Isotope Geochemistry - Science topic

Hi! There is a clumped lab in ATOMKI, Debrecen, Hungary. Check it out.

Hi Mr. Rojhani,

For study about rock genesis, I would suggest to take at the least one sampling point for each lithological unit. However, if you found variations within the same lithological unit, it's better to sample each variation.

Lithological unit/variation is more important than dimension/distance between sampling point.

For each sample, you will need to take two hand-sized speciment, one for microscopic observation (thin section + polished section if needed), one for chemical analysis (XRF, ICP-MS, stable isotope).

Another source could be oxidation of the methane (both biogenic and thermogenic). But even the 13C depleted thermogenic methane requires some biologically produced organic matter as starting materials. Sorry for this kind of loose answer. It would be great if you restructure/rephrase the question in more specific way.

Hi Afshin,

It depends a bit on the temperature range that you are interested in. For 18O/16O fractionation at high temperatures, it is probably best to use the fractionation factors by Zheng et al. (1991, GCA) that are based on the vibrational frequencies of the molecules. For triple oxygen isotope fractionation, one could use the theoretical values by Hayles et al. (2018, GCA). Both papers explain well how to to calculate water-magnetite fractionation at different temperatures. It is important to keep in mind that the calculations give accurate results only at the level of ca. +/- 0.5 per mill in d18O at the very best.

Best wishes,

Stefan

You can find all information needed in this paper, all the main equations used and how to chose.

Hello Praveen,

it seems that the book is available at Abebooks.com

Hope you find it!

Roberta

The answer to your question is: not always. Post-collisional or intraplate magmatism sourced from a hybrid mantle (crust+DM) presents geochemical (incompatible elements) and isotopic characteristics of the crustal component. Couzinié et al. (2016) (Earth and Planet. Sci. Lett.; Vol. 546) have demonstrated that a small (~10-25%) crustal component, transported to great depths in subduction zones as sediment or mechanically eroded sialic crust, is able to metasomatize/hybridize depleted mantle so that a rock sourced (e.g. high-K basalts) from this hybrid mantellic domain could provide incompatible element signatures (including Nb-Ta troughs), as well as radiogenic isotopic values (i.e. Hf, Nd), that dominantly reflect the crustal component. Therefore, let's picture a hypothetical scenario. Subduction during the Paleoproterozoic would generate arc-related magmatism and metasomatize/hybridize large swaths of the suprasubduction mantle. Right after continental collision, orogenic extensional collapse would partially melt this hybrid mantle and generate basalts (and fractionates) with a crustal-like geochemical signature, and therefore Nb-Ta anomaly. Extensional processes could (and probably would) continue during much longer periods due to periodic extensional/rifting. Therefore, basalts with Nb-Ta anomalies and other geochemical fingerprints of subduction zones could be generate in post-collisional or intracontinental settings. Nevertheless, they need to be sourced from mantle that was previously enriched and metasomatized by a (minor) crustal component delivered by an active subduction zone. Hope this helps. Cheers.

Hi Andrey,

There is nothing in principle to prevent Neodymium stable isotope geochemistry being explored to characterize magmatic processes, although the magnitude of mass-dependent fractionation is likely to be small, due to Neodymium's high molar mass.

Because of the analytical challenges involved, Neodymium stable isotope chemistry is in its infancy and has so far been applied to investigating materials exhibiting resolvable nucleosynthetic or cosmochemical Nd fractionations (i.e. among differing meteorite classes, and component CAI's within meteorites). Comparative studies involving earth materials have so far focussed on characterizing overall variance in Nd stable isotope concentrations, and the ε145Nd and δ146Nd of mantle and igneous crustal lithotypes with the aim of estimating the bulk silicate earth Nd stable isotope composition.

There have been no attempts published to date to characterize the Nd stable isotopic behaviour of a cogenetic suite of differentiated igneous rocks. However, preliminary work on various igneous rock reference standards suggests minimal variations in 146Nd concentration and δ146Nd/144Nd. There is some evidence that igneous rocks with SiO2 >70% do show show a resolvably heavier δ146Nd/144Nd than less differentiated igneous rocks such as MORB.

As alluded to by other contributers, bulk rock δ146Nd/144Nd in a differentiating igneous environment might be expected to be controlled, at least in part, by fractionation and removal of accessory minerals high in LREE, such as monazite, allanite, xenotime, titanite and apatite. These minerals would be expected from stable isotope fractionation theory (e.g. Schauble(2004)) to incorporate isotopically lighter Nd than the melts from which they crystallized.

I would recommend you follow the work of Alex J. McCoy-West of Monash University, who is a pioneer in the analytical techniques and research in this area.

Hope this helps

Schauble, E. A. (2004). Applying stable isotope fractionation theory to new systems. Reviews in Mineralogy and Geochemistry, 55(1), 65-111.

Dear Mrs. Lettini

I would like to refer to my comments given in a similar thread launched by your question.

