GEOLOGY OF THE EARLY MIOCENE ALAÇAMDAĞ (DURSUNBEY-BALIKESİR) MAGMATIC COMPLEX AND IMPLICATIONS FOR THE WESTERN ANATOLIAN EXTENSIONAL TECTONICS

Indexed In

Volume 141 / 2010

Authors:

Fuat ERKÜL, Sibel TATAR ERKÜL

Keywords:

Stratigraphy, ductile deformation, extensional tectonics, volcano-sedimentary successions, Northwestern Anatolia.

Abstract:

Extensional regime in western Anatolia caused development of metamorphic core complexes, NEand E-W-trending basins and emplacement of magmatic rocks since Late Oligocene and Early Miocene. The Alaçamdað magmatic complex, which is located to the west of the Simav metamorphic core complex, includes significant data that highlight the style of extensional regime in western Turkey. It consists of Early Miocene granitic intrusions and volcanic rocks with variable compositions ranging from basalt to rhyolite. The granitic intrusions that were emplaced into the basement rocks of the Menderes Massive and Ýzmir-Ankara Zone are divided into two facies based on their lithological and textural characteristics: Musalar and Alaçam granites. The Musalar granite has typical holocystalline equigranular texture, while the Alaçam granite is characterised by its porphyritic texture defined by abundant K-feldspar megacrysts. Both granite units were locally transformed into mylonites along shear zones. Volcanic rocks consist of Saðýrlar volcanic unit and felsic volcanic rocks. Saðýrlar volcanic unit is made up of andesitic/dacitic intrusions, domes, lava flows, dykes and volcanogenic sedimentary rocks. The felsic volcanic rocks, which unconformably overlies the Saðýrlar volcanic unit, consist of ignimbrite, dacite and rhyolite. These rocks have transitional contacts with alluvial/lacustrine sedimentary deposits. Ductile deformation on the granitic rocks, intra-basinal unconformities and syn-sedimentary deformational structures within the deposits are closely associated with the development of extensional regime during Early Miocene in western Turkey.