[John Mason]

ldavidcooke, on 20 May 2012 - 12:25, said:

Hey John,

Yes, you are correct, I had included both your rare zinc sulfite mineral in the beginning when I was discussing how it was created. (Usually in a highly humid or wet acidic environment at normal pressures.)

Then I expanded the discussion to include your evidence of Bleaching of the Iron Magnesium Dioxide Shist with the crystal filiments growing on the surface, (...looking a bit like the grain structure in an iron meteroite.) It was this sample that appeared to require the hot acidic CO2 rich environment under pressure.)

The main point I was trying to illicit was, it would appear your embedded statement relating to the original mineral being due to CO2 bearing rain did not seem to be very well supported. When in effect it likely had to of formed in either a hydrogen sulfide or sulfuric acid rich atmosphere.

Could you please help me in understanding why that statement was supported by the evidence, I simply do not see it...

Is this the image you are referring to Dave? ...."Iron Magnesium Dioxide Shist with the crystal filiments growing on the surface, (...looking a bit like the grain structure in an iron meteroite.)"



This is lower Silurian mudstone. In this area it is normally slate-grey. Here is an example, mined at depth and cut and polished, showing fault-breccia of grey mudstone cemented by quartz and zinc sulphide:




This is unoxidised: weathering had not penetrated to that depth. Now consider this:



You can immediately see that only local cores of grey remain in the mudstone fragment; the remainder has been bleached to buff shades. The white crystalline mineral is the lead carbonate, cerussite, which is accompanied by iron oxides. The primary ore found at depth at this mine was shattered mudstone, cemented by quartz, sphalerite (zinc sulphide) and galena (lead sulphide). The iron came from the sphalerite - it always contains a certain amount. The zinc itself simply ended up in the groundwater - it is very soluble, but the relatively insoluble lead leached from the galena combined readily with carbonic acid to form the carbonate.

In very acidic environments, these reactions do not occur the same way. The classic example in Wales is Parys Mountain on Anglesey, a massive sulphide deposit in which galena was common but pyrite was abundant: its weathering formed so much sulphuric acid that the oxidation assemblage consisted of iron oxides and large amounts of lead sulphate - Anglesite - named after the place at which it was first described in the 1830s. However, Parys Mountain is unusual in that respect and down here in Central Wales, pyrite is relatively localised and often only present in traces, so that in the oxidation assemblages carbonates dominate over sulphates - completely so in the deep-weathered stuff that is generally thought to have formed in the tropical conditions of the early Cenozoic, as in the cerussite-rich specimen illustrated above, which would not have formed in a very acidic, sulphuric acid-dominated geochemical environment.

Hope that makes sense! More interesting than discussing Heartland and their anti-science arm-waving in any case!

Cheers - John

[ldavidcooke]

Hey John,

That certainly helps in my understanding of your intent in the link. I was looking at the wrong line of evidence, so my thanks for having remedied that issue. As to your intended line of evidence, are you saying that mudstone is not an iron/magnesium rich silicate that has, under pressure and heat formed a solid amalgum? If so then I remain confused as to your line of evidence in support of CO2 rich rainwater being the source versus magmatic CO2 sources. Specifically, in relation to your description of secondary minerals is predicated in the donor elements you shared earlier, being Shales and by allusion, include dolomite dominated silicas suggesting the decomposition of smectite or chlorite and illite...

As to the sulfite deposits I thought these would be more indicative of sulfuric anarobic bacterium concentrations in mudstone as opposed to magmatic intrusion as well. Could you elaborate as to why you are certain that the supplied CO2 in the mudstone bleaching was from rainwater as opposed to magmatic intrusion. It would seem to make sense that you wouls see CO2 and Sulfites present in sedimentary deposits; yet, in magmatic intrusions it would seem that a silica-sulfide pairing was more common where as magnesium-CO2 was more common, at least in your region... Hence, the reason for my confusion... I am certain you can set me to rights quickly...

