low Th/U (

I am grateful for your answer. It will be very useful for my research.

I second what Daniela wrote. You can find examples of variable Th/U ratio in high grade rocks in my two papers on Rogland, Norway. JMG 2002 and Geol Soc London Spec Publication 2003

Here they are.

and the JMG 2002

Thank you very much Andreas. I am grateful!

Ms. Rubatto and Mr. Moeller, I am interested in papers that discuss the zircon grains characteristics which might help reavealing the zircon sources. Can you suggest some?

@Felipe Valença de Oliveira. If you are looking for articles describing zircon grain characteristics, I would recommend reding Corfu et al. (2003). Here is a link: http://rimg.geoscienceworld.org/content/53/1/469

Hi everyone!

Any research upon unusually high Th/U ratios (from 2 up to 6) ? I´ve found Timms et al (2006) study associating this feature to deformation in short period after crystallization in partial melting derived rocks. Does anybody have recommendations on this subject?

best regards

We had an abstract/poster at the Goldschmidt Conference 2006: Möller & Kennedy: Extremely high Th/U in metamorphic zircon: in-situ dating of the Labwor Hills granulites, Goldschmidt Conference Abstracts, A425. You can find the pdf by searching for the title in Google scholar.

Thank you so much Andreas.

For more information, kindly read the recent publication of Rubatto, 2017 (Zircon: the metamorphic mineral).

I recommend Daniela's answer

Best Regards

I apologize for being so late to chime in here.

I hope that you will find attached file

Cheshire Quartzite Zircons ©1963 SL Undergraduate Thesis .docx

to be of some interest, even though it does not touch immediately upon

the Th/U ratio in the question.

All best wishes, -Steve-

Apart from Th/U ratio CL images can also tell about whether zicon is igneous (with growth zoning) or metamorphic (weak CL) also read Protracted zircon growth paper by Singh, S (2018) in Geoscience Frontier

How a we differentiate rims in zircon formed in granite and migmatite when both form from melt and also how can we explain higher ages in rims compared to the cores...

If your granite is metamorphosed it can have the same metamorphic rims as zircons from migmatites and in fact both zircons are oscillatory zoned and therefore similar. Maybe more information would help us to answer. Look at CL in Broussolle et al., 2018 and we have dated migmatites and granites with metamorphic rims.

For the second matter. If I understand well you want to know how to interpret rims ages that are older than the cores? If so, firstly you should consider the error range of the method maybe both ages are the same within error range. In Broussolle et al., 2018 we also had this problem for one migmatite but the ages between rims and cores were the same within the error range.

If you have few grains that have this problem I would suggest not to consider them.

Thank you Broussole .Yes there are only 2 grains which give me such ages . I will look into your suggested papers.

Thanks very much.