is it possible to use impurities as a tool for Isotope dating?
For example can we use the K+ ion for dating with K/Ar system? can fission track study of the entire crystal help us for age determination?
Dear Mr. Ovissi,
Potassium is not an element accommodated in the lattice of quartz. Thus you might consider K bound to impurities such as mica flakes or any other K-bearing mineral hosted by quartz. Given the mineral has not suffered any change in the K/Ar system you will get an age of the K mineral but not of the quartz.
Best regards
H.G.Dill
1) Quartz has no K in the lattice for K-Ar, and typically has numerous fluid inclusions which may not have closed system behaviour. Dating quartz with directly by K-Ar on fluid inclusions is not typically reliable.
2) Quartz has no U for fission track dating. This will not work.
You need to look at the other minerals associated with your mineralization. You should look for something K-bearing like adularia, alunite or mica. Fine grained sericite could work if you analyse it with K-Ar or encapsulation Ar/Ar.
You can also look for Titanite or apatite in a mineralised system and date with U-Pb
Or what works well is Re-Os on molybdenite
So the question is really, what is your mineral assemblage? And to be sure that you are dating the right thing with the right tool, you need a detailed paragenetic sequence.
Cheers
Dear Dr. Roelant Joost Van der Lelij
Thanks for your kind answer. In my case, studying opal, chalcedony and quartz crystals, forming as a consequence of hydrothermal mineralization, one can see a host rock, andesite or basalt, and a cavity is compeletely or partialy filled by different forms of silica from crystalline to amorph varieties. So all you have is silica and there is no mineral assemblage. Is there any procedure for determining the age of quartz mineralization or I should give up?
By the age of the host rock, we can estimate the mineralization age younger than host rocks, but how we can determine the absolute age of mineralization?
Thanks for all comments,
As Dr.Harald G. Dill mentioned we can use K-bearing minerals hosted by quartz, suffering no changes in K/Ar system during geological history, for dating by K/Ar method. But this age is related to those minerals and not to quartz.
On the other hand the quartz mineralization is very common in various types of geological environments. You can have several phases of quartz mineralization and it is very difficult to distinguish quartz mineral paragenesis. Another problem is in my case I have some veins and cavities filled just by different varieties of silica and there is no mineral paragenesis.
As you know there are some impurities in quartz such as Fe3+, Al3+, K+, Li+, fluid inclusions, tiny pieces of other minerals, etc. Can I use one of these impurities as a key for opening this locked door?
Natural smoky quartz exhibits ESR signals and also TL peaks having blue emission. The effects are caused by electron/hole trapping and can be induced artificially by various radiations. The traps are filled slowly by natural background radiation, and are of interest for dating (McMorris, 1971). The paper is attached.
This paper has a good idea for dating the smoky quartz, but it has published about 44 years ago. Is there any new data about this method?
Dear Sirs,
Recently I read some papers, working on dating quartz by 40Ar/39Ar method, using Ar gas dispelled from fluid inclusions. I have attached three papers related to this issue. I will appreciate your comments.
Best Regards,
Masoud Ovissi
It is very difficult to estimate directly the age of quartz as it has various geologic setting. The best method is to use the paragentic sequence of crystallization with the reference to well-identified minerals associated with the quartz
I think if you take inclusion fluid from the quartz the same time you can defined and genesis etc.....
Quartz related to mineralisation will usually contain submicroscopic phengitic muscovite and have tiny fluid inclusions. See van Moort, JC and Aung Pwa 2005. The use of quartz concentrate (acid insoluble residue)as a sample medium in lithogeochemistry and regolith exploration studies. GEEA 5:267-277. There is no reason why K-Ar dating would not work.
Age dating with TL, EPR etc will not work because the amount and nature of fluid inclusions and trace element contained in the quartz is the main factor influencing the intensity of the signal. See eg van Moor, JC t et al 1992. Relations between trace element content and paramagnetic properties of a banded smoky quartz crystal. Proc Goldschmidt Conference Preston VA, May 1992 : A-115.
Dear Sirs,
Many thanks for so useful comments.
Best Wishes,
Masoud Ovissi
Dear Masoud,
Probably by now you have solved your question. If not, you can try opal dating with U-Pb (if older than 400 kyr) or U-series (if younger than 400 kyrs). Here are some papers about U-Pb opal dating.
Cheers,
Alejandro
I've just seen this interesting discussion and I remember that back in the 80s there were quite promising intensions to data hydrothermal quartz with the Rb-Sr system. Actually these elements are mainly trapped in fluid inclusions but the system remains closed. Check Horn et al 1986, Chemical Geology: Volume 58, Issue 3, Pages 259-272
Thermoluminescence dose rate data and disequilibrium in the decay series ( U-series disequilibrium , secular equilibrium in the decay series).
Dear José,
Many thanks for your answer that showed me new ways to find the answer.
Kind Regards,
Masoud
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