scholarly journals Hydrothermalism Associeted To Ediacarian Volcanism Of Ait Sawn And Tissouktai (Eastern Anti- Atlas, Morocco)

2016 ◽  
Vol 12 (24) ◽  
pp. 316
Author(s):  
R. Zahour ◽  
G. Zahour ◽  
Y. Zerhouni ◽  
S. Alikouss ◽  
Z. Baroudi ◽  
...  
Keyword(s):  
Active Faults ◽  
Fault Reactivation ◽  
Tectonic Structures ◽  
Weathering Processes ◽  
South West ◽  
Field Investigations ◽  
Geochemical Study ◽  
Volcanic Facies ◽  
Basic Volcanic ◽  
Geological Formations

In the South East of Ouarzazate (south west of the Saghro massif, Anti Atlas) outcrop the geological formations of Ait Sawn and Tissouktai. These, attributed to the Ediacaran (or terminal Neoproterozoic), consist of basic volcanic facies, intermediate and acid intercalated with pyroclastics and epiclastic levels. This set is traversed locally by acidic veins. The rocks studied suffered intense weathering processes marked by the development of secondary minerals which are also formed in the hydrothermal veins and at the expense of the primary magmatic minerals and mesostasis. The main paragenesis of mineralisation consists of hematite, malachite, chalcocite, pyrite, barite, epidote, quartz, chlorite, calcite, albite, sericite and iron oxides. Paleogeography sector is governed by inherited active faults of the Pan African base. Magmatism studied seems to be guided by these tectonic lineaments during the terminal Proterozoic extension. The reactivation of these tectonic structures, after the Cambrian, and probably during the Variscan and / or Atlasic, is certain. Field investigations, supplemented by microscopic and geochemical study, indicate that much of the mineralization associated with volcanic Southwest Massif Saghro, is related to a hydrothermalisme contemporary with the stage of fault reactivation.

scholarly journals Active tectonic field for CO<sub>2</sub> Storage management: Hontomín onshore study-case (SPAIN)

2020 ◽  
Author(s):  
Raúl Pérez-López ◽  
José F. Mediato ◽  
Miguel A. Rodríguez-Pascua ◽  
Jorge L. Giner-Robles ◽  
Adrià Ramos ◽  
...  
Keyword(s):  
Strain Field ◽  
Safety Management ◽  
Co2 Storage ◽  
Strain Tensor ◽  
Active Faults ◽  
Strike Slip ◽  
Fault Analysis ◽  
Fault Reactivation ◽  
Reservoir Rock ◽  
Active Tectonic

Abstract. One of the concerns of underground CO2 onshore storage is the triggering of Induced Seismicity and fault reactivation. Hence, a comprehensive analysis of the tectonic parameters involved in the storage rock formation is mandatory for safety management operations. Unquestionably, active faults and seal faults depicting the storage bulk are relevant parameters to be considered. However, there is a lack of analysis of the active tectonic strain field affecting these faults during the CO2 storage monitoring. The advantage of reconstructing the tectonic field is the possibility to determine the strain trajectories and describing the fault patterns affecting the reservoir rock. In this work, we adapt a methodology of systematic geostructural analysis to the underground CO2 storage, based on the calculation of the strain field and defined by the strain field from kinematics indicators on the fault planes (ey and ex for the maximum and minimum horizontal shortening respectively). This methodology is based on statistical analysis of individual strain tensor solutions obtained from fresh outcrops. Consequently, we have collected 447 fault data in 32 field stations located within a 20 km radius. The understanding of the fault sets role for underground fluid circulation can also be established, helping for further analysis about CO2 leakage and seepage. We have applied this methodology to Hontomín onshore CO2 storage facilities (Central Spain). The geology of the area and the number of high-quality outcrops, made this site as a good candidate for studying the strain field from kinematics fault analysis. The results indicate a strike-slip tectonic regime with the maximum horizontal shortening with N160° E and N50º E trend for local regime, which activates NE–SW strike-slip faults and NE–SW compressional faults. A regional tectonic field was also recognized with N–S trend, which activates E–W compressional faults. Monitoring of E–W faults within the reservoir is suggested in addition with the possibility of obtaining focal mechanism solutions for micro earthquakes (M 

FEATURES OF LEAD AND ZINC METALLOGENY WITHIN THE YENISEI RIDGE

2020 ◽  
pp. 68-84
Author(s):  
S. M. Makeev ◽  
E. A. Muromtsev ◽  
V. A. Makarov ◽  
G. V. Belokonov
Keyword(s):  
Siberian Platform ◽  
Yenisei Ridge ◽  
Tectonic Structures ◽  
Ore Formation ◽  
Lead And Zinc ◽  
Location Patterns ◽  
Lead Zinc ◽  
Polymetallic Mineralization ◽  
The Relationship ◽  
Geological Formations

