准噶尔盆地北部基底结构与属性问题探讨

准噶尔盆地的基底结构与属性一直是地学界关注的焦点问题之一.横跨准噶尔盆地北部,走向近东西的克拉玛依—喀姆斯特地震剖面提供了该盆地北部详细的地壳与上地幔顶部的速度结构与构造,特别是基底顶界面的速度.沿剖面发现了数条走向近南北的“H”型超壳断裂,它们没有明显的断差,断裂处反射系数明显降低,介质的Q值减小,推测具“开裂”性质;利用盆地内1:20万重磁数据完成了重磁联合反演,获得了沿剖面的地壳与上地幔顶部的二维密度结构与二维磁性结构.根据在一定深度范围内介质的速度-密度-岩性之间的关系,确定了盆地北部基底岩性分布.结果表明,准噶尔盆地北部的基底多处为基性和超基性物质,推测为深部（上地幔）物质沿超壳断裂进入地壳内部并对地壳物质进行改造的结果.这一推断得到盆地内部高磁性、高重力异常的支持,也与盆地具有较高的地壳平均速度相一致.综合其他地球物理与地质资料综合分析,给出了综合地质解释剖面,建立了准噶尔盆地北部基底结构与属性的动力学模型.     

新疆玛纳斯大震区地壳深部的电性结构

对玛纳斯大震区新近观测的大地电磁测深数据进行了处理,得到视电阻率曲线、阻抗相位曲线、二维偏离度、主轴方位角和地磁实感应矢量。然后对所有测点的资料进行了二维自动反演解释。结果表明,沿剖面的地壳浅部可划分为５个区段,沿剖面的深部可划分为３个区段,各区段的接触边界由断层或深断裂带组成。沿测线沉积盖层最大深度达１２ｋｍ左右;测线南段存在壳内低阻体。这些解释结果与地质及其它资料吻合较好。玛纳斯７．７级地震发生在地壳电性结构发生明显变化的接触带附近     

阵列式光纤地震仪在西藏易贡湖地区的浅层探测实验研究

随着野外观测数据的累积和地震成像技术的发展,对地球内部结构的探测范围越来越大,精度越来越高.利用新的技术手段获得更多的观测数据,不仅填补了研究区观测数据的空白,还有助于提高地下结构的探测精度.利用光纤地震仪耐极端环境和易于布设等优势,本研究使用自主研发的阵列式光纤地震仪在西藏易贡湖地区进行野外试验,首次获得了青藏高原地区主动源和背景噪声的光纤地震数据(包含一条水下测线的数据).利用背景噪声成像手段得到了易贡湖岸近地表S波速度结构,但未获得湖底的速度结构.经分析认为,湖水的流动对架设于湖底的探头造成了干扰.本次试验初步验证了阵列式光纤地震仪在极端野外环境中(尤其是水下)进行数据采集的可行性,为未来在极端环境下的数据采集提供了新思路.     

Ordovician Proto–basin in South China and its Tectonic Implications: Evidence from the Detrital Zircon U–Pb Ages of the Ordovician in Central Hunan, China

Caledonian orogeny is another important tectonic event in South China Block after the breakup of the Rodinia supercontinent. With a view to constrain the tectonic evolution and proto–basin in South China, this paper reports the geochemical and zircon U-Pb dating data of the Ordovician strata in central Hunan, South China. Geochemical features and paleocurrent directions suggest that the lower Ordovician deposited in a passive continental margin basin with a provenance of quartzose components and showing an affinity with the Yangtze Block. U-Pb age data for 260 detrital zircons from upper Ordovician identify three major age populations as: 900–1200 Ma, 1400–1800 Ma and 2400–2700 Ma. The detrital zircon age spectrum as well as the paleocurrent directions suggest that upper Ordovician deposited in a foreland basin and showing a close affinity with the Cathaysia Block. It is also suggest that the lower Ordovician continuously accepted the mineral from the Yangtze Block, whereas the provenance of the upper Ordovician sedimentary basin changed from the Yangtze Block to the Cathaysia Block. This change implies a tectonic movement, which caused the transformation of the proto–basin in the Hunan area in SCB from passive continental margin basin to foreland basin probably took place during late Ordovician. This fact also demonstrate that the Caledonian orogeny in South China Block began no later than 453 Ma, and a new crustal evolution model is proposed.     

Platinum-Group Elements Constraint on the Origin Mechanism of the Hetaoshu Rich-PGE Deposit in the Xiaoguanhe Region, Panxi Area

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The Re-Os Isotope Geochronology of Dapai Iron Polymetallic Ore Deposit in Yongding County, Fujian Province and its Genetic Significance

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A Study of Structure and Mechanism of a Meso-beta-scale Convective Vortex and Associated Heavy Rainfall in the Dabie Mountain Area Part I: Diagnostic Analysis of the Structure

An analysis was conducted on the evolutional process of a mesoscale convective vortex (MCV) and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in different stages,by using the mesoscale reanalysis data with 3 km and 1 h resolution generated by the Local Analysis and Prediction System (LAPS) in the Southern China Heavy Rainfall Experiment.The results showed that the latent heat released by convection in the midtroposphere was the main energy source for the development of a low-level vortex.There was a positive feedback interaction between the convection and the vortex,and the evolution of the MCV was closely related to the strength of the positive interaction.The most typical characteristics of the thermal structure in different stages were that,there was a relatively thin diabatic heating layer in the midtroposphere in the formative stage;the thickness of diabatic heating layer significantly increased in the mature stage;and it almost disappeared in the decay stage.The characteristics of the dynamic structure were that,in the formative stage,there was no anticyclonic circulation at the high level;in the mature stage,an anticyclonic circulation with strong divergence was formed at the high level;in the decay stage,the anticyclonic circulation was damaged and the high-level atmosphere was in a disordered state of turbulence.Finally,the structural schematics of the MCV in the formative and mature stage were established respectively.     

Ground-Based Atmospheric CO2, CH4, and CO Column Measurements at Golmud in the Qinghai-Tibetan Plateau and Comparisons with TROPOMI/S5P Satellite Observations

Measurements of carbon dioxide(CO₂), methane(CH₄), and carbon monoxide(CO) are of great importance in the Qinghai-Tibetan region, as it is the highest and largest plateau in the world affecting global weather and climate systems. In this study, for the first time, we present CO₂, CH₄, and CO column measurements carried out by a Bruker EM27/SUN Fourier-transform infrared spectrometer(FTIR) at Golmud(36.42°E, 94.91°N, 2808 m) in August 2021. The mean and...     

Source mechanism of strong aftershocks (M_s≥5.6) of the 2008/05/12 Wenchuan earthquake and the implication for seismotectonics

Dozens of >M5, hundreds of >M4, and much more >M3 aftershocks occurred after the 2008/05/12 Wenchuan earthquake, which were well recorded by permanent and portable seismic stations. After relocated with P arrival, the >M3 aftershocks show two trends of distribution, with most of the aftershocks located along the north-east strike consistent with Longmenshan fault system, yet there is a north-west trend around the epicenter. It seems that substantially more aftershocks occur in regions with crystalline bedro...