Laser Ablation-Inductively CoupledPlasma-Mass Spectroscopy (LA-ICP-MS) - Science topic

And:

Jie Lin et al. Calibration and correction of LA-ICP-MS and LA-MC-ICP-MS analyses for element contents and isotopic ratios; Solid Earth Sciences,Volume 1, Issue 1, June 2016, Pages 5-27

Hi Md. Zakaria, this completely depends on your research purpose (and your budget). You need to know, at least, which mineral(s) you want to target and what decay system(s) you want to date. The answers to these two general questions would lead to completely different directions. For example, LA-ICP-MS is suitable for zircon U-Pb dating, but is not for zircon (U-Th)/He.

For U-Pb system, I would say LA-ICP-MS is the most efficient and cheapest instrument to use (e.g., for U-Pb detrital zircon), but it is less precise when compared to TIMS and SIMS. It would be even more complicated (e.g., sample preparation) for other decay systems such as Ar-Ar and K-Ar as the analysis would be more time consuming (~6-12 months per sample) and more expensive.

So there is no answer to your question "which is better", as different instruments and decay systems have their own advantages and limitations. Which one is better depends on what questions you want to resolve.

So, according to my table of isotopes (Pure Appl Chem 1989 vol 63 no7 p991-1002), ⁴⁸Ti is 73.8% of total TI composition, but there is also an isotope ⁴⁸Ca which represents 0.187% of total Ca.

Could you be getting some ⁴⁸Ca in your ⁴⁸Ti measurement?

It probably won't cost you any extra time or money to measure ⁴⁷Ti (7.3%) or ⁴⁹Ti (5.5%), neither of which have isobaric interferences.

Perhaps ⁴⁶Ti (8.0% of Ti) with ⁴⁶Ca (only 0.004% of Ca) might be an option too.

I haven't used an LA-ICP-MS, so there may be some other things that other users might know about.

Not yet, our LA-ICP-MS started to work, but the quality of measurements is

unstable

Trace element abundance plots (spidergrams) are used to illustrate the rare earth element or mantle incompatible trace element contents of a sample. The order of trace elements is usually shown in the order of decreasing ionic radii. In the case of the REE, where the lighter elements such as La have the larger ionic radii (due to the lanthanide contraction with higher atomic numbers), the LREE are shown on the left and the HREE on the right part of the spidergram. Elements concentrations below detection limit cannot be plotted. The computer program plotting the spidergram usually interpolates their values between its neighboring elements.

What is needed to better assess this age difference is the temperature of crystallization of both minerals and their sensitivity to subsequent heating/chemical induced modifications at post-crystallization stage of the granite. Cassiterite is an oxyde mineral that is quite stable once crystallized, as for monazite, a phosphate, it can be more easily recrystallized via fluid or high temperature events affecting the granite. The spread of 70 Ma in monazites seems to reflect that one or more events induced partial Pb loss in the minerals. Cassiterite is more resistant and has possibly a more 'locked-in' age. You will need to verify the stability of both minerals to metamorphic and hydrothermal events that happened in and around the granite to support your interpretation of these age ranges. You need also to assess the crystalline capacity of each mineral to retain U and/or Pb in its structure, the more 'similar' in ion size and valence an element is to the other (eg. Sn vs Pb) the more likely the crystalline structure will retain the new element during a metamorphic event.

Sometimes, backreflection or emission from a sample may damage the optics inside the laser resulting in a power drop. Use of an optical isolator is usually recommended to prevent backreflection into the laser.

Hello and good health, I am a doctor of petrology in Iran and I have worked on the faults of northwestern Iran and the volcanic regions of Iran and Turkey, especially Sahand volcano, and I have several articles. I will be happy to work with you and help you. I am waiting for your message. Thank you so much

Quartz ablation and analysis by LA-ICP-MS is possible with both nanosecond and femtosecod lasers. See the paper attached.

One possibility is that the heavy atoms peak signals (Au, U) have shifted in comparison with the lighter elements (Fe, S, Ag) over time. The machine may be reading on the side of the heavy element peaks instead of right onto the top of the peak itself. If you can access one, try a gold standard (or any other very heavy element) to see if your peaks are read at the right place in the spectrum by the software. Another possibility is that one piece of the equipment is getting contaminated with deposits (gold plating?) and interferes with the reading of the heavy element peaks .