[John Mason]

Hi Dave,

The most compelling evidence is the following timeline:

~460 million years ago: main phase of Ordovician volcanism in Wales (we assume the volcanics underlie Central Wales but this has never been tested by drilling). From then on, marine clastic sediments were deposited over the area in what was known as the Welsh Basin.

~440 million years ago: Hirnantian glaciation and mass extinction disrupts sedimentation in Central Wales leaving clear evidence for a major fall then rise in sea levels.

~438 million years ago: onset of Silurian period; continued marine sedimentation (muds, sands, silts).

~400 million years ago: Welsh marine basin silted up; deformation of sediments due to closures of the Iapetus & Rheic Oceans.

~390 million years ago: first major phase of metalliferous mineralisation along mineralised fractures.

~360-330 million years ago: second major phase of metalliferous mineralisation along mineralised fractures.

~280-180 million years ago: third major phase of metalliferous mineralisationb along mineralised fractures.

~65-30 million years ago: major uplift of the western Eurasian Plate associated with ongoing Atlantic rifting. Tropical climate, cooling off towards the end. Deep tropical weathering of pre-exsting vein mineralisation leads to massive deposits of secondary carbonates, phosphates etc replacing the original metal sulphides in an assemblage clearly at or close to equilibrium; accompanying bleaching of host-rocks to an unknown depth downwards from surface.

~2.5 million years ago: onset of fluctuating glacial-interglacial cycles with major erosion of strata throughout Wales. Much of the deep-weathered bleached rock removed during the process.

~3500 years ago: first mining of sulphide ores at outcrop.

~Present day: only remnants of the deep-weathered vein mineralisation with the bleached rock remain here and there (all well-documented). A second, completely natural post-glacial weathering is recognised as present but is an immature, non-equilibrium assemblage with no wall-rock bleaching. A third, partially anthropogenic weathering is also recognised; this is due to miners removing sulphide-bearing rock from deep underground and piling it up in spoil-tips on the surface, where air and rain have over a matter of a few centuries led to oxidation assemblages containing all sorts of unusual sulphates, sulphate-carbonates and carbonates: the totally out-of-equilibrium so-called "post-mining" oxidation assemblage.

So everything I describe has taken place within a few hundred metres of the surface in an entirely clastic, sedimentary rock sequence with no other volcanic activity -extrusive or intrusive.

Cheers - John

[ldavidcooke]

Hey John,

Okay, first the presence of the various minerals leading to the secondary mineral formations are clearly wthin the rock itself, the initial resource of these minerals appears to have been magmatic and deposited by a combination of weathering and organic activity. The subsequent secondary mineral development appears to be related to the leaching of the donor minerals from the mined tailings. The leaching of these minerals as a minimum only require oxygen and water or high humidity to begin to create the secondary mineral examples. I see no requirement or support of carbonic precipitation leading to the formation of the secondary minerals. At best in a pre-320ppm CO2 atmosphere we see a high likelihood of sulfuric hydrogenation releasing the donor minerals resulting in the secondary mineral formation. Do I have this wrong or can you prove that the hydrogenation was the result of carbonic acid dissolved in rain water as opposed to nitric and sulfuric acid dissolved in rainwater?

[John Mason]

Hi Dave,

There is no evidence at all that magmatic fluids were involved in the primary (Devonian-Jurassic) Central Wales sulphide ore mineralisation: fluids generated by metamorphic dewatering and oilfield-type hypersaline brines from later adjacent sedimentary basins are better candidates, though work remains to be done on this. Sulphur isotope studies on sulphides from the unweathered parts of the veins and fluid inclusion studies of the various successive generations of quartz will likely resolve the question eventually here. The bottom line is that you do not need a magmatic source for the generation of mineralising fluids and there are several other demonstrated mechanisms in the stable. Magmatic fluids are but one potential type out of many.

The first two generations of secondary mineralisation occurred in situ (deep underground): one likely in the Cenozoic, when tropical temperatures and CO2 thought to be 1000ppm or more was the order of the day: only the third, "post mining" generation developed within the tailings.

