Hf isotope is positive +7 TO +10 even higher +14 in both types of rocks one is I-type which is older and other is A-type which is younger. I-type granites formed from lower continental crust and A-type formed in the upper continental crust, what will be the source in your opinion. magma source could be same or different, please any idea?
Dear Leonid Shumlyanskyy thanks for kind reply,
1. data is absolutly correct and i dont have Nd Whole rock data ,just Hf, 2. the ages are different for Atype 735 to754 Ma and for biotite granite ages ranging from 812 to 810 and considered as old then Atype...but if we say same source it will be not correct ,mean while ehft in both granites positive which indicates juvenile crust but REE and HFEE IS NOT supporting that they are from juvenile crust, what is your opinion about these rocks, have you counter such kinds of rocks ever, plz comment...
Dear Leonid Shumlyansky, i checked and confident on Hf results but surprising results in samples pushing me to more investigating them, i also have gone through your paper it is good and helpful too for me, reference (Precambrian Research 260 (2015) 39–54), let's see what conclusion we made for results.
Thanks for reply and information.
Regards ABDUL
Dear Abdul,
Perhaps this information will be useful to you.
The partial melting of more mafic source rocks, rather than the fractional crystallisation of more mafic magmas, is favoured for the origin of most of the I-type granites (Chappell et al., 2012).
Example: I-type granites originate from the lower crust that was quite juvenile in the Paleozoic (Yu et al., 2016)
References:
(1) Chappell, B.W., Bryant, C.J., Wyborn, D., 2012. Peraluminous I-type granites. Lithos 153, 142–153.
(2) Yang Yu, Min Sun, Xiaoping Long, Pengfei Li, Guochun Zhao, Alfred Kr¨oner, Arnaud Broussolle, Jinhui Yang, 2016. Whole-rock Nd–Hf isotopic study of I-type and peraluminous granitic rocks from the Chinese Altai: Constraints on the nature of the lower crust and tectonic setting. Gondwana Research, doi:10.1016/j.gr.2016.07.003
Best regards
Roman
- Dr.Leonid and Dr. Roman thank you very much for sharing some good papers ..definatly i will go throu these shared papers and i also gone through sone good papers and git alot of help. these papers shared by Dr roman also good one ...
Thanks to all my RG Geoscientists group friends...
Dear Br Shakoor Sb
Very informative comments made by researchers. Still I feel for some more comments. May I ask about the area where you collected samples? I may guess about your area perhaps nagar parkar sindh. Wish u good luck with your work.
Dear Abdul,
we also got positive eHf values between +3 and +8 for granitic rocks of the Piedra Alta Terrane (Oriolo et al. 2016 Precambrian Res 280:147-160). However, I also agree that values around +14 are exceptionally high and should be carefully evaluated. In any case, the the Hf fingerprint shows a clear juvenile signature. Which is the setting of those granites? Could it be related to an island arc?
Regards
Dear ijaz your guess is wrong, these rocks belongs to SC not from NP.
Dear Sebastian. Thanks for nice comments and yes these rocks belongs to different settings, what we did, as A_type WPG and I-type VAG settings , you may see the trend of elements as REE, LREE and HFSE clearly indicating to a different source or setting.
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