YW #1. Are the Giant Ring Structures in the Yilgarn Craton of Western Australia evidence of Archaean meteorite impact craters? What is their Exploration Significance? Research Project.
Leonora ring structure in Landsat.
This is the first paper in the above research program to define Archean meteorite impact structures.
Author’s research. In 1998, the author used gravity data to define structural trends over the Northern and Eastern Goldfields to assist in gold mineralization targeting. The Watchorn giant ring structure was found, centred 40 kilometres NNE of Leonora, at longitude 121°25’E and latitude 28°25’S (see figure 1 inset A). The concentric nature of the gravity rings, central gravity low and annular magnetic highs suggested a meteorite impact structure.
This research project is designed to answer the following questions;
What is the location and number of giant ring structures in the Yilgarn craton? Why and how did they form? Are they formed by impacts, plumes/hotspots, plutons, ring dykes, calderas, core metamorphic complexes, mantle degassing or by other methods? When did they form? What is their role in the formation of the Yilgarn craton? Why do they correlate with the most intense mineralisation? Are they a cause of mineralisation in the Yilgarn?
Why are multiple complex giant ring structures seen in abundance on our planetary neighbours but not on Earth? It is generally stated in geoscientific literature that the Earth’s crust has been so recycled that most traces of early Earth forming processes have vanished. The underlying premise of this research is the hotly debated topic that quite large areas of Earth’s Archaean crust (from 4.3 Ga to 2.5 Ga) have existed right through to the present with little modification and that multiple giant ring structures are therefore still preserved in the Earth’s middle and lower Archaean crust and the upper mantle. However, because they rarely reach the current surface they cannot be easily traced on the ground and are thus not recorded. This results in a lack of geological verification by field study which causes uncertainty as to their existence, mode of formation and usefulness. They are therefore not given the same credibility or research effort as other easily seen major structures.
This detailed research has not been done. Giant ring structures are not fully recognised or used for exploration worldwide. The project is significant because if its premises are proved valid then it will expand the concepts of the evolution, mineralization and exploration targeting of the Yilgarn Craton, and by default other Archaean Cratons. The circular features of four giant ring structures in the Yilgarn are shown in figure 1.
Figure 1. Yilgarn Giant Ring Structures empirical geological and geophysical evidence;
Inset A. Watchorn GRS has expression of Leonora Ring in Landsat (X), Agnew Ring in gravity (Y) with radiometric (inset background) that closely superimpose suggesting they are involved in a regional (250 km diameter) geological process and are not just local non-geological artifacts. The Agnew ring is ovoid NS. Inset B. O’Driscoll GRS in radiometric data (GSWA data). The salt-lake palaeochannels often define the rings. Inset C. Malgar GRS centre in magnetic data (GA data). The Eastern half is obscured by later greenstones. These rings have a similar appearance and dimensions to those at Chicxulub meteorite impact in Mexico. Inset D. Mt Cauden GRS in gravity data (GSWA data) shows an eastern arc (D), magnetic data (GSWA) exhibits clearly visible central and median rings and radiating greenstone belts (E) and fact surficial geology shows a western outer arc that is symmetrical to the eastern gravity arc. (F). Inset E. Yilgarn Geology plan (Blewett and Hitchman 2006) shows the GRS are unrelated to the regional NNW geology trend. Enlarge to see detail
To view the full paper click this link ….
| Watchorn GRS Research Leonora ring 9 May 2017 | 2.7 MB |
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