You still need carbonate ions to form carbonate minerals in the secondary mineralisation process though! In veins where there were no pre-existing primary carbonate minerals and the wall-rocks are non-calcareous, the scope starts to get a bit narrow! You have to ask yourself from where has that carbon originated! Remember that low concentrations of carbonate ions in water (i.e. "hard water") can, over thousands of years, lead to some impressive things happening - think also of karstic landscapes and their amazing subterranean formations. Were sulphate ions involved, it'd be a poor show - as you can demonstrate for yourself, by dropping a chunk of limestone into a bucket of 1% sulphuric acid and examining it some 10 years later: this is the exact reason why static limestone pebble-beds do a poor job of deacidifying acid mine discharges. A rind of calcium sulphate forms around every single piece of limestone and as calcium sulphate is barely soluble in water it forms a protective shield, protecting the limestone from further useful interaction with the sulphuric acid. Carbonic acid is far more important - if it wasn't, the incredible mineral specimens from Tsumeb, Namibia, simply wouldn't have ever formed in the first place!

Cheers - John

[John Mason]

ps - it's also why mineral dealers clean quartz crystals with an unsightly thin coating of grubby calcite not with sulphuric but with dilute acetic, hydrochloric or nitric acid!

Cheers - John

[ldavidcooke]

Hey John,

Ah, now I see the difference in our references. In my lab tests we tried to replicate the environment,the combination of acids, (nitric, sulphuric and sodum chloride) appeared to dissolve the shales fairly effectively. ( Not dissimilar to the "fracting" mix being used here in the States to access more natural gas... ) That much of the mudstones you appeared to offer appeared to be of the expansive variety, it would suggest that the conditions within the rock itself were sufficent to ellcit the bleaching action. With the addition of limitations of sulfides in this type of shale eould seem to suggest that the leaching would have been a progressive action, except in the cases of the minerals such as your sulfuric, zinc depositions.

As long as the blend of available elements could support both the oxidation and reduction of the series, my pov can easily be supported. As opposed to the 380ppm of CO2 of today. with the gradual increase in atmospheric CO2 from 250ppm in 1750 being the main cause of the bleaching of the mudstones.. That most of the increase was is the last 50 years and yet most of the bleaching had to of occurred prior to the Industrial Revolution, there is little support for the addition of anthropogenic sources for the CO2 involved in the bleaching of iron magnesium dominated silicon/carbonate mudstone.

[John Mason]

Not sure what you are getting at here at all, Dave, because I said from the outset that this sort of deep-bleach in-situ weathering took place in the tropical climate of the early Cenozoic when CO2 levels were way higher and on top of that it was a long process that likely took millions of years. It also converted portions of large Cornish granite intrusions into china-clay sources and that does not occur overnight! I do not think I have said anything to the contrary anywhere. My data on the post-glacial in situ weathering support this and the post-mining stuff is unrelated to either of these other, non anthropogenic processes. To recap; there is no pervasive bleaching associated with the post-mining secondary mineral assemblages anywhere and what you see in terms of the very diverse sulphate/carbonate mineral assemblage is a completely non-equilibrium situation (a bit like today's climate if you like)! Furthermore, I have stated several times that the mudstones contain very little carbonate. Fe & Mg are present in the form of metamorphic chlorite-group minerals and these take some oxidation, believe you me, before they yield! Where you say, "As opposed to the 380ppm of CO2 of today. with the gradual increase in atmospheric CO2 from 250ppm in 1750 being the main cause of the bleaching of the mudstones." you are arguing with yourself because I have nowhere said this! Apart from anything else, such pervasive weathering tends to occur in subtropical to tropical temperatures, hence the very familiar term in geology, "tropical deep-weathering". It's why we have bauxite and nickel-laterite ores. One has to look back to the Palaeocene, Eocene and early Oligocene for such conditions in our latitudes.... the days of the Azolla Bloom and all that.

