It has been observed that when I make a plot for Isochron diagram using Nd isotope data it shows very scattered distribution and unable to make the best fit line. So kindly suggest me how to find the age and (143Nd/144Nd)i.
You may be trying to get an age of the rock, in which case you are trying to make a "whole-rock" isochron. It is likely that the spread in 147Sm/143Nd is therefore not very large. I would second Le Zhang's suggestion that for better precision you need to do mineral separates, AND for the very best precision do the measurements by TIMS for isotope dilution.
Thank you sir for your answer. I have analysed REE, Trace and 143Nd/144Nd of all samples. But unable to date rock age. Kindly let me know how to select minerals. My samples are Volcanics and Gabbro.
Hello. Choose minerals according to Sm and Nd partitioning coefficients: the bigger difference in them, the bigger chances that isotope ratios give you big spread. Usually Grt, Pl, Amf and Px are chosen. Grt is particularly useful, but in Your case garnet is probably absent. I'd choose Amf and Pl for volcanics and Px and Pl for gabbros.
Thank you all for your quick response and suggestions. Kindly refer few books and papers for better understaning of the same.
Thank you Andrey Arzamastsev sir for your suggestion,
I don't know the age of the rocks. We have not enough analytically facilities for isotope analysis and depend on the other institutes. I sent the samples for Nd and Sr isotope analysis. But I have received only Nd data. The Sr data will be obtained later due to some technical problem in that institute. Therefore I am trying to date the rock by using Nd isotope and need help for the same.
I concur with the views raised above that Sm-Nd dating is suitable for separated minerals (pl, cpx, opx, ol, amph, phlog, garnet, apatite) or cogenetic suites of rocks that have Sm/Nd ratios that vary sufficiently to define a slope of an isochron in a correlation diagram 143Nd/144Nd versus 146Sm/144Nd. Just to add that Nd-Sm method is more reliable than Rb-Sr method, and it's suitable especially when the system had not remained closed Rb or Sr.
Thank you Uriah Alexander Lar sir for your valuable suggestion.
From your opinion now i need to separate the minerals (pl, cpx, opx, ol, amph, phlog, garnet, apatite) for sm and Nd partition coefficient for all rock types and after that I shall be able to date the rock.
Sir, can I use the values of mineral Opx (found as a nodules/xenolith in alkali basalt in the same area) for partition coefficient. I had picked the opx from the basaltic rock and analysed.
Yes, Le Zhang sir, I mean to say choosing of mineral for partition coefficient. From where i get the value of a mineral. Can i use opx, plag etc values of Rollinson, 1993, Arth, 1976 etc or we will obtain it from after analysing individual mineral grains of all rock types. I have analyzed above mentioned Opx minerals so, i asked. Kindly clear my doubts. How to calculate partition coefficient.
Mister Chaitradhar Taye, partition coefficients will only give you the impression of how elements are distributed in regards to one another. I don't think that you need actual values for your particular system in order to get the idea which minerals to chose. Another approach comes from the structures of the rock: phenocrysts and matrix minerals will have different isotopic composition (but you have to be aware that there is a possibility of contamination and phenocrysts might be interpreted as xenocrysts, in this case, you'll get two parallel isochrons). In any case, you cannot know for sure until you acquire data. But even in case of heavy contamination by crust material you should be able to put some constrains on timing.
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