little slab off off the off the flake to make it transparent it has to be thinned down to about under a millimeter and then we simply pass the infrared beam through it and it gives us our our um our structural water 4500 okay and it gives us this what we call combination peak of OH and H2O at 3750 so to get mass gain we need uh mass gain is contained within this peak right it's contained within this peak here oops sorry mass gain and hydroxyl arcane are this this peak is like a summary statistic so what we want to do is convert the structural water into the absorbance here uh using the extinction coefficients for the more absorptivities and then because this peak will come in just under the big under the 3570 peak so it's always going to be less and so the difference is the mass gain that's occurred over time so this little trick which is the innovation here is that we we want we convert we convert 4500 you know the absorbance of 4500 the absorbance of 3570 and subtract the two and we're able to do that because we know the more the more actual activities you know this ratio between the two we apply that ratio to the absorbance at 4500 we get a conversion so so uh so you get a mass gain so you have two we have two critical variables that we need to compute a rate a date we have a mass gain uh molecular water and we have a structural water concentration that allows us lots to predict the velocity but what about error so we looked at we looked at our errors uh coefficient variation because we have four potential potential contributors of error the absorbance density thickness and then extinction coefficient and we looked at we looked at those individually and and there's some and the sum there and we come in at an error of about 1.3 percent for those four different four different measurements net net so this this error applies to calculation of structural water this this error applies to the calculation of of gain molecular water gain or hydration gain so because you're measuring two two peaks on the same sample um density and thickness cancel out of the equation um but their contribution to the equation to the error is almost infinitesimal so you basically end up with the same error just under two percent so that that's encouraging so we have we have the variables that we need to calculate our rates um we have uh we have our our structural water we have our mass gain and of course hydration the fusion processes are temperature dependent and so the hydration temperature is estimated soil growth of humidity is estimated and then uh below this are our our our calibrations that that relate structural water to hydration rate so we get for the arenas equation that allows us to implement to extrapolate from our high temperature experiments at 150 degrees um we developed prediction equations for for the activation energy and for the pre exponential and so this is the pre exponential this is activation energy and that is used to calculate the hydration rate in absorbance for your archaeological article so um so it's all kind of cut and dry right now so it's the methodology set up these are easy equations um they they look coherent but we're still in the evaluations processes though how widely applicable they are so this is so this is the method for um for opaque insidians uh but but it does it does have its problems right it's destructive um uh and samples aren't transparent so you know a lot of insidians you know have to be um you know samples have to be thin and then the biggest drawback is in this is in this uh conversion process with a small amount of error for the 4500 measurement for the 4500 peak becomes amplified because you're actually multiplying it 125 so uh so you end up in the four to five percent error range so that's not that that's not good um it's not tedious but it's not good and so there's room for improvement there um so the our next step um this has been to say what can we do for transparency so looking at all all the insidians in mexico in the boxes this has some uh applicability there and the there's a there's another water band out here for 5200 that we didn't look at in this first application because uh because in the mid-air for it um you know you have a your water diffusion zone it might be only one micron i shouldn't say that i can't say it there uh it might be it's going to be you're going to have very very low molecular molecular concentration on the surface and so that 5200 band is is not very sensitive in the mid infrared but that's because the mid infrared loses energy in this region but if we shift to we just simply change the source in the same instrument uh to a flight light source our our energy our energy our background energy um becomes very high in this region now and so we can measure the 4500 peak you see here and we can measure the 5200 4500 peak is your structural water and then this 5200 peak is your surface water so uh we get both variables that we need without any any subtraction and without any um uh conversion um and and this now becomes detectable uh non-destructive under and so but how precise is it well don't quite know yet these results are only about three days old but one of our samples is also con that has an optically measured hydration layer of two microns um and um what this green peak represents is actually four microns because the infrared beam passes through two sides of the artifact so it picks up two surfaces so it doubles the response so uh you simply have to divide the the absorbance in half which you can see here for like the uh the red the red um the red spectrum is the shulveria source in georgia and um this is from shulveria shulveria gora um it's a site about 5000 years old um and it has a well developed peak as well so um um this if you have a transparent obsidian um the analysis of uh degree of hydration comes substantially easier and um and and straightforward and it becomes non-destructive um then what reason becomes non-destructive you do have um but we still have to calculate concentration we still need a sample thickness in the way we the way we get around this irregularity of artifacts is that we aperture down to a very very small area and so essentially there's no lateral variation in the thickness anything is one millimeter aperture so that allows us to to calculate beer's lock for our structural water so that's a lot to absorb in 15 minutes but uh i think the hydration dating had now had a new approach uh it's it's consistent with the theory and um you want to try it out and let me know thanks very much thank you christopher yeah that's a lot that's a lot to take in that's a lot to take in actually it's very simple it's actually two analytical steps um for for opaque obsidians and it's just one analytical step uh transparent for the for the what i just showed you on the for the transparent material and you put your sample within the beam path of the spectrometer 30 seconds later your analysis is done so it's it's gotten substantially easier over the years any any question can i ask you yes please uh with a huge respect christopher thank you for the interesting presentation my question may sound a little bit stupid but i want to ask you so uh how hard it will be to use the method you described for the sources which has very extreme environment i