I've been looking up references for Moacyr Monazite.
https://probesoftware.com/download/BoT&A_Jercinovic.pdf (https://probesoftware.com/download/BoT&A_Jercinovic.pdf) refers to https://www.sciencedirect.com/science/article/pii/S0009254108001927 (https://www.sciencedirect.com/science/article/pii/S0009254108001927) neither of which contain elemental composition
https://www.sciencedirect.com/science/article/pii/S0009254117306228 (https://www.sciencedirect.com/science/article/pii/S0009254117306228) states and refers to "We had some large pieces of monazite crystals, one from Itambe given by a Brazilian friend (that crystal would be later known as the "Moacyr" sample, Goncalves et al., 2016)" https://www.sciencedirect.com/science/article/pii/S0009254115301315 (https://www.sciencedirect.com/science/article/pii/S0009254115301315) which has a slightly different composition to Julian's paper https://iopscience.iop.org/article/10.1088/1757-899X/891/1/012001 (https://iopscience.iop.org/article/10.1088/1757-899X/891/1/012001) persumably reflecting different pieces
Other papers including composition incl
https://www.sciencedirect.com/science/article/pii/S000925410900285X?via%3Dihub (https://www.sciencedirect.com/science/article/pii/S000925410900285X?via%3Dihub)
Also https://www.sciencedirect.com/science/article/pii/S0009254102001559 (https://www.sciencedirect.com/science/article/pii/S0009254102001559) which "We would like to thank very much Moacyr Marinho who kindly provide us the monazite sample."
Also https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009TC002514 (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009TC002514)
And Guilherme de Oliveira Gonçalves et al explain "One widely distributed monazite U/Pb standard comes from the Itambé pegmatite district of Bahia State (E Brazil), and is known as either "Moacyr" or "Moacir" monazite in the literature. This pegmatite district forms the northern extent of the Eastern Brazillian Pegmatite Belt, which continues southwards into the 630-480 Ma Araçuaí Orogen. "Moacyr" monazite was originally collected by a Bahia State Geological Survey geotechnician and was subsequently distributed to several research groups by Prof. Moacyr Marinho. However, the exact sampling locality was not recorded and the Itambé pegmatite district contains three different large pegmatites (the Bananeira, Coqueiro and Paraíso pegmatites)" in "The origin of the Moacyr monazite standard – elemental and isotopic constraints"
I am reminded of a suggestion to create some synthetic monazites for testing measurement accuracy of trace U, Th and Pb:
https://smf.probesoftware.com/index.php?topic=928.msg8506#msg8506
Attempts to create a synthetic monazite in the past has had issues with sector zoning, but for the purposes of a blank matrix for testing trace U, Th and Pb, this would actually be a good thing. As it could test the accuracy of zero concentration measurements in multiple compositions of Ce and other rare earths.
Quote from: Probeman on June 03, 2025, 01:13:38 PMI am reminded of a suggestion to create some synthetic monazites for testing measurement accuracy of trace U, Th and Pb:
https://smf.probesoftware.com/index.php?topic=928.msg8506#msg8506
Attempts to create a synthetic monazite in the past has had issues with sector zoning, but for the purposes of a blank matrix for testing trace U, Th and Pb, this would actually be a good thing. As it could test the accuracy of zero concentration measurements in multiple compositions of Ce and other rare earths.
Does not pure REEPO4 fill that function already?
Quote from: sem-geologist on June 04, 2025, 05:55:14 AMQuote from: Probeman on June 03, 2025, 01:13:38 PMI am reminded of a suggestion to create some synthetic monazites for testing measurement accuracy of trace U, Th and Pb:
https://smf.probesoftware.com/index.php?topic=928.msg8506#msg8506
Attempts to create a synthetic monazite in the past has had issues with sector zoning, but for the purposes of a blank matrix for testing trace U, Th and Pb, this would actually be a good thing. As it could test the accuracy of zero concentration measurements in multiple compositions of Ce and other rare earths.
Does not pure REEPO4 fill that function already?
