Portland here I come

I am currently planning on attending the Geological Society of America meeting in Portland Oregon next month. Australian scientific Instruments has a booth- number 301- and we will hopefully be able to control some ion probes over the internet. I don't know if I'll have access to the talks yet, but if you're at the meeting, stop by, shoot some zircons, and say hello.

Space carnival

121

That's not old

Given that different people have different view on what 'old' is, I thought I'd share this figure from my thesis.



I apologize to any tectonicists who may have wandered in here for describing the Braziliano Orogen (The South American correlate of the Pan-African; one of several continental suture events that led to the amalgamation of the Gondwanaland supercontinent) as 'cover'. But let's face it folks. Thrust sheets get in the way just as much as mud piles do.

So if it seems like I haven't updated my blog for a while, use these numbers to keep a perspective on things...

33S

33-Sulphur, the colloquial name for the atom with 16 protons and 17 neutrons in its nucleus, is one of science’s more interesting characters. Many elements have multiple isotopes. Sulphur, for example, has four (mass 32,33,34,36). And while isotopes are chemically similar to each other, they can be separated to some degree in biological of physical systems. These effects produce what is called mass-dependent fractionation, where the degree of enrichment (or depletion) of the various isotopes is a function of their mass.

Mass dependent fractionation of various isotopes is used for everything from making nuclear bombs to predicting the mass of ice-age glaciers. In the case of Sulphur, it is generally measured by comparing the ratio of ³²S (the most abundant isotope) to ³⁴S (the second most abundant). Calculations show that the fractionation of ³³S from ³²S should be about half of the fractionation of ³⁴S from ³²S. Since ³³S is about 8 times less abundant, and the signal is expected to be half the size, measuring it seems like a silly think to do.

That all changed in 2000 when Farquhar et al. showed that Archean sulphides showed a ³³S anomaly that was not consistent with mass-dependent fractionation. This anomaly is expressed as Δ³³S, the difference between the expected value (based on extrapolation from the measured ³⁴S/³²S ratio, and the measured ³³S/³²S ratio, and is generally only present in archean sedimentary rocks.

One of the few processes that produces mass-independent fractionation (MIF) is photolysis of sulphurous gasses by UV radiation (the exact mechanism is still being researched). So the presence of these anomalous ratios in early sediments is generally thought to be an indicator that there was no ozone or other UV-blocking layer in the atmosphere at that time, and there were enough atmospheric suphur-bearing compounds to be dissociated by that radiation.

In 2003 Mojzsis et al. did some classy ion probe work (using a non-SHRIMP instrument) on in-situ sulphide grains so show where in the rock the anomalous D³³S was located. Our approach was somewhat different.

My hypothesis was that the Monica Lewinsky scandal of the late 1990’s caused enough hyperventilation to such all the oxygen out of the atmosphere and return the surface conditions of Earth to those of the late Archean. So I chose to test this hypothesis my analyzing sulphide minerals grown in the 1998-2000 time period, to see if a non-zero Δ³³S was present. We are breathlessly awaiting the results...

Health insurance blather

Our health fund recently ran a radio ad, suggesting that their product is superior because they paid out 90% of their rates as benefits. This figure is 5% higher than the industry average here in Australia.

Internet rumor has it that the US is aiming for 80%.

Translated into academic language, if your aspiration is to go from a C to a B-, you'll have a tough time getting an A.

Final Arctic minimum sea ice prognostications

The final guesses are shown above.
In the comments of the last post, Crandles was nice enough to put a data table up. With minor corrections, that table is included below. Unfortunately, due to the lousy table support in blogger, I've simply screen captured an excel spreadsheet. Comment if you want the numbers.


Finally, here is a comparison of the aggregate guess to the Wegener Institute forecasts.


Feel free to post links to other professional forecasts in comments, and I will add them. From a statistical point of view, our 'alarmist plateau' has a statistically strange shape.

