Age of xenocrystic zircon from diatremes of western Canada

1991 ◽  
Vol 28 (8) ◽  
pp. 1232-1238 ◽  
Author(s):  
R. R. Parrish ◽  
I. Reichenbach
Keyword(s):  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Late Paleozoic ◽  
Western Canada ◽  
Magmatic Activity ◽  
Early Paleozoic ◽  
Lower Paleozoic ◽  
Single Zircon ◽  
Crustal Xenoliths ◽  
Middle Proterozoic

Numerous diatremes of middle and late Paleozoic age intrude miogeoclinal middle and lower Paleozoic strata in the Canadian Cordillera. In addition to abundant crustal xenoliths and conspicuous mantle-derived mineral xenocrysts, rare zircon grains are present. U–Pb dating of single zircon crystals from many of these diatremes has failed to identify the presence of cogenetic (magmatic) zircons. All dated zircon grains are interpreted as xenocrysts derived from the crust. Their morphologies range from euhedral to very rounded, and their ages range from early Paleozoic to Archean. Most ages fall between 1.8 and 2.1 Ga, with subordinate age groupings in the late Archean (ca. 2.6 Ga), Middle Proterozoic (1.0–1.1 Ga), and early Paleozoic (ca. 470 Ma, 530 Ma). The Proterozoic and Archean zircons could have been derived from either the crystalline basement or its overlying sedimentary cover of Late Proterozoic to early Paleozoic age. Paleozoic zircons were probably derived from either intrusions within the basement or sills that intrude the early Paleozoic sedimentary cover, and they signify magmatic activity possibly related to rifting of the continental margin.

Infrastructure des Alpes et tremblement de terre du 25 janvier 1946 [with discussion]

1947 ◽  
Vol S5-XVII (1-3) ◽  
pp. 39-53 ◽  
Author(s):  
Nicolas Oulianoff
Keyword(s):  
Early Stage ◽  
Crystalline Basement ◽  
Late Paleozoic ◽  
Early Paleozoic ◽  
Hercynian Orogeny ◽  
The Alps

Abstract Distinguishes four structural complexes in the Alps, noting in particular that the crystalline basement is composed not only of Hercynian (late Paleozoic) masses but also of recrystallized material which had been subjected to extensive folding prior to emplacement of Hercynian granite massifs, probably during the Caledonian (early Paleozoic) orogeny rather than in an early stage of the Hercynian orogeny. The earthquake in the Valais region, Switzerland, was undoubtedly tectonic in origin, but whether it represented a continuation of Alpine movements or was caused by subsidence associated with isostatic readjustment of crustal blocks cannot yet be determined.

La tectonique et la geologie de la partie orientale du bouclier bresilien

1967 ◽  
Vol S7-IX (1) ◽  
pp. 147-152 ◽  
Author(s):  
Edison F. Suszczynski
Keyword(s):  
Lower Devonian ◽  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Early Paleozoic ◽  
Structural Trend ◽  
Coastal Basins ◽  
Geologic Processes ◽  
Age Determinations

Abstract The Brazilian shield comprises two separate units. The Precambrian crystalline basement, in the eastern part of the shield, is divided into three parts distinguished by their lithology, structural trend, and mineralizations. The sedimentary cover contains a folded series of formations ranging in age from terminal Precambrian to early Paleozoic and an unfolded series represented by sediments of lower Devonian to Tertiary age which were deposited in epicontinental, intracratonic, and coastal basins. Four phases are recognized in the evolution of the unfolded sedimentary series. The effects of geologic processes active in the Brazilian shield from the end of the Precambrian to the end of the Mesozoic have been observed in the Parnaba-Sao Francisco intracratonic geosyncline. Results of age determinations are reported.

scholarly journals Tracing Pre-Mesozoic Tectonic Sutures in the Crystalline Basement of the Protocarpathians: Evidence from the Exotic Blocks from Subsilesian Nappe, Outer Western Carpathians, Poland

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 571
Author(s):  
Jan Golonka ◽  
Aleksandra Gawęda ◽  
Anna Waśkowska ◽  
David Chew ◽  
Krzysztof Szopa ◽  
...  
Keyword(s):  
Crystalline Basement ◽  
Western Carpathians ◽  
Late Paleozoic ◽  
Magmatic Activity ◽  
Tectonic Zone ◽  
Nd Isotope ◽  
Crustal Component ◽  
Outer Western Carpathians ◽  
Carpathian Flysch ◽  
History Of

