U pb age dating

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The isotopic composition of oxygen, hafnium and other elements in the zircon represents a unique window into the earliest stages of Earth evolution.They indicate that liquid water was present on the surface of our planet early on in its history.For those minerals, the non-radiogenic Pb can be safely neglected (at least for relatively young ages), so that we can assume that .This assumption cannot be made for other minerals, young ages, and high precision geochronology.Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned, sector zoned, planar zoned, and patched zoned ones.Zircons formed in different geological environments generally have characteristic internal structures.Therefore, interpretation of zircon U-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.

Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions.The probability distribution of a representative sample of zircon U-Pb ages from a detrital population can serve as a characteristic fingerprint that may be used to trace the flow of sand through sediment routing systems.As a provenance tracer, zircon U-Pb data are less susceptible to winnowing effects than conventional petrographic techniques.This means that a mineral (of age T after its formation (e.g., during metamorphism), after which the system closes again and further accumulation of radiogenic Pb proceeds normally until the present.On the concordia diagram of multiple aliquots of a sample, this scenario will manifest itself as a linear array of datapoints connecting the concordant line) can be used to estimate the crystallisation age, whereas the lower intercept yields the age of metamorphism.

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