You have to deal with the U disequilibrium in the U-238 decay chain which is physically impacted in that the gaseous radon escapes along faults and porous media from its source which can be each mineral from high-grade uraninite ore to white mica or decomposed phosphate which contain U of up to 200 ppm U. Moreover there are variable chemical solubilities of each daughter product, e.g., radium which may be precipitated in sulfate-enriched environments, because of its extremely low solubility (Ra barite). There are different solubilities of the daughter products.Th-234 and Ra-226 are less soluble than the parent radionuclide U-238. It may cause a separation of these elements owing to differential leaching. There are also certain energy effects. Energy of decay process results in oxidation, e.g. U-234 from U-238 in uraninite may cause U 6+ which more soluble than tetravalent U. Based upon that any general advice in this case would be misleading. You must show the various environments under study which are interconnected with each other by aquifers or surface waters and last-but-not-least consider the migration of radon gas in the water and in the open pore space. The best way is to conduct a sampling along a transect or on a grid using alpha-cups or –pumps to get an idea of pathway of migration. I worked for 6 years in the U branch and we used Rn for exploration. There are some textbooks displaying case histories on the migration and trapping of Rn.

With kind regards

H.G.Dill

Unyime Umoh

Yes, I am totally agree your comments. As the sampling area is a big shallow urbanized lake, many sources was generally mixed and biodegraded. I have already tried to apply the proxy as your recommend, and I got a higher contribution of terrestrial and sometimes petroleum contribution. But what I am confusing is that the particles have lower C/N ratios and relative low POC/chla (<100 microgram per Litter) as I said in my questions. And actually I am not expecting the higher contribution of terrestrial, because the lake is highly eutrophication, and cyanobacteria bloom (I thought they are main contributors to C17 in my case) is serious issues in this lake. So I am wondering if the alkanes indicators are still robust in my case, since I saw some articles showed the diagenesis effect could cause higher contribution of long chain n-alkanes in sediments, even though the allochthonous inputs is few.

And I am very grateful for your suggestion, I will try to test them. Could you tell me the approximate retention time of these compounds basing my TIC graphs, it will be helpful for quickly locating them.

thank you very much

Parasites fractionation values in parasites are an interesting area of study. However, they are not well known (to my knowledge) but this paper does look at some cases: Unusual stable isotope fractionation patterns observed for fish host—parasite trophic relationships. If you are trying to correct for fractionation you must rely on published values or controlled laboratory studies.

Thanks a lot for your answers

It doesn't matter what you normalise to, as long as you are aware of what the differences between the different normalisation data sets do to your REY patterns (in particular with respect to the Eu anomaly - it does neither affect Ce nor Y anomaly). Normalisation is just a way to make the interpretation of REY data easier and help you illustrate your message. Make sure, however, you use a REY data set of good analytical quality that itself produces a smooth normalised REY pattern. If the normalised REY pattern produced from your data is not smooth (except for the anomalies that make "chemical" sense), the analytical quality of your data is highly questionable and you must not use such data!

(Note that Pourmand et al's "new" PAAS is based on different samples than the "old" PAAS, and hence their REY concentrations - though not the shape of the REY pattern, of course - are rather different.)

In addtion to the answers already given, diagenesis of carbonate in bio-apaptite will cause isotopic fractionation.  The direction of which depends on the nature of the process.  Long-term exposure to water (immersion) will shift carbonate d18O towards water d18O. Processes that produce CO2 as end-product will typically result in the remaining carbonate to become heavier in 18O.

The phosphate fraction of bio-apatite is virtually impervious to diagenesis which is why archaelogists and paleoecologist tend to prefer phosphate d18O over carbonate d18O.

Working on the basis of bio-apatite phosphate d18O values to be "true" one can use the correlation equations published by Iacumen et al. (1996) and Chenery et al. (2012) for bone and teeth respectively to check if corresponding carbonate d18O values are artefact free.

There are many analytical labs, for example the Bureau de Recherches Géologiques et Minières (BRGM), Orléans, France

Thank you Sagar. I've have seen some of the journals and they are quite helpful. Really appreciate.

Regards

On the bioapatite "mineral fraction", we must do a test "fish in preservative as Formol / Formaldehyde", but I think that the isotopic analysis in 18O is always valid.

Dear Mhammad

For young, poorly radiogenic zircons the TW plot for uncorrected data is probably the best. Significant amounts of common Pb and the difficulty in measuring correctly the poorly radiogenic 207/235  ratio makes concordia plots in some cases unreliable. In the uncorrrected TW diagram you however have to find a consistent group of data that define a good regression toward the unradiogenic 207/206 axis in order to define an free intercept age on the reverse concordia. Scattered data will not provide an age constraint.

Good luck

Daniela

In addition,  you can check out the following articles

1, Similar V/Sc systematics in MORB and arc basalts: implications for the oxygen fugacities of their mantle source regions

CA Lee, WP Leeman, D Canil, ZXA Li - Journal of Petrology, 2005

2, Water and the oxidation state of subduction zone magmas

KA Kelley, E Cottrell - Science, 2009

3, Fluid processes in subduction zones

SM Peacock - Science, 1990.

Dear Dilshad,

Nice image, the elongated dark brown has similar shape to what I found within Jurassic and Upper Miocene rocks.

Regards,

To add up in the on going answers and discussion.

