Tuesday, 15 November 2011

Radioactive paradise (slightly)

The areas of the Tweed Valley, Nightcap National Park and Byron Bay are often seen as fresh clean and natural. Well, I can argue that especially Byron Bay may be a little unnatural but certainly there is a feeling of 'freshness' with the rainforests and the beaches. Given this, few people would think that you'd get a bigger dose of radiation from living in these areas than you would in Brisbane or Sydney (even living near the Lucas Heights Reactor).

Few people realise that radiation occurs naturally in the environments in which we live. Yes, most of you would know that the Sun is a thermonuclear power station bombarding Earth with gamma radiation on a daily basis. But it is also a natural part of the earth and actions either natural or man made can result in these areas being elevated in radiation. In the cases below the sources are formed through different ways but all provide an increase in radiation sometimes thousands of times higher or more than what would be considered background.

Let us look at the little village of Uki first. This little place is located in the Tweed River valley and is known for its rainforest surroundings and rugged, scenic landscapes. Geologically some of the area around Uki is situated on mesozoic aged rhyolite of the Chillingham Volcanics and this rock type provides an added level of radiation due to the minerals that exist naturally in it. But even more interesting is that a mineral exploration company discovered a very tiny sized but significant anomaly in the radiation levels just south of the village. The source was not clear but sampling showed that a five square metre anomaly existed in the already slightly elevated rhyolite terrain background radiation. Analysis showed a nearly 0.05% concentration in uranium which is quite high. This is many thousands of times higher than the normal level expected. The reason for this anomaly remains unknown.

Byron Bay is located on the southern side of expansive active and historic beach systems. Much of the Byron Bay area (and much of the north coast itself) was subjected to heavy mineral mining up until the 1980's but this has ceased now. The heavy minerals sought after were mainly titanium rich ilmanite and rutile and there are other heavy minerals too such as zircon and monazite. These minerals were naturally enriched through the processes of wave and tidal action which created zones amongst the dunes that were targeted for mining. But many of the left over heavy mineral sands were not needed once the rutile and ilmanite were removed. So the left over mineral sand was discarded in some cases used as fill for future building sites. Little did people realise monazite rich left over sand would cause issues which may be unsafe for building homes on. This is because monazite is a radioactive mineral and when the residually enriched sands were dumped this increased the concentration of thorium and uranium and the associated radiation. In fact this situation didn't just occur at Byron Bay but all along the north coast.

More broadly, but less significantly many areas where rhyolite or granite is the underlying rock also have higher than normal background radiation. This too is because of radioactive minerals being enriched naturally when these sorts of magmas are being formed. So this would apply to areas in or close to the national parks of the nightcap ranges and many areas inland in the headwaters of the northern rivers such as the Clarence or Bellinger Rivers and large expanses of the New England tablelands.

References/bibliography:

 *Pechiney Resources (1970). Report on air and ground prospection, Clarence-Moreton Basin, EL 278, Nimbin - Murwillumbah area. Unpubl. Exploration Progress Report.

10 comments:

  1. Thanks Mark,

    I don't know whether some of these more obscure things are interesting or not so thank you for the encouragement.

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  2. Nice post Rod, I was in Byron at the time the council were wandering around with Geiger counters. I don't know how true this is, but according to Byron gossip, the most radioactive site was where Woolworths is today. They say this was the site of the processing plant.

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  3. Hi Dylan,
    I was not aware of the actual location of any processing facilities so that is interesting gossip!

    Just a note on the safety aspect is that when ever a new development in areas of known sand filling is carried out assessments are required by the developers to demonstrate that the land is suitable for the nature of the development. For example houses would require a low level of exposure and revolves around continuous exposure to a 2 year old child or X number of years with X safety factor etc which means that new approved developments are safe to the public or residents etc for the use they are approved for.

    I probably should have mentioned that in the post too... too late to bother changing it now. I don't want to be alarmist!

    While I'm thinking about this have you been to the abandoned Elsmore mine near Inverell???... that is a great site for huge amounts of radiation! Barrels of monazite sand!

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  4. Hi Rod,

    Yes, I have been to the Elsmore tin mine. It’s a pretty barren place and situated on one of the New England Fold Belts “hotter” granites. As far as I can make out this is because these granites have “cooked” for a longer time in the crust and have taken a longer time to come to the surface. We brought a Geiger counter and got some abnormally high readings in the sorting shed where the tin ore was sifted from the crushed granite- we didn’t hang around for long. The longer the length of time these magmatic bodies spend mingling or slowly melting and mixing in the Earths crust the larger the crystal growth.

    Smoky quartz crystals can be found at this site and is evidence of the radiation output of these granites. These crystals start off as clear or “pure” quartz, but after millions and millions of years these crystals become so bombarded by radioactive molecules that they become clouded. This is because each radioactive molecule hits the structure of the pure quartz crystal destroying atoms in minute trails that slowly destroy the crystals ability to reflect light.

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  5. Very interesting post, Rodney. Many people would be concerned at the amount of radiation we have as a normal background, let alone the extra due to mining activities.
    But in general, it is all a part of life on this wonderful and diverse planet.

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  6. Uki is on the south arm of the Tweed River.

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    1. oops. I should have picked that up earlier. Fixed now. Thanks.

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  7. Radio active sites around Byron Bay include all the coastline and any inland areas where there was sand, registered over 100 properties around the Byron Bay locale. There was a scandal about in the papers in 1983 to 1985, which is all still in the archives. The sites of Byron Markets and Byron Highschool were covered in 6 feet of top soil because of it. But take a geiger reading at any place where sand has been dug up, such as new building works, or beach washed away, or trees with established roots, or even some cow pats. I learned about it from professor and students from Lismore Uni going all over IQ.org.au with geiger counters in the mid 1990's, I was one of the meet and greet crew. I didn't quite understand the importance of it until close friends from Germany, living on a property in Tyagara in the radioactive region, had an unusually and badly deformed baby. It doesn't take an expert to understand why it's all been keep under wrap$

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    1. Hi Anne,

      Yes, you are quite right. The natural concentrations of radioactive minerals as well as areas where they have been concentrated by mining occur over a large area.

      Sadly birth defects can just occur anywhere but the frequency is assumed to be greater where there is more radiation. Ironically this means that flight attendants and x-ray technicians etc experience more radiation than any other group but I understand that even these groups do not show a higher rate of problems. This is reassuring, but it is important to take precautions regardless.

      I don't agree with your comment about it being kept under wrap$. There is plenty of information available both official and unofficial... and the official information is the best quality! Regardless, your sentiment about being aware of the land around us is essential.

      Cheers,

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