Uranium lead dating method dating for professionals in manchester
The general idea is that many different minerals are formed, which differ from one another in composition, even though they come from the same magma.
The mineral makeup of an igneous rock is ultimately determined by the chemical composition of the magma from which it crystallized.
As the crystallization process continues, the composition of the melt (liquid portion of a magma, excluding any solid material continually changes.
For example, at the stage when about 50 percent of the magma has solidified, the melt will be greatly depleted in iron, magnesium, and calcium, because these elements are found in the earliest formed minerals.
Evidence of this type led them to look into the possibility that a single magma might produce rocks of varying mineral content. Bowen discovered that as magma cools in the laboratory, certain minerals crystallize first.
Most people are not aware of the many processes that take place in lava before it erupts and as it solidifies, processes that can have a tremendous influence on daughter to parent ratios.
The following quote from The Earth: An Introduction to Physical Geology by Tarbuck & Lutgens, pp.
55-57, (1987), gives us an idea of the tremendous complexity of the processes that occur when magma solidifies.
Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger.
This calls the whole radiometric dating scheme into serious question.