美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带(续)          下载免费PDF全文

Stephen G. Peters  Gregory C. Ferdock  Maria B. Woitsekhowskay  Robert Leonardson  Jerry Rahn 《地质找矿论丛》2000,15(2):115-132

(接第 1期第 1 6页 )3　富矿分带与控制因素贝茨金矿中不同矿石矿物组合和蚀变类型的分布与构造背景、围岩岩石及在矿体中的位置有关。根据形态、矿物组成和地质背景可分出几种空间形式截然不同的矿石类型 ,彼此之间由废石或低含金量的岩石所分隔。富矿体的地球化学、矿物学、地质及冶金方面的分带在三维空间上是连续的。富矿体的形状和定位与 Peters向斜构造的特征 ,沉积岩的岩石组成以及闪长岩接触带的几何形态和厚度有关 (图 6 A,B)。根据对不同的矿石类型和围岩类型的研究结果 ,对不同的富矿体进行了分类和判别。 Pe-ters( 1 996 ,1 9…  相似文献   

Development of hepatic CYP1A and blood vitellogenin in eel (Anguilla anguilla) for use as biomarkers in the Thames Estuary, UK.   总被引：1，自引：0，他引：1  

D R Livingstone  C L Mitchelmore  L D Peters  S C O'Hara  J P Shaw  B S Chesman  A Doyotte  J McEvoy  D Ronisz  D G Larsson  L F?rlin 《Marine environmental research》2000,50(1-5):367-371

The potential of eel (Anguilla anguilla) as a monitoring species for the Thames Estuary, UK, was examined. Hepatic cytochrome P4501A [7-ethoxyresorufin O-deethylase (EROD) activity] and blood vitellogenin (Western analysis) were investigated as biomarkers of exposure to, respectively, organic contaminants and to contaminants showing estrogenic activity. Hepatic microsomal EROD activities in A. anguilla from seven sites in the Thames Estuary in May 1998 varied three-fold (111 +/- 24 to 355 +/- 42 pmol min-1 mg protein-1) (mean +/- S.E.M.) and showed correlation with salinity; however, the latter relationship was not maintained at other times of the year. The range of EROD activities was two- to eight-fold higher than the 37 +/- 8 pmol min-1 mg-1 for A. anguilla from the relatively clean Tamar Estuary. beta-Naphthoflavone treatment (5 mg kg-1 wet wt.; 2 days) of Thames A. anguilla produced a two-fold increase in hepatic microsomal EROD activity. Comparing the Thames EROD data with those for A. anguilla from well-characterised contaminated sites in the Netherlands (Van der Oost, R., Goks?yr, A., Celander, M., Heida, H., & Vermeulen, N. P. E. 1996. Aquatic Toxicology, 36, 189-222), the Thames is suggested to be moderately impacted by polycyclic aromatic hydrocarbons and related contaminants. 17-beta-Estradiol treatment produced the appearance of a plasma protein of 211 Kd app. mol. wt. (recognised by antibodies to vitellogenin of Morone saxatilis), but putative vitellogenin could not be detected in A. anguilla from selected sites in the Thames Estuary.  相似文献   

Investigations into an unknown organism on the martian meteorite Allan Hills 84001     

Andrew Steele  David t. Goddard  Dave Stapleton  Jan k. w. Toporski  Vanessa Peters  Virginia Bassinger  George Sharples  David d. Wynn‐Williams  David s. Mckay 《Meteoritics & planetary science》2000,35(2):237-241

Abstract— Examination of fracture surfaces near the fusion crust of the martian meteorite Allan Hills (ALH) 84001 have been conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and has revealed structures strongly resembling mycelium. These structures were compared with similar structures found in Antarctic cryptoendolithic communities. On morphology alone, we conclude that these features are not only terrestrial in origin but probably belong to a member of the Actinomycetales, which we consider was introduced during the Antarctic residency of this meteorite. If true, this is the first documented account of terrestrial microbial activity within a meteorite from the Antarctic blue ice fields. These structures, however, do not bear any resemblance to those postulated to be martian biota, although they are a probable source of the organic contaminants previously reported in this meteorite.  相似文献   

Hydrothermalism in the Tyrrhenian Sea: Inorganic and microbial sulfur cycling as revealed by geochemical and multiple sulfur isotope data     

Marc Peters  Harald Strauss  Sven Petersen  Nicolai-Alexeji Kummer  Christophe Thomazo 《Chemical Geology》2011,280(1-2):217-231