There are several labs in Canada to perform such analyses:

- Canadian Centre for Isotopic Microanalysis, U of Alberta

- Geobiology Isotope Lab, U of Toronto, Dept of Geology

- Isotope Science Lab, U of Calgary

also Carleton Univ. and U of Waterloo

Hello,

unless you sample is in the same matrix as the reference standard, then I wouldn’t count on laser ablation for quantitative data (in comparison to sample digestion). I agree with the fact that you should polish as fine as you can to avoid any difference in ablation rate

Yes, my coauthors, Niki Wintzer (USGS) and Mark Schmitz (Boise State University) have dated hydrothermal scheelite using LA-ICPMS in U-Pb system as well as with ID-TIMS. Material is from Stibnite District, Idaho. We are writing a manuscript (in revisions) for Economic Geology. Also see abstract (Wintzer et al) from GSA meetings in 2016, 2017. However, as a quick word of caution, the LA analyses using glass standard proved to be not as accurate as results from TIMS (U-Pb). A correction factor was calculated to enable better precision from remaining samples with LA. Mark Schmitz developed the analytical chemistry and supervised the ID-TIMS work. Full details will be in forthcoming article. Also in recent dissertation (Washington State Univ.) by Wintzer.

Hi Huseyin,

It really comes down to what you are trying to do. I looked at both methods for my project on trace element geochemistry to characterise magmatic processes and fractionation trends. I ended up going with the LA-ICP-MS as the EPMA simply wouldn't be able to detect things like trace Nb-Ta in a rutile for example.

Both methods can do similar things, however, given that EPMA is a SEM based method, there are a number of additional analysis you can do that might be of interest.

It seems your interest is quite broad and so you might want to consider a combination of methods if that is an available option.

I've provided a brief summary below.

Hope this helps.

Zeb

EPMA:

- better accuracy

- better resolution

- versitile - can be combined with other detectors to provide a variety of data (back-scatter electron images, cathodoluminescence, SWIR)

-good quality control (QC) - lots of available standards and literature to support

- Can be time consuming

- Most EPMA's are typically 'tuned' to provide high quality results for certain parts of the periodic table. Can sometimes be limited by the number and type of monochromators used in the machine.

- more sample prep required (high quality polished surfaces)

- poor detection limits on trace element concentrations

LA-ICP-MS

- better detection limits for trace element concentrations

- faster

- less accurate

- QC issues - lack of reliable standards and converting CPS to ppm is somewhat of a dark art

Lots of different approaches, but at the end of the day, you can't go wrong with about 5 kg. Don't separate all of it, start with just 500 g. Don't do anything special, just crush and gold pan it, and if the sample is rich, the zircon will be there. A UV lamp can be used to see it in a dark room, or just go ahead and pick it under the stereomicroscope. If it is detrital, it won't get locked up in other grains. Baddeleyite is different, and the only good way is to extract using a Wilfley Table.

Dear Irakli Javakhishvili ,

Glad to have been of help. I don't personally do fluid inclusion studies, but I can suggest you a couple of persons in case.

Best, Samuele

Hi Grace, please have a look at the paper by Veksler et al. (2005) in Geochim Cosmochim Acta 69: 2847-2860. You might find it very useful.

I think it is safe to say that older zircons are more vulnerable to Pb loss. This is especially so for those with higher U concentrations (>400 ppm). This longer time combined with the more decay destruction of the lattice contributes to the opportunity for lead loss.

In obtaining your PhD you do not need help from outside except, perhaps, to suggest a problem. Once you have a possible problem at hand you must search the available literature to understand what has been done and the failings of past work that will define the scope of your project. But perhaps there is an obvious problem at hand, such as a nearby metamorphic terrain that has not previously been described or whose description is incomplete. You, of course, will need (1) a clear statement of your project's purpose and scope and (2) an assessment of the resources you will need, e.g. thin sections and a petrologic microscope. But, ulimately, the project is yours and, yes, it is nice to have a sounding board who can help you attain focus and avoid deteours down wrong paths. But you should take possession of the project as being yours and your contribution to the advancement of knowledge.

Hi There,

It is in fact a bit of a fallacy that Laser Ablation techniques destroy more standard, whilst they are a more destructive analysis than SIMS and use more repeats, the standard chips themselves tend to be used much more efficiently. This is because laser systems can use separate standard blocks, with tightly spaced analysis, that can be repolished. SIMS wastes a vast amount of standard in general as chips are placed in each mount and only a tiny proportion is used. This means you can acquire standards for laser and make them last a very long time if you are careful.

