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Spatial distribution of magmatic activity

Structural control of igneous complexes and kimberlites : a new statistical method Dazheng Zhang and Lutz, T., 1989. . Spatial distribution of magmatic activity. transport through the lithosphere mechanical properties of the lithosphere zones of weakness

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Spatial distribution of magmatic activity

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  1. Structural control of igneous complexes and kimberlites: a new statistical method Dazheng Zhang and Lutz, T., 1989.

  2. Spatial distribution of magmatic activity • transport through the lithosphere • mechanical properties of the lithosphere • zones of weakness • associated with deep crustal fractures • linear outcrop patterns

  3. Monte Carlo simulations • null model • anisotropies • evaluated on a statistical basis

  4. Geologic point features • earthquake epicenters • kimberlites • igneous complexes • distribution random • controlled by geologic structures

  5. Magma transport control • pre-existing zones of weakness • stress fields during ascent • epeirogenic faults • transform fault extensions

  6. Anisotropic point feature distribution • Chapman (1968) alkaline igneous complexes • lattice nodal points • intersecting sets of crustal fractures • grid lines could be constructed • complexes located at nodal positions • Thompson and Hager (1979) • intuitive perceptions

  7. Lutz (1986) Monte Carlo simulations • line azimuth method • spatial anisotropy • shape of the region • azimuths of lines

  8. Filtering method (Strip method) • convex bounding polygon • parallel strips • equal number of strips • width of the strips • areal point density • vary the orientation

  9. Filtering method continued • limiting value arbitrary • false positive • false negative • signal to noise ratio

  10. Comparison of methods • should yield same anisotropies • different measures of spatial organization • line azimuth distribution (smaller scale) • point density (regional scale)

  11. Applications • theoretical tectonics • mineral resources location • geologic hazards

  12. Studies • Ring complexes • Kimberlite pipes

  13. Conclusions • In neither case can a convincing connection be shown between the directions of the trends indicated by the analysis and the trends of known geologic structures • located at depth and have no known surface expression • basis for predicting the locations of undiscovered or future events

  14. Thank You

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