انجمن متا: طراحی سایت و سئو - دانلود قالب و تم - کریپتو

age. In practice, the 238U/204Pb ratio may well have been disturbed by recent alteration of the rock because uranium is highly mobile in near-surface environments. For this reason it is more common to combine the two uranium decay schemes and plot 207Pb/204Pb against 206Pb/204Pb; the slope of an isochron on this plot is a function of age.
Isochron dating has been used to determine an age of 4.55 billion years for the Earth and the solar system by dating iron and stony meteorites (Fig. 2). The position of data along the isochron is a function of the U/Pb ratio. The iron meteorites are particularly important for defining the initial lead isotopic composition of the solar system since they contain negligible uranium. The meteorite isochron is commonly termed the Geochron.  See also: Earth, age of; Geochronometry; Meteorite