Many zircon U-Pb standards are freely distributed, and the ones in larger supply can typically be obtained from those who characterised them. Check the original papers for the lab or contact. e.g.

Geoscience Australiav for TEMORA zircons

GEMOC for GJ1 (i believe Elena Belousova is the contact)

There are many more that are common in geochron labs that you can look up e.g. FC1, AS3, Plesovice, SL1, Piexe

Others are in abundant supply and can often be obtained online through eBay or gem dealers e.g. Mud Tank (Though there is always a chance of a duff one in terms of precision)

There a decent list of zircon standards and references in here

Kind regards,

Rich

Dear Cristhian

I agree with Prof. Baig and Dr. Marijn. LA-ICP-MS system as well as its maintainance is costly. It has been proved that LIBS works better even for the geological sample and is faster than the LA-ICP-MS. Finaly you have to decide keeping all the points in your mind in the present situation.

Hi Daniel,

To follow-up on Martin's response, I should add that, depending on what type of ablation chamber you have, you should be able to "bake" the Hg out by removing the cell and sample holder(s) from the laser and heating them up in an oven at reasonably high temperatures (<75C). If you have a two-volume cell, do not forget to bake the inner cup as well. Be careful, though, since you might have O-rings, seals, and other bits and pieces that can be sensitive to heat. It helps if you a flush the cell with a constant flow of high purity inert gas while baking .

This should speed up the decontamination process, along with replacing all sample transport tubing.

Thank you for your quick replies. I didn't know the GeoReM database yet and it shall be very helpful with such research. Also the possibility of just using aluminium phosphate as a standard sounds good and straightforward. If I manage to compact such a powder material it might just work.

Baddeleyite is also pleochroic and might have a greenish hue apart from the reddish-brownish colours mentioned by Leonid. Please find attached some microscopic images in transmitted (plane polarized and crossed polars) and reflected light. Field width is 180 microns if not stated otherwise. Of course a SEM/EDX investigation would provide more information. The rock containing the Zr phases is a potassic syenite.

Here is a recent paper that outlines a standard workflow and recommended treatment of LA-ICP-MS data.

All the best

I don't think you saw my posting.  Yes, it should work if you have no material settling and in free Brownian motion.  However I've seen too many of these systems where the metal lies on the bottom of the container and ther's virtually none in suspension.

Just a bit of an update - new zircon mounts with variable grain size (from 40 up to 1000 micron) behave well in Epofix resin - almost no lost during polishing and I treat the samples quite rough :-)

Please note that the nano-particle pressed-tablets are made from homogeneous powders, and pressed with no binder. The surface is smooth enough for SIMS analysis, and the tablets obviously also handle the vacuum of SIMS or EMP. I don't make these myself, but get them from Dieter Garbe-Schonberg. He has demonstrated their homogeneity, even when mixing crazy options of rock types as examples of the ability of this process.

Excuse me. I can not help it because I just search for stable isotopes of C and O

You can use Belousova's diagrams for magmatic zircons to determine the nature of your detrital zircons.

Apart from the possibilities that Hafiz gave, it could also be that there is more than one population of zircon (or whatever other mineral you may have dated); or that some of the zircons have lost Pb; or that you have underestimated the uncertainty of the individual analyses that you have used to calculate the age. Is this MSWD for concordancy, or for an upper- or lower-intercept age? Perhaps you should give the diagram on which you base your statement, and we can say something more.

I'm amazed that none of the other answers have pointed this out, but here goes. A Langmuir probe can indeed be used as a diagnostic for certain types of plasmas, but it cannot be used for a typical laser-produced plasma.

Langmuir probes must be immersed in a plasma long enough to make voltage measurements etc. Therefore the desired plasma must:

Laser-produced plasmas typically meet none of the above conditions. Practical laser ablation happens with short pulses (nanoseconds or shorted), focused to spots millimetres in diameter. A plasma produced in this way is far too short-lived and rapidly expanding to get a measurement with a Langmuir probe. Even a CW industrial cutting laser produces turbulent, rapidly recombining plasma with steep temperature and density gradients. Making measurements on it with a Langmuir probe is out of the question.

 Dear Zehra,

I understand that the separation of minerals is not the most important of your business.

The simplest method of separation - manual separation of minerals during irradiation with UV radiation. Zircon will luminesce green-yellow light color (see answers to Petra Vesela). Pyrite is not luminescent.

