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Identification of carbonates with high positive carbon isotope excursion from the Liaohe Group in the northeastern North China Craton and implications for the Lomagundi-Jatuli Event 华北克拉通东北部辽河组高正碳同位素偏移碳酸盐岩的鉴定及其对洛马贡迪-贾图里事件的影响
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-30 DOI: 10.1007/s11430-023-1318-3
Hongyu Wang, Shuanhong Zhang, Sen Wang, Linghao Kong, Yue Zhao, Qiqi Zhang, Sen Gao, Guohui Hu

The Great Oxidation Event (GOE) during the early Paleoproterozoic represents the first significant buildup in Earth’s atmospheric oxygen and resulted in a series of significant changes in the Earth’s surface environment. Among them is the 2.22 (or 2.33)–2.06 Ga Lomagundi-Jatuli Event (LJE), which is globally, the largest magnitude and longest duration, marine carbonate positive carbon isotope excursion (δ13CV-PDB>10‰) known. This event has attracted the attention of scholars all over the world. However, except for a high positive carbon isotope excursion (δ13CV-PDB>10‰) recently identified from marine carbonate rocks within the Daposhan Formation in the lower Fanhe Group (or the Sanchazi Group) in the Longgang Block in the northeast North China Craton (NCC), Paleoproterozoic carbonates in the NCC are characterized by a low-amplitude positive carbon isotope excursion (δ13CV-PDB<5‰). This feature is significantly different from the high positive carbon isotope excursion characteristics of carbonates deposited during the LJE period in other cratons. To determine whether there are large-scale and reliable sedimentary records of the LJE in the NCC and the reasons for the low positive δ13C excursion of the Paleoproterozoic carbonates obtained by the previous studies, we conducted field investigations, carbon-oxygen isotopes, and whole-rock major and trace element geochemical analyses of Liaohe Group carbonate rocks from the Anshan area in the northwestern margin of the Jiao-Liao-Ji Belt in the northeast NCC. Our results show that the Gaojiayu Formation of the Liaohe Group in the Anshan area has high positive δ13CV-PDB values from 8.6‰ to 12.4‰ and δ18OV-SMOW values of 17.9‰–27.4‰ (δ18OV-PDB values ranging from −12.6‰ to −3.4‰). This provides solid evidence for the preservation of reliable sedimentary records of the LJE in the northeastern NCC. Deposition of the high positive δ13C excursion (>10‰) of marine carbonate rocks occurred at about 2.15 Ga. Lithological comparisons of different sections and whole-rock geochemical results show that the high positive δ13C excursion is mainly controlled by the stratigraphic interval and depositional ages; the changes of sedimentary facies and diagenesis have no significant effects on reducing of the δ13C values. The intrusion of mafic sills into carbonates has resulted in synchronous decrease of C–O isotopes near the contact zones, but the decreasing amplitude of δ13C is less than 3‰. Therefore, our study firstly identified marine carbonates with high positive δ13C excursion (>10‰) from the Gaojiayu Formation, which provides robust evidence for global correlation of the LJE, which has implications for its genesis and gl

古近纪早期的大氧化事件(GOE)代表了地球大气中氧气的首次显著积累,并导致了地球表面环境的一系列重大变化。其中,2.22(或 2.33)-2.06 Ga 洛马昆迪-贾图利事件(LJE)是全球已知的规模最大、持续时间最长的海洋碳酸盐正碳同位素偏移(δ13CV-PDB>10‰)。这一事件引起了全世界学者的关注。然而,除了最近在华北克拉通(NCC)东北龙岗区块下樊河组(或三岔子组)大坡山地层内的海相碳酸盐岩中发现了高幅正碳同位素偏移(δ13CV-PDB>10‰)外,华北克拉通古生代碳酸盐岩的特征是低幅正碳同位素偏移(δ13CV-PDB<5‰)。这一特征与其他陨石坑在LJE时期沉积的碳酸盐的高正碳同位素偏移特征明显不同。为确定北中国大陆是否存在大规模可靠的LJE沉积记录,以及前人研究获得的古近系碳酸盐岩低正δ13C偏移的原因,我们对北中国大陆东北部胶辽冀带西北缘鞍山地区的辽河组碳酸盐岩进行了野外调查、碳氧同位素和全岩主、微量元素地球化学分析。结果表明,鞍山地区辽河组高家峪地层的δ13CV-PDB值为8.6‰-12.4‰,δ18OV-SMOW值为17.9‰-27.4‰(δ18OV-PDB值为-12.6‰--3.4‰)。这为在北交界地区东北部保存可靠的 LJE 沉积记录提供了确凿的证据。海洋碳酸盐岩的δ13C高正向偏移(>10‰)大约发生在2.15 Ga。不同剖面的岩性对比和全岩地球化学结果表明,δ13C的高正向偏移主要受地层间隔和沉积年龄的控制,沉积面和成岩作用的变化对δ13C值的降低无明显影响。岩浆岩侵入碳酸盐岩导致接触带附近 C-O 同位素同步下降,但 δ13C 下降幅度小于 3‰。因此,我们的研究首次从高家峪地层中发现了δ13C高正向偏移(>10‰)的海相碳酸盐岩,为LJE的全球相关性提供了有力的证据,这对LJE的成因及其全球意义具有重要意义。此外,由于LJE的全球近同步性,LJE时期沉积的碳酸盐岩的碳氧同位素化学地层学与地质年代学数据相结合,可为南昌地区古近系沉积演替的地层划分与关联提供新的约束。
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引用次数: 0
Progress of vegetation modelling and future research prospects 植被建模的进展和未来研究前景
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-25 DOI: 10.1007/s11430-023-1367-1
Siqi Li, Xu Zhang, Zhengyao Lu, Jian Ni, Jianhua Lu

