Sunday, 1 September 2019

Tonga comes to visit... again?

The effects of Tongan undersea volcanic eruptions are not the first thing you'd think of when enjoying the summer weather on a sandy beach at Kingscliff, Byron Bay or Port Macquarie. But 6 years ago, in 2013 there was a direct reminder of a volcanic eruption of the the undersea volcano the Havre Seamount. This reminder was pumice rock washed ashore from an eruption which took place about 6 months previously. You can read more about it on the blog post I wrote at the time. It looks likely a very similar thing is going to occur in the next few months.

In mid August this year (2019) it was observed that a massive 'raft' of pumice rock was floating west of Tonga. A small island called Fonualei showed evidence of recent activity, with steam and fresh pumice in the area. The extent however of the eruption went unnoticed until a sailing boat sailed through a huge pumice raft. ABC News has a great video of what sailing through the raft looked like.
Photographs from passenger aircraft and also some satellite pictures have shown that the size of the eruption must have been huge. The Island of Fonualei was active but clearly not the main location of the eruption. We'd all be very aware of the eruption if it was Fonualei erupting the volume of rock obvious from the satellite. A formal but short report on the eruption by the Smithsonian Institute can be found here.

Given that the prevailing currents and winds will direct this pumice onto the coast of Australia it is something to look out for. Biologically it is interesting too. Fresh pumice washed up on the shore can transport various sea creatures. This is because pumice makes a great home given its porosity.
Not much more to add, except a prediction. I don't know how good it will be but I guess that come mid summer we will see pumice from Tonga washing up on the beaches of NSW and Queensland.

Thursday, 22 August 2019

Bottled Tweed Shire Spring Water - The Biffo!

I’ve been meaning to address the ‘bottled spring water' discussions that have been going on for quite some time in the Northern Rivers. I guess better late than never is OK. The recent request by Tweed Shire Council for comment on their draft planning proposal made me think it was worth putting some ideas up now. This is not a very technical post, more of a bureaucratic process one. Note it does not include surface water issues which are legally very similar and tied up with groundwater, it also does not consider the other issues such as road damage from haulage of water, construction of water supply pipelines etc). To be very clear... this is also tagged as an opinion post. It contains my personal views and opinions on the matter - they can be very different from yours! Feel free to let me know what your opinion is in the comments section below.

Can't find a relevant photo... so this will do!
To give some background, groundwater in the Tweed Valley is derived from two main aquifer types, either deep fractured rocks of the (administratively called the New England Fold Belt Coast Groundwater Source), or shallow groundwater systems of the sediments of recent alluvium (Such as the Tweed Alluvium Water Source). I understand that most (or is it all?) of the groundwater that is extracted in the Tweed Valley that ends up in water bottles is from the deeper groundwater source.
 
Tweed Council is proposing to prohibit new water bottling facilities in rural zoned areas of the shire. One of the reasons overly simplistically outlined for this proposal by the Tweed Daily News is that “there is not enough data on groundwater resources to fully understand the environmental impacts of the industry”. The Planning proposal document also says “…there was a perception that water belongs to the community and should not be used for private profit.

This raised my eyebrow. 

Access to groundwater in NSW is controlled by the state government. This is in two forms: 
  1. 1. The actual well or borehole that is to extract water is licenced by the state. 
When and individual wants to install a bore a water supply works approval application must be made to WaterNSW. Staff experienced in groundwater (including hydrogeologists) assess the application against plans (Water Sharing Plans) that have been developed to protect the environment from badly extracted water, including too much extracted water over periods of time, the possible impact on neighbouring groundwater bores and groundwater dependent ecosystems 
  1. 2.Water is owned by people and companies. The water itself when not used for basic landholder rights (e.g. stock and domestic) is licenced by the state and capped based on the water source (Water Sharing Plans). There is no automatic community right to any water unless it is basic rights water – which the Water Sharing Plans prohibit from being adversely affected. 
If an individual wants to extract water that is not for basic landholder rights they must buy water from some other producer in the water source. This means that the amount of water extracted cannot be increased. The plans that are in place also place a limit on how much water for different uses can be extracted from a source. I think the category of water in the case of bottling water would be Industrial Use. The limits on water have been set by hydrogeologists and state planners and are outlined in the Water Sharing Plans.

Slight differences to the above process are where a development is classed as state significant development, these are assessed in an even more detailed way (and by another organisation – the new Natural Resources Access Regulator). However, even in this case the extraction rules in the Water Sharing Plans cannot be ignored. 

In addition, the NSW Chief Scientist is due to release its final report on the impact of the water bottling industry on the North Coast. Being a state government review conducted by hydrogeologists this review has the potential to be the most useful for decision making and can directly feed into modifying the Water Sharing Plans or other licencing processes if there is shown to be a deficiency.  

Given that water is managed by the state government I was surprised to see that there is an expectation by some that Tweed Council should seek to manage water using local planning instruments. It is interesting that if a bottling plant is proposed in a rural area in the Tweed it requires Council consent now, and concurrence from other environmental agencies. In fact local government is legally required to refer such matters on to the appropriate state government department for these matters.  

I’m not saying this is the wrong way to manage water it is just, in my view, a very novel and creative way given the state has ultimate authority over water resources. How can a local government place rules that stop new water bottling plants to be constructed, but cannot stop water that is legally owed by someone and allowed to be used for that purpose under state rules? I guess this is one way you can… but a very cumbersome and possibly unnecessary way? If there is an expectation that the community owns the water, should the community actually be buying the water? I don’t fully know, as always I have more questions than answers! 