Pre-Mesozoic exotic crystalline blocks within the Outer Carpathian flysch have potential to unravel the nature of their eroded basement source(s) and to reconstruct the Paleozoic–Precambrian history of the Protocarpathians. Strongly tectonized Campanian–Maastrichtian grey marls in the Subsilesian Nappe of the Outer Western Carpathians in Poland contain a variety of different lithology types, including granitoids and andesites. Petrological investigations coupled with zircon and apatite U-Pb dating were performed on crystalline (subvolcanic) exotic blocks from a locality in the Subsilesian Nappe. U-Pb zircon dating yields magmatic crystallization ages of c. 293 Ma for the microgranitoid and c. 310 Ma for the andesite block, with inherited zircon cores yielding Archean, Paleoproterozoic, Mesoproterozoic and Cadomian ages. Whole rock trace element and Nd isotope data imply that the melt source was composed of a significant Neoproterozoic crustal component in both the microgranite and andesite. The Late Carboniferous–Permian magmatic activity likely continues outside the Carpathian Belt and can be linked to a Late Paleozoic transtensional zone, which is a continuation of the Lubliniec–Kraków Zone that extends under the Carpathians to Moesia. This Late Paleozoic transtensional zone was probably reactivated during the Late Cretaceous under a transpressional regime within the Żegocina tectonic zone, which caused the uplift of the Subsilesian Ridge and intensive erosion.

Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

2021 ◽  
Author(s):  
Evgenia Salin ◽  
Jeremy Woodard ◽  
Krister Sundblad
Keyword(s):  
Baltic Sea ◽  
Short Distance ◽  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Drill Core ◽  
The Baltic Sea ◽  
Baltic Sea Region ◽  
Drill Site ◽  
Southwestern Margin ◽  
The Baltic

AbstractGeological investigations of a part of the crystalline basement in the Baltic Sea have been performed on a drill core collected from the depth of 1092–1093 m beneath the Phanerozoic sedimentary cover offshore the Latvian/Lithuanian border. The sample was analyzed for geochemistry and dated with the SIMS U–Pb zircon method. Inherited zircon cores from this migmatized granodioritic orthogneiss have an age of 1854 ± 15 Ma. Its chemical composition and age are correlated with the oldest generation of granitoids of the Transscandinavian Igneous Belt (TIB), which occur along the southwestern margin of the Svecofennian Domain in the Fennoscandian Shield and beneath the Phanerozoic sedimentary cover on southern Gotland and in northwestern Lithuania. It is suggested that the southwestern border of the Svecofennian Domain is located at a short distance to the SW of the investigated drill site. The majority of the zircon population shows that migmatization occurred at 1812 ± 5 Ma, with possible evidence of disturbance during the Sveconorwegian orogeny.

Chapter 6 Conclusions, differences between the Jabal Akhdar and Saih Hatat domes and unanswered questions

10.1144/m54.6 ◽  
2021 ◽  
Vol 54 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Andreas Scharf ◽  
Frank Mattern ◽  
Mohammed Al-Wardi ◽  
Gianluca Frijia ◽  
Daniel Moraetis ◽  
...  
Keyword(s):  
Large Scale ◽  
Late Paleozoic ◽  
Future Research ◽  
Early Paleozoic ◽  
Chronological Order ◽  
Oman Mountains ◽  
Tectonic Events ◽  
Major Fault ◽  
Tethys Ocean ◽  
Semail Ophiolite

AbstractThis chapter provides the conclusions/outlines of the tectonics, affecting the Southeastern Oman Mountains, including the Jabal Akhdar and Saih Hatat domes. The main tectonic events include amongst others (1) Neoproterozoic rifting, (2) two distinct early Paleozoic compressive events, (3) large-scale open ‘Hercynian’ folding and formation of a pronounced unconformity during the late Paleozoic, (4) rifting preceding the opening of the Neo-Tethys Ocean during the late Paleozoic, (5) late Cretaceous obduction of the Semail Ophiolite and the response of the Arabian lithosphere as well as (6) post-obductional tectonics. Also of major geological significance are the three major glaciations (Sturtian, Marinoan and Late Paleozoic Gondwana glaciation) which have been recorded in the rocks of northern Oman. Moreover, major lithological, structural and metamorphic differences exist between the Jabal Akhdar and Saih Hatat domes. It appears likely that a major fault, striking parallel to the eastern margin of the Jabal Akhdar Dome, probably originating during Neoproterozoic terrain accretion, acted as a divide between both domes until present. This fault was multiple times reactivated and could explain the differences between the two domes. A catalogue of unanswered questions is included in chronological order to express that many geological aspects need further investigation and future research projects.

scholarly journals Influence of basement rocks on fluid evolution during multiphase deformation: the example of the Estamariu thrust in the Pyrenean Axial Zone

