Wednesday, March 22, 2017

Routine science turns clever- laser ICP vs SHRIMP analysis of Archean detrital zircons

So, last year I published a Geology paper. It is summarized in Geosonnet 42; see link therein to the paper itself. As it turns out, the paper deals with Archean uranium mobilization and the sedimentary history of carbonado diamond. But what the paper doesn’t say is that I wasn’t actually trying to do that. More professional researchers than I might know how state in their articles that it was all just a lucky coincidence, but I don’t know how to squeeze that into a short format journal.

What actually happened is that the second author and I realized that we had different pieces of the puzzle which, with the help of some old Japanese data, could be pieced together for a coherent story. So hey, "write it up."  Most of my part of the puzzle was unpublished bits and pieces from my PhD and post doc 15+ years ago, but the SHRIMP data was actually less than a year old, as I had collected it for an entirely different reason.

Back when I was working at ASI, which had just bought the Resolution laser ablation line from Resonetics, a few of us started looking at how the SHRIMP and laser products could best compliment each other. One of the things we experimented with was controlling the SHRIMP with a version of the laser control software. Another thing we wanted to know was whether there was any advantage to using the SHRIMP for detrital zircon provenance studies, so I pulled out my old PhD zircons, remounted them with modern standards, and we programmed a customized version of GEOSTAR to automatically rerun the same zircons (if they hadn’t been blown up) to compare the results. Of course, the laser data was old, and the SHRIMP was trying to make analyses next to laser holes (which distort the extraction field, due to the unfortunate tendency of holes not to be flat), but it generally worked, and the data is tucked away deep in the supplementary section of the paper.

Since there are analytical geochemists who occasionally read this blog, but might not think to look for microbeam comparisons in the appendix of a diamond radiation defect luminescence paper, I thought I’d mention it, and put up some plots that got culled due to space requirements.

The short answer is that fully metamict zircons (like half of the Tombador grains) are open system with either technique, but for zircons that are only a little bit metamict (most of the Jacobina zircons), the smaller ion probe spot and better 204Pb backgrounds improve data quality. Anyone who is interested is welcome to download the Data Repository data (it’s all there) and ask.

Figure 1 (See data repository for full version): Tombador zircon analyses with SHRIMP (red) and laser ICPMS (yellow). The SHRIMP data are, in general, a little more concordant, but there isn’t much in it.

Figure 2 (See data repository for full version): Jacobina zircon analyses with SHRIMP (red) and laser ICPMS (yellow). For this sample, the SHRIMP data are substantially more concordant.

Figure 3:  Probability distribution curves for Tombador zircons analysed by SHRIMP (purple) and laser (Red).

Figure 4:  Probability distribution curves for Jacobina zircons analysed by SHRIMP (tan) and laser (Red). Note that laser peaks are generally broader and offset to younger ages due to Phanerozoic Pb loss.

Tuesday, March 07, 2017

Geosonnet 48

The garden in which life evolved from slime
Did not have apples, naked girls, delights.
Although the details have been lost to time
clay seems more likely, or serpentinites.
Hydrated mantle min’rals do not tempt
But their kinetics none-the-less intrigue
Relationship twixt rock and sea attempts
at understanding help if we know speed.
The magnetite which serpentine expels
Contains trace actinides which will decay.
The helium which in the crystal dwells
Gives cooling time and late stage growth away.
Three million years ago, when Lucy ran
The final Greek tectonic stretch began.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Thursday, December 08, 2016

Geosonnet 47

For two times in a hundred million years
The Earth froze solid, snowball world in space.
The pitcher stretched, the batter’s frozen tears
Held metazoan terror on his face.
If frozen oceans struck for a third time,
While animals were trying to evolve,
Could they survive anoxic paradigm,
A sea ice-covered hunger games to solve.
The timing of the third ice age is key,
And CA-ID-Tims unlocks the truth.
The Gaskiers ice age ended suddenly
Timing constrained by isotopic sleuth.
  A modern ice age, mostly at the poles?
  Or thaw too swift for carbonate controls?

