Brine-pool deposition for the Zn–Pb–Cu massive sulphide deposits of the Bathurst mining camp, New Brunswick, Canada. II. Ocean anoxia during mineralisation     

Mike Solomon   《Ore Geology Reviews》2008,33(3-4):352-360

Current models of massive sulphide ore genesis in the Bathurst mining camp, New Brunswick, involve settling of sulphide particles from a stagnating, low-salinity hydrothermal plume spreading laterally in an anoxic ocean layer with minimal sulphate content. There is fragmentary evidence of ocean anoxia in the form of local fine lamination in the shales that host some of the deposits but the total organic carbon, S, Fe, U/Th, Ni/Co, V/Ni and V/Cr relationships indicate deposition under oxic or dysoxic conditions. Vanadium and Mn values range from oxic to anoxic and sulphate-reducing to non-sulphate reducing but Mn may be anomalously low due to derivation by erosion of acidic volcanic rocks. The somewhat equivocal physical and chemical data, combined with the likely disturbing effects of penecontemporaneous volcanism, considerably weaken the case for an anoxic bottom layer in a static ocean. The presence of barite with ambient seawater ³⁴S values in Brunswick no. 12 ore, and the abundance of sulphate in modern euxinic basin waters, make a sulphate-free layer unlikely, even if anoxic. Sulphate-bearing, low-salinity fluids mixing with seawater would lead to growth of barite-bearing chimneys and baritic rubble mounds, which are not observed. A model involving brine-pool deposition better explains the major features of the Bathurst ores.  相似文献   

Arctic Coastal Dynamics (ACD): an introduction     

Volker Rachold  Feliks E. Are  David E. Atkinson  Georgy Cherkashov  Steven M. Solomon 《Geo-Marine Letters》2005,25(2-3):63-68

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Pacific subtropical cell variability in coupled climate model simulations of the late 19th–20th century     

Amy Solomon  Dongxiao Zhang 《Ocean Modelling》2006,15(3-4):236

Observational studies of the Pacific basin since the 1950s have demonstrated that a decrease (increase) in tropical Pacific sea surface temperatures (SSTs) is significantly correlated with a spin-up (slow-down) of the Pacific Subtropical Cells (STCs). STCs are shallow wind-driven overturning circulations that provide a pathway by which extratropical atmospheric variability can impact the equatorial Pacific thermocline and, through upwelling in the eastern equatorial Pacific, tropical Pacific SSTs. Recent studies have shown that this observed relationship between SSTs and STCs is absent in coupled climate model simulations of the late 19th–20th centuries. In this paper we investigate what causes this relationship to breakdown and to what extent this limits the models’ ability to simulate observed climate change in the equatorial Pacific since the late 19th century. To provide insight into these questions we first show that the NCAR Community Climate System Model’s simulation of observed climate change since the 1970s has a robust signal in the equatorial Pacific that bears a close resemblance to observations. Strikingly, absent is a robust signal in the equatorial thermocline. Our results suggest that the coupled model may be reproducing the observed local ocean response to changes in forcing but inadequately reproducing the remote STC-forcing of the tropical Pacific due to the underestimate of extratropical winds that force these ocean circulations. These conclusions are found to be valid in five different coupled climate model simulations of the late 19th–20th centuries (CCSM3, GISS EH, GFDL CM2.1, CSIRO-Mk3, and HadCM3).  相似文献   

Groundwater study using remote sensing and geographic information systems (GIS) in the central highlands of Eritrea   总被引：3，自引：1，他引：3  

Semere Solomon  Friedrich Quiel 《Hydrogeology Journal》2006,14(6):1029-1041

Remote sensing, evaluation of digital elevation models (DEM), geographic information systems (GIS) and fieldwork techniques were combined to study the groundwater conditions in Eritrea. Remote sensing data were interpreted to produce lithological and lineament maps. DEM was used for lineament and geomorphologic mapping. Field studies permitted the study of structures and correlated them with lineament interpretations. Hydrogeological setting of springs and wells were investigated in the field, from well logs and pumping test data. All thematic layers were integrated and analysed in a GIS. Results show that groundwater occurrence is controlled by lithology, structures and landforms. Highest yields occur in basaltic rocks and are due to primary and secondary porosities. High yielding wells and springs are often related to large lineaments, lineament intersections and corresponding structural features. In metamorphic and igneous intrusive rocks with rugged landforms, groundwater occurs mainly in drainage channels with valley fill deposits. Zones of very good groundwater potential are characteristic for basaltic layers overlying lateritized crystalline rocks, flat topography with dense lineaments and structurally controlled drainage channels with valley fill deposits. The overall results demonstrate that the use of remote sensing and GIS provide potentially powerful tools to study groundwater resources and design a suitable exploration plan.The online version of the original article can be found at  相似文献   

