posthumous structural activity in the Cenozoic-destruction of orebodies in the later stage. In the middle and late Indosinian, the Tancheng-Lujiang fault zone cut deeply into the upper mantle so that the ore-bearing fluids migrated to higher layers through the crust-mantle interaction, resulting in alteration and mineralization.
文摘It has been suggested that eclogites in the Dabie orogenic be lt are exhumation products, which had subducted into the deep-seated mantle and undergone ultra-high pressure metamorphism during the Triassic. But no direct evidence supports this process except the calculated p-T conditions from mineral thermobarometers. The Late Cretaceous basalts studied in the prese nt paper, however, have provided some geochemical evidence for crust-mantle int eraction in the area. These basalts are distributed in Mesozoic faulted basins i n central and southern Dabie orogenic belt. Since little obvious contamination f rom continental crust and differentiation-crystallization were observed, it is suggested, based on a study of trace elements, that the basalts are alkaline and resultant from batch partial melting of the regional mantle rocks, and share th e same or similar geochemical features with respect to their magma source. In th e spider diagram normalized by the primitive mantle, trace element geochemistry data show that their mantle sources are enriched in certain elements concentrate d in the continental crust, such as Pb, K, Rb and Ba, and slightly depleted in s ome HFSE such as Hf, P and Nb. Pb-Sr-Nd isotopic compositions further suggest the mantle is the mixture of depleted mantle and enriched one . T his interaction can explain the trace element characteristics of basaltic magmas , i.e., the enrichment of Pb and the depletion of Hf, P and Nb in basalts can be interpreted by the blending of the eclogites in DOB (enriched in Pb and deplete d in Hf, P and Nd) with the East China depleted mantle (As compared to the primi tive mantle, it is neither enriched in Pb nor depleted in Hf, P and Nb). It is a lso indicated that the eclogites in the Dabie orogenic belt were surely derived from the exhumation materials, which had delaminated into the deep-seated mantl e. Moreover, the process subsequently resulted in compositional variation of the mantle (especially in trace elements and isotopes), as revealed by the late man tle-derived basalts in the Dabie orogenic belt.
基金supported by the National Science and Technology Support Project of the 12th"Five-Year Plan"(Grant No.2011BAB04B06)the Fundamental Research Funds for the Central Universities of China University of Geosciences,Beijing(Grant No.2-9-2012-143)the National Natural Science Foundation of China(Grant No.41572318)
文摘The Hongdonggou Pb-Zn polymetallic ore deposit, located in the southwestern part of the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore mineralization in Henan Province, China, is an important part of the East Qinling metallogenic belt. The orebodies in the deposit, which are vein, bedded and lenticular, are mainly hosted in the syenite porphyry, and formed within the carbonate and clastic rocks of the Yuku and Qiumugou formations partially. The genesis of the deposit has previously been argued to be of hydrothermal-vein type or of skarn-hydrothermal type. In this study, we report the results of Rb-Sr isotopic dating based on sphalerites from the main orebody of the Hongdonggou Pb-Zn polymetallic ore deposit, which yield an isochron age of 135.7 ± 3.2 Ma, constraining the timing of mineralization as early Cretaceous. The age is close to those reported for the Pb-Zn deposits in the Luanchuan ore belt. The （87Sr/86Sr）i values of the sphalerites （0.71127± 0.00010） are lower than that of terrigenous silicates （0.720） and higher than the mantle （0.707）, suggesting that the metallogenic components were mainly derived through crust-mantle mixing. Combining the results from this study with those from previous work, we propose that the Hongdonggou Pb-Zn polymetallic ore deposit is a hydrothermal-vein deposit associated with the early Cretaceous tectonothermal event, and the mineralization is controlled by NW- and near EW-trending faults in the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore concentration belt.
