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Archean, highly unradiogenic lead in shallow cratonic mantle

Zhang Junbo, Liu Yongsheng, Mihai N. Ducea and Xu Rong
Archean, highly unradiogenic lead in shallow cratonic mantle
Geology (Boulder) (March 2020) Pre-Issue Publication

Abstract

Here, we present coupled geochemical and Sr-Nd-Pb-S isotopic data of Early Cretaceous primitive gabbros from the North China craton. Strikingly, these rocks have highly unradiogenic lead compositions ( (super 206) Pb/ (super 204) Pb=16.58+ or -0.24) and anchor one extreme end member (low (super 206) Pb/ (super 204) Pb and (super 143) Nd/ (super 144) Nd) in the global array of oceanic-island volcanics. Our study shows that they originated from an Archean fluid-metasomatized refractory peridotite source, in which highly unradiogenic lead was preferentially released with subducted Archean seawater and sequestered into recrystallized sulfides at shallow mantle depths. Sulfide/silicate partition coefficients for lead show a negative pressure dependence: Lead is more enriched in sulfide with decreasing pressure. Sulfide-bearing and iron-poor harzburgite as well as dunite residues at shallow mantle are expected to develop low U/Pb (and thereby low time-integrated (super 206) Pb/ (super 204) Pb) relative to a deeper upper-mantle source. Our preferred interpretation is that an Archean, highly unradiogenic lead reservoir may be stored in the spinel-facies refractory cratonic mantle.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: Pre-Issue Publication
Title: Archean, highly unradiogenic lead in shallow cratonic mantle
Affiliation: China University of Geosciences-Wuhan, School of Earth Sciences, Laboratory of Geological Processes and Mineral Resources, Wuhan, China
Published: 20200327
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 41
Accession Number: 2020-030429
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2020172
Illustration Description: illus. incl. geol. sketch maps
N34°00'00" - N38°00'00", E116°00'00" - E120°00'00"
Secondary Affiliation: University of Arizona, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 2020
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