New insights into early Earth's crust evolution and phosphorus availability from zircon-melt partitioning experiments

A breakthrough study from a team of scientists led by Dr. Yanhao Lin from HPSTAR in collaboration with Vrije Universiteit Amsterdam have shed new light on the evolution of Earth's early crust and the availability of phosphorus—an essential element for life. They have conducted high-temperature experiments to constrain the partition coefficients of Al (DAl) and P (DP) between zircon and silicate melt, and found that the amounts of P have the identifiable effects on DAl, but not on itself. The positive correlation of DAl with P content in zircon enables to constrain the aluminum saturation index (ASI) of the parental magma of natural zircon. The re-evaluated ASI values over time yields two significant increases at 3.6 Ga and 1.0 Ga, whereas, the calculated magma P abundances are uniform (∼1900 ± 400 ppm) throughout Earth history. These indicate that the global scale tectonic events occurred on the Earth around 3.6 Ga and 1.0 Ga, and that the early Earth could have had a life habitability. This work published in Geology provides a new perspective for our understanding of the evolution of early Earth's crust.
 

Caption: Evolution of aluminum saturation index (ASI) and phosphorus content in the Earth's crust.

Phosphorus, a critical component of genetic material and energy conversion within living organisms, has long been a subject of interest for scientists studying the origins of life. Aluminum, another key element in the crust, plays a significant role in understanding the formation and evolution of the Earth's crust. The research team conducted zircon-melt partitioning experiments to quantitatively assess the impact of phosphorus content on the partitioning of elements between zircon and melt, particularly focusing on aluminum and phosphorus.

The experimental results revealed a significant correlation between phosphorus content and the partition coefficients of aluminum and lithium in zircon-melt systems. Notably, the aluminum saturation index (ASI) of early Earth's magmas, as inferred from the study, was consistently below 1, indicating the predominance of aluminum-poor granitic compositions in the early crust. Only around 3.6 billion years ago did peraluminous melts with ASI values exceeding 1 emerge, potentially correlating with a tectonic shift from vertical to horizontal movements.

The study also found that the phosphorus content of the early crust was comparable to that of the modern crust, suggesting that the necessary conditions for the emergence and evolution of life were already in place during the early stages of Earth's history. The findings provide valuable information for assessing the geochemical conditions required for the origin and evolution of life.

早期地壳的演化过程一直是地球科学研究领域的一个热点课题。最近，北京高压科学研究中心林彦蒿课题组的最新研究为我们理解地球早期地壳的组成和宜居性提供了重要启示。通过锆石-熔体的分配实验，该研究小组定量评估了磷含量对锆石与熔体之间元素分配的影响，并结合天然锆石的数据，证明了早期地球岩浆是贫铝的，且磷含量与现代地壳相近。相关研究以“Evolution of magma compositions and phosphorus availability in early Earth's crust: new constraints from zircon-melt partitioning experiments”为题，发表在国际地学期刊《Geology》，第一作者为北京高压科学研究中心博士后尚升博士。