mean the for example very high percentage of precipitation and so on how it will affect on your methods thank you precipitation um well the most artifacts will be in the ground and um you'll have you'll have the rainfall you can have white precipitation but as long as the soil is maintained at 98 percent humidity you're fine okay the the rainbow the rain is not going to road the artifact it's only if the if your soil ph is very outgoing and you have heavy rain that will start to dissolve the artifact you know with exposure over the centuries thank you yeah that's been very noticeable in places like you know central america and so on who i think i went over i'm sorry and no problem so we're in the midst of a little coffee break here we'll resume the the next paper in about 10 minutes so feel free to take a little short break or if you want time for some extra questions some of us are here that have talked earlier in the day i was really excited about this approach because you know for years you know i've been cutting and grinding up obsidian and uh stringing the porous and tedious correct isn't that right correct and you know in my dissertation i think i did 900 slides you know grinding each one down i just said i'm not gonna do this anymore and it took a while to develop a method like this that the one of the impetus impetus one of the imps this is for doing this is that you know the much harder to do obsidian dating destructible you know as you as chariots put new rules on it and indigenous groups don't want their your artifacts destroyed and so that the directive is to come up with a non-destructive method and maybe in the other part of the world it's not an issue yet but i'm sure it will be probably will be and sometime in the future so uh it's kind of it's kind of it's kind of merges with the upcoming policy of archaeological analysis so that's kind of good thing yeah so um but you know i'm always you know it's hard to come up with really good test cases because of the difficulty just finding stratified deposits just finding you know their obsidians and just finding cities that haven't been you know altered by post-death positional operation and then the issue that hasn't been discussed here is the it's the actual estimated thermal history and i know it's Steve Steve brandt is still here um you know working in in africa and on these very old sites you know i'm here hey there it is uh working in these very old sites coming up with a long-term estimate of temperature is is quite not very difficult we have a solution to that i think and that is why looking at the refractive index of the surface diffusion zone i'm just writing a chat message to you about the oh okay you can use it so we'll talk some more so uh but but it required but as it's done today it requires temperature monitoring of your archaeological site it just takes a year so uh you know signing your research is on you have to think a year ahead so you gotta put sensors in the ground for a year um that's it gets it's part way and you never know about the thermal history of the artifact you know it gets buried it's picked up and recycled you know it's transported hundreds of miles away those from the mount and down below so um that's that's a challenge but in areas uh for short short for short free histories you know it can work out pretty well um for very long free histories it's it's it's a challenge Bruce how do you think it compares cost-wise is it is it that's the other driver you know you can you can do great things with half a million dollar instrument like a synth machine right but it has to be it's usable so the infrared is uh basic instruments around 28,000 right that's that's really all you need um in this in this uh the results I've shown you here so you need a basic fTII you don't need any fancy options on it you know a white light source um and so that so that's like a good microscope is like $15,000 to do it the traditional way you know for $2 more you know you can you can have a new technology but you know the spectrum is our name it's they're not being in the street it's five years you have to buy a laser it's kind of like those xrf machines they break down um so that's why pep talk for obsidian dating I hope somebody uh takes me up on the offer if you have a clear obsidian you have dark obsidian don't talk back from our our short break our next paper is titled archaeological significances and geochemical characterization of obsidian sources in central highlands central japan by wavelength dispersed xrf and la icp ms by yashimitsu suda okay thank you for your introduction so let me share my desktop okay can you see my slide okay yes that's great okay all right let me start my presentation so it's great honor to be able to be join this visual meeting of international obsidian conference in baku so today I'd like to talk about archaeological significances and geochemical characterization of obsidian sources in the central highland central japan it is well known that there are five big or major obsidian sources around kanto plane which are called central highlands takahara yama hakone amagi and kozushima shimada etou indicates that the obsidian from central highland was most abundantly used as a lithic raw material in the kanto plane during apocalyptic also to look at the change in the use of obsidian in the kanto plane there are two big change in the use of obsidian from central highlands as the periods of the beginning and ends of late apocalyptic many researchers have been pointed out the relationship with the impact of lgm but the discussion based on the evidences of paleo climate change and human activities in this source area is quite insufficient so based on this the group of major university have been performed the archaeological excavation and paleo environmental research in helopolisites and bog at central highlands and yoshida etou reveals that during late apocalyptic the landscape of helopolisites and bog was characterized by alpine vegetation with rocky stretches and the tree line is located just around the level of helopolisites and bog after that the landscape was changed to be forested due to warming and rising of tree lines also more than 2000 of obsidian artifacts from early apocalyptic to german periods were excavated from this helopolisite we had already performed the archaeological analysis for these obsidian artifacts but there are still many difficulties on the provenance analysis of these obsidians so the aim of this study is to establish the methodology of provenance analysis of obsidian in kirigamine where the helopolisite bog and the site are located also to reveal the human activities concerning the procurement and consumption of obsidian in kirigamine source we try to improve the methodology of provenance analysis of obsidian artifacts to identify the procurement area and the point and this kirigamine source what you can see here is the locality of obsidian sources compiled by previous works the previous work has already already indicated that there are 21 points of obsidian sources in this kirigamine area and the obsidian in this area can be classified into these 11 chemical groups also looking at the locality of obsidian sources in this area it looks that there are no clear relationship between the locality of