The Palinuro volcanic complex and the Panarea hydrothermal field, both located in the Tyrrhenian Sea (Italy), are associated with island arc magmatism and characterized by polymetallic sulfide mineralization. Dissolved sulfide concentrations, pH, and Eh measured in porewaters at both sites reveal a variable hydrothermal influence on porewater chemistry.Multiple sulfur isotopic measurements for disseminated sulfides (CRS: chromium reducible sulfur) extracted from sediments at Palinuro yielded a broad range in δ³⁴S range between ?29.8 and + 10.2‰ and Δ³³S values between + 0.015 and + 0.134‰. In contrast, sediments at Panarea exhibit a much smaller range in δ³⁴S_CRS with less negative values between ?11.3 and ?1.8‰. The sulfur isotope signatures are interpreted to reflect a mixture between hydrothermal and biogenic sulfide, with a more substantial biogenic contribution at Panarea.Multiple sulfur isotope measurements were performed on sulfides and elemental sulfur from drill core material from the Palinuro massive sulfide complex. δ³⁴S and Δ³³S values for pyrite between ?32.8 and ?1.1‰ and between ?0.012 to + 0.042‰, respectively, as well as for elemental sulfur with δ³⁴S and Δ³³S values between ?26.7 and ?2.1‰ and between + 0.035 and + 0.109‰, respectively, point to a microbial origin for much of the sulfide and elemental sulfur studied. Moreover, data suggest a coupling of bacterial sulfate reduction, sulfide oxidation and sulfur disproportionation. In addition, δ³⁴S values for barite between + 25.0 and + 63.6‰ are also in agreement with high microbial turnover of sulfate at Palinuro.Although a magmatic SO₂ contribution towards the formation of the Palinuro massive sulfide complex is very likely, the activity of different sulfur utilizing microorganisms played a fundamental role during its formation. Thus, porewater and multiple sulfur isotope data reveal differences in the hydrothermal activity at Palinuro and Panarea drill sites and underline the importance of microbial communities for the origin of massive sulfide mineralizations in the hydrothermal subsurface.  相似文献   

Coastal Mediterranean plankton stimulation dynamics through a dust storm event: An experimental simulation     

Estela Romero  Francesc Peters  Cèlia Marrasé  Òscar Guadayol  Josep M. Gasol  Markus G. Weinbauer 《Estuarine, Coastal and Shelf Science》2011

An enhancement of aeolian inputs to the ocean due to a future increase in aridity in certain parts of the world is predicted from global change. We conducted an experimental simulation to assess the biological response of NW Mediterranean coastal surface waters to an episodic dust addition. On the assumption that planktonic growth was limited by phosphorus, dust effects were compared to those induced by equivalent enrichments of phosphate. The experiment analyzed the dynamics of several parameters during one week: inorganic nutrients, total and fractioned chlorophyll a, bacterial abundance, phytoplankton species composition, abundance of autotrophic and heterotrophic flagellates, particulate organic carbon and particulate organic nitrogen. The maximum addition of dust (0.5 g dust L⁻¹) initiated an increase in bacterial abundance. After 48 h, bacterial numbers decreased due to a peak in heterotrophic flagellates and a significant growth of autotrophic organisms, mainly nanoflagellates but also diatoms, was observed. Conversely, lower inputs of dust (0.05 g dust L⁻¹) and phosphate enrichments (0.5 μmol PO₄³⁻ L⁻¹) only produced increases in phototrophic nanoflagellates. In our experiment, dust triggered bacterial growth, changed phytoplankton dynamics and affected the ratio of autotrophic to heterotrophic biomass, adding to the variability in the sources that affect system dynamics, energy and carbon budgets and ultimately higher trophic levels of the coastal marine food web.  相似文献   

