Time filter

Source Type

Jiang Z.,Chinese Academy of Geological Sciences | Lian Y.,University of Illinois at Urbana - Champaign | Qin X.,Chinese Academy of Geological Sciences
Earth-Science Reviews | Year: 2014

Rocky desertification, which is relatively less well known than desertification, refers to the processes and human activities that transform a karst area covered by vegetation and soil into a rocky landscape. It has occurred in various countries and regions, including the European Mediterranean and Dinaric Karst regions of the Balkan Peninsula, Southwest China on a large scale, and alarmingly, even in tropical rainforests such as Haiti and Barbados, and has had tremendous negative impacts to the environment and social and economic conditions at local and regional scales. The goal of this paper is to provide a thorough review of the impacts, causes, and restoration measures of rocky desertification based on decades of studies in the southwest karst area of China and reviews of studies in Europe and other parts of the world. The low soil formation rate and high permeability of carbonate rocks create a fragile and vulnerable environment that is susceptible to deforestation and soil erosion. Other natural processes related to hydrology and ecology could exacerbate rocky desertification. However, disturbances from a wide variety of human activities are ultimately responsible for rocky desertification wherever it has occurred. This review shows that reforestation can be successful in Southwest China and even in the Dinaric Karst region when the land, people, water, and other resources are managed cohesively. However, new challenges may arise as more frequent droughts and extreme floods induced by global climate change and variability may slow the recovery process or even expand rocky desertification. This review is intended to bring attention to this challenging issue and provide information needed to advance research and engineering practices to combat rocky desertification and to aid in sustainable development. © 2014 Elsevier B.V.


Condie K.C.,New Mexico Institute of Mining and Technology | Kroner A.,University Mainz | Kroner A.,Chinese Academy of Geological Sciences
Gondwana Research | Year: 2013

Oceanic arcs are commonly cited as primary building blocks of continents, yet modern oceanic arcs are mostly subducted. Also, lithosphere buoyancy considerations show that oceanic arcs (even those with a felsic component) should readily subduct. With the exception of the Arabian-Nubian orogen, terranes in post-Archean accretionary orogens comprise < 10% of accreted oceanic arcs, whereas continental arcs compose 40-80% of these orogens. Nd and Hf isotopic data suggest that accretionary orogens include 40-65% juvenile crustal components, with most of these (> 50%) produced in continental arcs. Felsic igneous rocks in oceanic arcs are depleted in incompatible elements compared to average continental crust and to felsic igneous rocks from continental arcs. They have lower Th/Yb, Nb/Yb, Sr/Y and La/Yb ratios, reflecting shallow mantle sources in which garnet did not exist in the restite during melting. The bottom line of these geochemical differences is that post-Archean continental crust does not begin life in oceanic arcs. On the other hand, the remarkable similarity of incompatible element distributions in granitoids and felsic volcanics from continental arcs is consistent with continental crust being produced in continental arcs. During the Archean, however, oceanic arcs may have been thicker due to higher degrees of melting in the mantle, and oceanic lithosphere would be more buoyant. These arcs may have accreted to each other and to oceanic plateaus, a process that eventually led to the production of Archean continental crust. After the Archean, oceanic crust was thinner due to cooling of the mantle and less melt production at ocean ridges, hence, oceanic lithosphere is more subductable. Widespread propagation of plate tectonics in the late Archean may have led not only to rapid production of continental crust, but to a change in the primary site of production of continental crust, from accreted oceanic arcs and oceanic plateaus in the Archean to primarily continental arcs thereafter. © 2011 International Association for Gondwana Research.