obsidian sources and their chemical composition so this indicates that to improve the provenance analysis of obsidian in this area we need to make clear the relationship between the locality of obsidian sources and their chemical composition for this we again performed the field survey and field sample collection in this area and 109 samples of geological obsidians were analyzed by WDXRF and laser ablation ICP-MS you can see here is the instruments for chemical analysis of obsidian used in this study all samples for analysis were used into such this gas speed at Nagasaki University and using this gas speed we performed WDXRF analysis at Meiji University and laser ablation ICP-MS analysis at Kyushu University the compositional data by this study and previous studies had indicated that the obsidian from these major sources and counter plane can be discriminated based on these variation diagrams okay now let me explain why the magma of different composition had been formed the first process first reason is the process of magma generation in other words the composition of magma source is different the second reason is the degree of magmatic evolution is different even though the magma source is the same let me explain further explain what is the magmatic evolution beneath the volcano magma is always gradually crystallized in the magma chamber during cooling so because of this process the composition of magma are also gradually changing we call this process magmatic evolution also in such variation diagram composition of variation diagram the first process is shown by such these compositional clusters for each magma source on the other hand the second process is shown by such this trend line for each magma source so namely chemical groups of obsidian can be classified according to the difference of magma source and degree of magmatic evolution you can see here is a compositional variation diagrams of obsidian in Kirigamine from this diagram we can identify five compositional cluster and one trend line these diagrams show the composition of obsidian in the trend line from these diagrams the obsidian in the trend line can be further classified into more eight chemical groups based on the degree of magmatic evolution so this study indicates that the obsidian in this area can be classified into these 13 chemical groups however looking at the locality of obsidian sources in this area the relationship between the locality of obsidian source and the chemical composition are still unclear so to perform the provenance analysis of obsidian in this area we need to recompile these chemical groups based on their localities let me show again the chemical groups of obsidian in Kirigamine the group forming the clusters can be classified into these five groups on the other hand group forming a trend line can be classified into these eight groups but taking into account also their localities these are recompiled into most evolved intermediate and less evolved ones you can see here is the locality of obsidian sources for each recompiled chemical groups as you can see here to perform this recompilation for these chemical groups the relationship between the locality of obsidian source and the chemical composition become rather clear based on this we perform the provenance analysis of 40 obsidian artifacts excavated from these helopora sites you can see here is the discrimination diagrams based on wdxrf analysis in this diagram the composition of obsidian artifacts are also plotted the result indicates that roughly two-thirds of obsidian artifacts were classified into these mt chemical groups and including some w, k, a, g, h, o1 chemical groups this result also supported by these discrimination diagrams based on laser ablation icp ms analysis so this study indicates that the prehistoric human center and this helopora site exploded obsidian at around the area close to this helopora site of course this study need more investigation and need more provenance analysis of obsidian artifact but this study was able to be shown the relationship, correlation between the locality of obsidian source and the chemical composition finally let me talk about our ongoing studies for the provenance analysis you can see here is the instrument installed in our laboratory of course these instruments have both advantage and disadvantage on the analysis of obsidian artifact but based on this we are going to establish such this methodology of provenance analysis of obsidian artifact flowing this flowchart also recently from presented such this open source collection of reference samples of obsidians we want to follow up this work also in our laboratory we are making such this a package for the collection of obsidian reference samples and nearly open the website of obsidian source online database we hope these become valuable resources to promote the provenance study of obsidian artifact in archaeology thank you for your attention that's all thank you yashimi too any questions hi hi yes a really interesting presentation and I observed it in a difference obsidian source that that the obsidian flows was the last eruption or the last volcanic event mm-hmm in the evolution of the magmatic chamber some process produce the obsidian at the last volcanic events yeah I can it's now I cannot imagine the volcanic activity itself in this area but so some of age data is obtained in this area but it's quite narrow at a range of a few million years so but so I these data compositional data indicates some different composition of magma flow or magmatic activity occurred in this area and so to look at this distribution I suppose the last eruption of of liotic magma produced such this obsidian is such this green green one because it overlaps the different another another kind of obsidian dissolution area but so it's still become it needs more investigation for the linkage of the geological interpretation it's okay yeah okay I believe your presentation are really important because you can define the chemical range the chemical change yeah and that means if it's really important to study the geological evolution of the volcanic process yeah yeah exactly and in in Mexico many obsidian source are around big volcanic mm-hmm calderas uh-huh yes what is the composition of variation yes and the the volcanic process start of a salty composition salty huh and after when the caldera a big explosion of the caldera the caldera fell down mm-hmm yeah yeah start uh radial fractures uh-huh fractures at these fractures after start to grow the obsidian domes uh-huh uh-huh yes yeah the chemical study mm-hmm identify different source difference uh-huh okay but uh according with your presentation is the same volcanic origin this the same magmatic evolution mm-hmm this is important because sometimes uh the chemical study said this obsidian is from here this obsidian is from here and is the same area yeah yeah exactly yeah yeah I convinced that so the composition of magma is completely represented in the composition of obsidian yeah it's very important to to the composition of the obsidian to reconstruct the volcanic history such like that I think so that so also I want I didn't mention that so this this source including some of the uh deposition derived by the derived derived from phylocraft stick from phylocraft