Pb isotopic composition

Fig. 2.57. Pb isotopic compositions in volcanogenic Cu sulfide deposits in Japan. Diamond shape K], K2 and K3 indicate average values of Kuroko-type deposits Ki Taro (Cretaceous) K2 Northeast Japan (Miocene) K3 southwest Japan (Miocene). Note that the Shimokawa ores (solid square, Besshi subtype) and Yanahara ores (open square, Hitachi subtype), closely associated with sediments, tend to have slightly more radiogenic values than the others (solid circles) (Sato and Kase, 1996).

Table 4.4. Contours of the 95 percent confidence ellipse of the mean for the Pb isotope composition...

Table 5.23. Pb isotope composition of Archean granites from Zimbabwe (courtesy...

Figure 18. Temporal variations in Fe and Pb isotope composition for layers in Fe-Mn crust BM1969.05 from the Blake Plateau, Atlantic Ocean. Iron isotope data from Zhu et al. (2000) and Pb isotope data and ages from O Nions et al. (1998) and Reynolds et al. (1999). Modified from Zhu et al. (2000).

Figure 11,25 Th-Pb and U-Pb isotopic compositions of whole rocks from Granite Mountains Formation (Wyoming) based on data of Rosholt et al. (1973). 2.79 Ga isochrons based on Pb-Pb age are superimposed, to highlight effect of differential elemental remobilization.

Sandstone around the uranium deposits typically has radiogenic ° PbF° Pb isotope ratios (>30) (Fig. 5), with Pb isotopic compositions that are unsupported by the amount of U in the sandstone. This is consistent with the introduction of this Pb... 

Comment More accurate calculation requires adjustment of Pb atomic mass using the calculated Pb isotopic composition based on Th and U abundance and the age, and then calculating the number of moles of Pb per kilogram of monazite. Iterate until the age converges. The result is still 382 Ma. Error calculation is relatively complicated and not discussed here. 

Equation 5-61 involves only Pb isotopic ratios and is called the Pb-Pb isochron. There are a few advantages of this Pb-Pb isochron compared to the individual U-Pb isochrons. One is that Pb isotopic ratios can be measured more accurately than U/Pb ratios. Hence, the above equation has the advantage of Ar-Ar method compared to the K-Ar method. Secondly, if there was recent (such as yesterday or in the last million years) U loss or gain or Pb loss, the loss or gain would not affect the Pb isotopic composition and hence would not affect Pb-Pb dating (but it would affect U-Pb isochrons). Pb gain would affect the Pb-Pb isochron. 

Fig. 9.8. Sr-Nd-Pb isotopic composition of Sardinian Plio-Quatemary volcanic rocks. Compositions of EMI mantle end-member and of other Italian volcanic provinces are also shown. Symbols as in Fig. 9.3.

De Astis G, Peccerillo A, Kempton PD, La Volpe L, Wu TW (2000) Transition from calc-alkaline to potassium-rich magmatism in subduction environments geochemical and Sr, Nd, Pb isotopic constraints from the island of Vulcano (Aeolian arc). Contrib Mineral Petrol 139 684-703 De Astis G, Kempton PD, Peccerillo A, Wu TW (2005) Geochemical and Sr-Nd-Pb isotope composition of Vulture and Campanian Province volcanics (southern Italy) implications for mantle evolution and geodynamics. Submitted for publication... 

Mn crusts grow slowly over millions of years, sequestering high concentrations of Pb and providing a long-term record of such changes (Christensen et al., 1997). The analysis of Fe-Mn crusts for Pb isotopic composition using laser ablation MC-ICP-MS has been employed to produce a record of Pb contributions to the central Pacific Ocean (Christensen et al., 1997). 

Table 12.2 Pb and As contents and Pb isotope compositions of leach samples from soil profiles, Northport area, coastal Maine... 

In the case of lead arsenate (acid form), calcium arsenate, and sodium arsenate, the Pb-isotopic compositions closely match those of sulfides from porphyry copper deposits from southeastern Arizona, specifically from the Pima and Silver Bell districts (Bouse et al., 1999). Notably, other major historical producers of arsenic trioxide (e.g., Anaconda Copper Co., US Smelting Co., Jardine Mining Co.) used... 

This study was carried out to test whether Pb isotope compositions of soils and tills can be linked to use of arsenical pesticides, other anthropogenic point sources,... 

Pb isotopes are used to study environmental pollution because of their relative geochemical immobility and the wide use of Pb in industrial processes. Moreover, Pb isotopes are not fractionated by natural or industrial processes Pb isotopic composition in a material remains constant in time and reflects the nature of the source (Ault et al., 1970). 

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