江苏土壤硒分布特征及富硒土地资源开发利用潜力

基于江苏1∶25万多目标区域地球化学调查的土壤Se含量数据,结合相关农业地质环境调查研究资料,总结土壤中Se分布的基本特点与规律,分析江苏有限富硒土地资源的开发利用潜力与对策。结果显示：在均匀覆盖全省的24 186个表层土壤样品中,富硒土壤（Se含量≥0.4 mg/kg）占比＜3%;全省土壤Se分布不均匀,耕层土壤富硒趋势相对明显,其中宜溧地区是全省富硒土壤分布最集中的地段,属于原岩风化残积型富硒土壤,当地已产出天然富硒大米与茶叶;全省富硒土壤有6个成因类型,成土母质与土壤类型差异是导致Se分布不均匀的重要因素;全省富硒土地资源开发利用潜力较大,开发过程中要做好生态富硒产业与重金属污染防治等统筹兼顾的5项规划,并尽早解决土壤-植物系统Se分布迁移的控制因素等4个技术瓶颈。     

南沙海域盆地群早中新世“挤压隆升幕”及其构造意义

本文依据南沙海域实际地震测线资料,相关证据显示早中新世（T₆₀-T₄₀之间）南沙腹地多盆地发生挤压反转构造,南沙西南部多见挤压褶皱。南沙海域及周边地区在早中新世开始发生全区的挤压隆升和剥蚀,经过局部剥蚀量和构造抬升量定量估算,认为隆升核心区域的九章盆地由于挤压隆升导致的地层剥蚀量大于3 500 m。“早中新世挤压隆升幕”形成一个以郑和隆起为核心的“碟形”剥蚀区,活动时间与西南次海盆的扩张时间一致,西南次海盆的扩张可能是造成隆升幕的重要原因。由于隆升剥蚀前存在深埋,南沙腹地（九章盆地为代表）和南沙北缘（中业、永登盆地为代表）的“浅、薄、小”盆地群的价值不容忽视。     

伽马蜡烷--水体分层的地球化学标志

密执安盆地等海相蒸发环境伽马蜡烷的分布表明,伽马蜡烷作为咸水环境的生物标志化合物与高盐度环境并没有绝对的对应关系;松辽盆地淡水－微咸水环境较高含量的伽马蜡烷表明其形成与湖海沟通引起的水体分层事件有关。伽马蜡烷重碳同位素值及微生物学证据均表明了伽马蜡烷的形成与水体分层有关,由于高盐环境往往伴随着密度分层,从而解释了伽马蜡烷经常与高盐环境伴生,但并不仅仅局限于高盐环境的现象。     

Early cretaceous subduction-related adakite-like rocks of the Gangdese Belt,southern Tibet: Products of slab melting and subsequent melt–peridotite interaction?

The limited geochronology and geochemistry data available for the Early Cretaceous igneous rocks of the southern Gangdese Belt, southern Tibet, has resulted in the proposal of conflicting geodynamic models for the generation of the widespread Cretaceous igneous rocks in the middle and northern parts of the belt. To explore this issue, we present SHRIMP U–Pb zircon data and geochemical and Sr–Nd–Pb–Hf isotopic data for the Mamen andesites from the southern margin of the Gangdese Belt. The Mamen andesites, emplaced at 136.5 Ma, are sodic (Na₂O/K₂O = 1.2–2.3) and have geochemical characteristics typical of adakites (i.e., high Al₂O₃, high La/Yb ratios and Sr contents, low Y and HREE contents, and positive Eu anomalies), except for high Cr, Ni, and MgO contents. The andesites have initial (⁸⁷Sr/⁸⁶Sr)_t ratios of 0.70413–0.70513, positive εNd(t) values of 3.7–5.8, and (²⁰⁶Pb/²⁰⁴Pb)_t ratios of 18.37–18.51, (²⁰⁷Pb/²⁰⁴Pb)_t ratios of 15.59–15.65, and (²⁰⁸Pb/²⁰⁴Pb)_t ratios of 38.43–38.72. In situ Hf isotopic analyses of zircons that had previously been dated by SHRIMP yielded positive initial εHf(t) values ranging from +11.0 to +15.5. A model calculation using trace element and Sr–Nd–Pb isotopic data indicates that several percent of subducted sediment is required to generate the Mamen andesites, which were derived via the partial melting of subducted Neo-Tethyan slab (MORB + sediment + fluid) and subsequently hybridized by peridotite in the mantle wedge. Our data indicate that the Neo-Tethyan oceanic crust was subducted northward beneath the Gangdese Belt during the Early Cretaceous at a high angle. Our results are inconsistent with a tectonic model that advocates the low-angle or flat-slab subduction of Neo-Tethyan oceanic crust in generating the widespread Cretaceous magmatism recorded in the Gangdese Belt.     