If you have a lot of minerals, I recommend using the automatic X-ray luminescent separators, which are used for diamond industry. In the diamond industry zircon is a poor mineral which is extracted together with diamond and clogs concentrate.

But if you do not afraid some change the characteristics of zircon, it is possible to heat a mixture of pyrite + zircon at 200 -300C for 10 - 15 minutes. After that, zircon becomes lighter, but they restore color later. The pyrite becomes magnetic. After the procedures ferropirite is removed by magnetic fild.

Vasily

Dear Dr. Kenneth ..! 

Very interesting question,  At the beginning can't we use "comparative  anatomy" or external morphological characteristics for identify the differentiate in between  human bones of animal bones?if it is some thing like meagfauna?

Usually XRF analysis means bulk analysis, meaning the sample is considered homogeneous in depth. Elemental depth gradients cannot be resolved with standard XRF geometry, thus, when measuring a sample with surface enrichment or depletion, quantification values are not strictly correct, as you are using a 'incorrect' modell of your sample. Just to give you an idea, in metals the information depth of fluorescence lines is on the order of a few 10s of µm. I guess a cross section would give you the easiest access to the stratigraphy. If non-destructiveness is mandatory, maybe techniques such as grazing incidence XRF might be usefull.

I am also confident, that there have been a couple of studies dealing with ancient coins, if not even book chapters.

Dear LU,

Please find the attached file. When you use this Excel table, copy your own zircon trace elements data and the corresponding whole rock trace elements data to the yellow part of the table, and don't change the other coefficients, and then you can obtain the zircon Ce(IV)/Ce(III) values in the summary part of the table (the line with green color). 

best wishes,

KK

I agree, "1 ppm" is just a way of saying "one [part] in a million". That can be µg/g, g/t, µ-mol/mol, or even differences in isotopic ratios. Ppm in itself is a dimensionless ratio.

I'd say that if you want to say you have a one-in-a-million chance to win the lottery, then "picks of the right numbers occur at ppm-level" is a correct statement (although in reality the chances are well below ppt-level).

You can check the manual online. Concerning the voltage, check if you can get power regulator.

In addition to Leonid's suggestion, if the 206/204 ratio cannot be measured precisely and accurately (either because of the isobaric Hg interference, and/or if the 204 counts are too low), then you could plot the data on a concordia diagram, and assess if the zircons are discordant.

Most popular method being D-square method (https://www.osapublishing.org/ol/abstract.cfm?URI=ol-7-5-196). You plot the square of the crater diameter against laser power/pulse fluence/fluence(if you know w0). This method allows you deduce ablation threshold, w0 and incubation coefficient of any given material.

In my humble opinion, I think that possibly should do the cleaning only with nitric acid, and not add any mixture of solvents, or first one and then the other acid, because maybe that is generating this problem and should also be careful to keep on for a while after cleaning to remove any residues at least an hour and a half. and then test a series of standards with known concentrations to ensure that cleanup was effective.

Dear Sanghamitra,

check this:

Regards

Thomas

I agree with Leonid that concordant data are inconsistent with Pb loss. Otherwise, similar morphology is a very vague indicator, and a more thorough study of the zircons (CL, composition) should get us closer to the answer. Dating does not make much sense without a good knowledge/documentation of the analyzed crystals. And yes, the youngest concordant ages are likely to represent crystallization ages, while the older ones are most probably inherited.

Thank you! By the way, what is the equipment (and method) that you are employing to analyze your samples? 

I am potentially interested in collaborating. Info about our lab is here: https://sites.google.com/site/icpgeolucsb/

You can email me for more information: cottle@geol.ucsb.edu

In ToF mass spectrometry the relation between mass (m) and time-of-flight (t) is determined by the kinetic energy that is the same for all ions

Ekin = 1/2 m* v^2 (with v=s/t) 

as also the flight path s is the same this ultimately leads to : m ~  t^2.

In practice, however, your starting time is not 0, but there is a small shift t0 (can be positive or negative): m=(t-t0)^2 * k

To work out both constants k and t0 you just need two known masses and their time of flight. If this calibration does not give reasonable masses for other substances you should check what you use for calibration, metals could oxidize and you may not see the elemental ion, but oxides...

Dear Motahare Mohseni,

I can also suggest Photoluminescence (PL) measurements with high resolution. PL is a very sensitive, fast and non-destructive technique and it is commonly available.

