珠江水系沉积物重金属元素背景值估算及污染特征分析

估算水系沉积物的地球化学背景值和识别其异常对人为污染判别与环境风险评估非常重要。采集并分析了珠江58件水系沉积物样品,经分析检验,Al、Fe和Sc被选作参考元素,并对比了确定地球化学背景及识别异常值的方法。其中,基于最小截断二乘法的回归分析是定义地球化学背景的有效方法,它是一种对异常值不敏感的稳健统计方法,而基于局部富集因子的箱线图和回归诊断图更适用于识别异常值。珠江不同河段重金属污染存在差异,北江和河网区主要受As、Cd、Cu、Pb和Zn污染,东江主要受Cu、Cr和Ni污染,而西江几乎不存在重金属污染。水系沉积物的主要污染类型是点源污染,主要污染来源是采矿和电镀等相关的工业活动。     

云南腾冲全新世火山岩岩浆演化和岩石成因

腾冲火山岩区是我国全新世以来记载火山喷发的少数地区之一,该地区岩浆作用的性质与成因是揭示青藏高原东缘的现今侧向生长过程与深部作用的重要依据。本文对腾冲火山岩区的马鞍山、黑空山、打鹰山全新世火山岩开展了矿物化学和岩石地球化学研究,以期揭示岩石成因和深部动力学过程。腾冲全新世火山岩主体岩性为高钾钙碱性系列的玄武粗安岩和粗安岩。岩石的Ca O、Fe_2O_3~T、Ti O_2与Si O_2负相关,而K_2O与Si O_2正相关,表明岩浆演化过程中可能存在橄榄石、辉石和斜长石的分离结晶作用。岩石中存在酸性斜长石(更长石,An=28)大颗粒捕掳晶,其边部发育了基性斜长石(拉长石,An=65)增生边;在大颗粒石英捕掳晶的边部发育了辉石的反应边,这些结构表明在岩浆上升到地壳浅部时,曾受到了花岗岩围岩的混染,但岩石的Th/Nb值均小于1.16,表明地壳混染总体不显著。腾冲全新世火山岩大离子亲石元素富集、高场强元素相对亏损,高Th/U、低Ba/La,富集Sr-Nd同位素,其岩浆源区应为经历过洋壳沉积物交代后的富集地幔。腾冲火山岩属于大陆板内环境,是印度与亚洲大陆碰撞后岩浆作用的产物。火山岩是沿着腾冲盆地南北向展布,且熔岩分布面积有限。由于高原侧向生长过程中的区域性走滑断裂会引起局部的伸展,腾冲火山岩产出可能与富集岩石圈地幔的减压熔融有关。     

地下水砷污染研究进展

砷是一种毒性很强的致癌物质,地下水的砷污染严重破坏生态环境,危害人类健康,已成为近年来国内外学者研究的热点问题。本文针对地下水的砷污染问题进行综述,介绍了地下水砷污染研究现状,并简单介绍了地下水中砷的来源。另外,还针对地下水中砷的存在形态及其影响因素等方面作了详细介绍,对砷污染的预防控制和修复治理起到指导作用。     

塔里木板块东北部坡北岩体内橄榄辉长苏长岩岩石成因

坡北岩体位于塔里木板块东北部,由5个阶段的岩浆作用形成,其中,第二阶段岩浆作用形成的侵入体岩石类型单一,主要为橄榄辉长苏长岩,局部有零星的辉长苏长岩和斜长岩。岩石的SiO₂—FeO/MgO图解显示其化学组成为钙碱性系列,但单斜辉石的Al₂O₃—SiO₂及n（Si）—n（Al^Ⅳ）图解表明母岩浆为拉斑玄武质岩浆。岩浆演化方向与岩石化学系列的转化是同化混染作用的结果,侵入体遭受了长城系古硐井岩群1.38%～3.15%的混染。原生岩浆为MgO含量约7.31%的玄武质岩浆。岩石的TiO₂、Na₂O、K₂O、稀土元素、大离子亲石元素丰度均很低;除一件样品外,其余岩石的ε_Nd（t）值为+2.54～+2.81,这些特征表明岩浆源区属亏损型大陆岩石圈地幔。岩浆在结晶过程中处于物理化学条件相对稳定的近平衡状态,局部不平衡分离结晶形成堆晶结构和纹层状构造,岩浆结晶温度约为1070℃。由于岩浆源区熔融程度低,导致原生岩浆贫硫,且岩浆在演化过程中没有经历充分的分离结晶作用,这些因素使得橄榄辉长苏长岩侵入体不具备硫达到过饱和进而发生铜镍硫化物熔离成矿的潜力。     

Low-pressure evolution of arc magmas in thickened crust: The San Pedro–Linzor volcanic chain,Central Andes,Northern Chile

