岩坝桥岩体外接触带破碎带蚀变岩型金矿地质特征及其相关问题探讨

岩坝桥岩体外接触带的破碎带蚀变岩型金矿，是近年来在湘西鹤-锑-砷-金矿带发现的新类型金矿，具有矿化厚度较大，品位较低，矿化较均匀的地质特点。它的发现进一步展示了本区元古宇及其中发育的剪切带的成矿潜力，具有一定的找矿现实意义。     

关于“大贵州滩”

在20世纪90年代,Lehrmann等把中国南方贵州省南部罗甸地区早三叠世的一个孤立的"罗甸碳酸盐岩台地",称作"大贵州滩"。在国外,已有300多篇文章引用"大贵州滩"这一术语。笔者等曾对中国南方早及中三叠世的岩相古地理进行过研究,根据我们的地质资料,在贵州省南部的罗甸地区,在早三叠世,只有一个孤立的"罗甸碳酸盐岩台地",没有"大贵州滩",也不能把"罗甸碳酸盐岩台地"称作"大贵州滩"。《古地理学报》(英文版)2015年第4卷第1期,刊登了冯增昭等的文章,There was no"Great Bank of Guizhou"in the Early Triassic in Guizhou Province,South China(中国南方贵州省早三叠世没有"大贵州滩")。本文是该英文文章的详细摘要,目的在于让国内的广大读者也知道:"大贵州滩"这一术语是严重的名不副实,不应继续使用。     

THE WATER RESOURCES IN THE EUPHRATES RIVER AND THE TIGRIS RIVER VALLEYS AND POLITICAL RELATION BETWEEN COUNTRIES CONCERNED

Ａｔｐｒｅｓｅｎｔ,ｔｈｅＭｉｄｄｌｅＥａｓｔｉｓａｒｅｇｉｏｎｏｖｅｒｗｈｉｃｈｍａｎｙｋｉｎｄｓｏｆｃｏｎｔｒａｄｉｃｔｉｏｎｓｅｘｉｓｔ.Ｉｔｉｓｏｂｖｉｏｕｓｔｈａｔｔｈｅｒｏｏｔｃａｕｓｅｌｉｅｓｉｎｉｔｓｉｍｐｏｒｔａｎｃｅｉｎｔｈｅｓｔｒａｔｅｇｉｃｇｅｏｇｒａｐｈｉｃａｌｐｏｓｉｔｉｏｎａｎｄｒｉｃｈｒｅｓｏｕｒｃｅｓｏｆｏｉｌａｎｄｎａｔｕｒａｌｇａｓ.Ｉｔｈａｓａｌｗａｙｓｂｅｅｎａｈｏｔｓｐｏｔｉｎｔｈｅｗｏｒｌｄ,ａｎｄｃｏｎｆｌｉｃｔｓｈａｖｅｏｃｃｕｒｒｅｄｔｈｅｒｅｃｏ…     

Regional geochemical baseline concentration of potentially toxic trace metals in the mineralized Lom Basin,East Cameroon: a tool for contamination assessment

The distribution of trace metals in active stream sediments from the mineralized Lom Basin has been evaluated. Fifty-five bottom sediments were collected and the mineralogical composition of six pulverized samples determined by XRD. The fine fraction (<?150 µm) was subjected to total digestion (HClO₄?+?HF?+?HCl) and analyzed for trace metals using a combination of ICP-MS and AAS analytical methods. Results show that the mineralogy of stream sediments is dominated by quartz (39–86%), phyllosilicates (0–45%) and feldspars (0–27%). Mean concentrations of the analyzed metals are low (e.g. As?=?99.40 µg/kg, Zn?=?573.24 µg/kg, V?=?963.14 µg/kg and Cr?=?763.93 µg/kg). Iron and Mn have significant average concentrations of 28.325 and 442 mg/kg, respectively. Background and threshold values of the trace metals were computed statistically to determine geochemical anomalies of geologic or anthropogenic origin, particularly mining activity. Factor analysis, applied on normalized data, identified three associations: Ni–Cr–V–Co–As–Se–pH, Cu–Zn–Hg–Pb–Cd–Sc and Fe–Mn. The first association is controlled by source geology and the neutral pH, the second by sulphide mineralization and the last by chemical weathering of ferromagnesian minerals. Spatial analysis reveals similar distribution trends for Co–Cr–V–Ni and Cu–Zn–Pb–Sc reflecting the lithology and sulphide mineralization in the basin. Relatively high levels of As were concordant with reported gold occurrences in the area while Fe and Mn distribution are consistent with their source from the Fe-bearing metamorphic rocks. These findings provide baseline geochemical values for common and parallel geological domains in the eastern region of Cameroon. Although this study shows that the stream sediments are not polluted, the evaluation of metal composition in environmental samples from abandoned and active mine sites for comparison and environmental health risk assessment is highly recommended.     

