The US has become the largest producer of oil and gas in the world because of the technology created in 1997 to produce oil shales via fracking. The talk by Marc Defant was given on May 17, 2021 to the Rotary Club. Defant’s message is that we need to be good stewards of the environment but not destroy our economy by quickly converting to clean energy.

I enjoyed another talk with Chris Irons on the Quoth the Raven podcast. We talked about the New York Post article and the duplicity of the Press and even got into some discussions about global warming, volcanoes, and existential threats.

Quoth the Raven link to the podcast. You can also download it from the link.

In my debate with Graham Hancock on the Joe Rogan Experience podcast (beginning at 2:03:43) and a critique of Graham’s book I wrote for Skeptic magazine along with further details on my website, I found myself dealing with the veracity of the Younger Dryas Impact Hypothesis (YDIH). I was skeptical of the hypothesis but stated the following in my Skeptic paper:

“…the debate proceeds in the proper scientific manner (i.e., by publishing results in peer-reviewed scientific journals). As Malcolm LeCompte, one of the comet researchers, pointed out in our debate… there are four indicators at the YD boundary that may be due to an extraterrestrial origin: nanodiamonds, magnetic sphericals, melt glass, and the platinum group metals.”

My major problem with the YDIH was the claim that the megafauna and Clovis culture went extinct as a result of the proposed comet strike. I noted in the Skeptic paper “Scientists have also been a bit incredulous that a comet strike could wipe out all the megafauna as far south as Patagonia, while leaving mammoths alive and well on St. Paul Island, Alaska until 3,700 years ago.”

I recently had some correspondence with Graham, and he suggested I read a recent book by James Lawrence Powell entitled Deadly Voyager: The Ancient Comet Strike that Changed Earth and Human History (2020). It is a superb book and has absolutely convinced me there were comet airbursts at the Younger Dryas. And the airbursts probably killed the megafauna which in turn, caused the Clovis culture to cease existence (partly by diminishing human numbers but also because there was no need to have Clovis spearheads that could kill nonexistent megafauna). I have not been keeping up with the debate since 2017, and so I was thrilled to see the new evidence that has come to light and the lack of scientific merit in the studies that attempted to dismiss the hypothesis.

I recommend the book — it is a fascinating read. The evidence is overwhelming and nicely collected and summarized by Powell. It is clear that the Pt signature shows up precisely where it is expected about 12,900 years ago in all the sites, and high-pressure nanodiamonds, melt glass, carbon from forest fires, magnetic sphericals, etc. show up precisely where they are expected over 4 continents. I also have to admit the YDIH is an extremely good argument that the megafauna died out from the comet airbursts and the Clovis culture was impacted. The forest fires alone wreaked havoc across the continents. The mammoth existing on St. Paul Island seems to be a minor incidental when compared to the other evidence. And a crater is not required – no wonder they don’t find shocked minerals — the airbursts would have kept earth materials out of the equation.

Finally, the Hiawatha crater that has recently been discovered below the Greenland Ice sheet may or may not be related to the YDIH. But it is not needed to explain the evidence.

Of course, all of this does not change my views of Graham’s two most recent books. I enjoyed reading his latest entitled America Before (2019) because it is well written and his knowledge of archaeology is superb*. But as I say in the Skeptic article: “To be clear, the [YDIH] debate is not over lost civilizations.” So although I consider Graham a friend, I disagree with his lost civilizations scenario with all the respect he deserves.”

* When I say that Graham’s understanding of archaeology is superb, I am talking about his knowledge about what other archaeologists have done at sites. I do not mean to imply that his research is superb. I disagree with the results of his “research” and so do archaeologists – link.

Link to Skeptic magazine article

My article entitled Conjuring Up a Lost Civilization: An Analysis of the Claims Made by Graham Hancock in Magicians of the Gods[1] was published in Skeptic magazine on Sept. 14, 2017   It has been an interesting road to the final publication.  Michael Shermer (editor of Skeptic magazine) asked me to join him on the Joe Rogan Experience podcast #961 and Youtube video cast (JRE) in a debate with Graham Hancock and geologist Randal Carlson which I have linked (Hancock invited planetary scientist Malcolm LeCompte).  The three and half hour podcast has had millions of views on various platforms including 1.4 million on Youtube.  According to Shermer in an accompanying article in Skeptic, during the week of the show it was downloaded 120 million times “putting him [Rogan] on par with the biggest talk show hosts on television” and making our podcast one of the most popular in the world (I became involved in the debate at 2:04:45).

