Quantitative identification and source apportionment of anthropogenic heavy metals in marine sediment of Hong Kong

Based on ten heavy metals collected twice annually at 59 sites from 1998 to 2004, enrichment factors (EFs), principal component analysis (PCA) and multivariate linear regression of absolute principal component scores (MLR-APCS) were used in identification and source apportionment of the anthropogenic heavy metals in marine sediment. EFs with Fe as a normalizer and local background as reference values was properly tested and suitable in Hong Kong, and Zn, Ni, Pb, Cu, Cd, Hg and Cr mainly originated from anthropogenic sources, while Al, Mn and Fe were derived from rocks weathering. Rotated PCA and GIS mapping further identified two types of anthropogenic sources and their impacted regions: (1) electronic industrial pollution, riparian runoff and vehicle exhaust impacted the entire Victoria Harbour, inner Tolo Harbour, Eastern Buffer, inner Deep Bay and Cheung Chau; and (2) discharges from textile factories and paint, influenced Tsuen Wan Bay and Kwun Tong typhoon shelter and Rambler Channel. In addition, MLR-APCS was successfully introduced to quantitatively determine the source contributions with uncertainties almost less than 8%: the first anthropogenic sources were responsible for 50.0, 45.1, 86.6, 78.9 and 87.5% of the Zn, Pb, Cu, Cd and Hg, respectively, whereas 49.9% of the Ni and 58.4% of the Cr came from the second anthropogenic sources.     

Structural identification of the C25 highly branched isoprenoid pentaene in the marine diatom Rhizosolenia setigera

2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-2,5E,9E,13-tetraene I possessing a C₂₅ highly branched isoprenoid skeleton has been isolated from the marine diatom Rhizosolenia setigera and identified by ¹H and ¹³C NMR spectroscopy.     

The distribution and origin of dimethyldibenzothiophenes in sediment extracts from the Liaohe Basin,East China

The distributions of dimethyldibenzothiophenes (DMDBTs), the relationship between DMDBTs and dimethylbiphenyls (DMBPs), and the applications of DMDBTs as maturity indicators in source rocks have been investigated in a set of 21 lacustrine shales from the Eocene Shahejie Formation (Well SG1) in the Western Depression, Liaohe Basin, China. All source rock samples are characterized by total organic carbon contents of 1.37–3.27% and Type II (with minor Type III) kerogen. They were deposited in suboxic and brackish lacustrine environments and have maturities ranging from immature to mid-mature. The 3,3′-DMBP isomer can potentially react to yield 4,6-DMDBT; 2,6-DMDBT and 2,8-DMDBT by incorporating sulfur into biphenyl, which may be supported by a strong positive correlation between the absolute concentration changes of 3,3′-DMBP and those of 4,6-DMDBT, 2,6-DMDBT plus 2,8-DMDBT. The relative abundance of DMDBT isomers may be explained by the sulfur radical mechanism and are also controlled by steric hindrance and thermodynamic stability. The 4,6-/(1,4- + 1,6)-DMDBT ratio shows no regular trend with increasing maturity at the low stage, and it should be used with caution as a maturity indicator for immature sediments. However, within the oil generation window, the relative concentration of 4,6-DMDBT progressively increases with increasing maturity, which can be explained by its higher thermodynamic stability relative to the 1,4-DMDBT isomer. The 4,6-/(1,4- + 1,6)-DMDBT ratio exhibits a linear increase with increasing thermal maturity of the sediments. Thus, this ratio can be applied as an effective maturity indicator for source rocks within oil generation window.     