Magmatism at Andean Central Volcanic Zone (CVZ), or Central Andes, is strongly influenced by differentiation and assimilation at high pressures that occurred at lower levels of the thick continental crust. This is typically shown by high light to heavy rare earth element ratios (LREE/HREE) of the erupted lavas at this volcanic zone. Increase of these ratios with time is interpreted as a change to magma evolution in the presence of garnet during evolution of Central Andes. Such geochemical signals could be introduced into the magmas be high-pressure fractionation with garnet on the liquidus and/or assimilation from crustal rocks with a garnet-bearing residue. However, lavas erupted at San Pedro–Linzor volcanic chain show no evidence of garnet fractionation in their trace element patterns. This volcanic chain is located in the active volcanic arc, between 22°00^′S and 22°30^′S, over a continental crust ∼70 km thick. Sampled lavas show Sr/Y and Sm/Yb ratios <40 and <4.0, respectively, which is significantly lower than for most other lavas of recent volcanoes in the Central Andes. In addition, ⁸⁷Sr/⁸⁶Sr ratios from San Pedro–Linzor lava flows vary between 0.7063 and 0.7094. This is at the upper range, and even higher than those observed at other recent Central Andean volcanic rocks (<0.708). The area in which the San Pedro–Linzor volcanic chain is located is constituted by a felsic, Proterozoic upper crust, and a thin mafic lower crustal section (<25 km). Also, the NW–SE orientation of the volcanic chain is distinctive with respect to the N–S orientation of Central Andean volcanic front in northern Chile. We relate our geochemical observations to shallow crustal evolution of primitive magmas involving a high degree of assimilation of upper continental crust. We emphasize that low pressure AFC- (Assimilation Fractional Crystallization) type evolution of the San Pedro–Linzor volcanic chain reflects storage, fractionation, and contamination of mantle-derived magmas at the upper felsic crust (<40 km depth). The ascent of mantle-derived magmas to mid-crustal levels is related with the extensional regime that has existed in this zone of arc-front offset since Late-Miocene age, and the relatively thin portion of mafic lower crust observed below the volcanic chain.     

Electrokinetic remediation of metal contaminated glacial tills

This paper presents the results of an experimental investigation which studied the feasibility of using the electrokinetic process to remediate contaminated clays of glacial origin, otherwise known as glacial tills. An overview of the electrokinetic phenomena, as well as previously performed laboratory and field investigations, is first presented. The methodology of the electrokinetic experiments which were conducted to investigate the removal of metals from a glacial till is then described. A total of 16 experiments were conducted using glacial till samples obtained from a project site near Chicago. Sodium and calcium were used as the surrogate cationic metallic contaminants. These experiments demonstrated that ion transport during the electrokinetic process occurs due to both electro-osmosis and electromigration, but that due to electromigration is significantly higher than that due to electro-osmosis. Unlike other clays such as kaolinite, the glacial till used for this investigation possessed high buffering capacity because of its high carbonate content which prevented the acid front migration from the anode to the cathode during the electrokinetic process. The ion removal efficiency of the electrokinetic process was found to increase when: (1) the voltage gradient applied to the soil was increased, (2) the initial concentration of the contaminants was increased, and (3) the duration of the treatment process was increased. The ion removal efficiency was also greater for smaller ions which possess less ionic charge and when the ions existed independently in the soil as compared to when they coexisted. This investigation suggests that the electrokinetic process has significant potential for remediating glacial tills contaminated with metals. However, the properties of Na and Ca are not representative of contaminants, such as heavy metals, so further investigations are needed.     

柴达木北缘东段呼德生镁铁-超镁铁质岩体锆石U-Pb年代学、地球化学及成岩成矿分析

呼德生岩体位于柴北缘造山带欧龙布鲁克微陆块东南缘,侵位于古元古代金水口变质岩群中。该岩体从中心到边缘依次出现橄榄岩→辉石岩→辉长岩的岩相分带特征,岩石主要类型有纯橄岩、橄榄二辉岩和辉长岩,各岩石之间多为过渡接触关系,镍铜矿化主要赋存于辉石岩中。锆石LAICP-MS U-Pb年代学研究表明,岩体形成年龄为425.2±5.8Ma,为柴北缘晚志留世-晚泥盆世后造山伸展阶段岩浆作用的产物。岩石镁铁比值(m/f)为2.51~5.37,属于铁质系列基性-超基性岩。各类岩石富集轻稀土元素(LREE)和大离子亲石元素(Ba、Sr、Rb),而亏损高场强元素(Zr、Hf、Nb、Ta)。岩相学、矿物学及岩石地球化学研究表明岩浆在演化过程中发生了一定程度的结晶分异作用和同化混染作用。结合岩体形成年代及区域地质资料,呼德生岩体应形成于大陆边缘伸展阶段,原始岩浆在演化过程中经历了地幔流体的交代作用。通过对岩浆结晶分异程度及同化混染情况等方面的综合评价,认为呼德生岩体具有良好的铜镍硫化物矿床形成条件。     

Influences of wastewater discharges on the water quality of Mamasın dam watershed in Aksaray, Central Anatolian part of Turkey

Sustaining the human ecological benefits of surface water requires carefully planned strategies for reducing the cumulative risks posed by diverse human activities. Municipal governments in Aksaray City play a key role in developing solutions to surface water management and protection problems. The responsibility to provide drinking water and sewage works, regulate the use of private land, and protect public health provides the mandate and authority to take action. A large part of Aksaray City uses Mamasın dam water as its primary source for drinking water. Several point sources of contamination may result from direct wastewater discharges from Melendiz and Karasu rivers, which recharge the Mamasın dam watershed. Relevant studies were carried out for monitoring the eutrophication process, which usually occurs in the static water mass of the Mamasın dam lake. This process may be caused by the continual increase in nutrients and decrease of O₂ levels, causing anaerobic conditions. Stimulated algae growth in these water bodies consequently reduces water quality. Hydrochemical parameters were evaluated to estimate the types of pollution sources, the level of pollution, and its environmental impacts on the Mamasın dam drinking water reservoir.     

