Mineralogy and geochemistry of lateritic soil profiles in Kerala, India

Lateritic soils near Calicut, Kerala, contain halloysite of intermediate hydration, kaolinite, goethite, gibbsite and quartz. The presence of halloysite is responsible for relatively high plasticity and cation-exchange capacity. Fe-hydroxide colloids along with halloysite contribute to significant phosphate uptake by this soil. Composition of local groundwater is consistent with weathering of sodic plagioclase to gibbsite, kaolinite and metastable halloysite.     

Relationships between geochemistry of basal till and chemistry of surface soil at forested sites in Finland

Concentrations of several elements extractable with BaCl₂ and acid ammonium acetate (pH 4.65) were measured in the organic and 4 mineral soil layers on the national forest inventory plots of the Finnish Forest Research Institute. The soil data also includes total concentrations of elements in the organic layer and site and soil physical characteristics. Data were compared with the aqua regia extractable element concentrations measured in the nationwide regional till geochemical mapping carried out by the Geological Survey of Finland.Correlations between concentrations in surface soil and underlying basal till were generally highest for K, Mg, Mn, P and Zn; in the organic layer and till they were highest for Cr and Cu. The strength of these correlations did not increase regularly from surface to deeper soil layers. All soil base cations with the exception of Ca, which is of relatively low solubility, were well correlated. The elements Zn, K, P, Al and Mn in till were the most reliable indicators of surface soil chemistry.Fuzzy clustering showed that the correlation between element concentrations in basal till and the two uppermost layers of mineral soil was better within areas of distinct till geochemistry, such as the schist belts in southwestern Finland, the Lake Ladoga–Bothnian Bay zone and the Kuusamo schist belt.Surface soil chemical variables were clearly better in discriminating fertility classes of forest sites than were element concentrations in basal till. The independent ability of till geochemistry to distinguish these productivity classes and to explain surface soil fertility was nevertheless demonstrated.     

Arsenic and presumed resistate trace element geochemistry of the Lincolnshire (UK) sedimentary ironstones,as revealed by a regional geochemical survey using soil,water and stream sediment sampling

A regional geochemical survey using soils, stream sediment and stream water sampling revealed multi-element geochemical anomalies, though of low environmental mobility, associated with Mesozoic sedimentary ironstones in Lincolnshire, UK. The most prominent of these anomalies were of As and V in soils and sediments, but elevated levels of elements such as Cr, La, Ce and Th were also observed. These were initially thought to be part of a residual resistate element or heavy-mineral suite, but careful examination suggests that these too may be primarily associated with the process of Fe oxide precipitation during the initial formation of the ironstones.     

四平地区不同母质黑土土壤地球化学研究

在吉林省四平地区黑土分布区选择3个具有不同成土母质特点的黑土样点进行土壤剖面样品进行测试。对所得数据进行对比分析表明, 不同采样点母质层土壤的地球化学元素含量具有显著差异: 表层黑土虽然对母质的地球化学性质有一定的继承性, 但在区域内相同的气候和植被等成土因素长时间的影响下, 土壤地球化学元素的含量发生了相应的变化, 不同母质条件下形成的黑土在地球化学性质上表现出一定的趋同性。     

Microheterogeneity of element distribution and sulfur speciation in an organic surface horizon of a forested Histosol as revealed by synchrotron-based X-ray spectromicroscopy

