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Reconstructing forest and grassland cover changes in China over the past millennium

Science China earth Sciences 2025年第1期68卷 94-110页

作者： Fanneng HE Fan YANG Yafei WANG key laboratory of land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences key Research Institute of Yellow River Civilization and Sustainable Development Henan University University of Chinese Academy of Sciences

Historical forest and grassland cover changes not only are critical indicators for quantifying ecological and environmental change processes but also serve as fundamental data for long-term climate change simulations and terrestrial ecosystem carbon emission assessments. However, because of limitations in historical data, quantitative estimations and spatially gridded reconstructions of these changes remain challenging, necessitating further methodological exploration. This study focused on China's present-day land area over the past millennium, objectively capturing the characteristics and drivers of forest and grassland cover changes. On this basis, using the forest transition theory and the space-for-time substitution method, we depicted the historical deforestation process as an inverted “S” curve and developed a model to reconstruct historical forest area changes based on the functional relationship between the forest area and population size dynamics. Subsequently, a gridded forest allocation model was established on the basis of deforestation tendencies. For the grassland cover, we implemented regionspecific methods, such as the cropland area deduction method and the habitat constraint method, to quantitatively reconstruct historical changes. Consequently, we obtained provincial forest and grassland area changes over the past millennium and mapped 10-km-resolution gridded data of forest and grassland cover. The results indicated the following.(1) The methods developed using population data as a proxy objectively reproduced the spatiotemporal evolution of forest and grassland cover in China over the past millennium. These feasible methods offer a novel pathway for the quantitative reconstruction of historical forest and grassland cover changes.(2) The data indicated that China's forest area generally decreased over the past millennium, characterized by a “decrease-then-increase” pattern. The forest area experienced three distinct phases: a slow decline(AD 1000

关键词： land use and land cover change Forest Grassland Quantitative reconstruction Gridded reconstruction China historical period

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The study of subduction channels:Progress,controversies,and challenges

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Science China earth Sciences 2020年第12期63卷 1831-1851页

作者： Jianxin Zhang key laboratory of deep-earth dynamics of the ministry of land and resources Institute of GeologyChinese Academy of Geological SciencesBeijing100037China

The subduction channel is defined as a relatively thin and weak zone with coherent kinematics between the descending and overriding plates during *** materials in the channel,showing the characteristics of mélange,consist of low-density,low-viscosity,highly sheared metasediments and/or serpentinite-rich matrix with relatively rigid *** channel materials flow downwards and upwards,forming a kind of channel *** on geophysical and geological observations on active oceanic subduction zones,combined with numerical simulations,the subduction channel model was initially set to shallow depthsdeeper geodynamic environments of oceanic subduction zones and explore the exhumation of high to ultrahigh pressure metamorphic *** is also extended to continental subduction zones in order to explain the exhumation of metamorphic rocks in different grades as well as fluid activity and crust-mantle interaction during continental *** there are a series of differences in material composition and slab/mantle interface property between the upper and lower plates,continental subduction channels exhibit many similarities in structure and dynamics to oceanic subduction *** studies have provided a fundamental understanding of the structural and dynamic characteristics of subduction channels,but many problems still need to be solved and *** particular,the fundamental characteristics of subduction channels obtained by numerical simulation need to be confirmed and modified through geological investigations of fossil subduction channels.

关键词： Plate interface Subduction channel Mélange Numerical modeling High-ultrahigh pressure metamorphism Exhumation mechanism

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Metallogenesis within continental collision zones: Comparisons of modern collisional orogens

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Science China earth Sciences 2018年第12期61卷 1737-1760页

作者： Hongrui ZHANG Zengqian HOU key laboratory of deep-earth dynamics of ministry of Natural resources Institute of Geology Chinese Academy of Geological Sciences

Modern collisional orogens represent the natural laboratory for the study of metallogeny in continental collision zones. The Pyrenees, Alps, Zagros and Himalaya are all associated with Neo-Tethyan subduction and represent the youngest collisional orogens on earth. Here, we compare these four orogens in terms of their composition, architecture, tectonic evolution,and metallogenic systems. The four orogens can be divided into simple and composite types. Simple orogens are represented by the Pyrenees and the Alps, and are characterized by narrow linear shapes in plain view and symmetric structures in cross-section,are free of arc magmatism, and are associated with the Mississippi Valley Valley-type Pb-Zn and orogenic gold deposits. The mineral deposits that form in these simple collisional orogens are generally related to processes that occur in the middle and upper crust. In contrast, composite orogens, as exemplified by the Zagros-Iranian and Himalayan-Tibetan Plateaus, are associated with broad orogenic plateaus in plain view and asymmetrical structures in cross-section, record extensive arc magmatism in continental margins, and are associated with a variety of deposit types including carbonatite-related rare earth element(REE),porphyry Cu-Mo, orogenic Au, Mississippi Valley type Pb-Zn, and detachment-fault-related polymetallic deposits. Although the subduction of Neo-Tethys oceanic crust occurred before the creation of simple collisional orogens in the Pyrenees and the Alps,these areas do not show the record of continental arc magmatism. In contrast, the composite collisional orogens are associated with the development of huge continental margin arcs prior to continental subduction, and the subduction was followed by reactivation of the subduction-modified arc lithospheric material, generating the ore-forming systems in these regions.

