Different levels of mussel (Mytilus edulis) DNA strand breaks following chronic field and acute laboratory exposure to polycyclic aromatic hydrocarbons   总被引：1，自引：0，他引：1  

Large AT  Shaw JP  Peters LD  McIntosh AD  Webster L  Mally A  Chipman JK 《Marine environmental research》2002,54(3-5):493-497

Levels of polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene (B[a]P) were at least seven-fold higher in mussels sampled from a polluted site (Loch Leven, in Scotland, UK) compared to a nearby clean reference site (Loch Etive) throughout the year 2000. Levels of DNA strand breaks (alkaline COMET assay) using both gill and digestive gland nuclei were similar at both sites despite the difference in contaminant load (total PAH). In contrast, mussels collected from a reference site (Port Quin, Cornwall, UK) had an increase in DNA strand breaks in digestive gland cells following laboratory exposure to B[a]P-dosed Isochrysis galbana. However, after 14 days high dose (20 ppb-exposed diet) animals had returned to levels similar to the controls. There was no evidence of increased necrosis or apoptosis after treatments. The results from these two studies suggest that an adaptive response may prevent ongoing DNA damage in mussels exposed to high levels of B[a]P and PAH contamination.  相似文献   

Use of a multiplicative model to estimate relative abundance from commercial CPUE data   总被引：1，自引：3，他引：1  

Large  P. A. 《ICES Journal of Marine Science》1992,49(3):253-262

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Age and pyrite Pb-isotopic composition of the giant Sukhoi Log sediment-hosted gold deposit, Russia   总被引：2，自引：0，他引：2  

Sebastien Meffre  Ross R. Large  Jon Woodhead  Sarah E. Gilbert  Valeriy Maslennikov 《Geochimica et cosmochimica acta》2008,72(9):2377-2391

Sukhoi Log is one of the largest gold deposits in Russia (1100 t Au at 2.45 g/t). Like many other sediment-hosted gold deposits throughout the world, Sukhoi Log preserves textural, structural and geochemical evidence for multiple generations of Au enrichment and pyrite growth.The deposit is located in the Lena gold province of Siberia, on the edge of the Siberian Craton and occurs in the core of a recumbent anticline in a Neoproterozoic black shale and quartz-rich siltstone-sandstone turbidite succession. Temporal constraints on pyrite paragenesis at the deposit have been determined using laser ablation inductively coupled mass spectrometry (LA-ICPMS) measurements of U, Th and Pb isotopes in pyrite, monazite and zircon. LA-ICPMS age determinations on detrital zircons indicate the host rocks were deposited after 600 ± 10 Ma and derived from a mixture of Palaeoproterozoic and Neoproterozoic sources. The U, Th and Pb isotopic systematics indicate the cores of large monazite crystals, which predate obvious tectonic fabric development in the host rocks, began growing at 573 ± 12 Ma. The rims of the same monazite crystals formed at 516 ± 10 Ma, during peak metamorphism and deformation. Small monazite crystals also grew in the sedimentary rocks during the Devonian (374 ± 20 Ma) and the Carboniferous or Early Permian (288 ± 22 Ma), possibly in response to fluid movements triggered by synchronous granite intrusion in the area. Multi-collector and quadrupole LA-ICPMS Pb isotopic determination on pyrite, combined with overprinting criteria, show that the earliest (stratiform) Pb and Au-bearing pyrite formed prior to metamorphism—possibly during sedimentation or early diagenesis (575-600 Ma). Small Au-rich pyrite nodules preserved as cores to folded bedding-parallel pyrite-quartz veins probably grew during late diagenesis or early metamorphism. Large pyrite euhedra, which overgrow the strong axial planar cleavage in the host rocks, have more radiogenic Pb-isotopic compositions and formed either late during or after deformation. Framboidal pyrite that is overgrown by both the late diagenetic-early metamorphic and syn- to post-metamorphic pyrite has the most radiogenic Pb-isotopic composition suggesting exchange with radiogenic Pb in the matrix may have continued until late in the history of the deposit.The dating and Pb isotopes support a multistage origin for the gold deposit with Au first introduced during or prior to growth of the earliest stratiform pyrite and progressively re-concentrated (with or without addition of further gold) during later metamorphic events.  相似文献   

New insights into the genesis of volcanic-hosted massive sulfide deposits on the seafloor from numerical modeling studies   总被引：2，自引：0，他引：2  

Christian Schardt  Ross R. Large 《Ore Geology Reviews》2009,35(3-4):333-351

Numerical computer simulations have been used to gain insight into the evolution of marine hydrothermal systems and the formation conditions of massive sulfide deposits in ancient and modern submarine volcanic terrains. Simulation results have been used to gain a better understanding of the formation of massive sulfide ore deposits, their location, zonation, size, and occurrence in various geotectonic settings.Most hydrothermal fluid discharging at the seafloor exhibits temperatures ranging from 200 °C to about 410 °C and average fluid discharge velocities of 1 to 2 m/s in agreement with seafloor observations. Mass calculations imply that average massive sulfide deposits may form in ~ 5000 years while giant deposits take longer than 5000 years to accumulate; supergiant deposits either need much longer time to form (> 35,000 years) or at least 100 ppm of metal in solution. Results indicate that supergiant deposits may only form in certain geotectonic environments where longevity and preservation potential of the hydrothermal system are high. An additional process (mineral precipitate cap) is proposed here to explain the zinc content of massive sulfide deposits. This cap would prevent the widespread dissolution of anhydrite and the ‘wash-out’ of zinc by subsequent hydrothermal fluid discharge.  相似文献   

