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

The Terlemez quartz monzonite is one of the Central Anatolian Granitoids an d is exposed to the east of one of the main granitoid belts trending in a N W-SE direction and situated at the western end of the Central Anatolian Cry stalline Complex. The Terlemez quartz monzonite is medium- to coarse-grained with granoblasti c texture. It is essentially composed of quartz, plagioclase, hornblende an d K-feldspar and variable contents of biotite. It is mostly compact and mas sive, but close to the contact with the ophiolitic basic rocks it shows a c hilled margin. It characteristically includes K-feldspar megacrysts up to 3 cm in width and 10 cm in length, and contains irregular, angular or sub-ro unded micromafic granular enclaves as well as xenoliths and large 'roof-pen dants' of gabbroic composition derived from the Sankaraman Ophiolite, which is the most representative member of the supra-subduction zone type of Cen tral Anatolian Ophiolites. The Terlemez quartz monzonite is a calc-alkaline, metaluminous intrusion. I t typically displays moderately developed negative Ba and Nb trace element anomalies and enrichment in light rare earth elements relative to heavy rar e earth elements without any significant Eu, Sr and Ti anomalies. On the ba sis of field, petrographic and geochemical data, the Terlemez quartz monzon ite has been classified as PI-type (hybrid type), which requires significan t input from a mantle-derived mafic magma. The intrusion represents the adv anced stage of the post-collisional magmatism of the Central Anatolian Crys talline Complex. Unlike the other Central Anatolian Granitoids, the Terlemez quartz monzonit e has a clear intrusive contact with the well studied Middle Turonian-Lower Santonian Sankaraman 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 dat a further suggest that the post-collisional magmatism in Central Anatolia p ost-dates the emplacement of fore are-type ophiolites onto the passive marg in 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 are-type Eastern Mediterran ean Ophiolites. Copyright (C) 1999 John Wiley & Sons, Ltd.