东秦岭东段新发现的沙坡岭细脉浸染型钼矿地质特征、Re-Os同位素年龄及其地质意义

豫西洛宁沙坡岭钼矿床位于华北克拉通南缘东秦岭钼矿带东段,是新近发现的赋存于太古宙太华群变质岩中的细脉浸染型钼矿床。本文对其地质特征进行了研究,并初步测定了1个辉钼矿样品的Re－Os同位素年龄,获得模式年龄为126.8±1.7Ma,表明沙坡岭钼矿形成于燕山期,接近金堆城、雷门沟钼矿的形成时代,Re同位素含量显示其地幔来源的特征。沙坡岭钼矿形成机制错综复杂,有待进一步研究,特别是深部钻孔工程验证工作,对于验证深部是否隐伏着与成矿相关的斑岩体、储量更大的斑岩型钼矿有着重要作用,找矿潜力巨大。     

Episodic crustal growth of North China as revealed by U-Pb age and Hf isotopes of detrital zircons from modern rivers

Clastic sedimentary rocks are samples of the exposed continental crust. In order to characterize the crustal growth history of North China and its possible regional variations, 479 concordant detrital zircons in three sand samples from the lower reach of the Yellow River (which drains the Tibet-Qinghai Plateau, the Western Qinling Orogen, the Qilian Orogen and the North China Craton) and two sand samples from the Luan River and the Yongding River (which run entirely within the North China Craton) were measured for U-Pb age and Lu-Hf isotopic compositions by excimer laser-ablation ICP-MS and MC-ICP-MS. Although regional variations exist, concordant detrital zircons from the Yellow River reveal three major age groups of 2.1-2.5 Ga, 1.6-2.0 Ga, and 150-500 Ma. Detrital zircons from the smaller Luan and Yongding Rivers show three broadly similar major age groups at 2.3-2.6 Ga, 1.6-2.0 Ga, and 140-350 Ma, but with narrower age ranges. Compared to the Luan and Yongding River zircons, the Yellow River zircons are characterized by a significant number of Neoproterozoic grains. Although Hf isotopic compositions show both juvenile crustal growth and crustal reworking for all age groups, much of the crustal growth of North China occurred in the Neoarchean and Mesoproterozoic. All three rivers are characterized by a common prominent group of Hf crust formation model ages at 2.4-2.9 Ga with a peak at 2.7-2.8 Ga. A less significant age group lies between 1.4 and 1.8 Ga for the Yellow River, and between 1.6 and 1.9 Ga for the Yongding River and Luan River. Crustal growth rates based on Hf continental crust formation model ages suggest 45% and 90% of the present crustal volume was formed by 2.5 Ga and 1.0 Ga, respectively, for the drainage area of the Yellow River. In comparison, 60% and 98% of the present crustal volume of the North China Craton was generated by 2.5 Ga and 1.0 Ga, respectively, for the Luan and Yongding Rivers. The 2.7-2.8 Ga age peak observed in all river samples agrees well with the coeval major peak for global crustal growth. However, the other suggested global peaks of crustal growth at 3.4 and 3.8 Ga are insignificant in North China. Taken together with our previous studies of the Yangtze Craton, which show insignificant crustal growth at 2.7-2.8 Ga, we suggest that these advocated worldwide crust formation peaks be re-examined and treated carefully. Our results also show that Phanerozoic zircons may have been derived from crustal sources separated from the mantle up to 2.0 Ga ago before the zircons crystallized, suggesting long-term preservation, reworking and recycling of the continental crust.     

微波消解等离子体发射光谱和石墨炉原子吸收光谱法联合测定土壤中多元素

采用密闭式微波消解系统处理土壤样品,电感耦合等离子体发射光谱法或石墨炉原子吸收光谱法测定土壤样品中铜、砷、铅、锌、钴、铬、锰、镍、钒9个元素。分别从消解液的选择、用酸量及样品消解量等方面进行消解条件的优化,确定了一个最适合土壤消解的前处理体系。各元素的检出限为0.16～2.52μg/g,回收率为95.2%～106.6%,精密度为2.03%～9.79%(n=7)。方法简单快速,效率高,劳动强度低,是进行土壤中多元素测定的高效方法。     

晓天—磨子潭韧性剪切带变形模拟及其对北大别穹隆构造演化的指示

现今出露在北大别穹隆北界上的晓天—磨子潭韧性剪切带是早白垩世造山后伸展活动的产物。野外观测、室内石英C轴组构与运动学涡度测量指示,这一NWW—SEE走向、倾向NNE的韧性剪切带,呈现为正左旋走滑运动,以简单剪切变形为主。该剪切带内现今所保留运动学特征及其在空间上的变化反映其形成后经历过旋转改造。以实测组构为约束的变形模拟揭示,该剪切带在早期伸展活动时为中地壳内上盘向280°方位运动的水平韧性剪切带,后在北大别穹隆上拱中被动地抬升而成为现今状态。北大别穹隆西强东弱的上隆幅度是晓天—磨子潭韧性剪切带被不均匀抬升和旋转的主要原因。该剪切带与北大别穹隆皆为早白垩世造山后重力垮塌中形成的,具有科迪勒拉型变质核杂岩特征。     

