Seasonal variations in sulfur isotopic composition of dissolved SO<Subscript>4</Subscript><Superscript>2−</Superscript> in the Aha Lake,Guiyang and their implications

The Aha Lake is a seasonal anoxic water system in the southwest of Guiyang City, Guizhou Province, China. Seasonal variations in SO42- concentrations and their isotopic compositions in lake water as well as in the tributaries were investigated in this study. The results showed that sulfate concentrations in river water range from 0.94 to 6.52 mmol/L and their δ34S values range from -14.9‰ and 0.9‰, while lake water has sulfate concentrations ranging from 1.91 to 2.79 mmol/L, and δ34S values from -9.8‰ to -5.9‰. It is suggested that coal mining drainage is the major source of SO42- in the Aha Lake. Rainfall, sewage discharge, sulfide oxidation and gypsum dissolution have made only limited contributions. Different depth-dependent distributions of dissolved SO42- and δ34S were de-veloped for both DB and LJK in summer and winter. Due to water overturn, δ34S values display homogenous vertical distributions in winter and spring. While in summer and autumn, significant positive shifts of δ34S were clearly ob-served in epilimnion and bottom strata as a result of water stratification. High δ34S values in epilimnion may result from the retention of rainwater during water stratification. Dissimilatory sulfate reduction by bacteria was thought to be responsible for the increase of δ34S value in hypolimnion.     

大兴安岭—小兴安岭地区中生代岩浆-构造-钼成矿地质事件序列的初步框架

兴蒙造山带是中国一条重要的成矿带.通过近几年的调查研究,以及大量人力、物力和资金投入,在该区发现了一批大、中型钼矿床,但是钼矿产出的区域地质背景还不是很清楚.对该区中生代A型花岗岩类、地质图分析以及钼矿的研究得知:(1)研究区印支期和燕山期是两个独立的造山旋回,印支期造山在220～200Ma左右结束,以区域上发育一套碱...     

Crustal structure of the Paleozoic Kunlun orogeny from an active-source seismic profile between Moba and Guide in East Tibet, China

We herein present a new seismic refraction/wide-angle reflection profile that crosses the Songpan–Ganzi terrane, the Animaqing suture zone and the eastern Kunlun mountains (comprised of the South Kunlun and Middle Kunlun blocks separated by the Middle Kunlun fault). The profile is 380 km long and extends from Moba to Guide in eastern Tibet. The crustal thickness is about 62 km under the Songpan–Ganzi terrane, 62–64 km under the South Kunlun, and 60 km under the Middle Kunlun block. The Songpan–Ganzi flysch seems to be present up to a depth of 15 km south of the Animaqing suture zone, and up to a depth of 10 km in the Middle Kunlun block, with thicknesses elsewhere that depend on assumptions about the likely lithologies. The profile exhibits clear lateral variations both in the upper and lower crust, which are indicative of different crustal blocks juxtaposed by the Kunlun fault system. Whether or not the Songpan–Ganzi flysch was originally deposited on oceanic crust, at the longitude of our profile (100°E) it is now underlain by continental crust, and the presence of continental crust beneath the Songpan–Ganzi terrane and of a continental arc under the South Kunlun block suggest Paleozoic continent–continent arc collision in the eastern Kunlun Mountains. Comparison of crustal velocity columns from all wide-angle seismic profiles across the eastern Kunlun mountains indicates a remarkable west-to-east change in the Moho topography across the Kunlun fault system (15–20 km Moho step at 95°E, but only 2–5 km along our profile at 100°E). Lower-crustal thickness of the Kunlun terranes is rather uniform, about 35 km, from 80°–95°E, which suggests that similar thrust-thickening processes have played a role where the Qaidam Basin abuts the Kunlun fault, but thins to 20–25 km at 100°E, east of the Qaidam Basin. The increased crustal thickness from 93° to 98°E compared to that at 100°E may be due to the differences in the thickness of the crust of the two plates before their collision, and/or largely achieved by thickening of the lower crust, perhaps indicating a crustal flow mechanism operating more strongly in the western region.     