Zr isotope systemic such as U-Pb & Lu-HF has gained a global significance in depicting the crustal evolution, due to various reasons as provided by Dr. Latha and Mr. Leonid.

well studies on whole rock isotopic systemic are limited and are not used much due to various difficulties mainly in determining the initials isotopes ratio. Some of the difficulties are mentioned below:  

- It is very difficult to fix the Complexity of geological system with whole rock isotopic data as it represent the multiple phases with various ages and evolution paths.

- due to imprecise isochron dating which  involve assumption difficult to verify.

- Difficulty in assuring the closed isotopic systems in older and poly deformed rock.

Now using zircon isotope systemic also have its own complexity such as

- zircon crystallisation or growth, it can grow during more than one geological event or may have been effected by alteration process.

- Disturbance in U-Pb systematics of zircon, ancient Pb loss or recent Pb loss

- Sensitivity of Lu / Hf ratio due to involvement of garnet.

 All these complexity need to be addresses before interpretation, thanks to recent developed analytical technique and methods allowing us to acquire precise analysis. To overcome most of the above, combined approaches such as combined isotopic systematics of zircon along with O isotope and REE analysis and imaging techniques is used  for getting robust insight to the process of crustal evolution.

Combined Zr isotopic systemic is much more reliable than the whole rock isotopic systemic and one can decide on the pros and cons before choosing the methods for studying crustal rocks. 

I am also a bit confused - perhaps some more detail as to background and what you are proposing?. WHICH isotopes indicate a primitive origin for the granites and why? What is the chemical and mineralogical composition of the granites? Exactly what origin are you proposing for the granites - pure anatexisis, mixing? Please define what you mean by a primitive nature for the biotite schist - are you referring to its age, or the age of the sediments it was derived from, or the age of the source rocks for the sediments?

Hi Yuxiang,

It is difficult to assess whether the rock you have described is unusual in any way without a bit more information. Assuming we are dealing with an equilibrium assemblage it would be useful, for example, to know the K₂O/Na₂O of the residual liquid (groundmass), and any zoning, compositional variation, or evidence for resorbtion, in your phenocrysts.

I recommend you take a look at Carmichael (1963) who discussed low pressure equilibrium relations in the system CaAl₂Si₂O₈-NaAlSi₃O₈-KAlSi₃O₈-SiO₂ with specific reference to the evolution of one- and two-feldspar rhyolites. Carmichael showed that single-feldspar (sodic plagioclase-anorthoclase) rhyolites containing ~4% K₂O can readily evolve in the ternary feldspar-quartz system, given the appropriate initial bulk composition of the parent magma.  

In addition to the examples quoted by Carmichael, other examples of high-K, plagioclase-bearing rhyolites which lack sanidine are described by Takagi et al (1999) and Kimura et al (2007). The Kimura paper is interesting because it alludes to the low fO₂ environment of formation, invoking assimilation of (graphite bearing) metapelites mentioned above in Lucas’ contribution.

Hope this helps,

Graham

Carmichael, Ian "The crystallization of feldspar in volcanic acid liquids." Quarterly Journal of the Geological Society 119.1-4 (1963): 95-130.

Takagi, Tetsuichi, et al. "Petrology of a mantle-derived rhyolite, Hokkaido, Japan." Chemical Geology 160.4 (1999): 425-445.

Kimura, Jun-Ichi, and Yoshitaka Nagahashi. "Origin of a voluminous iron-enriched high-K rhyolite magma erupted in the North Japan Alps at 1.75 Ma: Evidence for upper crustal melting." Journal of Volcanology and Geothermal Research 167.1 (2007): 81-99.

Dear colleagues:

We need more hard facts. Tidal regimes, volcano-sedimentary sequences, the source of Cr and the host of Cr, as well as  exhalations are very difficult to be put together to give me a coherent picture. Or shall we cast aside the slogan "The present is the key to the past"  for these very old rocks ?  A chemical approach using the V/Cr ratio in the argillaceous layers (so-called fuchsite) may give an answer to the variation in the redox conditions. V increases with lowering of the Eh (more reducing) and Cr responds in the opposite direction (more oxidizing). If it gives a more coherent picture together with barite you get a bit closer to the large-scale environment. I would be very much reluctant to jump too fast into an interpretation of the depositional environment without proper knowledge of the mineralogy and chemistry. Nevertheless, a nice story, to think about.

Best regards

H.G.Dill

Dear Mrs Huang,

 the correct treatment of mass balance during open system-processes (such as alteration, metamorphism or weathering)  needs to take into account the changes in overall mass/volume of the whole system, which would also apparently alter the concentrations of immobile elements, whose abundances in reality did not change at all.

I agree with Antoine and Gordon that isocon method is commonly employed remedy to this problem. But unfortunately it does suffer from two drawbacks: 1)  it does not take into account a variability of the protolith (only a pair of rocks is assessed at the time) and 2) it is subjective in that the individual elements are scaled , i.e. multiplied by arbitrary coefficient, in order to obtain more legible results. 

I would like to bring to your attention an alternative, called Wedge plots, defined by prof. J.J. Ague. They are  superior in that they take into account the overall variability of the whole dataset (both of the putative protolith and the altered product) and not just a selected whole-rock pair, and do not introduce any subjective aspects, such as arbitrary scaling.