News Article | September 9, 2016
Site: www.chromatographytechniques.com

Earth requires fuel to drive plate tectonics, volcanoes and its magnetic field. Like a hybrid car, Earth taps two sources of energy to run its engine: primordial energy from assembling the planet and nuclear energy from the heat produced during natural radioactive decay. Scientists have developed numerous models to predict how much fuel remains inside Earth to drive its engines -- and estimates vary widely -- but the true amount remains unknown. In a new paper, a team of geologists and neutrino physicists boldly claims it will be able to determine by 2025 how much nuclear fuel and radioactive power remain in the Earth's tank. The study, authored by scientists from the University of Maryland, Charles University in Prague and the Chinese Academy of Geological Sciences, was published on September 9 in the journal Nature Scientific Reports. "I am one of those scientists who has created a compositional model of the Earth and predicted the amount of fuel inside Earth today," said one of the study's authors William McDonough, a professor of geology at the University of Maryland. "We're in a field of guesses. At this point in my career, I don't care if I'm right or wrong, I just want to know the answer." To calculate the amount of fuel inside Earth by 2025, the researchers will rely on detecting some of the tiniest subatomic particles known to science -- geoneutrinos. These antineutrino particles are byproducts of nuclear reactions within stars (including our sun), supernovae, black holes and human-made nuclear reactors. They also result from radioactive decay processes deep within the Earth. Detecting antineutrinos requires a huge detector the size of a small office building, housed about a mile underground to shield it from cosmic rays that could yield false positive results. Inside the detector, scientists detect antineutrinos when they crash into a hydrogen atom. The collision produces two characteristic light flashes that unequivocally announce the event. The number of events scientists detect relates directly to the number of atoms of uranium and thorium inside the Earth. And the decay of these elements, along with potassium, fuels the vast majority of the heat in the Earth's interior. To date, detecting antineutrinos has been painfully slow, with scientists recording only about 16 events per year from the underground detectors KamLAND in Japan and Borexino in Italy. However, researchers predict that three new detectors expected to come online by 2022--the SNO+ detector in Canada and the Jinping and JUNO detectors in China--will add 520 more events per year to the data stream. "Once we collect three years of antineutrino data from all five detectors, we are confident that we will have developed an accurate fuel gauge for the Earth and be able to calculate the amount of remaining fuel inside Earth," said McDonough. The new Jinping detector, which will be buried under the slopes of the Himalayas, will be four times bigger than existing detectors. The underground JUNO detector near the coast of southern China will be 20 times bigger than existing detectors. "Knowing exactly how much radioactive power there is in the Earth will tell us about Earth's consumption rate in the past and its future fuel budget," said McDonough. "By showing how fast the planet has cooled down since its birth, we can estimate how long this fuel will last."


News Article | September 12, 2016
Site: www.rdmag.com

Earth requires fuel to drive plate tectonics, volcanoes and its magnetic field. Like a hybrid car, Earth taps two sources of energy to run its engine: primordial energy from assembling the planet and nuclear energy from the heat produced during natural radioactive decay. Scientists have developed numerous models to predict how much fuel remains inside Earth to drive its engines -- and estimates vary widely -- but the true amount remains unknown. In a new paper, a team of geologists and neutrino physicists boldly claims it will be able to determine by 2025 how much nuclear fuel and radioactive power remain in the Earth's tank. The study, authored by scientists from the University of Maryland, Charles University in Prague and the Chinese Academy of Geological Sciences, was published on September 9, 2016, in the journal Nature Scientific Reports. "I am one of those scientists who has created a compositional model of the Earth and predicted the amount of fuel inside Earth today," said one of the study's authors William McDonough, a professor of geology at the University of Maryland. "We're in a field of guesses. At this point in my career, I don't care if I'm right or wrong, I just want to know the answer." To calculate the amount of fuel inside Earth by 2025, the researchers will rely on detecting some of the tiniest subatomic particles known to science -- geoneutrinos. These antineutrino particles are byproducts of nuclear reactions within stars (including our sun), supernovae, black holes and human-made nuclear reactors. They also result from radioactive decay processes deep within the Earth. Detecting antineutrinos requires a huge detector the size of a small office building, housed about a mile underground to shield it from cosmic rays that could yield false positive results. Inside the detector, scientists detect antineutrinos when they crash into a hydrogen atom. The collision produces two characteristic light flashes that unequivocally announce the event. The number of events scientists detect relates directly to the number of atoms of uranium and thorium inside the Earth. And the decay of these elements, along with potassium, fuels the vast majority of the heat in the Earth's interior. To date, detecting antineutrinos has been painfully slow, with scientists recording only about 16 events per year from the underground detectors KamLAND in Japan and Borexino in Italy. However, researchers predict that three new detectors expected to come online by 2022--the SNO+ detector in Canada and the Jinping and JUNO detectors in China--will add 520 more events per year to the data stream. "Once we collect three years of antineutrino data from all five detectors, we are confident that we will have developed an accurate fuel gauge for the Earth and be able to calculate the amount of remaining fuel inside Earth," said McDonough. The new Jinping detector, which will be buried under the slopes of the Himalayas, will be four times bigger than existing detectors. The underground JUNO detector near the coast of southern China will be 20 times bigger than existing detectors. "Knowing exactly how much radioactive power there is in the Earth will tell us about Earth's consumption rate in the past and its future fuel budget," said McDonough. "By showing how fast the planet has cooled down since its birth, we can estimate how long this fuel will last."


