美国罗德河流域地下水中铝形成动力学

In the Rhode River estuarine/watershed area, increased acidity of precipitation from atmospheric acidic deposition has deleterious effects on the freshwater ecosystems. One of the characteristics of an acidic watershed is the mobilization of aluminum from soils to aquatic environment. Increased concentrations of aluminum in surface waters are toxic to living organisms. Detection of long-term changes of acidity and elevated Al concentrations in surface and soil waters is a central issue. In this present paper, the dynamics ofAl speciation in the shallow ground waters from Rhode River watershed 110 (la) were investigated. This research provides a unique, regional analysis of important controls on the transport of Al speciation through the rural watershed of the Chesapeake Bay.     

珠江河口及近海水体中铜的水平和形态分布

对夏季(2002-07)和冬季(2003-01)航次中珠江河口及近海水域样品中金属铜的总含量以及总溶解态、颗粒态、游离态铜含量进行对比分析。结果发现,夏季铜的总浓度水平分布并非完全体现陆源性规律,而是随河口向外海递增。而在冬季,总铜浓度的空间变化呈现和夏季完全相反的趋势,即随河口向外海逐渐降低。说明研究水域中金属铜可能具有其他来源,同时在很大程度上受到夏季沿岸上升流的影响。但是,游离态铜的分布在冬季和夏季却呈现相同的趋势,即自河口向外海逐渐降低。说明铜的形态分布在更大程度上取决于水体的理化性质。     

黄陵断穹核部鳞片石墨矿地球化学特征与成因研究

黄陵断穹核部石墨矿是我国鳞片(晶质)石墨矿的主要产区,对该区石墨矿的研究具有重要理论和实际意义。该区已有石墨矿研究成果多侧重于矿床地质方面,对矿床成因分析缺乏地球化学支撑。为此,本文从地球化学层面查明石墨矿原岩类型,碳质富集岩相、变质作用和晶质石墨的形成,为矿床成因和成矿作用提供地球化学依据。通过系统采集区内主要石墨矿样品,进行主量元素、微量元素、稀土元素和同位素分析,根据矿床地球化学原理和分析方法,阐明石墨矿的物质来源,成矿元素集散行为和矿床形成机制。根据主量元素含量和组合,推断石墨的原岩为碳质粉砂质泥岩。微量元素的双重性指示石墨矿的物质有两个来源:中太古代野马洞岩组和中太古代东冲河片麻杂岩。独特的稀土元素配分型式说明物源转化为原岩时存在着强烈的地球化学反应。石墨矿的碳同位素组成支持碳质来自有机物的观点。     

A method to evaluate REE-HFSE mineralised provinces by value creation potential,and an example of application: Gardar REE-HFSE province,Greenland

The rare earth elements and high-field-strength elements (REE-HFSE) exploration sector conducts most evaluations at deposit and smaller scales. It is not evident how the sector performs a preceding exploration stage—rating and prioritising REE-HFSE mineralised provinces—to determine which provinces are prospective enough to warrant investment. Here we present an objective, repeatable, low-cost method to screen any REE-HFSE province, as a foundation for district-scale investigations or asset evaluations. It is original for REE-HFSE screening, and adapted from regional scale copper, cobalt and petroleum exploration, and CO₂ storage, screening methods. It is centred upon a mineralised province’s favourability for potential value creation, and to identify: (a) its main information gaps; (b) its weakest links; (c) its exploration maturity and remaining potential category; (d) how it compares against other REE-HFSE provinces; and (e) if further investigation is justified. This method incorporates geoscience, strategy, economic and socio-environmental factors in a way that is understandable and directly usable across stakeholder groups. The workflow is systematic, yet flexible enough to accommodate organisation-specific criteria, and usable for other commodities. It provides the platform to build a global REE-HFSE province map and database consistently across national boundaries and organisations. Categories for the extent of province exploration maturity and remaining mineral potential are proposed. We illustrate the applicability of these methods using the Gardar REE-HFSE Province (GRHP) of south Greenland. We conclude that it is a moderate size, frontier province that is currently of questionable favourability for value creation. To move GRHP into a positive favourability class, its current weak links need strengthening by research, government policy and industry stakeholders: evaluate the mineral system; integrate all information geospatially and place it in the public domain; help the region improve some community health and safety issues; convert some mineral resources into an Ore Reserves category; commence mining and sales production.     