Ague JJ (1994) Mass transfer during Barrovian metamorphism of pelites, south-central Connecticut; I, Evidence for changes in composition and volume. Amer J Sci 294:989-1057

BTW, they can be plotted by GCDkit, gcdkit.org.

I trust that this helps,

Vojtech Janousek

Hi Ke-Qing

You rly can't without knowing also the covariance: E((X-E(X)*(Y-E(Y)). As also Michaels reference should tell you.

cheers  / Bo

Dear Mr. Tripathi,

why do you take refuge to sulfur isotopes ? First make an attempt using geological methods such as sedimentological ones, than go into sedimentary-mineralogy (heavy and light minerals, phyllosilicates). Also the major and minor elements offer a lot in terms of recognition of the paleo-environment. There exists a wealth of papers. Do not saddle the horse from the tail and follow straightforward the common way of geoscientific work.

This is based on almost 40 years working in the geoscientific business.

H.G.Dill

Thank you for the information Prof. Bots....

You have to take into account that carbon-14 has a half-life of approx. 5700 years. So dating in that comparibly small time-frame will not be all too accurate.

In addition to being the customary reference isotope, it is one of the high-abundance Nd isotopes (therefore easy to measure). Typically, we want to reference radiogenic isotopes of an element to stable isotopes of the same element that aren't affected by ingrowth or decay. While 144Nd isn't actually stable and undergoes alpha decay, the decay rate is so slow (t1/2 on the order of 10^15 yr) that you wouldn't see significant change in 144Nd in geologic samples.

With regard to the isobaric 144Sm interference, we get around that by separating Nd from Sm and other elements in the sample. If the separation is imperfect and there is still a tiny amount of Sm present, it is possible to monitor other, uninterfered Sm isotopes during analysis. Assuming natural Sm ratios, you can then subtract the 144Sm part of the total measured 144 amu signal, isolating what should be just purely the 144Nd part of the signal in order to calculate your ratio.

I am searching a way to prove the age of some sediment strata which presumably are upper Miocene or Pliocene( C 14 is not working). This strata are reach of  Flora fossils, but so far can not determine the age only by them. They aslo are reach of iron oxides, that is why if we can date the oxide, than we can date the flora and the strata as well.

Dear Dr. Roberto Innocenti,

Thanks afor your answer. I will pay attention according to your suggestions.

Dear Mr. Xu, 

despite the lack of detailed information on the regional geology and metallogenesis there is only one piece of advice I can give you: Go out in your working area and try and  disentangle the relationship in space and time between magmatic rocks, alteration zones, country and wall rocks and last but not least Pb-Zn mineralization. This is the key element at the beginning of every work in economic geology. Your mapping procedure should include, lithological mapping, mineralogical mapping and mapping of the structural geology.

I wish you good luck 

H.G.Dill

Dear M. Nwaila, please find attached two pdf copies of papers that can be useful for you, including the references cited in these articles. Hoping these articles will be helpful for You, Best wishes, Anicet B.

As Dr. Qasim Jan mentioned the source could be magmatic but this needs more investigations. Pointing directly to your question, yes it is possible to have a metamorphosed marl  without calcite (or dolomite) in mineral assemblage. This happens if the molar proportion of  reactants are right amount that consumes all carbonates. Let explain this with an example. Consider reaction   calcite+quartz=wollastonite+CO2. In this reaction one mole calcite reacts with one mole  quartz to give one mole wollastonite and one mole fluid (you can see this if you write down the chemical formula of the minerals). If your protolith is made up of 50% quartz and 50% calcite, then in the resulted metamorphic rock you will not have neither quartz nor calcite. Because all calcite reacts with all quartz. Consider a protolith with say 30% calcite and 70% quartz. On metamorphism, 30% quartz reacts with 30% calcite and the remaining quartz will not be consumed in the reaction. So you end up with a rock with 30% wollastonite,  40% quartz and no calcite (the rest is fluid, this will be more correct if you consider the proportion in molar term rather than wt%, I wrote in % to make it more clear).

Thank you Mr. McDonald!

Dear Mr. Trevino,

you questions are very far-reaching, particularly in terms of the outcome of chemostratigraphy, where a huge number of answers may be given as the various element ratios are concerned (see e.g., V/Cr, Co/Ni ratios etc...)

1. Chemostratigraphy applied in its general way addresses chemical changes and in that it is synonymous with litho-stratigraphy. As such you cannot use it like chronostratigraphy which is based either on the evolution of life or the decay of radioisotopes which is a function of time.

2. The number of papers is enormous. You can get information of the provenance of sediments (extrabasinal) or the physical-chemical regime during sedimentation and diagenesis (intrabasinal)

3. If radio-isotopes are involved a temporal component is inherent to the process and chemostratigraphy is equivalent to what has been told under (1). If stable isotopes like S are considered the system can be denominated as an advanced level of elemental chemostratigraphy. No age information is implied. It is a sort of correlation and fingerprinting using growth curves and time-lines showing the evolution of, e.g., S content in the seawater or any other stable isotope system.

Best regards

H.G.Dill

Hi Weigang,

Here’s a small selection of (relatively) recent review papers to enable you to compare and contrast.

Best regards,

Graham

Mével, Catherine. "Serpentinization of abyssal peridotites at mid-ocean ridges." Comptes Rendus Geoscience 335.10 (2003): 825-852.

