Applicability to Korean Marine Clay of the Mobilized Undrained Vane Shear Strength Using Correction Factors

The undrained shear strength normalized by the yield consolidation pressure, su/pc', is presented for four coastal sites: Busan/Gwangyang and Incheon/Gunsan, having the characteristics of high and low plasticity, respectively. The field vane shear strengths, su(FVT), were compared with unconfined compressive strength, qu/2 which has been used as a representative testing method in Korea. Many researchers have suggested that the undrained shear strength normalized by the yield consolidation pressure, su/pc', depends on Ip. However, the undrained shear strength normalized by the yield consolidation pressure, su/pc' is in the range of 0.25–0.35, independently of the plasticity index, Ip except for su/pc' using qu/2 values in the case of soils having a low plasticity, such as Incheon and Gunsan intermediate soils.

Bjerrum's correction factor has been commonly applied to evaluate mobilized undrained shear strength using the field vane test in Korea. However, the corrected undrained shear strengths using Bjerrum's correction factor, including Morris and Williams' method, were considerably underestimated for Korean marine clay when compared with the qu/2 values that have been used as the mobilized undrained shear strength for practical design in Korea.     

ArcGIS在北山高放废物处置库预选区地学数据管理中的应用

以甘肃北山高放废物处置预选区所积累的数据为基础,研究地学信息数据管理平台的建立,实现对各种空间数据及其他非空间数据统一管理与应用,并提出了基于ArcGIS产品的预选区数据管理与共享的解决方案。     

Magma mixing origin for the post-collisional adakitic monzogranite of the Triassic Yangba pluton, Northwestern margin of the South China block: geochemistry, Sr–Nd isotopic, zircon U–Pb dating and Hf isotopic evidences

Petrogenesis of high Mg# adakitic rocks in intracontinental settings is still a matter of debate. This paper reports major and trace element, whole-rock Sr–Nd isotope, zircon U–Pb and Hf isotope data for a suite of adakitic monzogranite and its mafic microgranular enclaves (MMEs) at Yangba in the northwestern margin of the South China Block. These geochemical data suggest that magma mixing between felsic adakitic magma derived from thickened lower continental crust and mafic magma derived from subcontinental lithospheric mantle (SCLM) may account for the origin of high Mg# adakitic rocks in the intracontinental setting. The host monzogranite and MMEs from the Yangba pluton have zircon U–Pb ages of 207 ± 2 and 208 ± 2 Ma, respectively. The MMEs show igneous textures and contain abundant acicular apatite that suggests quenching process. Their trace element and evolved Sr–Nd isotopic compositions [(⁸⁷Sr/⁸⁶Sr)_i = 0.707069–0.707138, and ε_Nd(t) = −6.5] indicate an origin from SCLM. Some zircon grains from the MMEs have positive ε_Hf(t) values of 2.3–8.2 with single-stage Hf model ages of 531–764 Ma. Thus, the MMEs would be derived from partial melts of the Neoproterozoic SCLM that formed during rift magmatism in response to breakup of supercontinent Rodinia, and experience subsequent fractional crystallization and magma mixing process. The host monzogranite exhibits typical geochemical characteristics of adakite, i.e., high La/Yb and Sr/Y ratios, low contents of Y (9.5–14.5 ppm) and Yb, no significant Eu anomalies (Eu/Eu* = 0.81–0.90), suggesting that garnet was stable in their source during partial melting. Its evolved Sr–Nd isotopic compositions [(⁸⁷Sr/⁸⁶Sr)_i = 0.7041–0.7061, and ε_Nd(t) = −3.1 to −4.3] and high contents of K₂O (3.22–3.84%) and Th (13.7–19.0 ppm) clearly indicate an origin from the continental crust. In addition, its high Mg# (51–55), Cr and Ni contents may result from mixing with the SCLM-derived mafic magma. Most of the zircon grains from the adakitic monzogranite show negative ε_Hf(t) values of −9.4 to −0.1 with two-stage Hf model ages of 1,043–1,517 Ma; some zircon grains display positive ε_Hf(t) of 0.1–3.9 with single-stage Hf ages of 704–856 Ma. These indicate that the source region of adakitic monzogranite contains the Neoproterozoic juvenile crust that has the positive ε_Hf(t) values in the Triassic. Thus, the high-Mg adakitic granites in the intracontinental setting would form by mixing between the crustal-derived adakitic magma and the SCLM-derived mafic magma. The mafic and adakitic magmas were generated coevally at Late Triassic, temporally consistent with the exhumation of deeply subducted continental crust in the northern margin of the South China Block. This bimodal magmatism postdates slab breakoff at mantle depths and therefore is suggested as a geodynamic response to lithospheric extension subsequent to the continental collision between the South China and North China Blocks.     

