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1.
B. Anu Radha P. L. Srinivasa Rao M. A. Rasheed D. J. Patil A. M. Dayal 《Journal of the Geological Society of India》2012,80(6):802-812
Seepage of hydrocarbons, either as macroseepage or microseepage, can set up near-surface oxidation-reduction zones that favour the development of a diverse array of chemical and mineralogic changes. In this study trace metal alterations were mapped that appear to be associated with hydrocarbon microseepages in the oil/gas fields. A total of 210 soil samples were collected from near surface sediments of Kutch and Saurashtra Basins, India. The soil samples were collected from a depth of 2–2.5 m. The paper reports the chemical alterations associated with trace metals in soils that are related to hydrocarbon microseepages above the Kutch and Saurashtra Basins, India. The soil samples for trace metals; Scandium (Sc), Vanadium (V), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Barium (Ba) and Strontium (Sr) were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The concentrations of the trace elements ranged between for Sc (12.69 to 21.91 ppm), V (109.20 to 436.05 ppm), Cr (87.15 to 481.57 ppm), Co (18.25 to 64.31 ppm), Ni (57.55 to 263.15 ppm), Cu (44.88 to 143.96 ppm), Zn (137.60 to 502.31 ppm), Ba (149.27 to 921.46 ppm) and Sr (143.93 to 425.63 ppm) were obtained. It was observed that trace elements concentrations were tremendously increased when compared with normal concentration in the soils. The adsorbed soil gas analysis showed the presence of high concentrations of ΣC2+ (C2H6, C3H8 and n-C4H10) ranged between 1 to 121 ppb respectively. Integrated studies of trace elements over adsorbed light gaseous hydrocarbon (ΣC2+) anomalies showed good correlation. The carbon isotopic composition of δ13C1 of the samples ranges between — 36.6 ‰ to ?22.7‰ (Pee Dee Belemnite) suggest thermogenic source for hydrocarbon gases. The increase in trace metal concentrations near oil/gas producing areas, suggests that soil chemical change to a reducing environment, presumably due to the influence of hydrocarbon microseepage, which could be applied with other geo-scientific data to identify areas of future hydrocarbon exploration in the frontier areas. 相似文献
2.
Heavy metal pollution assessment through comparison of different indices in sewage-fed fishery pond sediments at East Kolkata Wetland,India 总被引:3,自引:0,他引:3
Subhasis Sarkar Phani Bhusan Ghosh Alok Kumar Sil Tapan Saha 《Environmental Earth Sciences》2011,63(5):915-924
The sediments of the raw sewage-fed fishpond system at East Kolkata Wetland (EKW) were analyzed for heavy metal content in
a comprehensive way. Various indices of contamination like enrichment factor (EF), geo-chemical index (I
geo), modified degree of contamination (mDC), and pollution load index (PLI) were assessed. In all cases, instead of literature values, the metal concentrations of less
contaminated sites, separated by the statistical approach of the hierarchical cluster analysis, were used as baseline values.
In the present study, about 70% of the pond sediments are found uncontaminated, 5% display low degree of contamination and
25% are designated as moderate degree of contamination. Both the EF and I
geo indices highlighted that the metals lead (Pb), cadmium (Cd), and chromium (Cr) are responsible for the contamination while
there is little anthropogenic input in cases of Cu, Zn, and Ni. Most of the ponds situated near the main sewage flowing canals
as well as the main traffic highway and close to the solid waste dumping areas recorded higher degree of metal contamination
as evident from spatial variation of mDC and PLI indices in the study area. Indices comparison study clearly indicates that although these are calculated using different
methods, these may or may not produce the same indices values and hence the values should neither be compared nor be averaged.
But all the above indices are directly related to a common term contamination factor (CF). Classification of contamination
levels based on these CF values is found to be similar and this classification is only valid up to the level of high degree
of contamination. Thus, the use of any one of these indices is sufficient to classify the degree of contamination of an area.
However, to evaluate the contamination per metal, both I
geo and EF are effective while, to assess the composite effect of all the metals, PLI is preferable to mDC. 相似文献
3.