Hyndman, Roy D., and Simon M. Peacock. "Serpentinization of the forearc mantle." Earth and Planetary Science Letters 212.3 (2003): 417-432.

Kodolányi, János, et al. "Geochemistry of ocean floor and fore-arc serpentinites: constraints on the ultramafic input to subduction zones." Journal of Petrology (2011)

Guillot, S.,  Deschamps, F., Godard, M.,., & Hattori, K "Geochemistry of subduction zone serpentinites: A review." Lithos 178 (2013): 96-127.

You can make a good case for arguing that the genesis and distribution of porphyry copper deposits (and the other disseminated ores such as molybdenum) were not properly understood until the advent of plate tectonic theory. The first studies linking porphyry/disseminated ore metallogeny to plate tectonics appear in the early 1970’s with Pierra and Dixon (1971) providing the first graphical depiction of porphyry copper mineralization in a continental arc setting above a downgoing slab. The spatial association of porphyry copper deposits with arcs formed above current or former subduction zones was then discussed in detail by Sillitoe (1972).

Prior to plate tectonics, however, geosynclinal theory held sway: a notable exposition of porphyry copper mineralization in the context of geosynclinal theory was provided by McCartney and Potter (1962).

You then have to go back to the early years of the 20th century to find the first properly scientific petrographic and field studies dealing with this particular ore paragenesis. Foundational work of this type was carried out by geologists of the USGS, for example Boutwell (1905) and Lindgren (1906).

Pereira, J., and C. J. Dixon. "Mineralisation and plate tectonics." Mineralium Deposita 6.4 (1971): 404-405.

Sillitoe, Richard H. "A plate tectonic model for the origin of porphyry copper deposits." Economic Geology 67.2 (1972): 184-197.

McCartney, W. D., and R. R. Potter. "Mineralization as related to structural deformation, igneous activity and sedimentation in folded geosynclines." Can. Min. J 83.4 (1962): 83-87.

Boutwell,  J.  M. "Economic  geology  of  the Bingham  mining  district,  Utah"  U.  S.  Geol. Survey Prof. Paper  38 (1905), p. 73-390.

Lindgren, Waldemar. "The copper deposits of the Clifton-Morenci district, Arizona". No. 43. US Government Printing Office, (1906).

Regards,

Graham

For fluffy freeze dried samples, some times you can just 'fume' the sample with HCL vapor for a bit (I've used ~8hrs, but probably overkill) and re-lyophilize the sample or just put it under vacuum for a while to remove any water or HCL adsorbed.

A simple method for fuming just uses a glass desiccator. pour a mL or so of conc. HCL in the bottom put the sample tray and sample (unsealed so the HCL vapor can reach it) in, close the lid to the desicator and let diffusion do it's thing.

You can also pH adjust (very carefully) your samples before freezedrying them to ensure the DIC volatilizes during sublimation.

Good Luck!

If your samples bird feathers feed mainly on C3 plants, I suggest you too, instead of the correction for "Suess effect" you try to rebuild the d13C the atmosphere.

Sorry the Kroner et al is not 2013, it's 2014. The reference is correct. 

Better also to see 

Vervoort, J.D., Patchett, P.J., Blichert-Toft, J., Albarède, F., 1999. Relationships between Lu–Hf and Sm-Nd isotopic systems in the global sedimentary system. Earth and Planetary Science Letters 168, 79–99.

some material attached below

Not sure if this is still relevant.  Only came across this question today.  From an 2H / 18O analysis point of view the presence of microbicides such as CuSO4 or NaN3 should not cause any problems.  If memory serves, Picarro claim one can analyse water 2H / 18O directly from urine.  That being said, you might have to clean interior surfaces (mirrors) more frequently as compared to typical maintenance schedule when running clean water samples.  Also, the flash evaporator will need regular inspection and cleaning (salt crust deposits).

Dear Jiawei Da,

Although HCl does not change isotope results you should remove it from the sample because it can damage spectrometer.

pH of your sample should be around 6.

Best wishes,

Karina

Dear Haozheng,

I could not agree more with Esther. In fact there are a few papers out there which undertook this "exercise" and could help you about the applied methodology and expected concentration levels of "water" in different NAMs from granulites.

Németh, Bianka, et al. "Melting, fluid migration and fluid-rock interactions in the lower crust beneath the Bakony-Balaton Highland volcanic field: a silicate melt and fluid inclusion study." Mineralogy and Petrology 109.2 (2015): 217-234.

Zhang, Li, Junfeng Zhang, and Zhenmin Jin. "Metamorphic P–T–water conditions of the Yushugou granulites from the southeastern Tianshan orogen: Implications for Paleozoic accretionary orogeny." Gondwana Research (2015).

Yang, Xiao‐Zhi, et al. "Water contrast between Precambrian and Phanerozoic continental lower crust in eastern China." Journal of Geophysical Research: Solid Earth (1978–2012) 113.B8 (2008).

In spite of some unjustified criticism on the methodology I would still recommend you with confidence to use the unpolarized infrared methodology (see references below) (this would save you a lot of time and effort and would not worsen significantly the accuracy of your quantitative results), or in some cases it would make possible to have any quantitative data at all). There are only a few absorbance conditions which should be met for accurate results. Note, however, that this methodology is rather limited if you would like to constrain the crystallographic orientation of particular absorbers in minerals.

