Mantle source characteristics and melting models for the early-middle Miocene mafic volcanism in Western Anatolia Implications for enrichment processes of mantle lithosphere and origin of K-rich volcanism in post-collisional settings

作者：Ersoy E Yalcin^*; Helvaci Cahit; Palmer Martin R

来源：Journal of Volcanology and Geothermal Research, 2010, 198(1-2): 112-128.

DOI：10.1016/j.jvolgeores.2010.08.014

• Western Anatolia
• Neogene volcanism
• Shoshonitic volcanism
• Ultrapotassic volcanism
• Subduction enrichment

In Western Anatolia early-middle Miocene post-collisional volcanism is represented by K nch volcanic rocks including calc alkaline high-K calc-alkaline shoshonitic and ultrapotasstc products Low-SIO2 and relatively high-MgO mafic volcanic rocks in the region are represented by high-K volcanic rocks (HKVR) in the west where strike-slip tectonics related to the Izmir-Balikesir Transfer Zone dominates while shoshonitic and ultrapotassic volcanic rocks (SHVR and UKVR) occur in the eastern part of the region where mid-crustal units were exhumed along detachment faults during orogenic collapse All three rock groups have nearly identical Sr-Nd Isotope ratios but the SHVR and UKVR are more enriched in incompatible trace elements relative to the HKVR. Comparison of the geochemical characteristics of the most primitive lavas (SiO2<55 wt % Mg#>65 and MgO>6 wt %) provides an important tool in discussing the origin and evolution of the K-rich magmatic activity in this post-orogenic setting
Geochemical features of the three rock groups require they were all derived from a primitive mantle-like source that, on the basis of Sr-Nd isotope mixing models was supplemented by addition of 7-15% sediment components including both sediment fluid and sediment melt Low-degree partial melting (similar to 5-10%) of this modified mantle source can account for the incompatible trace element budgets of the HIM but an additional trace element enrichment process is required to explain the compositions of the SHVR and UKVR. Numerical modeling suggests that this enrichment developed by multi-stage melting and melt percolation processes in a thicker metasomatized mantle lithosphere than that which produced the HKVR. This petrogenetic model accords with tectonic observations of lithospheric thickening from west to east in the area (where strike-slip deformation occurred to the west and regional uplift and exhumation occurred to the east) Hence the first enrichment stage of the mantle source (HKVR plus SHVR and UKVR) is interpreted to be the result of subduction related processes during southward

• 出版日期2010-12-1