scholarly journals Polyphase evolution of Pelagonia (northern Greece) revealed by geological and fission-track data

Solid Earth ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 285-302 ◽  
Author(s):  
F. L. Schenker ◽  
M. G. Fellin ◽  
J.-P. Burg
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Fission Track ◽  
Regional Scale ◽  
Normal Faults ◽  
Recent Sediment ◽  
Northern Greece ◽  
Rapid Cooling ◽  
Fission Track Ages ◽  
Pelagonian Zone

Abstract. The Pelagonian zone, situated between the External Hellenides/Cyclades to the west and the Axios/Vardar/Almopias zone (AVAZ) and the Rhodope to the east, was involved in late Early Cretaceous and in Late Cretaceous–Eocene orogenic events whose duration and extent are still controversial. This paper constrains their late thermal imprints. New and previously published zircon (ZFT) and apatite (AFT) fission-track ages show cooling below 240 °C of the metamorphic western AVAZ imbricates between 102 and 93–90 Ma, of northern Pelagonia between 86 and 68 Ma, of the eastern AVAZ at 80 Ma and of the western Rhodope at 72 Ma. At the regional scale, this heterogeneous cooling is coeval with subsidence of Late Cretaceous marine basin(s) that unconformably covered the Early Cretaceous (130–110 Ma) thrust system from 100 Ma. Thrusting resumed at 70 Ma in the AVAZ and migrated across Pelagonia to reach the External Hellenides at 40–38 Ma. Renewed thrusting in Pelagonia is attested at 68 Ma by abrupt and rapid cooling below 240 °C and erosion of the gneissic rocks. ZFT and AFT in western and eastern Pelagonia, respectively, testify at ~40 Ma to the latest thermal imprint related to thrusting. Central-eastern Pelagonia cooled rapidly and uniformly from 240 to 80 °C between 24 and 16 Ma in the footwall of a major extensional fault. Extension started even earlier, at ~33 Ma in the western AVAZ. Post-7 Ma rapid cooling is inferred from inverse modeling of AFT lengths. It occurred while E–W normal faults were cutting Pliocene-to-recent sediment.

scholarly journals Polyphase evolution of Pelagonia (northern Greece) revealed by geological and fission-track data

2014 ◽  
Vol 6 (2) ◽  
pp. 3075-3109 ◽  
Author(s):  
F. L. Schenker ◽  
M. G. Fellin ◽  
J.-P. Burg
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Fission Track ◽  
Regional Scale ◽  
Normal Faults ◽  
Recent Sediment ◽  
Northern Greece ◽  
Rapid Cooling ◽  
Basement Rocks ◽  
Fission Track Ages

Abstract. The Pelagonian zone, between the External Hellenides/Cyclades to the west and the Axios/Vardar/Almopia zone (AVAZ) and Rhodope to the east, was involved in late Early Cretaceous and in Late Cretaceous-Eocene orogenic events whose duration are still controversial. This work constrains their late thermal imprints. New and previously published zircon (ZFT) and apatite (AFT) fission-track ages show cooling below 240°C of the metamorphic western AVAZ imbricates between 102 and 93–90 Ma, of northern Pelagonia between 86 and 68 Ma, of the eastern AVAZ at 80 Ma and of western Rhodope at 72 Ma. At the regional scale, this heterogeneous cooling is coeval with subsidence of Late Cretaceous marine basin(s) that unconformably covered since 100 Ma the Early Cretaceous (130–110 Ma) thrust system. Thrusting restarted at 70 Ma in the AVAZ and migrated across Pelagonia to reach the External Hellenides at 40–38 Ma. Renewed thrusting in Pelagonia is attested at 68 Ma by abrupt and rapid cooling below 240°C and erosion of the basement rocks. ZFT and AFT in western and eastern Pelagonia, respectively, set at 40 Ma the latest thermal imprint related to thrusting. Central-eastern Pelagonia cooled rapidly and uniformly from 240 to 80°C between 24 and 16 Ma in the footwall of a major extensional fault. Extension started even earlier, at 33 Ma in the western AVAZ. Post-7 Ma rapid cooling is inferred from inverse modeling of AFT lengths. It occurred while E–W normal faults were cutting Pliocene-to-recent sediment.