Not really. This synthetic would be intended as a test material for measuring certain trace elements in a matrix similar to a natural monazite, but with zero concentrations of specific trace elements.
The idea is to create a synthetic monazite with the typical menagerie of REE elements, but with (for example) zero U, Th, and Pb. Some synthetic REEPO4 materials are contaminated with Pb, and for those not contaminated with trace Pb, a single element REE PO4 material isn't complex enough to create a material similar to a natural monazite for the purposes of testing one's ability to measure zero (a zero blank material) for testing various background modeling methods, e.g., multi-point bgds.
See here the paper attached to this post:
https://smf.probesoftware.com/index.php?topic=131.msg8659#msg8659
and also this presentation from Karsten Goemann attached below.
IMHO this very nicely showcase the problem of Multi-background method. With negative net intensity overlap correction (correcting negative overlap made by overlapped background positions, which is included in Cameca Peaksight starting from 6.5) I have no issues to correct all REE for Th, U and Pb b.d.l. (all Mα lines, no Mβ lines) with single off-line position per measured element.
Moreover having every single REE in separate standard does not "mud the water" and it is exactly clear where the overlap problem is originating and allows precise and proper mitigation of it with active or passive correction. Also, what is crucial at measuring trace level amounts, single offline position has ability in most cases to stay at same side as measured peak in relation to the absorption edges, where with multi-point it would not be possible by design.
The keyword here is pure REEPO4. It is known that there are some older REEPO4 in the market contaminated with Pb (proven with LA-ICP-MS). There are also some highly likely false claims of Pb contamination of some REEPO4 measured by EPMA (ignoring overlaps of 2nd, 3rd and 4th order of REE lines, which is impossible to completely filter out using PHA diff.).
Quote from: sem-geologist on June 05, 2025, 01:34:18 AMMoreover having every single REE in separate standard does not "mud the water" and it is exactly clear where the overlap problem is originating and allows precise and proper mitigation of it with active or passive correction.
I think you misunderstand my point regarding the idea of creating a synthetic monazite with multiple REE elements and zero U, Th and Pb. As one can see (if one read the Allaz et al. paper and the Goemann presentation carefully, one would have seen) that pure REE PO4 materials were utilized to test the MPB method.
The point about creating a mixed REE synthetic with known (zero) concentrations of particular elements is that it would simply provide more convenience for performing a quick check on the accuracy of one's ability to measure zero in such a matrix. Surely you can understand the efficacy of having such a material if one routinely measures complex REE materials.
Regarding your claims about using a single point background, I suppose it all depends on the sensitivity and accuracy required by the user. For ultimate sensitivity and accuracy the MPB method clearly produces the best results.
Quote from: Probeman on June 05, 2025, 08:35:13 AMRegarding your claims about using a single point background, I suppose it all depends on the sensitivity and accuracy required by the user. For ultimate sensitivity and accuracy the MPB method clearly produces the best results.
Dating monazites requires all sensitivity and accuracy the instrument can provide and more. That is the reason why I moved whole our measuring strategy to single background measurement per peak and I can't see how it would have less sensitivity and accuracy compared to MPB. 1) It is quite clear that spectrometer time spent for measuring single point in spectra, instead of many points (of background), will give least deviation of background; It even more obvious taking into consideration that MPB would throw out outliers - thus there is no possibility that MPB would be more sensitive than single background, given same measurement time and electron dose. Unless MPB is extending space time continuum... which I doubt :D .
2) The very existence of this post and declared need of some specific monazite (Hello darkness, my old friend, or matrix matched standards...But its different, but sounds the same, but different :D) shows that there is a base for accuracy doubts for MPB. Single offset per peak does not care about that, if "Zero" for Pb, Th, U (<DL of 20ppm) is achieved for all pure REEPO4 - that means it will stay zero with mixture of those. The slope for offset does not change - no need to recheck with different composition monazites.
3) more over, There are other potentially datable minerals like Xenotime, Chevkinite and other Th/U bearing REE minerals, The fixed composition synthetic monazite would address only the similar composition, and would assure accuracy only to similar composed monazites for MPB method. On other hand slope for correctly chosen single offset background does not change with Z (unless applying different HV). With single background offset method there is practically no reason to recheck if everything works as intended, as it simply works as intended in month, year, decade with different REE matrices.
