Problems with dating metamorphic rocks america adult mobile chat rooms
Thus under certain conditions Ar can be incorporated into minerals which are supposed to exclude Ar when they crystallize. envisage noble gases from the mantle (and the atmosphere) migrating and circulating through the crust, so there should be evidence of excess in crustal rocks and their constituent minerals could well be the norm rather than the exception.
Dalrymple, referring to metamorphism and melting of rocks in the crust, has commented: "If the rock is heated or melted at some later time, then some or all the In a recent study 128 Ar isotopic analyses were obtained from ten profiles across biotite grains in high-grade metamorphic rocks, and apparent Ar-Ar "ages" within individual grains ranged from 161Ma-514Ma.
Many geologists claim that radiometric “clocks” show rocks to be millions of years old.However, are all other rocks in the earth's crust also susceptible to "contamination" by excess emanating from the mantle?If so, then the K-Ar and Ar-Ar "dating" of crustal rocks would be similarly questionable.Radiometric dating measures the decay of radioactive atoms to determine the age of a rock sample.It is founded on unprovable assumptions such as 1) there has been no contamination and 2) the decay rate has remained constant.
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Petrologists also include the principles of geochemistry and geophysics through the study of geochemical trends and cycles and the use of thermodynamic data and experiments in order to better understand the origins of rocks.