Terlemez quartz monzonite of Central Anatolia (Aksaray-Sarıkaraman): age, petrogenesis and geotectonic implications for ophiolite emplacement

Abstract

The Terlemez quartz monzonite is one of the Central Anatolian Granitoids and is exposed to the east of one of the main granitoid belts trending in a NW–SE direction and situated at the western end of the Central Anatolian Crystalline Complex. The Terlemez quartz monzonite is medium- to coarse-grained with granoblastic texture. It is essentially composed of quartz, plagioclase, hornblende and K-feldspar and variable contents of biotite. It is mostly compact and massive, but close to the contact with the ophiolitic basic rocks it shows a chilled margin. It characteristically includes K-feldspar megacrysts up to 3 cm in width and 10 cm in length, and contains irregular, angular or sub-rounded micromafic granular enclaves as well as xenoliths and large ‘roof-pendants’ of gabbroic composition derived from the Sarıkaraman Ophiolite, which is the most representative member of the supra-subduction zone type of Central Anatolian Ophiolites. The Terlemez quartz monzonite is a calc-alkaline, metaluminous intrusion. It typically displays moderately developed negative Ba and Nb trace element anomalies and enrichment in light rare earth elements relative to heavy rare earth elements without any significant Eu, Sr and Ti anomalies. On the basis of field, petrographic and geochemical data, the Terlemez quartz monzonite has been classified as H-type (hybrid type), which requires significant input from a mantle-derived mafic magma. The intrusion represents the advanced stage of the post-collisional magmatism of the Central Anatolian Crystalline Complex. Unlike the other Central Anatolian Granitoids, the Terlemez quartz monzonite has a clear intrusive contact with the well studied Middle Turonian–Lower Santonian Sarıkaraman Ophiolite. The K-Ar hornblende age obtained from the quartz monzonite (81·5 ± 1·9 Ma) is interpreted as the intrusion age. These data suggest a post-Early Santonian to pre-Early Campanian emplacement age for the supra-subduction zone type of Central Anatolian Ophiolites. The data further suggest that the post-collisional magmatism in Central Anatolia post-dates the emplacement of fore arc-type ophiolites onto the passive margin of the Tauride–Anatolide platform. The very short time interval between the formation and emplacement ages of supra-subduction zone-type ophiolites seems to be a very typical feature of the fore arc-type Eastern Mediterranean Ophiolites. Copyright © 1999 John Wiley & Sons, Ltd.