Quantitative high resolution cathodoluminescence spectroscopy of diagenetic and hydrothermal dolomites   总被引：2，自引：0，他引：2  

Axel Gillhaus  Detlev K. Richter  Jan Meijer  Rolf D. Neuser  Andreas Stephan 《Sedimentary Geology》2001,140(3-4):191-199

A combination of high resolution cathodoluminescence-spectroscopy (HRS-CL=high resolution spectroscopy of cathodoluminescence emission) with spatial resolving trace element analyses (PIXE=proton induced X-ray emission) is used to establish a method for the quantitative determination of the Mn-content of diagenetic and hydrothermal dolomites using the measurements of peak areas of Mn-activated CL emission bands. This method takes into account the overlap of the CL broad bands of Mn²⁺ in the Mg- and the Ca-lattice-position of dolomite. There is a linear correlation between the peak areas and Mn concentration up to approx. 1000–1500 ppm. Thus, CL spectroscopy allows a determination of Mn concentrations below the abilities of PIXE (10–15 ppm) to less than 1 ppm by extrapolation of this linear relation.

Up to an Fe-content of approx. 2000 ppm, no quenching effect of Fe on this linear relationship occurs. However, Fe-contents above 2000 ppm result in a decrease of Mn-induced luminescence. Even at Fe-concentration >25,000 ppm spectroscopy reveals that Mn-activated CL of dolomite is not entirely extinguished.  相似文献   

Geochemistry of the late Cenomanian-early Turonian chalks of the Paris Basin: Manganese and carbon isotopes in carbonates as paleooceanographic indicators     

B. Pomerol 《Cretaceous Research》1983,4(1):85-93

In the North Atlantic DSDP/IPOD cores, carbon isotope data on the bulk carbonates show significant fluctuations. In sediments now exposed on land coeval fluctuations in the carbon isotope concentrations are also recorded in pelagic and epeiric facies. For instance, in the Upper Cretaceous chalks of the Paris Basin, there is a major break at the Cenomanian-Turonian boundary. At this time, the manganese content of the chalks was also at a maximum and consequently a positive relation can be demonstrated between δ¹³C and manganese concentrations. The same positive correlation is also recorded in many pelagic limestones.In the North Atlantic cores, carbon isotope events are related to the black shale facies and to global oceanic anoxic events and one can suppose that in sediments deposited on the continental margins they are also related to mildly anoxic conditions. Considering the manganese geochemistry in carbonate rocks, a high manganese content in such a reducing environment can be found in the sediments only if the Mn concentration of the interstitial solutions are abnormally high. As a high Mn content in marine pore waters is believed to originate from hydrothermal process, Mn and δ¹³C positive excursions are ultimately related to mid-oceanic ridge activity and to a closely connected phenomenon, the great transgressive pulses during which mid-depth waters may have been anoxic. Consequently, major Mn and carbon isotope events would seem to be useful tools in paleooceanographic reconstructions.  相似文献   

Bioavailable copper and manganese in soils from Iceland and their relationship with scrapie occurrence in sheep   总被引：1，自引：0，他引：1  

K. Vala Ragnarsdottir  Darren P. Hawkins 《Journal of Geochemical Exploration》2006,88(1-3):228

The bioavailability of trace metals can be directly linked with many common animal and human diseases. It is easier to correlate regional geochemical trends with disease distribution in the developing world because local populations and animals live from the land. In the western world, humans tend to live from the global food market whereas animals graze on the land. Recent biochemical studies have shown that the prion protein needs copper to keep its structure. If copper is not available, the prion protein can take up manganese and unfold. Preliminary results for trace metals in soil samples from scrapie-affected areas in Iceland show that bioavailable manganese manganese (easily reducible and exchangeable Mn) is very high whereas soluble copper and free copper are very low.  相似文献   

An Image Analysis Technique for Exploration of Manganese Nodules     

Chan-Young Park  Seung-Ho Park  Choon-Woo Kim  Jung-Keuk Kang  Ki-Hyune Kim 《Marine Georesources & Geotechnology》1999,17(4):371-386

In order to develop the mineral resources contained in manganese nodules of the deep sea, the Korea Ocean Research & Development Institute (KORDI) has explored the area allocated by the United Nations in the Clarion-Clipperton Fracture Zone in the northeastern Pacific. During research cruises, the seabed surface was photographed every 30 s by the KORDI Deep Tow Imaging System (DTIS). Features such as the coverage and size distribution of manganese nodules on the photographs serve as the essential information to determine the potential mining areas. This article presents (semi)automatic procedures to extract the useful features from the photographs of the seabed surface using digital image processing techniques. The 35-mm films are first digitized by the film scanner. The depth information written on the film is then recognized to compensate for distortions due to nonuniform illumination. The nodule areas on the digitized image are recognized and separated from the background based on the characteristics of the nodules. The nodule coverage and distribution of nodule diameters are then calculated from the processed image. The proposed technique has been applied to sample photographs of the seabed surface. Experimental results indicate that the technique could be utilized as an efficient tool to process the massive collection of photographs of the seabed surface.  相似文献   