Kovács, István, et al. "Quantitative absorbance spectroscopy with unpolarized light: Part II. Experimental evaluation and development of a protocol for quantitative analysis of mineral IR spectra." American Mineralogist 93.5-6 (2008): 765-778.

Sambridge, Malcolm, et al. "Quantitative absorbance spectroscopy with unpolarized light: Part I. Physical and mathematical development." American Mineralogist 93.5-6 (2008): 751-764.

You can have access to the digital spectra of several NAMs from granulites in the PULI spectral database for free and you have the opportunity to share your own spectra with the wider community ( puli.mfgi. hu ).

I hope that this was a help and good luck with your research,

Cheers,

Istvan

From my experience, white mica closure temperature depends on grain size. In hydrothermal muscovites (sericites) it is most likely not above 300 degrees, perhaps lower. 

Hi, Towe. The the plots given by Liu are different.

Your plot is the answer for the first one.

I did the second kind plot in the attached file.  I'am sorry that my EXCEL is in Chinese.

Paulo-

A recent JGR paper by Rioux et al. on the Samail ophiolite came to mind.  I'm not sure if their work strictly satisfies your request (i.e. I don't think they used Lu-Hf).  However, it might be a starting point . . .

Good luck!

Dear Mr. He,

there are two modern-day natural occurences of radian barite, one in lignitic brown coal swamps in Hessia, Germany and another in Northern Bohemia, Czech Republic, related to hydrothermal solutions.

The specific activity of ²³⁸U in barites from the Ohrĕ (Eger) Rift, Czech Republic, is very low while that of ²²⁶Ra reaches 8 Bq/g (Ulrych et al. 2007). Therefore, ²²⁶Ra is not inequilibrium with its parent uranium. These ‘‘radiobarites’’ are not older than 10–15 ka.

Although I am not a radio-chemist and hence I cannot answer your question to the full extent, I hope this information will bring you bit closer to a solution.

Best regards

H.G.Dill

Dear Dr Md. Salah

Actually i am working totally in REE species. The REE (e.g., La) less affected by diagenesis when go down to ground profiling even though the iron is REE transporter.  However regarding the lanthanum - As-DOC or anaerobic  condition in  where intention on the role of humic and fulvic of REE in groundwater system. How far the reactive and conservative behavior between thus metal ions also play important role either in dissolve or solid state be considered. The rebound problem should consider of Mn oxide or coated Mn-Fe-Ox-hydroxide complexation between dissolve and particulate before scavenging to surface sediment until certain level of equilibrium. Again according to your research kindly, please refer:

Johan Schifjf, Emily A. Christenson and Robert H. Byrne 2015, YREE scavenging in seawater:  A new look at an model. Marine Chemistry

Robert H.Byrne and Ki-Hyun Kim, 1990. Rare earth element in seawater. Geochemica et Cosmochimica Acta.

Hein de  Baar and Johan Schijf,1991. Solution chemistry of rare earth element in seawater. Europe Journal of Solid state and inorganic Chemistry.

Regard's

Zolhizir Daud

If you sinter the material in a vacuum or hydrogen furnace, you can take simply a crucible made of molybdenum foil.

Hi Amanda,

Closer to home (i.e. in NZ) there are two labs potentially able to help. One is at the University of Otago; contact Dr Robert van Hale (robertv@chemistry.otago.ac.nz) or Prof Russell Frew (russell.frew@otago.ac.nz). The other is the GNS Stable Isotope Lab in Lower Hutt; contact Andy Phillips (+64-4-570 4620; http://www.gns.cri.nz/who/staff/2253.html).

In OZ you could contact Assoc. Prof. Grzegorz Skrzypek at the University of Western Australia (grzegorz.skrzypek@uwa.edu.au); Kim Baublys at the  University of Queensland; (k.baublys@uq.edu.au); Dr Jim Carter at the Queensland Health & Forensic Science Service (Jim.Carter@health.qld.gov.au).

Whoever you choose to contact, plase, by all means mention my name and give them my best regards. I happen to know all these people on a professional level (and almost all on a personal level too) and I know they do excellent work.

Best wishes,

Wolfram

Radiometric ages of minerals from different halite formations have produced various results, as noted above. Some show results generally consistent with the depositional age derived from other methods. Some radiometric ages of crystals from the Salado Formation in New Mexico are reasonably consistent with the inferred age of deposition. Other results may be indicating post-depositional events, but I haven’t run across a framework for differing minerals and techniques in various types of salt deposits that might provide a better guide as to how to generally interpret or propose different techniques for a specific purpose.

Textures and features have been described that are accepted as indicating “primary” halite in salt deposits that have undergone varying degrees of alteration since deposition. Lowenstein and Hardie (1985) provided a good framework, partially building on previous work, and subsequent studies have used these and added features/textures. We (Holt and Powers, 1990, 2011) recently described very coarsely crystalline halite (commonly called “recrystallized”) in the Permian Salado Formation, where syndepositional halite cements filled dissolution pits/pipes that developed on the subaerially exposed halite pan. This doesn’t make all coarsely crystalline halite “primary” or syndepositional, but it removes the automatic assumption that such crystals are automatically assigned a post-depositional origin. So, there are some indicators, but in heavily deformed rocks, these can be rare to (probably) non-existent.

