The Baishuijiang Group, located in the southwest Qinling orogenic belt, is divided into three belts according to the characteristic of the matrix and rock blocks based on the large scale geological mapping. The north ...The Baishuijiang Group, located in the southwest Qinling orogenic belt, is divided into three belts according to the characteristic of the matrix and rock blocks based on the large scale geological mapping. The north belt and south belt are composed of abyssal mudstone and siltstone, and limestone, chert and basic and ultrabasic rock blocks. The middle belt consists of a few limestone blocks and turbidites, which were formed in the trench environment. At present, in the Baishuijiang Group, many fossils were found in matrix and rock blocks, the fossils contain the Cambrian small shell fossils(Xiao, 1992;Tao et al., 1992), Silurian chitinozoas, scolecodonts and spores, and Ordovician graptolites, and middle Devonian Coral and conodonts in limestone and chert blocks(Wang et al., 2011a), and Permian radiolarians in the matrix(Wang et al., 2007). The volcanic rock blocks have undergone different degree of metamorphism. Their geochemical characteristics indicate that the rocks are similar to oceanic island arc and seamount(Wang et al., 2009), and SHRIMP U-Pb dating yielded ages from Neoproterozoic to early Paleozoic(Yan et al., 2007;Wang et al., 2009, 2011b). Therefore, comprehensive analysis of regional data, the Baishuijiang group is an accretionary complex which was consisted of matrix and blocks, and was finally formed during Permian-Triassic.展开更多
Sensitivity evaluation of rocky desertification is to recognize the areas prone to be rock-deserted,so as to assess the sensitivity degree of rocky desertification to human activities.To perform the sensitivity evalua...Sensitivity evaluation of rocky desertification is to recognize the areas prone to be rock-deserted,so as to assess the sensitivity degree of rocky desertification to human activities.To perform the sensitivity evaluation of rocky desertification,we should be on the basis of the mechanism of rocky desertification formation for analyzing its regional distribution difference in the sensitivity and further for finding out the rocky desertification-susceptive areas and their possible degrees.Employing remote sensing and geological information system techniques,we regarded the 1∶ 50 000 topographic map and the TM image in 2000 of Guizhou Province,together with the hydrologic map,soil map,geologic map,rock formation map,administrative map and other geological information as data sources to generate the degree data of rocky desertification sensitivity of Guizhou Province in 1962 and 2000,based on which we determined the corresponding degree transfer matrix and adopted Markov model to simulate the dynamic change process of rocky desertification sensitivity and its future evolution trend.In various sensitivity types of rocky desertification in Guizhou Province,only the insensitive type showed a declined acreage,from the proportion of total land acreage of 61.35% in 1962 to 55.55% in 2000.Various sensitivity types inter-conversed,resultantly the acreage of mildly sensitive type increased most.The prediction results showed that the acreage of insensitive type of rocky desertification in Guizhou Province will assume a remarkable decline trend,of mildly sensitive type will present a remarkably increasing trend and of slightly sensitive type basically will maintain a stable level in the future tens of years.Acreages of both highly sensitive and extremely sensitive type of rocky desertification expanded to some extent,suggesting that the rocky desertification risk in Guizhou Province is in an aggravating process.展开更多
The Taoudeni Basin is a typical steady intracratonic basin. Based on the distribution of effective source rocks in the Taoudeni Basin, combined with the structure characteristics of the basin and the distribution char...The Taoudeni Basin is a typical steady intracratonic basin. Based on the distribution of effective source rocks in the Taoudeni Basin, combined with the structure characteristics of the basin and the distribution characteristics of reservoir beds, two petroleum systems are recognized in the basin： the infra-Cambrian petroleum system and the Silurian petroleum system. Structural uplift and timing of petroleum generation controlled the timing of petroleum charging and preservation of hydrocarbon accumulations. Maturity, evolution history, and distribution of effective source rocks controlled hydrocarbon richness. The geological key factors and geological processes controlled the type of hydrocarbon accumulations.展开更多