Geochemical evidence (C,N and Pb isotopes) of recent anthropogenic impact in south‐central Chile from two environmentally distinct lake sediment records

In this paper, we compare the elemental and isotopic (C, N, Pb) geochemistry of lake sediments from two contrasted environments in south‐central Chile. The first lake, Laguna Chica de San Pedro (LCSP), is situated in the urbanised area of the Biobio Region (36°S). The second lake, Lago Puyehue (40° S), is located 400 km to the southeast of LCSP and within an Andean national park. Our aim is to identify environmental impacts associated with increasing industrial activities and land degradation during the last 150 a. In LCSP, shifts in C/N atomic ratios, δ¹³C and δ¹⁵N from 1915–1937 to the late 1980s are attributed to successive land degradation episodes in the lake watershed. Based on a Pb isotopic mixing model, we estimate that up to 20% of lead in LCSP sediments is supplied from urban atmospheric pollution. By contrast, human impact in the watershed of Lago Puyehue is very limited. We observe no change in organic geochemistry during the last 150 a and lead contamination remains lower than 5%, even during the last decades. Although contamination levels are much higher in LCSP than in Lago Puyehue, a peak in anthropogenic Pb is recorded during the same period (1974–1976) at both sites. This maximum contamination level is consistent with increased industrial activity in the vicinity of Concepción. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of hydrocarbon distributions in oils and sediment extracts by gas chromatography—high resolution mass spectrometry

The distributions of steroid and triterpenoid hydrocarbons in crude oils and sedimentary rock extracts can be routinely determined by the direct injection of the sample into a gas chromatograph coupled to a mass spectrometer (GC-MS). The mass spectrometer is operated at a resolution of about 2500 (10% valley), and only the ion intensities at selected accurate mass values, diagnostic of the structural types of interest, are monitored throughout the analysis. The distributions, so obtained, find application in the assessment of the source and thermal maturity of crude oil accumulations in the subsurface. This technique eliminates chromatographic separation steps and combines two analyses in one. Thus, more geological samples and reference mixtures may be analyzed in a given time.     

石油和沉积有机质中C3-、C4-烷基取代二苯并噻吩的鉴定

采用人工合成标准物质共注实验、与文献报道的保留指数对比并结合异构体的结构及性质的方法,对石油和沉积有机质中 C3-和 C4-烷基取代二苯并噻吩类含硫多环芳烃化合物进行了系统的鉴定。确定了常规色谱质谱（GC-MS）分析中,烷基取代二苯并噻吩异构体在 HP-5MS （5%-苯基甲基聚硅氧烷）色谱柱上的标准保留指数。确认了前人初步鉴定的部分三甲基二苯并噻吩异构体甲基取代基位置,初步比较了 C3-和 C4-烷基取代二苯并噻吩在不同成因石油和沉积有机质中的分布特征,初步探讨了 C3-和 C4-烷基取代二苯并噻吩潜在的地球化学意义。研究结果为今后进一步探索烷基取代二苯并噻吩系列在石油和沉积有机质中的地球化学意义奠定了可靠的基础。     

Stable carbon isotopic evidence for differences in the dietary origin of bone cholesterol, collagen and apatite: implications for their use in palaeodietary reconstruction

Rats were raised on a variety of isotopically controlled diets comprising 20% C₃, C₄ or marine protein and C₃ and/or C₄ non-protein or energy (i.e. sucrose, starch and oil) macronutrients. Compound specific stable carbon isotope (δ¹³C) analysis was performed on the cholesterol isolated from the diet (n=7 ) and bone (n=15 ) of these animals and the values compared with bulk δ¹³C measurements of bone collagen and apatite. The dietary signals reflected by these three bone biochemical components were investigated using linear regression analysis. δ¹³C values of bone cholesterol were shown to reflect whole diet δ¹³C values, collagen to reflect mainly dietary protein values and apatite to reflect whole diet values. Further correlations between dietary protein-to-energy spacings (Δ¹³C_prot-engy = δ¹³C_protein - δ¹³C_energy) and whole diet-to-bone component fractionations (Δ¹³C_bcomp-wdiet = δ¹³C_{bone component} - δ¹³C_{whole diet}) indicates that for hypothetical diets where protein δ¹³C values are equal to energy values, fractionations between whole diet and bone biochemical fractions are -3.3‰ for cholesterol, +5.4‰ for collagen and +9.5‰ for apatite. Moreover, the narrow range of variation observed in apatite-to-cholesterol spacings (Δ¹³C_apat-bchol) suggests that cholesterol δ¹³C values can potentially also be used as an independent test for the isotopic integrity of apatite δ¹³C values. These insights into bone cholesterol, collagen and apatite dietary signals, diet-to-bone fractionations and bone component-to-bone component spacings provide the basis for more accurate interpretations of the dietary behaviour of archaeological populations and food webs when the δ¹³C analysis of bone is employed.     