Concurrent Determination of U‐Pb Age and REE Mass Fractions of Zircon by High Mass Resolution SIMS

A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate ²⁰⁶Pb/²³⁸U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties.     

与高岭石固相平衡的酸性天然地表水中铝形态分布的计算机模拟

基于热力学平衡计算,用计算机模拟研究了与高岭石固相平衡的酸性天然地表水中铝的形态分布,讨论了影响铝莆态分布的各种因素,同三水铝石固相平衡相比,与高岭石固相平衡的酸性天然地表水中,铝的形态分布与溶解硅酸的浓度密度相关,聚合态铝浓度较低,总溶解铝浓度明湿减小约２个数量级,模型被用于实际水样的分析,所得结果与实验值符合较好,最后用Ｍｏｎｔｅ Ｃａｒｌｏ模拟考察了由于平衡常数的选择而带来的不确定性。     

Spatial distribution and behavior of dissolved selenium speciation in the South China Sea and Malacca Straits during spring inter-monsoon period

Selenium(Se) has been recognized as a key trace element that is associated with growth of primary producers in oceans. During March and May 2018, surface water(67 samples) was collected and measured by HG-ICP-MS to investigate the distribution and behavior of selenite [Se(IV)], selenate [Se(VI)] and dissolved organic selenides(DOSe) concentrations in the Zhujiang River Estuary(ZRE), South China Sea(SCS) and Malacca Straits(MS). It showed that Se(IV)(0.14–3.44 nmol/L) was the dominant chemical species in the ZRE, related to intensive manufacture in the watershed; while the major species shifted to DOSe(0.05–0.79 nmol/L) in the MS, associated with the wide coverage of peatland and intensive agriculture activities in the Malaysian Peninsula. The SCS was identified as the northern and southern sections(NSCS and SSCS) based on the variations of surface circulation.The insignificant variation of Se(IV) in the NSCS and SSCS was obtained in March, potentially resulting from the high chemical activity and related preferential assimilation by phytoplankton communities. Contrastively, the lower DOSe concentrations in the SSCS likely resulted from higher primary production and utilization during March. During May, the concentration of Se(IV) remained low in the NSCS and SSCS, while DOSe concentrations increased notably in the SSCS, likely due to the impact of terrestrial inputs from surface current reversal and subsequent accumulation. On a global scale, DOSe is the dominant Se species in tropical oceans, while Se(IV) and Se(VI) are major fractions in high-latitude oceans, resulting from changes in predominated phytoplankton and related biological assimilation.     

南沙群岛海域沉积物稀土元素地球化学研究

应用电感耦合等离子质谱法测定了南沙群岛海域3个站位沉积物中的稀土元素(REE)和过渡金属元素的含量,讨论了沉积物中REE水平及深度分布的变化特征,以特征金属元素为指标对3个站位进行了沉积区划分,同时对REE与10种金属元素的相关性进行了研究。结果表明,3个站分别为近大陆架残留沉积区、大陆坡深海沉积区和碳酸盐沉积区,各站REE含量存在较大差别,但分布模式相似,均为轻稀土富集型和Eu负异常,每个站各层REE分布模式线几乎重合;3个站沉积物中REE都与Ti、Zr有很好的相关性,与其它金属元素不存在明显的相关性,表明3个站沉积物物源主要为陆源上地壳物质。结合测年资料,认为该海域3个站全新世以来沉积物物源变化很小,沉积环境稳定。     

