Study sheds light on Earth's early mantle

May 06, 2013
Credit: NASA

(Phys.org) —An international team of researchers, led by scientists at Boston University's Department of Earth and Environment, has found evidence that material contained in young oceanic lava flows originated at the Earth's surface in the Archean (>2.45 billions years ago). The new finding helps constrain the timing of the initiation of plate tectonics, the origin of some of the chemical heterogeneity in the Earth's mantle, and may shed light on how the chaotically convecting mantle could preserve such material for so long.

The study appears in the April 25 issue of the journal Nature.

Tectonic plates at the Earth's surface move around and collide at areas called subduction zones. In these areas, one plate is forced beneath the other and is transported into the Earth's mantle. It has long been suggested that this subducted material must be re-erupted at a later time. However, the residence time of the subducted material in the mantle is uncertain and convincing evidence of its return to the surface has been lacking.

Sulfur provide the key to the authors' discovery. According to the researchers, because mass-independently fractionated (MIF) sulfur isotope signatures were generated exclusively through atmospheric until about 2.5 billion years ago, material containing such isotope signatures must have originated at the Earth's surface in the Archean. In the new study, the researchers found MIF sulfur-isotope signatures in olivine-hosted sulfides from relatively young (20-million-year-old) ocean island basalts (OIB) from Mangaia, Cook Islands (Polynesia), providing evidence that material once at the Earth's surface has been recycled through the mantle and re-erupted at a young ocean island.

"The discovery of MIF-S isotope in these young oceanic lavas suggests that sulfur—likely derived from the hydrothermally-altered oceanic crust—was subducted into the mantle more than 2.5 billion years ago and recycled into the mantle source of the Mangaia lavas," says Cabral.

The data also complement evidence for recycling of ancient sedimentary materials to the subcontinental lithospheric mantle previously identified in diamond inclusions.

Explore further: TRMM satellite sees Tropical Storm Phanfone fragmented

More information: doi:10.1038/nature12020

Related Stories

Ancient Earth crust stored in deep mantle

Apr 24, 2013

Scientists have long believed that lava erupted from certain oceanic volcanoes contains materials from the early Earth's crust. But decisive evidence for this phenomenon has proven elusive. New research from ...

Diamonds show depth extent of Earth's carbon cycle

Sep 15, 2011

Scientists have speculated for some time that the Earth's carbon cycle extends deep into the planet's interior, but until now there has been no direct evidence. The mantle–Earth's thickest layer –is ...

Volcanoes deliver two flavors of water

Feb 26, 2012

Seawater circulation pumps hydrogen and boron into the oceanic plates that make up the seafloor, and some of this seawater remains trapped as the plates descend into the mantle at areas called subduction zones. ...

Studying ancient Earth's geochemistry

Jan 18, 2013

Researchers still have much to learn about the volcanism that shaped our planet's early history. New evidence from a team led by Carnegie's Frances Jenner demonstrates that some of the tectonic processes driving volcanic ...

Deep recycling in the Earth faster than thought

Aug 10, 2011

The recycling of the Earth's crust in volcanoes happens much faster than scientists have previously assumed. Rock of the oceanic crust, which sinks deep into the earth due to the movement of tectonic plates, ...

Recommended for you

Tropical Storm Rachel dwarfed by developing system 90E

2 hours ago

Tropical Storm Rachel is spinning down west of Mexico's Baja California, and another tropical low pressure area developing off the coast of southwestern Mexico dwarfs the tropical storm. NOAA's GOES-West ...

NASA ocean data shows 'climate dance' of plankton

5 hours ago

The greens and blues of the ocean color from NASA satellite data have provided new insights into how climate and ecosystem processes affect the growth cycles of phytoplankton—microscopic aquatic plants ...

Glaciers in the grand canyon of Mars?

7 hours ago

For decades, planetary geologists have speculated that glaciers might once have crept through Valles Marineris, the 2000-mile-long chasm that constitutes the Grand Canyon of Mars. Using satellite images, ...

NASA support key to glacier mapping efforts

7 hours ago

Thanks in part to support from NASA and the National Science Foundation, scientists have produced the first-ever detailed maps of bedrock beneath glaciers in Greenland and Antarctica. This new data will help ...

User comments : 0