Saturday, 12 September 2020

Where Does the Carbon in Diamonds Come From?

Where Does the Carbon in Diamonds Come From? 

this week I found THIS ARTICLE on the Earth-logs blog. It is based on THIS PAPER. It was thought that the carbon came from subducted sedimentary rocks. Then we thought of the basalts in the oceanic crust. Their reaction with aqueous fluids results in carbonates.

Current research uses the isotopic chemistry of carbon and nitrogen in the diamonds and the tiny silicate minerals included in them. Most of these are garnets. From the studies the depth of formation can be indicated and this can help determine the carbon source.

And it seems that the oceanic basalts are the favoured source.

But VERY deep diamonds - formed below 660km - may be different. The isotopes suggest that the carbon source is within the mantle and ultimately the stellar dust that accreted to form the earth. But at that depth the carbon is incorporated in metals and carbides. The authors suggest that subducted slabs, reaching that depth, release watery fluids which mobilise the trapped carbon and allow the formation of diamond.

Diamond crystal containing a garnet and other inclusions (Credit: Stephen Richardson, University of Cape Town, South Africa)




Friday, 4 September 2020

Hibernation is Not New

 Hibernation is Not New

A correspondent brought THIS ARTICLE to my attention.

Lystrosaurus is the creature which survived the end-Permian mass extinction. In the Triassic they were found all over Gondwanaland. The specimens used in this study came from what is now Antarctica and South Africa. In Triassic times Antarctica was within the Antarctic Circle, South Africa outside it. 

Lystrosaurus is characterised by having tusks, which like elephants tusks, grow throughout their lives. And they have growth rings. The South African specimens have regularly spaced rings, the Antarctic ones have the same but also closely-spaced, thick rings.

a A cross-section of Antarctic specimen UWBM 118025 with a “hibernation zone” highlighted at a higher magnification. Scale bars = 1000 μm. b Well-preserved regular incremental growth marks from the South African specimen UWBM 118028, lacking “hibernation zones”. Arrows denote individual lines with an average spacing of 16–20 μm. Scale bar = 100 μm.

The authors argue that this indicates the Antarctic creatures were hibernating - or something very like it. Which is not really surprising but nice to have some evidence for it.

The original article is HERE.


Tuesday, 1 September 2020

Methane Outgassing in Siberia

 Methane Outgassing in Siberia

By chance I came across THIS STORY in the Siberian Times. it seems, that with global warming methane is being released by the permafrost, often with spectacular results.

 The new funnel filmed from air by the team of Yamal-based TV station. Picture from July 2020 by Vesti Yamal. Note the figures for scale.


The other pictures in the article are equally spectacular. 



This is a rather worrying development. Methane is a more powerful greenhouse gas than carbon dioxide and there is believed to be vast quantities of it captured in the permafrost. If it continues to be released it will trigger a vicious circle.


Saturday, 29 August 2020

Tuatara Genome Revealed

Tuatara Genome Revealed 

A correspondent has brought THIS ARTICLE to my notice. It tells of how the genetic material of the tuatara was collected, in collaboration with the iconic species Maori guardians. Without their cooperation the material could not have been gathered. 

The genome is 50% larger than the human genome and is one of the largest ever published. One purpose was to reconstruct the creatures evolutionary tree.

A tuatara in New Zealand. Credit: Pete Oxford/NPL


And here is its evolutionary tree - the simple version.
 Refining the evolutionary tree for reptiles, birds and mammals. This phylogenetic tree includes six branches: mammals and five branches within a clade called sauropsids, which comprises reptiles and birds. One of these, the Rhynchocephalia, has only one living member, the tuatara. Gemmell and colleagues date the divergence of the Rhynchocephalia from the Squamata to about 250 million years (Myr) ago


And here is the more complex version, taken from THE ORIGINAL PAPER.

a, The tuatara, (S. punctatus) is the sole survivor of the order Rhynchocephalia. b, c, The rhynchocephalians appear to have originated in the early Mesozoic period (about 250–240 million years ago (Ma)) and were common, speciose and globally distributed for much of that era. The geographical range of the rhynchocephalians progressively contracted after the Early Jurassic epoch (about 200–175 Ma); the most recent fossil record outside of New Zealand is from Argentina in the Late Cretaceous epoch (about 70 Ma). c, The last bastions of the rhynchocephalians are 32 islands off the coast of New Zealand, which have recently been augmented by the establishment of about 10 new island or mainland sanctuary populations using translocations. The current global population is estimated to be around 100,000 individuals. Rhynchocephalian and tuatara fossil localities are redrawn and adapted from ref. 1 with permission, and incorporate data from ref. 2. In the global distribution map (c, top); triangle = Triassic; square = Jurassic; circle = Cretaceous; and diamond = Palaeocene. In the map of the New Zealand distribution (c, bottom); asterisk = Miocene; cross = Pleistocene; circle = Holocene; blue triangle = extant population; and orange triangle = population investigated in this study. Scale bar, 200 km. Photograph credit, F. Lanting.

 The papers are interesting as they give an insight into modern biology. 

Down to Earth Extra - September 2020

 

DOWN TO EARTH EXTRA - September 2020


The latest edition of Down to Earth Extra is HERE.

And you can read it below.


Wednesday, 19 August 2020

Zoom Geological Webinars from Cardiff University

 Zoom Geological Webinars from Cardiff University

The School of Earth and Ocean Sciences at Cardiff University is organising a series of Zoom webinars, held at 5PM on Wednesdays.

You can read all about it HERE. Instructions on how to join the webinar are on the site.

I have missed the first couple of seminars but the full list is as follows:- 


Dave Green's Geostudies Programme

 Dave Green's Geostudies Programme

In these uncertain coronavirus times, Dave Green has boldly gone and put together a programme for the rest of this year and next. Let us hope it can go ahead as planned! Dave can be contacted HERE.


Dave writes:-