New high-pressure and high-temperature metal/silicate partitioning of U and Pb: Implications for the cores of the Earth and Mars
In order to quantify possible fractionation of U and Pb into a metallic core, we have performed piston cylinder and multi-anvil press experiments at high pressure (up to 20 GPa) and high temperature (up to 2400 °C) and obtained the distribution coefficient D metal–silicate and the exchange partition...
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| Veröffentlicht in: | Geochimica et cosmochimica acta 2007-05, Vol.71 (10), p.2637-2655 |
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| creator | Malavergne, Valérie Tarrida, Martine Combes, Rossana Bureau, Hélène Jones, John Schwandt, Craig |
| description | In order to quantify possible fractionation of U and Pb into a metallic core, we have performed piston cylinder and multi-anvil press experiments at high pressure (up to 20
GPa) and high temperature (up to 2400
°C) and obtained the distribution coefficient
D
metal–silicate and the exchange partition coefficient
K
metal–silicate for these elements between metal and silicates (mineral or liquid).
D
Pb
metal–silicate
and
D
U
metal–silicate
depend strongly on the S content of the metallic phase, and also on the oxygen fugacity, in agreement with an effective valence state of 4 for U in silicates and 2 for Pb in silicates.
K
Pb
d metal–silicate
and
K
U
d metal–silicate
show no discernable pressure and temperature trend. U remains lithophile even at high pressure and high temperature but its lithophile nature decreases at very low oxygen fugacity. From our experimental data, it was possible to calculate the U and Pb contents of the cores of Mars and Earth under core-mantle equilibrium conditions at high pressure and high temperature. From the
D
metal–silicate of the present study, we obtained that: 0.008
ppm
<
Pb
in
the
core |
| doi_str_mv | 10.1016/j.gca.2007.03.011 |
| format | Article |
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GPa) and high temperature (up to 2400
°C) and obtained the distribution coefficient
D
metal–silicate and the exchange partition coefficient
K
metal–silicate for these elements between metal and silicates (mineral or liquid).
D
Pb
metal–silicate
and
D
U
metal–silicate
depend strongly on the S content of the metallic phase, and also on the oxygen fugacity, in agreement with an effective valence state of 4 for U in silicates and 2 for Pb in silicates.
K
Pb
d metal–silicate
and
K
U
d metal–silicate
show no discernable pressure and temperature trend. U remains lithophile even at high pressure and high temperature but its lithophile nature decreases at very low oxygen fugacity. From our experimental data, it was possible to calculate the U and Pb contents of the cores of Mars and Earth under core-mantle equilibrium conditions at high pressure and high temperature. From the
D
metal–silicate of the present study, we obtained that: 0.008
ppm
<
Pb
in
the
core
<4.4
ppm, and 0.0003
ppb
<
U
in
the
core
<
0.63
ppb, depending on whether the metal is S-free or S-saturated respectively, and if the mantle was molten or solid during the segregation process of the Earth’s core around ΔIW-2. For Mars, based on a core segregation process around ΔIW-1, we obtained that: 0.005
ppm
<
Pb
in
the
core
<
3
ppm, and 0.00002
ppb
<
U
in
the
core
<
0.05
ppb, depending on the metallic composition: S-free or S-saturated respectively.
Our results suggest that the low concentration of Pb in the terrestrial mantle could not be explained by an early Pb sequestration in the Earth’s core even if S is the dominant light element of the core. If we assume a magma ocean scenario, U might produced a maximum value of 1.5% of the total heat budget of the core with a segregation occurring below ΔIW-3. The values found in the present study for U in the Martian core suggest that the magnetic field activity of Mars before ∼0.5
b.y. after its formation would be difficult to ascribe to the decay of U alone.]]></description><identifier>ISSN: 0016-7037</identifier><identifier>EISSN: 1872-9533</identifier><identifier>DOI: 10.1016/j.gca.2007.03.011</identifier><language>eng</language><publisher>Elsevier Ltd</publisher><ispartof>Geochimica et cosmochimica acta, 2007-05, Vol.71 (10), p.2637-2655</ispartof><rights>2007 Elsevier Ltd</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-a417t-3c6cbe216e0e144c825231cc661d7b3fb6c0bd691a5d402ae1bd9781aba1e66b3</citedby><cites>FETCH-LOGICAL-a417t-3c6cbe216e0e144c825231cc661d7b3fb6c0bd691a5d402ae1bd9781aba1e66b3</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://www.sciencedirect.com/science/article/pii/S0016703707001433$$EHTML$$P50$$Gelsevier$$H</linktohtml><link.rule.ids>314,776,780,3537,27901,27902,65306</link.rule.ids></links><search><creatorcontrib>Malavergne, Valérie</creatorcontrib><creatorcontrib>Tarrida, Martine</creatorcontrib><creatorcontrib>Combes, Rossana</creatorcontrib><creatorcontrib>Bureau, Hélène</creatorcontrib><creatorcontrib>Jones, John</creatorcontrib><creatorcontrib>Schwandt, Craig</creatorcontrib><title>New high-pressure and high-temperature metal/silicate partitioning of U and Pb: Implications for the cores of the Earth and Mars</title><title>Geochimica et cosmochimica acta</title><description><![CDATA[In order to quantify possible fractionation of U and Pb into a metallic core, we have performed piston cylinder and multi-anvil press experiments at high pressure (up to 20
GPa) and high temperature (up to 2400
°C) and obtained the distribution coefficient
D
metal–silicate and the exchange partition coefficient
K
metal–silicate for these elements between metal and silicates (mineral or liquid).