The age of young intrusions of Tsana Complex (Greater Caucasus) and isotope-geochemical evidence for their origin from hybrid magmas

This paper presents isotope-geochronological and petrological study of granitoids of the potentially ore-bearing (Au–As–Sb–Sn–Mo) Early Pliocene Tsana Complex, which are confined to the Main Caucasus fault zone (upthrow fault) in the central part of the Greater Caucasus Range. The Tsurungal and Karobi groups of magmatic bodies are distinguished based on spatial criterion. The Tsurungal group includes three small granite—granodiorite massifs (Tsurungal, Chorokhi, and Toteldash) and numerous acid and intermediate dikes in the upper reaches of the Tskhenistsqali River (Kvemo Svaneti, Georgia). The Karobi group comprises three subvolcanic rhyodacite bodies located in the upper reaches of the Chashuri River (Zemo Racha, Georgia) and numerous N–S-trending trachyandesite dikes near the axial zone of the Main Caucasus Range. The K-Ar and Rb-Sr isotope dating shows that the granitoid massifs and dike bodies of the Tsana Complex were formed in two different-age pulses of the Pliocene magmatism: phase I at 4.80 ± 0.15 and phase II at 4.15 ± 0.10 Ma. All hypabyssal rocks of the Karobi group, unlike those of the Tsurungal Group, were formed during the first pulse. Petrographic studies in combination with geochemical data indicate that most of the granitoids of the Tsana Complex are hybrid rocks (I-type post-collisional granites) and were derived through mixing of deep-seated mantle magmas with acid melts obtained by the upper crustal anatectic melting in the Main Caucasus fault zone. The granitoids of the Tsurungal Group define basic to acid evolution (diorite–granodiorite–granite–two-mica granite) possibly caused by both crystallization differentiation and increasing role of crustal contamination in the petrogenesis of the parental magmas of these rocks. This conclusion is also confirmed by the differences in the Sr isotope composition between granitoids of the early (⁸⁷Sr/⁸⁶Sr = 0.7053) and late (⁸⁷Sr/⁸⁶Sr = 0.7071) phases of the Tsana Complex. Main trends in spatiotemporal migration of magmatic activity in the central part of the Greater Caucasus in the Pliocene–Quaternary time were established using obtained and earlier published isotope-geochronological data.     

Pull-apart formation mechanism of Cenozoic basins in the Tien Shan and their transpressional evolution: Structural and experimental evidence

The geodynamic settings of the evolution of Cenozoic basins in the North and Middle Tien Shan and their Paleozoic framework have been estimated from a kinematic analysis and detailed structural geological mapping of key sites. Two stages of their development in different geomechanical settings are distinguished. It is suggested that in the late Oligocene, Miocene, and early Pliocene, the pull-apart basins developed under the setting of simple left-lateral shear or transtension. Presumably in the late Pliocene and Quaternary, this setting gave way to right-lateral transpression; extension in the basins was changed by compression with the formation of local fold-thrust structural elements. The reconstruction of geomechanical sections was tested by analog tectonophysical simulation. The natural and experimental structural assemblies and patterns reveal satisfactory convergence.     