News Article | November 10, 2016
Site: www.eurekalert.org

A dinosaur fossil that almost went undiscovered is giving scientists valuable clues about a family of creatures that flourished just before the mass extinction. The bird-like species, found at a building site in southern China and nicknamed the 'Mud Dragon', was preserved almost intact, lying on its front with its wings and neck outstretched. Scientists speculate that the creature may have died in this pose after becoming mired in mud about 66-72 million years ago. Scientists have named the new species Tongtianlong limosus, meaning 'muddy dragon on the road to heaven'. The two-legged animal belongs to a family of feathered dinosaurs called oviraptorosaurs, characterised by having short, toothless heads and sharp beaks. Some, including the newly found species, had crests of bone on their heads that were probably used as display structures to attract mates and intimidate rivals, like modern-day cassowaries. Fossil discoveries in recent decades suggest that this group of flightless animals was experiencing a population boost, diversifying into new species, during the 15 million years before the dinosaurs went extinct. The group was probably one of the last groups of dinosaurs to diversify before the asteroid impact 66 million years ago, which killed off all of the non-bird dinosaurs. The skeleton was found during excavations using explosives at a school construction site near Ganzhou. The fossil remains remarkably well preserved and almost complete, despite some harm caused by a dynamite blast at the construction site. Researchers from the University of Edinburgh and China, who carried out the study, say the finding helps better understand how the last-surviving dinosaurs were flourishing before tragedy struck. The study, published in Scientific Reports, was carried out in collaboration with the Institute of Geology, Chinese Academy of Geological Sciences and the Dongyang Museum, China, and is the latest in a fruitful collaboration between Edinburgh and the Chinese Academy of Geological Sciences. It was supported by the National Natural Science Foundation of China, the Fundamental Research Funds for the Chinese Academy of Geological Sciences, the EU Erasmus Mundus Experts Sustain Program and a Marie Curie Career Integration Grant. Dr Steve Brusatte, of the University of Edinburgh's School of GeoSciences, said: "This new dinosaur is one of the most beautiful, but saddest, fossils I've ever seen. But we're lucky that the 'Mud Dragon' got stuck in the muck, because its skeleton is one of the best examples of a dinosaur that was flourishing during those final few million years before the asteroid came down and changed the world in an instant." Dr Junchang Lü, of the Institute of Geology, Chinese Academy of Geological Sciences, said: "The discovery of the new oviraptorid dinosaur further indicates that the Ganzhou area of Southern China is a most productive locality of oviraptorid dinosaurs and has a huge diversity of oviraptorosaurs from the late Cretaceous. It will provide important information on the study of evolution, distribution and behaviour of oviraptorid dinosaurs."


