Rotta, R.B., Evolutionary explanations for anomalous radiocarbon in coal? CRSQ41(2):104–112, September 2004. 14C in coal was reported by: Baumgardner, J., Humphreys, D., Snelling, A. and Austin, S., The Enigma of the Ubiquity of 14C in Organic Samples Older Than 100 ka, Eos Transactions of the American Geophysical Union84(46), Fall Meeting Suppl., Abstract V32C-1045, 2003. And also: Lowe, D., Problems associated with the use of coal as a source of 14C free background material, Radiocarbon31:117–120, 1989.
Giem, P., Carbon-14 content of fossil carbon, Origins51:6–30 (2001), grisda.org.
From what I am getting from this article it appears they are citing contamination to explain the C 14.They are wise enough not to claim that contamination came from within the diamonds since it is very hard to internally contaminate something that hard but they claim that the contamination came from hands or the air. which would be very irresponsible of the person doing the testing and it would have to happen in every sampling of diamonds taken because C14 is in every sample. Then they go on to mention well just how did the C14 get in diamonds in the first place since they are created very deep in the earth and C14 is created in the air.For one I wonder how they know there is no C14 deep within the earth.Saltwater in crushed granite has been found deeper in the earth then water or crushed rock should be since the great pressure should prevent water from seeping down as far down as it was found and what would crush rock at that depth? The point being we don't know as much about whats deep in the earth as we think we do but just because we don't know how C14 got into diamonds that does not answer the question as to How is it still there after billions of years? I had always thought diamonds were super heated and compressed coal? But how it got into the interior of the earth I don't know either.As to their comments on tree rings and ice layers I can supply articles verifying that Bristlecone Pines often produce double rings in a given year due to drought occurring in summer so that the tree shuts down and a ring is produced in spring and early fall.Ice layers are only assumed to be annually produced but are actually produced with each separate snow fall.None of these side issues of course has anything to do with why C14 is still in diamonds after billions of years.Even in sedimentation experiments varves can be rapidly produced in a flowing current where grain size is rapidly sorted and deposited simultaneously.taking each layer weather it's soil or ice as being annually produced is a guess and can be shown to be unnecessary.layers can be laid down much faster then that.
If I am missing the point of the article please point it out to me.I still see no explanation of how C14 can last millions of years or how a diamond can be contaminated.As for whats in the center of the earth your guess is as good as mine.I doubt what is there either of us would be able to accurately guess at.
I probably should have put more paragraphs in this but I never was very good at that even in school.