光山凉亭-薄刀岭银金矿床地质地球化学特征

凉亭-薄刀岭银金矿床属构造蚀变岩型.矿体赋存于中元古界信阳群龟山岩组下段第一、二岩性层(Pt2gcd+di)白云石英片岩、碳质绢云石英片岩内,严格受EW向构造破碎带控制.矿化带原生晕表现为高背景值、强异常特征,As,Pb,Mo,Bi指示元素与成矿元素Ag,Au密切相关;成矿热液的运移以渗流为主、渗透为辅.本文通过对该矿床地质、地球化学特征的总结研究,建立了综合找矿标志,对区域同类型矿床的找矿评价具有一定的借鉴和指导作用.     

生物土壤结皮研究：进展、前沿与展望

生物土壤结皮是由隐花植物和相关土壤微小生物与表层土壤颗粒胶结而形成的复合体,与维管束植物覆盖一样,它是干旱区地表的重要覆盖类型(其盖度达40%)。生物土壤结皮是荒漠生态系统组成和地表景观的重要特征,在不同生物气候区的荒漠景观过程、土壤生态过程、土壤水文过程、土壤生物过程和地球化学循环过程,以及干旱半干旱地区生态修复过程中发挥着重要作用。关于生物土壤结皮的研究是地学和生物学学科交叉的前沿研究领域,已成为国际干旱区地表过程研究的重要核心科学问题之一。综述了国内外该领域最新研究进展,分析了研究的趋势,讨论了其前沿科学问题和未来研究的重点,以期促进我国生物土壤结皮的研究,加深对我国干旱半干旱区地表过程的认识。     

汶川地震震后大成都地区断裂带活动性氡气测量分析评价

本文运用活动断裂剖面上的土壤氡气浓度测量,对大成都地区断裂的位置、范围和活动性进行监测,监测结果表明汶川地震对大成都地区断裂带有较大的影响。通过对北川断裂虹口剖面、彭灌断裂小渔洞剖面、彭灌断裂中坝剖面、彭灌断裂白鹿剖面以及新津-蒲江断裂剖面进行监测,从测量结果分析可知:断裂剖面土壤氡浓度背景高于无断裂带地区,且受地震影响较大,距汶川地震震中越近,断裂剖面土壤氡浓度值越高;断裂剖面氡浓度异常阈值与背景值之比均不大于3,最大值与背景值之比均小于5。结合测量地点的地形、表层土壤结构等地质条件,对大成都地区震后活动断裂的相对活动性的强弱进行科学评价,认为目前大成都地区并无活动性极强的断裂,且北川断裂与新津-蒲江断裂的活动性高于彭灌断裂。     

吉林荒沟山金矿床地球化学找矿模型

以荒沟山金矿床的成矿地质特征为基础，研究了区域地球化学及异常特征，矿床地表及深部地球化学异常特征和原生异常元素分带性规律。初步总结出寻找该类型矿床的若干地球化学及异常指标，建立了地球化学找矿模型。     

Delineation and explanation of geochemical anomalies using fractal models in the Heqing area,Yunnan Province,China

The Heqing area, located in the Sanjiang ore belt, China, consists of the Beiya gold orefield related to the alkaline porphyry, the Emeishan volcanic mafic rocks and a series of sedimentary rocks. Thirty-nine elements of stream sediment samples taken in the 1:200,000 geochemical survey in the Heqing area can be classified into four groups using principal component analysis. Two fractal models, i.e., the concentration–area model and the number–size model, are applied in determination of the thresholds for the representative elements in the four groups. The thresholds obtained from the two models are similar. According to the thresholds, the element concentration distribution can be divided into 3 segments, each of them is mainly correlated to one type of rocks, including the alkaline porphyry related to gold-mineralized rocks, mafic rocks and sedimentary rocks. This paper reveals that the various geological events can be characterized by the different fractal models of element distribution.     