Terrestrial vegetation is a crucial component of the Earth system, and its changes not only represent one of the most distinct aspects of climate change but also exert significant feedback within the climate system by exchanging energy, moisture, and carbon dioxide. To quantitatively and mechanistically study climate-vegetation feedback, numerical vegetation models have been developed on the theory of ecophysiological constraints on plant functional types. The models eventually can simulate vegetation distribution and succession across different spatial and temporal scales, and associated terrestrial carbon cycle processes by categorizing vegetation into biomes according different plant functional types and their associated environmental factors. Here we review the developing history of vegetation models and provide recent advances and future directions. Before 21st century, static vegetation models, as developed statistical models, can only simulate equilibrated characteristics of vegetation distribution. In last several decades, Dynamic Global Vegetation Models (DGVMs) have been developed to simulate instantaneous responses of vegetation to climate change and associated dynamics, and can be coupled with Earth system models to investigate interactions among atmosphere, ocean, and land. DGVMs are also widely applied to investigate the dynamics accounting for changes in the geographic distribution patterns of land surface vegetation at different spatial and temporal scales and to assess the impacts of terrestrial carbon and water fluxes and land use changes. We suggest that future vegetation modeling could integrate with machine learning, and explore vegetation transient response and feedback as well as impacts of process hierarchies and human activities on climate and ecosystem.

陆地植被是地球系统的重要组成部分,它的变化不仅是气候变化最明显的方面之一,而且还通过能量、水分和二氧化碳的交换在气候系统中产生重要的反馈作用。为了对气候-植被反馈进行定量和机理研究,人们根据植物功能类型的生态生理学制约理论建立了植被数值模型。这些模型根据不同的植物功能类型及其相关的环境因子将植被划分为不同的生物群落,最终可以模拟不同时空尺度的植被分布和演替,以及相关的陆地碳循环过程。在此,我们回顾了植被模型的发展历史,并介绍了最新进展和未来方向。21 世纪以前,静态植被模型作为发达的统计模型,只能模拟植被分布的均衡特征。近几十年来,动态全球植被模型(DGVMs)得到了发展,可模拟植被对气候变化的瞬时响应及相关动态,并可与地球系统模型相结合,研究大气、海洋和陆地之间的相互作用。DGVMs 还被广泛应用于研究不同时空尺度上陆地表层植被地理分布模式变化的动力学,以及评估陆地碳通量和水通量以及土地利用变化的影响。我们建议,未来的植被建模可与机器学习相结合,探索植被的瞬态响应和反馈,以及过程层次和人类活动对气候和生态系统的影响。
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引用次数: 0
Stable hydrogen isoscape in precipitation generated using data fusion for East China 利用数据融合生成的华东地区降水中稳定氢等值线图
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-25 DOI: 10.1007/s11430-023-1377-0
Jiacheng Chen, Jie Chen, Xunchang John Zhang, Peiyi Peng

