Lead isotope compositions

Lead isotopes. Sato and Sasaki (1973) concluded on the basis of a remarkable narrow range in lead isotopic composition of Kuroko ores that lead of Kuroko ore came from deep-seated source which originated from subducting pelagic sediments. 

Lead isotopic data on the epithermal deposits together with Kuroko deposits are plotted in Fig. 1.116 (Sato and Sasaki, 1973 Sato et al., 1973, 1981 Sato, 1975 Sasaki et al., 1982 Sasaki, 1987 Fehn et al., 1983). It is evident that lead isotopic compositions of epithermal vein ores are more scattered than Kuroko ores, although averaged values are similar to the Kuroko ores. This variation seems to be due to the difference in crustal materials underlying the ore deposits Lead isotopic compositions of different ore deposits which formed at different ages in the same district show the same values (Sasaki, 1974). 

Halbach et al. (1997) reported lead isotope data on volcanic rocks, sediments and ores from the hydrothermal JADE field in the Okinawa Trough and pointed out that lead isotopic compositions of Okinawa JADE ores are very similar to Kuroko ores (Fig. 2.31) and both sediments and volcanic rocks contributed comparable amounts of lead to the deposit. 

Oversby VM, Gast PW (1968) Lead isotope composition and uranium decay series disequilibrimn in recent volcanic rocks. Earth Planet Sci Lett 5 199-206... 

O Hara MJ (1968) The bearing of phase equilibria studies in synthetic and natural systems on the origin and evolution of basic and ultrabasic rocks. Earth Sci Rev 4 69-133 O Nions RK, McKenzie D (1993) Estimates of mantle thorium/uranium ratios from Th, U and Pb isotope abundances in basaltic melts. Phil Trans Royal Soc 342 65-77 Oversby V, Gast PW (1968) Lead isotope compositions and uranium decay series disequilibrium in reeent volcanic rocks. Earth Planet Sci Lett 5 199-206... 

Figure 8. ° Pb7 Pb vs. Th/Us (derived using Eqn. 5 in the text) diagram for mid-ocean ridge and ocean island basalt based on a recent data set with mostly mass spectrometry measurements (Turner et al. 1997 Bourdon et al. 1996 Dosso et al. 1999 Claude-lvanaj et al. 1998, 2001 Sims et al. 2002). The data show a relatively well defined array that intersect a closed-system hne for the bulk Earth starting with an initial lead isotope composition equal to Canyon Diablo (T = 4.55 Ga). This intersect was used by Allegre et al. (1986) to define the Th/U ratio of the Earth.

Gale, N. and Z. Stos-Gale (1996), Lead isotope methodology The possible fractionation of lead isotope compositions during metallurgical processes, in S. Demirci, A. M. Ozer, and G. D. Summers (eds.), Proc. Archaeometry Symp. Ankara, 1994, pp. 287-299. 

Four samples from a Polynesian island gave the lead isotope compositions given in Table 4.3. Calculate the mean and standard deviation vectors, the covariance matrix and the correlation coefficient between the two isotope ratios. 

Table 5.21. Average lead isotope compositions measured over three blocks with standard deviations and correlation coefficients. The last row indicates the weighted mean of the three blocks and its standard deviation and correlation coefficient.

The determination of an age using the Pb-Pb isochron method relies on the assumption that all samples that define the isochron had the same initial lead isotopic composition, formed at the same time, and remained closed to uranium and lead until the very recent past. 

Vollmer R, Hawkesworth CJ (1980) Lead isotopic composition of the potassic rocks from Roccamonfina (south Italy). Earth Planet Sci Lett 47 91-101 Voltaggio M, Barbieri M (1995) Geochronology. In Trigila R (ed) The volcano of the Alban Hills. University La Sapienza, Rome, pp 167-192... 

A kimasa, Masuda Lead isotope composition in volcanic rocks of Japan. Geochim. cosmochim. Acta 28, 291 (1964). 

Figure 8 Lead isotopic compositions for NIST SRM 981 as measured on the VG Elemental Plasma 54 (P54) at the University of Michigan, using T1 correction for mass bias. Open dots, individual data ( 2amean) from three measurement sessions over a 2-month period filled dots, our mean ( 2o and 2omean filled square, data from Todt et al. (1996) ( 2omean) filled triangle, certified values.

Figure 12 Lead isotopic compositions of two central Pacific Fe-Mn crusts as a function of depth. (From Christensen et al., 1997.)...

Table 12.1 Lead isotopic compositions of pesticides, herbicides, and feed additives... 

Figure 12.7 206Pb/207Pb versus 208Pb/207Pb plot showing the lead isotopic compositions of lead... 

Although the predominant source of arsenic and metals to most soils and sediments in New England is sulfide-rich rock, the extensive application of arsenical pesticides and herbicides (lead arsenate, calcium arsenate, and sodium arsenate, and others) on apple, blueberry, and potato fields may have been a possible anthropogenic source of arsenic and lead. The main objective of this study was to determine the lead isotopic compositions of commonly used pesticides, such as lead arsenate, sodium metarsenite, and calcium arsenate, in order to assist in future isotopic comparisons and to better characterize this anthropogenic source of Pb. The pesticides plot along a linear trend in isotope diagrams, for example, in values of... 

Ayuso, R., Foley, N., Robinson, G., Jr., Wandless, G., and Dillingham, J. (2004b). Lead isotopic compositions of common arsenical pesticides used in New England. United States Geological Survey. Open-file report 2004-1342, 14. [URL http //pubs.usgs.gov/of/2004/1342/]. 

Bouse, R. M., Ruiz, J., Tidey, S. R., Tosdal, R. M., and Wooden, J. L. (1999). Lead isotope compositions of Late Cretaceous and Early Tertiary igneous rocks and sulfide minerals in Arizona Implications for the sources of plutons and metals in porphyry copper deposits. Econ. Geol. 94, 211-224. 

Tommasini, S., Davies, G., and Elliott, T. (2000). Lead isotope composition of tree rings as bio-geochemical tracers of heavy metal pollution A reconnaissance study from Firenze, Italy. Appl. Geochem. 15, 891—900. 

So far, the only available technique capable of sufficiently accurate measurement of lead isotope compositions, both for isotope geochemistry and for archaeological applications, is thermal ionization mass spectrometry. Any well-equipped laboratory can routinely measure lead isotope ratios with... 

The question of lead isotope uniformity in an ore body has also been investigated in several other laboratories. Many ore deposits, especially the so-called strata-bound or comformable ore deposits, have a lead isotope composition that varies very little throughout the whole deposit, often by less than 0.3%. Such ore deposits commonly have lead isotope compositions that lie close to a single-stage model evolution curve (28). Such a simple model cannot describe the composition in any real ore body. 

In contrast with conformable ore deposits, some vein-type ore deposits have variable lead isotope compositions that plot as linear arrays of data points in one or both lead isotope diagrams. Such anomalous, or multistage, ore deposits can sometimes cause difficulties for archaeological provenance studies (30-31). Fortunately, deposits of this type are not common in the region of the Mediterranean indeed, none have yet been found. Only in... 

Fenan, Timna, and central Anatolia, have ore sources been found that retain sufficient uranium or thorium to cause variable present-day lead isotope compositions in a single ore deposit. 

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