US EPA

7465318 

Journal Article 

Geochemical Characteristics of Mafic and Intermediate Volcanic Rocks from the Hasandag and Erciyes Volcanoes (Central Anatolia, Turkey) 

Guctekin, A; Koprubasi, N 

2009 

1 

Turkish Journal of Earth Sciences
ISSN: 1300-0985
EISSN: 1303-619X 

18 

1 

1-27 

English 

WOS:000264771000001 

http:///www.tubitak.gov.tr
Exit
 

Hasandag and Erciyes stratovolcanoes, which are the two important stratovolcanoes in Central Anatolia, erupted volcanic products with both calc-alkaline and alkaline compositions, although the calc-alkaline activity is more widespread. There are three stages of geochemical evolution in the history of the Hasandag stratovolcanic complex: (1) Kecikalesi tholeiitic volcanism, (2) Hasandag calc-alkaline volcanism, and (3) Hasandag alkaline volcanism. The geochemical evolution of Erciyes volcanic complex also exhibits three distinct evolutionary stages: (1) Kocdag alkaline volcanism, (2) Kocdag calc-alkaline volcanism and (3) Erciyes calc-alkaline volcanism. The volcanic rocks from both suites show enrichments in LREE relative to HREE. The rocks as a whole show enrichments in large ion lithophile elements (LILE) relative to high field strength elements (HFSE) in N-MORB normalized multi-element diagrams, although the thoeliitic and alkaline rocks have less pronounced effects of HFSE/LILE fractionation comparing to the calc-alkaline rocks. Theoretical fractionation models obtained using the whole-rock trace element data indicate two distinct fractionation trends for the Hasandag volcanism: amphibole and plagioclase fractionation for the tholeiitic and calc-alkaline rocks and plagioclase, pyroxene and amphibole fractionation for the alkaline rocks. The alkaline and calc-alkaline rocks of Erciyes volcanism, on the other hand, indicate similar fractionation trends that can be explained by plagioclase and amphibole fractionation. AFC modelling indicate that the effect of crustal contamination on parental melt compositions is less pronounced in the Erciyes volcanic rocks compared to the Hasandag volcanic rocks. Theoretical melting trends obtained using the non-modal batch melting model indicate degree of melting between 8-9% for the Ke ikalesi tholeiitic rocks, 4-5% for the Hasandag alkaline rocks and 3-8% for the Kocdag alkaline rocks. The modeling also shows that the Central Anatolian volcanic rocks were originated by variable degree melting of a mantle source with garnet+spinel lherzolite composition, although the effect of residual garnet in the source is more pronounced for the Hasandag alkaline rocks. Geochemical modeling indicates that Central Anatolian volcanic rocks are likely to have originated by partial melting of a metasomatised lithospheric mantle. Delamination of TBL (termal boundary layer) may be considered as a potential mechanism that may cause thermal perturbation melting of continental lithospheric mantle. The distribution of volcanic centres along the region-scale strike-slip fault systems may also indicate additional effects of strike-slip faulting on melt production and eruption. 

Central Anatolia; collision volcanism; lithospheric delamination; Turkey