http://www.sciencedirect.com/science/article/pii/S1674987111000569

A study of deep penetrating geochemistry-the surface exploration techniques for finding concealed mineral deposits-was carried out over the Spence porphyry copper deposit in Chile by Australian,Canadian and Chinese laboratories using selective weak leach methods and is briefly reviewed here.Erratic and weak copper anomalies were obtained above the Spence deposit,which is concealed below a thick piedmont gravel cover.In the literature,such patterns are common in most of the weak selective leach studies carried out over known buried deposits.During exploration in unknown area,such weak leach techniques lead to some success and many dry holes.In this paper,stronger selective leaching methods are developed for oxides and sulfides,which may be the stable end products transformed and accumulated by a mobile precursor phase carried upward through the overburden by gas or water through long spans of geological time.The data obtained by the methods developed in this paper produced more significant and consistent anomalous data than previous efforts.Consequently,the leach approaches described here may increase the effectiveness of deep penetrating geochemistry in exploration for concealed ore deposits.     

GIS-based rare events logistic regression for landslide-susceptibility mapping of Lianyungang,China

Landslides have had a huge effect on human life, the environment and local economic development, and therefore they need to be well understood. In this study, we presented an approach for the analysis and modeling of landslide data using rare events logistic regression and applied the approach to an area in Lianyungang, China. Digital orthophotomaps, digital elevation models of the region, geological maps and different GIS layers including settlement, road net and rivers were collected and applied in the analysis. Landslides were identified by monoscopic manual interpretation and validated during the field investigation. To validate the quality of mapping, the data from the study area were divided into a training set and validation set. The result map showed that 4.26% of the study area was identified as having very high susceptibility to landslides, whereas the others were classified as having very low susceptibility (47.2%), low susceptibility (22.21%), medium susceptibility (14.39%) and high susceptibility (11.93%). The quality of the landslide-susceptibility map produced in this paper was validated, and it can be used for planning protective and mitigation measures. The landslide-susceptibility map is a fundamental part of the Lianyungang city landslide risk assessment.     

喀斯特地区土地利用变化研究——以贵州省为例

分析贵州省1996-2008年土地利用变化情况,揭示土地利用变化差异状况及驱动因子.基于贵州省1996-2008年土地利用变更调查数据,利用土地利用结构信息熵和均衡度、土地利用类型年均变化幅度、年均变化率与相对变化率5个指数,分析土地利用变化情况.结果表明:(1)13年间,贵州省土地利用变化主要以耕地和林地的变化为主,土地利用结构变化表现出林地、园地、居民点及工矿用地、水域、交通用地明显增加,耕地、牧草地和未利用地减少.(2)贵州省土地利用结构信息熵和均衡度呈现"上升--下降--上升"的过程,总体呈增长趋势.(3)8类土地利用类型中,园地的区域变化差异较大,牧草地区域变化差异较小;贵州省西部地区的土地利用类型变化较东部地区显著.贵州省土地利用结构变化的主要驱动力是生态退耕政策的实施和经济社会的发展.     

基于区域密度函数的兰—西城市区域人口聚散研究

以兰州—西宁城市区域县级行政单元三普四普五普以及2009年人口数据为依托,运用探索性空间数据分析技术研究了兰州—西宁城市区域人口分布,发现该区域存在3个人口高密度中心。根据单中心密度函数与多中心密度函数拟合结果的比较,发现采用基于平方根负指数模型的多中心区域密度函数能够很好地阐述研究区域的人口集聚与扩散。研究发现,区域内存在两种人口集聚与扩散模式,兰州城区与西宁城区呈现出向心集聚的特征,而临夏市则为弱中心式扩散。     

Seasonal evolution of circulation and thermal structure in the Yellow Sea

In this paper, the authors used the Princeton Ocean Model (POM) to simulate the seasonal evolutions of circulation and thermal structure in the Yellow Sea. The simulated circulation showed that the Yellow Sea Warm Current (YSWC) was a compensation current of monsoon-driven current, and that in winter, the YSWC became stronger with depth, and could flow across the Bohai Strait in the north. Sensitivity and controlling tests led to the following conclusions, In winter, the direction of the Yellow Sea Coastal Current in the surface layer was controlled partly by tide instead of wind, In summer, a cyclonic horizontal gyre existed in the middle and eastern parts of the Yellow Sea below 10 m. The downwelling in upper layer and upwelling in lower layer were somehow similar to Hu et al. (1991) conceptual model. The calculated thermal structure showed an obvious northward extending YSWC tongue in winter, its position and coverage of the Yellow Sea Cold Water Mass in summer.