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Multiple thermal events recorded in the Acasta Gneiss Complex:Evidence from in-situ dating of zircon, titanite, and apatite

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Science China Earth Sciences 2024年第3期67卷 673-686页

作者： Qingfeng MEI Jinhui YANG Jinfeng SUN Qiuli LI Shitou WU Xiaoxiao LING Peng PENG Hao WANG State Key laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Key laboratory of computational geodynamics University of Chinese Academy of SciencesBeijing 100049China

In-situ dating of the zircons, titanites, and apatites in the rock fragments of approximately 1 cm2in size from the Acasta Gneiss Complex was performed using secondary ion mass spectrometry or laser ablation inductively coupled plasma mass spectrometry to provide constraints on the thermal history of the Acasta Gneiss Complex. The zircons in these rock fragments typically exhibit multiple age populations, reflecting the presence of inherited zircons or the post-crystallization process of zircon overgrowth. Combined with previous studies, our zircon dating results reveal multiple magmatic events that occurred in the Acasta Gneiss Complex, specifically at >3.96, ~3.72, and ~3.57 Ga, respectively. A titanite Pb-Pb isochron age of2911±22 Ma(95% confidence level, MSWD=1.5) for sample AY199 is identified, consistent with the timing of the latest Archean magmatism in the Acasta Gneiss Complex. The titanite U-Pb ages for samples AC478 and AY066 are 1932±270 Ma(95% confidence level, MSWD=2.3) and 1813±45 Ma(95% confidence level, MSWD=2.3), respectively. The apatites in sample P090803-C exhibit a Pb-Pb isochron age of 1833±26 Ma(95% confidence level, MSWD=1.4). The apatite U-Pb ages for samples AC478, AY199, and AY066 are 1850±20 Ma(95% confidence level, MSWD=1.3), 1827±100 Ma(95% confidence level, MSWD=6.3), and 1807±58 Ma(95% confidence level, MSWD=3.9), respectively. Titanites in samples AC478 and AY066, as well as the apatites in all four investigated samples, show a uniform age(Pb-Pb or U-Pb age) of ~1.9–1.8 Ga,indicating U-Pb system reset in these minerals due to the Wopmay orogeny and documenting that the peak temperature condition associated with the Wopmay orogeny exceeded the apatite U-Pb closure temperature and approached or exceeded that of titanite.

关键词： Zircon Titanite Apatite Acasta Gneiss Complex Wopmay Orogen

The role of sub-continental lithosphere mantle in deep F and Cl cycling: Insight from the Dabeigou basalts, North China Craton

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Science China Earth Sciences 2024年

作者： Yadong WU Jinhui YANG Jinfeng SUN Hao WANG Baoquan ZHOU State Key laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences Key laboratory of computational geodynamics University of Chinese Academy of Sciences

The sub-continental lithosphere mantle （SCLM） represents a mechanical barrier that separate the convecting mantle from the exosphere,and possesses the ability to sequester and release volatiles,making it an integral part in deep volatile *** we explore the SCLM in modulating F and Cl cycling through a case study from the Early Cretaceous Dabeigou basalts in the North China Craton （NCC）.These lavas are associated with decratonization of the NCC,a process involving significant removal and replacement of the ancient *** Dabeigou basalts,characterized by arc magma-like trace element signatures,evolved initial87Sr/86Sr （0.70574–0.70578）,εNd（t）(-11.2–-11.1),and εHf（t）(-13.7–-13.4) values,along with high Fe/Mn ratios,Ni contents,and δ18O values （5.8‰–6.8‰） of olivine phenocrysts,are compatible with their origination from a veined,pyroxene-rich source formed through the infiltration and interaction of hydrous silicate melts from the subducting Pacific slabs with ambient ***-hosted melt inclusions of the Dabeigou basalts have compositions similar to the whole rocks,indicating that they record pre-eruptive melt compositions forming the whole *** melt inclusions exhibit high F（1371–2316 ppm） and moderate Cl （688–900 ppm） contents,with high F/Cl ratios of 2.1±0.3 （1σ）.The F and Cl signatures of the Dabeigou basalts are different from those of typical arc magmas,which are commonly characterized by high Cl contents （median of～1200 ppm） and low F/Cl ratios （<1）.The observed differences can be attributed to chromatographic reaction that fractionates elements of different compatibility in the metasomatic agents,with amphibole as the main mineral phase for fractionating and preserving F and *** is,amphibole crystallization prefers to retain F rather than Cl,making the metasomes in vein enriched in F and exhibiting elevated F/Cl ratios compared to original metasomatic *** is further suggested that the scenario inferred from the Dabeigou basalts m