The magnetic behaviour and Curie temperatures (T
C
) of spinelloids and spinels in the Fe3O4–Fe2SiO4 and Fe3O4–(Mg,Fe)2SiO4 systems have been determined from magnetic susceptibility (k) measurements in the temperature range –192 to 700 °C. Spinelloid II is ferrimagnetic at room temperature and the k measurements display a characteristic asymmetric hump before reaching a T
C
at 190 °C. Spinelloid V from the Mg-free system is paramagnetic at room temperature and hysteresis loops at various low temperatures indicate a ferri- to superparamagnetic transition before reaching the T
C
. The T
C
shows a non-linear variation with composition between –50 and –183 °C with decreasing magnetite component (X
Fe3O4). The substitution of Mg in spinelloid V further decreases T
C
. Spinelloid III is paramagnetic over nearly the total temperature range. Ferrimagnetic models for spinelloid II and spinelloid V are proposed. The T
C
of Fe3O4–Fe2SiO4 spinel solid solutions gradually decrease with increasing Si content. Spinel is ferrimagnetic at least to a composition of X
Fe3O4=0.20, constraining a ferrimagnetic to antiferromagnetic transition to occur at a composition of X
Fe3O4<0.20. A contribution of the studied ferrimagnetic phases for crustal anomalies on the Earth can be excluded because they lose their magnetization at relatively low temperatures. However, their relevance for magnetic anomalies on other planets (Mars?), where these high-pressure Fe-rich minerals could survive their exhumation or were formed by impacts, has to be considered. 相似文献
4.
Although marine lagoons are ubiquitous features along coastal margins, studies investigating the dynamics of metal, organic
matter, and nutrient concentrations in such systems are rare. Here we present a comprehensive examination of the temporal
and spatial gradients in dissolved trace metals (Ag, Cd, Cu, Mn, Pb), organic and inorganic nutrients (POC, PON, DOC, N03
−, NH4
+, H4SiO4, PO4
−3, and urea), and algal biomass in a lagoon estuary, Great South Bay (GSB), New York, USA. While this estuary has experienced
a series of environmental problems during recent decades (urbanization, loss of fisheries, harmful algal blooms), root causes
are largely unknown, in part because levels of bioactive substances, such as trace metals, have never been measured. Sampling
was undertaken within multiple estuarine, riverine, and groundwater sites during spring, summer, and fall. Trace metal tracers
(e.g., Ag, Mn) and statistical analyses were used to differentiate the influences of natural and anthropogenic processes on
the chemical composition of the lagoon. Our analyses revealed three clusters of biogeochemical constituents that behaved similarly
in GSB: constituents under strong biological control such as POC, PON, DOC and chlorophyll,a; elements indicative of benthic remobilization processes such as Mn, Cd, and Cu; and constituents strongly influence by anthropogenic
processes such as Ag, Pb, PO4
−3, NO3
−, and NH4
+. Although GSB is surrounded by a densely populated watershed (c. 1 million people), it does not appear to be significantly
contaminated by trace metals compared to other urban estuaries. Levels of DOC (up to 760 μM) in GSB were well correlated with
phytoplankton biomass and exceeded at least 98% of values reported in similar mid Atlantic estuaries at the same salinities.
These high levels of DOC are likely to be an important source of carbon export to the coastal ocean and likely promote mixotrophic
harmful algal blooms in this system. 相似文献
5.
A series of even carbon numbered α, ω-dicarboxylic acids ranging from C16 to C24 has been identified in recent sediments from various environments and sampling localities. A lacustrine sediment did not show detectable quantities of diacids. Consideration of quantitative relationships involving the diacids leads us to propose a dual origin for these diacids: deposition by mangroves is their main source in mangal areas while in situ production by sedimentary organisms is the only important source of diacids in a non-mangal marine environment. A fresh water lagoon shows an intermediate situation between these extremes. 相似文献
6.
