Geochemical Comparison of Ultramafic-Mafic Cumulate Rocks from the Central Anatolian Ophiolites, Turkey

摘要

Ophiolites, formed during closure of the Neo-Tethyan ocean, are widespread in Turkey and have been extensively studied. In addition to ophiolites showing recognizable stratigraphic sequences, numerous massive and layered gabbroic masses occur as isolated outcrops in the Central Anatolian Crystalline Complex. An example from the Akcakent region ranges from gabbro to diorite; another, from the Kustepe area, is characterized by dunite, wehrlite, troctolite, olivine gabbro, clinopyroxene gabbro, elinopyroxene hornblende gabbro, uralite gabbro, and fine-grained gabbro. Samples from both regions display adcumulate and orthocumulate textures and show low-K and subalkaline characters; they are enriched in some LILE (e.g., Sr, Rb, K, Ba) and depleted in HFSE (e.g., Ta, Nb, Zr, Ti) relative to N-MORB. Petrologieal data, negative Ta, Nb, Zr, Ti anomalies, and ratios of elements such as Ba/Nb and La/Nb indicate a suprasubduetion setting for the central Anatolian ultramafic-mafic rocks, suggesting that both rock types may have formed in a backarc setting.