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A steaming cauldron follows the demise of the dinosaurs

A steaming cauldron follows the dinosaurs' downfall

Hydrothermal minerals (analcime and dachiardite) in a centimeter hole in bumps that fill the Chicxulub crater. Credit: David A. Kring

A new study reveals that the Chicxulub impact crater may have had a large and long-lived hydrothermal system following the catastrophic consequence event linked to the extinction of dinosaurs 66 million years ago.

The Chicxulub impact crater, approximately 1

80 kilometers in diameter, is the best-preserved large impact structure on earth and a target for exploring multiple impact-related phenomena. In 2016, a research team supported by the International Ocean Discovery Program and the International Continental Scientific Drilling Program drilled into the crater and reached a depth of 1,335 meters (> 1 kilometer) below the modern seabed. The team returned rock core samples that could be used to study the thermal and chemical modifications of the earth’s crust caused by the impact. The core tests show that the crater hosted an extensive hydrothermal system that chemically and mineralogically modified more than 100,000 cubic kilometers of the earth’s crust.

The lead author, Universities Space Research Association, David Kring at the Lunar and Planetary Institute (LPI), explains, “Imagine an underwater Yellowstone Caldera, but one that is several times larger and produced by the astonishing impact event that resulted in the extinction of dinosaurs.”

A steaming cauldron follows the dinosaurs' downfall

Close-up view of hydrothermal minerals (silica and feldspar) in support smelter. Credit: David A. Kring

The team found evidence that underground water floods were heated and driven upward to the boundary between the bottom of the impact crater and the bottom of the Yucatán Sea. The warm water flowed around the edges of a roughly 3-kilometer-thick pool of impact-generated magma, percolated through cracked rock and rose to the seabed where it vented into the ocean. The hot water system was particularly intense in an uplifted mountain range on the seabed, forming a ring with a diameter of 90 kilometers around the center of the crater. The rock core recovered from that top ring is crossed by fossil hydrothermal lines lined with multicolored minerals, some, appropriately enough, a fiery red-orange color. Nearly two dozen minerals precipitated from the fluids as they passed through the rock, replacing the rock’s original minerals.

The crater’s top ring consists of cracked granite-like stones that are lifted from a depth of about 10 kilometers by the impact. These stones are covered with porous and permeable residue. Both rock units are affected by the hydrothermal system. “Fluid changes were most powerful in the permeable impact residues, but garnet crystals, indicating high temperatures, were found at different levels throughout the nucleus,” explains former LPI postdoctoral fellow Martin Schmieder, who recently took up a new post at Neu-Ulm University in Germany.

Minerals identified in the new rock core indicate that the hydrothermal system was initially very hot with temperatures ranging from 300 to 400 ° C. Such high temperatures indicate that the system would have taken a long time to cool down. The team determined the cooling time with a geomagnetic polarity clock. “Our results indicate that small magnetic minerals were created in the Chicxulub crater due to chemical reactions produced by a long-lived hydrothermal system. These minerals appear to have recorded changes in the Earth’s magnetic field when formed. Their magnetic memories suggest that hydrothermal activity within the crater lasted at least 150,000 years, says co-author Sonia Tikoo of Stanford University.

  • A steaming cauldron follows the dinosaurs' downfall

    Hydrothermal minerals (silica and feldspar) in the cavity in the support melt core. Credit: ECORD-IODP Exp 364

  • A steaming cauldron follows the dinosaurs' downfall

    Portion of Expedition 364 rock core. Credit: Around @ ECORD_IODP

Further evidence of the hydrothermal system’s longevity comes from an anomalously high concentration of manganese in seabed sediment, the result of ventilation of the seabed. Co-author Axel Wittmann of Arizona State University explains, “Like the center of the ocean ridges, aeration from marine impact craters generates hydrothermal plumes containing dissolved and slowly oxidizing manganese, which compared to background concentrations produced enrichments up to ten times after post-impacting sediment below 2.1 million years on Chicxulub. “

Although the expedition just knocked on the hydrothermal system in one place, Kring says, “The results indicate that there was an approximately 300 kilometer long string of hot water valves on the top ring and additional valves scattered over the crater floor when the melt was cooled. Such hydrothermal systems may have provided habitats for microbial life. “Yellowstone’s volcanic hydrothermal systems are rich in microbial organisms and suggest that impact-generated hot water systems have the same biological potential. Kring concludes, “Our study of the expedition’s rock core from a potential deep earth’s habitat provides further evidence of the impact-origin of the life hypothesis. Life may have evolved into a crater.”

A steaming cauldron follows the dinosaurs' downfall

A three-dimensional cross-section of the hydrothermal system of the Chicxulub impact crater and its floor openings. The system has the potential to house microbial life. Credit: Victor O. Leshyk for Lunar and Planetary Institute.

The scope and longevity of the hydrothermal Chicxulub system suggests that impact-generated systems early in earth history may have provided niches for life. Thousands of these types of systems were produced during a period of impact bombings more than 3.8 billion years ago. When each system was cooled, it would have provided an environment rich in materials suitable for thermophilic and hyperthermophilic organisms.

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More information:
D.A. Kring el al., “Looking for the hydrothermal system in the impact crater Chicxulub,” Scientific progress (2020). DOI: 10.1126 / sciadv.aaz3053, advances.sciencemag.org/content/6/22/eaaz3053

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