Orabi H. Orabi Abd El-Monsef A. El-Badry Ikhlas Alhejoj 《Journal of the Geological Society of India》2018,91(5):583-588
The identified mollusks from the Burullus lagoon of Egypt (Eastern Mediterranean) are represented by four bivalve species and four gastropod species. Sources of heavy metals pollution in the Burullus lagoon include phosphate fertilizers, sewage and oil spills from fishing boats.The Cerastoderma glaucum species has a wide distribution in the central part of the studied area with satisfying criteria required for good bio-monitors of pollution. High concentrations of heavy metals are found in water, at the eastern side of the lagoon, while low concentrations were detected in the central and western sides of the lagoon. Pirenella conica constitutes the total gastropods assemblages, reflecting this species tolerance to the high concentration of heavy metals. Meanwhile, the total pelecypods in bottom lagoon sediments are completely absent in the eastern parts of the lagoon, which may be due to the sensitivity of pelecypods to the accumulation of heavy metals. 相似文献
7.
Asmae Mhamdi Alaoui Mohamed Choura Mohamed Maanan Bendahhou Zourarah Marc Robin Maria Freitas Conceição César Andrade Mehdi Khalid Christian Carruesco 《Environmental Earth Sciences》2010,61(2):275-286
The metal content in surface sediments (0–2 cm, 26 samples), in a sediment core (120, 1 cm slices), taken from Moulay Bousselham
(Morocco) was investigated. Concentrations of Al, Fe, Mn, Pb, Zn, Cu, Ni, Cr, Cd, As, and Hg were evaluated in surface and
cored sediments of Moulay Bousselham lagoon. Significantly high concentrations in μg g−1 dw of Pb (31.7–6.2), Zn (758.9–167), Cu (310.7–22), Ni (96–10.5), Cr (113–18.9), Cd (0.84–0.02), As (1–0.1), and Hg (0.61–0.02)
were found in sediment samples from Moulay Bousselham lagoon. Calculated enrichment factors [EFMe = (Me/Al)sample/(Me/Al)background], using Al as a normalizer, and correlation matrices showed that metal pollution in Merja Zerga of Moulay Bousselham lagoon
was the product of anthropogenic sources, while the metal content in Merja Kehla was of natural origins. The results suggest
that a major change in the sedimentary regime of the lagoon, associated with internal trapping and re-distribution of heavy
metal, has been occurring in the past few decades. The cause would appear to be the construction of a Nador Canal at the lagoon.
Probable effects concentrations (PEC) were often exceeded for heavy metals in the lagoon sediments, especially for Zn, Cu,
Ni, and Cr, and four stations, stations MZ-11, MZ-12, MZ-13, MZ-14, MZ-16, and MZ-17, had multiple metals at presumptively
toxic levels. These comparisons suggest that sediment metal levels in the river are clearly high and probably pose an environmental
risk at some stations. The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance
when contamination issues are at stake. Metal concentrations found in Moulay Bousselham lagoon were comparable to aquatic
systems classified as contaminated from other regions of the world. 相似文献
8.
John Rapaglia 《Estuaries and Coasts》2005,28(5):705-713
Venice Lagoon, Italy, rests on a series of aquifers that are 1,000 m thick. Measurements of submarine groundwater discharge
(SGD) were made in Venice Lagoon using benthic chambers vented to a plastic collection bag. Two hundred measurements taken
in a pristine northern lagoon site (Isola la Cura) revealed flow rates as high as 200 cm d−1 with an average of 30 cm d−1. Over 100 measurements taken adjacent to a bulkhead shoreline in the Porto Marghera industrial zone (Fusina) showed flow
rates as high as 30 cm d−1 and averaging 6 cm d−1. These flow rates, if representative of even a fraction of the lagoon floor, are easily able to account for the 15% deficit
previously calculated between precipitation and runoff for the entire Venice Lagoon drainage basin. Land elevation surrounding
the Venice Lagoon is < 10 m within 20 km of the shoreline and is unable to support any substantial onshore water table. Submarine
groundwater discharge most likely represents upward artesian discharge from deeper partially confined aquifers. Over 60 samples
were collected in total from both sites for nutrient analysis. Ammonium concentration was found to be 2–8 fold higher in the
device water than in the lagoon water at the northern site depending on season, and 10–30 times higher at the industrial zone
site. These numbers suggest that SGD may be the primary pathway for nutrients and perhaps other contaminants to enter Venice
Lagoon. 相似文献
9.
