Oxygen isotope systematics of the Precambrian basement of Alberta: implications for Paleoproterozoic and Phanerozoic tectonics in northwestern Alberta

2000 ◽  
Vol 37 (11) ◽  
pp. 1611-1628 ◽  
Author(s):  
Ronald A Burwash ◽  
Thomas Chacko ◽  
Karlis Muehlenbachs ◽  
Youcef Bouzidi
Keyword(s):  
Oxygen Isotope ◽  
Sedimentary Basin ◽  
Tectonic Setting ◽  
Precambrian Basement ◽  
Regional Survey ◽  
Rock Interaction ◽  
Basement Faults ◽  
Basement Structures ◽  
Temperature Interaction ◽  
Seismic Reflection Profiles

We have conducted a regional survey of the oxygen isotope compositions of drill core samples from the Precambrian basement of the Alberta sedimentary basin. The majority of samples have whole-rock δ18O (SMOW) values between +7 and +11‰, as is typical of crustal rocks. However, there are also a significant number of samples with δ18O values less than +5‰. In these samples, high-grade minerals such as pyroxene, amphibole, and biotite commonly show retrograde alteration to chlorite and (or) epidote. The majority of low-δ18O samples are from a 250 x 50 km zone in northwestern Alberta, which we refer to as the Kimiwan isotope anomaly. The anomaly is significant in that the most reasonable explanation for generating such a laterally extensive zone of rocks, with δ18O values below +5‰, is through high-temperature interaction with surface-derived fluids in an extensional tectonic setting. We propose, therefore, that the low-δ18O samples define a hitherto unrecognized extensional zone in the Alberta basement. Available geochronological data indicate that fluid-rock interaction and associated 18O depletion occurred at ca. 1800 Ma. Oxygen and hydrogen isotope data on mineral separates from this zone indicate that the surface fluids responsible for 18O depletion were of meteoric origin. Seismic reflection profiles acquired during the Lithoprobe Alberta Basement Transect reveal the presence of basement faults spatially associated with the zone of 18O depletion. We propose that these faults were extensional in nature at ca. 1800 Ma. Periodic reactivation of these basement structures during the Phanerozoic played an important role in the development of faults in the overlying sedimentary basin.

Conceptual model of basement deformation beneath the Southern Atlassic front of Tunisia from gravity modeling, seismic reflection profiles and seismotectonic data

2021 ◽  
Author(s):  
Nesrine Frifita ◽  
Mohamed Gharbi ◽  
Kevin Mickus
Keyword(s):  
Seismic Reflection ◽  
Geological Mapping ◽  
Gravity Modeling ◽  
Basement Faults ◽  
Geophysical Study ◽  
Half Graben ◽  
Basement Structures ◽  
Tectonic Style ◽  
Basement Deformation ◽  
Seismic Reflection Profiles

<p>The nature of the basement beneath the Southern Atlassic front of Tunisia is relatively unknown. To study the basement, a geophysical study was undertaken using gravity, seismic reflection and seismicity data. Additionally, these data were used to determine the relationship and the tectonic environment between the known seismicity and basement structures under the Chotts fold belt and the surrounding basins. Based on 2.5D gravity modeling, 2D seismic reflection profiles and known geological mapping, the geometry of the basement was modeled as consisting of horsts,grabens and half-grabens. Specifically, the Sidi Mansour and El-Fejej basins are located on basement uplifts. The variations in the depths of the known earthquakes reveal that the deepest events occurred on basement faults beneath the Metlaoui and Sidi Mansour basins. While the surrounding anticlines within the northern Chotts range are probably inverted into graben and half-graben structures by both thin- and thick-skinned tectonic events. The geophysical findings indicate that the geometry of the basement to consist of a series of uplifted and downdropped regions, where the depth to basement increases from south to north and from east to west. This basement structure can explain the concentration of earthquakes in the northwestern portion of the study area by linking a reactivation of pre-existing east trending fault systems that formed during Alpine Orogeny. The results provide a coherent model showed a mixed thick and thin-skinned tectonic style was active within the study area. </p>

Investigation of links between Precambrian basement structure and Paleozoic strata in the Fort Worth basin, Texas, U.S.A., using high-resolution aeromagnetic (HRAM) data and seismic attributes

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. B157-B168 ◽  
Author(s):  
Olubunmi O. Elebiju ◽  
G. Randy Keller ◽  
Kurt J. Marfurt
Keyword(s):  
High Resolution ◽  
Seismic Attributes ◽  
Barnett Shale ◽  
Fort Worth ◽  
Precambrian Basement ◽  
Fort Worth Basin ◽  
The North ◽  
Basement Faults ◽  
Basement Structures ◽  
Muenster Arch

Effective hydraulic fracturing is critical for generating permeability within the Barnett Shale of the Fort Worth basin (FWB). Therefore, knowledge of the nature of the induced and natural fractures, faults, and collapse features that may form conduits to the underlying Ellenburger aquifer is vital. We use coherence and curvature seismic attributes, which are sensitive to faults, fractures, and collapse features, to map sedimentary features. We then integrate high-resolution aeromagnetic (HRAM) data with the seismic attributes extracted along the Ellenburger Formation and the top of basement from the north-central portion of the FWB, thereby linking features in the Precambrian basement to shallower sedimentary structures. HRAM-derived maps, designed to enhance basement structures, confirm that much of the sedimentary faulting is basement controlled. Specifically, attribute lineaments are aligned parallel to HRAM anomaly lineaments, consistent with regional tectonics. The northeast-southwest and northwest-southeast orientations of folds and faults in the sedimentary section parallel the northeast-trending Ouachita orogenic belt and the northwest-trending Muenster arch, which in turn correlate with reactivated Cambrian/late Precambrian basement faults. Mapping such features can aid in the design of the hydraulic fracture program and ability to predict structurally deformed areas of the basin.

