Extreme Mesozoic Crustal Thinning in the Eastern Iberia Margin: The Example of the Columbrets Basin (Valencia Trough)

Tectonics ◽  
2018 ◽  
Vol 37 (2) ◽  
pp. 636-662 ◽  
Author(s):  
Nathalie Etheve ◽  
Geoffroy Mohn ◽  
Dominique Frizon de Lamotte ◽  
Eduard Roca ◽  
Julie Tugend ◽  
...  
Keyword(s):  
Crustal Thinning ◽  
Valencia Trough

scholarly journals Mechanical (de-)coupling of the lithosphere in the Valencia Trough (NW Mediterranean): what does it mean?

2003 ◽  
Vol 210 (1-2) ◽  
pp. 291-303 ◽  
Author(s):  
J.M. Gaspar-Escribano ◽  
M. ter Voorde ◽  
E. Roca ◽  
S. Cloetingh
Keyword(s):  
Nw Mediterranean ◽  
Valencia Trough

scholarly journals Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

2018 ◽  
Vol 55 (9) ◽  
pp. 1063-1078 ◽  
Author(s):  
Michelle J. Markley ◽  
Steven R. Dunn ◽  
Michael J. Jercinovic ◽  
William H. Peck ◽  
Michael L. Williams
Keyword(s):  
Shear Zone ◽  
Crustal Thickening ◽  
Boundary Zone ◽  
Grenville Province ◽  
Metamorphic History ◽  
Crustal Thinning ◽  
Tectonic Significance ◽  
History Of ◽  
Central Gneiss Belt ◽  
Scale Shear

The Central Metasedimentary Belt boundary zone (CMBbz) is a crustal-scale shear zone that juxtaposes the Central Gneiss Belt and the Central Metasedimentary Belt of the Grenville Province. Geochronological work on the timing of deformation and metamorphism in the CMBbz is ambiguous, and the questions that motivate our study are: how many episodes of shear zone activity did the CMBbz experience, and what is the tectonic significance of each episode? We present electron microprobe data from monazite (the U–Th–Pb chemical method) to directly date deformation and metamorphism recorded in five garnet–biotite gneiss samples collected from three localities of the CMBbz of Ontario (West Guilford, Fishtail Lake, and Killaloe). All three localities yield youngest monazite dates ca. 1045 Ma; most of the monazite domains that yield these dates are high-Y rims. In comparison with this common late Ottawan history, the earlier history of the three CMBbz localities is less clearly shared. The West Guilford samples have monazite grain cores that show older high-Y domains and younger low-Y domains; these cores yield a prograde early Ottawan (1100–1075 Ma) history. The Killaloe samples yield a well-defined prograde, pre- to early Shawinigan history (i.e., 1220–1160 Ma) in addition to some evidence for a second early Ottawan event. In other words, the answers to our research questions are: three events; a Shawinigan event possibly associated with crustal thickening, an Ottawan event possibly associated with another round of crustal thickening, and a late Ottawan event that resists simple interpretation in terms of metamorphic history but that coincides chronologically with crustal thinning at the base of an orogenic lid.

Reconnaissance seismic refraction-reflection surveys in northwestern New Mexico

1984 ◽  
Vol 74 (4) ◽  
pp. 1263-1274
Author(s):  
Lawrence H. Jaksha ◽  
David H. Evans
Keyword(s):  
New Mexico ◽  
Wave Velocity ◽  
Lower Crust ◽  
Seismic Waves ◽  
Seismic Refraction ◽  
Velocity Model ◽  
P Wave ◽  
Uppermost Mantle ◽  
P Wave Velocity ◽  
Crustal Thinning

Abstract A velocity model of the crust in northwestern New Mexico has been constructed from an interpretation of direct, refracted, and reflected seismic waves. The model suggests a sedimentary section about 3 km thick with an average P-wave velocity of 3.6 km/sec. The crystalline upper crust is 28 km thick and has a P-wave velocity of 6.1 km/sec. The lower crust below the Conrad discontinuity has an average P-wave velocity of about 7.0 km/sec and a thickness near 17 km. Some evidence suggests that velocity in both the upper and lower crust increases with depth. The P-wave velocity in the uppermost mantle is 7.95 ± 0.15 km/sec. The total crustal thickness near Farmington, New Mexico, is about 48 km (datum = 1.6 km above sea level), and there is evidence for crustal thinning to the southeast.

scholarly journals Crustal thickness of the Grenville orogen: A Mesoproterozoic Tibet?

