Subduction-related Late Cretaceous high-K volcanism in the Central Pontides orogenic belt: constraints on geodynamic implications

Abstract

Mineral chemistry, major and trace elements, 40 Ar/ 39 Ar age and Sr-Nd-Pb isotopic data are presented for the Late Cretaceous Hamsilos volcanic rocks in the Central Pontides, Turkey. The Hamsilos volcanic rocks mainly consist of basalt, andesite and associated pyroclastics (volcanic breccia, vitric tuff and crystal tuff). They display shoshonitic and high-K calc-alkaline affinities. The shoshonitic rocks contain plagioclase, clinopyroxene, alkali feldspar, phlogopite, analcime, sanidine, olivine, apatite and titanomagnetite, whereas the high-K calc-alkaline rocks contain plagioclase, clinopyroxene, orthopyroxene, magnetite / titanomagnetite in microgranular porphyritic, hyalo-microlitic porphyritic and glomeroporphyritic matrix. Mineral chemistry data reveal that the pressure condition of the clinopyroxene crystallisation for the shoshonitic rocks are between 1.4 and 6.3 kbar corresponds to 6-18-km depth and the high-K calc-alkaline rocks are between 5 and 12 km. 40 Ar/ 39 Ar age data changing between 72 ± .5 Ma and 79.0 ± .3 Ma (Campanian) were determined for the Late Cretaceous Hamsilos volcanic rocks, contemporaneous with the subduction of the Neo-Tethyan Ocean beneath the Pontides. The studied volcanic rocks were enriched in the large-ion lithophile and light rare earth element contents, with pronounced depletion in the contents of high-field-strength elements. Chondrite-normalised rare earth element patterns (La N /Lu N = 6-17) show low to medium enrichment, indicating similar sources of the rock suite. Pb/ 204 Pb values between 37.839 and 38.427. The main solidification processes involved in the evolution of the volcanic rocks consist of fractional crystallisation, with minor amounts of crustal contamination ± magma mixing. According to geochemical evidence, the shoshonitic melts in the Hamsilos volcanic rocks were possibly derived from the low degree of partial melting of a subcontinental lithospheric mantle (SCLM), while the high-K calc-alkaline melts were derived from relatively high degree of partial melting of SCLM that was enriched by fluids and/or sediments from a subduction of oceanic crust.

Major Late Cretaceous Mass Flows in Central Turkey Recording the Disruption of the Mesozoic Continental Margin

“…(b) The arc magmatism in the western Sakarya Zone starts in the Campanian (approximately 78 Ma; e.g., Aysal et al, ). In contrast, there is ample evidence for earlier arc magmatism in the eastern Sakarya Zone (Eastern Pontides, 91–72 Ma; e.g., Aydınçakır, ; Eyuboglu, ; Kaygusuz et al, ; Liu et al, ; Özdamar, ). We suggest that the eastern margin of the western Sakarya Zone formed a transform fault (Figure ), which linked the subduction under the Eastern Pontides to an intraoceanic subduction zone, which was initiated in the Turonian (approximately 93 Ma; Plunder et al, ).…”

Striking Variation in the Provenance of the Lower and Upper Cretaceous Turbidites in the Central Pontides (Northern Turkey) Related to the Opening of the Black Sea

“…The petrographic compositions of the Campanian‐Maastrichtian turbiditic sandstone samples along with the abundance of Coniacian‐Campanian detrital zircon ages (30%; Figure 11 and Table S4) indicate sediment derivation chiefly from local volcanic and plutonic sources; the lithic grains can be counted mainly as neovolcanic clasts (according to the criteria of Critelli & Ingersoll ()). The nearest dated parts of the Upper Cretaceous volcanic arc are in the Sinop area, with Ar‐Ar ages on biotite grains of 79 to 72 Ma (Aydınçakır, ; Figure ). Zircons from felsic tuffs layers in the Campanian‐Maastrichtian volcaniclastic turbidites from the Eastern Pontides yielded U–Pb zircon ages in the range of 84–71 Ma (Eyüboğlu, ) similar to the detrital zircons reported here.…”

Settlement conditions of magma (s) forming Jurassic plutonic rocks in the Gümüşhane (Eastern Pontides, Turkey)

“…The Late Cretaceous period present that a lithology dominated by plutonic and volcanic rocks of the northsouth direction in the Eastern Pontides (Okay and Şahintürk, 1997;Kaygusuz et al, 2008;Kaygusuz and Aydınçakır 2009;Karslı et al, 2012;Aydın et al, 2014;Yücel, 2017;Demir, 2019). High potassium magmatism is also widespread in the region (Altherr et al, 2008;Eyüboğlu, 2010;Gülmez et al, 2016;Aydınçakır, 2016Aydınçakır, , 2017Özdamar et al, 2017). The collision of the Eastern Pontides magmatic arc and the Anatolide-Tauride continental block occurred in the Late Palaeocene-Early Eocene (Okay and Şahintürk, 1997;Dilek, 2006).…”