| Title | Regional implications of geochemistry and style of emplacement of Miocene I-type diorite and granite, Delos, Cyclades, Greece |
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| Author | Pe-Piper, G; Piper, D J W ; Matarangas, D |
| Source | Lithos vol. 60, issue 1-2, 2002 p. 47-66, https://doi.org/10.1016/s0024-4937(01)00068-8 |
| Links | Abstract - Résumé
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| Image |  |
| Year | 2002 |
| Alt Series | Geological Survey of Canada, Contribution Series 2000012 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Area | Greece |
| Lat/Long WENS | 24.0000 28.0000 38.0000 36.0000 |
| Subjects | general geology; geochemistry; mineralogy; structural geology; plutons; subduction zones; quartz diorites; tonalites; magmas; shear zones; deformation; mafic rocks; granites; fractures; fault zones;
crystal fractionation |
| Illustrations | location maps; geological sketch maps; graphs; cross-sections, stratigraphic; photographs; tables; geochemical plots; cross-sections, structural |
| Program | NSERC Natural Sciences and Engineering Research Council of
Canada |
| Released | 2002 01 01 |
| Abstract | The Miocene plutons of the Cyclades were emplaced in a subduction setting during regional back-arc extension of continental crust, that led to flat-lying mid-crustal detachment faulting. Mapping of the
island of Delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction. Mafic magmas were followed by numerous small batches of felsic magma, with
magmatic and ductile deformation synchronous with magma emplacement. Late granite dykes occupy brittle fractures in the more deformed rocks. Mafic and intermediate rocks show a bimodal distribution of incompatible trace elements, with one group of
broadly tholeiitic character and the other with substantial enrichment in Sr, Nb, and HFSE, but low Th and Ba. These differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the
eastern Cyclades. Voluminous granodiorite results from these mafic magmas fractionating and/or mixing with felsic crustal material, some of which was derived by anatexis of a sedimentary protolith, indicated by high B and Mn. Some late granites
appear derived from partial melting of Hercynian paragneiss. Regionally, the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones. The shear zones parallel the Mid-Cycladic
Lineament, a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the Hellenic subduction zone. Distinctive geochemical features in Miocene igneous rocks suggests that these two blocks had
quite different geological histories. The localisation of plutonism and core complexes near the Mid Cycladic Lineament suggests that this crustal-scale shear played a role in bringing subduction-derived magmas to mid-crustal levels. The heat supplied
by the mafic magmas promoted ductile deformation high in the crust, where extension was concentrated, leading to the formation of core complexes. The regional extension resulted in progressive shallowing of the position of the granite solidus within
the crust, leading to welding of the Mid-Cycladic Lineament, which is no longer seismically active. |
| GEOSCAN ID | 211391 |
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