Drill through the World's Largest Magma Chamber!

―Searching for primitive life in 2-billion-year-old rocks from the Bushveld Complex, South Africa―

  The International Continental Shelf Drilling Program (ICDP) is drilling through the Bushveld Complex in South Africa, the largest magma chamber^*1 on Earth which formed 2 billion years ago. This huge magma chamber is made up of the mantle material^*2 that penetrated the earth's crust (Photo Gallery 1). The mantle material is rarely seen on the earth's surface today, but it is thought to have existed everywhere on the earth's surface at the time when life emerged 4 billion years ago.

  The Bushveld Complex has experienced the small extents of deformation and metamorphic alteration since its formation and is considered to be a stable habitat for primitive life since then. Near the bottom of the 8-km thick Bushveld Complex, the world's largest platinum-group element deposits are layered to block the intrusion of groundwater from above (Photo Gallery 2). Thus, primitive life that intruded 2 billion years ago is expected to have survived at the very bottom of the complex.

  It has been demonstrated that subsurface microbes take 10,000 to 1,000,000 years for cell division, and that their evolution has been minimized over ~100 million years. Therefore, the purpose of this study is to clarify whether primitive microbes that started living 2 billion years ago have survived with minimal evolution over 2 billion years. If it has survived as expected, it will be possible to directly examine DNA and proteins instead of fossils, which provides critical information that will help solve the mystery of the birth of life.

  Drilling began in May 2024 at the Marula mine in Burgerfort, and as of July 15, drilling has been conducted to 600 meters. Using fluorescent beads the same size as microorganisms, Suzuki's laboratory and an international research team have successfully developed a new method to distinguish between contamination of rock core samples produced by drilling and organisms living in the rock (Photo Gallery 3).

  To examine the interior of the rock core samples, the rocks were sliced into thin sections. Proteins were detected in the veins within the rock by an infrared spectroscopy. Microscopic examination of the area also confirmed the presence of DNA within the cells (Photo Gallery 4). These results indicate that microorganisms are living in rocks 2 billion years old. Mineral analysis also revealed the presence of clay minerals^*3 in the fine veins, which contain water in their crystal structure and support microbial life in the rock.

  This achievement significantly extends the record of the oldest rocks confirmed to harbor life, from 100 million years to 2 billion years, and it is expected that even older rocks will harbor primitive life in the future. The genome is currently being analyzed to elucidate the metabolism and evolution of primitive life in 2-billion-year old rocks.

Explanation of Terms

^*1Magma chamber: Magma that has cooled and solidified deep underground without erupting into lava like a volcano.
^*2Mantle material: The mantle material is composed of heavy materials containing iron, on the top of which the crust with light materials is overlying. It contains a large amount of olivine, known as peridot, a gemstone, and is thought to have played an important role in the birth of life by reacting with water on the earth's surface.
^*3Clay mineral that contains water in its crystal structure: This mineral called smectite is believed to have played an important role in the origin of life.

Publication Information

Suzuki, Y., Webb, S. J., Kouduka, M., Kobayashi, H., Castillo, J. H., Kallmeyer, J., Moganedi, K., Allwright, A. J., Klemd, R., Roelofse, F., Mapiloko, M., Hill, S. J., Ashwal, L. D., Trumbull, R. B. (2024) Subsurface microbial colonization at mineral-filled veins in 2-billion-year-old igneous rock from the Bushveld Complex, South Africa. bioRxiv, doi: https://doi.org/10.1101/2024.07.08.602455

For Inquiries regarding research, please contact 

Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo

Associate Professor Yohei Suzuki

E-mail：yohey-suzuki(at mark)eps.s.u-tokyo.ac.jp