Geology ◽  
2021 ◽  
Author(s):  
Adam Brudner ◽  
Hehe Jiang ◽  
Xu Chu ◽  
Ming Tang
Keyword(s):  
Crustal Thickness ◽  
Detrital Zircons ◽  
Crustal Thickening ◽  
Geochemical Data ◽  
Geochronological Data ◽  
Grenville Province ◽  
Crustal Thinning ◽  
Paleoenvironmental Evolution ◽  
Orogenic Plateau ◽  
St Lawrence River

The Grenville Province on the eastern margin of Laurentia is a remnant of a Mesoproterozoic orogenic plateau that comprised the core of the ancient supercontinent Rodinia. As a protracted Himalayan-style orogen, its orogenic history is vital to understanding Mesoproterozoic tectonics and paleoenvironmental evolution. In this study, we compared two geochemical proxies for crustal thickness: whole-rock [La/Yb]N ratios of intermediate-to-felsic rocks and europium anomalies (Eu/Eu*) in detrital zircons. We compiled whole-rock geochemical data from 124 plutons in the Laurentian Grenville Province and collected trace-element and geochronological data from detrital zircons from the Ottawa and St. Lawrence River (Canada) watersheds. Both proxies showed several episodes of crustal thickening and thinning during Grenvillian orogenesis. The thickest crust developed in the Ottawan phase (~60 km at ca. 1080 Ma and ca. 1045 Ma), when the collision culminated, but it was still up to 20 km thinner than modern Tibet. We speculate that a hot crust and several episodes of crustal thinning prevented the Grenville hinterland from forming a high Tibet-like plateau, possibly due to enhanced asthenosphere-lithosphere interactions in response to a warm mantle beneath a long-lived supercontinent, Nuna-Rodinia.

scholarly journals Fault reactivation by gas injection at an underground gas storage off the east coast of Spain

2019 ◽  
Author(s):  
Antonio Villaseñor ◽  
Robert B. Herrmann ◽  
Beatriz Gaite ◽  
Arantza Ugalde
Keyword(s):  
East Coast ◽  
Fault Plane ◽  
Source Parameters ◽  
Gas Injection ◽  
Focal Depth ◽  
Gas Storage ◽  
Fault Reactivation ◽  
Underground Gas Storage ◽  
Waveform Modeling ◽  
Valencia Trough

Abstract. During September–October of 2013 an intense swarm of earthquakes occurred off the east coast of Spain associated with the injection of the base gas in an offshore underground gas storage. Two weeks after the end of the injection operations, three moderate-sized earthquakes (Mw 4.0–4.1) occurred near the storage. These events were widely felt by the nearby population, leading to the indefinite shut-down of the facility. Here we investigate the source parameters (focal depth and mechanism) of the largest earthquakes in the sequence in order to identify the faults reactivated by the gas injection, and to help understand the processes that caused the earthquakes. Our waveform modeling results indicate that the largest earthquakes occurred at depths of 6–8 km beneath the sea floor, significantly deeper than the injection depth (~ 1800 m). Although we cannot undoubtedly discriminate the fault plane from the two nodal planes of the mechanisms, most evidence seems to favor a NW-SE striking fault plane. We propose that the gas injection reactivated unmapped faults in the Paleozoic basement, with regional orientation possibly inherited from the opening of the Valencia Trough.

Ti-substitution mechanism in plutonic oxy-kaersutite from the Larvik alkaline complex, Oslo rift, Norway

2004 ◽  
Vol 68 (4) ◽  
pp. 687-697 ◽  
Author(s):  
H. Satoh ◽  
Y. Yamaguchi ◽  
K. Makino
Keyword(s):  
Negative Correlation ◽  
Closed System ◽  
Mineral Chemistry ◽  
Formula Unit ◽  
Alkaline Complex ◽  
Crustal Thinning ◽  
Substitution Mechanism ◽  
Plutonic Complex ◽  
O Isotope ◽  
Ti Substitution

AbstractAmphibole in the Larvik alkaline plutonic complex in the Oslo rift, Norway, has Ti-rich compositions from edenite through pargasite to kaersutite, and has a large H+ deficiency (0.7–1.1 atoms per formula unit: a.p.f.u.) with a large oxy component in the amphibole OH– site (O2– = 2 – (OH + F + Cl) = 0.2–0.9 a.p.f.u.), similar to the mantle-derived kaersutites. Their compositions reveal a characteristically low Fe3+/(Fe3++Fe2+) ratio (<0.23) and a high F concentration (0.3–0.9 a.p.f.u.). Correlation with the Fe3+ ratio caused by Fe2+ + OH– = Fe3+ + O2– + 1/2H2 substitution is negligible, which is supported by H and O isotope compositions. A possible substitution, [6]Al3+ + OH– = [6]Ti4+ + O2– may be operative for Larvik kaersutites when the O2–/Ti is 1.0. A relatively larger O2–/Ti ratio (1.2—2.0) suggests an another kaersutite substitution mechanism, [6]R2+ + 2OH– = [6]Ti4+ + 2O2–, where [6]R2+ = Fe2+ + Mg + Mn. These effects might result in the limited O2–/Ti ratio value from 1.0 to 2.0.A negative correlation between Ti and F, suggesting F incorporation into kaersutite may diminish the O2–/Ti ratio, not only due to the occupation of this non-oxy species in the O3 site, but also due to F—Ti avoidance. Composition-dependent H and O isotope variations (δD = –106 to –71% and δ18O = 4.6–5.2%) suggest equilibrium in the closed-system magma with differentiation. The mineral chemistry of Larvik oxy-kaersutitic amphibole could reflect the crystallization in a closed-system magma during rifting with passive crustal thinning at the Oslo palaeorift.