关键词： Pyrenees Alps Zagros Himalaya Collisional orogeny Accretionary orogeny Collisional metallogenesis

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Helium Isotopic Composition of the Songduo Eclogites in the Lhasa Terrane,Tibet: Information from the deep Mantle

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Journal of earth Science 2019年第3期30卷 563-570页

作者： Zhaoli Li Jingsui Yang Tianfu Li Songyong Chen key laboratory of deep-earth dynamics of ministry of Natural resources Institute of GeologyChinese Academy of Geological Sciences

Helium isotopic compositions are considered to be ideal tracers to identify whether mantle materials have been added to crustal rocks or *** this paper,we present the helium isotopic compositions of the Songduo eclogites in the Lhasa terrane,*** found that garnet and omphacite in the eclogites have different helium retention *** 4He content of most omphacite grains are about 10–20 times of that of garnet,suggesting that omphacite has a higher ability to capture 4He than ***,there is about 10–20 times difference in 3He content between omphacite and garnet in the same eclogite *** 3He/4He ratios of garnet and omphacite in these rocks range from 0.27 to 0.60 Ra(relative to the modern air 3He/4He ratio,1.4×10^-6).These ratios are within the range of both mantle-and crust-derived helium,suggesting mixed *** Songduo eclogites have much higher3He/4He ratios than those observed in the Dabie eclogites of eastern *** high ratios are typically thought to be associated with deep mantle *** cautiously conclude that deep mantle materials might have been involved during the formation of the Songduo eclogites.

关键词： eclogite helium isotopic composition HP/UHP metamorphic belt Lhasa terrane Qinghai-Tibet Plateau

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Geochemistry and Geochronology of the Jinghong Ophiolites:Implications for the Tectonic Evolution of the Eastern Paleo-Tethys

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Acta Geologica Sinica(English Edition) 2021年第5期95卷 1509-1526页

作者： ZHU Jianjiang LIU Fulai WANG Fang XIE Shiwen CAI Jia JI Lei WANG Huining key laboratory of deep-earth dynamics of ministry of Natural resources Institute of GeologyChinese Academy of Geological ScienceBeijing 100037China

The Jinghong mafic-ultramafic complex,exposed in the eastern margin of the Lancangjiang tectonic belt,is related to the subduction of the Paleo-Tethys *** petrogenesis plays a key role in constraining the tectonic evolution of the eastern Paleo-Tethys Ocean in southwestern *** this study,we present petrological,geochemical and geochronological results of the Jinghong complex rocks,in order to decipher their origin and tectonic *** Jinghong mafic-ultramafic complex was composed of peridotite,gabbro,basalt and minor ***-rock geochemical data of the mafic rocks indicate that they have both MORB and IAB affinities and plot in the back-arc basin basalt(BABB)field in the FeO^(*)/MgO ***_(2) *** with their trace element characteristics,it can be concluded that the Jinghong mafic-ultramafic complex represents an ophiolite suite that was formed in a back-arc ocean *** LA-ICP-MS zircon U-Pb dating yielded weighted mean ^(206)Pb/^(238)U ages of 298.4±1.7 Ma,294.3±1.6 Ma,and 292.8±2.0 Ma for gabbroic rocks from this complex,which indicates that the Jinghong ophiolites were formed during the early Permian(298-293 Ma).We propose that during subduction of the main Paleo-Tethys Ocean,a back-arc ocean basin was formed at the east of the Lancangjiang tectonic belt.

关键词： ophiolite zircon U-Pb dating back-arc basin Lancangjiang belt Paleo-Tethys

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Preface: Introduction of IGCP 649 Project——Diamonds and Recycled Mantle

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Journal of earth Science 2019年第3期30卷 429-430页

作者： Jingsui Yang Tingting Shen Cong Zhang Tian Qiu key laboratory of deep-earth dynamics of ministry of Natural resources Institute of GeologyChinese Academy of Geological Sciences

This special issue is attributed to the IGCP-649 Project. The IGCP-649 Project “Diamonds and Recycled Mantle” is an International Geosciences Program sponsored by UNESCO (the United Nations Educational, Scientific and Cultural Organization) and IUGS (International Union of Geological Sciences), is a global research project, aimed to carry out extensive and systematic research on peridotites, chromitites and related ma-terials such as diamond, moissanite and other unusual minerals, from different ophiolites in global orogenic belts, in order to understand the formation and origin of deep-mantle minerals in oceanic lithosphere, the origin of carbon for the ophiolitehosted diamonds, the evolution of earth's mantle and the dy-namic process of ophiolite emplacement.