Permo–Triassic unconformity-related Au-Pd mineralisation, South Devon, UK: new insights and the European perspective     

Tom J. Shepherd  Jon E. Bouch  Andrew G. Gunn  John A. McKervey  Jonathan Naden  Richard C. Scrivener  Michael T. Styles  Duncan E. Large 《Mineralium Deposita》2005,40(1):24-44

An integrated mineralogical-geochemical study of unconformity-related Au-Pd occurrences within and around the Permo–Triassic basins of southwest England, UK, has confirmed the importance of low temperature (86±13°C), hydrothermal carbonate veins as hosts for the mineralisation. Fluid inclusion data for the carbonate gangue, supported by stable isotope (¹³C and ¹⁸O) and radiogenic (⁸⁷Sr/⁸⁶Sr) data, have identified three principal fluids: (1) a reducing calcic brine [>25 wt% salinity, <0.5 NaCl/(NaCl+CaCl₂)] originating in the sub-unconformity basement and an expression of advanced mineral–fluid interaction; (2) an oxidising sodic brine [~16 wt% salinity, >0.9 NaCl/(NaCl+CaCl₂)] originating in the post-unconformity red beds under evaporitic conditions, and (3) an oxygenated, low salinity groundwater (<3 wt% salinity). The sodic brine is reasoned to be the parent metalliferous fluid and to have acquired its enrichment in Au and Pd by the leaching of immature sediments and intra-rift volcanic rocks within the local Permo–Triassic basins. Metal precipitation is linked to the destabilisation of Au and Pd chloride complexes by either mixing with calcic brines, dilution by groundwaters or interaction with reduced lithologies. This explains the diversity of mineralised settings below and above the unconformity and their affinity with red bed brines. The paucity of sulphide minerals, the development of selenides (as ore minerals and as mineral inclusion in gold grains), the presence of rhodochrosite and manganoan calcites (up to 2.5 wt% Mn in calcite) and the co-precipitation of hematite and manganese oxides are consistent with the overall high oxidation state of the ore fluids. A genetic model is proposed linking Permo–Triassic red beds, the mixing of oxidising and reducing brines, and the development of unconformity-related precious metal mineralisation. Comparison with other European Permo–Triassic basins reveals striking similarities in geological setting, mineralogy and geochemistry with Au, Au-Pd and selenide occurrences in Germany (Tilkerode, Korbach-Goldhausen), Poland (Lubin) and the Czech Republic (Svoboda nad Úpou and Stupná). Though the known Au-Pd occurrences are sub-economic, several predictive criteria are proposed for further exploration.Editorial handling: B. Lehmann  相似文献   

Book review     

D. Large 《Mineralium Deposita》1988,23(3):190-173

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Influence of survey strategy and interpolation model on DEM quality   总被引：2，自引：0，他引：2  

George L. Heritage  David J. Milan  Andrew R.G. Large  Ian C. Fuller 《Geomorphology》2009,112(3-4):334-344

Accurate characterisation of morphology is critical to many studies in the field of geomorphology, particularly those dealing with changes over time. Digital elevation models (DEMs) are commonly used to represent morphology in three dimensions. The quality of the DEM is largely a function of the accuracy of individual survey points, field survey strategy, and the method of interpolation. Recommendations concerning field survey strategy and appropriate methods of interpolation are currently lacking. Furthermore, the majority of studies to date consider error to be uniform across a surface. This study quantifies survey strategy and interpolation error for a gravel bar on the River Nent, Blagill, Cumbria, UK. Five sampling strategies were compared: (i) cross section; (ii) bar outline only; (iii) bar and chute outline; (iv) bar and chute outline with spot heights; and (v) aerial LiDAR equivalent, derived from degraded terrestrial laser scan (TLS) data. Digital Elevation Models were then produced using five different common interpolation algorithms. Each resultant DEM was differentiated from a terrestrial laser scan of the gravel bar surface in order to define the spatial distribution of vertical and volumetric error. Overall triangulation with linear interpolation (TIN) or point kriging appeared to provide the best interpolators for the bar surface. Lowest error on average was found for the simulated aerial LiDAR survey strategy, regardless of interpolation technique. However, comparably low errors were also found for the bar-chute-spot sampling strategy when TINs or point kriging was used as the interpolator. The magnitude of the errors between survey strategy exceeded those found between interpolation technique for a specific survey strategy. Strong relationships between local surface topographic variation (as defined by the standard deviation of vertical elevations in a 0.2-m diameter moving window), and DEM errors were also found, with much greater errors found at slope breaks such as bank edges. A series of curves are presented that demonstrate these relationships for each interpolation and survey strategy. The simulated aerial LiDAR data set displayed the lowest errors across the flatter surfaces; however, sharp slope breaks are better modelled by the morphologically based survey strategy. The curves presented have general application to spatially distributed data of river beds and may be applied to standard deviation grids to predict spatial error within a surface, depending upon sampling strategy and interpolation algorithm.  相似文献   