stick also including including in this obsidian source such as takayama source is a is a deposition of deposition originated from the phylocraft stick from but so volcanic event is located here higashimo says I said that higashimochia so it must be uh volcanic event occur here and the volcanic phylocraft stick flow is yeah is flooded it's it's many around the area but so I uh detail of the history I cannot now reconstruct it I would also suggest that that applying you know perhaps dating techniques you know fission track dating or whatever might help untangle uh you know these complexities because you know these aren't unique uh to to just Japan you know there's all all around the world people are facing these issues and defining things yeah I think so that so we want to so perform such this so uniformed age dating analysis such as uh potassium argon dating of glass glass parts but so we need to uh uniform the method of the age dating method I uniform the method of age dating to compare the such this frequency frequency of the volcanic event I think so thank you thank you yes yes you should meet two uh very good presentation wonderful questions very very engaging topic okay thank you for your comment all right our next presentation is an inter instrument calibration and data comparison for xrf analysis of obsidian by robert tycott robert I hand it over to you thank you you can see me and hear me yes sir okay well I'm not sure that I'm talking to the right audience here about this because we pretty much know what we're doing but keep this in mind for all of your colleagues people you may share your instruments with uh and that kind of thing okay I'm going to talk some more here about the use of a portable xrf how we calibrate the data that we produce focusing specifically in the mediterranean area dealing with archaeological and geological data and comparing this a bit to analyses that have been done by other methods as you know there are both advantages and limitations to using xrf instruments I'm not going to read through this whole list here but in particular the potential for doing non-destructive analysis on artifacts that's become a very big issue these days on archaeological samples the ability to transport the instrument to doing work in the field or museums especially in foreign countries how quick you can do it what it costs and those kinds of things those are the pluses involved here but we always have to keep in mind the limitations we're not putting out of business doing neutron activation and icp and other kinds of analytical methods here in particular we're only getting results on the surface of the sample so if we're being non-destructive that's not the same thing as what we get with those other analytical methods in the case of obsidian we usually don't have too much problems with weathering or contamination you know we're not doing pottery or something here but nevertheless that's just something to keep in mind and in particular again where we're analyzing original samples heterogeneity while we call obsidian glass it's not quite the same thing there can be in different sources of obsidian different kinds of crystals and so on accumulated in there and so where we're going and analyzing what spot we're doing that can have a bias in there as well and then we've heard today in some of the recent presentations issues where we're dealing with how thin the sample is or is it so small it's not even covering the area that the x-rays are coming out of the instrument we have to deal with that as well okay time to move on from this we already have seen where the different sources are in Europe the four islands that belong to Italy two for Greece and then parts up in Hungary Slovenia and that other country up there Ukraine right okay and we know what obsidian looks like how you have cores producing various kinds of tools and we have different kinds of research questions depending on our particular projects where the particular cores are being produced compared with the final products and so on I'm not getting into that here today but ultimately we want to go and match where the artifacts are found compared with their geological source and deal with what kind of distance trade routes etc etc how they change over time. In some cases it's possible simply from visual examination to distinguish some sources but I'll just say right off the bat in the Mediterranean and in the area in particular that I'm working on today that's not sufficient by itself we have to do some kind of chemical analysis and in particular when we're dealing with subsources and not just the general difference for example between liperi and pantilleria. I also don't really need to show you the periodic table here but again to emphasize the difference between portable xrf analyses and what is being done by ina or icp for the most part we're focusing on five trace elements maybe adding the iron and a couple of other elements in as well and so we just have to keep that in mind again also for various issues concerning the settings that we have for the pxrfs in particular dealing with lower elements where they are getting the x-rays get absorbed in the air but that's not the situation for these five trace elements without even doing any kind of calibration if you want to just go and compare results that you get from geological samples with your artifact analyses just looking at the peaks you can go and see how good an overlap in all that we have here for the iron and those five trace elements over here clearly coming from the same place whereas in the case in the lower graph clearly coming from different sources with the red having less strontium but more rubidium and zirconium and other elements here and so this brings up a little bit ahead here is the whole issue of how do we compare one set of data done with another set of data and I can just say right off the bat I've been using a pxrf for 15 years but not with the same pxrf instrument I have gone through more than a half dozen different ones and so I've beaten around the bush I guess by reanalyzing the geological samples that I have with each one so I don't have to worry about the calibration in that sense but I'll come back to that again a bit more here anyway the just showing the latest instrument that I have and I know some others again have these two okay I'm specifically focusing here on the research that I'm doing in the central Mediterranean and particular in the area within the green ellipse here where there's a whole bunch of potential geological sources being represented coming all the way from sardinia and leapery and palmarola in the Turinian coming all the way from Melos off the map here to the east and also from the Carpathians up here in the northeast and in addition and I've shown this in some other work and we'll show once again how important it is to distinguish the subsources within each of these islands or other source areas and this I discovered back in the 1990s looking just at this one site as my first investigation on sardinia where looking at the difference between the sources a b and c how they changed in their usage over time from the early Neolithic to the later Neolithic with the sardinian c subsource becoming the dominant rather than a minor portion okay and so