Origin of trace element distribution patterns in sulfides of the central and bingham districts,western U.S.A.

Trace element abundances in sulfides of these two large hydrothermal ore districts allow distinction of several groups of ore bodies with differing trace element levels. Within groups, certain elements show lateral or vertical zoning. The groups were deposited from different batches of ore fluid. The differences in trace element content between groups reflect differences in stage of differentiation or abundance of complexing species when the ore fluid separated from the magma. The zoning may result from hydrothermal differentiation of a single batch of ore fluid as it travels away from the magma. The zoning pattern correlates in part with expected strength of metal complexes, but also depends on temperature and solid-liquid partition coefficients.

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Zusammenfassung Auf Grund der Spurenelementhäufigkeiten in Sulfiden können in diesen beiden großen hydrothermalen Erzvorkommen mehrere Gruppen von Erzlagerstätten unterschieden werden. Innerhalb der Gruppen zeigen gewisse Elemente laterale oder vertikale zonale Verteilungen. Die Gruppen wurden von verschiedenen erzbringenden Lösungen gebildet. Die Unterschiede im Spurenelementgehalt zwischen verschiedenen Gruppen spiegeln Unterschiede im Stadium der Differentiation oder die Häufigkeit von komplexbildenden Ionen während der Absonderung der erzbringenden Lösungen von Magma wider. Die zonale Verteilung kann von der hydrothermalen Differentiation einer einzigen erzbringenden Lösung auf ihrem Weg vom Magma herrühren. Teilweise entspricht die zonale Spurenelementverteilung der erwarteten Stabilität von Metalionenkomplexen, sie hängt aber auch von der Temperatur und von Verteilungskoeffizienten zwischen festen und flüssigen Phasen ab.

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Contribution No. 69–34, College of Earth and Mineral Sciences, The Pennsylvania State University     

A study of the geophysical response of distributed fibre optic acoustic sensors through laboratory‐scale experiments

In the past few years, distributed acoustic sensing has gained great interest in geophysics. This acquisition technology offers immense improvement in terms of efficiency when compared with current geophysical acquisition methods. However, the fundamentals of the measurement are still not fully understood because direct comparisons of fibre data with conventional geophysical sensors are difficult during field tests. We present downscaled laboratory experiments that enabled us to characterise the relationship between the signals recorded by conventional seismic point receivers and by distributed fibre optic sensors. Interrogation of the distributed optical fibre sensor was performed with a Michelson interferometer because this system is suited to compact test configurations, and it requires only a very simple data processing workflow for extracting the signal outputs. We show acoustic data that were recorded simultaneously by both the fibre optical interferometer and conventional three‐component accelerometers, thus enabling the comparison of sensor performance. We present results focused on the directionality of fibre measurements, on the amplitude variation with angle of incidence, and on the transfer function that allows accelerometer signals to be transformed into optical fibre signals. We conclude that the optical fibre response matches with the array of the displacement differences of the inline accelerometers deployed along the fibre length. Moreover, we also analysed the influence of various types of coupling and fibre cable coating on the signal responses, emphasising the importance of these parameters for field seismic acquisitions when using the distributed fibre optic technology.     

The Néel transition and magnetic properties of terrestrial,synthetic, and lunar ilmenites

The magnetic susceptibility of a terrestrial, synthetic and lunar ilmenite specimen has been measured from 4 to 300 K. All specimens had a single Néel temperature transition which ranged from 56 to 57.7 K. In one case the powdered specimen was partially aligned in the magnetic field prior to the susceptibility measurements and the Néel transition was observed to shift to 60 K indicating magnetic anisotropy. A study of several magnetic parameters calculated from the experimental data showed gross impurities in the terrestrial specimen, single-domain to multi-domain metallic iron in the synthetic specimen, and a small amount of superparamagnetic metallic iron in the lunar sample. No multidomain iron was observed in the lunar ilmenite. The results of electron spin resonance measurements were also in general agreement with these findings. Because of the absence of Fe³⁺ compared to most terrestrial samples it is suggested that the anisotropic magnetic parameters be determined on lunar ilmenite when a large enough single crystal becomes available.     