Design,calibration and geological application of the first operational Australian laser ablation sulphur isotope microprobe     

D. L. Huston  M. Power  J. B. Gemmell  R. R. Large 《Australian Journal of Earth Sciences》2013,60(6):549-555

This contribution describes the setup and operating procedures of the first operational laser ablation microprobe for stable (sulphur) isotope analysis in Australia as well as some brief geological applications. A significant feature on this laser ablation microprobe is automated gas purification and analysis; operator control is only required to locate and ablate sample targets. As with other laboratories, samples were ablated in an oxygen atmosphere, producing a SO₂/O₂ gas mixture. SO₂ was separated from this mixture by either of two techniques. In the first technique, SO₂ was condensed into a liquid N₂ trap by cryogenic pumping, and O₂ was pumped away. This resulted in the collection of 60–70% of the produced SO₂. In the second technique, SO₂ was condensed into a liquid N₂ trap as the SO₂/O₂ mixture was slowly bled away. This technique collected 90–95% of the SO₂, with a small fractionation of 0.16%. Laser ablation and SO₂ collection via the second technique required a mineral dependent, additive correction of 2.85–5.75% to convert raw δ³⁴S values to δ³⁴S_CDT. These correction factors are mineral and laboratory dependent, and from our data, seem to be dependent on the quality of polish of the ablated sample. Precision (1σ) of laser ablation sulphur isotope analysis is 0.4–0.5%o for 150 μm ablation craters.

Preliminary results of studies on samples from the Broken Hill, Hellyer and active sea floor Pacmanus deposits indicate that laser ablation microprobe analysis can show subtle variations in δ³⁴S not apparent using either conventional or SHRIMP analysis. Laser ablation analysis indicates a larger range, but similar mean values, to conventional analysis on the same samples.  相似文献   

The influence of climate,hydrology and permafrost on Holocene peat accumulation at 3500 m on the eastern Qinghai–Tibetan Plateau     

David J. Large  Baruch Spiro  Marion Ferrat  Michaela Shopland  Malin Kylander  Kerry Gallagher  Xiangdong Li  Chengde Shen  Goran Possnert  Gan Zhang  W. George Darling  Dominik Weiss 《Quaternary Science Reviews》2009,28(27-28):3303-3314

Peatland of the eastern Qinghai–Tibetan Plateau lies at the convergence of the East Asian and Indian monsoon systems in eastern Asia. To understand the evolution of this peatland and its potential to provide new insights into the Holocene evolution of the East Asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near Hongyuan. The age-depth profile was determined using 16 ¹⁴C-AMS age dates, the peat analysed for a range of environmental variables including carbon, nitrogen and hydrogen concentration, bulk density, δ¹³C and the associated spring water analysed for hydrogen and oxygen isotopes. The age-depth profile of the recovered peat sequence covers the period from 9.6 to 0.3 kyr BP and is linear indicating that the conditions governing productivity and decay varied little over the Holocene. Using changes in carbon density, organic carbon content and its δ¹³C, cold dry periods of permafrost characterised by low density and impeded surface drainage were identified. The low δ¹⁸O and δD values of the spring water emanating around the peat deposit, down to ?13.8 and ?102‰ (VSMOW), respectively, with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day. In view of the current annual mean air temperature of 1 °C this suggests conditions in the past have been conducive to permafrost. Inferred periods of permafrost correspond to independently recognised cold periods in other Holocene records from across China at 8.6, 8.2–7.8, 5.6–4.2, 3.1 and 1.8–1.5 kyr BP. The transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at Hongyuan are of longer duration than equivalent cold dry periods over central and eastern China. Light–dark banding peat on a scale of 15–30 years from 9.6 to 5.5 kyr BP may indicate a strong influence of decadal oscillations possibly the Pacific Decadal Oscillation and a potential link between near simultaneous climatic changes in the northwest Pacific, ENSO, movement of the Intertropical Convergence Zone and the East Asian Monsoon.  相似文献   

Se and In minerals in the submarine oxidation zone of a massive sulfide orebody of the molodezhnoe copper–zinc massive sulfide deposit,Southern Urals     

N. R. Ayupova  V. V. Maslennikov  V. A. Kotlyarov  S. P. Maslennikova  L. V. Danyushevsky  R. Large 《Doklady Earth Sciences》2017,473(1):318-322

For the first time, extremely high Se and In contents were determined for the pinches of massive sulfide orebodies that are composed of small-clastic layered sulfide sediments transformed during submarine supergenesis. Se (clausthalite and naumannite) and In (roquesite) minerals were found. Hydrothermal chalcopyrite, a significant amount of which is present in the clasts of paleohydrothermal black smoker chimneys, was the source of Se. Most of the amount of In was contributed during dissolution of clasts of hydrothermal sphalerite, which is unstable in the submarine oxidation zone in the presence of oxidized pyrite.  相似文献