instrumental techniques applied to mineralogy and geochemistry

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128 Kjell Bilström Besides, mineralogical and trace element studies may give additional information. The isotope approach has the advantage of providing a direct comparison between collected dust and its potential source area(s). FIGURE 7. Sr-Nd isotopic composition of suspended matter from rivers entering the main world oceans (after Goldstein and Jacobsen, 1988). This opens up the possibility for modelling dust transport in the past which have important implications for climate reconstructions and historical atmospheric circulation patterns. For example, aeolian dust in the atmosphere can either reflect or absorb solar energy as a function of e.g. mineralogy and grain size. Moreover, continental dust settling in the oceans may affect the marine productivity, and pollutants are also easily carried by dust particles (Grousset and Biscaye, 2005). As for other finger-printing applications, the ability of provenancing dust makes use of the fact that the Nd, Sr and Pb isotope ratios are different in mantle- versus crustal-derived rocks. The example presented here is taken from Greenland´s ice-sheet which was found to have quite variable lead contents. One peak coincided with the period between ca. 150 B.C. and A.D. 50 during the Roman era (Rosman, 1998). The lead isotope composition actually measured in that interval of the ice core demonstrated a good match with lead mined at Rio Tinto in Spain. As this mine is known to have been processed by the Romans it can be concluded that air-borne lead was transported north-wards from Spain and finally
Radiogenic isotopes and their applications within a range of scientific fields 129 reaching Greenland. Another peak in the lead concentration record, representing about 25-50 times higher Pb concentrations, characterizes the period between ca. 1930 and 1980 and is readily interpreted as a contamination effect of leaded petrol. Anthropogenic Pb in petroleum and other pollutants The ALAS model is an important tool for estimating the age of hydrocarbon release (Hurst, 2000). It is based on systematic increases in lead isotope ratios in petrol caused by shifts in sources of lead ores used by the petroleum industry in North America. The ALAS calibration curve relies on isotope measurements of soils and water of known age, affected by petroleum products, and isotope data of the hydrocarbon products themselves. Due to an increasing usage of radiogenic MVT type of ores in leaded petrol, age uncertainties are as low as a few years. An application of this model is to correlate environmental releases of e.g. diesel and motor oil to their sources, and anthropogenic gasoline-derived lead has been mapped for many areas in the U.S. Numerous studies have been devoted to metal dispersions from mine sites. Pb isotopes is an ideal tool as lead occurs in detectable amounts in most ore-forming environments, whilst the parent elements U and Th typically occur in amounts that is negligible in most provenance studies. Even if the U and Th contents are relatively high in a studied system, the slow decay of these elements to form stable lead isotopes means that for young systems, like those affected by anthropogenic processes, this is not a problem. MacKenzie and Pulford (2002) investigated to what degree former activities at a mine site at Tyndrum, Scotland, could be detected in the environment. Samples of mining wastes, river sediments and peat cores were analyzed. Pb concentrations were high in e.g. river sediments near the mine, but the concentrations decreased markedly downriver from the mining site. Based on obtained Pb isotope data, the main source of lead in the studied samples could be coupled with the mining operations, although a certain influence of local bedrock geology and of leaded petrol could also be detected.
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SEMINARIOS DE LA SOCIEDAD ESPAÑOLA
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FOREWORD On the occasion of the Spa
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INDEX Electron back-scattered diffr
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TEM in Geology. Basics and applicat
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Page 82 and 83: 84 Clemente Recio Isotope Terminolo
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Page 88 and 89: 90 Clemente Recio beers. Some brand
Page 90 and 91: 92 Clemente Recio The source of the
Page 92 and 93: 94 Clemente Recio By using GC-C-IRM
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Page 96 and 97: 98 Clemente Recio such as blood and
Page 98 and 99: 100 Clemente Recio relatively simpl
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Page 102 and 103: 104 Clemente Recio and high N in dr
Page 104 and 105: 106 Clemente Recio although 15 N d
Page 106 and 107: 108 Clemente Recio spectrometers th
Page 108 and 109: 110 Clemente Recio O’Brien, D.M.
Page 110 and 111: 112 Kjell Bilström time in old geo
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Page 116 and 117: 118 Kjell Bilström Molybdenite is
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Page 120 and 121: 122 Kjell Bilström radiogenic sign
Page 122 and 123: 124 Kjell Bilström plants inherits
Page 124 and 125: 126 Kjell Bilström in some cases a
Page 128 and 129: 130 Kjell Bilström References Bear
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