Pb isotopes evolution

Newsom H. E., White W. M., Jochum K. P., and Hofmann A. W. (1986) Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the Earth s core. Earth Planet. Sci. Lett. 80, 299-313. 

FIGURE 3.30 The Kramers and Tolstikhin (1997) Pb-isotopic evolution curve for the Earth s mantle, given an initial /x(1 8U/204Pb ratio) of 11.2, relative to the field of initial Pb-isotope compositions, the MORB field, the 4.55 Ga Geochron and the primordial Pb-isotopic composition. The numbered marks on the mantle evolution curve indicate Ga before the present. The cross marks the composition of the average continental crust. 

In the several versions of their models, Doe and Zartman (1979) and Zartman and Haines (1988) have plotted curves to show the Pb isotopic evolution of the four reservoirs with time. A plot of vs ° Pb/ Pb discriminates well... 

Hoemle K., Tilton G. and Schmincke H-U., 1991, Sr Nd-Pb isotopic evolution of Gran Canaria evidence for shallow enriched mantle beneath the Canary Islands. Earth Planet. Sci. Lett.f 44—63. 

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... 

Zircon (ZrSi04) is a common accessory mineral in igneous and metamorphic rocks. It can take a significant amount of U in its structure (in the Zr site) at the thousands of ppm level, but takes very little original Pb. Because there is an unradiogenic stable isotope of Pb ( °" Pb), the very minor amount of initial ° Pb and ° Pb may be roughly corrected by assuming reasonable initial ratios of ° Pb/ °" Pb and ° Pb/ ° Pb (based on the evolution of these ratios with time in the Earth). Two U isotopes decay to two Pb isotopes decays to Pb, and... 

Figure 5-8 A Pb-Pb isochron that determined the age of the Earth to be about 4.55 Ga. Stony and iron meteorites as well as a sediment of the Earth are plotted on a Pb-Pb isochron. The sediment, as a "bulk sample of the silicate Earth in terms of Pb isotopes, plots on the same line as the meteorites, suggesting that the Earth and meteorites formed at the same time and are the same age. Erom Patterson (1956). Later studies reveal a more detailed evolution history of the Earth, including core formation (about 4.53 Ga), atmospheric formation (about 4.45 Ga), and crustal evolution.

One drawback of the Pb-Pb system is that two-stage or three-stage evolution of the U-Pb isotopic system can produce linear arrays on a Pb-Pb isochron plot (Gale and Mussett, 1973). If these arrays are interpreted as single-stage isochrons, incorrect dates may be obtained. In some cases, measurements of the U/Pb ratio can help identify multistage samples. But if several events occurred sufficiently early in solar system history, even a concordia approach may not be able to identify a multistage system (Tera and Carlson,... 

The common-lead method looks at the isotopic evolution of lead in systems with U/Pb and Th/Pb ratios similar to or less than the ratios in bulk solar system materials. The original formulation, by Holmes and Houtermans, is a single stage model that accounts for the isotopic composition of any sample of common lead in terms of primordial lead plus radiogenic lead produced in the source up to the time that lead was separated from uranium and thorium. Multistage models that more accurately describe the evolution of natural systems have been developed. The common-lead method is used in cosmochemistry primarily to study the time of differentiation and reservoir evolution in differentiated bodies... 

Radiogenic isotope data have added important information on evolution of mantle sources. The continuous trends of Sr-Nd-Pb isotope ratios along the Italian peninsula, from Etna-Iblei to Tuscany, have been interpreted as a result of contamination of upper mantle by different types of upper... 

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... 

Del Moro A, Gioncada A, Pinarelli L, Sbrana A, Joron JL (1998) Sr, Nd, Pb isotope evidence for open system evolution at Vulcano, Aeolian Arc, Italy. Lithos 43 81-106... 

Jagoutz E., Jotter R., Varela M. E., Zartman R., Kurat G., and Lugmair G. W. (2002) Pb-U-Th isotopic evolution of the D Orbigny angrite. In Lunar Planet. Sci. XXXIII, 1043. The Lunar and Planetary Institute, Houston (CD-ROM). 

Amelin Y., Lee D.-C., and Halliday A. N. (2000) Early-middle Archean crustal evolution deduced from Lu-Hf and U-Pb isotopic studies of single zircon grains. Geochim. Cosmochim. Acta 64, 4205-4225. 

Rudnick R. L. and Goldstein S. L. (1990) The Pb isotopic compositions of lower crustal xenoUths and the evolution of lower crustal Pb. Earth Planet Sci. Lett 98, 192-207. 

Walker R. J., Carlson R. W., Shirey S. B., and Boyd F. R. (1989a) Os, Sr, Nd, and Pb isotope systematics of southern African peridotite xenoliths implications for the chemical evolution of sub-continental mantle. Geochim. Cosmochim. Acta S3, 1583-1595. 

Ellam R. M., Hawkesworth C. J., and McDermott F. (1990) Pb isotope data from Eate Proterozoic subduction-related rocks implications for crust-mantle evolution. Chem Geol. 83, 165-181. 

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