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 

Saturday, November 26, 2016

Happy Thanksgiving

I am cooking a Thanksgiving feast again this year. Last year, I was in Japan, so I ate toxic fish with the nerve agents cut out by an overworked chef instead of cooking a Turkey. When I was a kid, Thanksgiving was at Grandma’s every year. We would play with the cousins and uncles and aunts, and Mom would help Grandma, and Granddad would tell stories about anything from fishing to the War in the Pacific, and we would eventually eat, and then play games or watch TV until we were too tired to do anything but sleep. After my Uncle died, my Grandparents moved farther away, and it was generally just our nuclear family at home until I finished college and headed off to make my way in the world and get as far from New York as possible. My first Thanksgiving away from family was 20 years ago, at the house of a guy I met in field camp who kindly took me in with a bunch of other recent arrivals to silicon valley. At the time I thought that was strange, but two years later I found myself cooking Lasagna in an apartment in Northeastern Brazil, with a woman who was kind of coming onto me but was the ex-wife of the guy I was working with and the ex-daughter in law of the people who were putting me up. My Portuguese was not really good enough to talk my way out of the trouble I somehow avoided, but a couple years later in Australia I met my wife-to-be at another Thanksgiving dinner hosted by another ex-pat PhD student from Arkansas. And somehow, over a decade and a half later, I have a family, a job I can ride my bike to, a house, and a wife who still miraculously puts up with me, despite my lifelong habit of biting off more that I can chew, not succeeding at anything, but somehow finding a continual series of third doors that miraculously allow me to avoid total failure. Despite my constant feelings of inadequacy and dread that I have wasted my potential and lost my way, I seem to somehow be doing OK. I have a lot to be thankful for, and I hope that you all have the same. Have a wonderful thanksgiving.

Saturday, November 19, 2016

Molten metal metamorphosis

The Australian Aluminium smelting industry is having a rough time. Built to utilize electricity from Australian coal from the 1960’s through the 1980’s, our smelters are ill equipped to deal with the migration of the Aluminium industry to a rapidly industrializing China or cheap low-carbon energy areas such as Iceland or New Zealand. As a result, the Kurri Kurri smelter closed in 2012, the Point Henry smelter closed in 2014, and the future for the Portland smelter is currently uncertain, with the contract for electricity due to be renegotiated this month.

At the same time, Australia is lagging the rest of the developed world in the transition to low emissions electricity. Although certain jurisdictions, like South Australia, are making progress, the fragile nature of the grid connections and the intermittent nature on renewable energy is slowing its uptake, and potentially contributing to supply instability, as was seen during this winter’s South Australian storm.

The production of aluminium metal requires a huge amount of electricity. An aluminum smelter basically consists of a huge tub of molten salt, from which the enormous electrical currents basically force the electrons onto aluminum ions, depositing them on the cathode atom by atom at a rate that allows several tons of production per day.
As a result, aluminium smelters are typically located in areas where there is a large, cheap supply of electricity. Traditionally these have been areas of hydroelectric power, or in Australia’s case, cheap open cut thermal coal. With coal getting more expensive, and with concerns over the impact of CO2 production on the climate, these coal-powered smelters are finding it harder to compete in high wage countries. So Australia has facilities which are designed to take a substantial proportion of the energy grid’s electricity, which are getting closed down just as the requirement for storage of large amounts of variable renewable energy is appearing.

One proposed solution of the “storage problem” is the use of a new technology known as the liquid metal battery. Like the aluminium smelting process, the liquid metal battery consists of a molten salt, which can have ions driven out of it to the anode and the cathode when power is applied. Unlike aluminium, the anode is a base metal instead of graphite, so instead of oxidizing the anode and making CO2, the metal is deposited. This allows the battery to discharge by dissolving the anode and cathode back into the molten salt. So if aluminum smelters are going obsolete in areas which are in desperate need of battery storage, it seems like modifying the smelter to store energy is a option worth at least considering.