this is why it's really important to assign artifacts to subsources and deal with the modest chemical differences between subsources versus comparing simply sardinia with leapery and other central Mediterranean groups okay I forgot what I was going to say about this but just showing it basically with pxrf and just using a few of those trace elements rubidium niobium and strontium how we can go and distinguish palmarola from leapery from sardinia pantalaria milose and and carpathians you'll also notice why as some questions why is it such a broad variation for milose well that's because we're doing a ratio here and the amount of niobium is very low so simply the numeric statistical part there is why that is so widespread but in any case fairly straightforward to distinguishing between the different islands but yes here in the carpathian area where there's many source groups and subgroups and I thank katalin for organizing the team meeting there and the opportunity to collect a bunch of geological samples showing that again just using a few of the trace elements we can go and distinguish things into separate groups but also notice some things which do not separate as easily the 1a versus 1b and and so on okay coming back to my area here on leapery we have two major or not necessarily not all considered major but two distinguishable subsources the major one in gabalato gorge and the smaller one in canettodentro here in the southern area and uh you know what artifacts look like and the zillion artifacts to be analyzed anyway we can go and distinguish not only those two groups canettodentro and gabalato gorge but also the one other ancient source montadela guardia which did not produce pieces of significant size and therefore no artifacts have been found yet made of montadela guardia and i'm not showing on the map here the more historic eruptions but those can also be distinguished as well in case you didn't have good context for your artifacts and we can also distinguish the four ancient subgroups using laser laser ablation icpms and yes we can do it with the portable version of the brooker as well using those same few trace elements okay another example is with milos in greece uh where on the same island there are multiple uh subgroups the deminigaki and the stanikia or ademas subgroups again using just a few trace elements well let's look at some numbers uh now here or i'll talk about the numbers you don't have to read them all but one of the early studies i did was simply comparing what kind of variation do we get in the numbers that is the concentrations when we're calibrating them but the analysis was done with different microamps whether we used the filter or not and whether we used a vacuum or not well this depends on just say right again in the case of the vacuum that has no effect on the elements that i'm showing you here but it certainly has a big effect on other elements that are used in many cases for determining the composition of obsidian so just keep that in mind it really doesn't make any difference what the microamp amperage is and we have a couple of differences here in iron and some others that are bolded but that in itself is not really an issue but do keep in mind that even though this were standard pieces of obsidian and it was the same standard run again obsidian is not totally homogenous so putting it back and forth on top of the pxrf that accounts for some of the variation that we're seeing here as well okay so as i mentioned over time i've had a number of different versions of the bruce brucher tracer three series and two versions of the tracer five i'm not going to read all the details here but let's just say again that there are different fundamental aspects between these two general models in terms of the detector there's even a difference in the composition of the filter that is used in both of these cases and how when we're dealing with our ultimate numeric calibrated data where is that actually coming from well in the earlier brucher tracer three versions this was coming from brucher which came independently or whatever from analyses done in missouri by my glass cock and colleagues um but it was in it came with the same set of software for running the calibration they were not doing this on my specific model or that is on the specific physical one xrf unit that i purchased okay these were done like on the whole batch in general so that could be variation simply from the manufacturer and the and the pieces the detectors and so on in each of these instruments in the case of the version five though i have gone and analyzed the 40 geological samples from my glass cock directly myself and put that into the calibration program so it doesn't matter to me what kind of variation there is between mine and some of the other people who have these so keep that in mind here when we're dealing with numbers okay so i'm comparing here specifically for the gabalato gorge subsource on leapery with the various instrumentation here the three dash five three a dash sd the five i the five g and also laser blation and in a data as well and you can see in the case of the rubidium that we have lower values for the rubidium and the yttrium higher values for the zirconium with the tracer three sd for some reason the iron seems to be much higher with the five g anyway there's a lot of variation here and so it's really very important to keep this in mind when you want to compare your artifact analyses with your geological samples or that is you need to go and keep doing your geological samples for a direct comparison okay looking here on milos and the two different subsources there deminigaki and stanitia and again looking at the variation between the different instruments of my tracer three and five and also comparing to marina millich's publication where she's using an olympus inovacs and again you can see that for some elements in the green you have lower lesser values some that are higher in the red and so everybody has to just be very specific and careful with what they're doing okay here is millich's graph showing the comparison that she made as well between her pxrf and icp and pixie and regular xrf acknowledging that there are differences between different instruments as well as between different versions of the pxrf which is what i'm showing you here when you're only dealing with two sources that do not have similar values well we don't have to really worry about it it's because everything is still in the same broader group concentration areas but i'm showing you here the differences between again big difference between lipery and milos we don't have to worry about that but let's look here within the milos what's actually going on between those two different subsources you can see the variation that we have just within lipery gabalato and the same thing is true on the milos as well in particular the deminigaki group which i have here now in red that the different methods the different instruments that were used those offsets make them overlap quite a bit with the stanikia values so therefore you can't mix and match results that you're getting from one version of the pxrf with another you have to go and analyze geological samples and with the same instruments so when we analyze artifacts as well as geological