Cheers - John

[ldavidcooke]

John Mason, on 20 May 2012 - 17:12, said:

You still need carbonate ions to form carbonate minerals in the secondary mineralisation process though! In veins where there were no pre-existing primary carbonate minerals and the wall-rocks are non-calcareous, the scope starts to get a bit narrow! You have to ask yourself from where has that carbon originated! Remember that low concentrations of carbonate ions in water (i.e. "hard water") can, over thousands of years, lead to some impressive things happening - think also of karstic landscapes and their amazing subterranean formations. Were sulphate ions involved, it'd be a poor show - as you can demonstrate for yourself, by dropping a chunk of limestone into a bucket of 1% sulphuric acid and examining it some 10 years later: this is the exact reason why static limestone pebble-beds do a poor job of deacidifying acid mine discharges. A rind of calcium sulphate forms around every single piece of limestone and as calcium sulphate is barely soluble in water it forms a protective shield, protecting the limestone from further useful interaction with the sulphuric acid. Carbonic acid is far more important - if it wasn't, the incredible mineral specimens from Tsumeb, Namibia, simply wouldn't have ever formed in the first place!

Hey John,

As for where I am... in your excerpt above, you state that the chemistry does not support sulfite hydrogenation of mudstones or calcium carbonate bearing rock, yet we hsve clear erosion of lime based stone via this vehicle: CaCO 3 (s) + H 2 SO 4 (aq) CaSO 4 (aq) + CO 2 (g) + H 2 O (l) I have seen claims that the natural PH of unpolluted rain is 5.7. In my measures that was only found in the downwind measurments of coal burning power plants. In Florida I rarely found a PH lower then 7 and then rarely saw Carbonic acid in the samples. If the same rain was falling on the ocean as I am seeing on land then I do not see support for acidification via CO2. Going further as to the weathering we see in the cities such as Venice, Naples, Los Angles, New York, London or Berlin or Paris even the high levels of both CO and CO2 from transportation do not seem to be the primary weathering agent, it is sulfates. Going further yet, the weathering of glass panes of unbroken 100 year old windows is generally via two factors, one glass is not a solid; but, a very viscous liquid; the second is the nitric acid in the wv contributing to its loss of smoothness.

What I think the biggest misunderstanding we have is every chemical breakdown of mudstone I have ever seen suggests that it as is shale are a form of sedimentry limestone the main differences being the silica content, apparently you do not share in that definition? Hence, why it would seem we have been at loggerheads over nothing... As to the issue as we initially started off 2 pages ago, I am not seeing Carbonic acid today in most rain fall, hence, I am confused as to why the mine tailing were considered evidence of carbonic oxydation today?

[rosskesava]

Jeepers. This is so interesting. I've more than struggled over a lot of things posted and I've spent quite a time on the net looking stuff up but what an intriguing thread. Thanks.

This post has been edited by rosskesava: 21 May 2012 - 00:03

[John Mason]

Firstly Dave you need to stop worrying about the anthropogenically polluted rainfall that you analysed, and its unfortunate effects on architecture, seeing as I am discussing an individual case of weathering that took part in the geological past! The rock bleaching I described took place ca. 65-30 million years ago (I don't know how many times I have to repeat this point!): unless you have some Eocene rain to analyse it leaves us a bit stuck, but despite that I can state with full confidence that it was not tainted by the byproducts of the Internal Combustion Engine! But to continue with the dissolution of carbon dioxide in rainwater, here are just a couple out of very many bits of further reading that you can find:

Nasa on this, the so-called "slow carbon cycle" - most call it more accurately the "carbonate-silicate cycle": http://earthobservat...Cycle/page2.php

And why the process is so fundamentally important to life on Earth: http://burro.astr.cw...goldilocks.html

Mudstone may indeed contain major carbonate - hence the geological term "calcareous mudstone" - but it can also contain hardly any or none. The slaty mudstones of Wales are in fact pretty clean when it comes to carbonate - think about it - if they were carbonate-rich then there would be no Welsh roofing-slate industry! (mudstones from the Cambrian through to the Silurian have all been quarried for slate where the cleavage is sufficiently well-developed and structural disruption at a happy minimum) - as slate full of carbonate would weather to all sorts of horrible beige shades over a few decades instead of the neat, uniform greys that decorate the roofs everywhere in Wales. The carbonate-silicate cycle takes place over periods longer than the history of Mankind.

