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The composition and weathering of the continents over geologic time
- Source :
- Geochemical Perspectives Letters. :21-26
- Publication Year :
- 2021
- Publisher :
- European Association of Geochemistry, 2021.
-
Abstract
- The composition of continental crust records the balance between construction by tectonics and destruction by physical and chemical erosion. Quantitative constraints on how igneous addition and chemical weathering have modified the continents’ bulk composition are essential for understanding the evolution of geodynamics and climate. Using novel data-analytic techniques we have extracted temporal trends in sediments’ protolith composition and weathering intensity from the largest available compilation of sedimentary major-element compositions: ∼ 15,000 samples from 4.0 Ga to the present. We find that the average Archean upper continental crust was silica rich and had a similar compositional diversity to modern continents. This is consistent with an early-Archean, or earlier, onset of plate tectonics. In the Archean, chemical weathering sequestered ∼ 25 % more CO2 per mass eroded for the same weathering intensity than in subsequent time periods, consistent with carbon mass-balance despite higher Archean outgassing rates and more limited continental exposure. Since 2.0 Ga, over long (> 0.5 Ga) timescales, crustal weathering intensity has remained relatively constant. On shorter timescales over the Phanerozoic, weathering intensity is correlated to global climate state, consistent with a weathering feedback acting in response to changes in CO2 sources or sinks.
- Subjects :
- bepress|Physical Sciences and Mathematics
Geochemistry & Geophysics
Archean
Geochemistry
bepress|Physical Sciences and Mathematics|Earth Sciences
Weathering
EarthArXiv|Physical Sciences and Mathematics|Earth Sciences
Geochemistry and Petrology
Environmental Chemistry
Science & Technology
FEEDBACK
Continental crust
37 Earth Sciences
PLATE-TECTONICS
Geology
EarthArXiv|Physical Sciences and Mathematics|Earth Sciences|Geochemistry
Geodynamics
EarthArXiv|Physical Sciences and Mathematics
3703 Geochemistry
Tectonics
Igneous rock
Physical Sciences
Earth Sciences
bepress|Physical Sciences and Mathematics|Earth Sciences|Geochemistry
Sedimentary rock
CRUST
Protolith
Subjects
Details
- ISSN :
- 24103403 and 2410339X
- Database :
- OpenAIRE
- Journal :
- Geochemical Perspectives Letters
- Accession number :
- edsair.doi.dedup.....a5b098da4e073a2af43e583ff2a2f538