Effect of contact time,pH, and ionic strength on Cd(II) adsorption from aqueous solution onto bentonite from Gaomiaozi,China 总被引:4,自引:2,他引:2
Yong-Gui Chen Wei-Min Ye Xiao-Min Yang Fei-Yue Deng Yong He 《Environmental Earth Sciences》2011,62(2):329-336
Copper smelting and toxic emissions in Sarcheshmeh Copper Complex have resulted in soil pollution especially in the vicinity
of the smelting plant. Calculated geoaccumulation index, contamination factor (C
f), and contamination degree (C
deg) indicate surface soil enrichment in potentially toxic metals (As, Cu, Pb, Zn, Mo, and Cd). The results also indicate that
most contaminated areas are located in the prevailing wind directions (N and NE). However, continuous copper smelting can
result in extensive pollution in the study area. This is especially alarming for adjacent townships. Since, the sampled sites
are also used as grazing land, the soils are likely to become phytotoxic and provide a potential pathway for the toxic elements
to enter the food chain. C
f based on distance and direction give more reasonable results; that is, the decrease of contamination degree with distance.
This is in agreement with I
geo and also statistical analysis, which show a decreasing trend of metal loadings of soil with distance from the smelter. Statistical
analysis reaffirms the polluting role of the smelting plant. 相似文献
10.
The Deccan Syneclise is considered to have significant hydrocarbon potential.However,significant hydrocarbon discoveries,particularly for Mesozoic sequences,have not been established through conventional exploration due to the thick basalt cover over Mesozoic sedimentary rocks.In this study,near-surface geochemical data are used to understand the petroleum system and also investigate type of source for hydrocarbons generation of the study area.Soil samples were collected from favorable areas identified by integrated geophysical studies.The compositional and isotopic signatures of adsorbed gaseous hydrocarbons(methane through butane) were used as surface indicators of petroleum micro-seepages.An analysis of 75 near-surface soil-gas samples was carried out for light hydrocarbons(C1-C4) and their carbon isotopes from the western part of Tapti graben,Deccan Syneclise,India.The geochemical results reveal sites or clusters of sites containing anomalously high concentrations of light hydrocarbon gases.High concentrations of adsorbed thermogenic methane(C_1 = 518 ppb) and ethane plus higher hydrocarbons(ΣC_(2+) = 977 ppb) were observed.Statistical analysis shows that samples from 13% of the samples contain anomalously high concentrations of light hydrocarbons in the soil-gas constituents.This seepage suggests largest magnitude of soil gas anomalies might be generated/source from Mesozoic sedimentary rocks,beneath Deccan Traps.The carbon isotopic composition of methane,ethane and propane ranges are from-22.5‰ to-30.2‰ PDB,-18.0‰to 27.1‰ PDB and 16.9‰-32.1‰ PDB respectively,which are in thermogenic source.Surface soil sample represents the intersection of a migration conduit from the deep subsurface to the surface connected to sub-trappean Mesozoic sedimentary rocks.Prominent hydrocarbon concentrations were associated with dykes,lineaments and presented on thinner basaltic cover in the study area,which probably acts as channel for the micro-seepage of hydrocarbons. 相似文献
11.
Yangming Zhu 《中国地球化学学报》2001,20(1):73-87
Based on the compositions and distributions of biomarkers in thirty-five representative oil samples, oils from the Tarim Basin of northwestern China are mainly divided into two oil families. One oil family contains relatively low amounts of C15-C20 isoprenoid hydrocarbons and shows pristane predominance with Pr/Ph ratios ranging from 1.50 to 3.00. The GC/MS analytical data of these oils show the occurrence of abundant hopanes, and low concentrations of steranes and tricyclic terpanes with hopanes/steranes ratios from 6.25 to 12.24 and tricyclic terpanes/hopanes ratios from 0.03 to 0.24. These oils contain low drimane relative to homodrimane (C15/C16 < 1.0) and abundant rearranged bicyclanes in bicyclic sesquiterpanes. They are dominated by low carbon number (C19-C21) compounds in the tricyclic terpanes, and are rich in rearranged hopanes, C29Ts and an unknown C30 compound in pentacyclic triterpanes. These geochemical characteristics suggest that the oils were generated mainly from terrigenous organic matter. The other oil family shows remarkably different biomarker compositions and distributions. The oils revealed Pr/Ph ratios of about 1.0, high drimane/homodrimane ratios (>1.0), low hopanes/steranes ratios (0.65–2.50), high tricyclic terpanes/hopanes ratios (0.30–2.00) and a dominant peak at C23 in tricyclic tepanes, suggesting a marine organic origin. Oil-source rock correlation indicates that these two oil families seem to have been derived from Mesozoic Jurassic-Triassic terrestrial source rocks (shales and coal seams) and Lower Paleozoic Ordovician-Cambrian marine source rocks, respectively. 相似文献
12.