Hallo Maria

LA (Laser Ablation) and ICP-MS (Inductively coupled plasma mass spectrometry) are two different things. Potentially you could couple a laser to a variety of analytical instruments as MS, SF-MS, ToF, AES etc.

With LA-ICP-MS you can obtain both element concentration and isotope data including the Rb-Sr¹ system or U-Pb dating². I recommend you have a look here: http://pubs.rsc.org/en/journals/journalissues/ja#!recentarticles&adv

If you are interested in LA-ICP-MS of isotopes maybe the search term triple quad or ICPQQQ could be interesting for you.

The samples you named are very different, although LA has been done on liquids (mostly to generate nanoparticles), this wouldn't be the method of choice for water analysis.

(1): Jochum, K. P. et al., 2009 In situ Sr isotopic analysis of low Sr silicates using LA-ICP-MS, J. Anal. At. Spectrum., Volume 24, Issue 9, Pages 1237-1243, http://dx.doi.org/10.1039/B905045K

(2): Simon, E. J. et al., 2004 The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U–Pb zircon geochronology, Chemical Geology, Volume 211, Issues 1–2, Pages 47-69, http://dx.doi.org/10.1016/j.chemgeo.2004.06.017.

Hi Yuri. I am not using hydrogen (too light) but rather Nitrogen (3 to 4 ml/mn). It works very well to increase the signal for heavy isotopes.

There is considerable good advice above.  But any hand picking will introduce additional bias in any analysis.  If you want the analysis to be as un-biased as possible, make sure your mineral separates are clean, and this may mean refining the separation process.  Then mount everything, image the mount, and then do a random walk from zircon grain to zircon grain.  

Bear in mind that part of your approach should be directed to what you are tying to accomplish.   You may, for example, select euhedral grains because you are interested in the provenance of first-cycle grains only.  Or perhaps only the rounded grains that may be recycled are of interest.    As you note, the euhedral grains are relatively easy to identify, and but zircons get increasingly more difficult to identify if they are broken, frosted, and they have radiation damage.   As such, it is very easy to bias your data by just focussing on the euhedral grains.

If you want to keep using the epoxi you could try to remove the zircons grains with a hot needle / soldering iron from the epoxy mount. I did this with quartz grains and it worked very well.

Another option would be to embed the zircon into indium metal. This is a technique developed at the University of California in Los Angeles and used in secondary ion mass spectrometry (Schmitt et al. 2010). You could check, if it also works for LA-ICP-MS. Once the indium mounts are prepared this technique is very quick and easy. You only press the zircon into the soft indium and the mount is ready to use (no waiting time for the mount to harden as with epoxy). The zircon grain can be removed with a small needle. The indium mounts can be reused several times and it’s also possible to polish them. There are no interferences encountered for ion beam overlap with indium.

Schmitt, A.K., Stockli, D.F., Lindsay, J.M., Robertson, R., Lovera, O.M. and Kislitsyn, R., 2010. Episodic growth and homogenization of plutonic roots in arc volcanoes from combined U-Th and (U-Th)/He zircon dating. Earth and Planetary Science Letters, 295(1-2): 91-103. doi: 10.1016/j.epsl.2010.03.028

Thanks for the advice. Will speak to Peter and will have a go at getting a slice.

They are very big. About 100 Kg!! in weight and 1 m wide.

Henk

Dear Abrahim,

Just to be clear, David Selby and his group  do not carry out in-situ, by which I take it you mean laser ablation MC-ICP-MS or SF-ICP-MS, Os isotope analyses of sulfides.

Myself and Chris Dale on the other hand do carry out in-situ Os isotope analyses by laser ablation MC-ICP-MS but on platinum group metal alloy grains rather than sulfides. We are the only people at Durham carrying out such in-situ Os isotope analyses.

The problem with the in-situ Os isotope analysis of sulfdes is that generally the sulphides are so small and the Os concentrations too low to yield an Os beam size that provides meaningful/accurate Os isotope data. In some cases the Os signal is so low that to perform a mass bias correction during the measurement it also proves necessary to aspirate an Ir solution and mix that with the laser ablation product. Performing accurate Re corrections on the 187Os is also very difficult at low Os beam intensities. There is also the issue that if you've polished a section to expose a sulfide then you will have lost some of that sulfide and if there has been any exsolution it may have fractionated the Re/Os ratio such that the Re/Os ratio you measure on the remaining sulfide may have no bearing on the measured Os isotope composition. In other words the Os isotope compositions is unsupported by the measured Re/Os ratio. A couple of references to look at that discuss some of the issues with in-situ Os measurements are :

Pearson N.J., Alard O., Griffin W.L., Jackson S.E., O'Reilly S.Y., 2002. In situ measurement of Re-Os isotopes in mantle sulfides by laser ablation multicollector–inductively coupled plasma mass spectrometry: Analytical methods and preliminary results. Geochim. Cosmochim. Acta., 66, Number 1037-1050(14).