δ34S isotope values of dissolved sulfate (SO4 2−) as a tracer for battery acid (H2SO4) contamination in groundwater

The application of sulfur isotope (³⁴S) values of sulfate in groundwater provided the information necessary to evaluate the source, transport and fate of battery acid and associated contaminants at the Gulf Coast Recycling (GCR) facility. The chemical and isotopic composition of groundwater beneath the (GCR) property, a battery recycling facility in east Tampa, Florida, varies more than expected for an area of comparable size. Sulfate (SO₄^2–) values, for example, range from 1.2 to 11,500 mg/L and oxygen and hydrogen isotopes do not attenuate towards the weighted annual mean. Those samples that are high in sulfate generally have a low pH, which immediately indicates battery acid (H₂SO₄) contamination as a potential source for the sulfate. The low pH and high reactivity of the sulfuric acid groundwater cause the formation of hydrogeological microenvironments due to preferential dissolution of carbonate minerals, which in turn causes enhanced recharge and groundwater flow in certain areas; thus, the extreme scatter in the data set. Because of the difficult hydrogeology it is not straightforward to delineate the point-sources of contamination and up to five potential scenarios have to be evaluated: (1) seawater intrusion, (2) upwelling of high-sulfate groundwater, (3) local dissolution of gypsum, (4) an up-gradient contaminant source to the northeast of the GCR property and (5) battery acid contamination.     

Genesis of the Huangshannan high-Ni tenor magmatic sulfide deposit in the Eastern Tianshan,northwest China: Constraints from PGE geochemistry and Os–S isotopes

The Huangshannan magmatic Ni-Cu sulfide deposit is one of a group of Permian magmatic Ni-Cu deposits located in the southern Central Asian Orogenic belt in the Eastern Tianshan, northwest China. It is characterized by elevated Ni tenor (concentrations in recalculated 100% sulfide) in sulfide within ultramafic rocks (9–19 wt%), with values much higher than other deposits in the region. Sulfides of the Huangshannan deposit are composed of pentlandite, chalcopyrite, and pyrrhotite and the host rock is relatively fresh, indicating that the high-Ni tenor is a primary magmatic feature rather than formed by alteration processes. It is shown that sulfides with high-Ni tenor can be generated by sulfide-olivine equilibrium at an oxygen fugacity of QFM +0.5, for magmas containing 450 ppm Ni and 20% olivine. Ores with >10 wt% sulfur have relatively low PGE and Ni tenors compared to other ores, R factor (mass ratio of silicate to sulfide liquid) modeling of Ni indicates that they formed at moderate R values (150–600). Based on this constraint on R values, ores with <10 wt% sulfides in the Huangshannan deposit can be segregated from a similar parental magma with 0.05 ppb Os, 0.023 ppb Ir, and 0.5 ppb Pd at R values between 600 and 3000. This, coupled with the supra-cotectic proportions of sulfide liquid to cumulus silicates in the Huangshannan ores imply mechanical transport and deposition of sulfide liquid in a magma pathway or conduit, in which sulfides must have interacted with large volumes of silicate magma. Platinum and Pd depletion relative to other platinum group elements (PGEs) are observed in fresh and sulfide-rich samples (S > 4.5 wt%). As sulfide-rich samples are also depleted in Cu, and as interstitial sulfides in those samples are physically interconnected at a scale of several cms, the low Pt and Pd anomalies are attributed to solid Pt and Pd phases crystallization and retention with the monosulfide solid solution (MSS) and Cu-rich sulfide liquid percolation during MSS fractionation. This finding indicates that Pt anomalies in sulfide-rich rocks from magmatic Ni-Cu deposits in the Eastern Tianshan are the result of sulfide fractionation rather than a hydrothermal effect. ¹⁸⁷Os/¹⁸⁸Os_(278Ma) values of the lherzolite samples vary from 0.27 to 0.37 and γOs_(278Ma) values vary from 110 to 189, indicating significant magma interaction with crustal sulfides, rich in radiogenic Os. Well constrained γOs values and δ³⁴S values (−0.4 to 0.8‰) indicate that crustal contamination occurred at depth before the arrival of the magma in the Huangshannan chamber. Regionally, deposits with high-Ni tenor have not been reported other than the Huangshannan deposit; however, many intrusions with high-Ni contents in olivine are present in NW China, such as the Erhongwa, Poyi and Poshi intrusions. Those intrusions are capable of forming high-Ni tenor sulfides due to olivine-sulfide-silicate equilibrium and relative high-Ni content in parent magma, making them attractive exploration targets.