Acidification and Trace Metals of Lakes in Taiwan

One hundred and eighty lakes, ponds and reservoirs in Taiwan, and the offshore islands have been investigated since 1985. Effects such as warming/cooling, mixing, photosynthesis and respiration on pH have been identified. These effects were found to be less profound than those resulting from the geology. Since there is little rain or lake water pH data available prior to 1970, it was necessary to use proxy data in order to ascertain the history of lake acidification. In this study, we present data based on diatoms in a sediment core collected from a lake in the remote subalpine region of southern Taiwan. The acidity of this lake water was found to have increased since 1900. We measured the concentrations of 55 chemical species in lake water samples. In addition, concentrations of 26 chemical species were obtained from sediments. Conductivity, alkalinity (HCO₃ ^?), most other major and minor chemical species, as well as the non sea-salt SO₄/Na ratio in lake water clearly decrease with elevation. Distribution of pH is similar, although the trend is less clear. Distribution of trace metals, however, shows a different trend as anthropogenic pollution, diagenetic reduction and lake acidification are at play.     

Distribution and mode of occurrence of zinc and lead in glacial soils

The distribution and mode of occurrence of zinc and lead have been examined in glacial soils developed over a complex Precambrian marble-paragneiss terrain in the Adirondack Mountains of New York. Based on distribution within the soil profiles, zinc is enriched in the B₁ horizon of soils sampled over marble and lead is generally enriched in the A horizon, particularly in soils developed over paragneiss. Contrast is calculated using

Full-size image (1K)

, where is the mean of n_A anomalous and n_B background samples, and S_p is the pooled standard deviation) for zinc, lead and cold-extractable heavy metals in soils sampled over marble and paragneiss. The t-values indicate that the B₁, soil horizon is the most suitable for sampling on a regular basis, even though lead is most concentrated in the A horizon.The distribution of zinc and lead among exchangeable, organic, iron-manganese oxide, clay, silt and sand fractions of B₁ horizons from two anomalous and one background soil indicates that both zinc and lead are tied up principally in iron and manganese oxides. The anomalous samples exhibit zinc enrichment in the Fe-oxide digestion and high Mn/Fe ratios for the Mn-oxide digestion (as well as the total analysis). In terms of total contribution to the sample, significant proportions of zinc in the clastic fraction can be attributed to zinc substitution into clays plus the ineffective removal of Fe-oxides by the ammonium oxalate extraction procedure. Lead, on the other hand, occurs in significant concentrations in clay, silt and sand as well as Fe- and Mn-oxides, probably as a trace constituent in feldspars or adsorbed onto clay surfaces.     

Atmospheric tracer monitoring and surface plume development at the ZERT pilot test in Bozeman,Montana, USA

A controlled release of CO₂ was conducted at a field site in Bozeman, Montana, USA in July of 2008 in a multi-laboratory study of near surface transport and detection technologies. The development of a subsurface CO₂ plume near the middle packer section of the horizontal release was studied using soil-gas and surface flux measurements of CO₂. A perfluorocarbon tracer was added to the CO₂ released from this section of the horizontal well, and the development of atmospheric plumes of the tracer was studied under various meteorological conditions using horizontal and vertical grids of monitors containing sorbent material to collect the tracer. This study demonstrated the feasibility of using remote sensing for the ultra low level detection of atmospheric plumes of tracers as means to monitor the near surface leakage of sequestered CO₂.     

Factors influencing the stability of smectite sealants

Smectite is a mineral, but a mineral with distinct chemical properties. Structural changes in minerals may require millions of years of aging to complete, but a chemical reaction may be completed in only 4 to 5 min.

Some of the problems of smectite seals are described in this paper, together with methods of avoiding these hazards.     