Genesis of the Shear Zone-related Gold Vein Mineralization of the Lega Dembi Gold Deposit, Adola Gold Field, Southern Ethiopia     

Solomon Tadesse 《Gondwana Research》2004,7(2):481

The Lega Dembi Primary Gold Deposit in southern Ethiopia is related to the shear zone-hosted vein in the Neoproterozoic metamorphosed volcano-sedimentary succession of greenschist- to amphibolite-facies metamorphism. The rocks consists of a sequence of biotite-feldspar-quartz schists, carbonaceous mica-schists, amphibolites and basic to ultrabasic rocks. This unit is separated from a foot wall biotite gneiss by a major shear zone. The ore bodies are hosted in the volcano-sedimentary sequence and consist of swarms of quartz veins, lenses, and stockworks that propagated along mesoscale ductile to brittle-ductile shear zones.The mineralization is defined by a complex paragenesis of gold in association with Cu-Pb-Zn-Fe sulphides, tellurides and sulphosalts. The presence of Ni-bearing minerals in amphibolites of the host sequence, together with the ore mineral association, suggests an origin related to mafic volcanism.  相似文献   

Urban land transformation for pro-poor economies   总被引：1，自引：0，他引：1  

Solomon Benjamin 《Geoforum》2004,35(2):177-187

The transformation of land into a setting for clustering local economies can become an important cornerstone of poverty policy. This transformation has several functional aspects, which in turn have important institutional and political aspects. Underlying both the functional and institutional factors is the role of local government and local democracy. Such a conceptualization puts to center stage several paradoxes: A terrain that seems “slum-like” turns out to be highly productive and employment generating. Complex tenure forms and mixed land use seen as “unplanned” turn out to be pre-requisites for economic development. There are institutional paradoxes that contrast efforts at “transparency” and managerial “best practices”. Here, the messiness of local bureaucracies in municipal government turns out to be critical for poor groups to influence interventions in their favor. Influencing the public process may be more effective in stealth-like ways rather taking a more visible approach. Most fundamentally these issues remind us that the potential of cities to reinforce or reduce poverty moved far beyond projects and programs and the normative frameworks used by planners and administrators. Instead, it is the transformative process of turning land into economic settings that might be at the center stage. This is a stage where poor groups are the central actors who stealth-like draw on complex alliances across ethnic and class lines to shapes cities in their interests.  相似文献   

Lajishan accretionary complex: Implications for Paleozoic accretionary and collisional events in the South Qilian belt     

YAN Zhen  FU Changlei  Jonathan AITCHISON  Solomon BUCHMON  NIU Manlan 《《地质学报》英文版》2018,92(Z2):41-41

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Comparison of taxon calibrations,modern analogue techniques,and forest-stand simulation models for the quantitative reconstruction of past vegetation: A critique     

Allen M. Solomon 《地球表面变化过程与地形》1986,11(6):681-685

Taxon calibrations based on eastern North America or on the southeastern United States alone suggest a different forest composition from that based on Wisconsin/Michigan, which is argued as preferable. Questions are raised about how well comparison with modern analogues distinguishes forest characteristics. The simulation model used by Delcourt and Delcourt is thought to be inappropriate, partly because it is constrained by faulty climatic data. Models are seen as complementary to other techniques rather than as an alternative methodology.  相似文献   

Site Characterization Using ³H/³ He Ground-Water Ages, Cape Cod, MA     

D. K. Solomon  R. J. Poreda  P. G. Cook  A. Hunt 《Ground water》1995,33(6):988-996

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Impact of the Montreal protocol and its amendments on the rate of change of global radiative forcing     

Susan Solomon  John S. Daniel 《Climatic change》1996,32(1):7-17

Increases in chlorinated and brominated halocarbons are believed to be responsible for the depletion of stratospheric ozone observed over much of the globe in the past decade or so. Ozone depletion is in turn believed to lead to a negative radiative forcing, tending to cool the stratosphere and the surface. We show that the increasing atmospheric concentrations of ozone-depleting halocarbons and onset of related ozone depletion likely led to a negative forcing of the climate system in the 1980s that slowed significantly the rate of change of total anthropogenic radiative forcing due to the combined effect of all greenhouse gases over that decade. Within the next decade, emissions of these halocarbons are expected to rapidly decrease, with corresponding impacts on ozone and radiative forcing. As the emissions of ozone-depleting gases are reduced and eventually phased out, the rate of ozone depletion is expected to decrease and eventually reverse. All other things being equal, we show that the change from deepening ozone depletion in the 1980s to ozone increases in the future should lead to a pronounced increase in the decadal rate of change of anthropogenic greenhouse forcing of the next few decades, perhaps to levels unprecedented in this century.  相似文献