Start Pb pb dating

Pb pb dating

We have analyzed the Pb isotopic compositions of whole-rocks and various components (CAIs, chondrules, and/or mineral separates) of two carbonaceous chondrites, Allende (CV3) and Murchison (CM2), and nine ordinary chondrites, Sainte Marguerite (H4), Nadiabondi and Forest City (H5), Kernouvé (H6), Bjurböle (L/LL4), Elenovka and Ausson (L5), Tuxtuac (LL5), and Saint-Séverin (LL6) by MC-ICP-MS. Among the H chondrites, Sainte Marguerite cooled to below ∼1100 K within a few My at 4565 Ma and to ∼800 K at 4563 Ma.

Modeled durations range from hundreds to millions of years (Herwartz et al., 2011; Koenig et al., 2009, and references therein). Both studies demonstrate that the chemical complexity of fossilized bones led to a wide range of ages.

recently reported the first direct dating of sedimentary carbonates using the whole-rock Pb– Pb method. in Tectonostratigraphic Terranes of the Circum-Pacific Region (ed. G.) 375−389 (Circum-Pacific Council for Energy and Mineral Resources, Houston, 1985).

The success of this method depends on the chemical fractionation of U from Pb and the consequent variation in .

The Pb ratio for the common-Pb correction was ∼19.9.

The difference between the two estimates of common Pb causes an appreciable bias in the ages reported by Fassett et al.

Lead isotopic ages of chondrules and calcium–aluminum-rich inclusions. When these two groups of samples are combined, the isochron yields an age of 4568.5 ± 0.5 (MSWD = 0.90), which is our best estimate of the age of the Solar System.

The data from Forest City and Kernouvé show evidence of late-stage perturbation with resulting U/Pb fractionation.

Likewise, Pb isotopes in Tuxtuac (LL5) record a cooling history lasting from ∼4555 to 4544 Ma, which may indicate that the cooling history for the LL parent body was more prolonged than for the H parent body.