First results of fission-track thermochronology in the Albanides

Abstract

Albania, situated at the boundary between the Dinaric and the Hellenic branchs of the Dinaro-Hellenic fold belt, has experienced a multiphase geodynamic evolution. The internal zones show a Mid-Jurassic episode of deformation characterized by ophiolite obduction, followed by development of a fold-and-thrust belt in the external zones during the Cenozoic. More recently, Albania has experienced a tensional regime. We present apatite and zircon fission-track (AFT and ZFT) measurements for 22 samples, and seven measurements of track-length distributions to elucidate the thermal evolution. AFT ages vary from 10.8 ± 0.7 Ma to 50.5 ± 5.7 Ma. The oldest ages (Eocene) occur in the western Albanides, corresponding to Eocene emplacement of the internal zones over the external ones. Neogene ages in the eastern Albanides suggest rapid exhumation, which we relate to an extensional regime. The ZFT ages show that the internal Albanides did not reach temperatures > 200 °C during the Cenozoic

New constrains on the thickness of the Semail ophiolite in the Northern Emirates

“…Because ophiolites are assumed to represent part of or the entire oceanic crust and upper part of the mantle of former oceanic lithospheric plates, and are commonly associated with either high pressure-low temperature (blueschist facies) or high pressure-high temperature (amphibolite facies) metamorphic sole, zero or very limited petroleum exploration has been yet initiated beneath the Mirdita Ophiolite in the central foothills of Albania, nor under the Semail Ophiolite which crops out in the Northern Emirates and in the adjacent parts of Oman. Nevertheless, improvements of seismic imagery and better estimates on the timing of erosional unroofing by means of paleo-thermometers provide new ways to properly predict the paleo-burial and coeval paleotemperature reached by reservoirs and source rocks associated with the lower plate below the ophiolite (Muceku et al 2007;Roure et al 2010a, b), and therefore, to better evaluate the exploration risk in such challenging, yet unexplored frontier areas. In this context, results of an integrated geophysical and geological survey of the Northern Emirates are discussed below to document our understanding on both the current thickness of the Semail Ophiolite west of the Masafi tectonic window, and on the timing of its erosional unroofing history.…”

The Vardar zone as a suture for the Mirdita ophiolites, Albania: Constraints from the structural analysis of the Korabi-Pelagonia zone

“…However, such postobduction top‐to‐the‐west thrusting also occurred in the most internal zones of the Dinarides, where it led to the individualization of composite thrust sheets consisting of Adria margin rocks and overlying ophiolites and to collision between Adria and Europe at the end of the Cretaceous along the Sava Zone (Figure a) [ Schmid et al ., ]. Compressive deformation in our working area continues at least until late Oligocene to early Miocene, from which time period the deformational regime evolved into crustal extension (Figure e) with the formation of low‐ and high‐angle extensional faults revealed by low‐temperature thermochronologic age data [ Muceku et al ., , ] (see above), contemporaneous with still ongoing compression along the Albanian coast.…”

“…Thus, the latter two units, as well as the Korabi subzone, record regional structures that were formed before the Early Cretaceous and after the Early Jurassic, either slightly during or immediately after ophiolite obduction that caused crustal thickening of the underlying Pelagonian continental margin. Zircon fission tracks ages measured in the Korabi subzone vary from 156 ± 17 Ma to 125.1 ± 12.9 to 116.8 ± 10.7 Ma (Figure ) [ Muceku et al ., ], indicating that during the earliest Cretaceous, rock units currently exposed in the Korabi subzone were at crustal temperatures lower than approximately 240°C, i.e., the closure temperature for fission track retention in zircon [e.g., Reiners and Brandon , ]. This is well below the minimal temperature conditions that were attained during the regional D 1 ‐related greenschist facies metamorphism that characterizes these rocks and clearly indicates that D 1 deformation is older than the Early Cretaceous.…”

Thermochronological evidence for Mio‐Pliocene late orogenic extension in the north‐eastern Albanides (Albania)

“…In contrast, the recent evolution of the Central Belt and the Internal Complex, together known as the Internal Albanides, has received much less attention. Recently published apatite and zircon FT data from the Internal Albanides show that the eastern part of the orogen experienced apparently rapid cooling and exhumation since the late Pliocene, whereas the western Internal Albanides show much slower exhumation throughout the Cenozoic (Muceku et al. , 2006).…”

“… Schematic geological map of the Albanides (modified from SHGJSH, 2003) showing main structural provinces as well as recent (Muceku et al. , 2006) and new thermochronological results.…”