Matt Herod

Geology Photo of the Week #34

Matt Herod June 3, 2013

My apologies for the slight blogging hiatus over the last little while. I have been preparing for a conference and then attending and so I had to put blogging on the back seat for a few weeks to prepare properly. However, the conference is done, my talk is given so now I can get back to blogging…at least until the next one…which starts on Tuesday (tomorrow). Luckily, I get to just watch at this one and don’t have to go through the effort of actually preparing to say anything. This conference is a very focused and small event that specifically concerns the geoscience of the proposed low-level radioactive waste storage facility in the Bruce Peninsula.

The photo for this week is known simply as the “The Candelabra”. It is one of the best if not the best specimen of blue-cap tourmaline in existence.

Blue cap elbaite at the Smisthonian Museum in Washington D.C. (Photo: Matt Herod)

Of course, the Canadian Museum of Nature has a pretty nice one also:

Blue cap at the Canadian Museum of Nature (Photo: Matt Herod)

Both of these unbelievable specimens come from the same location, which is the Tourmaline Queen Mine in Pala, California. The mine is still a producing gem mine to this day and if you would like to find out about its colourful history click the link above (pun intended). The geology of the mine is no less fascinating than the crystals it produces. It is located in a pegmatite, which is a class of igneous rock that can often be a source of large crystals and/or unusual mineralogy. Pegamatites are a type of intrusive igneous rock that can form from a melt that contains a high percentage of volatiles, such as water, which lowers the viscosity of the melt and allows for the formation of large crystals compared to those formed from a higher viscosity melt. Some crystals can be several metres in length. Furthermore, pegmatites can often contain a high concentration of incompatible elements such as lithium, tungsten and boron. These elements, among others, don’t normally form minerals easily, and are known as lithophiles or incompatible elements. When they are forced to crystallize in a pegmatite that has branched off a large batholith the result can often be unusual minerals such as toumaline or spodumene.

The reason that the tourmalines from the Tourmaline Queen have the “blue cap” is because of their chemistry. In the case of the blue caps there is a sudden shift from manganese rich to iron rich, which causes the sudden change in colour.

Thanks for reading,

Matt

p.s. This post represents something of a milestone for this blog as it is my 50th post since this blog began in October 2012. I am looking forward to another 50!

Tools of the Trade

Matt Herod May 14, 2013

It is already May!! Crazy. Everyone in the department is incredibly busy right now trying to get all of those things on their winter to-do list checked off before it is time to head out to the field once again and re-fill the to-do list for next winter with sample prep, analysis and some interpretation. It is also time to start thinking of preparing for the field. Some of you hard rock folk might think it is a bit early to start prepping since all you need is a hammer, some canvas bags, and….what else do you need? However, for the geochemist it is time to start organizing our MESS aka. Mobile Experimental Sampling Supplies. Yes, I did just make that up, but I think you get my drift.

For real though, there are numerous essential items that every aqueous geochemist/hydrogeologist needs to bring or at least consider bringing into the field and since these type of items often get back ordered around this time of year it pays to start thinking about it early. Otherwise, one could find oneself lacking anything from their new pH meter to bottle caps the day before one leaves. Not that either of these things has ever happened to me…..mistakes are part of learning, right?

Uh-oh! Notice the chipped edges and the crack. These are not good things and this guy ended up in the garbage. (Photo: Ian Clark)

Key parameters that must be measured in the field are pH, Eh/ORP, temperature, alkalinity and conductivity. There are many other parameters that may be measured in the field, but those five are the most essential as they are subject to change once the sample is collected and therefore any long delay in measuring these can compromise the integrity of the data.

The most essential piece of field equipment is probably the pH meter. It is the one completely indispensable measurement that must be taken sitting beside the sampling site. The other four, are essential as well, but if I could only do one, I’d do pH. The reason I am touting pH measurements so highly is simply because in geochemistry so much depends on pH: speciation/redox, dissolved gases, dissolved aqueous complexes, mineral mobility, alkalinity, etc. The list goes on and on. The reason it is so essential to measure pH in the field is because it can often change once the sample is collected due to temperature changes or CO2 degassing. One key thing that must be done before any pH measurements are taken is calibration. It is very important to calibrate the probe at least once each day in order to make sure of getting the most accurate performance.

Our current pH meter and probe: the YSI Pro Plus meter and combination pH/ORP electrode. So far so good, although it has yet to face the rigours of the field. Note the geochemical nature of the background. (Photo: Matt Herod)

The other measurement that goes hand in hand with pH is Eh/ORP (oxidation reduction potential). ORP is a measurement of the oxidation/reduction potential of the water. It measures the electron activity of the water which has a major influence on the specification and solubility of elements and minerals in the water. Eh/ORP measurements are given in volts and often go hand in hand with pH. In fact, many pH probes also measure ORP at the same time so both of these crucial parameters are recorded simultaneously.

Conductivity is another measurement that uses its own probe. Conductivity of a water sample is a measurement of salinity of the water. It is basically a measurement of the ions in solution. Conductivity is not a particularly quantitative measurement in that the numbers that it gives are not super accurate, however, it does provide a very good idea of the relative salinity of different waters. For example a cold freshwater spring might have a very low conductivity whereas a lake after a rainstorm might be very high, due to increased sediment influx from runoff.