News Article | November 10, 2016
Site: www.sciencedaily.com

A dinosaur fossil that almost went undiscovered is giving scientists valuable clues about a family of creatures that flourished just before the mass extinction. The bird-like species, found at a building site in southern China and nicknamed the 'Mud Dragon', was preserved almost intact, lying on its front with its wings and neck outstretched. Scientists speculate that the creature may have died in this pose after becoming mired in mud about 66-72 million years ago. Scientists have named the new species Tongtianlong limosus, meaning 'muddy dragon on the road to heaven'. The two-legged animal belongs to a family of feathered dinosaurs called oviraptorosaurs, characterised by having short, toothless heads and sharp beaks. Some, including the newly found species, had crests of bone on their heads that were probably used as display structures to attract mates and intimidate rivals, like modern-day cassowaries. Fossil discoveries in recent decades suggest that this group of flightless animals was experiencing a population boost, diversifying into new species, during the 15 million years before the dinosaurs went extinct. The group was probably one of the last groups of dinosaurs to diversify before the asteroid impact 66 million years ago, which killed off all of the non-bird dinosaurs. The skeleton was found during excavations using explosives at a school construction site near Ganzhou. The fossil remains remarkably well preserved and almost complete, despite some harm caused by a dynamite blast at the construction site. Researchers from the University of Edinburgh and China, who carried out the study, say the finding helps better understand how the last-surviving dinosaurs were flourishing before tragedy struck. The study, published in Scientific Reports, was carried out in collaboration with the Institute of Geology, Chinese Academy of Geological Sciences and the Dongyang Museum, China, and is the latest in a fruitful collaboration between Edinburgh and the Chinese Academy of Geological Sciences. It was supported by the National Natural Science Foundation of China, the Fundamental Research Funds for the Chinese Academy of Geological Sciences, the EU Erasmus Mundus Experts Sustain Program and a Marie Curie Career Integration Grant. Dr Steve Brusatte, of the University of Edinburgh's School of GeoSciences, said: "This new dinosaur is one of the most beautiful, but saddest, fossils I've ever seen. But we're lucky that the 'Mud Dragon' got stuck in the muck, because its skeleton is one of the best examples of a dinosaur that was flourishing during those final few million years before the asteroid came down and changed the world in an instant." Dr Junchang Lü, of the Institute of Geology, Chinese Academy of Geological Sciences, said: "The discovery of the new oviraptorid dinosaur further indicates that the Ganzhou area of Southern China is a most productive locality of oviraptorid dinosaurs and has a huge diversity of oviraptorosaurs from the late Cretaceous. It will provide important information on the study of evolution, distribution and behaviour of oviraptorid dinosaurs."


Gao L.-E.,Chinese Academy of Geological Sciences | Zeng L.,Chinese Academy of Geological Sciences
Geochimica et Cosmochimica Acta | Year: 2014

Identifying the timing of formation and geochemical nature of the Cenozoic granites along the Himalayan orogen is essential to test or formulate models that link crustal anatexis with tectonic transition during the evolution of large-scale collisional orogenic belts. The Malashan gneiss dome, one of the prominent domes within the Tethyan Himalaya, experienced Barrovian-type metamorphism and partial melting of pelitic rocks at relatively deep levels during the collision between India and Eurasia. New LA-MC-ICP-MS zircon U-Pb analyses yielded that the Malashan two-mica granites formed at a time span of 17.6±0.1 to 16.9±0.1Ma. The Malashan two-mica granites are characterized by: (1) high SiO2 (>71.3wt.%), Al2O3 (>14.8wt.%), and relatively high CaO (>1.3wt.%); (2) relatively high Sr (>146ppm), but low Rb/Sr ratios (<1.3) which are nearly constant relative to large variations in Ba concentrations; (3) enrichment in LREE, depletion in HREE, and no or weak negative Eu anomalies (Eu/Eu*=0.7-0.9); (4) as compared to granites in the other Northern Himalayan Gneiss Domes and High Himalayan Belt, relatively lower initial 87Sr/86Sr ratios (0.7391-0.7484) and similar unradiogenic Nd isotope compositions (εNd(t)=-13.7 to -14.4). These characteristics imply that the two-mica granites were derived from fluid-fluxing melting of metapelite, possibly triggered by the E-W extension. Our new data in combination with literature data indicate that there are three types of granites with diverse geochemical characteristics and distinct formation mechanisms along the Himalayan orogen since the Cenozoic India-Eurasia continental collision. Conceivably, our new results will provide new insights on how the partial melting behavior of relatively deeper crustal rocks evolved as the tectonic evolution of large orogenic belts. © 2014.


Li Z.H.,Chinese Academy of Geological Sciences
Science China Earth Sciences | Year: 2014

Continental subduction and collision normally follows oceanic subduction, with the remarkable event of formation and exhumation of high-to ultra-high-pressure (HP-UHP) metamorphic rocks. Based on the summary of numerical geodynamic models, six modes of continental convergence have been identified: pure shear thickening, folding and buckling, one-sided steep subduction, flat subduction, two-sided subduction, and subducting slab break-off. In addition, the exhumation of HP-UHP rocks can be formulated into eight modes: thrust fault exhumation, buckling exhumation, material circulation, overpressure model, exhumation of a coherent crustal slice, episodic ductile extrusion, slab break-off induced eduction, and exhumation through fractured overriding lithosphere. During the transition from subduction to exhumation, the weakening and detachment of subducted continental crust are prerequisites. However, the dominant weakening mechanisms and their roles in the subduction channel are poorly constrained. To a first degree approximation, the mechanism of continental subduction and exhumation can be treated as a subduction channel flow model, which incorporates the competing effects of downward Couette (subduction) flow and upward Poiseuille (exhumation) flow in the subduction channel. However, the (de-)hydration effect plays significant roles in the deformation of subduction channel and overriding lithosphere, which thereby result in very different modes from the simple subduction channel flow. Three-dimensionality is another important issue with highlighting the along-strike differential modes of continental subduction, collision and exhumation in the same continental convergence belt. © 2013, Science China Press and Springer-Verlag Berlin Heidelberg.