石英阴极发光在火成岩研究中的应用

阴极发光是一种研究火成岩石英显微生长结构的有效技术方法。文章以甲玛斑岩铜矿床中岩体样品分析为例,简要介绍了光学显微镜阴极发光(OM-CL)和扫描电镜阴极发光(SEM-CL)两种图片的特点,并综述了石英阴极发光在火成岩研究中的应用。阴极发光所显示出的火成岩石英中的生长形式和蚀变结构反映了岩浆的结晶历史。相对稳定的以蓝色阴极发光为主的斑晶区域主要与石英中Ti含量的变化有关,它反映了结晶作用的温度。由于在岩浆演化过程中,与铝、锂、钾、锗、硼、铁、磷相比,钛更加相容,因此随着岩浆分异程度的加深,火成岩中铝/钛逐渐升高。石英阴极发光不仅能显示岩浆早期及岩浆晚期的各种结构,如生长环带、重熔表面、溶蚀湾等,还反映了许多次生结构,如显微裂隙等。这些现象在光学显微镜下难以观察区分。晶体的显微结构提供了熔体来源和演化的重要信息。将石英结构和熔融包裹体与微量元素研究相结合反映了岩浆演化详细的PTt轨迹,它是富硅酸盐岩浆演化过程中物理-化学条件改变的敏感指示剂。     

Agricultural opportunity costs assessment based on planting suitability: a case study in a mountain county in southwest China

Payment for ecosystem services (PES) has become an increasingly popular means of ecosystem conservation. Opportunity cost is an important factor to increase the investment efficiency of PES projects. However, the distribution of opportunity cost is usually unclear in mountainous regions due to the obvious environment changes. In this study, we developed a framework to assess the distribution of agricultural opportunity costs in mountainous regions and applied this method to Baoxing County, a typical mountainous county in Sichuan Province of southwest China. Planting suitability of 17 crops was assessed based on agricultural statistics and natural conditions data within a GIS environment. Agricultural opportunity cost was quantified with a weighted summation of farmers’ willingness to cultivate and each crop’s opportunity cost. Finally, specific agricultural opportunity cost was obtained according to the spatial areas of the protection programs and land use status. The results showed that agricultural opportunity costs of PES in Baoxing County were estimated to be more than $30 million, with a mean of 400.85 $/ha. Agricultural opportunity costs in mountainous regions displayed some obvious spatial variation and areas with lower agricultural opportunity costs could be selected as priority areas for PES. Our findings revealed that the planting suitability evaluation can make agricultural opportunity costs mapping more reasonable. It will be helpful for the PES programs implementation in mountainous regions.     

Electrostatic waves with frequencies exceeding the gyrofrequency in the magnetosphere

Electrostatic waves with > _c in a plasma with temperature anisotropy and loss-cone are considered. An analytical asymptotic analysis is made for waves propagating nearly perpendicular to the magnetic field and having wave-length small compared with the Larmor radius. Numerical computations are done for carried out waves with arbitrary direction of propagation. The frequency range of instability, growth damping rates, and dispersion curves have been found. The results can be used for the interpretation of magnetospheric experiments.     