Rogan is normally a neutral host based on what I have seen of some of his earlier shows, but that was certainly not the case in this podcast.  The early sections of the show pitted Rogan, Hancock, and Carlson against Shermer as he tried to defend our skepticism toward Hancock’s book.   I will let Shermer’s words in his article stand without further comment.

Shermer writes a monthly article for Scientific American.  By sheer coincidence, his article on Hancock’s book was posted the day of the podcast.   Shermer muses in his Skeptic article about how Hancock wrote him after the podcast vociferously objecting  to “the rubbishing of his life’s work” in the Scientific American article.  Shermer explains that he is truly sorry that Hancock felt personally attacked and that was not his intention.  I was also the brunt of Hancock’s outrage over my skepticism about the contentions he makes in his book.  I posted an early version of the article here on my blog — I use my blog primarily as a way to show students how science and logic can be used to address controversial claims in various fields (e.g., GMOs, fracking, global warming, etc.).  The original article had many editorial changes but due to copyright precedence by Skeptic I only showed the original article submitted.  Prior to the JRE podcast, Hancock found the original article and became visibly angry during the podcast over what I had written (I do not wish to inflame him further by asserting that he was angry but Hancock used the word angry on Facebook after the podcast: “Judging from the Youtube comments to my recent appearance on the JRE I have been transformed into a hate figure because I expressed anger at the article posted online in January 2017 by Marc Defant”).  Like Shermer, I had no intention of personally attacking Hancock and was apologetic that he misunderstood my intentions when I first came on the podcast.  I cannot speak for Shermer but I think skeptics, myself included, are somewhat befuddled by the acceptance of non-scientific claims by many in the general population.  Hancock’s book  is an international bestseller and will continue to influence uncritical minds for generations.  People like Carl Sagan and James Randi started taking people to task in the 1970s for making outrageous and unfounded claims (e.g., Erich von Däniken and his alien visitation scenario) which eventually led to the formation of skeptic societies.  The goal is not to personally attack anyone but to demonstrate how faulty some of the more fantastic claims are.  I deeply support Hancock’s right to his opinion, but as scientists, I believe we have a duty to dispute fantasy that masquerades as scientific inquiry — for example, von Däniken’s books.

I need to identify some misunderstanding which Hancock has taken full advantage of, and I have been unable to comment about while I waited for the publication of my paper by Skeptic magazine.   After the podcast, Shermer asked me to remove my blog post on Hancock because, obviously, he wanted people to read the article in Skeptic.  I readily agreed to remove the article.  In a weird twist, Hancock and many of the viewers of the podcast insisted that this demonstrated that I had made claims in the blog that were incorrect.  That is not true.  As I stated in the podcast, I stand by the claims I made about his book both on the podcast and in the Skeptic paper.  In fact, I elaborated on what I said on the JRE in my Skeptic article and have added additional comments below that were not in the magazine article.  My original revised paper after the JRE was so long Skeptic had to cut some of my arguments to avoid a book-size article.   Consequently, I elaborate below on several of the topics not addressed in the Skeptic paper particularly because I never got a chance to express them in detail on the JRE.

 

The gravity of the situation

In Hancock’s discussion of the  Incan archaeological site Sacsayhuaman in Peru, he recounts how he was guided around the ruins by some mystic named Jesus Gamarra, who thinks that the finely crafted rocks at the site were not done by the Incas but by ancient people in a time when “gravity was lower” so the huge blocks could be moved more easily. I would not pay much attention to this unscientific remark other than to make note of Hancock’s astonishing comment about this “theory”: “The lowered gravity is linked in his mind [Gamarra] with the notion that the earth once made much closer orbits around the sun—an orbit of 225 days and an orbit of 260 days—before settling in to its present 365 day path. He could be right [my emphasis]; new science suggests that the orbits of the planets are not fixed and stable.” Hancock does not seem to realize that the gravitational pull on an object at the surface of the earth has practically nothing to do with the period of the orbit of the earth around the sun. How could Gamarra be right?  As Newton discovered in the 1600s, the gravitational pull between two objects, say the earth and a large rock, is directly related to the mass of the earth and the rock and the inverse of the square of their distance.