The Nagaland–Manipur Hill ophiolite belt in NE India represents the southern extension of the Neotethyan Yarlung-Zhangbo suture zone in Southern Tibet,and connects this on-land exposure of the late Mesozoic collision...The Nagaland–Manipur Hill ophiolite belt in NE India represents the southern extension of the Neotethyan Yarlung-Zhangbo suture zone in Southern Tibet,and connects this on-land exposure of the late Mesozoic collision front in the north with a modern trench-arc system in the Andaman Sea region in the south.Ophiolitic subunits in the Nagaland–Manipur Hill area in the Indo-Myanmar Ranges occur as blocks or thrust sheets within a mélange with a serpentinite or fine-grained greywacke matrix,and are spatially associated with eclogitic and blueschist rock assemblages.This ophiolitic mélange zone is tectonically sandwiched between an older(Triassic–Cretaceous)accretionary prism complex(Nimi Flysch)to the east and a younger(Late Cretaceous–Miocene)accretionary wedge(Disang Flysch)to the west.The Nagaland–Manipur Hill ophiolitic mélange is thus part of a progressively westward migrated subduction-accretion complex,and it represents a typical subduction channel mélange evolved during the fast subduction of the Neotethyan oceanic lithosphere beneath Asia–Sundaland.展开更多
We present an overview of the internal structure of the ophiolite massifs along the Yarlung Zangbo suture zone(YZSZ)in southern Tibet with a focus on the geochemical character and tectonic evolution of the Ocean Islan...We present an overview of the internal structure of the ophiolite massifs along the Yarlung Zangbo suture zone(YZSZ)in southern Tibet with a focus on the geochemical character and tectonic evolution of the Ocean Island Basalt(OIB)and mafic alkaline rock assemblages associated with these ophiolites.The Jurassic–early Cretaceous lavas,massive diabase and gabbroic rocks are either tectonically intercalated with the early Cretaceous,subduction-influenced ophiolitic units,or occur as thrust sheets or blocks with an early Cretaceous mélange and in a Jurassic-Cretaceous flysch unit structurally beneath these ophiolites.They display uniform chondrite-normalized REE patterns with light rare earth element(LREE)enrichment and heavy rare earth element(HREE)depletion,no obvious Eu anomalies or negative Nb,Ta and Ti anomalies,and primitive mantle normalized trace element patterns with significant large-ion lithophile element(LILE)enrichment,similar to those of modern OIB and the Hawaiian alkaline basalts.These mafic alkaline rock assemblages represent OIB-and Plume-type(P-type)oceanic crustal rocks(with no subduction influence)that formed from magmas produced by partial melting of plume–metasomatized asthenospheric mantle source during the early stages of the opening of a Neotethyan seaway between Proto-India and Eurasia.展开更多
The northern extremity of the late Neoproterozoic-Paleozoic Tasman Orogenic zone exposed in north Queensland forms a narrow belt of tectonised rock assemblages abutting Paleoproterozoic–Mesoproterozoic rocks of the N...The northern extremity of the late Neoproterozoic-Paleozoic Tasman Orogenic zone exposed in north Queensland forms a narrow belt of tectonised rock assemblages abutting Paleoproterozoic–Mesoproterozoic rocks of the North Australian craton.The craton-orogen contact(Tasman Line)is extensively exposed,a unique circumstance for Australia.Sedimentary protoliths of the cratonic rocks were mainly deposited between 1700–1600 Ma and multiply deformed between 1600–1500 Ma.The Lynd Mylonite Zone,one expression of the Tasman Line,separates rocks of the late Neoproterozoic–Ordovician Thomson Orogen from those of the craton.The succeeding Silurian–Devonian Mossman Orogen is generally faulted against the Thomson Orogen,but in its northern extent it may directly abut the craton along the Palmerville Fault,also an expression of the Tasman Line.These two orogenic systems are dominantly of active margin association and E-stepping but deep seismic imaging indicates that they are extensively underlain by crust of Archean or Paleoproterozoic age.The Tasman Orogenic Zone in its southern part represents a broad tract of crust c.1,000 km across,added to the cratonic core of Australia in a phase of rapid accretion.In contrast,for its north Queensland development a much smaller volume of new crust was generated,expressing slow accretion.For this region the orogenic system laps extensively onto cratonic crust,a geometry which at least in part reflects overthusting during episodes of Paleozoic contractional orogenesis.As a consequence of little orogenic accretionary outgrowth of the north Queensland continental margin,three large-scale,successive igneous assemblages of active margin association generated throughout the Paleozoic form largely co-located and overprinting belts with plutonic suites stitching the Tasman Line and extending into the craton.展开更多