Anyway, the draft proposal in on public exhibition until the 17th of September 2019. Go to www.yoursdaytweed.com.au/waterbottling for more information or to make a submission.

Friday, 21 December 2018

Faulty Gold - The Enmore Goldfields


I was undertaking a project on a private property near Enmore, south of Armidale last weekend. This gave me the opportunity to visit some abandoned mine sites and have a look at the country. The property I was on consisted of two stratigraphic units, the Girrakool Beds and the Enmore Monzogranite. The area I was most interested in was the boundary between the two units. Where I was the boundary is defined by a fault known as the Borah Fault.  The fault zone is quite easily observed through topographic and drainage features, but also there has historically been some gold extraction from some locations along this fault including two mines that I got to visit (Buffalo Ranche Mine and Sherwood Mine).  These mines make up part of the area sometimes referred to as the Enmore-Melrose Goldfield.


Old mining equipment Sherwood Mine
The regional geological mapping identifies that the north of the Sherwood Fault are blocks of the Girrakool Beds. This geological unit is dominated by mudstone (slate) and greywacke (lithic sandstones) with rare chert and basalt (Gilligan et al 1986) and is sometimes considered of Permian age (e.g. Binns 1966, Leitch 1974) but is more likely Carboniferous Gilligan et al 1986). It appears to me that the Girrakool Beds in the Enmore area have not been studied extensively but other areas well to the North east of Armidale have been much more studied because in that area they have undergone extensive and complex metamorphism. 


South of the Borah Fault, as well as some fault bound blocks to the north of it is the Enmore Monzogranite. The Enmore Monzogranite is a name given to a biotite monzogranite of S-Type derivation (from melted sedimentary rocks) commonly with a foliation (preferred direction of mineral alignment). The quartz in the unit is usually of a blue colour and there is occasionally amphibole. garnet and even some graphite present in some places too. It commonly contains xenoliths. The Enmore Monzogranite has been classified as part of the Hillgrove Supersuite. As far as I can find, the Enmore Monzogranite has not been dated accurately and therefore only has an inferred age of Carboniferous or Permian.


Remnants of the old Sherwood Mine
The Borah fault can be traced for quite some distance because the faulting has affected the rocks (which area now called mylonite, breccia and fault gauge). The shearing stresses caused by movement along the fault has recrystalised some of the rock and broken up other areas. Because of this action the affected rocks have been weakened and are more susceptible to erosion. This means that over time creeks have preferred to flow along the fault strike. For example one creek, Postmans Gully flows along the fault towards the north-east and another, Borah Creek flows along the same fault in the opposite direction (towards the south-west).


Some old mining equipment still remains at Sherwood Mine, with the remnants of a steam engine apparently manufactured about 1878 still visible. Historical mining records (Henley 1985) show that approximately 7.9kg of gold was extracted in 1893 then in the period up to 1937 a further 2.6kg was produced. Follow up exploration was carried out from time to time, particularly in the 1970’s to 1990’s but no significant economic concentrations of gold were identified. I note that the geology superficially appears similar to the nearby Hillgrove mines area but on further inspection it appears that all of the substantial mineral deposits lie in a thin zone around and along the fault line. The mineral deposits are also of a quite different chemical make up with low concentrations of Antimony, which distinguishes it from the major mineralisation events that formed many of the Gold-Antimony deposits from the nearby Hillgrove Gold Field. 


As mentioned, the most significant gold occurrences in the Enmore-Melrose Goldfield are located on, or adjacent to the Borah Fault (and nearby Sherwood Fault). This indicates the faults are likely to be a structural control on the gold mineralisation.

Monday, 11 June 2018

The NSW/QLD border geological mess and other matters - Talk at Binna Burra

This year marks the 85th birthday of the Binna Burra Wilderness Lodge in Southern Queensland. As part of the 85th celebrations the lodge has invited many people to give talks at the lodge between the 20th and 24th of June. There are many interesting science and nature talks open to the public on these days and two of the talks will have a geological theme. The Lodge is situated on the northern side of the Tweed volcano and the landscape and ecology of the area is intimately connected with the geological history of the area.

I will be giving a talk on the evolution of our understanding of the Tweed Volcano over the years and how politics can affect how we scientifically look at our part of the world. My talk will be on Friday 22nd June at 9.30am. On Sunday 24th, Warwick Willmott will be giving a more geology overview walk and talk including discussions on how the Tweed Volcano and Hawaiian Volcanoes have many similar characteristics.

UPDATE: Due to personal matters I have had to cancel my talk. The Talk by Warwick Willmott on Sunday is unaffected.

The details of my talk are as follows:


Talk title:
Our understanding of the Tweed Volcano: A Learning, Unlearning, Forgetful and Confused Experience.

Abstract:
The landscape of the NSW/QLD Border (Lamington and Tweed areas) being the result of a single volcanic centre, has been recognised formally for less time than the establishment of Binna Burra Lodge (only 70 years). Since this first realisation, many researchers have added to understanding of how the landscape has evolved. However, sometimes even in our modern and scientific world new knowledge can get lost, be ignored, or repeat old myths. This talk will cover some of the evolution of our understanding of the Tweed Shield Volcano and examine some of the persistent ‘popular science’ myths of this landscape.


For details of events being held at Binna Burra Wilderness Lodge you can visit their facebook page:

https://www.facebook.com/pg/binnaburra/events/?ref=page_internal