Hi Paul, very interesting work. I too am interested in the idea of proving the human delivery of these stones, rather than glacial delivery (unlikely).

As has already been said, it would be strikingly difficult to be able determine the difference between glacial delivery and human delivery. The irrefutable way that this could be accomplished however, is that if the location of origin of all 7 rock types were shown to be incompatible with the delivery to the site of the glaciers. For example, if all rock types were shown to be sourced from geogmorphologically unassociated or unconnected locations (below Stonehenge's elevation, or across different catchments, would show that the glaciers could not have brought them up against the flow of the topography). Following this line of logic, it would be possible to say that knowing all seven localities of the rock types that humans must have delivered most of the rocks from the quarry to their current location, depending on the strength of the geochemical evidence.

It is rather straightforward to determine the source outcrop for the 7 rock types you listed. This could be first done by comparing rare Earth element (REE) concentration patterns of each rock type sample to similar rock types in the surrounding region. Comparing REE concentrations in each rock type will narrow down the source areas, and can be quantified using REE capable bulk chemical analysis with ICP-MS or LA-ICP-MS. Some REE in question could be Rb/Sr, Sm/Nd, U/Th, etc.

Another method to cross confirm the source of each rock type would be through the geochronology of samples. Radiometric dating of Igneous rocks to determine their source is more straightforward than dating sedimentary or metamorphic rocks. Dating the time that an igneous body crystallized is done by first isolating individual mineral grains from a thin section analysis. This will allow you to see what minerals are first available for radiometric dating. You would then have to separate the minerals (density separation after chemical dissolution) to date your rock sample. Thermal ionization mass spectrometry (TIMS) can be used to do U/Th or U/Th-He dating of zircons in your igneous rocks for example. Dating these minerals in your sedimentary rocks too can prove useful if you have detrital age populations for the regional sedimentary rocks for comparison as well.

All of these kinds of analyses can be taken out in various University labs around the world who have expertise in this field. After you provide such samples to the geochemists, and relative context, they can do most of the work for you. You will want to find minerals such as zircon or garnet (and many more) to be used for dating the cooling. Age determination is a vague science in itself, because these kinds of measurements have a wide range of uncertainty and area always to be taken with a grain of salt if not combined with additional data to piece it together.

There is one more catch with providing the provincial analysis of these rocks, and that is the size and uniformity of the original rock quarry. Maybe the rock came from a uniform massive batholith that is widespread in a region over 100 km wide, then you would have no exact way of knowing where it was quarried other than knowing the formation your rock is from. Of course the rock could be from a much narrower source, but that is a different, possibly more difficult task to solve if the quarry is minuscule at the surface and the formation has yet to be mapped.

I can provide good references for the geochemical tests (ICPMS, TIMS, etc) and geochronology that may be of interest to you if needed. Message me for more questions and I'd love to provide more insight.

Cheers!

Dear Mr. Marketing.

I am not familiar with the rock type of this monument. Therefore it would be helpful  to get a more detailed information on the lithology in question. Apart from this I would suggest a "double blow" to use chemical data and the mineral association to constrain the provenance area. I myself did a lot of archeo-metallurgical studies encompassing the origin of the feed to the ancient kiln. The wide range of minerals determined using SEM-EDX, EMPA, XRD etc. provides a more efficient tool than a chemistry-only investigation. You can also start with non-destructive methods in the field using portable  IR scanners. Even if it is restricted only to IR sensitive mineral species you can cover a wide region and get a first glimpse of the various lithologies in the target area and possible source rock areas as well.

Kind regards

H.G.Dill

intersted

The Rock Types of Stonehenge that I am interested in Sourcing are the smaller Bluestones.

These consist of a number of Rock Types :

* Spotted Dolerite ( Plagioclase Feldspar spots )

* Unspotted Dolerite

* Rhyolite

* Volcanic Ash

* Ignimbrite

* Sandstone

* Schist ( Although some sources are calling this Micaceous Sandstone ).

Hope this helps.

I am batting on the team that believes that Man not Ice moved these three Ton Monoliths the 140 miles from Pembrokeshire to Salisbury Plain.

Would be the "Spotted Blue Dolerite".

Thanks

There is but my concern is "How 'Close' is 'Close' ?

The quarry from  where the bluestone at Stonehenge originates was found  in 2015  by Mike Parker Pearson. https://www.cambridge.org/core/journals/antiquity/article/craig-rhos-y-felin-a-welsh-bluestone-megalith-quarry-for-stonehenge/D1E66A287D494205D22881CBF1F6DDE8

Some earlier studies have pointed out provenance of dolerite/ rhyolite based on chemistry, microbiology.

It is difficult to pint out one single source unless you are very sure of both mineralogy and chemical composition of these rocks as well as the probable source rocks.