Information collected on deposits, ore occurrences, and lead and zinc mineralization points known within the Yenisei Ridge is provided. A summary of the latest data on the geology and metallogeny of lead and zinc in the region is presented. A brief description of the deposits is given and their ore formation typification is carried out. The position of deposits in a stratigraphic section, the relationship with geological formations and tectonic structures, and subsequent conclusions about deposit location patterns and metallogenic zonality of the area were examined. The position analysis of polymetallic mineralization in regional geophysical and geochemical field revealed the presence of lead → zinc → barium trend from the Ishimbinsk fault towards the Siberian platform and the potential discovery of economically significant polymetallic mineralization in the eastern Yenisei Ridge.

A geochemical study of Roman to early Byzantine Glass from Sagalassos, South-west Turkey

2005 ◽  
Vol 32 (2) ◽  
pp. 287-299 ◽  
Author(s):  
P. Degryse ◽  
J. Schneider ◽  
J. Poblome ◽  
M. Waelkens ◽  
U. Haack ◽  
...  
Keyword(s):  
South West ◽  
Geochemical Study ◽  
Early Byzantine

scholarly journals An active tectonic field for CO<sub>2</sub> storage management: the Hontomín onshore case study (Spain)

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 719-739
Author(s):  
Raúl Pérez-López ◽  
José F. Mediato ◽  
Miguel A. Rodríguez-Pascua ◽  
Jorge L. Giner-Robles ◽  
Adrià Ramos ◽  
...  
Keyword(s):  
Strain Field ◽  
Safety Management ◽  
Co2 Storage ◽  
Strain Tensor ◽  
Active Faults ◽  
Strike Slip ◽  
Fault Analysis ◽  
Fault Reactivation ◽  
Reservoir Rock ◽  
Active Tectonic

Abstract. One of the concerns of underground CO2 onshore storage is the triggering of induced seismicity and fault reactivation by the pore pressure increasing. Hence, a comprehensive analysis of the tectonic parameters involved in the storage rock formation is mandatory for safety management operations. Unquestionably, active faults and seal faults depicting the storage bulk are relevant parameters to be considered. However, there is a lack of analysis of the active tectonic strain field affecting these faults during the CO2 storage monitoring. The advantage of reconstructing the tectonic field is the possibility to determine the strain trajectories and describing the fault patterns affecting the reservoir rock. In this work, we adapt a methodology of systematic geostructural analysis to underground CO2 storage, based on the calculation of the strain field from kinematics indicators on the fault planes (ey and ex for the maximum and minimum horizontal shortening, respectively). This methodology is based on a statistical analysis of individual strain tensor solutions obtained from fresh outcrops from the Triassic to the Miocene. Consequently, we have collected 447 fault data in 32 field stations located within a 20 km radius. The understanding of the fault sets' role for underground fluid circulation can also be established, helping further analysis of CO2 leakage and seepage. We have applied this methodology to Hontomín onshore CO2 storage facilities (central Spain). The geology of the area and the number of high-quality outcrops made this site a good candidate for studying the strain field from kinematics fault analysis. The results indicate a strike-slip tectonic regime with maximum horizontal shortening with a 160 and 50∘ E trend for the local regime, which activates NE–SW strike-slip faults. A regional extensional tectonic field was also recognized with a N–S trend, which activates N–S extensional faults, and NNE–SSW and NNW–SSE strike-slip faults, measured in the Cretaceous limestone on top of the Hontomín facilities. Monitoring these faults within the reservoir is suggested in addition to the possibility of obtaining a focal mechanism solutions for micro-earthquakes (M<3).

scholarly journals The petrography and origin of gneisses, amphibolites and migmatites in the Qasigialik area, South-West Greenland

1970 ◽  
Vol 83 ◽  
pp. 1-70
Author(s):  
F Kalsbeek
Keyword(s):  
Alkali Feldspar ◽  
Mineralogical Composition ◽  
Gradual Change ◽  
General Introduction ◽  
Quartz Content ◽  
Modal Composition ◽  
Rock Types ◽  
South West ◽  
Basic Volcanic