I disagree with the notion that halite deposits are inherently open (permeable) deposits.  Potassic salts have long been considered the consequence of potassic metasomatism. Yet much evidence in at least some deposits contradicts this hypothesis. Lowenstein and Spencer (1990), for example, found KCl crystals within primary halite. Casas and Lowenstein (1989) found halite beds being cemented after deposition, limiting the effects of near-surface diagenesis. Fluid inclusion compositions have been interpreted for a long time as evidence of seawater chemistry at the time of deposition, and this would not be practical if the deposits were open to infiltration of unsaturated solutions. Beauheim and Roberts (2002) provided evidence of the extremely low permeability of Salado halite, which, if Darcy’s law has any applicability at all, indicates the system is not open to infiltration.

Your original question ended with the concern that “results/ages could be (always) interpreted without any doubts.” This is a universal issue, but salt results seem a little more “doubtful” at this time. My opinion is that suites of results will provide more confidence, but I don’t think some of these mineral systems are well understood for such things as the range of conditions under which Ar, for example, is retained/released. Or they are just pretty susceptible.

Hi,Dominlik. You should use 206Pb/238U when the zircon age is less thank 1000ma, and use 207Pb/206Pb when the zircon age is more thank 1000Ma.

In my opinion, we have to re-think about the location where the EMII and other mantle sources of basalts are residing. In a convecting mantle it is hard to expect that the positions of these are fixed in space and time. If we are to assume that the basaltic volcanism we see today is a result of mixing and/or melting in these reservoirs, then there is the need that  those should reside in relatively fixed positions for relatively large geological periods of time, for those processes to take place in the manner we envisage them. This is likely to happen only in a layered sub-continental lithosphere.

I would suggest getting in touch with Geoff McDonnell, mentioned by Douglas Burns above, for a more balanced approach to the question. Bootstrap and similar techniques (like Monte-Carlo) may not be the best approach, depending on the processes occurring in your system, and the available data.

Dear Mr. Chatterjee,

Quartzites often contain apatite, monazite and / or zircon crystals. If you find in your quartzites grains that are at one tenth of a millimeter in diameter, and contain at least 10 ppm uranium, then you should try the fission track dating methods.

Please compare two of my publications dealing with the apatite fission track dating method.

Best regards,

Guenter Grundmann

But from this reference for a start, you can trace backward and forward more references that are relevent to the boninites in Papua New Guinea:

You can refer to Materials and Methods section in article entitled : Recovery of temperature records from slow-growing corals by fine scale sampling of skeletons by Anne L. Cohen1 and Simon R. Thorrold (2007), GEOPHYSICAL RESEARCH LETTERS, VOL. 34

link: http://onlinelibrary.wiley.com/doi/10.1029/2007GL030967/pdf

Regards

Massih

First of all, it should be noted the name deuterium (and tritium) has been "outlawed" by IUPAC as of 2005. Instead 2H (and 3H) should be used at all times since 2H is not an element in its own right but a stable isotope of 1H. I know it's hard to break with tradition but there it is.

As for the question of d2H values of butane and isobutane (pentane / isopentane) being different even though they are all part of the same natural gas sample, it all comes down to how these compounds are being formed.  (non-quantitative) Reactions involving the breakage (or formation) of a C-H bond (any chemical bond actually) are subject to mass discrimination resulting in isotopic fractionation that will affect the bulk 2H composition of the reaction product more than it will its bulk 13C composition.  This is due to the link between reduced mass and bond strength (and bond length). The weaker 12C-1H bond will be broken preferentially over the stronger 12C-2H bond; even the 13C-1H bond is weaker than the 12C-2H bond. The overall isotopic fractionation factor for C may be as little as 1.0001 resulting in changes in d13C values behind the decimal point whereas the overall isotopic fractionation factor for 2H may range from 1.053 to 1.159 resulting in difference in d2H between precursor and product from approx. +40 to +146 ‰.

For example, biochemical de-novo formation of fatty acids and steroids (terpenoids) start both from acetate (acetyl-CoA).  While d13C values for saturated fatty acids and terpenoids of similar C content are fairly similar, their d2H values differ by 80 to 120 ‰.

Hi Praveen,

Stiller et al. (1985) is a good classical example for an evaporitic system.

Both, 18O and 13C of the precipitated CaCO3 depend on the isotope composition of the dissolved carbonate group. Degassing of CO2 from supersaturated aqueous solution leads to the enrichment of 13C in residual DIC. Therefore, since both the distribution of 13C and 18O of the individual dissolved inorganic carbon species depend on pH (e.g., Beck et al., 2005) it will also vary with biological activity, salt contents (e.g., ion pairs-look on the original experimental literature from the 60s and 70s)  and most likely precipitation rate. Biological activity may, therefore, also impact the signal via pH or kinetic effetcs as well as later recrystallization reactions.

Good luck, Michael

You can buy these PFA Barrel Spray chambers pre-made from ESI.

We use ammonia, yes, and it works well.