A comparative study of iron and manganese diagenesis in continental slope and deep sea basin sediments off Uruguay (SW Atlantic)     

R. R. Haese  J. Schramm  M. M. Rutgers van der Loeff  H. D. Schulz 《International Journal of Earth Sciences》2000,88(4):619-629

Pore water and solid phase from surface sediments of the continental slope off Uruguay and from the Argentine Basin (southwestern Atlantic) were investigated geochemically to ascribe characteristic early diagenetic reactions of iron and manganese. Solid-phase iron speciation was determined by extractions as well as by Mössbauer spectroscopy. Both methods showed good agreement ( <6% deviation) for total-Fe speciation. The proportion of easy reducible iron oxyhydroxide relative to total-Fe oxides decreased from the continental slope to the deep sea which is attributed to an increase in crystallinity during transport as well as to a general decrease of iron mobilization. The product of iron reoxidation is Fe oxyhydroxide which made up less than 5% of total Fe. In addition to this fraction, a proportion of smectite bound iron was found to be redox reactive. This fraction made up to 10% of total Fe in sediments of the Argentine Basin and was quantitatively extracted by 1?N HCl. The redox reactive Fe(+II) fraction of smectite was almost completely reoxidized within 24?h under air atmosphere and may therefore considerably contribute to iron redox cycling if bioturbation occurs. In the case of the slope sediments we found concurrent iron and manganese release to pore water. It is not clear whether this is caused by dissimilatory iron and manganese reduction at the same depth or dissimilatory iron reduction alone inducing Mn(+IV) reduction by (abiotic) reaction with released Fe²⁺. The Argentine Basin sediment showed a significant manganese solid-phase enrichment above the denitrification depth despite the absence of a distinct pore-water gradient of Mn. This implies a recent termination of manganese mobilization and thus a non-steady-state situation with respect to sedimentation or to organic carbon burial rate.  相似文献   

Environment and Deep-Sea Mining: A Perspective   总被引：1，自引：0，他引：1  

B. Nagender Nath  R. Sharma 《Marine Georesources & Geotechnology》2000,18(3):285-294

As the quest for deep-sea mineral resources is gaining momentum, environment and ocean mining have become important aspects of study. Because many of these deposits occur in international waters, the concern for environmental conservation in view of the effects of deep-sea mining is resulting in these effects being studied in different oceans, and efforts to develop regulations governing this exploitation are also underway at national and international levels. The impact assessment of deep-sea mining needs to encompass a variety of subjects, including environmental, socioeconomic, technological, and legal aspects. At the same time, effects of in situ environmental conditions on mining activities also need to be considered for effecient performance by the mining system. Differences in the degree of impact have been noticed during the mining simulation experiments by different investigating agencies. Therefore, interparameter comparisons, standardization of methods, and improvement in mining design are important considerations for proper utilization of resources, conservation of environment, and cost efficiency of the mining operations.  相似文献   

Ar/Ar dating of central European K–Mn oxides — a chronological framework of supergene alteration processes during the Neogene     

S. Hautmann  H. J. Lippolt 《Chemical Geology》2000,170(1-4):37-80

K-bearing Mn oxides may potentially constitute useful objects for isotopic dating of ore-forming events. A comprehensive ⁴⁰Ar/³⁹Ar study performed on supergene K–Mn oxides sampled from different sub-alpine mountain terrains in Germany and France has been undertaken. The objective of these investigations was to provide new insight into how and when these secondary Mn accumulations may have formed. Developed in supergene environments at the expense of Mn²⁺/Mn³⁺-bearing precursor minerals, the Mn⁴⁺ oxides occur either as pseudomorphic ores or as cavity-fillings and linings.

