K-rich mantle metasomatism control of localization and initiation of lithospheric strike-slip faulting
✍ Scribed by Alan P. M. Vaughan; Jane H. Scarrow
- Book ID
- 104463420
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 305 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0954-4879
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✦ Synopsis
ABSTRACT A conceptual model is proposed in which bulk transtension, or local transtension during bulk simple shear (resulting from mantle anisotropy contrasts or lithosphere rheology contrasts), of heterogeneously enriched lithospheric mantle, triggers localized K‐rich magmatism, which focuses strain and causes nucleation of lithosphere‐scale transtensional or strike‐slip shear zones. Transtension‐triggered magmatism is most likely to be located at sites of maximum metasomatism of the lithospheric mantle. Magma‐generated fractures propagate upwards, nucleating zones of lithospheric weakness, which focus shear in narrow transcurrent faults or at basin margins. In this way, magmatism controls fault timing and location. Although volcanism will be coeval with fault development and volcanoes will appear fault‐controlled, counterintuitively, our model suggests that faults are, in a sense, volcano‐controlled. We suggest that this new transtension – K‐rich magmatism – transcurrent faulting association represents a hitherto unrecognized genetic relationship as significant as, for example, the ocean island magma series.