scholarly journals Birth and closure of the Kallipetra Basin: Late Cretaceous reworking of the Jurassic Pelagonian–Axios/Vardar contact (northern Greece)

Solid Earth ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 2463-2485
Author(s):  
Lydia R. Bailey ◽  
Filippo L. Schenker ◽  
Maria Giuditta Fellin ◽  
Miriam Cobianchi ◽  
Thierry Adatte ◽  
...  
Keyword(s):  
Fission Track ◽  
Geothermal Gradient ◽  
Middle Part ◽  
Normal Faults ◽  
Illite Crystallinity ◽  
Northern Greece ◽  
Basin Inversion ◽  
Zircon Fission Track ◽  
Fission Track Ages ◽  
Fault Scarps

Abstract. Some 20 Myr after the Late Jurassic to Early Cretaceous obduction and collision at the eastern margin of Adria, the eroded Pelagonia (Adria)–Axios/Vardar (oceanic complex) contact collapsed, forming the Kallipetra Basin, described around the Aliakmon River near Veroia (northern Greece). Clastic and carbonate marine sediments deposited from the early Cenomanian to the end of the Turonian, with abundant olistoliths and slope failures at the base due to active normal faults. The middle part of the series is characterized by red and green pelagic limestones, with a minimal contribution of terrigenous debris. Rudist mounds in the upper part of the basin started forming on the southwestern slope, and their growth competed with a flux of ophiolitic debris, documenting the new fault scarps affecting the Vardar oceanic complex (VOC). Eventually, the basin was closed by overthrusting of the VOC towards the northeast and was buried and heated up to ∼ 180 ∘C. A strong reverse geothermal gradient with temperatures increasing up-section to near 300 ∘C is recorded beneath the VOC by illite crystallinity and by the crystallization of chlorite during deformation. This syntectonic heat partially reset the zircon fission track ages bracketing the timing of closure just after the deposition of the ophiolitic debris in the Turonian. This study documents the reworking of the Pelagonian–Axios/Vardar contact, with Cenomanian extension and basin widening followed by Turonian compression and basin inversion. Thrusting occurred earlier than previously reported in the literature for the eastern Adria and shows a vergence toward the northeast, at odds with the regional southwest vergence of the whole margin but in accordance to some reports about 50 km north.

Fast extension but little exhumation: the Vari detachment in the Cyclades, Greece

2003 ◽  
Vol 140 (3) ◽  
pp. 245-252 ◽  
Author(s):  
UWE RING ◽  
STUART N. THOMSON ◽  
MICHAEL BRÖCKER
Keyword(s):  
Late Cretaceous ◽  
Fission Track ◽  
Regional Scale ◽  
Slip Rate ◽  
Aegean Sea ◽  
Apatite Fission Track ◽  
Rapid Cooling ◽  
Magmatic Arc ◽  
Zircon Fission Track

Markedly different cooling histories for the hanging- and footwall of the Vari detachment on Syros and Tinos islands, Greece, are revealed by zircon and apatite fission-track data. The Vari/Akrotiri unit in the hangingwall cooled slowly at rates of 5–15 °C Myr−1 since Late Cretaceous times. Samples from the Cycladic blueschist unit in the footwall of the detachment on Tinos Island have a mean zircon fission-track age of 10.0±1.0 Ma, which together with a published mean apatite fission-track age of 9.4±0.5 Ma indicates rapid cooling at rates of at least ∼60 °C Myr−1. We derive a minimum slip rate of ∼6.5 km Myr−1 and a displacement of <∼20 km and propose that the development of the detachment in the thermally softened magmatic arc aided fast displacement. Intra-arc extension accomplished the final ∼6–9 km of exhumation of the Cycladic blueschists from ∼60 km depth. The fast-slipping intra-arc detachments did not cause much exhumation, but were important for regional-scale extension and the formation of the Aegean Sea.

scholarly journals Tectonic domains and exhumation history of the Omineca Belt in southeastern British Columbia from 40Ar/39Ar thermochronology