关键词： Recycled Project IGCP origin project UNESCO carbon IUGS

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Precambrian Tectonic Affinity of the Southern Langshan Area, Northeastern Margin of the Alxa Block: Evidence from Zircon U-Pb Dating and Lu-Hf Isotopes

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Acta Geologica Sinica(English Edition) 2022年第5期96卷 1516-1533页

作者： NIU Pengfei QU Junfeng ZHANG Jin ZHANG Beihang ZHAO Heng key laboratory of deep-earth dynamics Ministry of Natural Resources of GeologyInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China

The Alxa Block is the westernmost part of the North China Craton(NCC), and is regarded as one of the basement components of the NCC. Its geological evolution is of great significance for the understanding of the ***, the Precambrian basement of the Alxa Block is still poorly studied. In this study, we present new in situ LA-ICPMS zircon U-Pb and Lu-Hf isotope data from the Diebusige Metamorphic Complex(DMC) which located in the eastern Alxa Block. Field and petrological studies show that the DMC consists mainly of metamorphic supracrustal rocks and minor metamorphic plutonic rocks and has experienced amphibolite-granulite facies metamorphism. Zircon U-Pb dating results suggested that the amphibolite sample yields a crystallization age of 2636 ± 14 Ma and metamorphic ages of 2517–2454 Ma and 1988–1952 Ma, proving the existence of exposed Archean rocks in the Langshan area and indicating that late Neoarchean to Paleoproterozoic metamorphic events existed in the Alxa Block. Two paragneiss samples show that the magmatic detrital zircons from the DMC yield 207Pb/206Pb ages ranging from 2.48 Ga to 2.10 Ga with two youngest peaks at 2.13 Ga and 2.16 Ga, respectively, and they were also overprinted by metamorphic events at 1.97–1.90 Ga and 1.89–1.79Ga. Compilation of U-Pb ages of magmatic detrital and metamorphic zircons suggested that the main part of the DMC may have been formed at 2.1–2.0 Ga. Zircon Lu-Hf isotope data show that the source materials of the main part of the DMC were originated from the reworking of ancient Archean crust(3.45–2.78 Ga). The Hf isotope characteristics and the tectonothermal event records exhibit different evolution history with the Khondalite Belt and the Yinshan Block and the other basements of the Alxa Block, indicating that the Langshan was likely an independent terrain before the middle Paleoproterozoic and was subjected to the middle to late Paleoproterozoic tectonothermal events with the Khondalite Belt as a whole.

关键词： zircon U-Pb dating Hf isotop Paleoproterozoic Neoarchean Diebusige Metamorphic Complex Alxa Block North China Craton

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Diffusion of helium in FCT zircon

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Science China earth Sciences 2019年第4期62卷 719-732页

作者： Shun YU Wen CHEN Jingbo SUN Ze SHEN laboratory of Isotope Thermochronology Institute of Geology Chinese Academy of Geological Sciences key laboratory of deep-earth dynamics of ministry of Natural resources Institute of GeologyChinese Academy of Geological Sciences

To gain a better quantitative understanding of zircon(U-Th)/He ages and evaluate the applicability of zircon(U-Th)/He dating, the diffusion characteristics, He diffusion kinetics, helium partial retention zone(HePRZ), closure temperature, and(U-Th)/He ages were investigated using high-precision laboratory step heating experiments based on the thermally activated diffusion process. The ln(D/a^2) in Fish Canyon Tuff(FCT) zircons determined from laboratory step heating experiments was negatively correlated with reciprocal temperature, as expected for thermally activated volume diffusion. The zircon activation energies ranged from 144 to 184 kJ mol^(-1) with a mean of 169±12 kJ mol^(-1). The closure temperatures ranged from 144 to 216°C(a cooling rate of 10°C Ma^(-1) and an effective grain radius of 38–60 μm) with an average of 176±18°C. The calculated closure temperature increased with increasing cooling rate, yielding an average zircon He closure temperature of ～136°C at a slow cooling rate of 0.1°C Ma^(-1), whereas the closure value was ～199°C at a cooling rate of 100°C Ma^(-1). The closure temperature increased with the equivalent spherical radius assuming a constant cooling rate. The He ages from FCT zircons were negligibly affected by grain size because of the rapid cooling. He preserved in the zircon was sensitive to temperature and holding time, and the temperature range for zircon HePRZ gradually decreased with increasing holding time. The(U-Th)/He ages from 26 FCT zircons yielded an algorithmic mean of 28.3±0.3 Ma(S.E.) and a geometric mean of 28.4±0.3 Ma(S.E.), consistent with the ages of 28.4±1.9 Ma reported by other laboratories. The FCT zircons were characterized by rapid cooling, young(U-Th)/He ages with good reproducibility, and low alpha doses. Weak correlations between the He ages and effective uranium(eU) concentrations from the FCT zircons indicated radiation damage did not significantly affect He diffusivity.