In fairness to Hancock I quote his remarks from the JRE: “He [referencing me] just presents me as buying what Jesus Gamara says.  If that’s the standard that you are going to have in Skeptic magazine you have a serious problem…I do say he [Gamarra] may be right, but I don’t say he is right.  I say this is not my interest.”  I attempted to explain that my focus was not on whether he agreed with Gamarra but on his statement that rocks might not be as heavy in the past because the “period of the orbit of the earth around the sun” changed.  He completely deflected away from my contention that changing the orbit around the sun has virtually nothing to do with how heavy rocks might be on earth.  I believe the misunderstanding of the basic laws of gravity is important – it makes him suspect on other grandiose contentions he makes concerning science.

Sacsayhuamán,_Cusco,_Perú,_2015-07-31,_DD_27The superb construction at Sacsayhuaman in Peru.

I have attempted to see if the statement could be read any differently (he skated around the issue in the debate), but I fail to understand how. Hancock states that Gamara may be correct in his contention that the rocks were lighter in the past because the orbit of the earth around the sun may have been 225 days (or 260 days). Instead of pointing out that a 225-day orbit around the sun in 900 AD when Sacsayhuaman was built seems silly (calendars have been around for more than 2000 years continuously demonstrating 365-day years), Hancock states “he may be right”.  He may be right that the earth in 900 AD was where the orbit of Venus is now?  But even if the earth in some mystical way was on a 225-day orbit a quick back of the envelop calculation using Newton’s equation of gravity demonstrates that the weight of a rock on earth will not be significantly impacted by the gravitational pull of the sun.

 

Moai and Easter Island

During the JRE, Shermer brought up the moai, the megaliths on Easter Island.  More than 900 moai were sculpted between 1250 and 1500 AD, hauled to their present locations, and erected upright.  One of them weighs over 82 tons.  Many of the moai remain in the main quarry on the island – Rano Raraku. Hancock never addressed Shermer’s point that huge magaliths can be made by people with limited technological skills.  I later reemphasized to Hancock that the hunter gatherers on Easter Island had no problems constructing megaliths larger than those at Glöbekli Tepe with stone tools.  Why should we call upon the involvement of advanced civilizations?  But Hancock again deflected, surprised that I would suggest that hunter gatherers lived on Easter Island: “What’s there to hunt and gather on a tiny island – have you been to Easter Island? I have, six times, and you can walk across it in three hours.  What’s there to hunt and gather on that?”

AhuTongarikiMoai of Easter Island

Apparently what he did not realize is that when Polynesians (the Rapa Nui people) first arrived on Easter Island probably around 300 AD, the island was a lush tropical paradise.  Jared Diamond, in his book Collapse[2], proposed that the Rapa Nui hunter gatherers committed ecocide which led to the destruction of the island’s lush ecosystem and forced the Rapa Nui founders’ descendents to depend on a meager agriculture.  The increased population of the Rapa Nui on Easter Island according to Diamond led to deforestation and overkill of native species, decimating the ecosystem.  The point that Shermer and I were trying to emphasize is that hunter gatherers can make sophisticated megaliths without the help of “Magicians”.  Hancock postulates in his book that Magicians of the Gods were needed also at Easter Island.  No explanation has ever been given as to how these Magicians got to Easter Island or why but Hancock believes they were required to help the native population to construct the moai.

But alas, the argument is not specifically about the hunter gatherers on Easter Island.  It is about whether it takes an “advanced civilization” to create large hand-carved megaliths – hand carved with stone tools I might add!.  Not a single professional archaeologist working on Easter Island has ever suggested a requisite advanced civilization.   They all agree they were quarried locally with stone tools by the indigenous population[3].

 

The End of the World

In Hancock’s 1995 book Fingerprints of the Gods[4], Hancock suggests that the end of the world is approaching, all neatly summarized in a section at the end of his book entitled “The End of the World”. He particularly references December 23, 2012 (from the Mayan calendar) as a likely date for the end, but in Magicians he adroitly does not dwell on why these doomsday scenarios never came to be. He does an about face and tells us he never meant for these dates to be taken literally and sheepishly states in Magicians: “it is important to be clear that in signaling the decades around 2012 as the end of a great cycle, the Maya were not speaking of the end of the world, as such, but rather of the end of an age.”  I am reminded of Ghostbusters II when Peter Venkman (Bill Murray) is interviewing Milt Angland (Kevin Dunn) on his new book entitled The End of the World for Venkman’s television show World of Psychics.  When Angland announces that the end of the world will be on New Year’s Eve at midnight, Venkman astutely notes that choosing a date so close to the present is not wise for book sales.  After Angland gives a painful “fugue state” response as to why the date must be correct Venkman quips: “For your sake, I hope you’re right.”  My advice to Hancock — pick an end of the world date that does not occur in your lifetime!

