拉萨地块和羌塘地块多个二叠纪基性岩及一个古特提斯海山的初步古地磁结果:对模拟东冈瓦纳晚古生代裂解的暗示

Detachment of the sliver-like Cimmerian terrane from eastern Gondwana in the Early Permian triggered mafic volcanism in many parts of the rift zone. To understand this tectonic episode we have carried out paleomagnetic investigations on mafic volcanic for-mations that were erupted on key terranes that now form part of Tibet. Specifically, we will present data from sections near Lhasa City (central Lhasa block) and Tuotuohe (central Qiangtang Block) as well as near Gyanyima (Paleotethyan sea-mount) that was emplaced onto the floor of Palaeotethys during the Late Permian. Paleomagnetic plots from each location will be used for tectonic calculations. Our new data will be used to evaluate regional scale models con-cerned with how the Cimmerian terranes in southern and SE Asia (from Iran-Tibet-SW China-Myanmar- Thailand-Sumatra) formerly abutted eastern Gond-wana.     

Towards quantitative evaluation of gas injection using time‐lapse seismic data

Of particular concern in the monitoring of gas injection for the purposes of storage, disposal or improved oil recovery is the exact spatial distribution of the gas volumes in the subsurface. In principle this requirement is addressed by the use of 4D seismic data, although it is recognized that the seismic response still largely provides a qualitative estimate of moved subsurface fluids. Exact quantitative evaluation of fluid distributions and associated saturations remains a challenge to be solved. Here, an attempt has been made to produce mapped quantitative estimates of the gas volume injected into a clastic reservoir. Despite good results using three accurately repeated seismic surveys, time‐delay and amplitude attributes reveal fine‐scale differences though large‐scale agreement in the estimated fluid movement. These differences indicate disparities in the nature of the two attributes themselves, which can be explained by several possible causes. Of most impact are the effects of processing and migration, wave interference effects and noise from non‐repeatability of the seismic surveys. This subject highlights the need for a more careful consideration in 4D acquisition, amplitude processing and use of true amplitude preserving attributes in quantitative interpretation.     

沙尘天气下输沙率的野外观测与分析

2014年7月—2014年8月借助风速仪、微梯度集沙仪,通过野外监测系统获取的试验数据,对塔中地区2014年7月—2014年8月沙尘天气过程中贴地层输沙率进行分析,得出:0～85 mm高度内,随着风速的增大,35～85 mm无论是绝对的输沙量还是相对的输沙量都减少。0～85 mm高度内,各层输沙率最大值均出现在风速为8 m·s-1左右,波动较为显著;最小值出现在6.5 m·s-1左右,波动不明显;沙尘天气中,输沙率最大值出现在5～15 mm高度,最小值出现在35～85 mm高度。扬沙天气中,风速9.2 m·s-1时,输沙率最大值在0～5 mm处。沙尘暴天气,拐点风速为7.5 m·s-1,7.5 m·s-1时,输沙率增加不显著,7.5 m·s-1时,输沙率增加显著。通过微梯度集沙仪获得的上述试验数据是风沙工程设计的一个极重要工程参数,具有重要的实践意义。     

新疆沙漠地区地表宽波段比辐射率遥感估算

地表比辐射率是估算地表温度以及地表长波辐射的一个重要参数,为了解决遥感影像反演地表比辐射率在裸地的精度不足问题,本文在新疆沙漠地区利用2类数据：① 傅里叶变换热红外光谱仪（FTIR）数据,在2013年、2014年秋天沿2条穿越塔克拉玛干沙漠的沙漠公路测量得到25个点的地表比辐射率数据;② 与FTIR数据同时期的MODIS温度/比辐射率数据MOD11A1、MOD11B1和反射率数据MOD09GA以及反照率数据MCD3A3,利用这2类数据为数据源,估算新疆沙漠地表比辐射率。首先,重新估算了基于MODIS宽波段比辐射率（BroadBand Emissivity, BBE）方程的系数和基于GLASS（Global L And Surface Satellite）BBE方程的系数,由此获得了GLASS BBE和MODIS BBE的修正方程。其次,将修正前后的GLASS BBE与FTIR和MODIS BBE作对比,发现其精度显著提高：① 与FTIR数据对比,修正前后的GLASS BBE方程的决定系数R²值从0.42增加到0.95,均方根误差（RMSE）和偏差（Bias）分别减少了1和3个数量级;② 与MODIS BBE方程数据对比,修正前后的GLASS BBE的R²值从0.69增加到0.91,RMSE和Bias分别减少了1和2个数量级。因此,修正后的基于GLASS和MODIS的BBE方程,极大地提高了遥感影像对裸地尤其是沙漠地区地表比辐射率的反演精度。使用修正后的GLASS BBE方程反演出新疆3个沙漠地区的BBE分布特征。结果表明,塔克拉玛干沙漠由于土地类型较为单一,其BBE值主要为0.88~0.92,而古尔班通古特沙漠以及库姆塔格沙漠受到地形、植被等的影响,BBE值稍微偏高,分别为0.89~0.95和0.89~0.94,沙漠周边稀疏植被区及其边缘地区的值范围为0.95~1.00。本文基于GLASS和MODIS的适用于新疆沙漠的BBE方程,为陆面过程的研究与模拟提供了支持。     

First fossil evidence of Connaraceae R. Br. from Indian Cenozoic and its phytogeographical significance

Fossil leaflet impression described here as a new species Rourea miocaudata sp. nov., showing close resemblance with the modern leaflets of Rourea caudata Planch. (Connaraceae R. Br.), has been recorded from the lower part of the Siwalik sediments (Dafla Formation, middle–upper Miocene) exposed at the road-cutting section of Pinjoli area in West Kameng district, Arunachal Pradesh. The important morphological characters of the fossil are its narrow elliptic leaflet, cuneate base, long caudate apex, entire margin, eucamptodromous to brochidodromous secondary veins, presence of intersecondary veins, percurrent and reticulate tertiary veins and orthogonally reticulate quaternary veins. This is the first authentic record of the occurrence of leaflet comparable to R. caudata of Connaraceae from the Cenozoic sediments of India and abroad. At present R. caudata does not grow in India and is restricted only in southeast Asia especially in China and Myanmar. This taxon probably migrated to these southeast Asian regions after lower Siwalik sedimentation (middle–upper Miocene) due to climatic change caused by post-Miocene orogenic movement of the Himalaya. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period.     