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Present-day Upper-crustal Strain Rate Field in Southeastern Tibet and its Geodynamic Implications:Constraints from GPS Measurements with ABIC Method

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Acta Geologica Sinica(English Edition) 2024年第1期98卷 265-275页

作者： YANG Shaohua PAN Jiawei LI Haibing SHI Yaolin Key laboratory of Continental Dynamics of Ministry of Natural Resources Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China Jiangsu Donghai Continental Deep Hole Crustal Activity National Observation and Research Station DonghaiJiangsu 222300China Key laboratory of computational geodynamics College of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China

The Earth’s surface kinematics and deformation are fundamental to understanding crustal *** effective research approach is to estimate regional motion field and deformation fields based on modern geodetic *** the discrete observed velocity field is obtained,the velocity related fields,such as dilatation rate and maximum shear strain rate,can be estimated by applying varied mathematical *** study applied Akaike's Bayesian Information Criterion(ABIC)method to calculate strain rate fields constrained by GPS observations in the southeast Tibetan *** with results derived from other three methods revealed that our ABIC-derived strain rate fields were more *** maximum shear strain rate highlighted the Xianshuihe–Xiaojiang fault system as the main boundary for the outward migration of material in southeastern Tibet,indicating rotation of eastern Tibet material around the eastern Himalaya rather than whole extrusion along a fixed ***,distinct dilatation rate patterns in the northeast and southwest regions of the fault system were *** northeast region,represented by the Longmenshan area,exhibited negative dilatational anomalies;while the southwest region,represented by the Jinsha River area north of 29°N,displayed positive dilatational *** indicates compression in the former and extension in the *** with deep geophysical observations,we believe that the upper and lower crusts of the Jinsha River area north of 29°N are in an entire expanding state,probably caused by the escape-drag effect of *** presence of a large,low-viscosity region south of 29°N may not enable the entire escape of the crust,but instead result in a differential escape of the lower crust faster than the upper crust.

关键词： strain rate differential escape ABIC GPS southeastern Tibet

Seismicity changes and numerical simulation of coseismic deformation following the 2022 M_(s)6.8 Luding earthquake in Sichuan,China

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Science China Earth Sciences 2024年第8期67卷 2507-2521页

作者： Qiu MENG Zitao WANG Huai ZHANG Key laboratory of computational geodynamics of Chinese Academy of Sciences College of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China Institute of Earthquake Forecasting China Earthquake AdministrationBeijing 100036China Southern Marine Science and Engineering Guangdong laboratory(Zhuhai) Zhuhai 519080China Beijing Yanshan Earth Critical Zone National Research Station Beijing 101408China

The Xianshuihe fault is a major tectonic boundary between the Sichuan-Yunnan rhombic and Bayanhar blocks in Southwest *** an average left-lateral strike-slip movement of 10–15 mm/yr,it is a fast-moving strike-slip continental *** September 5,2022,the Ms6.8 Luding earthquake occurred along the Moxi segment of the Xianshuihe fault,reaching a maximum intensity of IX and resulting in a significant number of casualties and severe property *** earthquake broke the long-standing seismic quiescence of the Xianshuihe fault,which lasted for more than 40 years,and was followed by a significant number of *** outstanding question is how the behavior of the Xianshuihe fault and major earthquakes changed following this *** this study,we examined the changes in regional seismicity following the Luding earthquake and identified the potential for future strong earthquakes along the Xianshuihe *** used a finite element numerical method to simulate the environment of the seismogenic fault and its adjacent *** addition,we used the coseismic slip model of the Luding earthquake with the split-node method to calculate how the stress and strain fields in the surrounding area were affected by the2022 *** stress changes were resolved in the main faults,and the seismicity of adjacent faults was analyzed in conjunction with the observed seismic *** results indicate that regional tectonic movement primarily occurred to the southeast along the Moxi *** stress field is approximately north-south in tension and east-west in *** in the stress field in the epicentral region of the Luding earthquake exceeded 1 *** maximum displacement of the coseismic deformation field was concentrated between Moxi town and Tuanjie village,and the Coulomb stress of the fault zone in this region experienced the largest ***,the b-value of the Gutenberg-Richter magnitude-frequency relationship at the epicenter a