Copper, lead and cadmium concentrations in surface water, sediment and fish, C. Carpio, samples from Lake Naivasha: effect of recent anthropogenic activities

Following recent concerns of chemical pollution around Lake Naivasha, especially originating from recent agricultural activities in the catchment, samples of water, sediments, and fish Common carp (Cyprinus carpio) were collected from the Hippo Point, Kasarani, Mouth of Malewa River, Mouth of Karati River, Crescent Island, Sher Karuturi Discharge outlet and Oserian Bay for analysis of Cu, Cd and Pb by FAAS. The mean heavy metal levels ranged from 5.12?C58.11 (Pb), 1.06?C1.73 (Cd), and <0.03?C2.29 (Cu) mg/kg wet weight in C. carpio muscle, <100?C179.83 (Pb), <10.00?C10.06 (Cd) and <30.00?C32.33 (Cu) ??g/L in surface water, and 17.11?C53.07 (Pb), 1.18?C5.58 (Cd) and 3.00?C8.48 (Cu) mg/kg dry weight in sediment and showed a wide variation within and between samples with relatively high concentrations in sediments and fish muscle tissues. The results indicate that Lake Naivasha, in some parts, is polluted with these heavy metals of which relatively higher concentrations are found at the discharge outlets near Sher Karuturi and Oserian Bay. This indicates possible contribution from surrounding horticultural/floricultural activities and the Mouths of the Rivers Malewa and Karati which flow from it??s upper catchment.     

Large variations of δ13C values in stalagmites from southeastern China during historical times: implications for anthropogenic deforestation

Variations in speleothem δ¹³C values can reflect changes in overlying surface vegetation, which, over historical time scales, may represent the influence of human activities. Here, we examined δ¹³C variations in two stalagmites growing for the last 2200 years in Shennong Cave, Jiangxi Province, SE China. The two δ¹³C records corroborate well one another and show a prominent 6‰ enrichment of the δ¹³C values from AD 700 to 1100. The isotopic equilibrium for modern calcite and negative correlation between δ¹⁸O and δ¹³C values along the growth axis suggest that the influences of kinetic fractionation are negligible. Varied correlations between Mg/Ca and Sr/Ca ratios and divergent changes between δ¹³C values and Mg/Ca and Sr/Ca ratios from AD 700 to 1100 reveal that the prior calcite precipitation (PCP) and water–rock interaction did not dominate the increase of δ¹³C values. It is plausible that the obvious δ¹³C variation was largely influenced by the changes in vegetation cover overlying the cave. Our δ¹³C results, together with the records of climate and human activity from historical documentary records, suggest that: (i) prior to AD 700, small fluctuations in relatively light δ¹³C values reflect the presence of lush forest coverage above the cave, which was minimally disturbed by human activities; (ii) during AD 700–1100, the drastic increase in δ¹³C values indicates persistent and massive deforestation associated with large‐scale immigration into northern Jiangxi after the Rebellion of An & Shi (AD 755–763) in the Tang Dynasty and the subsequent development of agriculture and economic activity; and (iii) since AD 1100, fluctuations in relatively high δ¹³C values suggest that local vegetation during the last millennium has been sparse. Since the Rebellion of An & Shi, southeastern China was progressively developed, coincident with deforestation and vegetation deterioration caused by human disturbance in the form of deforestation and cultivation.     

Hydrogen,oxygen and carbon isotopic evidence for the origin of rodingites in serpentinized ultramafic rocks