Dear Mr. Costa,

maybe you can find some ideas how to tackle your chemical problems of Cr in ultrabasic rocks, e,g, dunite and harzburgite:

Chromite Ore - Characterisation through to processing Australasian Institute of Mining and Metallurgy Publication Series, 2008, Pages 339-351McCallum, D.A. | Bruckard, W.J. | Pownceby, M.I.

Preparation of Four Chromium Ore Reference Materials (Geostandards and Geoanalytical Research Volume 37, 2013, Pages 95-101 Cheng, Z. | Huang, H. | Liu, M. | Gu, T. | Yan, W. | Yan, M.

Analytical and mineralogical studies of ore and impurities from a chromite mineral using X-ray analysis, electrochemical and microscopy techniques Talanta Volume 74, 2008, Pages 1592-1597Sánchez-Ramos, S. | Doménech-Carbó, A. | Gimeno-Adelantado, J.V. | Peris-Vicente, J.

Chromitite and platinum-group-element mineralization at middle arm brook, central advocate ophiolite complex, Baie Verte Peninsula, Newfoundland, Canada Canadian Mineralogist Volume 49, 2011, Pages 1523-1547Escayola, M. | Garuti, G. | Zaccarini, F. | Proenza, J.A. | Bédard, J.H. | Vanstaal, C.

Petrology of Al- and Cr-rich ophiolitic chromitites from the Muǧla, SW Turkey: Implications from composition of chromite, solid inclusions of platinum-group mineral, silicate, and base-metal mineral, and Os-isotope geochemistry Contributions to Mineralogy and Petrology Volume 158, 2009, Pages 659-674Uysal, I. | Tarkian, M. | Sadiklar, M.B. | Zaccarini, F. | Meisel, T. | Garuti, G. | Heidrich, S.

Dunite xenoliths and olivine xenocrysts in gabbro from Taihang Mountains: Characteristics of Mesozoic lithospheric mantle in Central China Journal of Earth Science Volume 21, 2010, Pages 692-710 Xu, W. | Wang, C. | Yang, D. | Wang, F. | Pei, F.

Tibet Luobusa different types of characteristics and genetic model chromite discussion Acta Petrologica Sinica Volume 30, 2014, Pages 2137-2163 Xiong, F.H. | Yang, J.S. | Ba, D.Z. | Liu, Z. | Xu, X.Z. | Feng, G.Y. | Niu, X.L. | Xu, J.F.

Chromium in olivine occurrence: Tibet Luobusa mantle peridotite and chromite-rich olivine and implications for chromium causes of deep mantle Acta Petrologica Sinica Volume 30, 2014, Pages 2125-2136Liang, F.H. | Yang, J.S. | Xu, Z.Q. | Zhao, J.N.

Best regards

Harald G.Dill

Did you run the pattern through CrystalSleuth against the RRUFF database ? If you send me a copy of the spectrum data in CSV format I can run it against a RRUFF extract that is both cleaner and more extensive than the one released with CrystalSleuth from the RRUFF website.

Dear Mr. Hassan,

I agree with Dr. Towe, that the anomalies of Ce and Eu play a significant part, particularly Ce which responds to redox changes that are fundamental in the mobilization (organo-metallic complexes), thransort (chelat complex) and concentration of iron. You will find a lot of case studies of  these anomalies, also in papers dealing with a different set of elements or metal deposits. I would like to refer also to the classical studies covering Fe-bearing ochres of the deep sea, BIF and ironstone deposits quoted in Maynard (Geochemistry of Sedimentary Ore Deposits). He listed some of the REE elements. Investigations of the isotopes should not only focus on oxygen but also on carbon which is present in the afore-mentioned carriers of Fe and also in one of the most important Fe host minerals siderite (+ ferroan dolomite), both of which show up in  ironstones too.

Best regards

Harald G. Dill

Concentrations of Pb are likely to be rather low, especially in cpx. This may make it more difficult to get very precise measurements, especially if you want to use ratios over 204Pb. Clinopyroxene is not stable at greenschist facies, so if you still have cpx in the sample, it must be a relic, and hopefully not much affected by metamorphism. For plagioclase, you would have to check whether it is still the original igneous plagioclase, or that it has been metamorphosed to albite. I do not know the age of your samples, but if they are more than a few Ma, then you will also have to correct for the presence of U and Th that will have decayed in the mean time.

Yes, But we do not want to wait for four months to do Pb-210, so selected this method and want to compare this indirect method with Pb-210 gamma method. If anyone has tried this method we have mentioned, please suggest a solution?

Dear Jean-Michel, 

Thank you to your opinion/suggestion. We will try to split the dataset and to use separate trophic enrichment factor for primary and secondary consumers, but how to deal with intermediate consumers?

And of course, I agree with you that a deep knowledge of the trophic web is necessary before to use mixing models.

Merci.

Hi, the following article might be useful for you.

1. Interpreting magmatic processes from accessory phases: titanite—a small-scale recorder of large-scale processes.

2. DISTRIBUTION OF TRACE AND RARE EARTH ELEMENTS IN TITANITE FROM TUNGSTEN AND MOLYBDENUM DEPOSITS IN YUKON AND BRITISH COLUMBIA, CANADA.