Near surface manifestation of hydrocarbons in Proterozoic Bhima and Kaladgi Basins: Implications to hydrocarbon resource potential 总被引:1,自引:0,他引:1
M. S. Kalpana D. J. Patil A. M. Dayal S. V. Raju 《Journal of the Geological Society of India》2010,76(6):548-556
Reconnaissance surface geochemical survey for adsorbed soil gas analysis conducted in Proterozoic Bhima and Kaladgi Basins,
have revealed occurrence of anomalous concentrations of light gaseous hydrocarbons i.e. C1 to C4 (CH4, C2H6, C3H8, i-C4H10 and n-C4H10) in the near surface soils. The concentrations of C1 and ΣC2+(C2H6+C3H8+ i-C4H10+ n-C4H10) in Bhima and Kaladgi Basins are in the range of 1–2594 ppb and 1 to 57 ppb and 1–1142 ppb and 1–490 ppb, respectively. The
carbon isotopic data of adsorbed soil gas methane in few selected samples are in the range of −29.9 to −39‰ (PDB). The evaluation
of adsorbed soil gas data indicates that all the gas components are cogenetic and hydrocarbon ratios of C1/(C2+C3) < 10 and C3/C1*1000 between 60–500 and 20–60 suggest that the adsorbed gases are derived from oil and gas-condensate zones. The carbon isotopic
values of methane further support thermogenic origin of these migrated gases. The concentration distribution of C1 and ΣC2+ in the study areas illustrate C1 and ΣC2+ anomalies near Katamadevarhalli, Andola and Talikota in Bhima Basin and near Kaladgi, Lokapur and north of Mudhol in Kaladgi
Basin. The hydrocarbon anomalies near the surface coincide with the favourable subsurface structural features and correlate
with existing geochemical and geophysical data in these basins suggesting seepage related anomalies. 相似文献
13.
The organic geochemical methods of hydrocarbon prospecting involve the characterization of sedimentary organic matter in terms of its abundance, source and thermal maturity, which are essential prerequisites for a hydrocarbon source rock. In the present study, evaluation of organic matter in the outcrop shale samples from the Semri and Kaimur Groups of Vindhyan basin was carried out using Rock Eval pyrolysis. Also, the adsorbed low molecular weight hydrocarbons, methane, ethane, propane and butane, were investigated in the near surface soils to infer the generation of hydrocarbons in the Vindhyan basin. The Total Organic Carbon (TOC) content in shales ranges between 0.04% and 1.43%. The S1 (thermally liberated free hydrocarbons) values range between 0.01–0.09 mgHC/gRock (milligram hydrocarbon per gram of rock sample), whereas the S2 (hydrocarbons from cracking of kerogen) show the values between 0.01 and 0.14 mgHC/gRock. Based on the Tmax (temperature at highest yield of S2) and the hydrogen index (HI) correlations, the organic matter is characterized by Type III kerogen. The adsorbed soil gas, CH4 (C1), C2H6 (C2), C3H8 (C3) and nC4H10, (nC4), concentrations measured in the soil samples from the eastern part of Vindhyan basin (Son Valley) vary from 0 to 186 ppb, 0 to 4 ppb, 0 to 5 ppb, and 0 to 1 ppb, respectively. The stable carbon isotope values for the desorbed methane (δ13C1) and ethane (δ13C2) range between −45.7‰ to −25.2‰ and −35.3‰ to −20.19‰ (VPDB), respectively suggesting a thermogenic source for these hydrocarbons. High concentrations of thermogenic hydrocarbons are characteristic of areas around Sagar, Narsinghpur, Katni and Satna in the Son Valley. The light hydrocarbon concentrations (C1–C4) in near surface soils of the western Vindhyan basin around Chambal Valley have been reported to vary between 1–2547 ppb, 1–558 ppb, 1–181 ppb, 1–37 ppb and 1–32 ppb, respectively with high concentrations around Baran-Jhalawar-Bhanpur-Garot regions (Kumar et al., 2006). The light gaseous hydrocarbon anomalies are coincident with the wrench faults (Kota – Dholpur, Ratlam – Shivpuri, Kannod – Damoh, Son Banspur – Rewa wrench) in the Vindhyan basin, which may provide conducive pathways for the migration of the hydrocarbons towards the near surface soils. 相似文献
14.