The migmatites from a small area (approx. 200 km2) in SW Greenland are described with special attention to the modal composition of the different rock types. After a general introduction a description of the field relationships of the rocks is given. The leucosome of the migmatites consists of leucocratic veins which mostly have a quartz-dioritic to granodioritic composition; a typical melanosome has rarely been found. The paleosome consists of banded biotite gneisses, hornblende-biotite gneisses and amphibolites. In subordinate quantities occur anorthositic gneisses and garnet-rich gneisses and amphibolites. Spread throughout the area, homogeneous biotite gneisses occur, which locally form large masses, but generally occur as minor outcrops full of inclusions of banded gneisses and amphibolites. These homogeneous gneisses are generally hardly migmatized. The different rock types are petrographically described. Histograms of measured An contents of plagioclase in the different rocks are given. It is shown from a large number of modal analyses that there is a gradual change in plagioclase and quartz content from the banded biotite gneisses via the hornblende-biotite gneisses to the amphibolites (in part). Some of the amphibolites do not fit into this pattern, these amphibolites are also in other respects difierent from the others, among others through the presence of garnet and/or diopside. The homogeneous biotite gneisses may have a granodioritic composition, but the majority of the samples contain hardly any alkali feldspar and agree in modal composition with the banded biotite gneisses, but for a slightly higher amount of biotite in the latter. The leucocratic veins also have often a quartz-dioritic composition which agrees with most of the gneisses, but with a much lower content of dark minerals. The paper is concluded with a discussion of the origin of the difierent rock types, based on the data collected. Most of the rocks are thought to be formed by isochemical metamorphism of geosynclinal sediments. The banded biotite gneisses probably represent original sediments of greywacke to arkose type. Part of the amphibolites probably represent original basic volcanic and tufiaceous rocks, which may have undergone erosion, transport and sedimentation. The hornblende-biotite gneisses are thought to derive from mixtures of normal sediment with varying amounts of tufiaceous material. Alternative interpretations of the gneisses and amphibolites are discussed. The homogeneous gneisses may have formed from the metasediments by a process of homogenization and mobilization. The origin of the leucocratic veins is discussed. The mineralogical composition of the veins and the An content of the plagioclase seem to exclude an origin by anatexis in situ of the gneisses, but the evidence is not conclusive.

scholarly journals Igneous stratigraphy of Archaean anorthosite at Majorqap qâva, near Fiskenæsset, South-West Greenland

1975 ◽  
Vol 74 ◽  
pp. 1-27
Author(s):  
J.S Myers
Keyword(s):  
Volcanic Rocks ◽  
Major Group ◽  
Calcic Plagioclase ◽  
West Greenland ◽  
South West ◽  
Granitic Intrusions ◽  
Number Of Cycles ◽  
Basic Volcanic ◽  
Anorthosite Complex

Majorqap qâva provides one of the best preserved examples of a major group of anorthosites and associated gabbroic rocks which are characterised by extremely calcic plagioclase and are widespread throughout the Archaean complex of Greenland. The anorthosite outcrop is part of a sheet of layered igneous cumulates which were deposited in a number of cycles from magma intruded into basic volcanic rocks. It consists of six major units which in upward succession are: lower gabbro (10 m), ultramafic (30 m), lower leucogabbro (60 m), middle gabbro (40 m), upper leucogabbro (60 m), and anorthosite (200 m). The lower four units are considered to represent sequences of plagioclase-pyroxene, olivine-pyroxene, plagioclase, and plagioclase-pyroxene cumulates respectively, and the upper two units are plagioclase cumulates with intercumulus hornblende and plagioclase respectively. Plagioclase is the most abundant cumulus mineral and extensively occurs as equant crystals 2 to 10 cm in diameter. The anorthosite outcrop is enclosed by gneiss which was derived by deformation from sheetlike granitic intrusions younger than the anorthosite complex. The gneiss was more duetile and partly cushioned the anorthosite complex from the ravages of later deformation and metamorphism by absorbing a greater amount of strain and recrystallisation.

scholarly journals The role of basement-involved normal faults in the recent tectonics of western Taiwan

2016 ◽  
Vol 153 (5-6) ◽  
pp. 1166-1191 ◽  
Author(s):  
KENN-MING YANG ◽  
RUEY-JUIN RAU ◽  
HAO-YUN CHANG ◽  
CHING-YUN HSIEH ◽  
HSIN-HSIU TING ◽  
...  
Keyword(s):  
Active Faults ◽  
Foreland Basin ◽  
Normal Fault ◽  
Strike Slip ◽  
Fault Reactivation ◽  
Normal Faults ◽  
Thrust Belt ◽  
Structural Style ◽  
Fold And Thrust Belt ◽  
Recent Tectonics

