Note. The webinar will be split up into about 12 papers.
This paper is a transcription from the video of the AusIMM Webinar at the Western Australian, South West Branch on the 8th April 2021. The language is thus vernacular and not geologese. This should make it more easily read and understood by the majority of readers.
Additions have been made to expand and clarify sections that were abbreviated due to time constraints in the Webinar. References quoted in the webinar, as well as background papers referenced but not quoted in the webinar, are listed in the text and in the references section at the end of the paper.
The primary objective of these webinars is to promote discussion on new aspects of Earth-scale geoscience and how this will change our paradigms on the structural geology of Earth, Plate Tectonics, mineral deposit systems and give new exploration targeting ideas.
Abstract
Modeling. This paper is an introduction to the North American continent evolution and is the first research to be based on ultra-detailed, but broad scale, research from the surface to 2,850 km depth. The exponential increase in detail enables lithospheric geological structures to be clearly seen in plan and section enabling a 3 D model to be made of the continent. It also enables the lithosphere/crust and mineralisation timing relationships to be observed.
Thus, this research is able to give a much more accurate structural geology model of the continent’s evolution than the current hypotheses based on 3D modelling of very coarse lithospheric data.
Geology. North America has some of the most diverse geology and mineralisation on Earth. North America has rocks, or components of rocks, at the surface up to 4.4 billion years old. The lithosphere obviously would be progressively older the deeper one descends.
The strongest ring structure on Earth sits under the centre of the Pacific Ocean. I suspect that this is where the Mars sized planet hit Earth to form the moon. We can also see the impact of this ring structure at the core-mantle boundary at 2,850 km deep. This is still Earth’s hugest heat source and probably drives the Pacific Plate Tectonism.
Plate Tectonics. Earth’s evolution needs a rethink because of this infinitely more detailed Earth-scale data. The current Plate Tectonics theory suggests that North America progressively accreted over the last 4 billion years. Some of the oldest rocks found on Earth are 4.3-billion-year-old green-stone beds found along the eastern shore of Hudson Bay in northern Quebec. It suggests that the Superior craton was part of the oldest small, thin, original continent (Laurentia) which formed 3.8 billion years ago. https://www.livescience.com/31910-north-america-geology-through-time.html
The most startling observation in this ongoing research is that the mantle under Australia, Africa, South America and now North America has brittle deformation right down to the limits of detailed seismic tomography at the Core Mantle Boundary at 2,850 km depth. This study shows that the lithosphere down to 600 km depth most likely formed during the Late Heavy Bombardment from > 4.1 to 3.8 billion years ago.
Thus, the original North American super-continent has remained an unbroken continent up to the present era. It originated as part of an Earth-wide thick lithosphere. It has survived over the last 4.4 billion years despite the action, firstly from vertical tectonics and then Plate Tectonics which commenced, maybe, 2.7 billion years ago. It shows many generations of brittle deformation to the core with no evidence of the widespread ductile deformation required by the current Plate Tectonics theory. Thus, the plumes as shown on current plans and sections cannot free-flow up through this brittle solid lithosphere – and thus do not exist!.
This requires a complete change to the basis of the mechanism of Plate Tectonics, changing it from a free-flowing, world-wide drifting of accreting thin surface continents, to an original rigid earth being progressively broken up (perhaps a glacier is the best analogy). It will be interesting for us to try and discover the mechanism of how this new Plate Tectonics regime can operate. At the moment it raises more challenges than solutions! Hey but that’s science!
Structural geology. Another far-reaching discovery is the recognition of a 4 billion-year-old immovable barrier extending from the surface to the core and from South America through North America to Alaska. The Western Cordillera/Rocky Mountains separate totally different east/west lithospheric morphology either side of where this barrier lies.
The broad structural geology of North America is a pop-up structure. North America is getting pushed by the Asia-European plate to the WSW at 2.3 mm per year but it is also getting pushed north-eastward by the Pacific plate which moves at about 9 mm a year. That’s a total compression of about 12 mm a year, or about a metre every 85 years. The only way this pressure can release itself is upwards or downwards. Hence there are large sub-vertical compression and orthogonal dilation flat fractures under North America extending to the core.
Mineralisation. This lower pressure pop-up structure under North America to the core allows for heat and fluid release.
North America is a rich source of minerals. The main mining fields are located on ring structures and linears observed from the surface to the limits of detailed plan data at 600 km depth.
The mechanism and source of the fluid for most mineralisation may have been discovered by this research. The fluid source is suggested to be from passive resorption of the lithosphere by heat from as far down as the core. This fluid/magma then flows up vertical linear and ring structures to the surface, scavenging and depositing minerals along its path. These structures have been defined down to 2,850 km depth.
My research shows that this mechanism also occurs in Australia, Africa, South America, North America, China and FennoScandia. This suggests a close connection between deeply buried LHB impact structures, world girdling linears and mineralisation. Once this relationship has been firmly established, and acted upon for mineral and energy targeting, a leap forward will have been made in exploration understanding and success.
1. Introduction
Figure 1. Introduction slide to webinar outlining the new paradigms discovered by my research (see slide above).
New paradigms are discovered while researching North America are;
Earth started cooler and gradually heated up – all original constituents at -100 °C.
The earth started rigid and only started breaking up perhaps in the Proterozoic.
True Plate tectonics only commenced relatively recently.
Planar and ring structures to 2,850 km depth correlating with surface mines.
No lava lamp plumes – lithosphere is generally insitu replaced.
Mineralising fluids from core scavenge and deposit minerals when ascending.
This figure shows the Seismic tomography of the Earth and the areas explored (Dias 2020). I’ve researched Australia, Finland, North China, North America, Africa and South America mainly using seismic tomography down to about 300 to 400 km depth. I have published about 60 papers on this research on my website geotreks.com.au This webinar is on the evolution and mineralisation of North America. The greater continent of North America is about double the size of the continent seen above water.
The webinar will be split up into about 12 papers.
Stay tuned for the most up to date geology on North America, especially the exploration targeting exercises!
Cheers
Bob