Lipid geochemistry in a sediment core from Ruoergai Marsh deposit (Eastern Qinghai-Tibet plateau, China) 总被引:3,自引:0,他引:3
Peats in a sediment core from Ruoergai bog, which has a cold and moist plateau climate with major source input from herbaceous plants, have been studied by GC–MS in order to understand the composition and diagenetic processes of lipids in this depositional environment. Long chain components (C21–C35) predominate in the n-alkanes, n-alk-1-enes, n-fatty acids, n-alkan-2-ones and n-alkanols with a maximum of C31, C27, C22 or C24, C23 or C25 and C22, respectively. A herbaceous origin for these long chain compounds is suggested, and this is supported by their stable carbon isotopic compositions. Diterpenoid hydrocarbons with abietane, pimarane and kaurane skeletons, some of which have not been reported often in modern sediments, are prominent and are derived from higher plants. Several triterpenoid ketones and alcohols with oleanane or lupane skeletons, and a series of des-A-triterpenoid hydrocarbons which have not been reported often in modern sediments are also present, and are assigned to a higher plant source. Hopanoids, including their alkanes, alkenes, ketones, alcohols and esters, are abundant and of bacterial origin. Steroid ketones and alkanols are dominated by C29 homologues. C28 and C29 steroids are derived mainly from higher plants, whereas the C27 component is assigned to a microbial source. The presence of short-chain n-alkanes with no odd-even carbon predominance, bacterially derived fatty acids (C14, C15, iso- and unsaturated acids), n-alkan-2-ones, des-A-triterpenoid hydrocarbons, hopanoids and some steroid ketones indicate that intense microbial reworking of the organic matter has taken place in this depositional environment. The chemical and biochemical conversions of some cyclic alkenes to alkanes, such as tricyclic diterpenoids, tetracyclic terpenoids and steroid ketones, are also evident with depth. The dominance of C20 components in the diterpenoid hydrocarbons may reflect an oxidizing or reducing depositional condition. 相似文献
15.
We here report the discovery of unusual distributions of long-chain alkenones (C37-C42) in two Cretaceous black shales from the Blake-Bahama Basin, western North Atlantic. These sediments are Cenomanian (c. 95 Ma) and mid-Albian (c. 105 Ma) in age, thus significantly extending the geological range of these compounds. The precise source of these lipids is, as yet, unknown, although they may derive from an ancient ancestor of Emiliania huxleyi. 相似文献
16.