As discussed in the rules, the prize is a blog post on the topic of your choice. If you're feeling cocky, post your topic now. Otherwise, continue to trash-talk amongst yourselves. And keep watching IARC-JAXA's latest numbers. We should have a winner by the end of September.

Thanks y'all for playing, and feel free to suggest ways of over-interpreting everybody's estimates.

Various space carnivals

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118
119

New Job

As of this morning, I work as a geochemist for Australian Scientific Instruments, a small engineering firm that builds scientific instrumentation, including the SHRIMP. It is a part-time position, so I still get to spend two days a week with LLLL, while still getting paid to push the frontiers of science. So far it has been great- I spent the day learning how to set up sulfur isotopes on the multicollector, for the purpose of teasing 33S anomalies out of really old mud. Tomorrow will be swimming lessons, a playgrounds, and possibly the zoo.

Although selling the instruments isn’t actually part of my job description, if there’s anyone out there wishing to turn several million dollars of stimulus money into a world-class analytical facility, leave me a note in the comments.

OMG look at Mars!

Look up at the sky tomorrow morning (and that morning only), and the planet MARS IS HALF THE SIZE OF VENUS! At 1.5 AU distance, the red planet suptends 6 seconds of arc, while the larger Venus, at 1.3 AU, suptends 12. But this relationship will not last forever! As Earth catches up to Mars in its orbit, and Venus pulls away, this ratio will increase. So act now! Mars has not been this close for 16 months; it will not be closer until tomorrow! And this arbitrary geometric relationship will not occur again until 25 May 2010!

THIS IS NOT A HOAX! The planets will not cease their orbital motions while you procrastinate! Link this post, email your friends, and tweet it now!

Geological Society of America meeting

Are any of y'all going to be in Portland this October? If so, what are you looking forward to seeing, hearing, and/or saying?

Looking for reference help

Anyone out there with a GSA bulletin subscription willing to help me find a paper published when I was 9 weeks old?

Metamorphic petrology is cool, part eleventy zillion

It is abstracts like these that make me wish for journal access:

Drüppel, Kirsten; Lehmann, Christian

Fire bombing of the Tell Halaf Museum in Berlin during World War II - reconstruction of the succession of events based on mineralogical investigations

Abstract:
Basaltic monuments from the Aramaic Tell Halaf (built ca. 1000 BC), Syria were severely damaged during fire bombing of the Tell Halaf Museum, Berlin in World War II. While the museum burst into flames part of the statues were covered with burnt bitumen from the roof of the museum, mixed with fragmented quartz of the roofing cardboard, grinded basalt, limestone artwork, and gypsum casts. Detailed mineralogical investigations of the thin carbon coating on the statues revealed that additionally a number of unexpected, non-basaltic minerals formed in the bitumen via temperature-dependent reactions due to the thermal impact by the bomb blasting and subsequent reequilibration during burning of the exhibition hall. The source material of these newly formed phases was provided by the basalt, the gypsum casts, the limestone artwork, the museum roof, the museum pipe system and, last but not least, the incendiary bomb itself. Phases include sphalerite (zinc of the pipe system + sulphur of gypsum casts), smithsonite (zinc of the pipe system + calcite of limestone artwork), wollastonite (calcium of the limestone orthostats + silica of the roofing cardboard), pyrite (iron of the basalt Fe-oxides + sulphur of the gypsum casts), alkali feldspar (saltpetre of the incendiary bomb + basalt plagioclase), and apatite (phosphorus of the incendiary bomb + calcium of the limestone). A conspicuous feature of samples close to the impact is the abundance of silicate glasses. Observed mineral-forming reactions suggest initial temperature conditions of > 980 °C near the fire centre and of 850-980 °C throughout the museum. The cold water used for fire fighting finally resulted in crack-producing stress that caused severe shelled fracturing of the statues.

European Journal of Mineralogy, Volume 21, Number 2, March 2009 , pp. 443-456
DOI: 10.1127/0935-1221/2009/0021-1901