Application of SEM-EBSD to regional scale shear zone analysis: A case study of the Bhavani Shear Zone,South India

The Bhavani Shear Zone (BSZ), part of the Palghat-Cauvery shear system of southern India, comprises a number of subparallel shear zones ranging in width from a few centimetres to tens of metres. These shear zones are characterised by progressive mylonitisation and shear fabrics corresponding to increasing strain, as documented by grain size reduction, flattening, elongation and dimensional preferred orientation of constituent minerals (quartz, hornblende, biotite, plagioclase and orthoclase). However, SEM-EBSD measured crystal preferred orientations (CPO) of these minerals are more complex and indicate interchange of maximum (X) and intermediate (Y) tectonic axes during different phases of deformation, with the minimum axis (Z) remaining approximately constant. The tectonic evolution of the BSZ and the disposition of the surrounding Archaean and Pan-African granulites are interpreted therefore in terms of polyphase deformation involving both dip-slip and strike-slip movement events in a multiply reactivated setting. SEM-EBSD CPO analysis provides clearer indication of potentially conflicting movement directions that are otherwise poorly constrained by shear markers and shear sense indicators.     

U-Pb age of detrital zircons from neoproterozoic placers of the Erementau-Niyaz massif as a reflection of stages of Precambrian tectono-magmatic evolution of northern Kazakhstan

A typical feature of the Precambrian complexes of the Kokshetau, Ishkeolmess, Erementau-Niyaz, and Aktau-Dzhungaria massifs of Northern and Central Kazakhstan is the presence of the end Mesoproterozoic-beginning of the Neoproterozoic quartzite-schist sequences in these sections. The lower and upper parts of these sequences are mostly composed of schists with interlayers of quartzites and marbles and of quartzitic sandstones, respectively. It is suggested that the quartzite-schist sequences represent the sub-platform cover of a large continental block and were formed in the regressive basin with widely abundant facies of submarine deltas and a littoral shoal. The presence of horizons and the lenses enriched in zircon-rutile heavy concentrate with the amount of accessory minerals of 10-70% characterizes the quartzite-schist sections of the Kokshetau and Erementau-Niyaz massifs. The U-Pb age of zircons from one such locality in the central part of the Erementau-Niyaz massif was analyzed by LA-ICP-MS. The Concordia ages of zircons are in the intervals 1041 ± 13-1519 ± 14, 1623 ± 14-1931 ± 14, and 2691 ± 14-2746 ± 14 Ma. One age was 2850 ± 14 Ma. The age distribution is characterized by clear peaks of 1.08, 1.20. 1.34, 1.46, 1.65, 1.89, and 2.70 Ga and weak peaks of 1.13 and 1.68 Ga. The age of the majority of zircons ranges from 1309 ± 14 to 1519 ± 14 Ma. Our data indicate that mostly Neoproterozoic rocks with a subordinate role of Paleoproterozoic and Neoarchean complexes served the feeding sources for the quartzite-schist sequence of the Erementau-Niyaz massif. The Mesoproterozoic and Paleoproterozoic events identified for the detrital zircons of the Erementau-Niyaz massif are completely manifested only in Laurentia. In the first approximation, these events coincide with the assembly and breakup of the Columbia/Nuna supercontinent (～1650–1580 and 1450–1380 Ma) and assembly of the Rodinia supercontinent (1300–900 Ma).     

东亚季风“2.8ka”事件高分辨率的石笋记录

据湖北省神农架永兴洞一支石笋的8个230Th年龄、648个δ18O数据,建立了晚全新世4.40～ 1.75ka B.P.时段平均分辨率为4a的东亚夏季风演化序列,其中在2.92～ 2.74ka B.P.期间,δ18O发生显著正偏,幅度达2.5‰,指示一个显著的弱季风事件(这里称之“2.8ka”事件).该事件以夏季风缓慢减弱开始,迅速增强结束,事件内部有两个次一级的振荡旋回(两峰三谷结构),在内部细节与转型特征上类似湖北和尚洞石笋δ18O记录的“8.2ka”事件,暗示发生在全新世这两个冷事件的驱动机制基本一致.这两个弱季风事件都发生在太阳活动明显减弱时期,并分别与北大西洋Bond 2和Bond 5冰漂碎屑事件同步,表明百年尺度的东亚季风环流的演化由太阳活动和北高纬气候共同驱动.     