samples from potential sources in our regions using the same xrf calibration is not an issue but changes over time in xrf models and detectors and keep in mind they do not last forever they do not last as cars do in many cases so just keep that in mind analysis of lower z elements and in the calibration programs require great care and direct numeric or graphical comparisons of mixed data always important to have enough geological samples also to show the range of elemental variation which may reflect multiple eruptions over time and space well most of us have our own geological set of samples from our study region beware of undocumented subsources in some cases as well as potential imports from sources not in our collections review carefully studies by non obsidian specialists publications and things i won't mention some that i've reviewed who have used pxrf but without geological samples for direct comparison thank you pxrf is portable precise rapid and less expensive but requires the use by somebody trained in x-ray analysis and data processing thank you rob questions for for dr tycott okay may i have a question one question so i want to know about your opinion that the data obtained from the pxrf analysis it's shareable for among the researcher and the robot laboratory i cannot so please please let me let me know your opinion or or opinion based on your data is it okay sure okay yeah so you can you understand why question okay i'm sorry i didn't understand what you just okay said okay shortly speaking so the data obtained from the pxrf instrument is shareable or shareable among researchers or it is difficult to it it it's still be difficult to among the researcher to share the data or pxrf analysis it's really no different than comparing results that you get on your ic pms machine and what my glass cock produces from mar or on your pxrf there's variation just based on the calibration software that's being used and and various things like that that you have to be careful of okay so my so basically so in my opinion the ic pms data and wdx data is so quantity data is quantity data very precise precise precise data so it's shareable and among researchers but so pxr is quite i think that to call it's quite too difficult to it depends on the machine itself the data so i i'm so asking about this i think that the pxrf is as quantitative as any of the other instruments the precision uh that we get on the analyses is just great it's the same issue with all instruments uh is simply being able to compare one with the other okay okay i can us on to thank you thank you i have a question uh lucas i can uh what about using the microprope and comparing px pxrf data with a microprope has anyone ever tried to do that uh yes i actually use the microprope for my dissertation work uh long long time ago uh and focusing of course on the major and minor elements that are detectable there but it's the same issue it and we can go and analyze many of those same elements with the pxrf using different settings and vacuum or helium flow but you just can't go and make a graph using results from both different methods without being able to analyze some of the same objects and show what kind of offsets there might be so that that highlights the importance of standards in some ways absolutely may segue into the next talk may ask one more question sure i don't know if there's time also to rub uh you know in our Ethiopian research you use the same instrument uh to look at uh the gamma obsidian but you never publish the details and uh you know we've asked you a few times for the details can you ever get us the details because we can't compare it because it's the same instrument uh we haven't published that yet uh because we haven't identified the actual source of locations and that is in progress uh and well it's been delayed being able to go back there uh again because of the COVID but we do have we have source information uh but you did publish it you published minor information not enough really to do any comparative work with not yet i see okay thank you rob yep our last paper of the day is an SEM based micro XRF and portable XRF spectrometry study of Mesoamerican obsidian tablets by Edward Vicenzi, Meredith Sharpe-Noyes, Maria Martinez, Michael Randall, and Thomas Lawn okay am i in the correct view here yes looks great okay great um um so we gratefully acknowledge the native peoples on whose ancestral lands we gather as well as the diverse and vibrant native communities who make their home here today in Maryland so in this talk i'm going to be describing some of the largest and finally worked obsidian artifacts uh described in the conference including results from portable XRF as well as microbeam XRF in the scanning electron microscope and i want to thank all my co-authors on the study especially Maria Martinez uh from the National Museum of the American Indian who introduced me to these special objects and Meredith Sharpe-Noyes, my former postdoc who took the lead on the measurements and did an excellent job during her fellowship at the Smithsonian so i want to begin by drawing a distinction between the assuredly pre-columbian round and polished objects that are found in various places in Mesoamerica and those in sharp distinction with the rectangular polished objects that are the subject of the top today that have never been excavated or otherwise found in context to our knowledge um and these objects are part of the NMAI collection here's the the building that you may be familiar with on the national mall in downtown Washington DC and they're curated at the on behalf of um indigenous communities at the cultural resources center in Suitman Maryland just outside of DC so for a variety of reasons that are spelled out in Maria Martinez's chapter in a forthcoming volume that's going to be published by the Smithsonian scholarly press these objects are thought to be produced by indigenous artisans on behalf of European invaders during the 16th century expansion so there are five black tablets the largest one measures 41 centimeters in width 32 centimeters orthogonally and about three centimeters thick that's pretty good thickness for all of them there's one mahogany tablet reddish brown brachia and they're they're very rare artifacts and there's a small number of museums and collections in the United States Corning Dunbarton Oaks University of Missouri and in in Paris at Musee de l'Homme and at the Louvre and the two specimens at the Louvre serve as canvases for paintings by Marilla and these have been analyzed by Pixie and Caligaro and others reported in 2005 that those both those tablets at the Louvre and the five unpainted tablets at Musee de l'Homme are associated with the Ucureo Zinnipaquaro source so in this segment of our study our goal is to simply identify the obsidian sources for the six Smithsonian tablets which is the largest single collection that we're aware of and it's rivaled only by Musee de l'Homme. So given the suspicion that these objects related to the Spanish in some way we focused our attention on the major sources for obsidian production in northern Mesoamerica in the late post-classic and we've modified a map here by Mike Glaskock's 2005 publication showing the boundary between the Taraskan or Parachipa Empire and that of the