The tensile strength of the lithosphere and the localization of extension

Abstract

Continents appear to rift in preference to oceans. Furthermore, some areas of continents appear to be more susceptible to rifting than others. Experimental rock mechanics data are used to estimate lithospheric strength for lithospheres of different structure, thereby to investigate the possible causes of rift localization. Using optimum creep parameters for silicic, mafic and ultramafic rocks, we find that lithospheric strength is inversely related to both crustal thickness and heat flow. By virtue of its thinner crust, oceanic lithosphere is inherently stronger than continental lithosphere. We find that oceanic lithosphere older than about 10 Ma should be able to withstand the lithospheric forces exerted on it by gravity sliding and plate interactions. Rifting or ridge-jumps are therefore only likely to occur in very young oceanic lithosphere. Low heat flow continental shields should also be able to withstand likely lithospheric forces without significant deformation. As the heat flow increases, however, the lithosphere is weakened dramatically. A smaller amount of weakening is associated with crustal thickening. Thus, unless rifting is localized by a strongly heterogeneous stress field, it will be by anomalously weak lithosphere. This lithosphere is likely to have anomalously high heat flow and/or crustal thickness prior to extension.

Calculation of temperature distribution and rheological properties of the lithosphere along transect I in the Western Carpathians

“…Ductile strength is calculated assuming a power-law creep deformation given as (Lynch and Morgan, 1987):…”

Metamorphic Core Complex dynamics and structural development: Field evidences from the Liaodong Peninsula (China, East Asia)

“…First, previous modelling studies strongly suggest that local "soft" anomalies in the lower crust help to the initiation of MCC development, as discussed before (Tirel et al, 2008). Second, at regional-scale, widespread melting and/or magmatism can significantly reduce the bulk lithosphere strength, emphasizing continuous pervasive deformation of the deepest levels of the lithosphere (Van der Molen and Paterson, 1979;Reynolds and Rehrig, 1980;Coney and Harms, 1984;Lynch and Morgan, 1987; see synthesis in Handy and Brun, 2004). Then, within South Liaodong area, the continental crust mechanical behaviour in the Late Jurassic and Early Cretaceous may have been strongly controlled by melts generation at the onset and during the extension period.…”

Metamorphic Core Complexes vs. synkinematic plutons in continental extension setting: Insights from key structures (Shandong Province, eastern China)

“…In fact, exhumation and deformation of middle to lower crustal rocks and development of master detachment faults lead to consider a large amount of extension for the whole crust. Moreover, extension processes can be favoured by partial melting and widespread magmatism that strongly weakens the lithosphere, emphasizing deformation and strain localization (Reynolds and Rehrig, 1980;Coney and Harms, 1984;Lynch and Morgan, 1987). In such an extensive setting, synkinematic plutons that can emplace along major shear zones in the upper crust are of efficient markers to study crustal deformation (e.g.…”