# Radiometric Dating 2 Pb-Pb Isochron Dating Method

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This approach to Pb-Pb isochrons makes use of 2 of the natural radioactive decay series, the uranium-238 decay series & the uranium-235 series, which are related to each other by that the isotopic ratio (238U = 137.88 x 235U) was found to be consistent for Earth, moon & meteor rocks. The two series proceed to different final lead isotopes: 238U-206Pb & 234U-207Pb. There is a third lead isotope, 204Pb, that is not formed in radioactive processes & can therefore be used as a reference. at…

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Lead-lead dating (Pb-Pb dating) is a method for dating geological samples, normally based on 'whole-rock' samples of material such as granite. For most dating requirements it has been superseded by uranium-lead dating (U-Pb dating), but in certain specialized situations (such as dating meteorites and the age of the Earth) it is more important than U-Pb dating.

Pb-Pb Isochron Dating: There are a number of useful isotope systems which constitute clocks in the rocks and are useful for geologic dating. But if asked what is the most reliable and precise method for dating the Earth and meteorites, Brent Dalyrymple would point to lead isochrons. He calls the lead method "the hourglass of the solar system". The current approach to plotting Pb-Pb isochrons is referred to as the Holmes-Houtermans method. at gsu.edu

Holmes-Houtermans System for Lead (Pb) Isochrons: The lead-lead isochron method for determining the age of ancient rocks including meteorites is generally thought to be the most reliable and precise method for such dating. Dalrymple calls the lead method "the hourglass of the solar system". Many years of painstaking research has gone into establishing what is commonly called the Holmes-Houtermans System. at gsu.edu