Le magmatisme neogene betico-rifain et le couloir de decrochement trans-Alboran

1987 ◽  
Vol III (2) ◽  
pp. 257-267 ◽  
Author(s):  
Jean Hernandez ◽  
Francois Dominique de Larouziere ◽  
Jean Bolze ◽  
Pierre Bordet
Keyword(s):  
Shear Zone ◽  
Strike Slip ◽  
Alkaline Magmatism ◽  
Basin Evolution ◽  
Crustal Anatexis ◽  
Calc Alkaline ◽  
Alkali Basalts ◽  
Eastern Morocco ◽  
Extended Area ◽  
Late Tortonian

Abstract The Miocene basin evolution of southeastern Spain and eastern Morocco is linked to a "shear zone" elongated from SW across the Alboran Sea. In Spain the magmatism is mostly calc-alkaline (or K-rich calc-alkaline). Most of the products are locatred on strike-slip faults (Almeria-Cabo de Gata). Lavas of dacitic compositions are interpreted as products of crustal anatexis. During Messinian time, lamproites are erupted over an extended area. Later (Plio-Quaternary), alkali basalts are located near Cartagena. In Morocco, calc-alkaline magmatism is not as developed as in Spain; late Tortonian-Messinian volcanoes (Gourougou, Guilliz) have erupted of shoshonitic lavas. Alkali basalts are abundant and appear from the end of Messinian to Quaternary all over northwestern Africa. In the studied area, there are no chronological nor geochemical polarity of the magmatism according to the existence of a Miocene subduction. The association of the magmatism with tectonics and basin evolution shows that it is linked with their aperture. The structure of the lithosphere, as it appears from the geophysical data, shows the existence of two different crusts, separated by the western part of the "shear zone". Trans-Alboran calc-alkaline magmatism is clearly correlated with the activity of this "shear zone", from Miocene to present time.

Suture zones and importance of strike-slip faulting for Variscan geodynamic reconstructions of the External Crystalline Massifs of the western Alps

2009 ◽  
Vol 180 (6) ◽  
pp. 483-500 ◽  
Author(s):  
Stéphane Guillot ◽  
Silvia di Paola ◽  
René-Pierre Ménot ◽  
Patrick Ledru ◽  
Maria Iole Spalla ◽  
...  
Keyword(s):  
Shear Zone ◽  
Bohemian Massif ◽  
Western Alps ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Geodynamic Evolution ◽  
Central European ◽  
Back Arc ◽  
Eastern Domain ◽  
Geodynamic Reconstructions

Abstract This paper reviews the geodynamic evolution of the Belledonne, Grandes Rousses and Oisans massifs in the western Alps from Early Ordovician to Permian times. Three domains are distinguished. The eastern domain, which includes the NE Belledonne massif and the inner Oisans massif, records the subduction of the Central-European ocean along a NW dipping subduction zone. The western domain is marked by Cambro-Ordovician back-arc rifting (Chamrousse ophiolite) initiating the opening of the Rheic ocean. It was followed by Mid-Devonian obduction of the back-arc Chamrousse ophiolite, towards the NW in relation with the SE dipping subduction of the Saxo-Thuringian ocean. The central domain, including the SW part of the Belledonne massif, the Grandes Rousses massif and the outer Oisans massif, records the Devonian to Carboniferous orogenic activity that produced calc-alkaline magmatism, Mg-K granite intrusions and syn-collisional sedimentation related to Visean nappe stacking that we relate to the closure of the Saxo-Thuringian ocean. Based on tectonostratigraphic correlations we propose that these domains initially correspond to the northeastward extension of the Bohemian massif. During the late Carboniferous, the External Crystalline Massifs including Sardinia and Corsica were stretched towards the SW along the > 600 km long dextral External Crystalline Massifs shear zone. Offset of the Saxo-Thuringian and eo-Variscan suture zones from the Bohemian massif to the ECM suggests a possible dextral displacement of about 300 km along the ECM shear zone.

scholarly journals Geochemical and geochronological records of tectonic changes along a flat-slab arc-transform junction: Circa 30 Ma to ca. 19 Ma Sonya Creek volcanic field, Wrangell Arc, Alaska

