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Conference Papers Year : 2009

Silicium isotopes as a proxy of weathering processes during the PETM

Abstract

The end of the Paleocene epoch (55.5 Ma) was marked by an abrupt episode of global warming ("Palaeocene/Eocene Thermal Maximum"; PETM) coincident with a large perturbation to the global carbon cycle. Because the PETM might represent an analogue in the past of the present anthropogenic accelerated emission of greenhouse gases, it has attracted a good deal of interest with both data collecting and modeling efforts. Most of the studies focused on ocean records through sediments, we propose here one of the first study on continental records during the PETM. We focus our study on silcretes sampled in north of France, rocks present on the Paleocene-Eocene boundary and on the silicification formed in the porosity during weathering processes. Stable isotopes of Si have been used as proxies for understanding the Si cycle and its variations in the past. Here we analyzed silicon isotopes of in situ quartz using a new generation secondary ion mass spectrometry apparatus. Secondary phases as overgrowths on primary detrital quartz and microcrystals of quartz have been measured. Our results are very unexpected : althought detrital quartz present same values than in other silcretes, secondary phases present very homogenuous signatures far from very negative values that can be reached (-8 ‰ in [1, 2]). It seems that the origin of silicium is not local as both primary and secondary phases are within the same range. The isotopic fractionnation link to the dissolution/precipitation phase during weathering processes is 1.5 ‰. The lack of a strongly 30Si-depleted reservoir with negative isotopic values seem to show a low intenisity of alteration during the PETM in continental context. [1] Basile-Doelsch et al.(2005) Nature 433, 399–402. [2] Basile-Doelsch (2006) Journal of Geochemical Exploration 88, 252-256.

Domains

Earth Sciences
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Dates and versions

hal-00740723 , version 1 (10-10-2012)

Identifiers

  • HAL Id : hal-00740723 , version 1

Cite

Setareh Rad, Isabelle Basile-Doelsch, Florence Quesnel, Christian Dupuis. Silicium isotopes as a proxy of weathering processes during the PETM. Goldschmidt Conference 2009 : CXhallenges to our volatile planet, Jun 2009, Davos, Switzerland. pp.A1066. ⟨hal-00740723⟩
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