Problems with radiometric dating techniques
On the upper left branch of this reaction series, olivine, the first mineral to form, Ml] react with the remaining melt to become pyroxene.This reaction will continue until the last mineral in the series, biotite mica, is formed.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.Oftentimes the rate of cooling occurs rapidly enough to prohibit the complete transformation of calcium-rich feldspar into sodium-rich feldspar.In these instances, the feldspar crystals will have calcium-rich interiors surrounded by zones that are progressively richer in sodium.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.
This calls the whole radiometric dating scheme into serious question.
Bowen also demonstrated that if a mineral remained in the melt after it had crystallized, it would react with the remaining melt and produce the next mineral in the sequence shown in Figure 3.6.
For this reason, this arrangement of minerals became known as Bowen's reaction series.
Most scientists today believe that life has existed on the earth for billions of years.
This belief in long ages for the earth and the existence of life is derived largely from radiometric dating.
Ordinarily, these reactions are not complete so that various amounts of each of these minerals may exist at any given time.