Zircon Thermometer Reveals Minimum Melting conditions on Earliest Earth
Date
2005
Authors
Watson, E B
Harrison, Timothy
Journal Title
Journal ISSN
Volume Title
Publisher
American Association for the Advancement of Science
Abstract
Ancient zircons from Western Australia's Jack Hills preserve a record of conditions that prevailed on Earth not long after its formation. Widely considered to have been a uniquely violent period geodynamically, the Hadean Eon [4.5 to 4.0 billion years ago (Ga)] has recently been interpreted by some as far more benign - possibly even characterized by oceans like those of the present day. Knowledge of the crystallization temperatures of the Hadean zircons is key to this debate. A thermometer based on titanium content revealed that these zircons cluster strongly at ∼700°C, which is indistinguishable from temperatures of granitoid zircon growth today and strongly suggests a regulated mechanism producing zircon-bearing rocks during the Hadean. The temperatures substantiate the existence of wet, minimum-melting conditions within 200 million years of solar system formation. They further suggest that Earth had settled into a pattern of crust formation, erosion, and sediment recycling as early as 4.35 Ga.
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Keywords
Keywords: Crystallization; Earth (planet); Erosion; Melting; Sediments; Solar system; Thermometers; Titanium; Geodynamics; Hadean zircons; Sediment recycling; Zircon thermometers; Zircon; titanium; zirconium; Archean; geothermometry; planetary evolution; zircon; ar
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Source
Science
Type
Journal article