Petrogenesis of mafic collision zone magmatism: The Armenian sector of the Turkish–Iranian Plateau

Transition From Low‐K to High‐K Calc‐Alkaline Magmatism at Approximately 84 Ma in the Eastern Pontides (NE Turkey): Magmatic Response to Slab Rollback of the Black Sea

“…(c) ε Nd ( t ) versus zircon ε Hf ( t ) of the eastern Pontides granitoids. The composition of curve 1 end‐members used for mixing calculations is the LJLC composition that is represented by a gabbro sample of L8.7 at 150 Ma (N41°05′, E44°41′; Neill et al, ): Nd = 18.6 ppm, Hf = 4.0 ppm, ε Nd ( t ) = +4.9, and ε Hf ( t ) = +10.9; the AMUC composition is represented by our 312‐Ma Gümüşhane syenogranite sample 14TK23 (N40°27′, E39°29′). The composition of AMUC in curve 1: Nd = 20.7 ppm, Hf = 5.1 ppm, ε Nd ( t ) = −7.6, and ε Hf ( t ) = −8.3; in curve 2: ε Hf ( t ) = −4.0, ε Nd ( t ) = −7.6, Hf = 2.9 ppm, and Nd = 32 ppm; and in curve 3: ε Hf ( t ) = −14.6, ε Nd ( t ) = −7.6, Hf = 6.4 ppm, and Nd = 16.0 ppm.…”

“…As Al‐in‐hornblende geobarometer reveals an emplacement depth of middle‐upper crust level (1.4–4.5 kbar) for the Carboniferous granitoids from Gümüşhane (Topuz et al, ), a high‐K calc‐alkaline syenogranite from Gümüşhane was selected as the enriched ancient middle‐upper crust basement (AMUC). Taking a gabbro sample from Lori as the juvenile lower crust (LJLC) (Neill et al, ), the modeling results of binary mixing of these two end‐members indicate that incorporation of 5–30% AMUC melts into LJLC‐derived magmas could generate the Nd‐Hf‐O isotopic compositions of the Group I samples (Figures c and d).…”

Long Wavelength Progressive Plateau Uplift in Eastern Anatolia Since 20 Ma: Implications for the Role of Slab Peel‐Back and Break‐Off

“…Although the depth/distribution of the mantle flow varies (e.g., shallower/near crust under the foreland and deeper lithosphere under the hinterland), such processes can induce decompression related magmas (alkaline magmatism) under both the northern (e.g., Geghema highland Armenia) (Lebedev, Chernyshev, et al, ) and southern part of the plateau. This would serve as an alternative mechanism to small‐scale convective instabilities and related melt production that may have operated under the Lesser Caucasus (Kaislaniemi et al, ; Neill et al, ). We note that the numerical experiments used in this work do not include formulations of thermopetrological properties of hydrous versus dry (decompression related) melt production; therefore, these results cannot be directly reconciled with the varying chemistry of magmatism in Eastern Anatolia (e.g., calc‐alkaline to alkaline transition), while it helps to interpret the geodynamic origin (heating induced by mantle upwelling) for the volcanism and the surface (dynamic) uplift.…”

Evolving Mantle Sources in Postcollisional Early Permian‐Triassic Magmatic Rocks in the Heart of Tianshan Orogen (Western China)

“…Postcollisional mafic magmatism provides a unique opportunity to study the asthenospheric and lithospheric mantle after the cessation of arc magmatism, and is important in understanding the evolution of orogenic belts (Carlson et al, ). Calc‐alkaline and potassium‐enriched (K‐rich) volcanic rocks are two types of postcollisional magmatism recognized in the modern mountain belts in Tibet (Guo et al, ; Turner et al, ; Williams et al, ) and the Turkish‐Iranian Plateau (Allen et al, ; Neill et al, ). Postcollisional mafic rocks are generally considered to be derived by partial melting of enriched mantle sources (Kirchenbaur et al, ).…”