西安河金矿床特征及找矿前景分析

西安河构造 (热液 )蚀变岩型金矿床 ,产于丹凤群及大草滩组发育的近EW向断裂破碎带内。矿床规模已达中型。矿石以低品位构造蚀变岩型为主 ,褐铁矿、黄铁矿是主要的载金矿物。围岩蚀变以硅化、褐铁矿化、黄铁矿化、绢云母化为特征。中基性火山岩、韧脆性断裂构造、中酸性岩浆侵入“三位一体”是控制矿床形成的基本条件。区内成矿条件优越 ,具有形成大型金矿的可能性 ,近EW向断裂蚀变延伸带是寻找金矿的有利地段。     

三峡坝区非对称共轭低缓角度剪破裂系

在岩石摩擦流变学理论指导下, 运用构造解析方法, 在三峡坝区岩体内多期的、复杂的破裂系统中, 识别出一个不对称的共轭低缓角度剪破裂系统.几何学和运动学标志证明, 这个影响大坝深层和浅层抗滑稳定性的共轭剪切破裂系统形成较早, 受岩体非均一性制约, 被后期破裂系统切错和改造, 是高流体压力控制下非对称共轴变形的结果.      

豫西秦岭群变质岩岩相学特征及早期地壳演化

豫西秦岭群是东秦岭褶皱带的核心岩系,具角闪岩相变质并有不同程度的混合岩化.空间上呈透镜状构造域,其内部可识别三期变形,韧性强应变带十分发育。变质岩系内主体岩石显示为成熟度不高的陆源碎屑沉积,是活动带沉积的特点,变质泥砂岩沉积的稀土组成及微量元素显示为后太古沉积的特征,而区内广泛分布的变质基性岩墙群,可代表早期的地壳拉张环境。     

Studying surface structure in desert areas using multiple kinds of surface wave data

Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan Desert area, we use the multi-channel analysis of surface wave （MASW） method to process multi-channel shallow surface wave records to determine the near surface velocity structure in the desert area. We also process, analyze, and compare the surface waves in many-trace records extracted from the oil exploration shot gathers in the area. We show that the MASW method can determine detailed shallow velocity structure in desert areas and the many-trace records can be used to get detailed deep geological structure. The combination of the two different datasets can obtain the exact velocity structure upper 60 m depth in the survey area.     

The influence of agriculture in the process of population integration and cultural interaction during the Eastern Zhou Period in central-south,Inner Mongolia: Carbon and nitrogen stable isotope analysis of human bones from the Dabaoshan cemetery,Helingeer County

Central-south Inner Mongolia, China, is highly sensitive to the cultural interactions between sedentary agriculturalists and nomadic pastoralists during the Eastern Zhou Period (770–256 BC). The previous pattern of multiple cultures and diverse ethnic groups has been transformed to the increasingly dominated cultural system of Central Plain since the middle and late Warring States Period, when the states of Zhao and Qin have conquered the most parts of central-south Inner Mongolia. However, the variation of subsistence strategies during this historical process has never been evaluated. Particularly, as the typical representative of Central Plain cultures, the effect of intensive millet agriculture is still unknown in the process of population integration and culture interaction. Thus, to explore the shift of subsistence pattern, carbon and nitrogen stable isotope analysis of bone collagen from Dabaoshan site (410–180 BC) have been performed. The isotopic result indicates a large amount of C4-based animal protein consumed by Dabaoshan humans. According to the archaeological backgrounds, we propose the Dabaoshan persons intensively relied on the millet agriculture and developed the agro-pastoral economy, which hinted the comprehensive influences from Central plain civilizations in late Warring States Period. Further compared with other published isotopic data in the same region during different periods, we suggest the millet agriculture has played the positive role in the process of population integration and culture fusion in central-south Inner Mongolia during the Eastern Zhou Period.     

Changes in Shale Rock Properties and Wave Velocity Anisotropy Induced by Increasing Temperature

Natural Resources Research - Water saturation, organic matter content, and fractures are important factors influencing the physical properties of shale. In this study, shale samples were subjected...     

