Sunday, September 25, 2022

Unlocking ancient history of Earth from grains of sand

This new approach allows a greater understanding of the nature of ancient geology.

Sedimentary basins represent the fundamental archive of Earth system processes through deep time. Understanding the tectonic setting of sediment at the time of deposition can reveal important aspects of resource endowment and planetary geodynamics through Earth history.

However, resolving the tectonic setting of sedimentary basins becomes difficult due to the likelihood of overprinting by younger tectonomagmatic and metamorphic processes. As a solution, Curtin researchers have developed a new technique that differentiates extensional, convergent, and collisional tectonic settings based on detrital zircon (DZ) age population characteristics.

This technique has been developed after studying the age of ancient grains of sand from beaches, rivers, and rocks from around the world. It represents crucial advancements in interpreting ancient basin settings that could reveal previously hidden details of the Earth’s distant geological past.

The technique determines the ‘age distribution fingerprint’ of minerals called zircon within the sand. It offers a greater understanding of the nature of ancient geology and a chance to reconstruct the arrangement and movement of tectonic plates on Earth through time.

Lead researcher Dr. Milo Barham, from the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences said, “While much of the original geological record is lost to erosion, durable minerals like zircon form sediments that effectively gather information from these lost worlds to paint a vivid picture of the planet’s history, including changing environments, the development of a habitable biosphere, the evolution of continents, and the accumulation of mineral resources at ancient plate boundaries.”

“The world’s beaches faithfully record a detailed history of our planet’s geological past, with billions of years of Earth’s history imprinted in the geology of each grain of sand, and our technique helps unlock this information.”

Co-author Professor Chris Kirkland, also from the Timescales of Mineral Systems Group within Curtin’s School of Earth and Planetary Sciences, said, “the new method can be used to trace the Earth’s history with greater detail than previously achievable.”

“Zircons contain chemical elements that allow us to date and reconstruct the conditions of mineral formation. Much like human population demographics trace the evolution of countries, this technique allows us to chart the evolution of continents by identifying the particular age population demographics of zircon grains in sediment.”

“The way the Earth recycles itself through erosion is tracked in the pattern of ages of zircon grains in different geological settings. For example, the sediment on the west and east coasts of South America is completely different because there are many young grains on the west side that were created from crust plunging beneath the continent, driving earthquakes and volcanoes in the Andes. Whereas, on the east coast, all is relatively calm geologically, and there is a mix of old and young grains picked up from a diversity of rocks across the Amazon basin.”

Journal Reference:

  1. M.Barham et al. Understanding ancient tectonic settings through detrital zircon analysis. DOI: 10.1016/j.epsl.2022.117425
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