Geng Y.,Chinese Academy of Geological Sciences | Du L.,Chinese Academy of Geological Sciences | Ren L.,Chinese Academy of Geological Sciences
Gondwana Research | Year: 2012

We synthesize more than 2600 Hf isotope data on the Archean-Paleoproterozoic zircons from the North China Craton (NCC). Recalculation of the data based on single stage and two-stage Hf model ages of the Eastern Block of the NCC shows peak ages of 3902±13Ma and 3978±18Ma, respectively, and also small peaks at 3.5-4.0Ga. The majority of zircon ε Hf(t) values are positive, suggesting the possibility of the crust and the mantle differentiation at ca. 3.9-4.0Ga in the Eastern Block of the NCC. Most magmatic zircons from the whole of NCC have their Hf model age range of 2.4-2.9Ga, and the single stage model ages is cluster at 2698±4Ma, whereas the two-stage model ages concentrate at 2714±5Ma, implying that the protoliths were juvenile crustal rocks. The most prominent peak at 2.7Ga indicates that this period marks the most important stage of the crust-mantle differentiation and crust formation of the NCC. The widespread 2.5Ga rocks in the NCC and the absence of the 2.5Ga peaks in Hf model ages are consistent with the partial melting and reworking of the juvenile rocks at 2.5Ga. Furthermore, the 2.5-1.7Ga zircon Hf isotope features are also related to the reworking of the crustal rocks. Our results from the integration of a large database suggest that the Eastern Block and the Trans-North China Orogen have undergone similar crust-mantle differentiation and magmatism, leading to the conclusion that the essential cratonization of the North China took place at the end of Neoarchean. © 2011.


An M.,Chinese Academy of Geological Sciences
Geophysical Journal International | Year: 2012

The resolution matrix of an inverse problem defines a linear relationship in which each solution parameter is derived from the weighted averages of nearby true-model parameters, and the resolution matrix elements are the weights. Resolution matrices are not only widely used to measure the solution obtainability or the inversion perfectness from the data based on the degree to which the matrix approximates the identity matrix, but also to extract spatial-resolution or resolution-length information. Resolution matrices presented in previous spatial-resolution analysis studies can be divided into three classes: direct resolution matrix, regularized/stabilized resolution matrix and hybrid resolution matrix. The direct resolution matrix can yield resolution-length information only for ill-posed inverse problems. The regularized resolution matrix cannot give any spatial-resolution information. The hybrid resolution matrix can provide resolution-length information; however, this depends on the regularization contribution to the inversion. The computation of the matrices needs matrix operation, however, this is often a difficult problem for very large inverse problems. Here, a new class of resolution matrices, generated using a Gaussian approximation (called the statistical resolution matrices), is proposed whereby the direct determination of the matrix is accomplished via a simple one-parameter non-linear inversion performed based on limited pairs of random synthetic models and their inverse solutions. Tests showed that a statistical resolution matrix could not only measure the resolution obtainable from the data, but also provided reasonable spatial/temporal resolution or resolution-length information. The estimates were restricted to forward/inversion processes and were independent of the degree of inverse skill used in the solution inversion; therefore, the original inversion codes did not need to be modified. The absence of a requirement for matrix operations during the estimation process indicated that this approach is particularly suitable for very large linear/linearized inverse problems. The estimation of statistical resolution matrices is useful for both direction-dependent and direction-independent resolution estimations. Interestingly, even a random synthetic input model without specific checkers provided an inverse output solution that yielded a checkerboard pattern that gave not only indicative resolution-length information but also information on the direction dependence of the resolution. © 2012 The Author Geophysical Journal International © 2012 RAS.

Loading Chinese Academy of Geological Sciences collaborators
Loading Chinese Academy of Geological Sciences collaborators