A nicer pic of our conductivity meter than I could take. (Source)

Alkalinity is another key field parameter that measures the acid buffering potential of the water sample, which directly corresponds to the concentration of HCO3 in the water, except in rare circumstances, where other species provide the acid buffering capabilities. Alkalinity titrations are a bit of a process, and do take a bit of time, but it is essential to do them ASAP as the loss of CO2 from the water can change the alkalinity. Alkalinity is measured by taking the initial pH and then slowly adding acid using a digital titrator and taking the pH along the way. The keys to this are to know the volume of water being titrated, the volume of acid added and the pH after each acid addition. With those basic numbers the amount of HCO3 can be calculated. The key equipment needed for alkalinity titrations are the pH meter, filtering apparatus, the digital titrator and a flask. By the way, helpful tip: don’t store the acid with the titrator, or make sure the acid is well sealed or else this can happen….and those babies aren’t cheap.

This is what happens when the acid is put away with the titrator. (Photo: Matt Herod)

Other field parameters that can be measured depending on the type of work being done are dissolved oxygen (DO), which is a common parameter in groundwater sampling and ion selective electrode measurements (ISE). ISE’s can provide a guide to the concentrations of certain ions in the field such as Cl, NH4, F, etc. Ion selective electrodes are great, but they often have a higher limit of detection that the mass spec back in the lab. They are very useful for groundwater sampling or contaminated water sites, where the concentration of dissolved ions is high.

So that is the basics on the different things we have to measure in the field, but there is a lot more stuff that has to come out in order to make these measurements possible and take the samples…and it is really, really easy to overlook something. For example, you can have a great pH meter and probes and be ready to go, but it won’t be much use if you forget one of the calibration standards back in the lab a few thousand kilometers away.

The key pieces of this list (if it were mine) include a lot of random, but very necessary, items such as: filter papers, syringes, filter cartridges, DIC/DOC septa, pH standards, AA and AAA batteries, digital titrator tips, acid, de-ionized water for rinsing, instruction manuals, rock hammer, ziploc bags, GPS and many other little things.

The list of stuff that must be brought to the field is dependent on the type of sampling that you are trying to do. The most important part of planning to the go the field is to pick the parameters that you would like to sample for and tailor your gear list, sample collection methods and field measurements to make sure the samples are of the highest quality. Follow these words of wisdom: “Determine what you are analyzing for in advance and collect your samples according to the proper protocols for each analyte! An analysis can be only as good as the sample that goes into the ICP-MS” – Nimal De Silva (ICP-MS legend). Basically, what this means is that in order to ensure good results the samples must be collected properly, in the proper containers and stored the right way until they are analyzed. Failing to do so could compromise the quality of the results.

Thanks for reading and I would love to hear if I missed anything or if anyone else has field methods/gear that they use for other types of sampling. Please comment!

Wishing everyone a productive field season.

Matt

p.s. I forgot to mention the most important piece of field equipment in the geologists arsenal:

Geology Photo of the Week #33

Matt Herod May 13, 2013

The photo of the week this week is of a very special place in Canada. Yes, predictably, it is the Yukon. However, this part of the Yukon is unique. It is a special region known as Beringia, which extends into Alaska and Siberia and it is the only part of Canada that was not covered by kilometers of ice during the last glaciation. Beringia is a special place because it is believed that that first human inhabitants of North America made their way across the exposed land bridge form Siberia into the Yukon and spread west and south. Geologically, Berinia is interesting as it is full of Pleistocene mammal fossils like mammoths, short faced bears, giant beavers and other giant mammals. It is also strange because of the degree of weathering and erosion that the rocks have undergone is like nowhere else in Canada. Piles of talus may not seem like a big deal to people from other parts of the world, but for a Canadian geologist this is a somewhat unusual sight as most of our mountains had a good scraping 20,000 years ago and we just don’t see this level of weathering anywhere else in the country.

Cheers,

Matt

Geology Photo of the Week #32 – Name that squid!

Matt Herod May 6, 2013

This edition of the photo of the week highlights another piece from my personal collection.

Cephalopod – Matt Herod Collection (Photo: Matt Herod)

This is a cephalopod. More specifically it is a member of the Order Endocerida and the Family Endoceratidae. This creature, which hopefully you can see was pretty large (golf tee for scale) was the largest of the Ordovician cephalopods found in Ontario and this is a particularly fine/large example mainly because it tapers all the way to the apex at the end, which is a very rare find, and because of its large size (~7ocm). Cepahlopods, such as Endoceras, were the top predators of the Ordovician ocean that once covered most of southern Ontario and they grew up to several metres long. The cephalopods of the past resembled modern squids of today. Indeed, they were the progenitors of the Cretaceous ammonites and the squid and octopi of today’s oceans. If you enjoy calamari, thank a cephalopod!

(Photo: Matt Herod)

This zoomed in look at the cephalopod shows the siphuncle and the suture lines, which divide the inner chambers. The siphuncle was an inner tube that ran the length of the cephalopod and allowed it to control its buoyancy. The fact that the siphucle and sutures are clearly preserved is a great feature of this cephalopod, however, there is more….

When I was extracting this fellow from the giant boulder he was in I was unfortunate enough to break him in several pieces, which I have now super-glued together. But why, you may ask, did I not super-glue him completely together? The answer is pictured below.

(Photo: Matt Herod)

One of the points at which he broke contained this tiny little trilobite, which I am pretty sure is a Bumastus, based on the shape of its pygidium (tail). I decided not to rejoin the parts together so that we could still see this little dude that made this find a 2 for 1 deal. The obvious question is what is this little guy doing in a cephalopod? Was he eaten? Was he seeking shelter? Was he eating the already dead cephalopod? I have no idea, and it is pretty hard to prove one way or the other now. Please weigh in and let me know how you think he got in there!

Also, the other great fossil in my collection, the two trilobites that were featured in the Photo of the Week #25 and are named “Bert and Ernie”. We have a similar pair here, but they lack the awesome name. Please suggest your favourite names for this odd couple.

Cheers,

Matt