GeoSphere

Economic Geology

Cruisin’ for Deep Sea Vents

My friend John Jamieson, who is now a prof in the geology department at Memorial University in Newfoundland and Canada Research Chair in marine geology and is also a former GeoSphere guest poster is currently on a research cruise near Fiji. John researches deep sea vents, aka. black smokers/seafloor massive sulphide deposits that are exhaling super heated water at tectonic plate boundaries around the world. These vents are modern analogues of the conditions in which volcanogenic massive sulphide deposits form, which are major sources of iron, copper, lead and zinc around the world.

Watch the really cool video below to learn all about the cruise and why we care about black smokers and mapping the ocean floor.

While you’re at it, check out some of the other awesome videos from the Schmidt Institute for Ocean Science!

 

Photo of the Week #51

I’m getting back in the bog saddle. After a brief hiatus as I was adjusting to the life of a real, productive member of the PGS (post grad school) world I am good to go for blogging again. Enjoy the photo of the week!

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Sphalerite’s “Transformer” by Dmitry Tonkacheev, IGEM RAS, Moscow, Russian Federation

The text that follows is a technical description of the photo by the photographer, Dmitry Tonkacheev.

Presented intergrowths of the infinite number of dark-brown sphalerite’s and arborescent crystals of gold were synthesized using gas transport method at 850 centigrade degree during 20 days by Dmitry Chareev from the Institute of Experimental Mineralogy RAS in Chernogolovka city, Moscow Region while we were working on the project of Russian Scientific Fund in the Institute of Ore Geology, Petrology Mineralogy and Geochemistry RAS.
The main aim of this project was the determination of the maximum possible concentration and chemical state of some trace elements in the most abundant sulfides, synthesized using different techniques, including in ZnS. We obtained crystals of Fe-bearing sphalerite with simultaneous incorporation of Cd, Mn, In, Se and Au. The concentration of gold reaches 3,000 ppm (0.3 wt.%). This is amazing for natural sphalerite. The next goal was in-depth-study of the influence of the presence of Se, In, Fe, Mn on Au concentration and also lattice parameter in ZnS. In this connection in the furnace-charge of Fe-bearing sphalerite, different admixtures were added in different combinations or severally.

According to LA-ICP-MS data Fe did not encourage Au annexation (73±1 ppm). The bulk of Au wire “boards” on the dark-brown phase surface in the form of fascination crystals (usually arborescent). Some of them looks like a weapon from the “Transformers” arsenal or parts of his armor. Also bright diamond luster of this creature makes our “Knight” even more ultra-modern.

Militiamen’s profile was confirmed by twisted skeletal crystal on the transformer’s head. It looks like ostrich plumage or horn, which were the main attribute in the plate armor of ancient warriors and indicated about their noble birth. Truly, it is a king of all sulfides. The good news for us is the fact, that the coarsening of this bellicose subject is approximately 1-2 mm.

Guest Post: Dr. John W. Jamieson – Using seafloor mapping to find missing Malaysia Airlines flight MH 370

Guest Post: Dr. John W. Jamieson – Using seafloor mapping to find missing Malaysia Airlines flight MH 370

On March 8th, 2014, Malaysia Airlines flight MH370 disappeared while en route from Kuala Lumpur to Beijing.  Evidence from satellite tracking suggests that the aircraft may have crashed into the Indian Ocean several 1,000 kms west of Australia and this is where the search is now focused.  No debris or oil slick related to the aircraft has so far been found.  However, signals consistent with the “pings” of the flight data recorder were detected in two areas, several 100 kms apart from each other.  A search of the northernmost location, using an autonomous underwater vehicle (AUV) owned and operated by the United States Navy has so far turned up no sign of wreckage of the aircraft.  The intent of this blog post is to explain what instruments are being used to locate the wreckage, how they work, what are their limitations, and hopefully provide some clarity and perspective on the monumentally difficult task that lies ahead for the searchers.

Why is finding something on the seafloor so difficult?  The methods we use for mapping and surveying on dry land (e.g., aerial photographs, satellite imagery, laser and radar mapping) rely on the electromagnetic spectrum (e.g., radio frequencies, the visible spectrum and even infrared photography).  Electromagnetic waves attenuate quickly in seawater, however, and can only propagate over short distances (sunlight only penetrates the top 200 m of the ocean, known as the photic zone).  The result is is that we cannot see through water very well using electromagnetic waves, and the oceans effectively shield us from surveying the seafloor using traditional means used on land (and on other planets!).  So, to map the seafloor, alternative techniques are required.

On any world map that includes information on the ocean floor (e.g., Google EarthTM) you can see features such as ridges, seamounts, the continental shelves and submarine trenches.  These features were mapped using satellite altimetry, a technique in which orbiting satellites use radar to measure small spatial variations in sea level.  The uneven surface of the ocean results from variations in Earth’s gravitational field, which is stronger above positive features (e.g., a volcano) on the seafloor, due to the presence of more mass, relative to regular abyssal plain.  The increased gravitational pull causes seawater to preferentially flow to that location, resulting in an elevated ocean surface height directly above the volcano, or a dip in ocean surface height above a trench.  These sea surface variations can be translated into a map of topographic features on the seafloor (Fig. 1).  The resolution of the map, however, is only 1-3 km, which means features on the seafloor smaller than a few kilometers cannot be resolved (note that most media outlets covering the Malaysia Airlines search have been inaccurately reporting the resolution as 20 km).

