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Metallic Pb nanospheres in ultra-high temperature metamorphosed zircon from southern India

Metallic Pb nanospheres in ultra-high temperature metamorphosed zircon from southern India A transmission electron microscope (TEM) study of Paleoproterozoic zircon that has experienced ultra-high temperature (UHT) metamorphism at ca. 570 Ma in the Kerala Khondalite Belt (KKB), southern India, documents the occurrence of metallic Pb nanospheres. These results permit comparison with a previous report from UHT zircon in Enderby Land, Antarctica, and allow further constraints to be placed on possible mechanisms for nanosphere formation. As in Enderby Land, the nanospheres in the KKB occur in non-metamict zircon, emphasising that radiogenic Pb redistribution can occur with only partial interconnectivity of radiation damaged zircon. In contrast, the nanospheres reported here are not closely associated with Si-rich glass inclusions, which is inconsistent with a silicate liquid-metal immiscibility model proposed in the earlier study. Formation of these Pb nanospheres effectively halts Pb-loss from zircon, even under extreme conditions, and can adversely affect geochronological interpretations due to decoupling of Pb from U. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Mineralogy and Petrology Springer Journals

Metallic Pb nanospheres in ultra-high temperature metamorphosed zircon from southern India

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References (41)

Publisher
Springer Journals
Copyright
Copyright © 2017 by The Author(s)
Subject
Earth Sciences; Mineralogy; Inorganic Chemistry; Geochemistry
ISSN
0930-0708
eISSN
1438-1168
DOI
10.1007/s00710-017-0523-1
Publisher site
See Article on Publisher Site

Abstract

A transmission electron microscope (TEM) study of Paleoproterozoic zircon that has experienced ultra-high temperature (UHT) metamorphism at ca. 570 Ma in the Kerala Khondalite Belt (KKB), southern India, documents the occurrence of metallic Pb nanospheres. These results permit comparison with a previous report from UHT zircon in Enderby Land, Antarctica, and allow further constraints to be placed on possible mechanisms for nanosphere formation. As in Enderby Land, the nanospheres in the KKB occur in non-metamict zircon, emphasising that radiogenic Pb redistribution can occur with only partial interconnectivity of radiation damaged zircon. In contrast, the nanospheres reported here are not closely associated with Si-rich glass inclusions, which is inconsistent with a silicate liquid-metal immiscibility model proposed in the earlier study. Formation of these Pb nanospheres effectively halts Pb-loss from zircon, even under extreme conditions, and can adversely affect geochronological interpretations due to decoupling of Pb from U.

Journal

Mineralogy and PetrologySpringer Journals

Published: Jul 1, 2017

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