New techniques like QEMSCAN both data at the same time. If possible you can approach for such study which is non destrcutive as well.

Can you say what the best equipment to use is ?

It looks like there has been considerable work on this. Are you looking at a particular lithology? For example that would use portable XRF see: Thorpe, R.S., Williams-Thorpe, et al. 1991,. The geological sources and transport of the bluestones of Stonehenge, Wiltshire, UK. In Proceedings of the Prehistoric Society (Vol. 57, No. 2, pp. 103-157). Cambridge University Press.

Hi John

Thanks for answering. I'm following up on the earlier work. The Thorpe results I feel don't correlate particularly well with later work - Parker Pearson and his pocket-geologists.

I suppose it comes down to how close is close ?

The best elements for determining origin are radioisotope elements that its good for igneous rocks. You can also use rare earth elements.

Thanks Farhad.

Are some Rare Earths and some Isotopic elements better than others ?Perhaps the rarer elements will give a higher degree of confidence in the result.

Hello,

for ceramics sourcing raw materials, I used LA ICP MS to analyses some type of mineral inclusions and compare the chemical signature of these minerals with the signatue of the same minerals in the supposed mother rocks. I think that you can perform the same method for your samples.

Thanks Benjamin

Do you find there are any good statistics that allow you to put a probability on the likely source ? We have also got a Medieval Kilns project on the go in the Memorial Hall ( Newport, Pembrokeshire ) and there are quite a lot of disagreement between the Archaeologists on sourcing.

Hi Paul, very interesting work. I too am interested in the idea of proving the human delivery of these stones, rather than glacial delivery (unlikely).

As has already been said, it would be strikingly difficult to be able determine the difference between glacial delivery and human delivery. The irrefutable way that this could be accomplished however, is that if the location of origin of all 7 rock types were shown to be incompatible with the delivery to the site of the glaciers. For example, if all rock types were shown to be sourced from geogmorphologically unassociated or unconnected locations (below Stonehenge's elevation, or across different catchments, would show that the glaciers could not have brought them up against the flow of the topography). Following this line of logic, it would be possible to say that knowing all seven localities of the rock types that humans must have delivered most of the rocks from the quarry to their current location, depending on the strength of the geochemical evidence.

It is rather straightforward to determine the source outcrop for the 7 rock types you listed. This could be first done by comparing rare Earth element (REE) concentration patterns of each rock type sample to similar rock types in the surrounding region. Comparing REE concentrations in each rock type will narrow down the source areas, and can be quantified using REE capable bulk chemical analysis with ICP-MS or LA-ICP-MS. Some REE in question could be Rb/Sr, Sm/Nd, U/Th, etc.

Another method to cross confirm the source of each rock type would be through the geochronology of samples. Radiometric dating of Igneous rocks to determine their source is more straightforward than dating sedimentary or metamorphic rocks. Dating the time that an igneous body crystallized is done by first isolating individual mineral grains from a thin section analysis. This will allow you to see what minerals are first available for radiometric dating. You would then have to separate the minerals (density separation after chemical dissolution) to date your rock sample. Thermal ionization mass spectrometry (TIMS) can be used to do U/Th or U/Th-He dating of zircons in your igneous rocks for example. Dating these minerals in your sedimentary rocks too can prove useful if you have detrital age populations for the regional sedimentary rocks for comparison as well.

All of these kinds of analyses can be taken out in various University labs around the world who have expertise in this field. After you provide such samples to the geochemists, and relative context, they can do most of the work for you. You will want to find minerals such as zircon or garnet (and many more) to be used for dating the cooling. Age determination is a vague science in itself, because these kinds of measurements have a wide range of uncertainty and area always to be taken with a grain of salt if not combined with additional data to piece it together.

There is one more catch with providing the provincial analysis of these rocks, and that is the size and uniformity of the original rock quarry. Maybe the rock came from a uniform massive batholith that is widespread in a region over 100 km wide, then you would have no exact way of knowing where it was quarried other than knowing the formation your rock is from. Of course the rock could be from a much narrower source, but that is a different, possibly more difficult task to solve if the quarry is minuscule at the surface and the formation has yet to be mapped.

I can provide good references for the geochemical tests (ICPMS, TIMS, etc) and geochronology that may be of interest to you if needed. Message me for more questions and I'd love to provide more insight.

Cheers!

Hi Cole

Thanks for such a comprehensive answer. It sounds like more than a one-man task. I will keep you up-to-date on the progress of the Project. Think I am pretty close to discovering the source outcrop of the Volcanic Ash.

At the moment I'm trying to think through the initial thoughts of Neolithic Men in this project. Did somebody just say - lets take 80 odd Multi-Ton Megaliths on a 140 Mile holiday to Salisbury Plain one day?

Cheers

Paul

Geologist

North Pembrokeshire