Hi Harshita,

Your question needs elaboration. As far as instrumentation and methods are concerned, oxygen is extracted from the rocks and minerals by reacting it with bromine pentafluoride or chlorine trifluoride under high temperatures (upto 700 degrees C). There are two popular techniques e.g., Nickel tubes or laser. Purified oxygen or carbon dioxide is measured for oxygen isotope ratios using isotope ratio mass spectrometer. Elaborate your question and you will get better feedback.

Hi Harshita

Hope u r fine.

The Oxygen isotopes are temperature dependent. The heterogeneity observed by you may be due to the fluctuation of temperature during precipitation. Please Elaborate your question for better feedback.

Well I am not an expert but I have seen oxygen isotope heterogeneity caused by secondary fluid flux in metamorphosed carbonates. In other words, the pristine oxygen isotope signatures can get modified by deformation/metamorphism/ metasomatic processes. I guess you need to be more specific (rock type, tectonic back ground) to get more clear cut answers from the experts.

Hope you are doing great and cheers

Maybe the best solution is to determine in situ oxygen composition on different phases, but to my knowledge, a not common line is requested, i.e., an excimer laser connected with a proper microscope and to a MS. See, for example, among others:

1. Farquhar J. & Rumble III D.(1998) Geochim. Cosmochim. Acta, 62(18): 3141-3149.

2. Hu G., Rumble D., Wang P.L. (2003) Geochim. Cosmochim. Acta, 67(17): 3101-3117.

3. Rumble III D., Farquhar J., Young E.D., Christensen C.P. (1997): Geochim. Cosmochim. Acta, 61(19): 4229-4234.

4. Wiechert U. & Hoefs J. (1995) Geochim. Cosmochim. Acta, 59(19): 4093-4101.

Of course, you have to take into account isotope fractionation due to temperature, for different phase. And, up to now, fractionation factors among the main minerals are known, so that you can overcome this problem. Have you got any indipendent estimate of temperature equilibration (?) of your rocks?

Hi Harshita,

It would be helpful, as others have said, to have some more information about the composition of your rocks,the scale on which you are trying to identify this heterogeneity and the current identified maximum metamorphic grade (if any) that these have experienced. I have experience of quite complex patterns of oxygen isotope heterogeneity through two separate phases of fluid interaction in limestone. However this is on a m scale so may not be relevant to you. This is documented in

Horák & Evans (2011), Geological Magazine, 148, 7-88. 

Thank you all !!

Oxygen isotope heterogeneity in calcareous rocks (limestone) in micron scale is to be done.The rock is not metamorphosed.  

The detail technique of analysis including the instrumentation and methodology is required. 

So, I think that the unique way is to perform point in situ analysis via excimer laser. Reading the quoted bibliography, you can easily find details on instruments, and probably also some labs to contact and ask them whether they are able to answer your specific questions. I don't know (I'm not updated, unfortunately) whether it should be possible perform in situ analyses also with a Nd-YAG source, as the main problem during in situ analysis is avoid isotope fractionation during microsampling via a laser source

P.S. So, you will analyze only calcite, or also something else?

Harshita

Oxygen isotope heterogenity in case of limestone can be ascertained by mass spectrometer. The variation can  due to fluctuations in conditions of environment of deposition (both marine or freshwater). Further diagenesis  can also contribute to the variation..

Rock chemisrty and geochmical analysis and carbon dating of rock may be  one of the clue to your queston. what is the trace elements present in the rock.what is the x-ray diffraction results indicate the variation  in compostions of mineral constituients. what is process  of formation of the rock. if you have instrument to study related to isotopes of oxygen than  also..it is only possible through modelling  of experimental results.