Discussion on moment tensor solution and seismogenic structure of Ruichang-Yangxin earthquake on 10 September 2011

Ruichang-Yangxin earthquake is another moderate earthquake in Yangxin-Jiujiang area since 2005 Jiujiang-Ruichang M5.7 earthquake. In order to more understand the seismic activities in this area, we study the moment tensor solution and the seismogenic structure of the Ruichang-Yangxin earthquake. Precise earthquake relocation shows that the mainshock occurred on the southwestern part of the NE-trending fault and aftershocks are distributed not only along the NE-trending fault but also along its conjugated NW-trending fault. By comprehensive analysis on the earthquake distribution, characteristics of isoseismal curve, focal mechanism, and regional structure characteristics, it is inferred that this earthquake is caused by the NE-trending Tanlu fault. In addition, it has close relationship with the conjugated NW-trending fault as well. Many researches have shown that the junction area is the earthquake-prone area, and should be paid more attention to. And our study also proves this viewpoint.     

Fluid identification based on P-wave anisotropy dispersion gradient inversion for fractured reservoirs

Fluid identification in fractured reservoirs is a challenging issue and has drawn increasing attentions. As aligned fractures in subsurface formations can induce anisotropy, we must choose parameters independent with azimuths to characterize fractures and fluid effects such as anisotropy parameters for fractured reservoirs. Anisotropy is often frequency dependent due to wave-induced fluid flow between pores and fractures. This property is conducive for identifying fluid type using azimuthal seismic data in fractured reservoirs. Through the numerical simulation based on Chapman model, we choose the P-wave anisotropy parameter dispersion gradient (PADG) as the new fluid factor. PADG is dependent both on average fracture radius and fluid type but independent on azimuths. When the aligned fractures in the reservoir are meter-scaled, gas-bearing layer could be accurately identified using PADG attribute. The reflection coefficient formula for horizontal transverse isotropy media by Rüger is reformulated and simplified according to frequency and the target function for inverting PADG based on frequency-dependent amplitude versus azimuth is derived. A spectral decomposition method combining Orthogonal Matching Pursuit and Wigner–Ville distribution is used to prepare the frequency-division data. Through application to synthetic data and real seismic data, the results suggest that the method is useful for gas identification in reservoirs with meter-scaled fractures using high-qualified seismic data.     

强地震动幅值谱随机涨落特征的研究

本文从工程应用的观点，将强地面运动幅值谱?Ａ（ｆ）│表示为强度受到调制的随机过程即│Ａ（ｆ）│＝│Ａ（ｆ）│〔１＋ｎ（ｆ）〕其中，│Ａ（ｆ）│为随频率变化的确定性函数亦是│Ａ（ｆ）│的均值，ｎ（ｆ）为均值为零的随机过程。在随机过程ｎ（ｆ）为各态历经的假定下，研究了ｎ（ｆ）的功率谱密度函数的特征及其衰减形式。根据地震学的有关理论，提出了用四个参数控制幅值谱的均值随频率变化的函数形式并对拟合这些参数的     

怀玉山地体略论

地质，地球化学和地球物理的综合分析表明，以赣东北断裂带，东乡－江山－绍兴断裂带和宁波－嵊泗断裂带围限的地区是一外来地体，其形成的构造环境与边缘海相当。晋宁期，该地体与扬子大陆边缘九岭区发生碰撞拼贴造山作用，相伴形成了一系列的碰撞造山构造。     

A fractional order creep constitutive model of warm frozen silt

A series of triaxial creep tests were conducted on warm frozen silts extracted from Qinghai–Tibet Plateau at temperature of ?1.5 °C under confining pressures of 0.5, 1.0, and 2.0 MPa, respectively. The applied test stress levels were 30, 50, 60, and 70% of triaxial shear strength, respectively. The test results indicate that the creep strain increases with the increase in applied stress level and there is a stress threshold, based on which the test results can be classified into two types of creep strain curves. The creep strain curve only includes primary and secondary creep stages when the stress level is less than the threshold value. When the stress level exceeds the threshold value, the creep strain velocity gradually increases and the specimen quickly fails in tertiary creep stage. Based on the creep test results, a fractional order rheological element model is established for warm frozen silt, which is also generalized from uniaxial stress state to the three-dimensional stress state. From the analysis on the features of the stress threshold, a creep strength criterion is also proposed simultaneously. Comparing the calculated results of the warm frozen silt with the tested ones, it is found that the predicted results of the proposed model are in good agreement with the test results. In the proposed fractional order model, the relationship between the damage factor and time is established to describe the damage degree of the specimen. Compared with the existing creep constitutive model of frozen soil, the proposed fractional order model has advantages of fewer model parameters, higher simulation precision and wider applicability in analyzing the mechanical properties of warm frozen silt.     

改进密云水库汛期调度方案的途径

密云水库是华北最大的水库，确定密云水库汛期调度方案的原则是２０年前制定的，按现代观点看来，其设计防洪库容过大，因而降低了密云水库的蓄水能力。在深入分析潮白河水文特征的基础上，并考虑新建３个水库对下游汉域洪峰流量的影响，提出了几个新的方案，每一个新的方案，每一个建议的方案都能显著提高密云水库的效益。