Geosphere ◽  
2019 ◽  
Vol 15 (5) ◽  
pp. 1508-1538 ◽  
Author(s):  
Samuel E. Berkelhammer ◽  
Matthew E. Brueseke ◽  
Jeffrey A. Benowitz ◽  
Jeffrey M. Trop ◽  
Kailyn Davis ◽  
...  
Keyword(s):  
Basaltic Andesite ◽  
Volcanic Field ◽  
Strike Slip ◽  
Trace Element Geochemistry ◽  
Alkaline Magmatism ◽  
Shield Volcano ◽  
Calc Alkaline ◽  
Initial Alignment ◽  
The West ◽  
South Central

Abstract The Sonya Creek volcanic field (SCVF) contains the oldest in situ volcanic products in the ca. 30 Ma–modern Wrangell Arc (WA) in south-central Alaska, which commenced due to Yakutat microplate subduction initiation. The WA occurs within a transition zone between Aleutian subduction to the west and dextral strike-slip tectonics along the Queen Charlotte–Fairweather and Denali–Duke River fault systems to the east. New 40Ar/39Ar geochronology of bedrock shows that SCVF magmatism occurred from ca. 30–19 Ma. New field mapping, physical volcanology, and major- and trace-element geochemistry, coupled with the 40Ar/39Ar ages and prior reconnaissance work, allows for the reconstruction of SCVF magmatic evolution. Initial SCVF magmatism that commenced at ca. 30 Ma records hydrous, subduction-related, calc-alkaline magmatism and also an adakite-like component that we interpret to represent slab-edge melting of the Yakutat slab. A minor westward shift of volcanism within the SCVF at ca. 25 Ma was accompanied by continued subduction-related magmatism without the adakite-like component (i.e., mantle-wedge melting), represented by ca. 25–20 Ma basaltic-andesite to dacite domes and associated diorites. These eruptions were coeval with another westward shift to anhydrous, transitional-tholeiitic, basaltic-andesite to rhyolite lavas and tuffs of the ca. 23–19 Ma Sonya Creek shield volcano; we attribute these eruptions to intra-arc extension. SCVF activity was also marked by a small southward shift in volcanism at ca. 21 Ma, characterized by hydrous calc-alkaline lavas. SCVF geochemical compositions closely overlap those from the <13 Ma WA, and no alkaline lavas that characterize the ca. 18–10 Ma eastern Wrangell volcanic belt exposed in Yukon Territory are observed. Calc-alkaline, transitional-tholeiitic, and adakite-like SCVF volcanism from ca. 30–19 Ma reflects subduction of oceanic lithosphere of the Yakutat microplate beneath North America. We suggest that the increase in magmatic flux and adakitic eruptions at ca. 25 Ma, align with a recently documented change in Pacific plate direction and velocity at this time and regional deformation events in southern Alaska. By ca. 18 Ma, SCVF activity ceased, and the locus of WA magmatism shifted to the south and east. The change in relative plate motions would be expected to transfer stress to strike-slip faults above the inboard margin of the subducting Yakutat slab, a scenario consistent with increased transtensional-related melting recorded by the ca. 23–19 Ma transitional-tholeiitic Sonya Creek shield volcano between the Denali and Totschunda faults. Moreover, we infer the Totschunda fault accommodated more than ∼85 km of horizontal offset since ca. 18 Ma, based on reconstructing the initial alignment of the early WA (i.e., 30–18 Ma SCVF) and temporally and chemically similar intrusions that crop out to the west on the opposite side of the Totschunda fault. Our results from the SCVF quantify spatial-temporal changes in deformation and magmatism that may typify arc-transform junctions over similar time scales (>10 m.y.).

scholarly journals Migmatite and leucogranite in a continental-scale exhumed strike-slip shear zone: Implications for tectonic evolution and initiation of shearing

2021 ◽  
Author(s):  
Junyu Li ◽  
Shuyun Cao ◽  
Xuemei Cheng ◽  
Franz Neubauer ◽  
Haobo Wang ◽  
...  
Keyword(s):  
Shear Zone ◽  
Thermal State ◽  
Shear Zones ◽  
Strike Slip ◽  
Red River ◽  
Crustal Anatexis ◽  
Plate Convergence ◽  
Continental Scale ◽  
Geological Processes ◽  
Lower Crustal