J. J. Hanley J. E. Mungall T. Pettke E. T. C. Spooner C. J. Bray 《Mineralium Deposita》2005,40(3):237-256
We report methane-dominant hydrocarbon (fluid) inclusions (CH4±C2H6–C2H2, C3H8) coexisting with primary brine inclusions and secondary halide melt (solid NaCl) inclusions in Au–Pt-rich quartz-sulfide-epidote
alteration veins associated with the footwall-style Cu–PGE (platinum-group element)–Au deposits at the Fraser Mine (North
Range of the Sudbury Igneous Complex). Evidence for coentrapment of immiscible hydrocarbon–brine, and hydrocarbon–halide melt
mixtures is demonstrated. A primary CH4–brine assemblage was trapped during quartz growth at relatively low T (min. T
trapping∼145–315°C) and P (max. P
trapping∼500 bar), prior to the crystallization of sulfide minerals in the veins. Secondary inclusions contain solid halite and a
mixture of CH4, C2H6–C2H2 and C3H8 and were trapped at a minimum T of ∼710°C. The halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally
postdate (by replacement) early alteration quartz hosting the primary, lower T brine–CH4 assemblage. Laser ablation ICP-MS analyses show that the brine, hydrocarbon and halide melt inclusions contain significant
concentrations of Cu (0.1–1 wt% range), Au, Bi, Ag and Pt (all 0.1–10 ppm range). Cu:Pt and Cu:Au ratios in the inclusions
are significantly (up to 4 log units) lower than in the host alteration veins and adjacent massive sulfide ore veins, suggesting
either (1) early Cu loss from the volatiles by chalcopyrite precipitation or (2) enhanced Au and Pt solubilities relative
to Cu at the temperatures of entrapment. Concentration ratios between coexisting brine and CH4 inclusions
are lower for Cu, Au, Bi and Ag than for other elements (Na, Ca, Fe, Mn, Zn, Pb) indicating that during interaction with
the brine, the hydrocarbon phase was enriched in ore metals. The high concentrations of ore metals in hydrocarbon, brine and
halide melt phases confirm that both aqueous and non-aqueous volatiles were carriers of precious metals in the Sudbury environment
over a wide range of temperatures. Volatile evolution and magmatic sulfide differentiation were clearly part of a single,
continuous process in the Sudbury footwall. The exsolution of H2O-poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of
PGE and Au in the footwall ore systems. The study reports the first measurements of precious metal concentrations in fluid
inclusions from a magmatic Ni–Cu–PGE environment (the Sudbury district).
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
17.
David J. Grimes Walter H. Ficklin Allen L. Meier John B. Mchugh 《Journal of Geochemical Exploration》1995,52(3)
Ground-water, alluvium, and bedrock samples were collected from drill holes near the Chimney Creek, Preble, Summer Camp, and Rabbit Creek disseminated gold deposits in northern Nevada to determine if Au and ore-related metals, such as As, Sb, and W, are being hydromorphically mobilized from buried mineralized rock, and, if they are, to determine whether the metal-enriched ground water is reacting with the alluvial material to produce a geochemical anomaly within the overburden.Results of chemical analyses of drill-hole water samples show the presence of hydromorphic dispersion anomalies of Au, As, Sb, and W in the local ground-water systems associated with these deposits. Background concentrations for Au in the ground water up-gradient from the buried deposits was less than 1 nanogram per liter (ng/L), near the deposits the Au values ranged from 1 to 140 ng/ L, and in drill holes penetrating mineralized rock, concentrations of Au in the ground water were as high as 4700 ng/L. Highest concentrations of Au were found in ground-water samples where the measured Eh and the distribution of arsenic species, arsenite [As(III)] and arsenate [As(V)], indicated oxidizing redox potentials. Similarly, As, Sb, and W concentrations in the ground water near the deposits were significantly enriched relative to concentrations in the ground water up-gradient from the deposits. In general, however, the highest concentrations of As, Sb, and W occurred in ground-water samples where the measured Eh and the distribution of arsenic species indicated reducing conditions. Arsenic concentrations ranged from 9 to 710 micrograms per liter (μg/L); Sb, from less than 0.1 to 250 μg/L; and W, from 1 to 260 μg/L.In addition, analysis of sequential dissolution and extraction solutions of drill cuttings of alluvium and bedrock indicate geochemical anomalies of gold and ore-related metals in the overburden at depths corresponding to the location of the present-day water table. This relationship suggests that water-rock reactions around these buried deposits are active and that this information could be very useful in exploration programs for concealed disseminated gold deposits. 相似文献
18.