D
Pb
metal–silicate
and
D
U
metal–silicate
depend strongly on the S content of the metallic phase, and also on the oxygen fugacity, in agreement with an effective valence state of 4 for U in silicates and 2 for Pb in silicates.
K
Pb
d metal–silicate
and
K
U
d metal–silicate
show no discernable pressure and temperature trend. U remains lithophile even at high pressure and high temperature but its lithophile nature decreases at very low oxygen fugacity. From our experimental data, it was possible to calculate the U and Pb contents of the cores of Mars and Earth under core-mantle equilibrium conditions at high pressure and high temperature. From the
D
metal–silicate of the present study, we obtained that: 0.008
ppm
<
Pb
in
the
core
<4.4
ppm, and 0.0003
ppb
<
U
in
the
core
<
0.63
ppb, depending on whether the metal is S-free or S-saturated respectively, and if the mantle was molten or solid during the segregation process of the Earth’s core around ΔIW-2. For Mars, based on a core segregation process around ΔIW-1, we obtained that: 0.005
ppm
<
Pb
in
the
core
<
3
ppm, and 0.00002
ppb
<
U
in
the
core
<
0.05
ppb, depending on the metallic composition: S-free or S-saturated respectively.
Our results suggest that the low concentration of Pb in the terrestrial mantle could not be explained by an early Pb sequestration in the Earth’s core even if S is the dominant light element of the core. If we assume a magma ocean scenario, U might produced a maximum value of 1.5% of the total heat budget of the core with a segregation occurring below ΔIW-3. The values found in the present study for U in the Martian core suggest that the magnetic field activity of Mars before ∼0.5
b.y. after its formation would be difficult to ascribe to the decay of U alone.]]></description><issn>0016-7037</issn><issn>1872-9533</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2007</creationdate><recordtype>article</recordtype><recordid>eNp9kEtP6zAQRi10kegt_AB2Xt1dwkycOC13hRAvidcC1pbjTFpXeWG7IHb8dJyWNavRzJwz0nyMnSKkCCjPNunK6DQDKFMQKSAesBkuyixZFkL8YTOIUFKCKI_YX-83EMGigBn7eqQPvrardTI68n7riOu-3k8CdSM5HaZhR0G3Z9621uhAfNQu2GCH3vYrPjT8dWc9V-f8rht3TNx53gyOhzVxM8TjEzc1V9Fd7_gH7fwxO2x06-nkp87Z6_XVy-Vtcv90c3d5cZ_oHMuQCCNNRRlKAsI8N4usyAQaIyXWZSWaShqoarlEXdQ5ZJqwqpflAnWlkaSsxJz9298d3fC2JR9UZ72httU9DVuvMhAyxwVEEPegcYP3jho1Ottp96kQ1JS12qiYtZqyViBUzDo6__cOxQ_eLTnljaXeUG0dmaDqwf5ifwO0XIhx</recordid><startdate>20070515</startdate><enddate>20070515</enddate><creator>Malavergne, Valérie</creator><creator>Tarrida, Martine</creator><creator>Combes, Rossana</creator><creator>Bureau, Hélène</creator><creator>Jones, John</creator><creator>Schwandt, Craig</creator><general>Elsevier Ltd</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>F1W</scope><scope>H96</scope><scope>KL.</scope><scope>L.G</scope></search><sort><creationdate>20070515</creationdate><title>New high-pressure and high-temperature metal/silicate partitioning of U and Pb: Implications for the cores of the Earth and Mars</title><author>Malavergne, Valérie ; Tarrida, Martine ; Combes, Rossana ; Bureau, Hélène ; Jones, John ; Schwandt, Craig</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a417t-3c6cbe216e0e144c825231cc661d7b3fb6c0bd691a5d402ae1bd9781aba1e66b3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2007</creationdate><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Malavergne, Valérie</creatorcontrib><creatorcontrib>Tarrida, Martine</creatorcontrib><creatorcontrib>Combes, Rossana</creatorcontrib><creatorcontrib>Bureau, Hélène</creatorcontrib><creatorcontrib>Jones, John</creatorcontrib><creatorcontrib>Schwandt, Craig</creatorcontrib><collection>CrossRef</collection><collection>Meteorological & Geoastrophysical Abstracts</collection><collection>ASFA: Aquatic Sciences and Fisheries Abstracts</collection><collection>Aquatic Science & Fisheries Abstracts (ASFA) 2: Ocean Technology, Policy & Non-Living Resources</collection><collection>Meteorological & Geoastrophysical Abstracts - Academic</collection><collection>Aquatic Science & Fisheries Abstracts (ASFA) Professional</collection><jtitle>Geochimica et cosmochimica acta</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Malavergne, Valérie</au><au>Tarrida, Martine</au><au>Combes, Rossana</au><au>Bureau, Hélène</au><au>Jones, John</au><au>Schwandt, Craig</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>New high-pressure and high-temperature metal/silicate partitioning of U and Pb: Implications for the cores of the Earth and Mars</atitle><jtitle>Geochimica et cosmochimica acta</jtitle><date>2007-05-15</date><risdate>2007</risdate><volume>71</volume><issue>10</issue><spage>2637</spage><epage>2655</epage><pages>2637-2655</pages><issn>0016-7037</issn><eissn>1872-9533</eissn><abstract><![CDATA[In order to quantify possible fractionation of U and Pb into a metallic core, we have performed piston cylinder and multi-anvil press experiments at high pressure (up to 20
GPa) and high temperature (up to 2400
°C) and obtained the distribution coefficient
D
metal–silicate and the exchange partition coefficient
K
metal–silicate for these elements between metal and silicates (mineral or liquid).
D
Pb
metal–silicate
and
D
U
metal–silicate
depend strongly on the S content of the metallic phase, and also on the oxygen fugacity, in agreement with an effective valence state of 4 for U in silicates and 2 for Pb in silicates.
K
Pb
d metal–silicate
and
K
U
d metal–silicate
show no discernable pressure and temperature trend. U remains lithophile even at high pressure and high temperature but its lithophile nature decreases at very low oxygen fugacity. From our experimental data, it was possible to calculate the U and Pb contents of the cores of Mars and Earth under core-mantle equilibrium conditions at high pressure and high temperature. From the
D
metal–silicate of the present study, we obtained that: 0.008
ppm
<
Pb
in
the
core
<4.4
ppm, and 0.0003
ppb
<
U
in
the
core
<
0.63
ppb, depending on whether the metal is S-free or S-saturated respectively, and if the mantle was molten or solid during the segregation process of the Earth’s core around ΔIW-2. For Mars, based on a core segregation process around ΔIW-1, we obtained that: 0.005
ppm
<
Pb
in
the
core
<
3
ppm, and 0.00002
ppb
<
U
in
the
core
<
0.05
ppb, depending on the metallic composition: S-free or S-saturated respectively.
Our results suggest that the low concentration of Pb in the terrestrial mantle could not be explained by an early Pb sequestration in the Earth’s core even if S is the dominant light element of the core. If we assume a magma ocean scenario, U might produced a maximum value of 1.5% of the total heat budget of the core with a segregation occurring below ΔIW-3. The values found in the present study for U in the Martian core suggest that the magnetic field activity of Mars before ∼0.5
b.y. after its formation would be difficult to ascribe to the decay of U alone.]]></abstract><pub>Elsevier Ltd</pub><doi>10.1016/j.gca.2007.03.011</doi><tpages>19</tpages></addata></record> |
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| source | Elsevier ScienceDirect Journals Complete |
| title | New high-pressure and high-temperature metal/silicate partitioning of U and Pb: Implications for the cores of the Earth and Mars |
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