The isotopic ages range from 25 to 1 Ma, indicating intense chemical weathering, especially during the Miocene and Pliocene. It is yet too early to decide whether the age range represents a more or less continuous process or distinct weathering episodes. Formation of supergene Mn oxides may result from combined climatic and tectonic factors: local uplift, exhumation, and associated fracturing of rocks provided fresh mineral surfaces for percolating meteoric fluids that induced subsequent weathering under warm–temperate to subtropical conditions.  相似文献   

Cobalt, manganese, and iron near the Hawaiian Islands: A potential concentrating mechanism for cobalt within a cyclonic eddy and implications for the hybrid-type trace metals   总被引：1，自引：0，他引：1  

Abigail E. Noble  Mak A. Saito  Kanchan Maiti  Claudia R. Benitez-Nelson 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1473

The vertical distributions of cobalt, iron, and manganese in the water column were studied during the E-Flux Program (E-Flux II and III), which focused on the biogeochemistry of cold-core cyclonic eddies that form in the lee of the Hawaiian Islands. During E-Flux II (January 2005) and E-Flux III (March 2005), 17 stations were sampled for cobalt (n=147), all of which demonstrated nutrient-like depletion in surface waters. During E-Flux III, two depth profiles collected from within a mesoscale cold-core eddy, Cyclone Opal, revealed small distinct maxima in cobalt at 100 m depth and a larger inventory of cobalt within the eddy. We hypothesize that this was due to a cobalt concentrating effect within the eddy, where upwelled cobalt was subsequently associated with sinking particulate organic carbon (POC) via biological activity and was released at a depth coincident with nearly complete POC remineralization [Benitez-Nelson, C., Bidigare, R.R., Dickey, T.D., Landry, M.R., Leonard, C.L., Brown, S.L., Nencioli, F., Rii, Y.M., Maiti, K., Becker, J.W., Bibby, T.S., Black, W., Cai, W.J., Carlson, C.A., Chen, F., Kuwahara, V.S., Mahaffey, C., McAndrew, P.M., Quay, P.D., Rappe, M.S., Selph, K.E., Simmons, M.P., Yang, E.J., 2007. Mesoscale eddies drive increased silica export in the subtropical Pacific Ocean. Science 316, 1017–1020]. There is also evidence for the formation of a correlation between cobalt and soluble reactive phosphorus during E-Flux III relative to the E-Flux II cruise that we suggest is due to increased productivity, implying a minimum threshold of primary production below which cobalt–phosphate coupling does not occur. Dissolved iron was measured in E-Flux II and found in somewhat elevated concentrations (0.5 nM) in surface waters relative to the iron depleted waters of the surrounding Pacific [Fitzwater, S.E., Coale, K.H., Gordon, M.R., Johnson, K.S., Ondrusek, M.E., 1996. Iron deficiency and phytoplankton growth in the equatorial Pacific. Deep-Sea Research II 43 (4–6), 995–1015], possibly due to island effects associated with the iron-rich volcanic soil from the Hawaiian Islands and/or anthropogenic inputs. Distinct depth maxima in total dissolved cobalt were observed at 400–600 m depth, suggestive of the release of metals from the shelf area of comparable depth that surrounds these islands.  相似文献   

贵州省松桃县道坨超大型锰矿床地质地球化学基本特征   总被引：4，自引：0，他引：4  

朱祥坤  彭乾云  张仁彪  安正泽  张飞飞  闫斌  李津  高兆富  覃英  潘文 《地质学报》2013,87(9):1335-1348

本文报导了贵州省松桃县新发现的一个全隐伏的超大型锰矿床——道坨锰矿床的地质地球化学基本特征,为进一步开展科学研究奠定基础。矿床赋存在新元古代成冰系（南华系）大塘坡组底部的含锰碳质页岩中,主要由条带状、块状、气泡状菱锰矿矿石组成。主量元素特征为Al₂O₃、TiO₂、Fe₂O₃含量较低,中等程度的P₂O₅富集,MnO、MgO含量相对较高,Fe/Mn比值低。微量元素特征为Rb、Nb和Pb亏损,Co、Zn、Sr、Mo相对富集。稀土元素总稀土含量高、中稀土轻微富集、Ce的正异常明显为特征。道坨锰矿含锰层位中黄铁矿的δ³⁴S_-VCDT值异常高,并且变化范围小,所测试黄铁矿的δ³⁴S_-VCDT值介于56.2‰⁶3.3‰,平均60.8‰。新发现的道坨超大型锰矿床属于典型的大塘坡式锰矿床,其发现不仅为研究新元古代大规模成锰作用提供了新机遇,同时也为研究成冰系环境演化及其资源、生物效应提供了新契机。  相似文献   

云南鹤庆锰矿成矿规律控矿因素新认识   总被引：1，自引：0，他引：1  

魏蓉花  杨枝斌  雷阳艾  李真冲  何志芳 《云南地质》2009,28(4):415-419

鹤庆锰矿,赋存于印支运动形成的东西向裂陷槽中,成矿时限应早于松桂湖的中、晚北衙期,分出同生沉积型和淋滤充填型。控矿构造为特殊的向斜轴部“锅底凹”,成因属于火山热液同生沉积、后期改造型锰矿床。  相似文献