基金the National Natural Science Foundation of China (Grant No.40234043)
文摘From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. Among them, 51 stations make up an about 500-km-long profile across the Tianshan Mountains from Kuytun to Kuqa. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km deep are obtained by using the re-ceiver function method (Liu et al. 1996, 2000). The main results can be summarized as follows: (1) A clear mountain root does not exist beneath the Tianshan Mountains, and the crust-mantle boundaries underneath the stations mostly have transitional structures. This implies that the material differentia-tion between the crust and mantle is not yet accomplished and the orogenic process is still going on. (2) The crust beneath the Tianshan Mountains has laterally blocked structures in direction perpendicular to the mountain strike, and the crust-mantle boundary has a clear dislocation structure. Both of them correspond to each other. (3) The offsets of the Moho discontinuity are highly correlated to the tectonic borders on the surface and that corresponding to the frontal southern Tianshan fault reaches to 14 km. This manifests that large vertical divergent movement took place between different blocks. This sup-ports the discontinuous model of the Tianshan orogeny, and the Tarim block subduction is restricted only to the southern side of the South Tianshan. (4) Inside the upper and middle crust of the Tianshan Mountains exist several low-velocity bodies correlated with high seismicity located on the moun-tain-basin jointures on both sides of the mountain and between different blocks, and the low-velocity bodies on the mountain-basin jointures are inclined obviously to the mountain. This implies that the low-velocity bodies may be correlated closely to the thrust and subduction of the basins on both sides of the mountain, the splicing of adjacent blocks and the fast uplift of the Tianshan Mountains.
基金financially supported by the China Geological Survey (Grant No. 12120113069900)the National Natural Science Foundation of China (Grant No. 40672045)
文摘Sulphide inclusions, which represent melts trapped in the minerals of magmatic rocks and xenoliths, provide important clues to the behaviour of immiscible sulphide liquids during the evolution of magmas and the formation of NieCueFe deposits. We describe sulphide inclusions from unique ultramafic clots within mafic xenoliths, from the mafic xenoliths themselves, and from the three silica-rich host plutons in Tongling, China. For the first time, we are able to propose a general framework model for the evolution of sulphide melts during the evolution of mafic to felsic magmas from the upper mantle to the upper crust. The model improves our understanding of the sulphide melt evolution in upper mantle to upper crust magmas, and provides insight into the formation of stratabound skarn-type FeeCu polymetallic deposits associated with felsic magmatism, thus promising to play an important role during prospecting for such deposits.
基金Project cosupported by the National Nature Science Foundation of China (Grant Nos. 49625305, 49573183, 49794043, 49672144)the Ministry of Education of China, the Open Laboratory of Constitution.
文摘Geological, geophysical and geochemical evidence for lower crustal delamination in the Qinling-Dabie oro-genic belt is presented and a chemical geodynamic model for lower crustal delamination is developed. The synthetic results suggest that eclogite from the Dabie-Sulu ultrahigh pressure metamorphic belt is the most likely candidate as the de-laminated material, and that a cumulative 37-82 km thick eclogitic lower crust is required to have been delaminated in order to explain the relative deficits in Eu, Sr, Cr, Ni, Co, V and Ti in the present total crust composition of the Qin-ling-Dabie orogenic belt. Delamination of the lower crust can well interpret many geological, geophysical and geochemical characteristics of the belt.
基金ThestudywasfundedbytheNationalNaturalScienceFoundationofChina (No .497940 43)andtheOpenLaboratoryofCon stitution ,InteractionandDynamicsoftheCrust MantleSystem China .
文摘It has long been debated that the Dabie orogenic belt belongs to the North China or Yangtze craton. In recent years, eastern China has been suggested, based on the Pb isotopic compositions of Phanerozoic ore and Mesozoic granitoid K-feldspar (revealing the crust Pb) in combination with Meso-Cenozoic basalts (revealing the mantle Pb), being divided into the North China and Yangtze Pb isotopic provinces, where the crust and mantle of the Yangtze craton are characterized by more radiogenic Pb. In this sense, previous researchers suggested that the pro-EW-trending Dabie orogenic belt with less radiogenic Pb in the crust was part of the North China craton. In this paper, however, the Late Cretaceous basalts in the central and southern parts of the Dabie orogenic belt are characterized by some more radiogenic Pb (\{\{\}\+\{206\}Pb\}/\{\{\}\+\{204\}Pb\}=\{17.936\}-\{18.349\}, \{\{\}\+\{207\}Pb\}/\{\{\}\+\{204\}Pb\}=\{15.500\}-\{15.688\}, \{\{\}\+\{208\}Pb\}/\{\{\}\+\{204\}Pb\}=\{38.399\}-\{38.775\}) and a unique U-Th-Pb trace element system similar to those of the Yangtze craton, showing that the Mesozoic mantle is of the Yangtze type. In addition, the decoupled Pb isotopic compositions between crust and mantle were considerably derived from their rheological inhomogeneity, implying a complicated evolution of the Dabie orogenic belt.
