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Cenozoic delamination of the southwestern Yangtze craton owing to densification during subduction and collision.
- Source :
-
Geology . Aug2022, Vol. 50 Issue 8, p912-917. 6p. - Publication Year :
- 2022
-
Abstract
- It is widely thought that oceanic subduction can trigger cratonic keel delamination, but the southwestern Yangtze craton (SYC; southwestern China) lost its lower keel during Cenozoic continental collision. The upper mantle beneath the thinned SYC contains its incompletely delaminated keel, which has high-velocity seismic anomalies. Combining geophysical observations with the geochemistry of Eocene mafic potassic lavas derived from the SYC mantle at different depths, we suggest that the deep (~130 km) delaminated lithosphere was more fertile and dense, with low-forsterite (Fo; molar 100 × Mg/[Mg + Fe] = 91.3) and high-δ18O (5.9‰) olivine, than the shallow (~55 km) intact lithosphere (Fo = 94.2; δ18O = 5.2‰), although both were rehydrated and oxidized. The deep keel underwent strong refertilization and densification owing to the addition of Fe-rich basaltic melts during earlier oceanic subduction. Subduction-driven refertilization and subsequent collision-driven cooling caused cratonic keel delamination due to compositional and thermal densification rather than hydration- or oxidation-induced rheological weakening. Our study provides an example of Cenozoic cratonic keel delamination in a collisional orogen and highlights the key roles of compositional and thermal densification in delamination during subduction and collision. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00917613
- Volume :
- 50
- Issue :
- 8
- Database :
- Academic Search Index
- Journal :
- Geology
- Publication Type :
- Academic Journal
- Accession number :
- 161490344
- Full Text :
- https://doi.org/10.1130/G49732.1