The stable hydrogen isotope in precipitation is an effective environmental tracer for climatic and hydrologic studies. However, accurate and high-precision precipitation hydrogen isoscapes are currently unavailable in China. In this study, a data fusion method based on Convolutional Neural Networks (CNN) is used to fuse the hydrogen isotopic composition (δ2Hp) of observations and isotope-equipped general circulation model (iGCM) simulations. A precipitation hydrogen isoscape with a temporal resolution of monthly and a spatial resolution of 50–60 km is established for East China for the 1969–2017 period. Prior to building the isoscape, the performance of three data fusion methods (DFMs) and two bias correction methods (BCMs) is compared. The results indicate that the CNN fusion method performs the best with a correlation coefficient larger than 0.90 and root mean square error smaller than 10.5‰when using observation as a benchmark. The fusion methods based on back propagation and long short-term memory neural network perform similarly, while slightly outperforming the bias correction methods. Thus, the CNN method is used to generate the hydrogen isoscape, and the temporal and spatial distribution characteristics of the hydrogen isotope in precipitation are analyzed based on this dataset. The generated isoscape shows similar spatial and temporal distribution characteristics to observations. In general, the distribution pattern of δ2Hp is consistent with the temperature effect in northern China, and consistent with the precipitation amount effect in southern China. The trend of the δ2Hp time series is consistent with that of observed precipitation and temperature. Overall, the generated isoscape effectively reproduces the observations, and has the characteristics of time continuity and relative spatial regularity, which can provide valuable data support for tracking atmospheric and hydrological processes.

降水中的稳定氢同位素是气候和水文研究的有效环境示踪剂。然而,中国目前还没有精确的高精度降水氢同位素图。本研究采用基于卷积神经网络(CNN)的数据融合方法,将观测数据和配备同位素的大气环流模式(iGCM)模拟数据的氢同位素组成(δ2Hp)进行融合。建立了华东地区1969-2017年降水氢等值线图,时间分辨率为月,空间分辨率为50-60千米。在建立等值线之前,比较了三种数据融合方法(DFM)和两种偏差校正方法(BCM)的性能。结果表明,以观测值为基准,CNN融合方法的相关系数大于0.90,均方根误差小于10.5‰,表现最佳。基于反向传播和长短期记忆神经网络的融合方法表现类似,但略微优于纠偏方法。因此,利用 CNN 方法生成了氢等值线图,并基于该数据集分析了降水中氢同位素的时空分布特征。生成的等值线图显示出与观测数据相似的时空分布特征。总体而言,δ2Hp 的分布模式与华北地区的温度效应一致,与华南地区的降水量效应一致。δ2Hp时间序列的变化趋势与观测到的降水和气温变化趋势一致。总之,生成的等值线图有效地再现了观测资料,具有时间连续性和空间相对规则性的特点,可为跟踪大气和水文过程提供宝贵的数据支持。
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引用次数: 0
The δ15N values of foxtail millet (Setaria italica) and common millet (Panicum miliaceum) are reliable indicators of manuring practices 狐尾黍(Setaria italica)和粢饭黍(Panicum miliaceum)的δ15N 值是肥料使用方法的可靠指标
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-23 DOI: 10.1007/s11430-023-1376-y
Jishuai Yang, Xiaoyan Yang, Ting You, Fahu Chen

Millet agriculture, which originated in northern China, alongside rice agriculture, have nurtured the Chinese civilization. Prehistoric manuring practices likely promoted and maintained sustainable millet agricultural production in the loess area of northern China. However, ongoing controversy exists regarding the indicators of prehistoric manuring intensity of foxtail millet (Setaria italica) and common millet (Panicum miliaceum). Here, we present the results of pot and field fertilization experiments on two millet types. Our findings suggest that manuring can significantly increase the δ15N values of foxtail millet, and its δ15N values increase with increasing manuring levels. The δ15N values of foxtail millet leaves are systematically greater than those of grains by approximately 1.6‰. Manuring could have a long-term residual impact on increasing the δ15N values of soil and millet crops. Combined with previous crop fertilization experiment results, we propose that the impact of manuring on the δ15N values of non-nitrogen-fixing crops is roughly consistent. The δ15N value and amount of manure are key factors determining the extent of change in plant δ15N values. The millet grain δ15N values can serve as reliable indicators of manuring practices. Finally, we provide an interpretive framework for assessing the correlation between manuring levels and the δ15N values of archaeological millet remains. The δ15N values of ancient millet grains suggest widespread and intensive manuring practices in prehistoric millet agriculture in northern China, spanning from the early Yangshao period to the Longshan period.

起源于中国北方的小米农业与水稻农业共同孕育了中华文明。史前耕作方式很可能促进并维持了中国北方黄土地区可持续的粟农业生产。然而,关于狐尾黍(Setaria italica)和黍(Panicum miliaceum)史前耕作强度的指标一直存在争议。在此,我们介绍了对这两种小米进行盆栽和田间施肥试验的结果。我们的研究结果表明,施肥能显著提高狐尾粟的δ15N值,而且其δ15N值会随着施肥量的增加而增加。狐尾黍叶片的δ15N值系统地比谷粒的δ15N值高约1.6‰。施肥对提高土壤和黍作物的δ15N 值可能会产生长期的残余影响。结合之前的作物施肥实验结果,我们认为施肥对非固氮作物δ15N 值的影响大致是一致的。δ15N值和肥料量是决定植物δ15N值变化程度的关键因素。小米谷粒的δ15N值可作为肥料施用方法的可靠指标。最后,我们提供了一个解释性框架,用于评估施肥水平与考古小米遗存δ15N 值之间的相关性。古小米谷粒的δ15N值表明,从仰韶早期到龙山时期,中国北方史前小米农业中广泛而密集的施肥措施。
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引用次数: 0
Explainable artificial intelligence models for mineral prospectivity mapping 用于绘制矿产远景图的可解释人工智能模型
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-23 DOI: 10.1007/s11430-024-1309-9
Renguang Zuo, Qiuming Cheng, Ying Xu, Fanfan Yang, Yihui Xiong, Ziye Wang, Oliver P. Kreuzer