We generaly try to get rid of matrix matched standards, or we don't?
Quote from: sem-geologist on June 06, 2025, 06:12:11 AM1) It is quite clear that spectrometer time spent for measuring single point in spectra, instead of many points (of background), will give least deviation of background; It even more obvious taking into consideration that MPB would throw out outliers - thus there is no possibility that MPB would be more sensitive than single background, given same measurement time and electron dose. Unless MPB is extending space time continuum... which I doubt :D .
I am not referring to the theoretical sensitivity, but rather how to determine the actual sensitivity empiricially. A single background measurement is like a single peak measurement: one is unable to determine the actual background reproducibility for that composition.
Yes, one could assume that the only variance in the measurement is due to counting statistics, but there can be many other sources of variance in the background intensity measurement. The MPB method allows one to actually determine the background variance in every measurement as opposed to assuming it is solely due to counting statistics.
Quote from: sem-geologist on June 06, 2025, 06:12:11 AM2) The very existence of this post and declared need of some specific monazite (Hello darkness, my old friend, or matrix matched standards...But its different, but sounds the same, but different :D) shows that there is a base for accuracy doubts for MPB. Single offset per peak does not care about that, if "Zero" for Pb, Th, U (<DL of 20ppm) is achieved for all pure REEPO4 - that means it will stay zero with mixture of those. The slope for offset does not change - no need to recheck with different composition monazites.
If, as the unknown monazite composition varies, that single background measurement is interfered by a greater or lesser degree, one will lose accuracy. And even worse, one will have no idea that this additional error has been introduced. The MPB method allows one to see these changes in the background by measurement. Yes, using the one point/slope method one could specify a different background slope for every composition, but unless one has a synthetic monazite of every possible composition and with known zero concentrations of U, Th and Pb, one cannot test that assumption.
A single synthetic monazite of variable composition but with zero U, Th and Pb will provide that critical information.
Quote from: sem-geologist on June 06, 2025, 06:12:11 AM3) more over, There are other potentially datable minerals like Xenotime, Chevkinite and other Th/U bearing REE minerals, The fixed composition synthetic monazite would address only the similar composition, and would assure accuracy only to similar composed monazites for MPB method. On other hand slope for correctly chosen single offset background does not change with Z (unless applying different HV). With single background offset method there is practically no reason to recheck if everything works as intended, as it simply works as intended in month, year, decade with different REE matrices.
We generaly try to get rid of matrix matched standards, or we don't?
Again you misunderstand. These synthetic materials with sector zoning variations in composition would not be utilized as primary standards, but instead only as zero blank materials for checking trace element accuracy by measurement.
As for primary standards, for best sensitivity (if one examines the equations for detection limits), one should always utilize a primary standard with the highest intensity of the element per concentration. That is usually the pure element or oxide.
https://smf.probesoftware.com/index.php?topic=1535.msg12121#msg12121
In summary, rather than assuming sensitivity and accuracy, I prefer measurement of both sensitivity and accuracy. The MPB method combined with such a blank material would empirically provide that information.
Regarding Ben's original comments about Moacyr, these are certainly spectacular megacrysts from the famous Brazilian pegmatites - all described nicely in Goncalves et al. The thing is the sector zoning that is typical of igneous monazite. So indeed the composition ranges quite a bit over a scale of centimeters (more or less). The pieces we use for consistency checking are of course only valid for that particular piece - we just want to know how it is doing each day to see if anything has changed. Obviously we have lots of data on these, but that information is of little use to anyone else. We can only evaluate it based on our own history, and on the dates that we have accumulated by EPMA, and elsewhere by TIMS, SIMS, and LA of pieces of the same large crystal. So maybe the age looks a bit old and we look at the concentrations and see that Th is a bit less than what we usually get. Then recalibrate. We never actually calibrate anything using Moacyr, it is only a secondary reference, and this will be the case for any natural monazite.