In response to this early version of the article, Hancock posted the following comment in his defense on his Facebook page: “Are my views not allowed to evolve, then, or react to new information? Must I never stray from the line I took in a 1995 book? If I did so would that be ‘scientific’?”  Of course his views are allowed to change.  But predicting the end of the world from the Mayan calendar is not scientific.  One might expect that being wrong on such an important event as the end of the world would chasten him.  Not so!  After the end of the world did not occur in 2012, he continued down the same road making this comment in Magicians:

“It is possible, indeed highly probable, that we are not done with the comet that changed the face of the earth between 10,800 BC and 9600 BC.  To be quite clear,… some suspect that ‘the return of the Phoenix’ will take place in our own time — indeed by or before the year 2040 — and there is danger that one of the objects in its debris stream may be as much as 30 kilometers (18.6 miles) in diameter.  A collision with such a large cometary fragment would, at the very least, mean the end of civilization as we know it, and perhaps even the end of all human life on this planet.  Its consequences would be orders of magnitude more devastating than the Younger Dryas impacts 12,800 years ago that left us as a species with amnesia, obliged to begin again like children with no memory of what went before.”

First Hancock assumes that a comet struck about 13,000 years ago – still a hotly debated research topic.  Second, as I discuss in my Skeptic article, he contends that the precession of the earth tells him that we will be struck by another large comet some time before 2040.  As I explained in Skeptic, precession has nothing to do with cyclical comet collisions.  Predicting the end of the world seems to fascinate his audience but where is the science?  It is complete speculation equivalent to soothsaying (I suspect that this will irritate Hancock but I want those that are willing to listen to know that predicting the end of the world through speculation has nothing to do with science – nothing personal here).

 

[1] Hancock, G., 2015. Magicians of the God: The Forgotten Wisdom of Earth’s Lost Civilization: St. Martin’s Press.

[2] Diamond, J., 2005, Collapse: How Societies Choose to Fail or Suceed: Viking Press, 592p.

[3] See for example Van Tilbug, J., 1994, Easter Island: Archaeology, Ecology and Culture, Smithsonion Institution Press, 191p.

[4] Hancock, G., 1995. Fingerprints of the Gods: The Evidence of Earth’s Lost Civilization: Three Rivers Press.

 

A few lucky souls have stumbled on diamonds in glacial debris around the Great Lakes and further north into Canada for centuries.  Geologists have known that the sources of those diamonds represented a vast wealth of hidden treasure somewhere in the frozen tundra of northern Canada, but it was not until the late 1980s that a couple of cowboy geologists, Chuck Fipke and Stewart Blusson, painstakingly ferreted their way back to the source. But I am getting way ahead of the story.

Diamonds are brought to the surface from deep within the upper mantle via unusual igneous rocks called kimberlites (and sometimes lamproites).   I recognize I run the risk of losing my readers by delving into the nature of kimberlites, but to a geologist like myself kimberlites are crazy types of rocks.  Typical magmas (and lavas) like basalt form by partial melting of the mantle.  Kimberlites, on the other hand, are geologically unique because although they form from partial melting of the mantle, the melting is significant enough for these rocks to resemble compositionally (not precisely) the mantle itself.  They are referred to as ultramafic rocks as compared with basalts which are mafic (mafic means rich in magnesium and iron – two of the most abundant elements in the mantle).

Diamonds actually don’t form in kimberlites.  Think of kimberlites as a conveyor belt bringing diamonds that form under high temperatures and pressures (from about 125 to 175 kilometers1) to the surface relatively fast, before they can reequilibrate (breakdown) into other compounds like graphite or carbon dioxide.  Diamonds are not forever.  Many an exploration program has had its hopes dashed with the discovery of kimberlite full of octahedral or other cubic forms of graphite — degraded diamonds2.

