Widespread Archean basement beneath the Yangtze craton
- Jianping Zheng1,
- W.L. Griffin2,
- Suzanne Y. O'Reilly3,
- Ming Zhang3,
- Norman Pearson3 and
- Yuanming Pan4
- 1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China, and GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia
- 2GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia, and CSIRO Exploration and Mining, North Ryde, NSW 2113, Australia
- 3GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia
- 4Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
Abstract
The age distribution of the crust is a fundamental parameter in modeling continental evolution and the rate of crustal accretion through Earth's history, but this is usually estimated from surface exposures. The exposed Yangtze craton in eastern China consists mainly of Proterozoic rocks with rare Archean outcrops. However, the U-Pb ages and Hf isotope systematics of xenocrystic zircons brought to the surface in lamproite diatremes from three Proterozoic outcrop areas of the craton suggest the widespread presence of unexposed Archean basement, with zircon age populations of 2900–2800 Ma and 2600– 2500 Ma and Hf model ages of 2.6 to ca. 3.5 Ga or older. The zircons also record thermal events reworked on the craton ca. 2020 Ma (remelting of older crust) and 1000–850 Ma (addition of juvenile mantle material). The observation of deep crust significantly older than the upper crust will require revision of models for the rates of crustal generation through time.
- crustal evolution
- Hf isotopes
- zircon geochronology
- deep-crustal xenocryst
- Archean basement
- Yangtze craton
- east China
Footnotes
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↵GSA Data Repository item 2006082, U-Pb dating and Hf-isotope analyses of zircons, is available online at www.geosociety.org/pubs/ft2006.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Accepted 28 December 2005.
- Received 7 October 2005.
- Revision received 23 December 2005.
- The Geological Society of America, Inc.