2020 ◽  
Vol 57 (8) ◽  
pp. 918-946
Author(s):  
Ewan R. Webster ◽  
Douglas A. Archibald ◽  
David R.M. Pattison ◽  
Jessica A. Pickett ◽  
Joel C. Jansen
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Regional Scale ◽  
Metamorphic Rocks ◽  
Normal Faults ◽  
Canadian Cordillera ◽  
Data Set ◽  
Rapid Cooling ◽  
Central Domain ◽  
Eastern Domain

A large geochronological data set comprising 40Ar/39Ar and K–Ar (hornblende, muscovite, biotite, and K-feldspar), Rb–Sr (muscovite), fission track (zircon and apatite) and U–Pb (zircon and monazite) dates has been compiled for the southern Kootenay Arc and western Purcell anticlinorium in the Omineca Belt of the Canadian Cordillera in southeastern British Columbia. New 40Ar/39Ar data for hornblende, muscovite, biotite, and alkali feldspar are presented and combined with data from other studies. We integrate these data with recent advances in the geology of the region to define three partially fault-bounded domains with differing geological and exhumation histories, here termed the western, central, and eastern domains. The western domain is characterized by (1) late synkinematic Jurassic plutons with hornblende, muscovite, and biotite 40Ar/39Ar plateau dates between 170 and 165 Ma, some of which are within error of the U–Pb zircon dates for these plutons, and (2) late Early Cretaceous (118–102 Ma) plutons commonly with concordant mica 40Ar/39Ar plateau dates of a similar age range, indicating rapid cooling following emplacement of both suites. The central domain is bounded by regional-scale normal faults (Gallagher and Midge Creek faults, Blazed Creek/Next Creek faults, and Purcell Trench fault) and contains superposed Early and Late Cretaceous zones of Barrovian metamorphic rocks and several mid- to Late Cretaceous, post-kinematic plutons. The transition from the western domain into the central domain is characterized by 40Ar/39Ar mica age spectra showing a progression of increasing thermal overprinting. Along the north–south length of the central domain, biotite and muscovite yield Paleocene to Eocene K–Ar and 40Ar/39Ar plateau dates between 66 and 40 Ma. The eastern domain consists of (1) a southern portion that occurs in the hanging wall of the Purcell Trench fault, comprising mid-Cretaceous intrusions of the Bayonne magmatic suite emplaced into biotite zone metasedimentary rocks of the Mesoproterozoic Belt-Purcell Supergroup in the western Purcell anticlinorium, and (2) a northern portion that shows a continuous transition with the northern part of the central domain north of the terminus of the Purcell Trench fault. Cretaceous igneous rocks in the southern portion of the eastern and western domains have 40Ar/39Ar mica plateau dates that are <9 Myr younger than U–Pb zircon dates, indicating rapid cooling shortly after emplacement. 40Ar/39Ar step-heating reveals that there was a mid- to Late Cretaceous thermal disturbance in the eastern domain, possibly related to emplacement of younger plutons at deeper crustal levels and the Late Cretaceous Barrovian metamorphic event recorded in rocks of the central domain, such that biotite with dates <ca. 73 Ma yield plateau age spectra but those with older dates are disturbed. The new geochronology, combined with recent mapping and metamorphic studies, leads to the conclusion that the exhumation of the Barrovian metamorphic rocks of the central domain was a multi-stage process. The central domain experienced rapid tectonic decompression and minor pluton emplacement in the Late Cretaceous to early Paleocene (76–61 Ma) when the Cordilleran orogen was under regional contraction during which most of the exhumation occurred. Final exhumation in the footwall of Eocene normal faults was less significant and occurred between 53 and ca. 46 Ma when the Cordilleran orogen had transitioned to regional extension, by which time the three domains had attained a similar crustal level. These episodes of exhumation are similar to those found in other core complexes in the southern Canadian Cordillera and contiguous northern Idaho and Washington. The earlier episode is coincident with regional-scale, Late Cretaceous thrust faulting in the Foreland Belt of the Rocky Mountains. Eocene normal faulting and final exhumation of core complexes in the Omineca Belt mark the end of contraction in the Foreland Belt.

scholarly journals Burial and Exhumation History of the Lujing Uranium Ore Field, Zhuguangshan Complex, South China: Evidence from Low-Temperature Thermochronology

