Dear Sagar,

You probably are giving the present day Sr-isotopic ratios and eNd values I hope. Do you also have parent ratios of these isotopic systems? How large is this body of carbonatite? Did your sampling encompass entire length or width of this body? What are the associated rocks? Such information would be necessary for someone thinking of any possible interpretation, particularly because there is  large diversity both in isotopic ratios and concentrations.

Best Wishes!

LRK

• carbonatite magma is usually very rich with volatile and this leads to interaction with country rocks and can change the isotopic composition. It seems that  your magma is not primary. Some carboantite are form in subduction zone by melting of subducted sediments and can have variable isotopic composition.

Dear Sagar,

I find the extremely large range of the isotopic data and of the element concentration data remarkable. Does this range relate to one individual carbonatite body? or to a group of occurrences? With this large range of data, definitely more than one source will be involved in the formation of these rocks. 

The data  - sure that they are accurate? For example, a Sr ratio of 0.701 is lower than what I ever heard of for a carbonatite. This must either be an extremely old carbonatite, or there is a problem with the data. Are the Sr isotopic ratios calculated for the age of carbonatite emplacement? If so, the age estimate may be incorrect.

Other observations with the values you give - an epsilon Nd range of +10 to - 20 covers a full range from depleted mantle to old continental crust. Its highly unlikely to find such a range in an individual carbonatite body or even in a group of geologically related carbonatite occurrences. Then - Sr concentrations down to 20 ppm and Nd concentrations down to 1 ppm are again not plausible for a carbonatite magma. I would expect these concentrations much higher. I feel the set of data requires re-evaluation