Mineral prospectivity mapping (MPM) is designed to reduce the exploration search space by combining and analyzing geological prospecting big data. Such geological big data are too large and complex for humans to effectively handle and interpret. Artificial intelligence (AI) algorithms, which are powerful tools for mining nonlinear mineralization patterns in big data obtained from mineral exploration, have demonstrated excellent performance in MPM. However, AI-driven MPM faces several challenges, including difficult interpretability, poor generalizability, and physical inconsistencies. In this study, based on previous studies, we devised a novel workflow that aims to constructing more transparent and explainable artificial intelligence (XAI) models for MPM by embedding domain knowledge throughout the AI-driven MPM, from input data to model design and model output. This newly proposed approach provides strong geological and conceptual leads that guide the entire AI-driven MPM model training process, thereby improving model interpretability and performance. Overall, the development of XAI models for MPM is capable of embedding prior and expert knowledge throughout the modeling process, presenting a valuable and promising area for future research designed to improve MPM.

矿产远景测绘(MPM)旨在通过组合和分析地质找矿大数据来缩小勘探搜索空间。此类地质大数据过于庞大和复杂,人类无法有效处理和解释。人工智能(AI)算法是在矿产勘探大数据中挖掘非线性成矿模式的有力工具,在 MPM 中表现出了卓越的性能。然而,人工智能驱动的 MPM 面临着一些挑战,包括难以解释、普适性差和物理不一致性等。在本研究中,我们在以往研究的基础上设计了一种新的工作流程,旨在通过将领域知识嵌入人工智能驱动的 MPM(从输入数据到模型设计和模型输出),为 MPM 构建更加透明和可解释的人工智能(XAI)模型。这种新提出的方法提供了强大的地质和概念线索,指导整个人工智能驱动的 MPM 模型训练过程,从而提高了模型的可解释性和性能。总体而言,为 MPM 开发 XAI 模型能够在整个建模过程中嵌入先验知识和专家知识,为旨在改进 MPM 的未来研究提供了一个有价值、有前景的领域。
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引用次数: 0
Predict the spatiotemporal distribution of solar magnetic field and understand the evolutionary feature of solar activity 预测太阳磁场的时空分布,了解太阳活动的演变特征
IF 6 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-18 DOI: 10.1007/s11430-024-1382-2
Jingxiu Wang
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引用次数: 0
Elevation of basal lacustrine sediments along the mid-lower reaches of the Yangtze River and its implications for the reconstruction of Holocene water levels 长江中下游基底湖相沉积的抬升及其对全新世水位重建的影响
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-18 DOI: 10.1007/s11430-023-1374-y
Shuchun Yao, Chunhai Li, Bin Xue

The middle and lower reaches of the Yangtze River, a primary region for freshwater lakes in China, have undergone significant transformations throughout the Holocene. These changes, driven by factors such as sea-level rise, climate change, and human activities, have led to the progressive elevation of water levels in this area. As a result, a floodplain has emerged, characterized by the formation of numerous shallow lakes along the river course. However, the pattern of water-level changes in the main channel of the Yangtze River during the Holocene remains unclear. This gap in knowledge poses challenges for understanding sediment transport dynamics, the interactions between the river and its adjacent lakes, and the prevention and control of flood disasters in the Yangtze River basin. To shed light on these issues, our study compiled data on the surface elevation and water depth of 81 lakes in the mid-lower reaches of the Yangtze River basin. Additionally, we analyzed historical water-level records from the 1900s to the 1970s at eight gauging stations from Shashi to Jiangyin along the river’s main stream. Our findings reveal that, particularly along the Jingjiang section, the basal elevation of most lakes is lower than the Yangtze River’s water level during the dry season. Conversely, the water level of the main stream exceeds that of both the floodplain and the lakes enclosed by the Jingjiang embankment. In the tidal reach, especially within the Taihu Lake basin, the basal elevation of lakes typically falls below sea level. Meanwhile, lakes located along the section from Chenglingji to Wuhu exhibit basal elevations that correspond with the Yangtze River’s annual average and dry season water levels. Given the widespread presence of lakes along the middle and lower reaches of the Yangtze River, our study introduces a new proxy for reconstructing the mean water level of the mid-lower Yangtze River in the Holocene. By analyzing sediments from Nanyi Lake and Chenyao Lake in the lower Yangtze River, we attempted to reconstruct the water level of the Yangtze River’s main channel since 8 ka BP.