关键词： Luding earthquake Seismicity Coulomb failure stress change Finite element numerical simulation

Seismic and geological evidence of hidden faults in the Yinpan Reservoir area based on a dense seismic array

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Science China Earth Sciences 2024年第7期67卷 2401-2407页

作者： Guangyao YIN Huai ZHANG Liwen GONG Q ipeng BAI Yicun GUO Bing ZHANG Yaolin SHI Key laboratoryof Earth System Numerical Modeling and Application(Chinese Academyof Sciences) College of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China Key laboratory of computational geodynamics Chinese Academy of SciencesBeijing 100049China Southern Marine Science and Engineering Guangdong laboratory(Zhuhai) Zhuhai 519080China Beijing Yanshan Critical Zone National Field Scientific Observation and Research Station Beijing 101408China Chongqing Earthquake Agency Chongqing 401147 China Institute of Earthquake Forecasting China Earthquake AdministrationBeijing 100036China Hangzhou Applied Acoustics Research Institute Hangzhou 311100China State Key laboratory of Geodesy and Earths Dynamics Innovation Academy for Precision Measurement Science and TechnologyCASWuhan 430077China

*** November 23,2017,an M_(S)5.0 earthquake occurred in Wulong,Chongqing,China,resulting in tens of casualties and considerable economic ***,the epicenter of this earthquake was located in the transition zone from the... 详细信息

关键词： earthquake southeast seismic

Three-dimensional numerical simulation of glacial trough forming process

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Science China Earth Sciences 2015年第9期58卷 1656-1668页

作者： YANG ShaoHua SHI YaoLin Key laboratory of computational geodynamics of Chinese Academy of Sciences University of Chinese Academy of Sciences

The glacial trough is a common glacier erosion landscape, which plays an important role in the study of glacier erosion processes. In a sharp contrast with the developing river, which is generally meandering, the developing glacial trough is usually wide and straight. Is the straightness of the glacial trough just the special phenomenon of some areas or a universal feature? What controls the straightness of the glacial trough? Until now, these issues have not been studied yet. In this paper, we conduct systematic numerical models of the glacier erosion and simulate the erosion evolution process of the glacial trough. Numerical simulations show that:(1) while the meandering glacier is eroding deeper to form the U-shaped cross section, the glacier is eroding laterally. The erosion rate of the ice-facing slope is bigger than that of the back-slope.(2) The smaller(bigger) the slope is, the smaller(bigger) the glacier erosion intensity is.(3) The smaller(bigger) the ice discharge is, the smaller(bigger) the glacier erosion intensity is. In the glacier erosion process, the erosion rate of the ice-facing slope is always greater than that of the back-slope. Therefore, the glacial trough always develops into more straight form. This paper comes to the conclusion that the shape evolution of the glacial trough is controlled mainly by the erosion mechanism of the glacier. Thereby, the glacial trough prefers straight geometry.

关键词： glacial trough erosion action numerical simulation finite element method

Finite element simulation of deformation and stress changes of Kalpin-Kemin fault system in the Southwest Tianshan Orogenic Belt

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Science China Earth Sciences 2022年第5期65卷 863-873页

作者： Zitao WANG Huai ZHANG Qiu MENG Yaolin SHI Key laboratory of computational geodynamics University of Chinese Academy of SciencesBeijing 100049China

Under the shadow of the far-field effect of the India-Eurasia collision,the Tianshan orogenic belt underwent tectonic re-activation in the Cenozoic,accompanied by strong tectonic deformation and frequent large *** by two rigid cratonic blocks located in its north and south,a series of marginal foreland fold-and-thrust belts are developed within the Tianshan orogenic belt and continue to develop to the bilateral pull-apart ***,the faults in the orogenic belt are *** deformation caused by thrust-related structure accounts for larger than 50%of the total convergence of the Tianshan Mountains,which results in the most active structure with large earthquakes in the Tianshan ***,it is of great significance to study the dynamic process of the newly generated and reactivated thrust-nappe structures in Tianshan orogen via numerical *** paper selects a classical cross-section profile in the western segment of the Southwest Tianshan Mountains,which contains the Kalpin-Maidan-Nalati-Kemin fault system from the south to the *** attempt to establish a two-dimensional plane strain,viscoelastic finite element model,by treating the regional faults as a whole fault system and considering the topography,fault geometry,and GPS *** displacement and stress fields of the model are retrieved,the short-term cumulative deformation field of the overall fault system is analyzed,and the rate of Coulomb failure stress change of each fault is also *** results show that the deformation is concentrated in the middle and southern parts of the Southwest Tianshan *** contrast,the deformation of the Kemin fault in the north is relatively *** to the Coulomb failure stress changes of these four faults and the historical earthquake catalog,the potential seismicity of each fault is qualitatively *** preliminary results suggest that the possibility of large earthquake occurrence is higher in the