A comprehensive survey of lignin geochemistry in the sedimentary organic matter along the Kapuas River (West Kalimantan, Indonesia)

In this first study of lignin geochemistry in the world’s longest river on an island, surface sediments were collected along the Kapuas River, three lakes in the upper river, a tributary in the lower river and a separate river during June-July 2007 and December 2007-January 2008. The samples were analyzed for lignin-derived phenols and bulk elemental and stable carbon isotope compositions. Λ values (the sum of eight lignin phenols, expressed as mg/100 mg organic carbon (OC)) ranged from 0.13 to 3.70. Ratios of syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) ranged from 0.34 to 1.18 and 0.28 to 1.40, respectively, indicating the presence of non-woody angiosperm tissues. The high vanillic acid to vanillin (Ad/Al)v (0.71-2.01) and syringic acid to syringaldehyde (Ad/Al)s (0.72-2.12) ratios indicate highly degraded lignin materials. In the upper Kapuas River, highly degraded soil materials discharged from lands that were barren as a result of deforestation activities were detected in the locations directly in those vicinities. The middle Kapuas River showed rapid organic matter degradation, probably due to the presence of fresh terrestrial and phytoplankton organic matter fueling the biogeochemical cycling. The Kapuas Kecil River, one of the two branches in the lower reach of the Kapuas River, showed higher levels and diagenesis of sedimentary organic matter due to input from anthropogenic sources and increased marine organic matter near the mouth. This study shows that different stretches along the river exhibit different levels and composition of sedimentary organic matter, as well as different carbon dynamics, which is directly attributable to the varying landscapes and quality of organic matter.     

Pore to pore validation of pore network modelling against micromodel experiment results

Pore network modelling (PNM) has been widely used to study the multiphase flow and transport in porous media. Although a number of recent papers discussed the PNM validation on core-scale parameters such as permeability, relative permeability and capillary pressure; quantitative predictive potential of PNM on pore by pore basis has rarely been studied. The aim of this paper is to present a direct comparison between PNM simulations and corresponding micro-model experiments at the same scale and the same geometry. A number of well-defined and constrained two-phase flow in porous medium experimental scenarios were utilized to validate the physics solving part in PNM (filling rules, capillary and viscous pressure). This work validates that a dynamic pore network flow solver can predict two-phase flow displacements for these experiments for drainage situations at both pore and plug scales. A glass-etched micro-model is used to quantify the accuracy of a dynamic PNM solver on pore and core levels. Two-phase drainage micro fluidic experiments at different flow conditions are performed on micro-models. PNM simulations are performed on the same pattern and flow conditions as used in micro-model experiments. The two-phase distribution extracted from experiment images is registered onto rsults of PNM simulations for direct pore to pore comparison. Pore-scale matching level is found at around 75 % for all three test cases. The matching level of core-scale parameters such as S _{w c} and oil-phase permeability varies from case to case; the relative error to micro-model experiment measurements varies from 15 to 60 %. Possible reasons leading to discrepancies on core-scale parameters are discussed: missing considerations during validation of the combination of uncertainty in both simulator input parameters and experiments are seen as the principal factors.     

Clay mineralogical,geochemical and isotopic tracing of the evolution of the Woodleigh impact structure,Southern Carnarvon Basin,Western Australia

Chaotically structured diamictite from the inner ring syncline surrounding the central uplift of the Woodleigh impact structure contains shocked metamorphic and impact melt-rock fragments, largely derived from Ordovician and Devonian target sandstones. Coarse illite fractions (<2 m) from the sandstones containing no K-feldspar yield K–Ar ages of around 400 Ma, whereas the K–Ar ages of authigenic clays of >0.2 m fractions from the diamictite without smectite and K-feldspar cluster around 360 Ma, consistent with Rb–Sr data. Crystallisation of newly formed illite in the impact melt rock clasts and recrystallisation of earlier formed illite in the sandstone clasts preserved in the diamictite, are attributed to impact-induced hydrothermal processes in the Late Devonian. The illitic clays from the diamictite and from the sandstones have very similar trace element compositions, with significantly enriched incompatible lithophile elements, which increase in concentrations correlatively with those of the compatible ferromagnesian elements. The unusual trace element associations in the clays may be due to the involvement of hot gravity-driven basinal fluids that interacted with rocks of the Precambrian craton to the east of the study area, or with such material transported and reworked in the studied sedimentary succession.