A revised equation is proposed to represent and extrapolate the heat capacity of minerals as a function of temperature: C
P=k0+k1
T
–0.5+k2
T
–2+k3
T
–3 (where k1, k20).This equation reproduces calorimetric data within the estimated precision of the measurements, and results in residuals for most minerals that are randomly distributed as a function of temperature. Regression residuals are generally slightly greater than those calculated with the five parameter equation proposed by Haas and Fisher (1976), but are significantly lower than those calculated with the three parameter equation of Maier and Kelley (1932).The revised equation ensures that heat capacity approaches the high temperature limit predicted by lattice vibrational theory (C
P=3R+2VT/). For 16 minerals for which and have been measured, the average C
Pat 3,000 K calculated with the theoretically derived equation ranges from 26.8±0.8 to 29.3±1.9 J/(afu·K) (afu = atoms per formula unit), depending on the assumed temperature dependence of . For 91 minerals for which calorimetric data above 400 K are available, the average C
Pat 3,000 K calculated with our equation is 28.3±2.0 J/(afu·K). This agreement suggests that heat capacity extrapolations should be reliable to considerably higher temperatures than those at which calorimetric data are available, so that thermodynamic calculations can be applied with confidence to a variety of high temperature petrologic problems.Available calorimetric data above 250 K are fit with the revised equation, and derived coefficients are presented for 99 minerals of geologic interest. The heat capacity of other minerals can be estimated (generally within 2%) by summation of tabulated oxide component C
Pcoefficients which were obtained by least squares regression of this data base. 相似文献
19.
Heather Clegg Brian Horsfield Heinz Wilkes Jaap Sinninghe Damst Martin P. Koopmans 《Organic Geochemistry》1998,29(8):1953-1960
Hydrous pyrolysis experiments were performed on the Ghareb Formation (Upper Cretaceous, Jordan), a carbonate- and organic-rich (TOC 19.6%) source rock, using a temperature range of 200 to 360°C (72 h). The original sediment contains only low amounts of carbazoles, (maximum 2.2 μg/g bitumen for 1-methylcarbazole). With increasing thermal maturation, intense generation begins at temperatures only in excess of 300°C, reaching a maximum at 360°C. Likewise, during natural maturation, generation occurs at later stages of maturity (e.g. for Tithonian source rocks at >0.81% Rr and for Posidonia Shale at >0.88% Rr). Some isomeric changes during hydrous pyrolysis do not resemble those in nature whereas others do. The relative abundances of selected C1- and C2-alkylcarbazoles on ternary diagrams reveal differences, whereas the benzo[a]carbazole/benzo[a]carbazole+benzo[c]carbazole ratio is closely similar. The latter result supports the contention that maturation plays a key role in controlling carbazole distributions in source rocks. However, the results for alkylcarbazoles, especially the C2-carbazoles, are not easy to interpret. 相似文献
20.
Chrysoula Christia Eva Papastergiadou George Papatheodorou Maria Geraga Emmanouil Papadakis 《Environmental Earth Sciences》2014,71(8):3543-3558
Temporal and spatial variations of environmental and water quality parameters and their relations with macrobenthic flora were investigated in an eastern Mediterranean lagoon. Kaiafas is a mesohaline lagoon, which is influenced by point and diffused sources from the adjacent agricultural land and the nearby city. Water samples were analyzed for physicochemical parameters, microbial load and primary production, on a seasonal and spatial scale, while heavy metal concentrations were measured into two different sediment cores. An overall analysis of seasonal dynamics of water parameters and Chl-a based on trophic index TSI pointed out the lagoon as eutrophic. According to water quality parameters the lagoon was separated into two parts. The southern sector of the lagoon which was more affected by human activities showed higher nutrients, Chl-a, heavy metals and total Coliforms concentrations. Sediment texture and distribution of macrophytes were detected through the acoustic side scan sonar method, which proved to be a promising tool for defining and monitoring vegetation coverage of shallow lagoons. A number of distinct echo types and three different sediment types were revealed on the basis of the backscatter level and the variability of low and high backscatter areas. Furthermore, the extension and the coverage of Potamogeton pectinatus and Chara hispida f. corfuensis were successively depicted by combining the data of SSS and ground truthing samples. Meadows of P. pectinatus were established to the lagoon limits where high turbidity and silty substrate occurred, while C. hispida f. corfuensis was limited in deep and high transparent waters with sandy substrate. 相似文献