关键词： Tianshan orogenic belt Viscoelastic finite element Coulomb failure stress change Seismicity

Lithospheric Thermal Isostasy of North Continental Margin of the South China Sea

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Journal of China University of Geosciences 2009年第1期20卷 95-106页

作者：陈石张健孙玉军石耀霖 laboratory of computational geodynamics Graduate University of Chinese Academy of SciencesBeijing 100049 China

Accompanied with rifting and detaching of the north continental margin of the South China Sea, the crust and the lithosphere become thinner away from the continental margin resulting from the tectonic activities, such as tensile deformation, thermal uplift, and cooling subsidence, etc.. Integrated with thermal, gravimetric, and isostatic analysis techniques, based on the seismic interpretation of the deep penetration seismic soundings across the northern margin of the South China Sea, we reconstructed the lithospheric thermal structure and derived the variation of the crust boundary in the east and west parts of the seismic profile by using gravity anomaly data. We mainly studied the thermal isostasy problems using the bathymetry of the profiles and calculated the crust thinning effect due to the thermal variety in the rifting process. The results indicate that the thermal isostasy may reach 2.5 km, and the compositional variations in the lithospheric density and thickness may produce a variation of 4.0 km. Therefore, the compositional isostatic correction is very important to recover the relationship between surface heat flow and topography. Moreover, because of the high heat flow characteristic of the continental margin, building the model of lithospheric geotherm in this region is of great importan for studying the Cenozoic tectonic thermal evolution of the north passive continental margin of the South China Sea.

关键词： north continental margin of the South China Sea lithosphere geothermal thermal isostasy.

Advances, Problems and Prospects of Modern Geodesy Applied in Tibetan Geodynamic Changes

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Acta Geologica Sinica(English Edition) 2013年第2期87卷 318-332页

作者： SUN Wenke ZHOU Xin Key laboratory of computational geodynamics of Chinese Academy of Sciences University of Chinese Academy of Sciences

Modern geodetic techniques have developed rapidly in recent years, providing reliable observation data and new effective approaches, and greatly enhancing studies of the Tibetan geodynamics. For instance, the well-known GPS technique has been employed to measure seismic slips for many faults in the Tibetan Plateau. GPS data agree well with the hypothesis of a thickening crust and eastward mass flow. Moreover, absolute gravimetric data have been applied to interpret geophysical phenomena such as crust movement, co-seismic gravity change, GIA, and ground water change. The satellite gravity mission GRACE launched in 2002 provided global gravity models with unprecedentedly high precision and high spatial resolution. It has been used in implementing temporal gravity changes and improving our knowledge of the Earth＇s interior, including lithosphere dynamics, mantle viscosity and rheology, plateau uplift, and subduction processing. It is noteworthy that gravity presents unique advantages for the study of Tibetan geodynamics because of its sensitivity to mass migration and dynamic redistribution. To date, great advances have been made in applying modern geodetic data in studying dynamic changes of Tibetan plateau. For instance, the horizontal displacement field from GPS data revealed dynamical characteristics of the present-day Tibetan plateau. The combination of gravity anomalies and topographic data describe the tectonic characteristics of Tibetan plateau. The combination of gravity data and GPS data show present properties of the Tibetan plateau such as crust thickening, Moho＇s subsidence, and plateau uplift. GRACE data were used to estimate the distribution of ice/snow melting. These results demonstrate that mere application of integrated geodetic data as well as geophysical methods and numerical simulations can enhance our knowledge of Tibetan plateau dynamics. It must be pointed out that GRACE data include various geophysical signals such as crust vertical movement, d

关键词： modern geodesy gravity GPS gravity satellite geodynamics Tibetan plateau