In recent years, the relevance of physico-chemical heterogeneity patterns in soils at the micron and submicron scale for the regulation of biogeochemical processes has become increasingly evident. For an organic surface soil horizon from a forested Histosol in Germany, microspatial patterns of element distribution (sulfur, phosphorus, aluminium, silicon) and S speciation were investigated by synchrotron-based X-ray spectromicroscopy. Microspatial patterns of S, P, Al and Si contents in the organic topsoil were assessed for a sample region of 50 μm × 30 μm by spatially resolving μ-XRF. Sulfur speciation at four microsites was investigated by focused X-ray absorption near edge structure (μ-XANES) spectroscopy at the S K-edge. The results show a heterogeneous distribution of the investigated elements on the (sub)micron scale, allowing the identification of diatoms, aluminosilicate mineral particles and sulfide minerals in the organic soil matrix. Evaluation of the S K-edge μ-XANES spectra acquired at four different microsites by linear combination fitting revealed a substantial microspatial heterogeneity of S speciation, characterized by the presence of distinct enrichment zones of inorganic sulfide and zones with dominant organic disulfide S within a few micrometers distance, and coexistence of different S species (e.g. reduced inorganic and organic S compounds) at a spatial scale below the resolution of the instrument (60 nm × 60 nm; X-ray penetration depth: 30 μm).     

Lunar geochemistry as told by lunar meteorites

About 36 lunar meteorites have been found in cold and hot deserts since the first one was found in 1979 in Antarctica. All are random samples ejected from unknown locations on the Moon by meteoroid impacts. Lithologically and compositionally there are three extreme types: (1) brecciated anorthosites with high Al₂O₃ (26–31%), low FeO (3–6%), and low incompatible elements (e.g., <1 μg/g Th), (2) basalts and brecciated basalts with high FeO (18–22%), moderately low Al₂O₃ (8–10%) and incompatible elements (0.4–2.1 μg/g Th), and (3) an impact-melt breccia of noritic composition (16% Al₂O₃, 11% FeO) with very high concentrations of incompatible elements (33 μg/g Th), a lithology that is identified as KREEP on the basis of its similarity to Apollo samples of that designation. Several meteorites are polymict breccias of intermediate composition because they contain both anorthosite and basalt. Despite the large range in compositions, a variety of compositional parameters together distinguish lunar meteorites from terrestrial materials. Compositional and petrographic data for lunar meteorites, when combined with mineralogical and compositional data obtained from orbiting spacecraft in the 1990s, suggest that Apollo samples identified with the magnesian (Mg-rich) suite of nonmare rocks (norite, troctolite, dunite, alkali anorthosite, and KREEP) are all products of a small, geochemically anomalous (noritic, high Th) region of crust known as the Procellarum KREEP Terrane and are not, as generally assumed, indigenous to the vast expanse of typical feldspathic crust known as the Feldspathic Highlands Terrane. Magnesian-suite rocks such as those of the Apollo collection do not occur as clasts in the feldspathic lunar meteorites. The misconception is a consequence of four historical factors: (1) the Moon has long been viewed as simply bimodal in geology, mare or highlands, (2) one of the last, large basin-forming bolides impacted in the Procellarum KREEP Terrane, dispersing Th-rich material, (3) although it was not known at the time, the Apollo missions all landed in or near the anomalous Procellarum KREEP Terrane and collected many Th-rich samples formed therein, and (4) the Apollo samples were interpreted and models for lunar crust formation developed without recognition of the anomaly because global data provided by orbiting missions and lunar meteorites were obtained only years later.     

Mercury as a pathfinder in exploration geochemistry — Case history studies

Mercury has long been regarded as a potential pathfinder for base and precious metals, and for mercury deposits per se. The earliest work was done in Russia (e.g. Saukov, 1946; Ozerova, 1962) and was followed up in North America, the UK and Australia. However, results were generally unsatisfactory. While the earlier data related to high-mercury systems, the methodology was adapted for sulphide deposits in general when it was recognized that these also carried mercury as a trace component. However, few case history studies have been published which demonstrate the usefulness of mercury in exploration geochemistry, especially in comparison to the more commonly analyzed target and indicator elements copper, lead, zinc, silver, gold and arsenic (Hawkes, 1982).     