Plutons within continental strike-slip shear zones bear important geological processes on late-stage plate transpression and continent-continent collision and associated lateral block extrusion. Where, when, and how intrusions and shearing along transpressional strike-slip shear zones respond to plate interactions, however, are often debated. In this study, we investigated migmatite associated leucogranite and pegmatite from the exhumed &gt;1000-km-long Ailao Shan-Red River left-lateral strike-slip shear zone in Southeast Asia that was active during India-Eurasia plate convergence. Most zircons from the migmatites and leucogranitic intrusions present inherited core-rim structure. The depletion of rare earth element patterns and positive Eu anomalies suggest that leucosomes and leucogranites are the result of crustal anatexis. Zircon rims from the foliated migmatites and leucogranites record U-Pb ages of 41−28 Ma, revealing the timing of the Cenozoic crustal anatexis event along this strike-slip shear zone. Ages of the magmatic zircons from the unfoliated pegmatites provide the timing of the termination of a high-temperature tectono-thermal event and ductile left-lateral shearing at 26−23 Ma. The Cenozoic crustal anatexis along the Ailao Shan-Red River strike-slip shear zone indicates that thickened crust underneath the shear zone involved previously subducted crust. We propose that the Cenozoic thermal state has an important effect on the crustal anatexis and thus on the rheological behavior of the lithosphere by thermal weakening, which plays an essential role in localizing the initiation of the deep-seated lower-crustal shear zone.

scholarly journals 207Pb-206Pb dating of magnetite, monazite and allanite in the central and northern Nagssugtoqidian orogen, West Greenland

2006 ◽  
Vol 11 ◽  
pp. 101-114 ◽  
Author(s):  
Henrik Stendal ◽  
Karsten Secher ◽  
Robert Frei
Keyword(s):  
Hydrothermal Activity ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Sulphide Deposit ◽  
Late Archaean ◽  
West Greenland ◽  
Isotopic Signatures ◽  
Source Characteristics ◽  
Isotopic Measurements

Pb-isotopic data for magnetite from amphibolites in the Nagssugtoqidian orogen, central West Greenland, have been used to trace their source characteristics and the timing of metamorphism. Analyses of the magnetite define a Pb-Pb isochron age of 1726 ± 7 Ma. The magnetite is metamorphic in origin, and the 1726 Ma age is interpreted as a cooling age through the closing temperature of magnetite at ~600°C. Some of the amphibolites in this study come from the Naternaq supracrustal rocks in the northern Nagssugtoqidian orogen, which host the Naternaq sulphide deposit and may be part of the Nordre Strømfjord supracrustal suite, which was deposited at around 1950 Ma ago. Pb-isotopic signatures of magnetite from the Arfersiorfik quartz diorite in the central Nagssugtoqidian orogen are compatible with published whole-rock Pb-isotopic data from this suite; previous work has shown that it is a product of subduction-related calc-alkaline magmatism between 1920 and 1870 Ma. Intrusion of pegmatites occurred at around 1800 Ma in both the central and the northern parts of the orogen. Pegmatite ages have been determined by Pb stepwise leaching analyses of allanite and monazite, and source characteristics of Pb point to an origin of the pegmatites by melting of the surrounding late Archaean and Palaeoproterozoic country rocks. Hydrothermal activity took place after pegmatite emplacement and continued below the closure temperature of magnetite at 1800– 1650 Ma. Because of the relatively inert and refractory nature of magnetite, Pb-isotopic measurements from this mineral may be of help to understand the metamorphic evolution of geologically complex terrains.

The relationship between potassic, calc-alkaline and Na-alkaline magmatism in South Italy volcanoes: A melt inclusion approach

2004 ◽  
Vol 220 (1-2) ◽  
pp. 121-137 ◽  
Author(s):  
Pierre Schiano ◽  
Robert Clocchiatti ◽  
Luisa Ottolini ◽  
Alessandro Sbrana
Keyword(s):  
Melt Inclusion ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
South Italy ◽  
The Relationship

Dextral strike-slip along the Kapıdağ shear zone (NW Turkey): evidence for Eocene westward translation of the Anatolian plate

2016 ◽  
Vol 105 (7) ◽  
pp. 2061-2073 ◽  
Author(s):  
Ercan Türkoğlu ◽  
Gernold Zulauf ◽  
Jolien Linckens ◽  
Timur Ustaömer
Keyword(s):  
Shear Zone ◽  
Strike Slip ◽  
Nw Turkey ◽  
Dextral Strike Slip

The Hidaka Shear Zone (Hokkaido, Japan): Genesis during a right-lateral strike-slip movement

Tectonics ◽  
1985 ◽  
Vol 4 (3) ◽  
pp. 289-302 ◽  
Author(s):  
Laurent Jolivet ◽  
Sumio Miyashita
Keyword(s):  
Shear Zone ◽  
Strike Slip ◽  
Lateral Strike Slip ◽  
Strike Slip Movement
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