Natural olivine beaches

[Andrew Lockley]

Hi

The proposal for olivine weathering on beaches seems to pass a common sense test.

However, there's been a lack of detailed discussion about the occurrence and function of natural olivine beaches, as far as I'm aware.

There are a lot of beaches in the world. Olivine is pretty common. How much of a sink is natural beach chemical and mechanical weathering of olivine?

It should be easy to find at least one location where there's massive quantities of olivine sand, and take detailed measurements on the carbon sink.

I know there's at least one such beach in the literature, but I can't recall discussions of others, nor detailed quantitative research on erosion and sequestration rates at this site

Can someone enlighten me as to why this has seemingly been overlooked for detailed study?

A

[Greg Rau]

Agree that the silicate mineral sand idea needs testing. I'd first start in the lab with a flask of freshly ground olivine in chemically well characterized, sterile seawater. I would then put this on a shaker table in the dark and let the sand and water gently slosh back and forth for a few days and then measure the SW alkalinity and DIC again.  this would give you and idea of the efficacy and kinetics under ideal conditions. Measuring this in a beach setting would be trickier, but possible. My guess is that there are synergies with sediment respiration/microbes that hasten silicate weathering. Add in some fresh sediment to the above flask and see what happens.

Greg

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From: Andrew Lockley <andrew....@gmail.com>
To: geoengineering <geoengi...@googlegroups.com>
Sent: Tuesday, September 30, 2014 11:28 AM
Subject: [geo] Natural olivine beaches

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[Parminder Singh]

Hi,

Schuilling carried out experiments where modest surf action was imitated by having olivine grains rotate slowly along the bottom of an Erlenmeyer, the water turned an opaque white after a few days of rotation, the pH of the solution had gone up, and many of the slivers had already turned into neoformed grains of brucite, a mineral known to carbonate fast.

As for beaches you can find them in Hawaii, Turkey, Galapagos Is. just a few to mention.

Regards,

Parminder

[Greg Rau]

Thanks. Indeed,  Schuiling and de Boer* did a flask study but only measured olivine effects on tap water pH.  Seawater was not used, DIC and alkalinity were not measured, nor were controls done. As far as I know the other relevant papers on marine silicate CDR simply model dissolution rates using various assumptions. While I may be missing something, it would seem that discussion of marine silicate CDR potential would benefit from some carefully controlled and measured lab and field experiments using well characterized seawater and silicate mineral(s).

Greg

* http://www.earth-syst-dynam-discuss.net/2/551/2011/esdd-2-551-2011-print.pdf

"Three Erlenmeyer flasks were filled with 250 ml tap water and 30 g olivine from Norway

with a grain size of 0.71–1.4 mm and three others with 250 ml tap water and 30 g olivine 20 grit (2–5 mm) from Turkey. A third experiment was carried out with a 50/50 mixture of both. The Erlenmeyer flasks were put on a table top rotary shaker, so that the grains kept rotating along the bottom. The Erlenmeyers were open to the air, permitting CO2 exchange. In all cases the tap water had an initial pH of 8.22, and the olivine grains

had been washed to remove any attached dust.

554

3 Results

Grains of both sizes became visibly rounded (Fig. 1). The abraded fine material caused the water in the bottles with fine-grained olivine to be cloudy. In the bottles with coarse- grained olivine the water was a milky white, opaque suspension (Fig. 2). Already after

5 6 h the pH had risen to 8.82 in one bottle with coarse-grained olivine. After 1, 4 and 10 days the pH in one of each of the two series of bottles was measured. In a bot- tle with fine-grained olivine the pH had risen to 8.91 after 24h, and in a bottle with coarse grains to 9.02 (Table 1). This implies that the coarse grains had produced more slivers than the finer grains, likely due to their greater mass and consequently heavier

10 mutual impacts. In this experiment the olivine reacted with a limited, fixed amount of water. Thus, logically the accumulation of reaction products slowed down and even- tually stopped the reaction (Table 1), contrary to shallow marine settings where water refreshment is continuous and the tiny slivers, together with the dissolved magnesium and silica, are carried away.

15 Figure 3 shows the grain size distribution of the material that was scraped oð the grains in the test with 50/50 coarse and fine grains. The amount of scraped oð material was 9 g (30 %), considerably more than the amounts in the single grain size experi- ments which were slightly over 1 g in the separate fine and coarse fractions. The pH in the 50/50 mixture rose to 9.42 in 12 days. About 50wt% of the abraded particles

20 is 5 μm or less (Figs. 3 and 4). Such fine grains of olivine weather fast, as is evident from the rapid rise of pH during the experiments. The rate of solution may have been further increased by the deformation that grains undergo when they are strained. The phenomenon of enhanced dissolution of fine particles by repeated particle impact and rubbing is well known in the field of mineral processing, where it is called mechanical

25 activation (Tromans and Meech, 2001)."