内蒙古呼伦湖沙丘带形成原因分析

近年来,内蒙古呼伦湖地区降水偏少、气温偏高,导致湖水水位下降。引起沙丘带的面积逐渐增加。文章基于新巴尔虎右旗30年气象资料变化,试分析呼伦湖沙丘带形成原因。并分析沙丘带发展趋势。     

Dominants and accumulation of rare earth elements in sediments derived from riparian and depressional marshes

The rare earth elements (REEs) in the sediments of the Xianghai wetlands were measured by inductively coupled plasma spectrometry. The REEs accumulation rates in two sedimentation cores derived from the riparian and depressional marshes were determined by ²¹⁰Pb method. The results showed that REEs concentrations in the Xianghai wetland sediments (∑REEs, 116 mg kg⁻¹) were lower than the corresponding values in Chinese soils (181 mg kg⁻¹) and river sediments (∑REEs, 158–191 mg kg⁻¹). Under alkaline conditions (with pH, 8.2–10.3), the light REEs were more enriched than the heavy REEs. Cerium is the predominant element, and accounts for 30–33% of the total REEs. REEs in the depressional marsh sediments were relatively high (∑REEs, 127 vs. 104 mg kg⁻¹), especially light REEs contents. A significantly positive correlation was found between the neighboring elements except Pr and Dy. The different types of vertical distribution of REEs between the riparian and the depressional marsh can partly result from long-term differing hydrological regimes. Generally, depressional marsh had accumulated much more REEs than riparian marsh (the mean accumulation rates of ∑REEs, 102.98 vs. 48.89 μg cm⁻² year⁻¹).     

Tidal Reduction Method Based on Temporal Tidal Time-Difference Variations

Abstract

Technical developments in the positioning and depth detection fields have allowed for vast improvements in sounding results, but the effects of tidal reduction (TR) yet merit improvement; today, TR is the main factor that limits bathymetry precision. It is crucial to determine tidal time difference (TTD) between tidal gauges to conduct effective TTD-based TR. The influence of temporal TTD variations is usually ignored, and the temporal observation window to determine TTD is generally freely selected. In this study, temporal TTD variations were analyzed under the tidal constituent merging theory. Daily and hourly TTDs were compared and utilized to reduce the TR error during time difference method operation. At-sea experiments were conducted to contrast the effects of daily versus hourly TTDs on TR; the results indicate that hourly TTD is more precise and thus better suited to TR.     

柴达木盆地风沙地貌区风况特征

利用自动气象观测仪所记录的1年风速数据,计算并分析了柴达木盆地风速、风向及输沙势等风况特征的时空变化。结果表明:该区风速最大值出现在春季,最小值出现在冬季,季节变化明显,且在空间上表现为自西北向东南递增的趋势;起沙风风向以NW、WNW为主,主风向和次风向的组合在空间分布上存在明显不同,风况与沙丘类型比较吻合;常年以稳定的西北气流为主,东南气流所占比重小,仅出现在夏季;柴达木盆地整体属于中风能环境,一年中风沙活动最强烈的季节为春季,风沙活动强度由西北向东南逐渐增强。     

不确定性条件下的下辽河平原地下水脆弱性评价及空间分布软区划

建立地下水脆弱性评价的DRASTICH模型,辨析各个参数的不确定性特征,采用随机模拟方法同时对随机性参数和模糊性参数模拟赋值。分别对模糊性参数和脆弱性指数统计值设立具有概率分布意义的置信水平和百分位,得到多重地下水脆弱性的指数区间,在此基础上,分别绘制地下水脆弱性的保守分布图和冒险分布图,并对研究区地下水脆弱性分布状况进行分析。结果表明：① 以模糊区间形式表示的地下水脆弱性评价结果,能反映多种不确定因素综合影响下的地下水脆弱性客观实际情况,可提供更多可靠性方面的信息;② 以软区划方式制作地下水脆弱性分布图,保留了不确定性客观存在的事实,可给予决策者更多参考信息和调整余地;③ 地下水脆弱性软区划分布图显示：保守分布的脆弱性程度总体要高于冒险分布,置信水平选择越高,冒险分布与保守分布的空间分布差异越接近,且与最大可能性分布情况越接近;④ 研究区地下水脆弱性分布具有明显的空间集聚现象,地下水高脆弱性区域主要集聚在下辽河平原中部和南部地区,低脆弱性区域一般分布在下辽河平原东、西两侧地区。     

泸溪县李家田铝土矿床地质特征及其控矿因素

李家田铝土矿床赋存于下二叠统梁山组,与下伏地层寒武系呈平行不整合接触,其直接底板为铁质粘土岩,顶板为铝土岩或栖霞灰岩。矿体呈层状,矿石质量较好,铝硅比5.6,含铝矿物以—水硬铝石为主。矿床属红土—沉积型。