Potassium has three naturally occurring isotopes: 39K (93.3%),40K (0.01%) and 41K (6.7%). Naturally emerging 40Kdecays to secure 40Ar (11.2%) by electron capture and also by positronemission, and decays to steady 40Ca (88.8%) through negatron emission;40K has a half-life of 1.250 x 109 years. The decayof 40K to 40Ar is generally used as a method for datingrocks. The conventional K-Ar dating technique depends on the presumption thatthe rocks consisted of no argon at the moment of formation and that every thesubsequent radiogenic argon (i.e., 40Ar) to be quantitativelyretained, i.e., closed system. Minerals room dated by measure of theconcentration that potassium, and the quantity of radiogenic 40Arthat has accumulated. The minerals the are best suited for date includebiotite, muscovite, and also plutonic/high great metamorphic hornblende, andvolcanic feldspar; totality rock samples from volcanic flows and shallow instrusivescan likewise be date if they are unaltered (Faure, 1986). For a discussionof K-Ar dating watch Dalrymple and also Lanphere (1969), Faure (1986), and Dicken(1995).
Outside that dating, K isotopes have actually been used extensively in studiesof weathering (Moldan and Cerny, 1993); K isotope have also be offered fornutrient cycling studies because K is a macro-nutrient compelled for life.
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Source that text: This evaluation was assembled by Dan Snyder, primarilyfrom Faure (1986).References
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