A thin slice of ancient rock collected from Gakkel Ridge near the North Pole (IMAGE)
Caption
A thin slice of the ancient rocks collected from Gakkel Ridge near the North Pole, photographed under a microscope and seen under cross-polarized light. Field width ~ 14mm.
Analyzing rocks in thin section helps geologists identify and characterize minerals within a rock. The analyses reveal information about the rock’s mineral composition, texture and history, such as how it formed and any subsequent changes it has undergone. Researchers use the identification and chemical composition of the minerals in these ancient rocks from Earth’s mantle to determine the conditions under which these rocks melted.
A new analysis of rocks thought to be at least 2.5 billion years old by researchers at the Smithsonian’s National Museum of Natural History helps clarify the chemical history of Earth’s mantle—the geologic layer beneath the planet’s crust. The study, published today in the journal Nature, centered on a group of rocks collected from the seafloor that possessed unusual geochemical properties.
Credit
E. Cottrell, Smithsonian.
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