2020 ◽  
Author(s):  
Daniel Muñoz-López ◽  
Gemma Alías ◽  
David Cruset ◽  
Irene Cantarero ◽  
Cédric M. Jonh ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Normal Faults ◽  
Published Data ◽  
Fluid Migration ◽  
Rock Interaction ◽  
Fluid Chemistry ◽  
Vein Formation ◽  
Basement Rocks ◽  
Calcite Veins

Abstract. Calcite veins precipitated in the Estamariu thrust during two tectonic events decipher the temporal and spatial relationships between deformation and fluid migration in a long-lived thrust and determine the influence of basement rocks on the fluid chemistry during deformation. Structural and petrological observations constrain the timing of fluid migration and vein formation, whilst geochemical analyses (δ13C, δ18O, 87Sr/86Sr, clumped isotope thermometry and elemental composition) of the related calcite cements and host rocks indicate the fluid origin, pathways and extent of fluid-rock interaction. The first tectonic event, recorded by calcite cements Cc1a and Cc2, is related to the Alpine reactivation of the Estamariu thrust, and is characterized by the migration of meteoric fluids, heated at depth (temperatures between 56 and 98 °C) and interacted with crystalline basement rocks before upflowing through the thrust zone. During the Neogene extension, the Estamariu thrust was reactivated and normal faults and shear fractures with calcite cements Cc3, Cc4 and Cc5 developed. Cc3 and Cc4 precipitated from hydrothermal fluids (temperatures between 127 and 208 °C and between 102 and 167 °C, respectively) derived from crystalline basement rocks and expelled through fault zones during deformation. Cc5 precipitated from low temperature meteoric waters percolating from the surface through small shear fractures. The comparison between our results and already published data in other structures from the Pyrenees suggests that regardless of the origin of the fluids and the tectonic context, basement rocks have a significant influence on the fluid chemistry, particularly on the 87Sr/86Sr ratio. Accordingly, the cements precipitated from fluids interacted with crystalline basement rocks have significantly higher 87Sr/86Sr ratios (> 0.710) with respect to those precipitated from fluids that have interacted with the sedimentary cover (

scholarly journals Co-Seismic Deformation and Fault Slip Model of the 2017 Mw 7.3 Darbandikhan, Iran–Iraq Earthquake Inferred from D-InSAR Measurements

2019 ◽  
Vol 11 (21) ◽  
pp. 2521 ◽  
Author(s):  
Zicheng Huang ◽  
Guohong Zhang ◽  
Xinjian Shan ◽  
Wenyu Gong ◽  
Yingfeng Zhang ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Sedimentary Cover ◽  
Historical Seismicity ◽  
Crystalline Basement ◽  
Geometrical Parameters ◽  
Seismic Zone ◽  
Seismogenic Fault ◽  
Long Distance ◽  
Blind Thrust ◽  
Seismic Deformation

The 12 November 2017 Darbandikhan earthquake (Mw 7.3) occurred along the converence zone. Despite the extensive research on this earthquake, none of this work explained whether this earthquake rupture was limited to the thick sedimentary cover or it extends to the underlying crystalline basement rock (or both). Besides, whether this region will generate devastating earthquakes again and whether there is a one-to-one correlation between these anticlines and blind-reverse faults need further investigation. In this study, we derived the co-seismic interferograms from the Sentinel-1A/B data and successfully described the surface deformation of the main seismic zone. The fringe patterns of both the ascending and descending interferograms show that the co-seismic deformation is dominated by horizontal movements. Then, using the along- and across-track deformation fields of different orbits, we retrieved the three-dimensional deformation field, which suggests that the Darbandikhan earthquake may be a blind thrust fault close to the north–south direction. Finally, we inverted the geometrical parameters of the seismogenic fault and the slip distribution of the fault plane. The results show that the source fault has an average strike of 355.5° and a northeast dip angle of −17.5°. In addition, the Darbandikhan earthquake has an average rake of 135.5°, with the maximum slip of 4.5 m at 14.5 km depth. On the basis of the derived depth and the aftershock information provided by the Iranian Seismological Center, we inferred that this event primarily ruptured within the crystalline basement and the seismogenic fault is the Zagros Mountain Front Fault (MFF). The seismogenic region has both relatively low historical seismicity and convergent strain rate, which suggests that the vicinity of the epicenter may have absorbed the majority of the energy released by the convergence between the Arabian and the Eurasian plates and may generate Mw > 7 earthquakes again. Moreover, the Zagros front fold between the Lurestan Arc and the Kirkuk Embayment may be generated by the long-distance slippage of the uppermost sedimentary cover in response to the sudden shortening of the MFF basement. We thus conclude that the master blind thrust may control the generation of the Zagros front folding.

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