关键词： Zircon Helium diffusion (U-Th)/He Closure temperature Thermochronometry

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Late Mesozoic Tectono-Thermal History in the South Margin of Great Xing’an Range,NE China:Insights from Zircon and Apatite(U-Th)/He Ages

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Journal of earth Science 2022年第1期33卷 36-44页

作者： Wen Zhang Shuangfeng Zhao Jingbo Sun Ze Shen Wen Chen laboratory of Isotope Thermochronology Key Laboratory of Deep-Earth Dynamics of Ministry of Natural ResourcesInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China

The Late Mesozoic tectono-thermal evolution and geodynamic setting of the Great Xing’an Range(GXR),particularly in the south margin,are still *** this study,we present original low-temperature thermochronological data of six granitoid samples collected from Maanzi pluton in the south margin of the *** apatite and zircon(U-Th)/He ages vary of 70.8 ± 4.3-119.0 ±7.0 Ma and 120.0 ± 7.1-146.7 ± 8.7 Ma,*** numerical inverse modeling results reveal that the granitoid plutons experienced a rapid cooling and exhumation stage during Early Cretaceous with a rate of ~5.0-6.0 ℃/Ma and ~0.14-0.17 mm/yr,respectively,including the western minor pluton emplaced during Early Permian and the major pluton crystallized in latest Jurassic,corresponding to the extensional tectonics in NE *** rapid exhumation processes in the south margin of the GXR during the Early Cretaceous could be related to both the rollback of Paleo-Pacific oceanic plate and the collapse of thickened crust in the Mongol-Okhotsk Orogen.

关键词： Great Xing’an Range tectono-thermal history (U-Th)/He dating extensional tectonics Mongol-Okhotsk collapse Paleo-Pacific subduction geochemistry

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Dur’ngoi Ophiolite in East Kunlun, Northeast Tibetan Plateau: Evidence for Paleo-Tethyan Suture in Northwest China

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Journal of China University of Geosciences 2009年第2期20卷 303-331页

作者：杨经绥史仁灯吴才来王希斌 Paul T Robinson key laboratory for Continental dynamics of the ministry of land and resources Institute of GeologyChinese Academy of Geological Sciences Department of earth Sciences Dalhousie University

The A＇nyemaqen （阿尼玛卿） ophiolite belt along the southern margin of the East Kunlun （昆仑） Mountains marks the suture formed by the closure of paleo-Tethys. The Dur＇ngoi ophiolite in the eastern part of this belt consists of meta-peridotite, mafic-ultramafic cumulates, sheeted dikes and basaltic lavas. The meta-peridotites consist of dunite, harzburgite, lherzolite, feldspar-bearing lherzolite and garnet-bearing lherzolite and contain residual spinel with Cr# [100×Cr/（Cr＋Al）] ranging from 30 to 57 and Mg# [100×Mg/（Mg＋Fe2＋）] ranging from 50 to 75, indicating an Al- and Mg-rich series. The meta-peridotites have a relatively narrow range of composition with Mg# of 89.2-92.6, Al2O3 contents of （1-4） wt.% and slightly depleted chondrite normalized REE patterns, indicating that they represent relict mantle material that has undergone intermediate to low degrees of partial melting. Garnets in the lherzolite are andradite, enriched in Ca and Fe and depleted in Mg and AI （And=95-97, Pyr=0.3-5, Gro=0-3）, indicating a metamorphic origin. The cumulate rocks mainly consist of dunite, wehrlite, pyroxenite and gabbro. A well-layered gabbro-pyroxenite complex is defined by modal variations in plagioclase and pyroxene. Blocks of garnet-pyroxenite or rodingite are locally present in the meta-peridotites. Garnets in the cumulate rocks are grossular （Gro=69-90, And=9-19, Br=l-12）, also metamorphic origin. The diabase dikes are moderately depleted in LREE [（La/Sm）N=0.5-0.8] and HREE resulting in slightly convex chondrite-normalized patterns with slightly positive Eu anomalies （δEu=1.1-1.3）. The basaltic lavas have REE patterns similar to those of MORB with （La/Sm）N ratios of 0.5-1 and small negative Eu anomalies. They appear to have been derived from a depleted mantle source and to have undergone little or no differentiation during crystallization. SHRIMP U-Pb dating of zircons from the basalts yields 286pb/238U ages of 276-319 Ma （average 308.0±4.9 Ma）. The Dur＇ngoi ophiolite is interprete

关键词： ophiolite Dur'ngoi A'nyemaqen East Kunlun Tibet.

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