Stabilisation of soil organic matter by interactions with minerals as revealed by mineral dissolution and oxidative degradation

Soil organic matter is known to contain a stable fraction with an old radiocarbon age. Size and stabilisation processes leading to the formation of this old soil carbon pool are still unclear. Our study aims to differentiate old organic matter from young and labile carbon compounds in two acid forest soils (dystric cambisol, haplic podzol). To identify such fractions soil samples were exposed to oxidation with Na₂S₂O₈ and to dissolution by hydrofluoric acid (HF). A negative correlation between ¹⁴C activity and carbon release after dissolution of the mineral matrix by HF indicates a strong association of stabilised carbon compounds with the mineral phase. A negative correlation between the ¹⁴C activity and the relative proportion of carbon resistant to oxidation by Na₂S₂O₈ shows that young carbon is removed preferentially by this treatment. The fraction remaining after oxidation represents a certain stabilised, long residence time carbon pool. This old fraction comprises between 1 and 30% of the total soil organic carbon in the surface horizons, but reaches up to 80% in the sub-surface horizons. Old OC is mainly stabilised by organo-mineral associations with clay minerals and/or iron oxides, whereas intercalation in clay minerals was not found to be important.     

Ion-microprobe zircon geochemistry as an indicator of mineral genesis during geochronological studies

This paper considers the distribution of trace elements (including rare earth elements) in zircons dated by the ion-microprobe U-Th-Pb isotope method and its genetic implications. Two problems were addressed on the basis of the investigation of trace element compositions of zircons: (1) genesis of zircons from subalkaline magmatic rocks, sysenites, and sanukitoids and their comparison with tonalites as exemplified by the rocks of the Karelian region, and (2) determination of trace element signatures of zircons from the oldest granulite-facies rocks of the Ukrainian shield. It was shown that the REE distribution patterns of the tonalites, which crystallized in equilibrium with melt, are strictly governed by crystal-chemical laws. The REE distribution patterns show a positive slope with an increase from La to Lu, a positive Ce anomaly, and a negative Eu anomaly. Similar patterns were observed in zircons from the syenites. The trace element contents of zircons are related to those of melts through partition coefficients. Zircons from the sanukitoids show a considerable LREE enrichment, which is inconsistent with the calculated zircon/melt partition coefficients and presumably related to the inherently imperfect zircon structure. Such a structure was formed during zircon crystallization from melt at high temperatures and the anomalous fluid regime that is characteristic, in particular, of sanukitoid melts. The REE distribution patterns of zircons that crystallized under granulite-facies conditions are sharply different from typical distributions in HREE depletion, which was caused by the competitive growth of garnet during zircon crystallization.     

Vulnerability profiles of forested landscape to climate change in Bengal Duars region,India

This paper assesses village level vulnerability profiles of the forested landscape in Bengal Duars region. Vulnerability of forested landscape is addressed by indicator-based approach with finer details using GIS-based interactive model under present climate. The three integrant of vulnerability are inscribed: exposure, sensitivity and adaptive capacity, by taking into consideration of twenty-one environmental and socio-economic indicators are identified. Being located in the foothills of Eastern Himalaya sudden variation of slope in Bengal Duars region results in frequent flooding and huge damage to forested landscape. Change of climate, degradation of forest resources and socio-economic backwardness further enhances the degree of vulnerability. It has been detected that 61% of area in Bengal Duars is configured to be vulnerable to climate change. The most vulnerable areas are the forested cover in Jalpaiguri, Baikunthapur, Wildlife-II, Wildlife-III, and Buxa Tiger Reserve East and their surrounding landscape with more climatic variation, disrupted by anthropogenic and non-climatic activities and less access to infrastructural and socioeconomic facilities.     