Cheers - John

[Conrad]

Hallo Dave

My feeling is that whenever natural processes are occurring that there are numerous primary and secondary causes contributing to the changes. However, it's also the case that one or two primary factors can strongly outweigh all of the secondary processes that are taking place. It's as somebody mentioned earlier, when somebody has been a chain smoker for 40 years and then gets lung cancer, the primary cause, based on present knowledge, is almost certainly the smoking that caused the illness. Based on present knowledge and probabilities it seems reasonable to deduce that. Yes, smoking so much was the cause, even though there is a very low probability that other secondary processes were really responsible.Likewise, somebody has a bad road accident. It turns out that they were drunk, and most people would conclude that that was the primary cause.

I acknowledge the points that you are making about heat flow etc, but the rising anthropomorphic increase in atmospheric CO2 does very much look like the factor that is principally responsible for the present global warming and as this global warming proceeds it will probably have dire effects, particularly in some areas of the globe more than others. Amongst the First Nations peoples in Canada there is a saying to the effect that whatever we do, we need to evaluate the consequences, not only to our own generation, but also to the generations that will follow us, even unto the 7th generation, as their saying goes.

I agree that there must be all kinds of secondary processes at work too, and these complicate the picture enormously. However, many, even most, of those best informed in this area of climate and atmospheric science are identifying the the continuing anthropomorphic release of CO2 , from combustion of fossil fuels, as being the principal driving factor behind the present ongoing global warming.

I feel particularly worked up about this because here in Canada we have a government that denies global warming and the possible destruction of atmospheric ozone etc. It even refuses to look at the evidence and it achieves this by closing down most of Canada's environmental monitoring agencies and firing the environmental scientists. When I look at the people and interests who either don't want to think about possible damage to the environment or those who deliberately fund global warming denial outfits, they always seem to have some strong connection to the oil and gas industries and related financial sectors and their only interest is in big profits now and forget about all of the rest.

Beyond this, yes we must continue the science so as to achieve a more and more complete picture of the complex processes that are taking place on our planet, our only home.

[ldavidcooke]

Hey John,

No, when you clarified that the bleaching was likely not from recent exposure we were good. That earlier pre-mineing (roughly 54mya prior) raiinfall likely provided the carbonates the issue was resolved. However, it still remains that there is insufficient recent history that provides sufficient support wrt CO2 as a primary drver of Warming. Given, that if you remove the CO2 that the Warming trend does not happen in models does little to suggest the mechanism of warming in light of alternative atmospheric heat flow.

[ldavidcooke]

Hey Conrad,

I believe it is a case of being an Ostrich, politically in Canada. They are loath to the consequences if it is true, just consider all of that coastline they would now have to patrol to protect their land rights. Add to that the one primary natural resource they can market other then agriculture. They apparently forget they have the prime ability as does Russia to be the worlds sources of natural plant fibers. With that in combination and their global hertiage of their population they have the opportunity to be world leaders. What seems funny is that for all that potential they are hiding their heads in the "sand"...

[ldavidcooke]

Hey All,

In truth, I am a poor example of the sceptical core as I am not formally trained. That this discussion has run as long as it has and became as technical as it did goes to suggest that even between friends misunderstanding occurs. If you get so frustrated that you feel your pov is either dismissed or disgarded as irrelavent you are likely to react as opposed to seek clarification. This is the conversation that needs to be taken up by professionals in my humble opinion.

With so many degrees of freedom of both the distribution of heat and carbon uptake it would appear we may be missing something. With the combination of organic uptake response and as John has patiently tried to suggest the dilution of CO2 in wv certainly supports the more rapid uptake, of the roughly 100-103Gt of carbon, in a world that emitts roughly 97-100Gt naturally, today!

