TY - CHAP
T1 - Geometric scaling of tabular igneous intrusions
T2 - implications for emplacement and growth
AU - Cruden, Alexander Ramsay
AU - McCaffrey, Kenneth J.W.
AU - Bunger, Andrew
PY - 2018
Y1 - 2018
N2 - The horizontal (L) and vertical (T) dimensions of broadly tabular,sub-horizontal intrusions of mafic to felsic composition emplaced intoshallow to mid-crustal levels of continental crust reveal two well-definedand continuous curves in log L vs. log T space. The data set spans six andfive orders of magnitude in L (1 m to 1000 km) and T (10 cm to 10 km),respectively. Small tabular sheets and sills (mafic and felsic) define astraight line with a slope * 0.5 at all horizontal length scales, similar tothe known geometric scaling of mafic dikes, indicating that the L/T ratio ofthese intrusions to increases with increasing L (horizontal lengtheningdominates over vertical thickening). Laccoliths, plutons, layered maficintrusions and batholiths define an open, continuous S-shaped curve thatbifurcates from the tabular sheets and sills curve at L * 500 m towardshigher T values. For L * 0.5 to 10 km the slope of this curve is * 1.5,corresponding to laccoliths that are characterized by a decrease in L/T ratiowith increasing L (vertical thickening dominates over horizontal lengthening).Between L * 10 and 100 km the slope has a mean value * 0.8,indicating that plutons and layered mafic intrusions have a tendency forhorizontal lengthening over vertical thickening as L increases. Batholiths and very large layered mafic intrusions with L > 100 km lie on a slope* 0 with a threshold thickness * 10 km. The continuous nature of thedimensional data over such a wide range of length scales reflects aspectrum of igneous emplacement processes repeated in space and time.We discuss how thresholds and transitions in this spectrum, defined bybifurcations between the curves (e.g., between sill and laccolith emplacement)and changes in slope, largely reflect depth- and time-dependentchanges in emplacement mechanisms rather than factors such as magmaviscosity, composition and temperature.
AB - The horizontal (L) and vertical (T) dimensions of broadly tabular,sub-horizontal intrusions of mafic to felsic composition emplaced intoshallow to mid-crustal levels of continental crust reveal two well-definedand continuous curves in log L vs. log T space. The data set spans six andfive orders of magnitude in L (1 m to 1000 km) and T (10 cm to 10 km),respectively. Small tabular sheets and sills (mafic and felsic) define astraight line with a slope * 0.5 at all horizontal length scales, similar tothe known geometric scaling of mafic dikes, indicating that the L/T ratio ofthese intrusions to increases with increasing L (horizontal lengtheningdominates over vertical thickening). Laccoliths, plutons, layered maficintrusions and batholiths define an open, continuous S-shaped curve thatbifurcates from the tabular sheets and sills curve at L * 500 m towardshigher T values. For L * 0.5 to 10 km the slope of this curve is * 1.5,corresponding to laccoliths that are characterized by a decrease in L/T ratiowith increasing L (vertical thickening dominates over horizontal lengthening).Between L * 10 and 100 km the slope has a mean value * 0.8,indicating that plutons and layered mafic intrusions have a tendency forhorizontal lengthening over vertical thickening as L increases. Batholiths and very large layered mafic intrusions with L > 100 km lie on a slope* 0 with a threshold thickness * 10 km. The continuous nature of thedimensional data over such a wide range of length scales reflects aspectrum of igneous emplacement processes repeated in space and time.We discuss how thresholds and transitions in this spectrum, defined bybifurcations between the curves (e.g., between sill and laccolith emplacement)and changes in slope, largely reflect depth- and time-dependentchanges in emplacement mechanisms rather than factors such as magmaviscosity, composition and temperature.
U2 - 10.1007/11157_2017_1000
DO - 10.1007/11157_2017_1000
M3 - Chapter (Book)
SN - 9783319140834
T3 - Advances in Volcanology: An Official Book Series of the International Association of Volcanology and Chemistry of the Earth’s Interior
SP - 11
EP - 38
BT - Physical Geology of Shallow Magmatic Systems
A2 - Breitkreuz, Christoph
A2 - Rocchi, Sergio
PB - Springer
CY - Cham Switzerland
ER -