气候变化对京津唐地区水资源及供需平衡的影响

根据大气环流模型(GCMs)输出的未来气候变化情景,结合历史资料的诊断分析,应用建立的流域水文模型及水资源利用综合评价模型,研究了气候变化对京津唐地区水资源数量和时空变化的影响。在地区未来经济发展及部门用水量预测的基础上,分析了气候变化对供水、需水和部门缺水的影响以及经济损失。     

Comparison of two alluvial aquifers shows the probable role of river sediments on the release of arsenic in the groundwater of district Vehari,Punjab, Pakistan

The study was done to assess the effect of the river Sutlej on arsenic (As) contamination. Sampling was done from the alluvial plain with increasing distance from the river Sutlej in district Vehari and compared with the study done in the proximity of River Sutlej. Sixty (60) groundwater samples mostly from shallow depths were collected and analyzed for As concentrations. Multivariate statistical tools (PCA and CA), saturation index, piper plots and Gibbs diagrams were used to detect evidence about the interrelationship and sources of As and other water quality variables responsible for groundwater contamination. Results revealed that As concentration ranged from below detection limit to 156 µg/L indicating that 50% samples exceeding the WHO guidelines (10 µg/L) and 17% exceeding the Pakistan National Environmental Quality Standards (NEQS) limits (50 µg/L) Sutlej. The piper plot revealed that water chemistry of the study area was Ca–HCO₃^?, Ca–Mg–Cl, type. Correlations between As and HCO₃^? (r²?=?0.433) was positive, while negative correlations were observed between As–Mn²⁺ and As–Fe²⁺ (r²?=???0.102), (r²?=?0.107) respectively. Geochemical signatures of the groundwater in the study area showed that the As could be released by oxidative dissolution to some extent and elevated evaporation in the arid environment of the study area under the stimulus of alkaline water and high pH (range 7.1–8.4). Although the concentrations are exceeding the WHO limit in 50% of the water samples but, are less than the previous study done in Mailsi near River Sutlej. Further, the concentrations decreased as the distance from the River increased which shows the probable role of sediments deposited by the River Sutlej.     

Silver–bearing minerals in the Xinhua hydrothermal vein-type Pb-Zn deposit,South China

Mineralogy and Petrology - Electron probe microanalysis (EPMA) results are reported for newly identified silver–bearing minerals from the Xinhua deposit, Yunkaidashan area, South China. The...     

岩石圈流变性与沉积盆地以辽西-辽北-松辽盆地区为例

岩石圈流变性取决于岩石圈的地热状态、物质组成和结构,并量化为岩石圈总强度。沉积盆地的沉降和抬升是地球最上层流变带形变的响应,岩石圈板块对构造应力的响应在很大程度上取决于岩石圈流变性在横向和纵向上的不均一性。辽西、辽北、松辽盆地区岩石圈流变性存在明显差异,因而岩石圈总强度明显不同,在晚中生代伸展过程中,变形方式、变形幅度不同,分别形成了断陷盆地、多断少坳型盆地和断坳型盆地。     

华北石炭——二叠纪煤系粘土岩夹矸中铝的氢氧化物矿物研究

华北石炭——二叠纪煤系太原组和山西组不同煤层粘土岩夹矸中,广泛含有一水软铝石、一水硬铝石和三水铝石。大多数一水铝石矿物呈薄纹层状、似层状及层状聚集于富岩质及富有有机质粘土岩夹矸条带中,有的呈细脉状沿炭质条带及粘土岩夹矸层理的节理裂隙分布,并与玉髓、方解石、高岭石或迪开石和铵云母细脉共生。铝的氢氧化物矿物可以作为成岩古温度和成岩阶段划分的标志矿物。最后还讨论了该矿物的成因。     

微波作用下化学助剂在细粉煤脱水中的应用研究

探讨了在微波加热条件下加入表面活性剂和溶剂油等有机溶剂对脱水效果的影响,力求找出其中的脱水规律。结果表明：微波脱水效果明显,同时,表面活性剂能够大大降低滤饼含湿量,而且非离子表面活性剂的效果比阳离子、阴离子好,柴油也能促进粉煤的脱水。     

矿物热释氡找矿在某地含铀砂岩中的试验研究

该文探讨了矿物热释氡的氡来源较多的原因是每(μm)~3次生含铀矿物或眇岩中有数量巨大的——m×10~n(n>4,m、n为自然数)个的铀离子或晶胞。本文并介绍了取自4210砂岩铀矿床的坑道、钻孔及其矿区内的河流、陡壁的271个样品矿物热释氡的特征:热释氡晕范围较矿体宽约几十米,在平面、剖面上都有热释氡晕存在,产状与矿体一致,与地层和冲刷面有一定交角。表明热释氧晕受层位、岩相、构造等多种因素控制。这些特点,对指导技矿和分析矿床成因,无疑是有意义的。