长江中下游是中国淡水湖泊的主要区域,在整个全新世期间经历了重大变化。在海平面上升、气候变化和人类活动等因素的推动下,这些变化导致该地区的水位逐渐升高。因此,出现了一个洪泛平原,其特点是沿河道形成了许多浅湖。然而,全新世期间长江主航道的水位变化规律仍不清楚。这一知识空白对理解长江流域的泥沙输移动力学、河流与邻近湖泊之间的相互作用以及洪水灾害的防控提出了挑战。为了揭示这些问题,我们的研究汇编了长江流域中下游 81 个湖泊的湖面高程和水深数据。此外,我们还分析了从 20 世纪到 20 世纪 70 年代长江干流沙市至江阴沿线八个测站的历史水位记录。我们的研究结果表明,尤其是在荆江段,大多数湖泊的基底高程在枯水期低于长江水位。相反,干流的水位则超过洪泛区和荆江大堤所围湖泊的水位。在潮汐区,尤其是太湖流域内,湖泊的基底标高通常低于海平面。同时,位于城陵矶至芜湖段的湖泊的基底高程与长江的年平均水位和枯水期水位一致。鉴于长江中下游湖泊的广泛存在,我们的研究为重建全新世长江中下游的平均水位提供了新的替代方法。通过分析长江下游南漪湖和陈瑶湖的沉积物,我们试图重建公元前 8 kaP 年以来长江主航道的水位。
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引用次数: 0
Monazite U-Th-Pb and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit in the Qinling orogen, central China: Implications for regional gold metallogeny 中国中部秦岭造山带夏家店黑页岩型金矿床的独居石U-Th-Pb和绢云母Rb-Sr年代测定:对区域金成矿作用的影响
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-18 DOI: 10.1007/s11430-023-1322-y
Xueling Yu, Jianwei Li, Xiaoye Jin, Shaorui Zhao, Chongguo He, Yunlong Zhu

The Qinling orogen in central China contains several black shale-hosted gold deposits, but the age of their formation and a possible relation between gold mineralization and regional tectonism remain undetermined. Here we present results of in situ monazite U-Th-Pb dating and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit to provide tight constraints on the time of gold deposition and information on the tectonic setting under which the deposit formed. The Xiajiadian gold deposit is mainly hosted in black shales of the Lower Cambrian Shuigoukou formation, with minor ores contained in sandy conglomerate of the Lower Devonian Xichahe formation. Gold ores in the black shales have been intensively oxidized and consist mainly of hematite, goethite, gypsum, quartz, calcite, native gold, and unrecognized iron oxides. However, gold ores in the sandy conglomerate are free of oxidation and thus provide an opportunity to date the formation of the Xiajiadian gold deposit. The ores consist of pyrite, marcasite, sericite, and quartz, which are associated with a variety of accessory minerals, including monazite, apatite, and titanite. Gold is mainly present as structure-bound ions or nanoparticles in pyrite and marcasite, but minor native gold grains also occur as inclusions in pyrite. Monazite is well developed in the ores, and has close textural association with Au-bearing pyrite and marcasite. Most monazite grains have zoned textures consisting of a core area (Mnz1) and an overgrowth zone (Mnz2). Mnz1 contains 4.8–13 wt.% ThO2 and shows large variations in HREE and prominent negative Eu anomalies in the chondrite-normalized REE patterns. It yields common lead-corrected 208Pb/232Th dates ranging from 910±10 to 416±4 Ma (2σ). These dates are interpreted in terms of a detrital origin for monazite in the core area. Mnz2 has much lower ThO2 contents of 0.8–1.7 wt.% and shows weak negative Eu anomalies in the chondrite-normalized REE patterns. It yields common lead-corrected 208Pb/232Th dates of 229–209 Ma (2σ) with a weighted mean of 217.6±3.0 Ma (2σ), which is considered as the time of Mnz2 crystallization. Sericite in gold ores and associated alteration zones has close relations to Au-bearing pyrite and marcasite, and yields a well-defined Rb-Sr isochron age of 222.2±3.3 Ma (2σ). The sericite Rb-Sr age is indistinguishable within analytical errors from the weighted mean Th-Pb age of Mnz2. The age data presented here indicate that the Xiajiadian gold deposit formed at ca. 220 Ma in the Late Triassic (Norian). We therefore suggest that gold mineralization at Xiajiadian occurred during the transitional stage from oceanic subduction to continental collision that led to the formation of the Qinling orogen. During this stage, metamorphic devolatization of the underlying Early Paleozoic to Proterozoic carbonaceous sequences likely supplied ore fluids from which the Xiaj