Discontinuous deformation analysis （DDA） method, proposed firstly by Shi [1] in 1988, is a novel numerical approach to simulate the discontinuous deformation behaviors of blocky rock structures. In DDA, the domain o...Discontinuous deformation analysis （DDA） method, proposed firstly by Shi [1] in 1988, is a novel numerical approach to simulate the discontinuous deformation behaviors of blocky rock structures. In DDA, the domain of interest is represented as an assemblage of discrete blocks and the joints are treated as interfaces between blocks. The governing equations of DDA are derived from Newton’s Second Law of Motion and the Principle of Minimum Potential Energy.展开更多
基金financially supported by the National Nature Science Foundation of China(Grant No.41772233,41272220)the China Geological Survey(Grant No.DD20189613)grants from the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J1708)
文摘The Baishuijiang Group, located in the southwest Qinling orogenic belt, is divided into three belts according to the characteristic of the matrix and rock blocks based on the large scale geological mapping. The north belt and south belt are composed of abyssal mudstone and siltstone, and limestone, chert and basic and ultrabasic rock blocks. The middle belt consists of a few limestone blocks and turbidites, which were formed in the trench environment. At present, in the Baishuijiang Group, many fossils were found in matrix and rock blocks, the fossils contain the Cambrian small shell fossils(Xiao, 1992;Tao et al., 1992), Silurian chitinozoas, scolecodonts and spores, and Ordovician graptolites, and middle Devonian Coral and conodonts in limestone and chert blocks(Wang et al., 2011a), and Permian radiolarians in the matrix(Wang et al., 2007). The volcanic rock blocks have undergone different degree of metamorphism. Their geochemical characteristics indicate that the rocks are similar to oceanic island arc and seamount(Wang et al., 2009), and SHRIMP U-Pb dating yielded ages from Neoproterozoic to early Paleozoic(Yan et al., 2007;Wang et al., 2009, 2011b). Therefore, comprehensive analysis of regional data, the Baishuijiang group is an accretionary complex which was consisted of matrix and blocks, and was finally formed during Permian-Triassic.
基金Supported by Programs for Science and Technology Development of Guizhou Province(20073017,20083022)National Basic Research Program of China(973Program,2006CB403200)~~
文摘Sensitivity evaluation of rocky desertification is to recognize the areas prone to be rock-deserted,so as to assess the sensitivity degree of rocky desertification to human activities.To perform the sensitivity evaluation of rocky desertification,we should be on the basis of the mechanism of rocky desertification formation for analyzing its regional distribution difference in the sensitivity and further for finding out the rocky desertification-susceptive areas and their possible degrees.Employing remote sensing and geological information system techniques,we regarded the 1∶ 50 000 topographic map and the TM image in 2000 of Guizhou Province,together with the hydrologic map,soil map,geologic map,rock formation map,administrative map and other geological information as data sources to generate the degree data of rocky desertification sensitivity of Guizhou Province in 1962 and 2000,based on which we determined the corresponding degree transfer matrix and adopted Markov model to simulate the dynamic change process of rocky desertification sensitivity and its future evolution trend.In various sensitivity types of rocky desertification in Guizhou Province,only the insensitive type showed a declined acreage,from the proportion of total land acreage of 61.35% in 1962 to 55.55% in 2000.Various sensitivity types inter-conversed,resultantly the acreage of mildly sensitive type increased most.The prediction results showed that the acreage of insensitive type of rocky desertification in Guizhou Province will assume a remarkable decline trend,of mildly sensitive type will present a remarkably increasing trend and of slightly sensitive type basically will maintain a stable level in the future tens of years.Acreages of both highly sensitive and extremely sensitive type of rocky desertification expanded to some extent,suggesting that the rocky desertification risk in Guizhou Province is in an aggravating process.
文摘The Taoudeni Basin is a typical steady intracratonic basin. Based on the distribution of effective source rocks in the Taoudeni Basin, combined with the structure characteristics of the basin and the distribution characteristics of reservoir beds, two petroleum systems are recognized in the basin： the infra-Cambrian petroleum system and the Silurian petroleum system. Structural uplift and timing of petroleum generation controlled the timing of petroleum charging and preservation of hydrocarbon accumulations. Maturity, evolution history, and distribution of effective source rocks controlled hydrocarbon richness. The geological key factors and geological processes controlled the type of hydrocarbon accumulations.