基于水淘选分级的长江口及邻近海域表层沉积物中磷的形态分布和迁移转化

磷是一种重要的生源要素,在河口、边缘海的初级生产中发挥重要作用,了解沉积物中磷的形态分布和迁移转化有助于深入了解该区域生态系统动力学。于2013年3月在长江口及邻近海域采集了表层沉积物样品,利用水淘选方法对沉积物进行了分级,并采用化学连续提取法分析了未分级和分级沉积物样品中的6种磷形态含量:可交换态磷、活性有机磷、铁结合态磷、自生磷灰石磷、碎屑磷和难分解有机磷,讨论了该区域沉积物中磷的形态分布、选择性输运过程和迁移转化。沉积物中总磷含量在14.0~18.4 μmol/g,其中碎屑磷是其主要成分,占54.5%,其次是有机磷和难分解有机磷,分别占到15.1%和13.1%。不同粒级沉积物中磷形态含量不同,可交换态磷、活性有机磷、铁结合态磷、自生磷灰石磷和难分解有机磷随粒级增加含量逐渐降低,而碎屑磷主要集中在粗粒级（大于32 μm）沉积物中。基于各粒级磷形态的质量分布,发现小于32 μm粒级的沉积物中各磷形态含量从长江口向浙闽沿岸逐渐增加,向外海方向逐渐减小,而大于32 μm沉积物的变化趋势与此相反,体现了不同形态磷的选择性输运。随粒径增大,总有机碳对有机磷比值（TOC/Or-P）先降低后升高,在大粒级沉积物中,TOC/Or-P比值较高主要是因为陆源有机碳贡献较高,而在小粒级沉积物中,主要是由于有机磷的迁移和转化更为活跃,体现了细颗粒物中有机磷相对有机碳的优先分解。本研究表明,从分级的角度可以对河口、边缘海的磷循环有一个更全面的认识。     

Rare earth element characteristics of the carboniferous Huanglong Formation dolomites in eastern Sichuan Basin,southwest China: Implications for origins of dolomitizing and diagenetic fluids

Marine dolostones of Carboniferous Huanglong Formation constitute major gas reservoir rocks in eastern Sichuan Basin. However, the investigation with respect to sources of dolomitizing and diagenetic fluids is relatively underexplored. The current study attempts to investigate the REE characteristics of dolomites using seawater normalization standard, and therefore discusses the origins of dolomitizing and diagenetic fluids, on the basis of continuous 47.33-m-long core samples from the second member of Huanglong Formation (C₂h₂) in eastern Sichuan Basin. Low Th, Sc, and Hf concentrations (0.791 × 10⁻⁶, 4.751 × 10⁻⁶, and 0.214 × 10⁻⁶, respectively), random correlation between total REE concentration (ΣREE) and Fe or Mn abundance, and seawater-like Y/Ho ratios (mean value of 45.612) indicate that the carbonate samples are valid for REE analysis. Based on petrographic characteristics, four dolomite types are identified, including micritic-sized dolomite (type Dol-1), fine-to medium-sized dolomite (type Dol-2), medium-to coarse-sized dolomite (type Dol-3), and coarse-to giant-sized saddle dolomite (type Dol-4). Dol-1 dolomites, characterized by positive Ce anomaly (mean value of 6.398), light REE (LREE) enrichment, and heavy REE (HREE) depletion with mean LREE/HREE ratio of 12.657, show micritic calcite-like REE patterns, indicating seawater origin of their dolomitizing fluids. Dol-1 dolomites were formed in sabkha environment whereas the dolomitizing fluids originated from evaporative brine water due to their micritic crystal sizes and tight lithology. Dol-2 dolomites, particularly subtype Dol-2a barely developing vuggy porosity, also show micritic calcite-like REE patterns, suggesting their dolomitizing fluids were seawater or seawater-derived fluids. This inference is confirmed by low Fe and Mn concentrations, which range from 651 μg/g to 1018 μg/g (mean value of 863 μg/g) and 65 μg/g to 167 μg/g (mean value of 105 μg/g), respectively, whereas homogenization temperatures (T_h, mean value of 103 °C) indicate that Dol-2 dolomites were formed under burial environment. Dol-3 dolomites, in form of cements of Dol-2 dolomites, show similar REE patterns to their host minerals (i.e., Dol-2 dolomites), indicating their parent source was possibly derived from Dol-2 dolomites. Dol-3 dolomites have high Fe and Mn concentrations with mean values of 3346 μg/g (ranging from 2897 μg/g to 3856 μg/g) and 236 μg/g (ranging from 178 μg/g to 287 μg/g), respectively, indicating the involvement of meteoric water. Meanwhile, it confirms that the dissolution in Dol-2 dolomites was caused by meteoric water leaching. Positive Eu anomalies (mean value of 1.406) in Dol-4 dolomites, coupled with high homogenization temperatures (mean value of 314 °C), suggest that Dol-4 dolomites precipitated from hydrothermal fluids. High Fe and Mn concentrations (mean values of 2521 μg/g and 193 μg/g, respectively) in Dol-4 dolomites likely results from interactions of hydrothermal fluids with deep burial clastic rocks.