Groundwater contamination in parts of Nalgonda district,Telangana, India as revealed by trace elemental studies

The present paper deals with major and trace elements geochemistry of the groundwater from Nalgonda district, Telangana. The study area is very important in terms of anthropogenic activity like rapid industrial, urban development, pesticides, pharmaceutical, granite polishing and agro based industries. Inductively coupled plasma mass spectrometer (ICPMS) was employed to determine the concentration of trace elements in collected groundwater samples (bore well). These probe elements were further categorized as toxic elements (Pb, As, Cd, and V), alkaline earths (Sr and Ba), alkali metals (Li, Rb), transition metals (Cr, Mo and Ni), metallic elements (Cu, Fe, Zn, Al, Co), and other non-metallic elements (Se and Si). The groundwater quality was examined in perspective of Indian as well as World Health Organization drinking water standards. Based on the analytical results, groundwater in the study area is found to be slightly alkaline in nature and very hard, the average abundance of the major cations and anions is in the order of Ca⁺<Na⁺<Mg⁺<K⁺ and Cl^-<HCO₃ ^?<CO₃ ^?<SO₄ ^?<NO₃ ^?<F^– respectively. The dominant hydro chemical facies of groundwater is Na⁺ - HCO ₃ ^– – Cl^– and Na⁺ - Cl^– – HCO^– ₃ types.The results of trace elements shows that concentration of Pb, As, Cd, V in collected samples exceeding the desirable limits, and in the case of alkaline, alkali, transition, non-metallic elements, seventy per cent of the samples crossed the desirable limits, but all metallic elements viz. Cu, Fe, Zn, Al, Co is within the limits as per Indian as well as World Health Organizations drinking water standards. Factor analysis results shows that seven factors emerged as a significant contributor to the groundwater contamination is about 65.32 per cent. The spatial variation maps decipher trace elemental concentrations both geogenic and anthropogenic origin, by three zones i.e. ‘low’, ‘moderate’ and ‘high’ of the study area based on environment using Arc-GIS. High concentrations of trace elements are indicative of phenomenal rise in chemical composition and likely to have its origin from silicate weathering reactions and dissolution/precipitation processes supported by rainfall and anthropogenic activities, indiscriminate use of fertilizers/pesticides, and disposal of waste and sewage, release of reactive pollutants into the atmosphere by industries. Hence, this work is of immense societal benefit in terms of prevailing human health hazards in the study area with a direct relevance to such industrially populated regions elsewhere.     

Silicate and carbonate mineral weathering in soil profiles developed on Pleistocene glacial drift (Michigan, USA): Mass balances based on soil water geochemistry

Geochemistry of soil, soil water, and soil gas was characterized in representative soil profiles of three Michigan watersheds. Because of differences in source regions, parent materials in the Upper Peninsula of Michigan (the Tahquamenon watershed) contain only silicates, while those in the Lower Peninsula (the Cheboygan and the Huron watersheds) have significant mixtures of silicate and carbonate minerals. These differences in soil mineralogy and climate conditions permit us to examine controls on carbonate and silicate mineral weathering rates and to better define the importance of silicate versus carbonate dissolution in the early stage of soil-water cation acquisition.Soil waters of the Tahquamenon watershed are the most dilute; solutes reflect amphibole and plagioclase dissolution along with significant contributions from atmospheric precipitation sources. Soil waters in the Cheboygan and the Huron watersheds begin their evolution as relatively dilute solutions dominated by silicate weathering in shallow carbonate-free soil horizons. Here, silicate dissolution is rapid and reaction rates dominantly are controlled by mineral abundances. In the deeper soil horizons, silicate dissolution slows down and soil-water chemistry is dominated by calcite and dolomite weathering, where solutions reach equilibrium with carbonate minerals within the soil profile. Thus, carbonate weathering intensities are dominantly controlled by annual precipitation, temperature and soil pCO₂. Results of a conceptual model support these field observations, implying that dolomite and calcite are dissolving at a similar rate, and further dissolution of more soluble dolomite after calcite equilibrium produces higher dissolved inorganic carbon concentrations and a Mg²⁺/Ca²⁺ ratio of 0.4.Mass balance calculations show that overall, silicate minerals and atmospheric inputs generally contribute <10% of Ca²⁺ and Mg²⁺ in natural waters. Dolomite dissolution appears to be a major process, rivaling calcite dissolution as a control on divalent cation and inorganic carbon contents of soil waters. Furthermore, the fraction of Mg²⁺ derived from silicate mineral weathering is much smaller than most of the values previously estimated from riverine chemistry.     

