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Researchers identify first 'ghost plume' mantle column beneath Oman with no surface volcanism

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Discovery of a 'Ghost Plume' Beneath Eastern Oman

A new study published in the journal Earth and Planetary Science Letters reports the identification of a unique mantle plume beneath eastern Oman. This feature, named the Dani plume, is described as the first known 'ghost plume,' characterized by a complete lack of associated surface volcanism. The research was led by Simone Pilia of King Fahd University of Petroleum and Minerals.

This discovery suggests that mantle plumes can significantly influence tectonics and topography without ever producing surface volcanism.

Detection and Characteristics

The plume was detected using seismic tomography, a method that analyzes thousands of earthquake signals to image structures deep within the Earth.

  • Structure: Seismic wave speeds slowed within a cylindrical structure approximately 125 miles (200 kilometers) wide, extending to a depth of at least 410 miles (660 kilometers).
  • Temperature: Data indicated a temperature increase of roughly 200–500 °F (93–260 °C) within the column. This is sufficient to soften rock but not melt it under the thick continental lithosphere.
  • Key Evidence: The mantle transition zone was observed to warp downward at 255 miles (410 km) and lift again at 410 miles (660 km)—a pattern strongly associated with rising hot material.

Surface Effects and Geological Context

Despite the absence of volcanic activity, the plume's influence is visible at the surface.

  • Elevation: The Salma Plateau in eastern Oman is elevated over 6,500 feet (1,980 meters).
  • Uplift: GPS and shoreline data indicate the coast is rising at a rate under 0.04 inches (0.1 cm) per year. The study attributes this to dynamic support from the buoyant mantle plume below.
  • Tectonic History: The researchers propose the plume interacted with the Indian Plate around 40 million years ago. They suggest it may have contributed to an eastward bend in India's tectonic path through viscous drag.

Implications and Broader Context

The identification of the Dani plume has significant implications for our understanding of Earth's interior and its surface expression.

  • New Understanding of Plumes: The discovery challenges the traditional view that mantle plumes must produce volcanism. It shows they can act as hidden forces shaping the landscape.
  • Detection Methods: It implies that traditional detection methods relying on volcanic evidence may overlook significant subsurface features.
  • Global Connections: The study notes the Dani plume may be connected to a broader low-velocity structure at the core-mantle boundary, possibly linking it to other major plumes like the Afar plume under Africa.

Researcher Saskia Goes of Imperial College London, who was not involved in the study, reviewed the data and described the detection as plausible.