Add in anthropogenic sources resulting in roughly 7.5Gt added carbon to the atmosphere, including the reduction in natural uptake on the order of 2-3Gt annually due to post-1650 environmental destruction (both natural and Man-made). That there is roughly 104-108Gt of carbon being emitted in a world with a 97-100Gt carbon uptake does play a part. (Though prior to 1650 there was roughly 4Mkm^2 more of organic uptake on land...) However, as the anthropogenic source levels of CO2 at 7.5Gt are only a recent imbalance (since @ 1950, >3Gt/yr), that does not support the change seen between 1700 and roughly the mid-20th century (<3Gt/yr, Avg @ 1.2Gt/yr). The point, this is but one of roughly 12 identified contributors both for and against global warming. (Re-edited in the vain attempt at improving my accuracy...)

So before I get pounded for being a denier please let us discuss the facts and the reality of the sources and sinks of the contributors rather then try to defend positions or povs. If after we agree to the science such that it can be observed that the facts lay somewhere between the extremes of current opinion, then its time for everyone to accept the truth rather then continue to go on and off subject in attempts to protect a pov that has so many degrees of freedom that in truth you could not hold them in a bucket for the holes... Reorienting on establishing direct cause and effect is going to be the only way forward, everything else is an ill wind...

(Oh and yes, models do play a part, they can show the direction of change and help suggest a value for the mid-range of change; however, they can not create a virtural world as there are simply too many variables to manage, (A bit like the computer required to answer the question "...and everything", wrt the Douglas Adams series..., (He was off by a mere 40 of the possible infinity of numbers,... Now, was that two (finite unique or divisive units), too (increasing or additional units) or to (the direction of a unit...?)) ...me thinks Hamlet may have been wiser then the mice...

[John Mason]

Y'know, Dave, I've never had you down as a denier. A bit contrarian at times (i.e. more skeptical in one direction than the other), maybe, and variably too, in all fairness, but in my books there's a huge difference! The people I'd class as deniers are in fact a small (but loud) minority - we have all come across them and those who engage in the climate wars tend to know them quite well, surprisingly, though it has to be said, not always on good terms! But we know who they are - and they know who we are! Very much like a game of chess, in other words. That is not how I'd tend to like debates to go here on UKww, because there are plenty of other UK-based fora in which such often pointless contests of words take place, and no lay reader has much to gain from the idea that in a tit-for-tat battle the first one to get ten tits is the Master of the Universe!

The Guardian's perhaps the classic example of such battles though of course people join in on there from all over the world. But getting involved with Skeptical Science was a good choice for me: if I suggest a topic I then typically need to read 20-odd papers, perhaps querying the authors if I need clarification, then submitting the post to internal review, in which any of my cock-ups WRT the science get found and illuminated. The idiom is always to accurately and fairly report where the science is at at the time. It has certainly increased my reading volume by two orders of magnitude - and has anybody got a filing-cabinet they don't want

I cannot fully appreciate PDFs on-screen - I need good old hard copy, a highlight-pen and a biro to scrawl notes/potential questions. So the bulging folders build up...

But delving ever deeper into the literature as a member of SkS has to beat playing pointless word-tennis with some Tea-Partier or other! And the nice thing is that I can focus on the science a bit more than the goddam politics!

Cheers - John

[ldavidcooke]

Hey John,

I try to keep an open mind... As for a battle of words, concur whole-heartedly. My choice has nearly always been lets look at the empirical evidence of the processes being described, that support the theory being shared. I have usually figured if the goes-inters and the goes-outers can be explained by one and only one process, we have a winner!

When I see multiple processes and a lack of empirical evidence supporting the prescribed processes, I become concerned. Its when those around me go rushing headlong off the bridge..., I stop and look about trying to find what suggested a gentle landing...

Certainly it can be as simple as I missed something everyone else has got; however, most times I find that movement in a certain direction becomes similar to what happens in a mob. So I get sticky feet, until I get a logical, supported answer... (Hence, Wishy-Washy is not quite correct...)

As always if science is under discussion I will be "Johnny on the Spot", at least for the moment... The differences in opinion are my obligation, the science is the nectar. Hopefully, here we can find a medium where both can be shared and growth in both directions can occur.