文摘The Nagaland–Manipur Hill ophiolite belt in NE India represents the southern extension of the Neotethyan Yarlung-Zhangbo suture zone in Southern Tibet,and connects this on-land exposure of the late Mesozoic collision front in the north with a modern trench-arc system in the Andaman Sea region in the south.Ophiolitic subunits in the Nagaland–Manipur Hill area in the Indo-Myanmar Ranges occur as blocks or thrust sheets within a mélange with a serpentinite or fine-grained greywacke matrix,and are spatially associated with eclogitic and blueschist rock assemblages.This ophiolitic mélange zone is tectonically sandwiched between an older(Triassic–Cretaceous)accretionary prism complex(Nimi Flysch)to the east and a younger(Late Cretaceous–Miocene)accretionary wedge(Disang Flysch)to the west.The Nagaland–Manipur Hill ophiolitic mélange is thus part of a progressively westward migrated subduction-accretion complex,and it represents a typical subduction channel mélange evolved during the fast subduction of the Neotethyan oceanic lithosphere beneath Asia–Sundaland.
基金supported by the National Nature Science Foundation of China(41303027)Special Fund for Basic Scientific Research of Central Colleges,Chang’an University(310827153506,310827153407)to G.-X.Yang.Y.Dilek’s research in Tibet and on the Yarlung-Zangbo suture zone ophiolites has been funded by the Chinese Academy of Geological Sciences(Beijing,China).
文摘We present an overview of the internal structure of the ophiolite massifs along the Yarlung Zangbo suture zone(YZSZ)in southern Tibet with a focus on the geochemical character and tectonic evolution of the Ocean Island Basalt(OIB)and mafic alkaline rock assemblages associated with these ophiolites.The Jurassic–early Cretaceous lavas,massive diabase and gabbroic rocks are either tectonically intercalated with the early Cretaceous,subduction-influenced ophiolitic units,or occur as thrust sheets or blocks with an early Cretaceous mélange and in a Jurassic-Cretaceous flysch unit structurally beneath these ophiolites.They display uniform chondrite-normalized REE patterns with light rare earth element(LREE)enrichment and heavy rare earth element(HREE)depletion,no obvious Eu anomalies or negative Nb,Ta and Ti anomalies,and primitive mantle normalized trace element patterns with significant large-ion lithophile element(LILE)enrichment,similar to those of modern OIB and the Hawaiian alkaline basalts.These mafic alkaline rock assemblages represent OIB-and Plume-type(P-type)oceanic crustal rocks(with no subduction influence)that formed from magmas produced by partial melting of plume–metasomatized asthenospheric mantle source during the early stages of the opening of a Neotethyan seaway between Proto-India and Eurasia.
文摘The northern extremity of the late Neoproterozoic-Paleozoic Tasman Orogenic zone exposed in north Queensland forms a narrow belt of tectonised rock assemblages abutting Paleoproterozoic–Mesoproterozoic rocks of the North Australian craton.The craton-orogen contact(Tasman Line)is extensively exposed,a unique circumstance for Australia.Sedimentary protoliths of the cratonic rocks were mainly deposited between 1700–1600 Ma and multiply deformed between 1600–1500 Ma.The Lynd Mylonite Zone,one expression of the Tasman Line,separates rocks of the late Neoproterozoic–Ordovician Thomson Orogen from those of the craton.The succeeding Silurian–Devonian Mossman Orogen is generally faulted against the Thomson Orogen,but in its northern extent it may directly abut the craton along the Palmerville Fault,also an expression of the Tasman Line.These two orogenic systems are dominantly of active margin association and E-stepping but deep seismic imaging indicates that they are extensively underlain by crust of Archean or Paleoproterozoic age.The Tasman Orogenic Zone in its southern part represents a broad tract of crust c.1,000 km across,added to the cratonic core of Australia in a phase of rapid accretion.In contrast,for its north Queensland development a much smaller volume of new crust was generated,expressing slow accretion.For this region the orogenic system laps extensively onto cratonic crust,a geometry which at least in part reflects overthusting during episodes of Paleozoic contractional orogenesis.As a consequence of little orogenic accretionary outgrowth of the north Queensland continental margin,three large-scale,successive igneous assemblages of active margin association generated throughout the Paleozoic form largely co-located and overprinting belts with plutonic suites stitching the Tasman Line and extending into the craton.
文摘Discontinuous deformation analysis （DDA） method, proposed firstly by Shi [1] in 1988, is a novel numerical approach to simulate the discontinuous deformation behaviors of blocky rock structures. In DDA, the domain of interest is represented as an assemblage of discrete blocks and the joints are treated as interfaces between blocks. The governing equations of DDA are derived from Newton’s Second Law of Motion and the Principle of Minimum Potential Energy.
