Sm-Nd isotopes can be use for petrogenesis but what about dating the ultramafic rocks of ophiolite complexes....I have came across very less research paper of these isotopes used for petrogenesis but not for dating......
Can anyone share publications or expertise in the field of isotope studies of these rock types....
Dear Dr. Nayak, I've attached an article about Sm-Nd dating technique. Also, if you have gabbro rock samples, you could dating it using U-Pb on zircon, probably, will need 2 to 5 kg, and you can use SHRIMP or LA-ICP-MS methods.
Whole rock Sm-Nd Dating can be done ..but the problem is that peridotites are mainly residual in nature so that we can not get the exact crystallization age of this type of residual peridotites. First , we should check whether that peridotites are residual or not.
If you are sure that peridotites of your samples are not residual solid, Sm- Nd dating can be valid and you can use that age as crystallization age.
Sm-Nd dating has some limitation that it is not suitable for dating of young age like Recent, Cretaceous, Tertiary. etc.,..PRECISION WILL NOT BE GOOD because half life of Sm-Nd decay system is very long. So, it is more suited to dating the rock of older formation like Archaean.
For these reason, it is better to know your peridotites that you want to date are older formation or younger formation before start.
Thanks Kingson....I have gone through your recent paper.....congrats for the good work done on MNO... My samples are mostly from cretaceous...So I think I better go for the Nd isotope analyses (from bulk rock ) for petrogenesis than dating of these ultramafics rocks.....
Thanks Leonid for sharing you expertise on Sm/Nd isotope studies....I have no garnet in my samples...So probably I will go for Nd isotope studies purely for petrogenesis from the bulk rock instead of separating the minerals form these rock types.......
Also would like to request you to share any publication on isotope studies of ultramafic rocks of ophiolite complexes if you have any??...
If you have a Ophiolite Complex, you have several kind of different rocks that you could dating like gabbro and basalt units within this complex. More recently the U-Pb geochronology on the baddeleyite mineral was successfully applied in mafic and ultramafic rocks, but you can make 40Ar/39Ar geochronology in a special mineral or whole-rock.
Thank Elisabeth for sharing your views but I am interested in ultramafic rocks.
Dear Maojiang Wang,
Regarding your absolute error on isochron, that high errror may be due to the analytical problem...need to be check the parent isotope (147Sm/144Nd) (i.e., Sm, Nd concentration). Probably, this error will give the high error to the isochron. recheck the process of ID METHOD and their analysis.
Yes, it can, but you need to do very careful separation of the different phases to increase the Sm/Nd spread.
Using Sm/Nd for dating in this case can be quite complicated. Except if you want TDM ages, for example. Usually the isochron will have a considerable error within its values.
The following references may help you
Mørk, M. B. E.& Stabel,A.:Cambrian Sm-Nd
dates for an ultramafic intrusion and for high-grade metamorphism on the Øksfjord
peninsula, Finnmark, North Norway. Norsk Geologisk Tidsskrift,
Vol.70, pp. 275-291. Oslo 1990.ISSN 0029-196x.
Contributions to Mineralogy and Petrology
March 1992, Volume 110, Issue 1, pp 57–67
U-Pb zircon and Sm—Nd geochronology of mafic and ultramafic rocks from the central part of the Tauern Window (eastern Alps) ----Albrecht von Quadt
Dear Kingson
Which method you have used for processing the samples for Nd isotope studies???... there are five different methods listed in your department....
Can you please suggest in which method we can get only the concentration of Nd isotope for petrogenesis of ultramafic rocks....
As mentioned above multiple times, ultramafic rocks are usually tough to deal with when it comes to dating. Especially when you have (1) mantle xenoliths, or (2) bodies of dismembered ophiolites, where you have to date ultramafics directly with no opportunities to deal with hosting/associating lithologies. Major problems are (1) often low LREE contents (so you need to use large sample amounts to elute a minimum necessary Nd for analysis that is not convenient), and (2) possible incipient melting or interaction of ultramafics with mantle or crustal fluids that lead to selective or complete resorption or - vice versa - crystallization of new phases via metasomatic reactions; all this leads to isotope disequilibrium and nonsense results. To deal with the first problem, many labs modify techniques to use a lower amount of Nd (and total sample as well), e.g., please see the paper attached.
Dear Sergei
Thank You for sharing you expertise on the Sm-Nd isotopes on ultramfic rocks..... But could you help me, what best can be done for these type of rocks from ophiolite complexes... I could not able to download the paper you have attach.
Dear Dr. Ranjit
For ultra-depleted peridotites, you can follow the methods which i have explained in my recent paper in chemical geology and other one I am attaching here a LINK. Anyway, you should know the concentration of Nd in your samples from ICPMS OR any. Around 200 ng of Nd is required for good measurement in TIMS. Accordingly, you can take your sample amount for digestion. Your sample amount in gram which you want to digest for Nd isotope should have around 200 ng. Acordingly you calculate ng of Nd from your Nd concentration from the samples.
Cheers....!!!!
http://www.sciencedirect.com/science/article/pii/S0016703796002803/pdf?md5=65c9de0ede31ab0d509aea6119224fea&pid=1-s2.0-S0016703796002803-main.pdf
Dear Kingson
Thank You for the information....The Nd concentration is below 0.3ppm in my samples.I cannot download or access the link that you have provided..... If can share you contact details, it will be very helpful for me to contact you directly......
Hope you don't mind....
Have a great day
Dear, Dr. Ranjit,
Here is the pdf file attached. Please find out.
ok sure, we can discuss about that directly. 7598176184... this is my current contact no.
Email ID: [email protected]
Hi Ranjit,
There are several useful suggestions already outlined by others. My two cents are the attached paper that might be of interest to you.
Good luck!
Arshad
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