An Archean Yellowstone? Evidence from extremely low δ18O in zircons preserved in granulites of the Yilgarn Craton, Western Australia

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Abstract

We report the discovery of Archean (2980-2670 Ma) zircons from the Yilgarn Craton in Western Australia that record unusually low δ18O signatures (to -0.5‰). These zircons occur in cordierite-orthopyroxene granulites that retain the geochemical signature of intense premetamorphic hydrothermal alteration. We propose a model whereby the low-δ18O zircons crystallized within protoliths that record multiple stages of high-temperature interaction and hydrothermal exchange between shallow crustal material and 18O-depleted meteoric fluids, in a setting analogous to that of the Yellowstone caldera. Burial and subsequent granulitefacies metamorphism of this crust led to the crystallization of zircon, which acquired and preserved the extremely 18O-depleted signature of the whole rock. The apparent absence of strongly 18O depleted Archean zircons has been a puzzling feature of the global zircon record, but we suggest this is an artifact of poor preservation potential. Our findings suggest that long-lived, shallow crustal magmatic-hydrothermal systems similar to those operating in modern caldera complexes were also a feature of Archean Earth.

Original languageEnglish
Pages (from-to)411-414
Number of pages4
JournalGeology
Volume46
Issue number5
DOIs
Publication statusPublished - 1 May 2018

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craton
Archean
zircon
caldera
cordierite
hydrothermal system
hydrothermal alteration
protolith
orthopyroxene
artifact
crystallization
metamorphism
crust
fluid
rock

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title = "An Archean Yellowstone? Evidence from extremely low δ18O in zircons preserved in granulites of the Yilgarn Craton, Western Australia",
abstract = "We report the discovery of Archean (2980-2670 Ma) zircons from the Yilgarn Craton in Western Australia that record unusually low δ18O signatures (to -0.5‰). These zircons occur in cordierite-orthopyroxene granulites that retain the geochemical signature of intense premetamorphic hydrothermal alteration. We propose a model whereby the low-δ18O zircons crystallized within protoliths that record multiple stages of high-temperature interaction and hydrothermal exchange between shallow crustal material and 18O-depleted meteoric fluids, in a setting analogous to that of the Yellowstone caldera. Burial and subsequent granulitefacies metamorphism of this crust led to the crystallization of zircon, which acquired and preserved the extremely 18O-depleted signature of the whole rock. The apparent absence of strongly 18O depleted Archean zircons has been a puzzling feature of the global zircon record, but we suggest this is an artifact of poor preservation potential. Our findings suggest that long-lived, shallow crustal magmatic-hydrothermal systems similar to those operating in modern caldera complexes were also a feature of Archean Earth.",
author = "Johannes Hammerli and Kemp, {Anthony I.S.} and Heejin Jeon",
year = "2018",
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TY - JOUR

T1 - An Archean Yellowstone? Evidence from extremely low δ18O in zircons preserved in granulites of the Yilgarn Craton, Western Australia

AU - Hammerli, Johannes

AU - Kemp, Anthony I.S.

AU - Jeon, Heejin

PY - 2018/5/1

Y1 - 2018/5/1

N2 - We report the discovery of Archean (2980-2670 Ma) zircons from the Yilgarn Craton in Western Australia that record unusually low δ18O signatures (to -0.5‰). These zircons occur in cordierite-orthopyroxene granulites that retain the geochemical signature of intense premetamorphic hydrothermal alteration. We propose a model whereby the low-δ18O zircons crystallized within protoliths that record multiple stages of high-temperature interaction and hydrothermal exchange between shallow crustal material and 18O-depleted meteoric fluids, in a setting analogous to that of the Yellowstone caldera. Burial and subsequent granulitefacies metamorphism of this crust led to the crystallization of zircon, which acquired and preserved the extremely 18O-depleted signature of the whole rock. The apparent absence of strongly 18O depleted Archean zircons has been a puzzling feature of the global zircon record, but we suggest this is an artifact of poor preservation potential. Our findings suggest that long-lived, shallow crustal magmatic-hydrothermal systems similar to those operating in modern caldera complexes were also a feature of Archean Earth.

AB - We report the discovery of Archean (2980-2670 Ma) zircons from the Yilgarn Craton in Western Australia that record unusually low δ18O signatures (to -0.5‰). These zircons occur in cordierite-orthopyroxene granulites that retain the geochemical signature of intense premetamorphic hydrothermal alteration. We propose a model whereby the low-δ18O zircons crystallized within protoliths that record multiple stages of high-temperature interaction and hydrothermal exchange between shallow crustal material and 18O-depleted meteoric fluids, in a setting analogous to that of the Yellowstone caldera. Burial and subsequent granulitefacies metamorphism of this crust led to the crystallization of zircon, which acquired and preserved the extremely 18O-depleted signature of the whole rock. The apparent absence of strongly 18O depleted Archean zircons has been a puzzling feature of the global zircon record, but we suggest this is an artifact of poor preservation potential. Our findings suggest that long-lived, shallow crustal magmatic-hydrothermal systems similar to those operating in modern caldera complexes were also a feature of Archean Earth.

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U2 - 10.1130/G39969.1

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VL - 46

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JF - Geology

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