Leedsacukdynamicearthdatingclosurehtm wednesday 15

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Unformatted text preview: ating/closure.htm Wednesday, 15 August, 12 Closure Temperatures Cooling Curve Temperature (1) TB = blocking temperature or closure temperature TB (2) Time Dauhter isotope/parent isotope Accumulation Curve TB Time Wednesday, 15 August, 12 From Dodson (1973, 1979) and Rollinson (1993) Common Minerals Used for U-Pb Dating Mineral Formula Rock Type Closure Temperature (oC) Zircon ZrSiO4 Most >800 Baddeleyite ZrO2 K,C,UM,M,A 725 Monazite CePO4 SG,GP,PS,HV 700 Titanite CaTiSiO5 Most,SK 600 Rutile TiO2 GP,GN,HV 400 Perovskite CaTiO3 K,C 650 Apatite CaPO4 Most 100 Allanite CaFeAl2Si3O12 IG 650 Xenotime YPO4 SG 650 Thorite Th(SiO4) GP,SG 650 K = kimberlite, C = carbonatite, UM = ultramafic, M = mafic, A = alkaline, SG = S-type granitoids, IG = I-type granitoids, GP = granitic pegmatite, HV = hydrothermal veins, GN = granitic gneiss, PS = pelitic schist, SK = skarn. From Heaman and Parrish (1991) and Richards and Noble (1998) Wednesday, 15 August, 12 Concordia Diagrams • U has two isotopes and two decay schemes, hence, we get independent checks on the age of rocks. • If the two ages (and Pb-Pb age) are coincident they are CONCORDANT; i...
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This document was uploaded on 03/06/2014 for the course ES 4502 at Memorial University.

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