YY # 2 Yamarna giant ring structures. Comparison of the radiometric and Landsat Giant Ring Structures. Independent Coincident Evidence of the radiometrics.
Yamarna Landsat giant ring structures
Yamarna enhancement
The Yamarna rings had previously been searched for on raw Landsat images without success. So the simple tools of contrast and sharpness enhancement were used to examine them in the same way as had been done with the Leonora ring (Watchorn 2017. YW #1. https://www.geotreks.com.au/work/giant-ring-structures/australia/archaean-meteorite-impacts-in-western-australia-real-or-imagined/ ). They were visible immediately. They are not as perfect as the Leonora ring but some are quite clear, despite almost no outcrop and the desert sandplain cover. It was deduced they should be observable as the radiometric images of the Yamarna GRS are very clear and radiometrics only measures radioactivity from the surface metre.
Structural Geology
The Yamarna rings do not appear to be related to the structure of the surface geology. The ring structures project through surface crust which ranges in age from 3.2 Ga in the Yamarna Terrane to 1.5 Ga in the Fraser Orogen to Cretaceous and recent in the east. This suggests an underlying crustal architecture that is not represented by the near surface (0-20km depth) geology.
There has been a huge volume of extrusive and intrusive rocks pushed through the lower crust to the middle and upper crust (Blewett 2012 p 89) and it is suggested that this huge outpouring is what controls the structure of the intensely deformed near surface geology. Much of the post 3.2, 2.9 and 2.7 Ga magmatic rocks intrude up the ring structures where they intersect the NNW greenstone belts which suggests that the GRSs are at least this old – yet they’re still circular?
The prominent, dark centre of the Plumridge GRSW stands out as an area of outcrop. Is this because it is a similar pop-up structure to the Leonora GRS (Watchorn YW # 2, 2017 https://www.geotreks.com.au/work/giant-ring-structures/leonora-ring-circular-pop-structure-discovery-new-giant-ring-structure-real-imaginary/
Mineralisation and exploration targeting on the Yamarna GRS.
The Tropicana and Gruyere mines lie on the Landsat rings which correlate with the radiometric rings Watchorn 2017. YY #1 https://www.geotreks.com.au/work/giant-ring-structures/australia/2-giant-ring-structures-gold-far-eastern-yilgarn-meteorite-impacts/). The next paper will examine exploration targeting using the GRS, regional geology and the radiometric signature of the mines already found.
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| YY #2 Yamarna Landsat ring study | 1.1 MB |