Spatial variability and correlation of environmental proxies during the past 18,000 years among multiple cores from Lake Pumoyum Co,Tibet, China

Multiple cores from Lake Pumoyum Co, southern Tibet, provide an improved understanding of the spatial distribution of lake sediments, and how well they represent the paleo-climate. Comparative study of these cores using AMS ¹⁴C dating and environmental proxies clarified their relationships with environmental changes. Our work focused on understanding the spatial similarities among cores covering different time scales, and evaluating variations in sedimentary processes across sites. The four studied cores demonstrate different sedimentation rates, but environmental proxies help synchronize the timing of environmental variations. Sediment variables such as total organic carbon (TOC), inorganic carbon (IC), and grain size in different cores correlate well and corroborate changing trends over the past 10,000 cal years. Differences in sedimentation rates and facies among core sites probably result largely from differences in water depth. The core from the deepest site displays the highest average sedimentation rates and the highest accumulation rates of TOC, but lowest content of IC. Two cores from somewhat shallower sites have plant residues in their lower sections and record similar variations in both the number of layers and their depositional ages. Our results do not indicate any significant variation in sedimentation pattern or its related factors among the three sites. A single core from the deepest site could adequately represent the total lake environment over the time span covered. But cores from somewhat shallower sites might reveal important shifts in the environment over a longer time period.     

城市生态足迹计算与分析——以广州为例

生态足迹是近年来较为流行的定量测度人类对自然利用程度的新方法。生态足迹分析可定量反映城市人类活动对自然生态环境产生的压力和影响程度,为城市生态系统研究提供了新的思路和研究方向。本文以广州市为案例,估算2000年广州市的生态足迹,并分析了1995～2000年间广州生态足迹动态变化过程。结果表明:2000年广州市生态足迹为2.5ha/人,当地生态承载力为0.2ha/人,生态足迹是生态承载力的12倍半;近5年间万元GDP生态足迹逐年下降,但人均生态足迹略有上升。这说明广州市总体上经济发展方式正逐步由粗放型转变为集约型,但今后仍需注重提高其资源利用效率,提倡节约型的生产和生活消费模式,减少其生态足迹,逐步迈向生态城市,实现城市的可持续发展。     

吉林省典型城市大气颗粒物主要排放源成分谱对比研究

为建立吉林省典型城市大气颗粒物排放源源成分谱数据库,保障源解析结果的准确性,采用X射线荧光光谱分析技术对典型城市大气颗粒物主要排放源（道路尘、扬尘、建筑尘、土壤风沙尘、燃煤锅炉尘）的无机化学组分进行分析。结果表明：吉林市、白城市、通化市和四平市4个城市排放源成分谱组分含量虽有不同,但主量成分均为地壳组分;SiO₂含量在土壤风沙尘中最高,道路尘中最低,Ca含量在建筑尘中最高。元素富集因子分析表明：人类活动对道路尘元素Pb的富集贡献较大,主要来自汽车尾气排放;扬尘元素Pb、Zn、As有较高富集,具有道路尘、燃煤锅炉尘特征;建筑尘元素Ca富集显著;土壤风沙尘受人类活动影响较小,主要为自然源贡献;燃煤锅炉尘中元素As富集因子＞60,属极强扰动。     

高放废物地质处置北山预选区芨芨槽岩块地质特征

芨芨槽岩块是高放废物地质处置北山预选区新场地段中有利候选岩块之一。以高精度卫片解译、野外踏勘、地表工程揭露和节理测量为主要手段,对此岩块的岩石、断裂、节理带和节理等地质特征进行了详细调查和研究。芨芨槽岩块的主岩岩石类型单一,为黑云母二长花岗岩;后期有煌斑岩脉和石英脉贯人。断裂以NE向为主,共7条;多数断裂分布于岩块东西两侧边界,而岩块内部只有2条断裂。节理带以NW向为主,长度大于1km的有8条。据统计,岩块中节理有4个优势组,各优势组的产状和间距分别服从正态和负指数分布,节理平均间距为1．2-1．6m。断裂对节理的影响范围小于100m。此项调查和研究为处置库选址、性能评价和设计提供了必要的基础资料。