Figure 1: Global seafloor topography map derived from satellite altimetry data.  Source: http://topex.ucsd.edu/WWW_html/mar_grav.html

Figure 1: Global seafloor topography map derived from satellite altimetry data. Source: http://topex.ucsd.edu/WWW_html/mar_grav.html

To generate maps of the seafloor with higher resolution, hydroacoustic or SONAR (Sound Navigation And Ranging) methods are used.  Unlike visible light or radio waves, sound waves are compression waves and can travel greater distances in water, and hydroacoustic techniques (e.g., the “pinging” of a flight data recorder) are the standard methods used for underwater mapping and communication.  Multibeam sonar is a mapping technique where a series of acoustic beams are emitted simultaneously downward to the seafloor in a fan-shaped geometry perpendicular to the direction of travel of a ship, submarine or other carrier platform.  The time taken for the acoustic signals to reflect off the seafloor back to a receiver is converted into a depth.  By using multiple beams, a swath underneath the ship that is roughly equally to 2 to 7 times the depth can be mapped, producing a 3-D topographic image of the seafloor beneath a vessel as it moves forward.  Modern multibeam systems can produce maps with a resolution of ~30 m (actual resolution is dependent on several parameters including depth and speed of the vessel).  It would take a fleet of 10 ships 15 to 45 years of continuous surveying to map the entire ocean floor at a resolution of ~40 m.  Although the resolution of multibeam mapping is significantly higher than the global satellite map, it is still inadequate to be of any use for finding a downed aircraft.

Higher resolution maps can be generated if the multibeam transmitter and receiver are closer to the seafloor.  This is achieved by mounting multibeam systems onto instruments towed deep beneath a ship by a cable, or, more recently, using AUVs such as the U.S. Navy’s Bluefin-21, which are effectively underwater drones that can be programmed to fly at prescribed altitudes above the seafloor.  From heights of 50-100 m above the seafloor, resolutions of less than 1 m can be achieved, which is good enough to find objects on the seafloor such as sunken ships, containers that have fallen off cargo ships, or aircraft wreckage (Fig. 2).

Figure 2: Example of a 2 m resolution image of the seafloor, derived from autonomous underwater vehicle (AUV) multi-beam SONAR data.  This image is from the Juan de Fuca Ridge, in the NE Pacific Ocean. The mound in the foreground has a diameter of ~75m and a height of 26 m.

Figure 2: Example of a 2 m resolution image of the seafloor, derived from autonomous underwater vehicle (AUV) multi-beam SONAR data. This image is from the Juan de Fuca Ridge, in the NE Pacific Ocean. The mound in the foreground has a diameter of ~75m and a height of 26 m.

A related hydroacoustic method that is commonly used (including for the Malaysia Airlines search) is side scan sonar.  Instead of emitting acoustic beams downwards, beams are emitted outward and downward at a wider angle, relative to multibeam sonar.  The intensity of the reflected signal is measured, producing an acoustic “image” of the seafloor.  The advantage of side scan sonar is that hard, solid objects stand out clearly, and, because the survey “swath” is wider than that for a multibeam survey, a larger area can be covered.

The initial search area for MH370 was a 314 km2 area where a pinging consistent with that of the Boeing 777’s black box was detected.  This area was surveyed with a U.S. Navy Bluefin-21 AUV using side-scan sonar, covering an area of ~40 km2 per day.  This initial survey turned up no evidence of the missing aircraft.  As the search radius expands, the area of seafloor to be covered increases exponentially.  For example, expanding the survey area to cover 60,000 km2 of seafloor, which is likely the next step, would take over two years with a single AUV.  However, this area will first be mapped using ship-based multibeam (a process that has already started), before choosing new targets to survey more thoroughly with an AUV.

In 2009, Air France flight AF447 crashed in the Atlantic Ocean en route from Rio de Janeiro to Paris. The wreckage of the aircraft, including the flight data recorder, was found two years later after searching nearly 17,000 km2 with 3 REMUS6000-type AUVs (one from GEOMAR in Kiel, Germany, and two from Woods Hole Oceanographic Institution, in Massachusetts, USA).  Figure 3 shows side scan reflections that were the first images of wreckage on the seafloor from the Air France flight.  Luckily, the wreckage came to rest in a flat, featureless area within a very mountainous region of seafloor near the Mid-Atlantic Ridge, so that the reflections seen in the image stood out easily.  Had the wreckage come to rest in an area such as that shown in Figure 2, the wreckage would not necessarily stand out so clearly.