$\text{D}\text{H}$, ${}^{18}\text{O}{}^{16}\text{O}$ and ${}^{13}\text{C}{}^{12}\text{C}$ analyses were made of 14 whole rock and 28 mineral samples of rodingites associated dominantly with lizardite-chrysotile serpentinites from the West Coast of the U.S.A., New Zealand, and the Northern Appalachian Mtns. The δD values of the rodingite minerals are in three groupings: 5 monomineralic veins of pectolite, ?281 to ?429; 8 monomineralic veins of xonotlite, ?112 to ?135; all other minerals, including hydrogarnet, idocrase, prehnite, actinolite, nephrite, and chlorite, ?34 to ?80. Most calcites in rodingites have δ¹⁸O (+9.3 to +14.4) and (δ¹³C (?6.7 to +0.9) values similar to calcites in other Franciscan rocks, but distinct from the very low temperature calcite veins in serpentinites. The $\text{D}\text{H}$ data, combined with δ¹⁸O values of xonotlite (+5.7 to +10.9) and pectolite (+8.9 to +12.4) suggest formation from meteoric-type waters at low temperatures; the $\text{D}\text{H}$ depletion of pectolite, however, is anomalous. Rodingite whole rock values range from δ¹⁸O = +4.1 to +11.5 and δD = ?50 to ?86; one sample containing minor amounts of lizardite-chrysotile serpentinite has δD = ?92, outside this range. However, most rodingites of basaltic or gabbroic parentage are more restricted in δ¹⁸O (+4.1 to +8.6). Such a wide range in δ¹⁸O is consistent with the idea that most rodingites form over a relatively broad range of hydrothermal temperatures. Hydrogen isotopic data for most rodingite minerals (except xonotlite and pectolite) and for whole rocks are suggestive of non-meteoric waters. These $\text{D}\text{H}$ data overlap those observed for veins of hydrous minerals found in Franciscan igneous rocks studied by Margaritz and Taylor (1976, Geochim. Cosmochim. Acta40, 215–234), possibly suggesting evolved D-enriched, connate type metamorphic waters generated during high P, low T Franciscan-type metamorphism at temperatures (250–500°C) comparable to estimates based on mineral stabilities. Such an interpretation is supported by the ${}^{18}\text{O}{}^{16}\text{O}$ and ${}^{13}\text{C}{}^{12}\text{C}$ data for calcite in rodingites.The isotope data appear to contradict some of the conclusions derived from geologic and petrologic studies that indicate concomitant metasomatism and serpentinization of their presently observed host rock. These data appear most consistent with the interpretation that most rodingite minerals, with the exception of late-stage veins of xonotlite and possibly pectolite, may involve metasomatism in association with antigorite serpentinization of ultramafic rock. Subsequent upward tectonic transport in many instances may result in incorporation of the rodingites into their presently observed lizarditechrysotile host rock during or subsequent to pervasive shallow level serpentinization by meteoric waters.     

Carbon and hydrogen isotopic evidence for the origin of combustible gases in water-supply wells in north-central Pennsylvania

The origin of the combustible gases in groundwater from glacial-outwash and fractured-bedrock aquifers was investigated in northern Tioga County, Pennsylvania. Thermogenic methane (CH₄) and ethane (C₂H₆) and microbial CH₄ were found. Microbial CH₄ is from natural in situ processes in the shale bedrock and occurs chiefly in the bedrock aquifer. The δ¹³C values of CH₄ and C₂H₆ for the majority of thermogenic gases from water wells either matched or were between values for the samples of non-native storage-field gas from injection wells and the samples of gas from storage-field observation wells. Traces of C₂H₆ with microbial CH₄ and a range of C and H isotopic compositions of CH₄ indicate gases of different origins are mixing in sub-surface pathways; gas mixtures are present in groundwater. Pathways for gas migration and a specific source of the gases were not identified. Processes responsible for the presence of microbial gases in groundwater could be elucidated with further geochemical study.     

Carbon and hydrogen isotopic evidence for the origin of combustible gases in water-supply wells in north-central Pennsylvania

The origin of the combustible gases in groundwater from glacial-outwash and fractured-bedrock aquifers was investigated in northern Tioga County, Pennsylvania. Thermogenic methane (CH₄) and ethane (C₂H₆) and microbial CH₄ were found. Microbial CH₄ is from natural in situ processes in the shale bedrock and occurs chiefly in the bedrock aquifer. The δ¹³C values of CH₄ and C₂H₆ for the majority of thermogenic gases from water wells either matched or were between values for the samples of non-native storage-field gas from injection wells and the samples of gas from storage-field observation wells. Traces of C₂H₆ with microbial CH₄ and a range of C and H isotopic compositions of CH₄ indicate gases of different origins are mixing in sub-surface pathways; gas mixtures are present in groundwater. Pathways for gas migration and a specific source of the gases were not identified. Processes responsible for the presence of microbial gases in groundwater could be elucidated with further geochemical study.     

