Building a virtual Earth could be the key for clean energy
Traveling through deep time could help us understand where copper deposits have formed along mountain belts
How large copper deposits form
Many of the world’s richest copper deposits formed along volcanic mountain chains such as the Andes and the Rocky Mountains. In these regions, an oceanic tectonic plate and a continent collide, with the oceanic plate sinking under the edge of the continent in a process called subduction.
This process creates a variety of igneous rocks and copper deposits to form along the edge of the continent, at depths of between one and five kilometers in the crust, where hot magmatic fluids containing copper (and other elements) circulate within networks of faults. After millions of years of further plate movement and erosion, these treasures move close to the surface – ready to be discovered.
Searching for copper
Geologists typically use a set of well-established tools to look for copper. These include geological mapping, geochemical sampling, geophysical surveys, and remote sensing. However, this approach does not consider the origin of the magmatic fluids in space and time as the driver of copper formation.
We know these magmatic fluids come from the “mantle wedge”, a wedge-shaped piece of the mantle between the two plates that are fed by oceanic fluids escaping from the downgoing plate. The oceanic plate heats up on its way down, releasing fluids that rise into the overlying continental crust, which in turn drives volcanic activity at the surface and the accumulation of metals such as copper.
Differences in how subduction occurs and the characteristics of the oceanic plate may hold the secret to better understanding where and when copper deposits form. However, this information is traditionally not used in copper exploration.
Building a virtual Earth
At theEarthByteresearch group, we are building a virtual Earth powered by ourGPlatesplate tectonic software, which lets us look deep below the surface and travel back in time. One of its many applications is to understand where copper deposits have formed along mountain belts.
In arecent paper, we outline how it works. We focus on the past 80 million years because most of the known economic copper deposits along mountain belts formed during this period. This period is also most accurate forour models.
We used machine learning to find links between known copper deposits along mountain belts and the evolution of the associated subduction zone. Our model looks at several different subduction zone parameters and determines how important each one is in terms of association with known ore deposits.
So what turns out to be important? How fast the plates are moving towards each other, how much calcium carbonate is contained in the subducting crust and in deep-sea sediments, how old and thick the subducting plate is, and how far it is to the nearest edge of a subduction zone.
Using ourmachine learningapproach, we can look at different parts of the world and see whether they would have experienced conditions conducive to forming copper deposits at different times. We identified several candidate regions in the US, including in central Alaska, southern Nevada, southern California, and Arizona, and numerous regions in Mexico, Chile, Peru, and Ecuador.
Knowing when copper ore deposits may have formed is important, as it helps explorers to focus their efforts on rocks of particular ages. In addition, it reveals how much time given deposits might have had to move closer to the surface.
Australia has similar deposits, including theCadia copper-gold districtin New South Wales. However, these rocks are significantly older (roughly 460 million to 430 million years old) and require virtual Earth models to look much further back in time than those applied to the Americas.
Future of mineral exploration
Finding10 million tonnes of copper by 2030– the equivalent of eight of the largest copper deposits that we mine today – presents an enormous challenge.
With the support of over a decade fromAuScopeand the National Collaborative Research Infrastructure Strategy(NCRIS), we are in a position to imagine tackling this challenge. By supercharging GPlates in Australia’sDownward Looking Telescope, together with AI and supercomputing, we can meet it head on.
These emerging technologies are increasingly being used by Australian startups likeLithodatandDeeperXand mining companies in collaboration with universities to develop AI’s enormous potential forcritical mineralsdiscovery.
Article byDietmar Müller, Professor of Geophysics,University of Sydney;Jo Condon, Honorary researcher,The University of Melbourne;Julian Diaz, Exploration Geologist,University of Sydney, andRohitash Chandra, Senior Lecturer,UNSW
This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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