Figure 3:  Side scan image of initial discovery of Air France 447.  The debris appears as bright reflections on an otherwise flat seafloor.  Source: http://www.bea.aero/docspa/2009/f-cp090601e3.en/pdf/f-cp090601e3.en.pdf

Figure 3: Side scan image of initial discovery of Air France 447. The debris appears as bright reflections on an otherwise flat seafloor. Source: http://www.bea.aero/docspa/2009/f-cp090601e3.en/pdf/f-cp090601e3.en.pdf

A major difference with the Air France search, compared to the Malaysia Airlines search, is that floating debris was discovered within a week of the crash, providing searchers a clear target from which to base their search.  The current search location in the Indian Ocean is constrained by satellite data, which defines a broad area spanning 1,000s of kms, and two separate reports of potential acoustic flight recorder pings, spaced 100 kms from each other.  With no physical sign of any wreckage, this search is indeed daunting and may take many years.

 

About the author:

John Jamieson is a research scientist at GEOMAR – Helmholtz Centre for Ocean Research, in Kiel, Germany.  John obtained his B.Sc. in geology from the University of Alberta in 2002, his M.Sc. in isotope geochemistry from the University of Maryland in 2005, and his Ph.D. in marine geology from the University of Ottawa in 2013.  John specializes in the study of mineral deposits that form at hydrothermal vents (or “black smokers”) on the seafloor, and the development of technology and methods for submarine exploration.  His research has led to participation on several research cruises and projects in the Pacific, Atlantic and Indian Oceans.  He has twice dived in the ALVIN submersible on the Juan de Fuca Ridge in the NW Pacific to depths of over 2,000 m.  His research currently focuses on the use of autonomous and remotely-operated vehicles and their mapping capabilities to locate and understand the geological controls on the formation of mineral deposits on mid-ocean ridges.  He works with governments, international organizations and industry on aspects related to seafloor mining.

The author, on board the French research vessel Pourquoi Pas?, with the GEOMAR REMUS6000-class AUV “Abyss” which was used in the search for the Air France flight AF447 wreckage.

The author, on board the French research vessel Pourquoi Pas?, with the GEOMAR REMUS6000-class AUV “Abyss” which was used in the search for the Air France flight AF447 wreckage.

#AESRC2014 Highlights

Well, AESRC is done for another year and with it my role as co-chair of the organizing committee! Thank goodness for that! Hopefully, I can finally get some actual thesis related work done in the coming months…and maybe get back to blogging a bit as well. However, as grateful as I am that AESRC is done, I have to say that it was a fantastic conference this year with a host of terrific talks from keynotes and grad students alike.

As I mentioned in my conference opening post AESRC is the only conference in Ontario, maybe Canada for all I know, that is organized by and for graduate students. The entire organizing committee is composed of graduate students and all of the talks, with the exception of keynotes, are given by graduate students. AESRC is meant to be a place where new and experienced grads alike can talk about their work in a less nerve-racking environment. We encourage in progress research or research that does not even have results yet. The idea is that every graduate student can feel comfortable, practice presenting to an educated audience and hopefully enjoy themselves and meet their colleagues from across the province.

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This AESRC was by far the most well attended in the past 10 years, with over 100 delegates attending from 8 different universities. The conference kicked off with the Icebreaker at a campus pub, where we all got meet each other or reconnect in many cases, while watching hockey and drinking beer. A nice relaxing end to the week and prelude to the science of the weekend. On a personal note, it is always worth attending the Icebreaker at every conference I have been to. More often than not there is free food and drink, but it is a great opportunity to meet new people, spot that keynote you want to talk with and introduce yourself. I try to make of point of meeting at least one new person at every Icebreaker I go to.

Saturday started with some great talk on Environmental Geoscience (my session) and Sedimentology and Petroleum Geology. We had two keynote speakers on Saturday: Paul Mackay from the Canadian Society of Petroleum Geologists and Dr. Jack Cornett from uOttawa. The video of Jack’s talk is below.

 

To summarize, in case you didn’t watch the entire video, Jack discusses the incredible range of radionuclides that are found naturally occurring on Earth and the vast range of geologic problems these nuclides can be applied to. He also talks about how we can use accelerator mass spectrometry to measure these radionuclides at incredibly low levels, which is how we are able to apply them to geologic questions. To illustrate this point Jack discussed the case study of chlorine-36 in the Cigar Lake uranium mine in Saskatchewan, Canada.

Saturday concluded with a fantastic dinner at the nearby National Arts Centre and another terrific keynote by Dr. Becky Rogala on the challenges of extracting bitumen from the oil sands and the importance of having an accurate understanding of the sedimentology to ensure maximum efficiency of SAGD recovery. There was also quite a bit of beer.

Sunday started nice and early with the Geophysics session as well as the Paleontology and Tectonics sessions as well. Our keynote for the geophysics session was Dr. Glenn Milne from uOttawa, who was an author on the most recent IPCC report and is an expert on sea level change.

 

We also had another great keynote from uOttawa in the tectonics session in Dr. Jon O’Neil. The video of his talk on the oldest rocks on Earth (4.4 billion years old) is coming soon! That pretty much wraps up AESRC2014! It was a great weekend, there was lots of great science and I am really glad its over. I likely won’t be around for next year’s AESRC at Queens University (fingers crossed), however, I am sure it will be great.

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Yours truly giving his talk on iodine-129 fallout from Fukushima. (Photo: Viktor Terlaky)

 

 

 

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