The Beypazarı Granitoid is an arc-related intrusion in the Central Pontides, Turkey. This study presents apatite fission track (AFT) ages of the intrusion to shed some light on collision-related cooling/exhumation history of the central Pontides. The AFT ages from different altitudes (506–805-1110 metres above sea level) of the Beypazarı Granitoid yield around 65 ± 3 Ma. This indicates a rapid cooling/exhumation for the intrusion around 65 Ma, which is attributed to the commencement of the collision event in the region. Integration of these ages and low-temperature thermochronology literature suggests a progressive collision propagation towards the margins of the collision system.
Sarıhıdır travertines and associated manganese mineralization are located in an area known as the Central Anatolian Volcanic Province (CAVP). The topic of the study, the Sarıhıdır manganese mineralization, was deposited in association with fault zones in this tectonically-active region. Paragenesis of the mineralization includes pyrolusite, rhodochrosite and goethite with gangue minerals of calcite and quartz observed. Diagrams drawn using major oxide and trace elements like Fe–Mn–(Ni+Co+Cu)×10, Fe-Si×2-Mn, Co/Ni vs Cu+Co+Ni, Si/Al, Na/Mg, Fe/Ti vs. Al/(Al+Fe+Mn), Co+Ni/As+Cu+Mo+Pb+V+ Zn and FeO–MnO2–10× MgO show the mineralization found in the region is sourced in the hydrothermal field. The low total REE values and LREE>HREE ratio indicate the effect of hydrothermal solutions. Additionally, Ce, Eu and Ceanom anomalies indicate the source of the mineralization was hydrothermal with oxic-anoxic formation environment. The Y/Ho ratio is mean 30.1 which is lower compared to hydrothermal fluids. Mean values are δ13CPDB 12.24‰ and δ18OPDB 10.87‰ indicating deposition from fluids with a deep CO2 component. In conclusion, the Sarıhıdır mineralization and travertine were determined to have formed about 50–53 ka (Upper Pleistocene) based on U-series age data, as fault-controlled, hydrothermal-sourced mineralization.
The Wa-Lawra Belt which is situated in the northern part of Ghana consists of Paleoproterozoic Birimian fine metasedimentary rocks metamorphosed to greenschist facies, particularly, in the western part. A whole-rock geochemical study of these metasedimentary rocks was undertaken to unravel their source area weathering, provenance and tectonic setting. Geochemical characteristics of the studied shales show that they are immature in nature and first cycle in origin, with little or no recycled component. Compared to Post-Archaean Australian Shales (PAAS), the studied shales indicate reduction in Zr, Hf, La, Nb, Th and Ta being the high field strength elements and evidences of transition metal enrichments in V, Ni, Sc, Co, and Cr. Major element geochemistry indicates that the shales were subjected to slight potassium metasomatism after deposition. Pre-metasomatized Chemical Index of Alteration calculations indicates that weak to moderate degree of chemical weathering took place at the sediment source area. Co-Th-La-Sc systematics reveals a combination of mafic and felsic provenances for the shales. Eu/Eu* together with values of Th/U and some abundances of trace elements show that the shales were mainly derived from juvenile rocks. Average REE model calculations suggest that the source materials are composed of about 49% basalt, 16% TTG and 35% granite.
Granitoids of the Ekecikdağ Igneous Association (Central Anatolia/Turkey) are products of collisional–post-collisional magmatism in the Ekecikdağ area. These granitoids are granodiorite, microgranite and leucogranite. Field relations of granodiorites with microgranites is obscured, but leucogranites intrude both rock types. Mean zircon laser ablation (LA)-ICP-MS 206Pb-238U ages of granodiorites and microgranites are 84.52 ± 0.93 Ma and 80.7 ± 1.6 Ma, respectively, and age of leucogranites is suggested as 80 Ma, based on field relations combined with 206Pb/238U and Rb-Sr ages. Crystallisation temperatures of granodiorites, microgranites and leucogranites are 728°C-848°C, 797°C-880°C, 704°C-809°C, respectively. Geochemical characteristics including Sr-Nd isotopic evidences infer a non-cogenetic character, as there is a high crustal contribution in I-type granodiorite sources, a crustal source with insignificant and significant mantle inputs in S-type microgranites and leucogranites, respectively. LA-ICP-MS Lu-Hf isotope data from zircons reveal their crustal nature (εHf(t): −1.3 ± 0.5 to −8.8 ± 0.5). Crustal melting linked to the Alpine thickening during the Late Cretaceous led to formation of heterogeneous sourced granitoids with crustal dominated sources in the Ekecikdağ area. Understanding of the nature and evolution of collisional Ekecikdağ granitoids is not only important to put contribution in the geodynamic evolution of Central Anatolia and surrounding Alpine area, but also to better understand systematics of collisional magmatic systems.
Abstract Anorthosite-bearing layered intrusions are unique to the Archaean rock record and are abundant in the Archaean craton of southern West Greenland and the Superior Province of Canada. These layered intrusions consist mainly of ultramafic rocks, gabbros, leucogabbros and anorthosites, and typically contain high-Ca (>An70) megacrystic (2–30 cm in diameter) plagioclase in anorthosite and leucogabbro units. They are spatially and temporally associated with basalt-dominated greenstone belts and are intruded by syn-to post-tectonic granitoid rocks. The layered intrusions, greenstone belts and granitoids all share the geochemical characteristics of Phanerozoic subduction zone magmas, suggesting that they formed mainly in a suprasubduction zone setting. Archaean anorthosite-bearing layered intrusions and spatially associated greenstone belts are interpreted to be fragments of oceanic crust, representing dismembered subduction-related ophiolites. We suggest that large degrees of partial melting (25–35%) in the hotter (1500–1600 °C) Archaean upper mantle beneath rifting arcs and backarc basins produced shallow, kilometre-scale hydrous magma chambers. Field observations suggest that megacrystic anorthosites were generated at the top of the magma chambers, or in sills, dykes and pods in the oceanic crust. The absence of high-Ca megacrystic anorthosites in post-Archaean layered intrusions and oceanic crust reflects the decline of mantle temperatures resulting from secular cooling of the Earth.
