Burial and thrust-related very low-grade metamorphism in the Upper Paleozoic meta-sedimentary rocks at the Kangal-Alacahan area, Sivas, Turkey

Abstract

Kangal formation meta-clastics of Middle Devonian-Lower Carboniferous have different lithologic, textural and mineralogic features related to sedimentary burial and thrust, from bottom to top, in the Kangal-Alacahan area. Kinalar member (slates and less meta-siltstone, with chlorite-mica pod) contain phyllosilicates (2Mi illite/muscovite, Ilb chlorite, mixed-layer paragonite-muscovite-P-M, paragonite, pyrophyllite, kaolinite/dickite, mixed-layer chlorite-vermiculite-C-V, mixed-layer chlorite-smectite-C-S), calcite, quartz, geothite and chloritoid, in order of decreasing abundance. IC values are indicative of low epizonal-high anchizonal conditions. Quarts, phyllosilicates (2Mi+1Md illie/muscovite, kaolinite/dickite), felspar and geothite are present in the anchimeta-sandstone and anchimeta-shale and/ or slates of Bakirtepe member, which represents middle anchizone IC values. The anchimeta-shale, anchimeta-siltstone, anchimeta-limestone, anchimetra-sandstone and slates with chlorite-mica pod in the Duzce member mainly consist of phyllo-silicates (2M1=Md illite/muscotite, Ilb chlorite, M-p, paragonite, kaolinite/dickite, pyrophyllite, C/V, C/S), quartz, calcite and geothite. IC measurements of meta-clastics show high-grade anchizone. Hoyuk member is commonly composed of crystallized limestone, and rarely sandstone and shale that corresponds to low anchimetamorphic or high diagenetic dgree. The unit includes calcite, quartz, phyllosilicates (illite/muscovite, chlorite and kaolinite/dicktie) and geothite. The index minerals related to thrust such as P-M, paragonite, pyrophyllite and chloritoid are found in the allochthonous Kangal formation that appears as an indicator to distinguish allochthonous and autochthonous units. In addition, paragenetic relationships suggest that meta-sedimentary rocks are metamorphosed in anticlockwise P-T-t(pressure-temperature-time) path and then clockwise P-T-t path as a result of burial and thrust tectonics, respectively.