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Earth and Space Sciences · 术语表

什么是 Concordia, discordia, intercepts, Tera–Wasserburg diagram?

又称: concordia · discordia · upper intercept · lower intercept · Tera--Wasserburg diagram

Definition 13.1 University Earth and Space Sciences — Year 3 · 第 13 章 — Advanced Geochronology

The concordia is the curve of the (x,y)(x, y) plane on which the two uranium–lead ages are equal. A discordia is a straight line along which discordant analyses of one population of crystals are aligned; its intersections with the concordia are the upper intercept (the older) and the lower intercept (the younger). The Tera–Wasserburg diagram plots X=238U/206Pb∗X = {}^{238}\mathrm{U}/{}^{206}\mathrm{Pb}^* against Y=207Pb∗/206Pb∗Y = {}^{207}\mathrm{Pb}^*/{}^{206}\mathrm{Pb}^*.

(a) The concordia, with its ages in millions of years, and five invented discordant zircons of one granite (red; their error ellipses are smaller than the symbols), aligned on a discordia (dashed) that meets the concordia near 311 and 100\, Ma. (b) The same zircons and line in the Tera–Wasserburg diagram, where a discordia is still a straight line.
(a) The concordia, with its ages in millions of years, and five invented discordant zircons of one granite (red; their error ellipses are smaller than the symbols), aligned on a discordia (dashed) that meets the concordia near 311 and 100 Ma100\,\mathrm{Ma}. (b) The same zircons and line in the Tera–Wasserburg diagram, where a discordia is still a straight line.
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