Characterization of hydrogeologic properties of the Tabriz plain multilayer aquifer system,NW Iran

A detailed hydrogeological investigation was carried out in the Tabriz plain in Iran using conventional hydrogeological field investigations and hydrochemistry. The study was carried out because the aquifers are of particular importance as they are more or less the only source of water supply available to the rural population and for agricultural and industrial activities. Analytical and numerical methods were applied to the constant rate pumping test data from the Tabriz airport and the Tabriz Power Station well fields. Two types of aquifers of different water quality were identified in the study area: an unconfined aquifer that extends over the plain and confined aquifers that are found in the deeper layers of the multilayered sediment terraces of the Aji-Chay River course. Therefore, the central part of the Tabriz plain contains both unconfined and confined aquifers, while close to the highlands, there is only an unconfined aquifer. There was evidence of minor leakage in the confined aquifers when the numerical method was used for analysis. The groundwater in the area can be identified by three main geochemical facies: Na-Cl, Ca-HCO₃, and mixed Ca-Mg-Cl-SO₄. The processes responsible for the hydrochemical evolution in the area fall into five categories: dissolution of evaporate minerals, precipitation of carbonate minerals, evaporation, ion exchange, and anthropogenic activity.     

Geochemical characteristics of the Arabshah kaolin deposit,Takab geothermal field,NW Iran

The Arabshah kaolin deposit (Takab geothermal field, NW Iran) is the product of alteration of Miocene dioritic rocks. According to mineralogical data, the rock-forming minerals in this deposit include kaolinite, quartz, muscovite-illite, pyrophyllite, accompanied by lesser amounts of rutile, chlorite, anatase, albite, gypsum, nontronite, and pyrite. Consideration of elemental ratios and geochemical indices such as TiO₂, Nb + Cr, Ti + Fe, Sr + Ba, and La + Ce + Y demonstrated that both hypogene and supergene processes played a significant role in the development of this deposit. The mass change calculations revealed that elements like Zr, Ga, Hf, REEs, and Th which are normally immobile in ordinary alteration processes had both incremental and decremental trends during the development of this deposit. The Eu and Ce anomaly values (normalized to chondrite) in kaolinized samples vary within the range of 0.65–1.13 and 0.91–1.05, respectively. It seems that the variation of negative Eu anomaly values was controlled by kaolinization of feldspars by hypogene solutions and by scavenging of this element by Fe oxides and hydroxides (formed during oxidation of hypogene pyrite by supergene solutions). Variation of Ce anomalies also unravels the effective role of reducing hypogene fluids and to some extent of supergene solutions during kaolinization. Combination of the results obtained from mineralization considerations, mass change calculations of elements, and correlation coefficients illustrate that distribution and concentration of major, minor, and rare earth elements during kaolinization at Arabshah were affected by the function of factors such as changes in physico-chemical conditions of altering solutions (e.g., Eh and pH), adsorption, accessibility to complex-forming ligands, water-rock ratios, existing in resistant (to alteration) mineral phases, and scavenging by Fe and Mn oxides.     

Assessing the hydrogeochemistry and water quality of the Aji-Chay River,northwest of Iran

Aji-Chay River is one of the most important surface reservoirs of northwest of Iran, because it passes through Tabriz city and discharges to Urmia Lake, one of the largest permanent salty lakes in the world. The main objectives of the present study are to evaluate its overall water quality and to explore its hydrogeochemical characteristics, including the potential contamination from heavy metals and metalloids such as Co, Pb, Zn, Cd, Cu, Cr, Al and As. For this purpose, 12 water samples were collected from the main river body and its tributaries within Tabriz plain. The Piper diagram classified water samples mainly into Na–Cl and secondary into Ca–HCO₃ and mixed Ca–Mg–Cl types, denoting a profound salinization effect. The cross-plots showed that natural geochemical processes including dissolution of minerals (e.g., carbonates, evaporites and silicates), as well as ion exchange, are the predominant factors that contribute to fluvial hydrogeochemistry, while anthropogenic activities (industrial and agricultural) impose supplementary effects. Cluster analysis classified samples into two distinct clusters; samples of cluster B appear to have elevated electrical conductivity (EC) values and trace metals concentrations such as Co, Pb and Cd, while SiO₂ and Zn are low in comparison with the samples of the cluster A. The main processes controlling Aji-Chay River hydrogeochemistry and water quality were identified to be salinization and rock weathering. Both are related with geogenic sources which enrich river system with elevated values of Na⁺, Cl^?, Ca²⁺, Mg²⁺, K⁺, SO₄ ^2? and EC as a direct effect of evaporites leaching and elevated values of Pb and Cd as an impact from the weathering process of volcanic formations. According to the US salinity diagram, all of the water samples are unsuitable for irrigation as having moderate to bad quality.