Exploration for diamonds can be excruciatingly frustrating.  There are 6,400 known kimberlite pipes worldwide but only 30 or so have become viable mines — that’s about 0.5% chance that a discovered kimberlite will turn into a producing mine.  It’s true, diamondniferous kimberlites are hard to find, but you don’t need many diamonds to make a mine.  High-grade diamond kimberlites only contain a few carats per ton of rock.  That’s enough to make any geologist rich beyond her dreams.  Kimberlites form at greater than 200 kilometer depths (200 to 600 km) and are enriched in volatiles (e.g., carbon dioxide and water) that make the magmas not only buoyant but explosive.  They literally “blow” through the upper mantle and crust in perhaps a matter of hours (rates postulated are about 14 km/hr) forming carrot-shaped pipes called diatremes (see the diagram below).  The faster the better for diamond preservation.  But they also have to pick diamonds up along the way or incorporate them as the magma forms.  Kimberlites can contain as much as 25 to 50 percent rock within their magma acting as an elevator to the surface for mantle material helping geologists understand the mantle3.

VolcanicPipeAsbestos Wikipedia

After half a century or more of serious diamond exploration. we have learned that diamond-bearing kimberlites form below the cratons.  The cratons are the ancient regions of continents containing rocks greater than 2 billion years old.  There is still great debate about how the cratons formed, but every continent is rooted in these ancient environs.   If you are looking for diamonds, go to the cratons.  Before the 1980s, diamond kimberlite mines had been developed on every craton of all the continents except Antarctica and North America.  Diamonds come from two major sources: mantle rock (e.g., peridotite) and eclogite (metamorphosed basalt).  Diamond formation in peridotites occurred primarily in the Archean centered on a time about 3 to 3.3 billion years ago but some dates are as young as 1.9 billion years ago.  Eclogite diamonds tend to be younger from 1 to 2.9 billion years ago.

Where does the carbon come from to form diamonds?  No one knows for sure, but most researchers think that the carbon along with sediments and volatiles were subducted through plate tectonics (the ecologites brought up by kimberlites are likely ancient subducted ocean floor)4.  I am interested, through my own research, on how the cratons formed and when subduction began.  Many geologists pooh-pooh the idea that subduction could have begun so early in earth history so it is satisfying to see how diamond research supports the early existence of plate tectonics and subduction.  My colleagues and I have contended for years that the cratons are the result of ancient subduction.

Imagine Chuck Fipke in the 1980s looking out over the vast expanses of northern Canada contemplating all the diamonds he believed had to be out there in the craton hidden below tons of glacial deposits.  Those damnable glacial deposits were the reason no one had discovered pipes in Canada5.  The map below shows the furthest extent of the glaciers 17,000 years ago and the site of the diamond pipes eventually discovered.  Fipke also had to contend with De Beers, the giant cartel that controlled the world’s diamond markets. They were actively exploring with their practically unlimited resources.  I worked for De Beers as a consulting geologist for a time in the mid 1990s in Russia, and I can assure you, they are a force to be reckoned with.

diamond countryBase map from Wikipeida

By the mid 1980s, geologists had discovered that the mantle material brought up by kimberlites could aid them in their exploration thanks to a geochemist named John J. Gurney at the University of Capetown.  Diamonds form in equilibrium at specific temperatures and pressures with other minerals more abundant than diamonds.  Gurney, funded by Superior Oil, analyzed extensive mineral assemblages from kimberlites with and without diamonds and found that there are chemical signatures in the minerals that show up when diamonds are present.   One of the more famous diagrams is that of the chromium and calcium concentrations in garnets from the mineral assemblages.  Garnets fall into two groups on the diagram called G10 and G9 and virtually all garnets that occur with diamonds fall within the G10 field shown below.  As mentioned before, diamonds can reequilibrate in kimberlites and become graphite or evaporate away as carbon dioxide.  The diagram shows the line of stability under chromium saturation where diamonds will breakdown.  Some diamonds remain stable in the graphite field because the conditions do not last long enough to degrade the diamonds.  But if G10 garnets fall above the diamond-graphite equilibrium line it is a pretty sure bet you are on the right track for diamondiferous kimberlites.  And that is precisely what Fipke kept finding in in his samples of glacial debris as he flew along with Blusson (who not only has a PhD but is a pilot) periodically sampling them.  The long-gone glaciers were pointing the way.