Topographic control on the nascent Mediterranean outflow   总被引：1，自引：1，他引：0  

M. Gasser  J. L. Pelegr��  J. D. Nash  H. Peters  J. Garc��a-Lafuente 《Geo-Marine Letters》2011,31(5-6):301-314

Data collected during a 12-day cruise in July 2009 served to examine the structure of the nascent Mediterranean Outflow Water (MOW) immediately west of the Espartel Sill, the westernmost sill in the Strait of Gibraltar. The MOW is characterized by high salinities (>37.0 and reaching 38.3) and high velocities (exceeding 1?m s^?1 at 100?m above the seafloor), and follows a submerged valley along a 30?km stretch, the natural western extension of the strait. It is approx. 150?m thick and 10?km wide, and experiences a substantial drop from 420 to 530?m over a distance of some 3?km between two relatively flat regions. Measurements indicate that the nascent MOW behaves as a gravity current with nearly maximal traveling speed; if this condition is maintained, then the maximum MOW velocity would decrease slowly with distance from the Espartel Sill, remaining significantly high until the gravity current excess density is only a small fraction of its original value. The sharp pycnocline between the Mediterranean and the overlying North Atlantic Central waters is dynamically unstable, particularly where the flow interacts with the 100?m decrease in bottom depth. Here, subcritical gradient Richardson numbers coincide with the development of large interfacial undulations and billows. The very energetic downslope flow is likely responsible for the development of a narrow V-shaped channel downstream of the seafloor drop along the axis of the submerged valley, this probably being the very first erosional scour produced by the nascent MOW. The coincidence of subcritical gradient Richardson numbers with relatively high turbidity values above the channel flanks suggests it may be undergoing upstream erosion.  相似文献   

An endochronic plasticity theory with shear-volumetric coupling     

K. C. Valanis  J. F. Peters 《国际地质力学数值与分析法杂志》1991,15(2):77-102

Thermodynamic and physical principles are applied in conjunction with the concepts of endochronic plasticity to develop a theory of constitutive behaviour of soils with dilatant capability. Three separate constitutive models are derived within the framework of the proposed theory, all capable of accounting for shear–volume coupling of soil within the context of endochronic plasticity. One specific model is singled out as the most appropriate on the basis of its analytical simplicity and the plausibility of its thermodynamic and physical foundations. A simple example is worked out for the purposes of illustration.  相似文献   

IAVCEI news     

H-U Schmincke  RW Johnson 《Bulletin of Volcanology》1991,53(8):647-648

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Mooring developments for autonomous ocean-sampling networks     

Frye  D.E. Kemp  J. Paul  W. Peters  D. 《Oceanic Engineering, IEEE Journal of》2001,26(4):477-486

Two general-purpose mooring designs have been developed to support autonomous underwater vehicle (AUV) operations in autonomous ocean sampling networks (AOSNs). These moorings provide two-way communications between investigators and AUVs docked on the moorings or conducting survey operations some distance from the moorings. A deep-water design that incorporates an AUV dock and recharging station was built for use in the Labrador Sea during the winter of 1997/1998. This severe winter environment required a robust design that could operate unattended for six months while isolating the dock from surface wave motion. A much lighter, easier-to-deploy design was developed for use in coastal waters to extend the nearshore AOSN operating area by extending the communications network. This coastal design has been deployed without the dock component and has typically been configured for use in a small network of moorings maintained with a small research vessel. The deep-water mooring has been deployed successfully on two occasions, for short periods of time. The coastal moorings have been deployed a number of times and have proven to be quite effective. This paper describes the two moorings in detail and provides information on their performance so that interested investigators can utilize the technology where it meets their needs  相似文献   

Very high-frequency radar mapping of surface currents     

Shay  L.K. Cook  T.M. Peters  H. Mariano  A.J. Weisberg  R. An  P.E. Soloviev  A. Luther  M. 《Oceanic Engineering, IEEE Journal of》2002,27(2):155-169

An ocean surface current radar (OSCR) in the very high frequency (VHF) mode was deployed in South Florida Ocean Measurement Center (SFOMC) during the summer of 1999. During this period, a 29-d continuous time series of vector surface currents was acquired starting on 9 July 1999 and ending 7 August 1999. Over a 20-min sample interval, the VHF radar mapped coastal ocean currents over a 7.5 km × 8 km domain with a horizontal resolution of 250 m at 700 grid points. A total of 2078 snapshots of the two-dimensional current vectors were acquired during this time series and of these samples, only 69 samples (3.3%) were missing from the time series. During this period, complex surface circulation patterns were observed that included coherent, submesoscale vortices with diameters of 2 to 3 km inshore of the Florida Current. Comparisons to subsurface measurements from moored and ship-board acoustic Doppler current profiles revealed regression slopes of close to unity with biases ranging from 4 to 8 cm s^-1 between surface and subsurface measurements at 3 to 4 m beneath the surface. Correlation coefficients were 0.8 or above with phases of - 10 to - 20° suggestive of an anticyclonic veering of current with depth relative to the surface current. The radar-derived surface current field provided spatial context for an observational network using mooring-, ship- and autonomous underwater vehicle-sensor packages that were deployed at the SFOMC  相似文献