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From: Parminder Singh <psin...@gmail.com>
To: geoengi...@googlegroups.com
Cc: andrew....@gmail.com; gh...@sbcglobal.net
Sent: Tuesday, September 30, 2014 10:59 PM
Subject: Re: [geo] Natural olivine beaches

[markc...@podenergy.org]

Greg,

Might a paleoclimate researcher know or find a technique for dating the rate of carbon sink based on sediment cores from olivene beaches?  Perhaps relating the sink rate to past air/ocean CO2 concentrations?

Mark

Mark E. Capron, PE
Ventura, California
www.PODenergy.org

[Francesc Montserrat]

Thanks for bringing this up Andrew... Greg, to follow up on your points made: I presented some preliminary results at the Climate Engineering Conference in Berlin last August. Basically, everything you´ve mentioned we´ve done at NIOZ in the past two years, including proper lab tests with filtered seawater, and different mixtures of artificial seawater, and controls (of course), where we measured DIC, alkalinity, pH, dissolved silicate and dissolved metals. Also, we´ve fed olivine to common bioturbating coastal macrofauna (lugworms) to see what their potentially enhancing effect might be on olivine dissolution in coastal settings and as we speak/write, students are applying small layers of forsteritic olivine sand in mesocosm setups (1 m2 basins) with natural coastal sediment and running seawater. Results of the shaking experiments and lugworm experiments are nice, and more importantly, consistent and I expect to come out with the first shaking bottle lab experiments in a manuscript in november or december. Depending on the results of the current experiment, the rest wil then follow. 

Yes, Papakolea Beach on South Point, Big Island Hawaií is one very nice place where an olivine/basalt mix of grains forms a green beach in a relatively closed embayment. Depending on the wind, the bay is very well accessible, and would serve perfectly as a natural analogue, or at least tell us something on the accumulation of dissolution products on the marine ecosystem.

   

Cheers,

Francesc

PS I´m away on holiday at the moment, and will only check email irregularly

-----
vriendelijke groeten / kind regards,

Dr. Francesc Montserrat
Netherlands Institute for Sea Research

Department of Ecosystem Studies
PO Box 140
4400 AC Yerseke
The Netherlands

Phone: +31 (0)113 577 472
Mobile: +31 (0)6 2481 5595

http://www.nioz.nl/

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From: geoengi...@googlegroups.com <geoengi...@googlegroups.com> on behalf of Parminder Singh <psin...@gmail.com>
Sent: 01 October 2014 07:59

To: geoengi...@googlegroups.com
Cc: andrew....@gmail.com; gh...@sbcglobal.net

Subject: Re: [geo] Natural olivine beaches

[Russell Seitz]

Perhaps more to the point,temperate zone  serpentinization  and tropical weathering  of olivine rich rocks like basalts and dunites is proceeding constantly over large inland areas, and whereever  such rocks are eroded , comminution in rivers and streams gives rise to olivine particles even smaller than those you have discussed .

[Andrew Lockley]

Do any useful materials tend to occur alongside olivine? If so, using tax incentives to ensure that open cast mining takes place in olivine-rich areas would potentially help greatly. Coarse-ground mine tailings dumped in areas prone to erosion would eventually end up weathering pretty fast.

This could be a very simple way of getting some pretty large volumes of CO2 out of the air.

A

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[Parminder Singh]

It came to my notice in the tropics and sub-tropics where ultramafic rocks exist on some islands, weathered materials like serpentine are washed into rivers etc leading them into mangrove swamps. One in particular is New Caledonia.
Pls see link http://newcaledoniaplants.com/plant-catalog/mangrove-plants/

The mangroves are so healthy possibly the result of these nutrients and other chemicals present in the waters. However I also note there is extensive mining on the island and mangroves threatened by toxic chemicals. Another problem is the presence of chrysotile asbestos in the ultramafic rocks is not good for humans. I am interested to study the reaction of mangroves to olivine and other forms of surpentine like lizardite. Much of the coasts of countries in the tropics and sub-tropics can be further protected by natural means if these plants can be grown near coastlines to protect them against erosion, sea-level rises and tsunamis. In addition we may see further CO2 uptake by these forests by reducing the acidification in the surrounding waters.

Parminder Singh

Malaysia

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[Schuiling, R.D. (Olaf)]

Once you do the mining and crushing, you might recover chromite, even if the grade is too low as a chromite ore. Once the mining and crushing is already paid for by the olivine, it may become possible to recover low chromite contents from the crushed olivine. Another possibility is magnesite that is present as veins in some olivine massifs. Olaf Schuiling