中国中部的秦岭造山带蕴藏着多个黑页岩型金矿床,但其形成年代以及金矿化与区域构造的可能关系仍未确定。在此,我们介绍了夏家店黑页岩型金矿床的原位独居石U-Th-Pb定年和绢云母Rb-Sr定年结果,为金的沉积时间提供了严格的限制,并提供了该矿床形成的构造环境信息。夏家店金矿床主要赋存于下寒武统水口组黑色页岩中,少量矿石赋存于下泥盆统西岔河组砂砾岩中。黑色页岩中的金矿石已被严重氧化,主要由赤铁矿、高铁锰矿、石膏、石英、方解石、原生金和未识别的铁氧化物组成。然而,砂质砾岩中的金矿石没有被氧化,因此为夏家店金矿床的形成提供了一个年代测定的机会。矿石由黄铁矿、云母石、绢云母和石英组成,并伴生有多种附属矿物,包括独居石、磷灰石和榍石。金主要以结构结合离子或纳米颗粒的形式存在于黄铁矿和黑云母中,但也有少量原生金粒以包裹体的形式存在于黄铁矿中。独居石在矿石中发育良好,并与含金黄铁矿和云母石有着密切的纹理联系。大多数独居石晶粒具有分带纹理,由核心区(Mnz1)和过度生长区(Mnz2)组成。Mnz1 含有 4.8-13 重量%的二氧化硫,在软玉归一化 REE 模式中显示出较大的 HREE 变化和突出的 Eu 负异常。它产生了常见的铅校正 208Pb/232Th 年代,范围从 910±10 到 416±4 Ma (2σ)。这些日期被解释为核心区独居石的碎屑起源。Mnz2的二氧化硫含量要低得多,为0.8-1.7 wt.%,在软玉归一化的REE模式中显示出弱的负Eu异常。它产生的普通铅校正 208Pb/232Th 年代为 229-209 Ma (2σ),加权平均值为 217.6±3.0 Ma (2σ),这被认为是 Mnz2 的结晶时间。金矿石和相关蚀变带中的绢云母与含金黄铁矿和云母关系密切,并产生了明确的Rb-Sr等时线年龄222.2±3.3 Ma (2σ)。绢云母的 Rb-Sr 年龄与 Mnz2 的 Th-Pb 加权平均年龄在分析误差范围内没有区别。本文提供的年龄数据表明,夏家店金矿床形成于三叠纪晚期(诺日朗期)约 220 Ma 处。因此,我们认为夏家店的金矿化发生在秦岭造山带从大洋俯冲到大陆碰撞的过渡阶段。在这一阶段,下伏早古生代至新生代碳质岩层的变质脱落可能为夏家店金矿床的形成提供了矿石流体。
{"title":"Monazite U-Th-Pb and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit in the Qinling orogen, central China: Implications for regional gold metallogeny","authors":"Xueling Yu, Jianwei Li, Xiaoye Jin, Shaorui Zhao, Chongguo He, Yunlong Zhu","doi":"10.1007/s11430-023-1322-y","DOIUrl":"https://doi.org/10.1007/s11430-023-1322-y","url":null,"abstract":"<p>The Qinling orogen in central China contains several black shale-hosted gold deposits, but the age of their formation and a possible relation between gold mineralization and regional tectonism remain undetermined. Here we present results of <i>in situ</i> monazite U-Th-Pb dating and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit to provide tight constraints on the time of gold deposition and information on the tectonic setting under which the deposit formed. The Xiajiadian gold deposit is mainly hosted in black shales of the Lower Cambrian Shuigoukou formation, with minor ores contained in sandy conglomerate of the Lower Devonian Xichahe formation. Gold ores in the black shales have been intensively oxidized and consist mainly of hematite, goethite, gypsum, quartz, calcite, native gold, and unrecognized iron oxides. However, gold ores in the sandy conglomerate are free of oxidation and thus provide an opportunity to date the formation of the Xiajiadian gold deposit. The ores consist of pyrite, marcasite, sericite, and quartz, which are associated with a variety of accessory minerals, including monazite, apatite, and titanite. Gold is mainly present as structure-bound ions or nanoparticles in pyrite and marcasite, but minor native gold grains also occur as inclusions in pyrite. Monazite is well developed in the ores, and has close textural association with Au-bearing pyrite and marcasite. Most monazite grains have zoned textures consisting of a core area (Mnz1) and an overgrowth zone (Mnz2). Mnz1 contains 4.8–13 wt.% ThO<sub>2</sub> and shows large variations in HREE and prominent negative Eu anomalies in the chondrite-normalized REE patterns. It yields common lead-corrected <sup>208</sup>Pb/<sup>232</sup>Th dates ranging from 910±10 to 416±4 Ma (2σ). These dates are interpreted in terms of a detrital origin for monazite in the core area. Mnz2 has much lower ThO<sub>2</sub> contents of 0.8–1.7 wt.% and shows weak negative Eu anomalies in the chondrite-normalized REE patterns. It yields common lead-corrected <sup>208</sup>Pb/<sup>232</sup>Th dates of 229–209 Ma (2σ) with a weighted mean of 217.6±3.0 Ma (2σ), which is considered as the time of Mnz2 crystallization. Sericite in gold ores and associated alteration zones has close relations to Au-bearing pyrite and marcasite, and yields a well-defined Rb-Sr isochron age of 222.2±3.3 Ma (2σ). The sericite Rb-Sr age is indistinguishable within analytical errors from the weighted mean Th-Pb age of Mnz2. The age data presented here indicate that the Xiajiadian gold deposit formed at ca. 220 Ma in the Late Triassic (Norian). We therefore suggest that gold mineralization at Xiajiadian occurred during the transitional stage from oceanic subduction to continental collision that led to the formation of the Qinling orogen. During this stage, metamorphic devolatization of the underlying Early Paleozoic to Proterozoic carbonaceous sequences likely supplied ore fluids from which the Xiaj","PeriodicalId":21651,"journal":{"name":"Science China Earth Sciences","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141745762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Status and trends in the stability of the three largest ice shelves in Antarctica 南极洲三个最大冰架的稳定性现状和趋势
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-17 DOI: 10.1007/s11430-023-1338-8
Rongxing Li, Guojun Li, Lu An, Menglian Xia, Da Lv, Yuan Cheng, Aiguo Zhao, Tian Chang, Xiangbin Cui, Shengkai Zhang, Shijie Liu, Yixiang Tian, Weian Wang