AbstractIn the foreland area of western Taiwan, some of the pre-orogenic basement-involved normal faults were reactivated during the subsequent compressional tectonics. The main purpose of this paper is to investigate the role played by the pre-existing normal faults in the recent tectonics of western Taiwan. In NW Taiwan, reactivated normal faults with a strike-slip component have developed by linkage of reactivated single pre-existing normal faults in the foreland basin and acted as transverse structures for low-angle thrusts in the outer fold-and-thrust belt. In the later stage of their development, the transverse structures were thrusted and appear underneath the low-angle thrusts or became tear faults in the inner fold-and-thrust belt. In SW Taiwan, where the foreland basin is lacking normal fault reactivation, the pre-existing normal faults passively acted as ramp for the low-angle thrusts in the inner fold-and-thrust belt. Some of the active faults in western Taiwan may also be related to reactivated normal faults with right-lateral slip component. Some main earthquake shocks related to either strike-slip or thrust fault plane solution occurred on reactivated normal faults, implying a relationship between the pre-existing normal fault and the triggering of the recent major earthquakes. Along-strike contrast in structural style of normal fault reactivation gives rise to different characteristics of the deformation front for different parts of the foreland area in western Taiwan. Variations in the degree of normal fault reactivation also provide some insights into the way the crust embedding the pre-existing normal faults deformed in response to orogenic contraction.

scholarly journals Weathering Processes and Mechanisms Caused by Capillary Waters and Pigeon Droppings on Porous Limestones

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 18
Author(s):  
David Benavente ◽  
Marli de Jongh ◽  
Juan Carlos Cañaveras
Keyword(s):  
Chemical Effect ◽  
Salt Weathering ◽  
Capillary Water ◽  
Material Loss ◽  
Weathering Processes ◽  
Geochemical Study ◽  
Pigeon Droppings ◽  
Deterioration Process ◽  
Dehydration Processes ◽  
Physical And Chemical

This investigation studies the physical and chemical effect of salt weathering on biocalcarenites and biocalcrudites in the Basilica of Our Lady of Succour (Aspe, Spain). Weathering patterns are the result of salty rising capillary water and water lixiviated from pigeon droppings. Surface modifications and features induced by material loss are observable in the monument. Formation of gypsum, hexahydrite, halite, aphthitalite and arcanite is associated with rising capillary water, and niter, hydroxyapatite, brushite, struvite, weddellite, oxammite and halite with pigeon droppings. Humberstonite is related to the interaction of both types of waters. Analysis of crystal shapes reveals different saturation degree conditions. Single salts show non-equilibrium shapes, implying higher crystallisation pressures. Single salts have undergone dissolution and/or dehydration processes enhancing the deterioration process, particularly in the presence of magnesium sulphate. Double salts (humberstonite) have crystals corresponding to near-equilibrium form, implying lower crystallisation pressures. This geochemical study suggests salts precipitate via incongruent reactions rather than congruent precipitation, where hexahydrite is the precursor and limiting reactant of humberstonite. Chemical dissolution of limestone is driven mainly by the presence of acidic water lixiviated from pigeon droppings and is a critical weathering process affecting the most valuable architectural elements present in the façades.

scholarly journals Postglacial strain rate – stress paradox, example of the Western Alps active faults

2021 ◽  
Author(s):  
Juliette Grosset ◽  
Stéphane Mazzotti ◽  
Philippe Vernant
Keyword(s):  
Strain Rate ◽  
Active Faults ◽  
Western Alps ◽  
Fault Reactivation ◽  
Deformation Pattern ◽  
Isostatic Adjustment ◽  
Flexural Response ◽  
Coulomb Failure ◽  
Direct Corollary ◽  
Gnss Data

Abstract. The understanding of the origins of seismicity in intraplate regions is crucial to better characterize seismic hazards. In formerly glaciated regions such as Fennoscandia North America or the Western Alps, stress perturbations from Glacial Isostatic Adjustment (GIA) have been proposed as a major cause of large earthquakes. In this study, we focus on the Western Alps case using numerical modeling of lithosphere response to the Last Glacial Maximum icecap. We show that the flexural response to GIA induces present-day stress perturbations of ca. 1–2 MPa, associated with horizontal extension rates up to ca. 2.5 × 10−9 yr−1. The latter is in good agreement with extension rates of ca. 2 × 10−9 yr−1 derived from high-resolution geodetic (GNSS) data and with the overall seismicity deformation pattern. In the majority of simulations, stress perturbations induced by GIA promote fault reactivation in the internal massifs and in the foreland regions (i.e., positive Coulomb Failure Stress perturbation), but with predicted rakes systematically incompatible with those from earthquake focal mechanisms. Thus, although GIA explains a major part of the GNSS strain rates, it tends to inhibit the observed seismicity in the Western Alps. A direct corollary of this result is that, in cases of significant GIA effect, GNSS strain rate measurements cannot be directly integrated in seismic hazard computations, but instead require detailed modeling of the GIA transient impact.

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