scholarly journals Pervasive fluid-rock interaction in subducted oceanic crust revealed by oxygen isotope zoning in garnet

2021 ◽  
Vol 176 (7) ◽  
Author(s):  
Thomas Bovay ◽  
Daniela Rubatto ◽  
Pierre Lanari
Keyword(s):  
Oxygen Isotope ◽  
Western Alps ◽  
Large Contribution ◽  
Chemical Mapping ◽  
Rock Interaction ◽  
Rock Density ◽  
Chemical Zoning ◽  
Dehydration Reactions ◽  
Subducted Oceanic Crust ◽  
Eclogite Facies

AbstractDehydration reactions in the subducting slab liberate fluids causing major changes in rock density, volume and permeability. Although it is well known that the fluids can migrate and interact with the surrounding rocks, fluid pathways remain challenging to track and the consequences of fluid-rock interaction processes are often overlooked. In this study, we investigate pervasive fluid-rock interaction in a sequence of schists and mafic felses exposed in the Theodul Glacier Unit (TGU), Western Alps. This unit is embedded within metaophiolites of the Zermatt-Saas Zone and reached eclogite-facies conditions during Alpine convergence. Chemical mapping and in situ oxygen isotope analyses of garnet from the schists reveal a sharp chemical zoning between a xenomorphic core and a euhedral rim, associated to a drop of ~ 8‰ in δ18O. Thermodynamic and δ18O models show that the large amount of low δ18O H2O required to change the reactive bulk δ18O composition cannot be produced by dehydration of the mafic fels from the TGU only, and requires a large contribution of the surrounding serpentinites. The calculated time-integrated fluid flux across the TGU rocks is 1.1 × 105 cm3/cm2, which is above the open-system behaviour threshold and argues for pervasive fluid flow at kilometre-scale under high-pressure conditions. The transient rock volume variations caused by lawsonite breakdown is identified as a possible trigger for the pervasive fluid influx. The calculated schist permeability at eclogite-facies conditions (~ 2 × 10–20 m2) is comparable to the permeability determined experimentally for blueschist and serpentinites.

Isotopic data bearing on the origin of Mesozoic and Tertiary granitic rocks in the western United States

1984 ◽  
Vol 310 (1514) ◽  
pp. 743-753 ◽  
Keyword(s):  
Granitic Rocks ◽  
Precambrian Basement ◽  
Regional Survey ◽  
Regional Patterns ◽  
Peraluminous Granite ◽  
Isotopic Compositions ◽  
Geographic Coverage ◽  
Magma Flux ◽  
Archean Basement ◽  
Mantle Magma

A regional survey of initial Nd and Sr isotopic compositions has been done on Mesozoic and Tertiary granitic rocks from a 500 000 km 2 area in California, Nevada, Utah, Arizona, and Colorado. The plutons, which range in composition from quartz diorite to monzogranite, are intruded into accreted oceanic geosynclmal terrains in the west and north and into Precambrian basement in the east. Broad geographic coverage allows the data to be interpreted in the context of the regional pre-Mesozoic crustal structure. Initial Nd isotopic compositions exhibit a huge range, encompassing values typical of oceanic magmatic arcs and Archean basement. The sources of the magmas can be inferred from the systematic geographic variability of Nd isotopic compositions. The plutons in the accreted terrains represent mantle-derived magma that assimilated crust while differentiating at deep levels. Those emplaced into Precambrian basement are mainly derived from the crust. The regional patterns can be understood in terms of: (1) the flux of mantle magma entering the crust; (2) crustal thickness; and (3) crustal age. The mantle magma flux apparently decreased inland; in the main batholith belts purely crustal granitic rocks are not observed because the flux was too large. Inland, crustal granite is common because mantle magma was scarce and the crust was thick, and hot enough to melt. The values of peraluminous granite formed by melting of the Precambrian basement depend on the age of the local basement source.

scholarly journals Permian Triassic geologic evolution in the southern Kitakami Belt, Japan

1992 ◽  
Vol 6 ◽  
pp. 155-155
Author(s):  
Kotaro Kamada
Keyword(s):  
Middle Triassic ◽  
Sedimentary Basin ◽  
Tectonic Setting ◽  
Japan Sea ◽  
Passive Margin ◽  
Middle Permian ◽  
Asian Continent ◽  
Transform Faults ◽  
Magmatic Arc ◽  
The Japan Sea

Before opening of the Japan Sea, the Japanese islands were attached to the eastern margin of the Asian continent. The Southern Kitakami Belt is regarded as a micro-continent in an accretional complex of the islands, that accreted before the Early Cretaceous. But its tectonic setting and location between the belt and the Asian continent is still an unresolved argument.Permo-Triassic sequences in the Southern Kitakami Belt are composed of shallow to off-shore deposits. These deposits are composed of clastics, carbonates with volcaniclastics. But there was no volcanic activity in the belt in the Middle to Late Permian. From the viewpoint of the sedimentary character and history, the Middle Permian to Middle Triassic sequences differ from their previous and their following successions in the belt. And the sedimentary basin of Middle Permian to Middle Triassic was bounded by transform faults. Magmatic arc was replaced by passive margin as hinterland of the Southern Kitakami Belt during the Middle Permian to Middle Triassic. It means that the sedimentary basin moved from the margin of Yangtze Platform to Sino-Korean Platform at that time.

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