The Ross, Filchner-Ronne, and Amery ice shelves are the three largest ice shelves in Antarctica, playing a crucial role in supporting the Antarctic ice sheet. However, current studies on the stability of the three largest ice shelves primarily focus on singular or limited factors, lacking a comprehensive assessment of multiple parameters. To systematically and in-depth study the stability and trend of the three largest ice shelves, we comprehensively collected and analyzed key parameters, including elevation changes, basal melting, surface meltwater, major rifts propagation rate, suture zones, ice front area change rate, grounding lines, ice velocity, and mass balance. Additionally, we selected the collapsed Larsen B Ice Shelf (LBIS), the rapidly changing and structurally weakened Pine Island Ice Shelf (PIIS), and the accelerating Totten Ice Shelf (TIS) as reference ice shelves. By comparing and analyzing the key parameters between these reference ice shelves and the three largest ice shelves, we find the status and trends in the stability of the latter. Our findings reveal that most key parameters of the three largest ice shelves present relatively minor variations compared to those of the reference ice shelves. Specifically, 50% of the parameters are smaller than those of the accelerating TIS, 88% are smaller than those of the rapidly changing PIIS, and all parameters are smaller than those of the collapsed LBIS. Furthermore, after analyzing parameters that are not smaller than those of the TIS, it is observed that they remain in a stable state. Hence, the three largest ice shelves are currently undergoing natural changes that do not threaten their stability in the short term. Nevertheless, the evolution of the ice shelves under global climate change remains uncertain, making long-term observation and monitoring essential to assess their impact on sea level rise.

罗斯冰架、菲尔赫纳-龙恩冰架和阿梅里冰架是南极洲最大的三个冰架,在支撑南极冰盖方面起着至关重要的作用。然而,目前对这三个最大冰架稳定性的研究主要集中在单一或有限的因素上,缺乏对多个参数的综合评估。为了系统深入地研究三大冰架的稳定性及其变化趋势,我们全面收集和分析了包括海拔变化、基底融化、表面融水、主要裂口传播速度、缝合带、冰前面积变化率、接地线、冰速和质量平衡等在内的关键参数。此外,我们还选择了坍塌的拉森 B 冰架(LBIS)、快速变化且结构减弱的松岛冰架(PIIS)和加速的托顿冰架(TIS)作为参考冰架。通过比较和分析这些参照冰架与三个最大冰架之间的关键参数,我们发现了后者的稳定性现状和趋势。我们的研究结果表明,与参照冰架相比,三个最大冰架的大多数关键参数变化相对较小。具体来说,50%的参数小于加速变化的 TIS,88%的参数小于快速变化的 PIIS,而所有参数都小于坍塌的 LBIS。此外,在对不小于 TIS 的参数进行分析后发现,它们仍处于稳定状态。因此,这三个最大的冰架目前正在经历自然变化,短期内不会威胁其稳定性。然而,冰架在全球气候变化下的演变仍不确定,因此必须进行长期观测和监测,以评估它们对海平面上升的影响。
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引用次数: 0
Segmental nature of the Red River fault revealed by seismic anisotropy and geological structures 地震各向异性和地质结构揭示的红河断层分段性质
IF 5.7 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-07-17 DOI: 10.1007/s11430-023-1311-0
Ying Li, Yuan Gao