Aztec with the high quality sources as we've heard a lot about in the last two days from Ucureo and Pachuca. So many of the results I'll be reporting here today have recently been reported in a Journal of Archaeological Science reports. The majority of our reference specimens come from the National Museum of Natural History specifically from the Robert L. Smith Obsidian collection which was an accession not that long ago. We have a single specimen from collected by Jose Aguilera who was the co-founder and first president of the Geological Society of Mexico and even though he was a paleontologist he donated a specimen of Pachuca to the we also received generous donations of reference specimens from Mike Glaskock and Dan Hewlin. So here are the locations of our reference obsidians from two large volcanic centers in the trans-Mexican volcanic belt. In the east we have Los Azucres and to the west Sierra de Pachuca and so we have latitude longitude information for the majority of our references and a few of them are indicated by locality name. Okay so I'm going to talk about the instrumentation we used in this study relative to what I'm referring to as a typical portable XRF and I used the tracer 3 silicon drift version because that's the one we have in our laboratory. It's got about a 5 millimeter spot size. It comes into contact with the specimen and they're all rhodium sources all of these but has a has a power of about 1.2 watts and quantification through the calibration curve method that everyone seems to be using. In in our study the portable XRF is the Elio made originally designed by XG Labs and is now a broker product. It's capable of imaging 10 by 10 centimeters. It has a 1 millimeter spot. It's a non-contact measurement and it's a 4 watt source. We don't do quantification at the moment. We're not an obsidian shock. We analyze all kinds of materials so we don't have the standards to cover all kinds of compositional ranges. So we're using a crude net count ratio method for the portable XRF. The SEM based micro XRF is also a broker product called the X-Trace. It has a lateral spot size of between 30 and 35 microns and we operated at high vacuum or in low vacuum often in low vacuum because we're not interested in putting evaporative coating on electrically insulating samples like ceramics and obsidian and so forth. It's got a 30 watt power and we do quantification through fundamental parameters. So this is what the instrument looks like on the outside. It's an Etachi SEM with a large chamber. The X-ray detector is by broker and it's a large solid angle detector. Here's the micro XRF source that I referred to earlier the X-Trace. The optic is on the interior. We also collect multi spectral cathode luminescence in this instrument and we anticipate we will be making more discoveries as we link the emission of trace species in ceramics to XRF intensities. I've termed this instrument the analysis tandem the analytical dual beam microscope and that's why you see a bicycle. This is what it looks like on the inside of the chamber and here's a schematic that's co-location of the electron beam with the photon beam and then the common X-ray detector for both methods as well as an electron image showing the polycapillary optic which is the key to positioning it. You get a complete analysis of light to heavy elements and your analysis selection is informed by electron imaging or backscattered average atomic number imaging and so you can cope with heterogeneity at the sub millimeter length scale. So our lab is designed to handle all manner of museum objects from metals, minerals, paint cross-section, ceramics, historical and pre-historical manufactured objects you name it and that's the reason we're interested in this capability. So why bother measuring lozi elements in obsidian? We all use the mid to heavy atomic number elements for geochemical fingerprinting and I would say that since the big four oxides silicon silica, lumina, soda and potash make up 97, over 97 percent of obsidian it's useful to measure that but you can also predict whether a magmatic composition is alkaline or sub alkaline. This is something geologists have done for over a hundred years by computing normative mineralogy whether a magma will be quartz free or quartz bearing and that will determine its position on a total alkalized silica diagram. Here I'm not showing all the rock names at lower silica contents than in the rhyolite field but if we project that boundary you can see that for the specimens we're interested in in central Mexico just based on the major elements from the electron beam we can rule out the patruca source. The here the obsidian tablets are the filled triangles relative to a few other sources here and we'd like to compare the not just the results that we get but where is the information coming from by these two methods from the specimen. We'll start with the electron beam and so we can perform Monte Carlo simulations under the conditions of our analysis and we find that to 99.9% of the emitted x-rays there are all for the all the elements in major elements are coming from the top 2% of the specimen. With respect to XRF we can compute the information depth for a number of elements here I've done it for all the elements you see here in the periodic table and defined as 90% of fluorescence that's the cutoff I've selected so for sodium aluminum and silicon well we're within a factor of three of the electron beam so those should be almost directly comparable especially for a pre-homogenized material like obsidian we get to the potassium you know we're up the factor of seven greater in depth and then and when we get to iron at about 70 microns that's when things you really get either you can view it as an advantage to the XRF by getting a more representative bulk number or less sensitive to inhomogeneity so iron manganese around 70 and then as we get to higher energy x-rays rubidium strontium yttrium zirconium and niobium we are at many hundreds of microns depth of the information we're getting into the spectrum and so especially for something like zirconium we're at over 750 microns we're no longer in the realm of classical micro-analysis we're somewhere doing something like a sub-millionalysis so we use a yellowstone obsidian cliff's riotic glass for this project it's an excellent reference and the reason it's an excellent reference is that back in the 1970s it was analyzed by wet chemistry by one of my predecessors Eugene Jarosiewicz so he published his work in a freely available but totally obscure Smithsonian series and a few years after he published it he got permission to republish it with geostandards and geoanalytical research it's become a highly cited source for people especially in the electron probe business who depend on the Smithsonian standards for sort of ground truth with the wet chemistry so we use it as a secondary standard as to check the quantification from both methods as well as an internal reference we we just heard in the last talk about aging factors of instruments over many years we checked this reference during each analytical session for the project you know lasting over about a year or so here's the composition from that 1980 paper of Jarosiewicz and a spectrum from the micro XRF this is unfiltered so when we