川东“侏罗山式”褶皱的数值模拟及成因探讨

本文通过采用有限差分法（FLAC）对“侏罗山式”褶皱进行数值模拟发现,层间粘聚力差异和上覆压力是控制隔档式褶皱、隔槽式褶皱样式的主要因素,即层间的能干性差异和埋深的控制。当地层在埋深较浅时,层间能干性差异对褶皱样式起主控作用,能干性差异小时出现隔槽式褶皱,差异大时出现隔档式褶皱。随着埋深加大,压力逐渐起主要作用,这时仅出现隔槽式褶皱。川东东带褶皱地层总体上层间能干性差异小,因而盖层的深部与浅部皆出现隔槽式褶皱,与模拟结果一致。西带褶皱地层总体层间能干性差异大,因而浅部出现隔档式褶皱。而其深部的下古生界地层主要受上覆压力控制,根据模拟推测应为隔槽式褶皱。     

福建省沿海砂质岸线防护林分布特征及生态修复探讨

以2019年遥感卫星影像为基础,通过监督分类与目视解译相结合的方法,获得福建省砂质岸线防护林的分布现状,结合多时相遥感影像数据,总结防护林的退化变化规律.结果表明:尽管近几十年来福建省防护林保护与修复取得了显著成效,但也有将近一半的砂质岸线存在无防护林、原有防护林消失、防护林不连续、修复后再度遭受破坏等问题.针对这些问...     

渤海海冰微波散射特性研究

Microwave remote sensing has become the primary means for sea-ice research, and has been supported by a great deal of field experiments and theoretical studies regarding sea-ice microwave scattering. However, these studies have been barely carried in the Bohai Sea. The sea-ice microwave scattering mechanism was first developed for the thin sea ice with slight roughness in the Bohai Sea in the winter of 2012, and included the backscattering coefficients which were measured on the different conditions of three bands(L, C and X), two polarizations(HH and VV), and incident angles of 20° to 60°, using a ground-based scatterometer and the synchronous physical parameters of the sea-ice temperature, density, thickness, salinity, and so on. The theoretical model of the sea-ice electromagnetic scattering is obtained based on these physical parameters. The research regarding the sea-ice microwave scattering mechanism is carried out through two means, which includes the comparison between the field microwave scattering data and the simulation results of the theoretical model, as well as the feature analysis of the four components of the sea-ice electromagnetic scattering. It is revealed that the sea-ice microwave scattering data and the theoretical simulation results vary in the same trend with the incident angles. Also, there is a visible variant in the sensitivity of every component to the different bands.For example, the C and X bands are sensitive to the top surface, the X band is sensitive to the scatterers, and the L and C bands are sensitive to the bottom surface, and so on. It is suggested that the features of the sea-ice surfaces and scatterers can be retrieved by the further research in the future. This experiment can provide an experimental and theoretical foundation for research regarding the sea-ice microwave scattering characteristics in the Bohai Sea.     

巨厚灰岩油藏中隔夹层与高渗层成因与发育规律 ——以伊拉克H油田Mishrif组为例

隔夹层和高渗层是影响油田开发效果的重要因素.以伊拉克H油田Mishrif组为例,基于岩心和测井资料,在渗透率控制因素分析的基础上,研究了隔夹层和高渗层的成因类型与发育规律,并探讨了对油田开发的指导意义.Mishrif组生物碎屑灰岩渗透率与岩石结构、孔隙类型和成岩改造密切相关,受沉积和成岩作用的共同控制.隔夹层包括隔层、...     

金星的地幔对流、岩石圈演化和表面更新

金星在大小、轨道半径等方面与地球非常接近,但现今的观测显示金星在大气、表面温度、重力与地形特征等方面与地球非常不同.对固体金星而言,最显著特征是有火山活动但没有活动的板块构造运动、表面平均大约500±200 Ma的年龄显示金星发生过全球性表面快速更新、重力与地形强相关.本文在简要介绍已有工作的基础上,主要介绍我们基于这些观测特征开展的金星动力学研究,包括现今地幔的对流模式、相变对表面更新的影响、地壳厚度、岩石圈演化与表面更新等研究工作和取得的初步认识.     

利用GRACE数据联合新型尺度因子校正法提高陆地水储量变化准确性

本文围绕GRACE数据在信号处理过程中存在泄露误差开展了探索性研究.第一,在传统尺度因子法的基础上,根据模型与CSR-SHc数据的均方根误差和相关性赋予权重,构建了新型尺度因子校正法.第二,以长江流域为例,评估该方法的校正效果,研究结果表明:新型尺度因子校正法校正结果综合GLDAS(Global Land Data Assimilation System)水文模型计算的尺度因子校正结果空间分布趋势的优点,避免了 CSR(Center for Space Research)官方提供的尺度因子、WGHM(Water GAP Global Hydrology Model)尺度因子和迭代恢复法校正结果空间分布趋势不均匀的现象.在长期趋势上,该方法校正结果优于GLDAS水文模型计算的尺度因子校正结果;在周年振幅上,新型尺度因子校正法校正结果明显优于迭代恢复法和CSR Mascon数据的结果.第三,基于该方法校正结果显示,长江流域、上游和中下游在2002年4月-2017年1月水储量呈现上升趋势,分别为0.29 cm·a-1、0.14 cm·a-1和0.49 cm·a-1,相比于校正前CSR-SHc数据在长江流域、上游和中下游上升趋势0.21 cm·a-1、0.07 cm·a-1和0.40 cm·a-1,分别提高了 38％、100％和23％.长江流域水储量上升趋势主要集中在中下游.