天津蓟州五名山滑坡隐患早期识别监测

为精确识别五名山滑坡隐患,利用Sentinel-1A/B升降轨数据,基于SBAS-InSAR技术反演2017-03~2021-04该地区垂向和坡向形变,识别滑坡灾害以及隐患点,对形变时间序列及滑坡原因进行分析。结果表明,五名山潜在地质灾害隐患可分为3个区域,其中最大垂向累积形变达-38.28 mm,临空面坡体最大坡向累积形变为22.10 mm;降水量对坡体稳定性具有不同程度的影响,坡体累积形变峰值滞后于降水峰值。研究成果可回溯蓟州五名山滑坡灾害形变特征,为天津北部山区地质灾害监测识别提供新思路,为防灾减灾提供保障和技术支持。     

Superpenumbral chromospheric flare

We observed a C-class flare at the outer boundary of the superpenumbra of a sunspot. The flare was triggered by an emerging magnetic bipolar region that was obliquely oriented with respect to the superpenumbral fibrils. The flare started due to the low height magnetic reconnection of emerging magnetic flux with a superpenumbral field resulting in hot multi-temperature plasma flows in the inverse Evershed flow channel and its overlying atmosphere. Inverse Evershed flows in the chromosphere start from the superpenumbra towards the sunspot that end at the outer boundary of the penumbra. The hot plasma flow towards the sunspot in the inverse Evershed channels show about 10 km s~(-1) higher velocity in Hα wavelengths compared to the plasma emissions at various temperatures as seen in different AIA filters. Even though these velocities are about seven times higher than the typical inverse Evershed flow speeds, the flow is diminished at the outer boundary of the sunspot's penumbra. This suggests that the superpenumbral field lines that carry inverse Evershed flows are discontinued at the boundary where the penumbral field lines dive into the sun and these two sets of field lines are completely distinct. The discontinuity in the typical magnetic field and plasma properties at the adjoining of these two sets of field lines further leads to discontinuity in the characteristic magnetoacoustic and Alfv′en speeds, thereby stopping the plasma flows further on. The multi-temperature plasma in the inverse Evershed channels exhibits possible longitudinal oscillations initially during the onset of the flare, and later flows towards the sunspot. In the multi-temperature view, the different layers above the flare region have a mixture of supersonic as well as subsonic flows.     

Origin and model of transform faults in the Okinawa Trough

Transform faults in back-arc basins are the key to revealing the opening and development of marginal seas. The Okinawa Trough (OT) represents an incipient and active back-arc or marginal sea basin oriented in a general NE-SW direction. To determine the strikes and spatial distribution of transform faults in the OT, this paper dissects the NW- and NNE-SN-trending fault patterns on the basis of seismic profiles, gravity anomalies and region geological data. There are three main NW-trending transpressional faults in the OT, which are the seaward propagation of NW-trending faults in the East China Continent. The NNE-SN-trending faults with right-stepping distribution behave as right-lateral shearing. The strike-slip pull-apart process or transtensional faulting triggered the back-arc rifting or extension, and these faults evolved into transform faults with the emergence of oceanic crust. Thus, the transform fault patterns are inherited from pre-existing oblique transtensional faults at the offsets between rifting segments. Therefore, the OT performs the oblique spreading mechanism similar to nascent oceans such as the Red Sea and Gulf of Aden.     

Geochemistry and detrital zircon records of the Ruyang-Luoyu groups,southern North China Craton:Provenance,crustal evolution and Paleo-Mesoproterozoic tectonic implications

Paleo-to Mesoproterozoic sedimentary rocks in the southern margin of the North China Craton(NCC)are represented by the Ruyang and Luoyu groups.We studied the sedimentary rocks from the Yunmengshan and Beidajian formations of the Ruyang Group and the Cuizhuang and Sanjiaotang formations of the Luoyu Group.Detrital zircon grains from these formations have U–Pb age populations of 3.64–3.31 Ga,2.96–2.86 Ga,2.72–2.59 Ga,2.56–2.47 Ga,2.45–2.0 Ga,1.99–1.85 Ga and 1.84–1.65 Ga.The geochemical features of the sedimentary rocks suggest that some of the sediments were sourced from intermediate to felsic magmatic rocks.The age groups of the detrital zircon are roughly consistent with the tectono-thermal events in the southern margin of the NCC.The Hf isotopic compositions of detrital zircon from the sedimentary rocks in Ruyang and Luoyu groups suggest that significant crustal growth and reworking of the NCC took place during the Neoarchean and early-to mid-Paleoproterozoic,while crustal reworking at the Paleoarchean and late-Paleoproterozoic,and crustal growth at the Mesoarchean.We suggest the depositional times of the Ruyang Group and Luoyu Group are constrained to no older than 1.75–1.7 Ga and 1.7–1.65 Ga,respectively.Formation of late-Paleoproterozoic basins related to the strike slip and extrusion tectonics that cross-cut the NCC during the late Paleoproterozoic(<1.75 Ga),and the late Paleoproterozoic sedimentation once isochronous developed in the southern margin of the NCC through the Taihang region of the interior NCC and linked the Yanshan–Liaoxi regions of the northern NCC.