compare the measurements for the electron beam induced quantification which is based upon standards just as the electron micro probe community does and with the with the XRF measurements quantified by fundamental parameters here are the results the results are quite comparable for the yellowstone rhyolitic glass there are only two oxides that exceed three sigma indifference here and that's iron tough to see because the size of the symbols are large but this is largely due to heterogeneity in obsidian i'm using an example here from one of our tablets but you get the idea that there are iron oxides on a fine length scale and the micro XRF beam is a factor of 30 times smaller than the PXRF so we have the ability to encounter differing iron values by virtue of the the size of the probe so for silica these are the two values the XRF value the air bars here are one sigma and the electron beam value so they're just outside of three sigma but when we take a look at the accuracy of the analysis we're going to compare these results to the wet chemical values we we find that we're in good shape we're both the electron beam and the micro XRF results are within one and a half percent so that's absolutely we're very happy with that level of accuracy so here's an element ratio biplot for the XRF net count rates for all of the all six obsidian tablets and here we're plotting iron manganese to rubidium zirconium and the data for the tablets are plotted in the blue symbols and they're largely consistent or with the ucarea source there are two tablets that have values that overlap with the zinopequero but if you were to take the mean ratio of those two values they're they plot they plot clearly within the ucareo region they're the one specimen the mahogany tablet does not align with any of these source regions in this analysis and I just want to mention that because we didn't use a calibration curve we validated the net count ratio by using well established by measuring well established references that appear in the literature and so we compared our data to three other methods in AA XRF and LAIC PMS and we had good agreement with with all of those now we were unable to assign a source for the Smithsonian's mahogany tablet based on portable XRF but there's another mahogany tablet out there at the University of Missouri Museum of Art and Archaeology and it's been analyzed by portable XRF and it's also been linked to the ucareo source much like the obsidian canvases at the Louvre and the and also the tablets from Musee de l'Homme and so this is a Jacques Stella painting it's from 1630 and it depicts the decapitation of Saint Catherine of Alexandria and it's pretty vivid and instead of blood streaming there's a there's milk coming out of the body and it's a whole thing the artist makes really good use of the of the black parts of the obsidian I notice and and then the nanoscale reddish brown areas just serve as sort of a it's part of the gruesome angelic imagery so for the next phase of our project we did several things to address the unassigned data we added two additional Los Azufres reference specimens from the national rock and ore collection we employed the SEM based micro XRF and this time around in analyzing we used all five we use five elemental ratios the five that I show you here and on top of that used a canonical discriminant analysis and we confirmed that indeed in 2D and using two of the factors in CDA we could confirm that the black tablets are indeed from ucareo there's a few points lying outside of the 50 reliability in the two-dimensional plot but when we add a third factor then they plot clearly within the 50 reliability volume for ucareo and importantly the mahogany tablet data falls within the our locality called Haruaro which is just one of the geological sources collected by Robert L. Smith and was fortunately in our geological reference collection so finally final note here I just wanted to compare the elemental ratios that were calculated from fundamental parameters micro XRF with the portable XRF and so the solid black lines here are the one-to-one relationship you'd expect if you had perfect agreement between the two methods and you know for iron manganese and rubidium zirconium we get that perfect agreement and it's notable that all those elements are present at greater than 100 parts per million we don't get that result across the board for yttrium zirconium we do for when yttrium is present at high concentrations but when it's present at tens of ppm the trend is the ideal trend isn't found and so we sought to you know figure out which of the two methods was causing this excursion so what we did was we measured two NIST reference standard materials SRM 610 and SRM 612 that had yttrium and zirconium concentrations at roughly 450 and 440 ppm and what we found is that the micro XRF gave values that from difference from expected of less than 8% regardless of that concentration of this reference standard and we got good values for the portable XRF at the high concentration at hundreds of ppm but not for the low concentration SRM and so it's clear that the portable XRF net count method breaks down for our system the way we're using it at the tens of ppm level and it systematically underestimates the concentration so that's important for elements at least in the obsidian we were looking at for well then I'll just resummarize here the I wanted to close by saying that I think the co-located electron and micro XRF beam method it looks good for analyzing museum objects but it's going to shine for uh samples that have greater heterogeneity than an obsidian and we found that the five Smithsonian uh the black tablets were linked to Ucareo and that was true by pxrf and we confirmed it with the scm-based micro XRF and we discovered a new source for the Smithsonian mahogany tablet um just 20 kilometers northeast of Ucareo and uh in within the Los Zufres complex thank you very much thank you Edward are there uh questions we have about 10 minutes before uh our for our poster session goes up so we can spend this uh asking questions uh those of you who have a poster you're more than welcome to move in to those rooms and uh prepare your poster it's awful late in some parts of the world yes yes it is and we we uh we sympathize with that I confirm you so Nico just posted uh the link to the posters in the long pdf and a place that you can comment outside of the the formal conference here if you want to uh go ahead and make any comments and beauty posters uh using those links um otherwise you can move around the rooms and view the posters and talk with the authors directly which we certainly welcome but we we understand some of you it's very late and you may not have the energy for it we understand that one of our poster presenters will not be available but I think we're going to post the we're going to share the poster either myself or Kyle might might post it um just so people can read it and if there's any questions we can copy those questions down for the authors and then convey those um to them well I have enjoyed uh your conference so far thank you very much yeah when we next group of talks we've been very fortunate to have so many um stay on persistently throughout the shape that it's a dedicated community the high silica community