As the western boundary of the Sichuan-Yunnan block (SYB), the Red River fault (RRF) is a major fault that controls deep crustal movement and deformation in the southeast margin of the Tibetan Plateau and regulates middle-lower crustal flow. Geophysical data suggest that the RRF is segmented and exhibits distinct variations in seismicity, velocity structure and crustal deformation from north to south. Seismic anisotropy reveals a complex pattern of lateral spatial and vertical stratified distributions. (1) From the perspective of crustal stratification, in the upper crust, the fast wave polarization in the north segment of the RRF is complex and possibly influenced by the Sanjiang lateral collision zone and adjacent faults with varying strikes. The fast wave polarization in the middle segment is in the NW-SE direction, indicating a localized area of closed down or locked up with consistent deformation. And in the south segment, it presents a disordered pattern, signifying complex deep tectonics and stress conditions at the wedged intersection zone. In the middle-lower crust in the north and south segments of the RRF, the azimuthal anisotropy is strong and consistent with the spatial strike of the weak zone characterized by low-velocity and high-conductivity. This suggests a connection between the anisotropy and the material migration. (2) In the whole crustal scale, the fast wave directions in two sides of the RRF are consistent with the NW-SE tectonic strike. It indicates that the RRF, as a large fault potentially cutting through the whole crust, strongly controls the surrounding media. (3) In the lithospheric scale, the fast wave polarizations are oriented nearly E-W and independent of the fault strike, consistent with the low P- and S-wave velocity structures and positive radial anisotropy in the upper mantle. The fast wave directions could be related to lithospheric olivine deformation and asthenospheric flow. This paper suggests a decoupling of deformation between the crust and the lithospheric mantle in the south of approximately 26°20′N near the RRF, which can potentially be attributed to the subduction and rollback of the Indian plate. Based on various geophysical observations and inversions, we can determine the detailed anisotropic structure in the crust and the upper mantle around the RRF. Denser geophysical arrays and more accurate records can be used to explore the intricate anisotropy in segmentation and stratification around the RRF, enhancing the understanding of its tectonic significance.

作为四川-云南断块(SYB)的西部边界,红河断层(RRF)是控制青藏高原东南缘深部地壳运动和变形、调节中下地壳流动的主要断层。地球物理数据表明,红河断层是分段的,从北到南在地震活动性、速度结构和地壳变形方面表现出明显的差异。地震各向异性揭示了横向空间和纵向分层分布的复杂模式。(1)从地壳分层的角度看,在上地壳中, RRF 北段快波极化复杂,可能受到三江侧向碰撞带和相邻不同走向断层的影响。中段的快波极化方向为NW-SE向,表明局部地区有持续变形的闭锁或锁闭。而在南段,快波极化呈现无序形态,表明楔形交汇带的深部构造和应力条件复杂。在RRF北段和南段的中下地壳,方位各向异性很强,与以低速高导为特征的弱区空间走向一致。这表明各向异性与物质迁移之间存在联系。(2)在整个地壳尺度上,RRF两侧的快波方向与NW-SE构造走向一致。这表明,RRF 作为一个可能切割整个地壳的大型断层,对周围介质具有强烈的控制作用。(3) 在岩石圈尺度上,快波极化方向接近于 E-W,且与断层走向无关,这与上地幔的低 P 波和 S 波速度结构以及正径向各向异性相一致。快波方向可能与岩石圈橄榄岩变形和星体层流动有关。本文认为,在 RRF 附近约 26°20′N 的南部,地壳与岩石圈地幔之间的变形脱钩,这可能是印度板块俯冲和回滚造成的。根据各种地球物理观测和反演,我们可以确定 RRF 周围地壳和上地幔的详细各向异性结构。可以利用更密集的地球物理阵列和更精确的记录来探索 RRF 周围分段和分层中错综复杂的各向异性,从而加深对其构造意义的理解。
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