The gravity field over the Ungava Bay region from satellite altimetry and new land-based data: implications for the geology of the area

1999 ◽  
Vol 36 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Hamid Telmat ◽  
Jean-Claude Mareschal ◽  
Clément Gariépy
Keyword(s):  
Satellite Altimetry ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Models ◽  
Crustal Thickening ◽  
Seismic Line ◽  
Crustal Thinning ◽  
Gravity Measurements ◽  
George River ◽  
Superior Craton

Gravity data were obtained along two transects on the southern coast of Ungava Bay, which provide continuous gravity coverage between Leaf Bay and George River. The transects and the derived gravity profiles extend from the Superior craton to the Rae Province across the New Quebec Orogen (NQO). Interpretation of the transect along the southwestern coast of Ungava Bay suggests crustal thickening beneath the NQO and crustal thinning beneath the Kuujjuaq Terrane, east of the NQO. Two alternative interpretations are proposed for the transect along the southeastern coast of the bay. The first model shows crustal thickening beneath the George River Shear Zone (GRSZ) and two shallow bodies correlated with the northern extensions of the GRSZ and the De Pas batholith. The second model shows constant crustal thickness and bodies more deeply rooted than in the first model. The gravity models are consistent with the easterly dipping reflections imaged along a Lithoprobe seismic line crossing Ungava Bay and suggest westward thrusting of the Rae Province over the NQO. Because no gravity data have been collected in Ungava Bay, satellite altimetry data have been used as a means to fill the gap in data collected at sea. The satellite-derived gravity data and standard Bouguer gravity data were combined in a composite map for the Ungava Bay region. The new land-based gravity measurements were used to verify and calibrate the satellite data and to ensure that offshore gravity anomalies merge with those determined by the land surveys in a reasonable fashion. Three parallel east-west gravity profiles were extracted: across Ungava Bay (59.9°N), on the southern shore of the bay (58.5°N), and onshore ~200 km south of Ungava Bay (57.1°N). The gravity signature of some major structures, such as the GRSZ, can be identified on each profile.

Finite difference forward modelling across the Tyrrhenian basin

2021 ◽  
Author(s):  
Chiara Nardoni ◽  
Luca De Siena ◽  
Fabio Cammarano ◽  
Elisabetta Mattei ◽  
Fabrizio Magrini
Keyword(s):  
Wave Propagation ◽  
Finite Difference ◽  
Wave Attenuation ◽  
Software Tool ◽  
Seismic Wave Propagation ◽  
Tyrrhenian Sea ◽  
Forward Modelling ◽  
Crustal Thinning ◽  
Energy Leakage ◽  
Radiative Transfer Equations

&lt;p&gt;Strong lateral variations in medium properties affect the response of seismic wavefields. The Tyrrhenian Sea is ideally suited to explore these effects in a mixed continental-oceanic crust that comprises magmatic systems. The study aims at investigating the effects of crustal thinning and sedimentary layers on wave propagation, especially the reverberating (e.g., Lg) phases, across the oceanic basin. We model regional seismograms (600-800 km) using the software tool OpenSWPC (Maeda et al., 2017, EPS) based on the finite difference simulation of the wave equation. The code simulates the seismic wave propagation in heterogeneous viscoelastic media including the statistical velocity fluctuations as well as heterogeneous topography, typical of mixed settings. This approach allows to evaluate the role of interfaces and layer thicknesses on phase arrivals and direct and coda attenuation measurements. The results are compared with previous simulations of the radiative-transfer equations. They provide an improved understanding of the complex wave attenuation and energy leakage in the mantle characterizing the southern part of the Tyrrhenian Sea and the Italian peninsula. The forward modelling is to be embedded in future applications of attenuation, absorption and scattering tomography performed with MuRAT (the Multi-Resolution Attenuation Tomography code &amp;#8211; De Siena et al. 2014, JVGR) available at https://github.com/LucaDeSiena/MuRAT.&lt;/p&gt;

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