garnetAfter Nowicki et al., 2007

At the time in the mid 1980s, geologist understood the relationships between these indicator minerals and diamonds, but how could the information be used to find the kimberlites in the Canadian craton?  What was unique about Fipke and his partner Blusson was the way they approached the problem.  They knew that the glaciers were powerful enough to gouge out the relatively soft kimberlite and carry the indicator minerals long distances destroying any signs of the kimberlites at the surface and subsequently burying them under debris carried by the glaciers when they melted.  They reasoned that they might be able to sample glacial deposits and “walk” the indicator minerals back to their source.  Standard Oil liked the idea and funded their exploration at first.  No one knew then that it would take eight years, millions of exploration dollars, and several companies before they hit pay dirt.  De Beer’s geologists also knew the answer was in the glacial remains, but to them it was a nine to five job and the season ended after 8 weeks of summer collecting.  For Fipke, it was a life’s dream, and nothing terminated his resolve collecting well into the cold months of the far north.

Fipke and Blusson focused on eskers (see the esker shown below) which are sinuous ridges of stratified sand and gravel deposited by water flowing in tunnels of ice within or under the glaciers.  As the glaciers recede the ridges remain like compasses indicative of the direction the water and ice once flowed.  If the glaciers rumbled over kimberlites, the proof would be in the streams that carried the glacial till away.   They kept going even after Standard Oil called it quits.  The G10 garnets kept telling them they were on the right road and the mining giant BHP believed them when they began running out of money.  Dia Met, the company Fipke and Blusson formed, signed a sweet deal with BHP.  BHP agreed to fund the exploration for a 51% stake.  Within six months after teaming with BHP, Fipke had come to a point where the G10 garnets disappeared near Lac de Gras.  Fipke knew he was close to the source.  As the story goes, he noticed a lake from the air that looked like it sat in a bowl-shaped depression near where the G10 garnets disappeared.  He had to have a sample of the rock in that depression.  They landed the plane on the lake, rowed to shore, and started to dig, but after many hours they were still in glacial till.  They decided to walk the shoreline for a better place to dig.  That is when Fipke’s son Mark, found a piece of kimberlite.  They were all ecstatic — the lake must sit on the pipe.  Gurney eventually analyzed the mineral assemblage and verified that it was highly likely to be a diamond-bearing kimberlite.  BHP quickly flew a geophysical survey which showed a distinct structure below the lake.

FulufjalleteskerEsker in Sweden (Hanna Lokrantz Wikipedia)

BHP and Dia Met started quietly staking as much land around the lake as they could.  Kimberlite pipes frequently occur in bundles so it was imperative that they obtain rights to as large a region as possible before word got out of the find.  While they were staking, BHP flew a drill rig in by helicopter and cored 455 feet under the lake pulling out beautiful samples of kimberlite 33 feet below the glacial debris with 80 plus small diamonds. Canadian law requires that companies announce to their shareholders when a potentially profitable body is found.  On November 12, 1991 they announced the results from the core including the fact that a few gem-quality diamonds had been recovered from the core.  All hell broke loose, and the rush was on by large and small companies alike to stake as close to BHP’s claims as possible in the hopes that other pipes might be buried nearby.   BHP would go on to discover more than 150 kimberlite pipes helping to make Canada the third largest producer of diamonds in the world.  De Beers even found a few mines.  Fipke and Blusson became billionaires overnight (if you don’t count the 8 years of exploration).

The image below shows the Etaki mine – one of the producing mines staked within Fipke’s original claims.   The large circular depressions in kmberlite represent part of the open-pit mining operations BHP is running.

 

Untitled-1 copyEkati mines from the air (Google Maps)

  1. Shirey, S. B. and Richardson, S. H. (2011) Start of the Wilson Cycle at 3 Ga shown by diamonds from subcontinental mantle: Science 333, 434-436
  2. Pearson, D. G., Davies, G. R., Nixon, P. H., and Milledge, H. (1989) Graphitized diamonds from a peridotite massif in Morocco and implications for anomalous diamond occurrences: Nature, 338, 60-62
  3. Russell, J. K., Porritt, L. A., and Hilchie, L. (2013) Kimberlite: rapid ascent of lithospherically modified carbonatitic melts: In Pearson, D. G. et al, Proceedings of 10th International Kimberlite Conference Vol. 1 p. 195-210
  4. Nowicki, T. E., et al. (2007) Diamonds and associated heavy minerals in kimberlite: A review of key concepts and applications: Developments in Sedimentology, 58, 1235-1267
  5. Cross, L. D. (2011) Treasure Under the Tundra: Canada’s Arctic Diamonds: Heritage House Publishing Co