There are technical issues, of course. An industrial Hall-Héroult cell is the size of a city bus, and a smelter contains lots of them. The liquid metal technology is being developed by a small company, Ambri, which seems to be starting small (like bottlecap scale), and scaling up. So there is a bit of a gap between the emerging battery technology and the aging smelter technology. But it is in everybody’s interest to bridge it.

Ambri is trying to raise cash and start production. South Australia is still investigating their state-wide blackout.  Alcoa and Hydro have two shuttered smelters which they need to remediate or repurpose, and Portland has 11% of its population working at the smelter. In addition, Boyne Island and Tomago are supposedly facing similar market pressures.

Portland would be a particularly useful place for a pilot project, since the smelter is still operating, even though the pain of closing a big industrial center in a small isolated town looms. It is also located in prime wind power country, on the Victoria / South Australia border, close to the interconnector. So it would be nice if the union, the council, the state and federal governments, and the industry groups could work together to see if there is a solution that benefits everybody.

As for Kurri Kurri and Port Henry, the Kurri Kurri remediation plan comment period closed in August, but Port Henry is still open, even though the last public hearing was last week.Thus the rushed, not completely researched blog post.

Monday, October 10, 2016

Blogular quiescence

Earlier this year, I left Australian Scientific Instruments to take a job as Senior SHRIMP Specialist at Geoscience Australia. In between those jobs, I pushed a couple of bottom drawer manuscripts out into journal submission. One has already been published (see Geosonnet 42 for details and link). Others are currently in review or revision. So most of my writing energy is going there, not here. So don't expect a lot of blogular activity in the near future.

Friday, August 05, 2016


Macbeth is my favorite play. My favorite book. My favorite collection of English words. The poetic beauty of the text, the directness of the plot, the representations of madness, supernatural, and reality, and the shear magnitude of the tragedy are what makes it so fantastic. But although, for all of these reasons, it is one of the easiest of Shakespeare’s plays to read, by the same token it is one of the most difficult to play. The sheer beauty of the spoken words, many of which are directed to nobody, makes it particularly challenging for  actors to value-add through their interaction with each other. Thus it is a rare stage performance which does the masterpiece justice. Luckily for me, the Canberra Repertory Theatre here in town has just put on a great production of the Scottish Play.

This is a gaunt production of Macbeth, with a spare stage and simple costumes. From the opening with the witches as a maleficent blur in the gloom of the stage, the focus quickly shifts to an astoundingly dynamic portrayal of Duncan King of Scots. He imbues the opening scenes with a generosity and a charismatic presence that shows all a king can be. Generous, charismatic, leader of a band of brave yet fragile Scots besieged by Vikings, and completely without guile, it is against this that the brutal but utterly bewitching ambition of Lady Macbeth must seduce, and the two of them wrestle over Macbeth’s heart for all of a lively Act 1.

Of course, we all know how that turns out, and from the moment the blood touches
Macbeth’s hands, he comes into his own, playing off a terrifying Lady Macbeth and a wavering Banquo in the maddening spiral that ends with Banquo’s Banquet. That astoundingly potent scene is followed by the intermission, presumably so that the audience can steady their nerves with a glass or two before coming back for Hecate and her hands.

The last two acts do drag a bit, as they feature many minor and less developed characters, and the witches riddle hasn’t been fresh for 410 years. However, the approach to Lady Macbeth’s downfall was new (at least to me), and as Malcolm and Macduff rouse themselves from their personal grievances and man up to take back control of their country, the play builds back up to its bloody triumph.

All in all, it is a superb production of the great play.

Thursday, August 04, 2016

Geosonnet 46

If decompression melting is enhanced
When glacial loads are washed away by rain
Then letting go the ice sheets that advanced
Might wake volcanoes in an arc again.
Unloading helps silicic lavas blow
And then the magma chambers must recharge
Desire for huge eruptions simmers low
Five thousand years ‘till ash beds become large
A glacial load weighs heavy on the soul
Unfreezing lets the middle crust rebound
Explosive lava, free from amphibole
Bursts forth like summer flowers from the ground.
   Frost claims ice will suffice to wreck the world.
   But should it melt, eruptions are unfurled.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47