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 116
Author(s):  
Yue Sun ◽  
Barry P. Kohn ◽  
Samuel C. Boone ◽  
Dongsheng Wang ◽  
Kaixing Wang
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
South China ◽  
Thermal History ◽  
Fission Track ◽  
Thermal Evolution ◽  
Negative Relationship ◽  
The Tibetan Plateau ◽  
Uranium Ore ◽  
Production Area

The Zhuguangshan complex hosts the main uranium production area in South China. We report (U-Th)/He and fission track thermochronological data from Triassic–Jurassic mineralized and non-mineralized granites and overlying Cambrian and Cretaceous sandstone units from the Lujing uranium ore field (LUOF) to constrain the upper crustal tectono-thermal evolution of the central Zhuguangshan complex. Two Cambrian sandstones yield reproducible zircon (U-Th)/He (ZHe) ages of 133–106 Ma and low effective uranium (eU) content (270–776 ppm). One Upper Cretaceous sandstone and seven Mesozoic granites are characterized by significant variability in ZHe ages (154–83 Ma and 167–36 Ma, respectively), which show a negative relationship with eU content (244–1098 ppm and 402–4615 ppm), suggesting that the observed age dispersion can be attributed to the effect of radiation damage accumulation on 4He diffusion. Correspondence between ZHe ages from sandstones and granites indicates that surrounding sedimentary rocks and igneous intrusions supplied sediment to the Cretaceous–Paleogene Fengzhou Basin lying adjacent to the LUOF. The concordance of apatite fission track (AFT) central ages (61–54 Ma) and unimodal distributions of confined track lengths of five samples from different rock units suggest that both sandstone and granite samples experienced a similar cooling history throughout the entire apatite partial annealing zone (~110–60 °C). Apatite (U-Th-Sm)/He (AHe) ages from six non-mineralized samples range from 67 to 19 Ma, with no apparent correlation to eU content (2–78 ppm). Thermal history modeling of data suggests that the LUOF experienced relatively rapid Early Cretaceous cooling. In most samples, this was followed by the latest Early Cretaceous–Late Cretaceous reheating and subsequent latest Late Cretaceous–Recent cooling to surface temperatures. This history is considered as a response to the transmission of far-field stresses, involving alternating periods of regional compression and extension, related to paleo-Pacific plate subduction and subsequent rollback followed by Late Paleogene–Recent India–Asia collision and associated uplift and eastward extrusion of the Tibetan Plateau. Thermal history models are consistent with the Fengzhou Basin having been significantly more extensive in the Late Cretaceous–Early Paleogene, covering much of the LUOF. Uranium ore bodies which may have formed prior to the Late Cretaceous may have been eroded by as much as ~1.2 to 4.8 km during the latest Late Cretaceous–Recent denudation.

scholarly journals The Tectonic event of the Zaire-Hala’alate thrust belt in Junggar Basin,China

2021 ◽  
Vol 937 (4) ◽  
pp. 042090
Author(s):  
Jinghui Ma ◽  
Lishang Nie ◽  
Changcheng Han
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Thermal History ◽  
Fission Track ◽  
Junggar Basin ◽  
Tectonic Activity ◽  
Thrust Belt ◽  
Tectonic Event ◽  
Intensity Effect ◽  
Activity Intensity

Abstract The Yanshanian tectonic activity intensity effect of The Zaire- Hala’alate thrust belt, which is located in the northwest margin of Junggar Basin, have been in dispute for a long time. The distribution characteristics of the FT peak age in the narrower time domain is the key to understanding the dynamic mechanism of this important intracontinental deformation. In this study, apatite fission track dating and thermal history simulation analysis were carried out on 6 samples collected from this area. The results show that the fission track ages are mainly distributed in three intervals, corresponding to the geological ages of 130∼128Ma, 92∼89Ma and 72Ma, reflecting the obvious cooling and uplifting events in the three periods. At the same time, the thermal history simulation shows that the region experienced three rapid uplift events in the Early Cretaceous, the Early Late Cretaceous and the Late Cretaceous-Eocene. The comprehensive study shows that the main thrust fold in this area started from the end of Early Cretaceous, and the tectonic movement was the most intense in Late Cretaceous. As a whole, Tectonic activity migrated from south to north, which shows a retro-thrust expansion from the basin to the orogenic belt.

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