赣南地热气体起源的同位素与地球化学证据

对取自赣南地区10个温泉的地热气体进行了气体化学成分及氦、碳、氖同位素组成的分析。该区地热气体可分为CO₂型和N₂型两种类型。CO₂型地热气体分布在赣南东南部地区,主要成分是CO₂,占总体积96.47%以上,二氧化碳气体的δ¹³C值为 -5.50‰～-3.49‰（PDB）,平均为 -4.66‰,为幔源无机成因,其氦同位素组成为1.36～2.27 R_a,具有明显的幔源成因特征,最高约有28.2%的氦源于地幔,其N₂-Ar-He关系研究表明,该型地热气体中的氮源于地幔-地壳-大气混合成因。研究揭示该区CO₂型地热气体属幔源无机成因气,是地幔脱气作用的产物。N₂型地热气体分布在赣南西部地区,N₂含量占91.04%以上,其中二氧化碳气体的δ¹³C值为 -23.7‰～-12.6‰,平均为 -17.82‰,为壳源有机成因,其氦同位素组成为0.06～0.13 R_a,具有明显的壳源放射性成因特征,³He/⁴He 与 ⁴He/²⁰Ne关系和He-Ar-N₂关系研究表明,N₂型温泉气主要来源于大气,并有壳源气体的贡献。     

Strontium isotopic evidence for the origin of siderite,ankerite and magnesite mineralizations in the Eastern Alps

Metasomatic magnesite, siderite and ankerite mineralizations within Paleozoic sediments of the Northern Greywacke zone and its metamorphic counterpart in the crystalline basement (Upper Austroalpine unit) were investigated with respect to their strontium isotopic composition. The results support a sedimentary (s.l.) model for the magnesites within Viséan platform carbonates of the Veitsch nappe and an epigenetic hydrothermal model for the siderites and ankerites in Devonian platform carbonates of the Noric nappe and from Hüttenberg. The Fe transporting fluids can be characterized either as magmatogene or, more probably, as metamorphogene. By increasing the stage of recrystallization and/or remobilization due to at least two later metamorphic overprints, Sr in the various ore minerals beame ± enriched in radiogenic ⁸⁷Sr.     

Optically stimulated luminescence ages of the Hengyu site and their implications for anthropogenic activities in the Fuzhou Basin,South China

The chronologies of few Neolithic sites in the lower reaches of the Min River of China have been well investigated for the middle to late Holocene. In this study, the Hengyu Neolithic site in Fujian Province, South China, which has significant archaeological remains, was dated using blue‐stimulated optically stimulated luminescence (OSL) and accelerator mass spectrometry radiocarbon (AMS¹⁴C) techniques. The results, comprising nine OSL and three AMS¹⁴C ages through the Neolithic sequence, provide new evidence towards understanding the relationship between environmental evolution and human activities in the middle to late Holocene in the Fuzhou Basin and coastal areas of South China. The ages of the site deposits vary from 6.83 to 1.67 ka and can be divided into two main phases: the Keqiutou–Tanshishan culture period and the Bronze culture period. In contrast, the persistent periods of ancient human activities at the Hengyu site seem to correspond to regional sea‐level changes and the East Asian winter monsoon as a secondary factor, which can affect human activities through sea‐level impacts. The warm and high sea level conditions provided a liveable environment for the ancient humans of Fujian and even South China. The ages of two building column bases are linked to the early stage of the Han dynasty, suggesting a potentially favourable habitation environment; that is, ancient humans occupied and settled this area for the long term within this time period, which is consistent with sea‐level changes and palynology records. Copyright © 2019 John Wiley & Sons, Ltd.     