G.M. Nowell, A. Luguet, D.G. Pearson & M.A. Horstwood (2008a). Precise and accurate 186Os/188Os and 187Os/188Os measurements by Multi- Collector Plasma Ionisation Mass Spectrometry (MC-ICP-MS) part I: solution analyses. Chemical Geology 248: 363-393.

Norm Pearson and Bill Griffin at GEMOC are probably the main group carrying out this kind of analysis so I would contact them if this is really the way you want to go.

Hope this helps. All the best

Geoff

Maybe you could get some hints from this paper:

Wendy Cieslak, Kathleen Pap, Dustin R. Bunch, Edmunds Reineks, Raymond Jackson, Roxanne Steinle, Sihe Wang, Highly sensitive measurement of whole blood chromium by inductively coupled plasma mass spectrometry, Clinical Biochemistry 46 (2013) 266–270. http://dx.doi.org/10.1016/j.clinbiochem.2012.10.035

Dear Christopher,

I am slightly puzzled by the fact that this particular stalagmite was shown to be in secular equilibrium (>500 ka) by U-230Th method. A simple calculation shows that if you start accumulating radiogenic lead in a speleothem initially having common Pb (206/204~18.5, 207/204~15.6, and 208_204~38.5) and 238U/206Pb=50, then in 3 Ma in a closed system its 207Pb/206Pb will be =0.68, which is a bit lower than your lowest measured 207Pb/206Pb value. Because 238U/206Pb value decreases with time, measured values of ~1000 in your sample may indicate that initial 238U/206Pb was even higher. For the initial 238U/206Pb=1000 207Pb/206Pb will be =0.15 in 3 Ma, which you do not see. Therefore, there are at least 2 natural reasons to explain your data:

(1) Your speleothem is younger than ~ 50 ka

(2) You deal with open U-Pb system. The first scenario would require COMPLETE loss of radiogenic Pb, which is highly improbable. The second scenario would require very recent considerable U gain, which would result in young 230Th/U ages.

Therefore, my suggestion would be (1) to double check U/Th dating results and confirm that the same materials were analyzed for U-Pb and (2) carefully check the accuracy of your U/Pb ration LAICPMS measurements during the analytical sessions when these data were collected.

I hope this would help in resolving your puzzle.

Best,

Leonid

Hi Yuri,

we have a paper accepted with moderate revision in American Mineralogist dealing with Kd on plagioclase, alkali feldspar, Ti-magnetite, biotite and apatite in felsic alkaline volcanic rocks (potassic trachytes and trachyphonolites) from Phlegrean Fields. As soon as we have the paper definitively accepted I can send you the data.

Oter literature data can be found in Villemant (1988; CMP, 98, 169-183) and Pappalardo et al. (2008; CMP, 156, 1-26).

In Fedele et al (2009; CMP, 158, 337-356) you can find Kd of cpx in equilibrium with the same liquids (potassic trachytes and trachyphonolites) from Phlegrean Fields.

Cheers

michele

Samuel, no single method will provide you with all answer on all possible modifications, and certainly not in "high throughput" (which leaves me puzzled - why are you looking for high throughput if you "only" want to characterize one protein?). You will probably need a combination of separations (2D, SDS-PAGE) combined with MS, Western (provided antibodies can be raised) and other techniques here - in other words, a good old full-blown biochemistry project. It will not be quick or high throughput.

low Th/U (<0.1) in zircon can be an indication of metamorphic origin, however metamorphic zircons with high Th/U exists, particularly in high grade rocks. Ultimately the Th/U in zircon is controlled by other coexisting phases and the presence of Th-rich phases such as allanite or monazite generally infers low Th/U in metamorphic zircon. Rocks in which these phases are not presented or dissolved in anatectic melts will have metamorphic zircon with higher Th/U.

Alone Th/U is not sufficient to define a metamorphic zircon, zoning pattern, inclusions, trace elements and of course age in geological context have to come along as well.