Intro: One day hopefully, I will get there… but for now, I am starting this post with the truth. No, I have not been to Antarctica (yet!), but by a random chance of events I find myself the owner of a collection of rocks from Antarctica.
How? Well, long story short, on the plane ride to the gold mine I am researching I was sitting beside a mechanical worker who used to live in Tasmania and work in Antarctica. After talking about geology and finding out I live in Tassie, he turned out to be quite the rock hound and his wife and him where moving houses and were going to throw away all his old rocks he randomly grabbed during his years working in Antarctica. Thus, I gladly offered to take them off his hands. And yes, I find myself the new owner of a collection of rocks from the great southern land. Most of the rocks were picked up around the Australian Antarctica stations in the 1990’s (apparently it’s illegal to take rocks from the continent now…). So, here is a quick blog on some awesome Antarctica rocks, and a brief introduction to the geological history of the great southern continent.
Science Spiel: What lies beneath the ice (Geology, Geomorphology)
Antarctica’s surface is 98% covered with ice, so the geological history is still incomplete. Rocks of the ancient Antarctica bedrock have been dated to ~ 4 billion years ago (bya), and it was once near the equator and beaming with warm-climate animals and plants such as those found on Tasmania and the rest of Australia. This can be traced back to the supercontinent of Gondwana ~400 million years ago (mya), which coupled many of the current continents such as Africa and India together until plate tectonics slowly drifted these lands apart ~130 mya. One of the last continents to go was Australia (along with Tasmania, my current home), which completely separating only ~45 mya (Coleman, 1980; Kennett, 1980; Exon et al., 1997; Jacob and Dyment, 2014).
Antarctica is geographically divided by the Transantarctic Mountains; one of the longest mountain chains in the world. The area where my rocks are from is the east, near the Amery Ice Field and the Australian stations of Davis and Mawson. Around these stations are the Prince Charles Mountains, Vestfold Hills and Larsemann Hills, which are some of the most significant ice-free areas in Antarctica. Because I’m not sure the exact outcrop my rocks are from, I will just show some of them grouped by area, and a brief description on what they are/where they are from!
Most of the rocks are metamorphic rocks, formed by high temperatures and pressures. They belong to the granulite and amphibolites metamorphic facies.
My first set of rocks is from the Larsemann Hills. The Larsemann Hills underwent low pressure high temperate granulite facies metamorphism ~1.1 bya (Stuwe et al., 1989). I have several beautiful examples of felsic garnet–biotite-quartz-magnetite schist. Other rocks from the Larsemann Hills include a K-feldspar pegmatite, and a pale blue, greasy rutilated blue quartz sample (thank you to David Corrigan from the GSC for the identification help with this one). And lastly, I have copper! An ultramafic olivine-rich rock with pale green copper oxide staining…
Northeast of Larsemann Hills are the Vestfold Hills. The Vestfold Hills are only 100 km away, but they are rougly 1.5 billion years older than the Larsemann Hills, with some age dates putting them in the Archean geological period >2.5 bya (Lanyon et al. 1993). Again, this area has mostly high-grade metamorphic basement rocks and I have several samples of more garnet-biotite gneiss. Another rock that falls into my Vestfold Hills collection is a high-temperature siliceous granulite schist with sillimanite and garnet porphyroblasts. This rock is fairly similar to a khondalite, a rock that makes up a considerate part of India (Krishnan, 1968). Also in Vestfold are large euhedral magnetite chunks, and a feldspar(albite-anorthite?)-quartz pegmatite.
Lastly, I have a couple unique rocks from Mawson’s station and the Prince Charles Mountains. Mawson’s station rocks are a K-feldspar-quartz gneiss and a mylonite (a metamorphic rocks that has undergone ductile deformation due to compactation and shearing) with beautiful porphyroclasts . My lone Prince Charles Mountain rock is petrified wood.
Ah Antarctica… and being here in Tasmania I’m so close, but yet so far! It would be a dream to go there one day, but in the meantime, having a little piece of the land in my office is pretty cool. Again, I haven’t gone into the geological history too much in this post, but while Antarctica was once together with the other continents during Gondwana, it is now an isolated ancient land mass in the far south. My small collection of rocks are a testament to some of the extreme high-temperature and pressure metamorphism that took place in eastern Antarctica. Now to only find some way to convince the government or university I need to go there myself to follow up on these?! Wish me luck, haha.
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