Novel C15 sesquiterpanes in Niger Delta oils: Structural identification and potential application as new markers of angiosperm input in light oils

Two new C₁₅ sesquiterpanes have been isolated from a Niger Delta oil. Based on nuclear magnetic resonance (NMR) data, their structures are similar to the ring D and E part of oleanane. The mass spectra show an m/z 193 base peak typical of rearranged drimanes. They have been found only in oleanane-containing oils with a Cretaceous or Tertiary source. Data are presented for 34 such oils from Angola, Canada, Greece, India, Indonesia, Iran, New Zealand, Nigeria, Thailand and Vietnam. The ratio between the new sesquiterpanes and rearranged drimanes roughly follows the oleanane index. They are absent from marine oils whose source rock age (Jurassic or older) predates the evolution and proliferation of angiosperms. They are probably formed via degradation of functionalized oleanoids or by cleavage of seco-oleananes. These sesquiterpanes may be useful as markers of angiosperm input in light oils (jet fuel, diesel or condensates) usually devoid of higher molecular weight markers for higher plant input.     

Pb-isotope evidence for the origin of lead in strata-bound Pb-Zn deposits in triassic carbonates of the Eastern and Southern Alps

A comparison of ore-lead isotope ratios of Pb-Zn deposits hosted in Triassic carbonates of the Eastern and Southern Alps with the isotopic composition of trace leads of their host rocks, of Triassic volcanics, and of the underlying clastic sediments shows that these rocks could have supplied only part of the ore lead. The isotopic signature of feldspar lead from crystalline basement rocks, however, reveals that they must have contributed a significant amount of metal to these deposits. The presence of barite and of thallium is also indicative that feldspars were the main source of lead. Arsenic is one of the few important trace elements in these deposits and is known to occur in some areas of Lower Paleozoic metasediments in unusually high concentrations. Any model explaining the origin of these deposits must consider the extensive leaching of the basement and to some extent of the overlying clastic sediments as well. How the metal-bearing solutions entered the lagoonal back-reef areas is still open to question as feeder channels have not yet been positively identified. The results further demonstrate that the basement also acted as a metal source for galena-bearing deposits hosted in Permian sediments, vein-type deposits in Permian volcanics, and probably the barite-fluorite polymetallic deposits along a Devonian erosional surface in the Carnic Alps as well.     

Geochemical and C, O, Sr, and U-series isotopic evidence for the meteoric origin of calcrete at Solitario Wash, Crater Flat, Nevada, USA

Calcite-rich soils (calcrete) in alluvium and colluvium at Solitario Wash, Crater Flat, Nevada, USA, contain pedogenic calcite and opaline silica similar to soils present elsewhere in the semi-arid southwestern United States. Nevertheless, a ground-water discharge origin for the Solitario Wash soil deposits was proposed in a series of publications proposing elevation-dependent variations of carbon and oxygen isotopes in calcrete samples. Discharge of ground water in the past would raise the possibility of future flooding in the unsaturated zone at Yucca Mountain, Nevada, site of a proposed high-level nuclear waste repository. New geochemical and carbon, oxygen, strontium, and uranium-series isotopic data disprove the presence of systematic elevation-isotopic composition relations, which are the main justification given for a proposed ground-water discharge origin of the calcrete deposits at Solitario Wash. Values of δ¹³C (−4.1 to −7.8 per mil [‰]), δ¹⁸O (23.8–17.2‰), ⁸⁷Sr/⁸⁶Sr (0.71270–0.71146), and initial ²³⁴U/²³⁸U activity ratios of about 1.6 in the new calcrete samples are within ranges previously observed in pedogenic carbonate deposits at Yucca Mountain and are incompatible with a ground-water origin for the calcrete. Variations in carbon and oxygen isotopes in Solitario Wash calcrete likely are caused by pedogenic deposition from meteoric water under varying Quaternary climatic conditions over hundreds of thousands of years.