التفاصيل البيبلوغرافية
| العنوان: |
Post-Collisional Transition from Subduction- to Intraplate-type Magmatism in the Westernmost Mediterranean: Evidence for Continental-Edge Delamination of Subcontinental Lithosphere. |
| المؤلفون: |
S. DUGGEN, K. HOERNLE, P. VAN DEN BOGAARD, D. GARBE-SCHNBERG |
| المصدر: |
Journal of Petrology; Jun2005, Vol. 46 Issue 6, p1155-1201, 47p |
| مصطلحات موضوعية: |
VOLCANIC ash, tuff, etc., IGNEOUS rocks, PLATE tectonics, SUBDUCTION zones |
| مستخلص: |
Post-collisional magmatism in the southern Iberian and northwestern African continental margins contains important clues for the understanding of a possible causal connection between movements in the Earth''s upper mantle, the uplift of continental lithosphere and the origin of circum-Mediterranean igneous activity. Systematic geochemical and geochronological studies (major and trace element, SrNdPb-isotope analysis and laser 40Ar/39Ar-age dating) on igneous rocks provide constraints for understanding the post-collisional history of the southern Iberian and northwestern African continental margins. Two groups of magmatic rocks can be distinguished: (1) an Upper Miocene to Lower Pliocene (8248?Ma), SiK-rich group including high-K (calc-alkaline) and shoshonitic series rocks; (2) an Upper Miocene to Pleistocene (63065?Ma), Si-poor, Na-rich group including basanites and alkali basalts to hawaiites and tephrites. Mafic samples from the SiK-rich group generally show geochemical affinities with volcanic rocks from active subduction zones (e.g. IzuBonin and Aeolian island arcs), whereas mafic samples from the Si-poor, Na-rich group are geochemically similar to lavas found in intraplate volcanic settings derived from sub-lithospheric mantle sources (e.g. Canary Islands). The transition from Si-rich (subduction-related) to Si-poor (intraplate-type) magmatism between 63?Ma (first alkali basalt) and 48?Ma (latest shoshonite) can be observed both on a regional scale and in individual volcanic systems. SiK-rich and Si-poor igneous rocks from the continental margins of southern Iberia and northwestern Africa are, respectively, proposed to have been derived from metasomatized subcontinental lithosphere and sub-lithospheric mantle that was contaminated with plume material. A three-dimensional geodynamic model for the westernmost Mediterranean is presented in which subduction of oceanic lithosphere is inferred to have caused continental-edge delamination of subcontinental lithosphere associated with upwelling of plume-contaminated sub-lithospheric mantle and lithospheric uplift. This process may operate worldwide in areas where subduction-related and intraplate-type magmatism are spatially and temporally associated. [ABSTRACT FROM AUTHOR] |
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