Discordia — Atomica

: This point often corresponds to the age of a later metamorphic event or disturbance that caused the lead loss. Interpretation Guidelines

In the context of geochronology and U-Pb (Uranium-Lead) radioisotope dating, refers to a straight line on a Concordia diagram that represents a suite of minerals that have lost some of their daughter isotopes (lead) or parent isotopes (uranium) due to a geological event. Discordia atomica

: Grains that do not plot exactly on the Concordia curve are called "discordant". The degree of discordance can vary based on the intensity of the heating or fluid access that caused the disturbance. : This point often corresponds to the age

: Scientists use mathematical approaches like the "York" or "Ludwig" methods to perform a linear regression of measurements to define the Discordia line. The degree of discordance can vary based on

: For accurate results, "common lead" (lead not produced by radioactive decay inside the mineral) must be correctly subtracted. High-precision tools like SHRIMP (Sensitive High-Resolution Ion Microprobe) are often used to refine these 3D planar regressions .

A "proper guide" to interpreting a Discordia line involves understanding its two key intersections with the (the mathematically determined line where the age equals the Key Intercepts

: This point typically represents the original age of crystallization for the minerals. It indicates when the isotopic clock first started ticking.