Structural variations in derivatives of the bacteriochlorophylls of Chlorobiaceae: impact of stratigraphic resolution on depth profiles as revealed by methanolysis

Bacteriochlorophylls c and d, recovered from two sedimentary sequences, were converted to bacteriophaeophorbide methyl esters by methanolysis and analysed by atmospheric pressure chemical ionisation liquid chromatography-multistage mass spectrometry (APCI LC-MSⁿ). The distributions in both settings, a moderately consolidated sediment from Kirisjes Pond, Antarctica, and in a finely laminated microbial mat from Les Salines de la Trinitat, Spain, show significant variations within a narrow depth interval. The overall bacteriophaeophorbide c to d ratios in the two sediments are different, as are the ratios of particular C-3¹ diastereoisomers, indicating distinct differences between the bacterial communities that contributed to each sediment. Furthermore, a shift towards more extensive alkylation in homologues within each sediment is consistent either with changing environmental conditions in the depositional environments, or development-related changes in the structure of the bacterial community, leading to increased competition for light or nutrients.     

莺歌海盆地底辟带热流体突破的地层水化学证据

地层水化学特征往往反映出盆地流体的成因和演化信息。莺歌海盆地地层水样品分析表明地层水矿化度可划分3个带,即非底辟带、底辟带上方常压段和超压段。非底辟带地层水矿化度接近于正常海水,而超压带为具有较低矿化度的NaHCO_3型水,底辟带上方常压段地层水矿化度变化极大,与垂向断裂距离有关,越靠近垂向断裂的井往往具有更低的矿化度和更高的 HCO_3~-和 CO_3~(2-)离子浓度。在远离垂向断裂的底辟带侧翼或较浅地层(<1200m)孔隙水接近正常海水,以 MgCl_2型地层水为主:而在毗邻于垂向断裂的浅部储层具有明显低的矿化度,与超压带流体相似,也具有较高的 HCO_3~-和 CO_3~(2-)离子浓度这些观察结果反映垂向断裂为深部超压热流体突破的主通道,底辟带上方成为地层原生孔隙水(海水)与超压带内低矿化度热流体混合场所,地层水矿化度越低,说明来自深部超压热流体所占比例越大。不同压力地层中的水化学特征可以很好地用来识别流体运移路径和可能的水-岩反应。     

桂西北典型岩溶区水稻田成土剖面砷的垂向分布特征及其影响因素

调查分析桂西北典型岩溶矿区及其周边水稻田成土剖面砷含量及相关土壤参数垂向分布特征,研究了岩溶区土壤砷的含量垂向分布及迁移规律,并探讨了岩溶区土壤砷垂向迁移的主要影响因素。结果表明:研究区三个典型土壤剖面的主要土壤类型为石灰岩土,化学风化程度较高,土壤砷自然来源主要为土壤母质;土壤剖面砷含量的垂向分布均为表层相对富集、深层相对稳定,而土壤有机碳是制约岩溶区水稻田土壤砷垂向迁移的关键因素;矿区外围的两个土壤剖面砷含量主要富集在10～20 cm层,而在0～10 cm层砷含量相对较低,土壤砷含量平均值分别为5.5 mg·kg-1 和5.0 mg·kg-1 ;而临近矿区的土壤剖面具有土壤砷高背景值的特点,土壤砷含量平均值为46.2 mg·kg-1 ,且砷主要富集在20～40 cm的次表层,而在10~20 cm层砷含量则相对较低,但在0～10 cm层土壤砷含量又显著高于10～20 cm层,这表明外来源对该剖面表层土壤也具有显著影响。      

土壤(土被)中后生异常与深穿透地球化学

本文论述了土壤定义、土壤中同生组分和后生组分,重点论述了后生异常,特别是上置后生异常.提出深穿透化探技术设计原理是提取土壤中来自深部与矿化有关的后生组分,而尽可能不破坏或少破坏土壤基体(同生组分).用实例说明同生异常和后生异常特征,为什么常规化探(全量)难以在运积物覆盖区隐伏矿勘查中发挥作用的原因.从提取土壤后生异常角...     