岳阳市环境地球化学影响及其综合防治

1:20万蒲圻幅化探水系沉积物测量,发现岳阳市东北区的F、As、Hg、Pb、Mo、U、Cu、Be、Sb等9种元素的过高或过低含量,有碍于人体健康,容易诱发相应的地球化学疾病;该环境中的B、Zn及Mo、Cu、As等5种元素,以及Cu/Mo比值的过高或过低,均有碍农业和林业的发展,会出现某些植物病虫害。因此,本文研究了该区的地球化学特征,划分出6个有碍人体健康、5个有碍农业与林业发展的综合预测区,并提出了防治措施与建议。     

A Review of the Methods and Controls of Soil Weathering Rates

The study of soil weathering processes College of Resources and Environment, rates and the associated influencing factors is crucial for understanding of the feedbacks between soil and environment, which will provide a basis for predicting soil behavior and evolution trend in the ecosystem under natural and anthropogenic forcings. This is also important for the effective management of soil resources. This article reviewed the methods for measuring soil weathering rates (including simulating leaching experiment, model calculation, isotope technique, element depletion and geochemical mass balance) and the influencing factors (including climate, organism, parent material, relief, time and human activities). In view of the serious degradation of soil resources, we proposed the challenge and opportunity of the research of soil weathering. The future study should focus on the critical processes, rates and the associated environmental thresholds of soil weathering under varying natural conditions and intensive human perturbations, including the establishment of the quantitative relationship between the weathering rates calculated by different methods, the analysis and interpretation of synergistic effects among multiple influencing factors, and the modeling and prediction of changing tendency of weathering rates under the impacts of both climatic changes and human activities, in order to guide the sustainable management of soil resource and mitigation of global change.     

郯庐断裂带南段两侧花岗岩地球化学特征:对大别造山带中-下地壳流动的限定

大别造山带形成于印支期华南、华北板块陆-陆碰撞过程中。大别造山带造山后发生了山根减薄,其可能的动力学机制为岩石圈拆沉或中-下地壳的塑性流动。为了检验大别造山带是否在造山后发生过中-下地壳流动,本次工作从对比郯庐断裂带南段两侧大别造山带及洪镇、月山地区花岗岩地球化学特征入手,对同样位于郯庐断裂带南段东侧的徐桥岩体开展地球化学研究,为大别造山带造山后是否经历过中-下地壳流动提供证据。本次工作对徐桥岩体的研究表明,该岩体侵位时间为127Ma左右;具有较高的Si O_2和全碱含量;明显富集Rb、Th、U、Pb等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE);稀土元素配分图解中表现为轻稀土富集和重稀土亏损的右倾配分模式,具有较弱的Eu负异常。徐桥岩体的地球化学特征与造山带东侧的月山岩体类似,且与下扬子地区沿江地区侵入岩基本一致。但同样位于造山带东侧的洪镇岩体,其地球化学特征与月山、徐桥岩体明显不同,而与大别造山带一致的地球化学特征,说明两者可能具有相似的源区。基于以上分析,笔者推断洪镇花岗岩的物质来源可能为大别造山带加厚的地壳。而大别造山带东侧出现造山带地壳物质的现象表明造山带在造山后发生过地壳的塑形流动。由于大别造山带中-下地壳物质穿过郯庐断裂带南段,表明郯庐断裂带造山后大规模左行平移事件应发生于大别造山带地壳流动变形之前。     

The variability of δ34S and sulfur speciation in sediments of the Sulejów dam reservoir (Central Poland)

The study was carried out on the Sulejów dam reservoir (Central Poland). Water and sediment samples were collected between February and October 2006. Sulfur compounds in the sediment were chemically extracted and subjected to isotopic analysis.Large variability of SO₄²⁻ concentration in the water column (from 10.3 to 36.2 mg/dm³) and the isotopic composition of sulfur (δ³⁴S from 2.1 to 5.4‰) was observed. The main identified sources of SO₄²⁻ were watercourses, surface runoff, and phosphorus fertilizers.Both oxidized sulfur species (SO₄²⁻) and its reduced forms were found in sediments. Particular sulfur forms were characterized by large variations in both, concentrations and the isotopic composition of sulfur. SO₄²⁻ in the sediment and in the water column had different genesis. Bacterial oxidation of organic sulfur and its binding in SO₄²⁻ were observed in the sediment. Under reducing conditions, oxidized and organic sulfur is converted to H₂S which reacted with Fe or other metallic ions leading to metal sulfide precipitation. Monosulfides were shown to have a very low concentration, ranging up to 0.07 mg/g of sediment. The transformation of elemental sulfur from sulfides through their chemical oxidation occurred in the sediment.