Water movement within lac du bonnet batholith as revealed by detailed thermal studies of three closely-spaced boreholes

Successive temperature logs have been obtained over a period of two years in three closely-spaced boreholes in the Lac du Bonnet batholith of the Superior Province of the Canadian Shield. Two of the boreholes, of depth 450 m and 830 m, intersect a dipping fracture zone at 435–450 m. In both holes water is flowing from near the surface to the fracture zone at approximately 1.5–1.9·10⁻⁵ m³ s⁻¹, the flow being inferred from analysis of the temperature logs. Below 25 m, temperatures in these two holes are 0.22–0.28 K lower than those in the third, 145 m, hole.The temperature data have been combined with over 200 thermal conductivity measurements on core samples to produce heat flow values. In the deepest hole heat flow above the fracture zone is 16% higher than that below the zone. This indicates that water is flowing up the fracture zone. The flow rate is approximately 0.3 g s⁻¹ m⁻¹, and the flow has existed for thousands of years.Observation of thermal effects of water flow in massive, relatively unfractured plutons in a region having little topographic relief causes one to be concerned about the reliability of heat flow values measured in similar environments.The regional heat flow is taken to be 50 mW m⁻² after correction for glaciation effects. The average value of 24 determinations of radioactive heat generation in granitic core samples is 5.23 ± 1.11 μW m⁻³, which is more than three times higher than expected for such a heat flow in the Superior Province. This implies that the layer of high radioactive heat generation is thin, being not more than 4 km and probably about 1.3 km thick.     

Arsenic in soil and vegetation of a contaminated area

Plant and soil samples were collected from one uncontaminated and four contaminated sites (in the Dashkasan mining area western Iran). Total and water-soluble arsenic in the soil ranged from 7 to 795 and from 0.007 to 2.32 mg/kg, respectively. The highest arsenic concentration in soil was found at the ore dressing area (up to 1,180 mg/kg) and lowest at an uncontaminated area (up to 11 mg/kg). A total of 49 plant species belonging to 15 families were collected from four sampling sites. A significant positive correlation was detected between the concentrations of arsenic in plant dry matter and those in soils. The highest arsenic concentrations were found in Hyoscyamus kurdicus Bornm. (up to 205 mg/kg) and Helichrysum oligocephalum DC. (up to 162 mg/kg). These two accumulator species could have potential for soil clean-up by phytoextraction. The data have been compared with those for the Zarshuran mining area (north-western Iran) obtained in a former study.     

黑龙江兴凯湖平原土壤硒地球化学特征及富硒土地开发潜力

土地质量地球化学调查结果显示,兴凯湖平原土壤总体上属足硒土壤,富硒土壤面积不足1%。土壤硒的分布对成土母质具有较好的继承性,新近系富锦组（N1f）发育的土壤中Se平均含量最高,平均值为0.375 mg/kg,该地层控制了研究区富硒土壤的主要分布,而石炭系北兴组凝灰岩发育的土壤中Se含量最低,平均值为0.183 mg/kg。同时,土壤Se含量还受地球化学环境、土壤类型、土壤性质等自然条件综合影响,其中白浆土的Se含量最高,暗棕壤最低;硒与土壤中Corg、N、P、TFe2O3、S、As、Cr、Cu、Hg、Pb、Cd和Ni呈显著正相关,与pH、CaO、Na2O及Zn呈显著负相关。此外,研究区土地综合质量优良,5处潜在富硒区均符合AA级绿色食品产地,且发现天然富硒水稻,开发富硒农产品的潜力巨大。