Joint spacing and distribution in deformation band shear zones

2003 ◽  
Vol 140 (1) ◽  
pp. 1-9 ◽  
Author(s):  
S. E. TINDALL ◽  
G. H. DAVIS
Keyword(s):  
Deformation Band ◽  
Shear Zones ◽  
Structural Features ◽  
Distribution Characteristics ◽  
Joint Spacing ◽  
Mechanical Stratigraphy ◽  
Sandstone Reservoirs

Tectonic joints localized within deformation band shear zones on the Kaibab uplift in Utah, USA, show the same spacing and distribution characteristics as joints controlled by primary lithological mechanical stratigraphy, despite the fact that deformation band shear zones are secondary structural features oblique to primary sedimentary layers. The spacing and distribution of joints that traverse deformation band shear zones are important factors in the permeability and connectivity of sandstone reservoirs compartmentalized by deformation band shear zones.

scholarly journals The tectonostratigraphic architecture of the Serbo-Macedonian massif in the Vertiskos and Kerdilion mountains (Northern Greece)

2021 ◽  
Vol 57 (1) ◽  
pp. 1
Author(s):  
Anastasios Plougarlis ◽  
Markos Tranos ◽  
Lambrini Papadopoulou
Keyword(s):  
Cross Sections ◽  
Large Volume ◽  
General Trend ◽  
Shear Zones ◽  
Structural Features ◽  
Ultramafic Rocks ◽  
Northern Greece ◽  
Tectonic Contact ◽  
Western Side ◽  
Map Scale

The lithologies and structural features of the exposed rocks of the Serbo-Macedonian massif in the Vertiskos and Kerdilion Mts. have been studied in detail by carrying out km-long cross-sections. Moreover, a new tectonostratigraphic architecture for the massif is proposed, based on the migmatization and anatexis that the rocks pertain, under which the specific exposed rocks have been placed into the Vertiskos and Kerdilion Units. The latter approach differs from the traditional view, which is based solely on the lithological difference between the units. In particular, in the Vertiskos Mt., mica schists, garnet-bearing two-mica gneisses, and predominantly two-mica gneisses, without a sign of anatexis and migmatization, overlie tectonically, biotite gneisses and layered amphibolite gneisses into which migmatization and anatexis takes place. The former constitute the Vertiskos Unit, whereas the latter have been grouped into the Kerdilion Unit, since they are of similar lithologies and affinities with rocks of the Kerdilion Unit. The Kerdilion Mt. is a large antiform made up of biotite gneisses alternating with marbles, which are similarly characterized by intense migmatization and anatexis. These rocks are intruded by the Oreskia granite, which is foliated and follows the general trend of the country rocks. All the rocks are folded with isoclinal to tight folds, and the contact between the two units is a mylonitic shear zone with a top-to-the-SW sense-of-shear. Also, a large volume of ultramafic rocks occurs between the Vertiskos and Kerdilion Mts., including metamorphosed rocks like metagabbros to massive amphibolites, which is assigned to the Therma-Volvi-Gomati Complex (TVGC). These rocks have been found in tectonic contact, i.e., shear zones with top-to-the-SW sense-of-shear, only with the rocks of the Kerdilion Unit. Taking into account our new tectonostratigraphic architecture, the contact between the Vertiskos and Kerdilion Units is not located along the western side of the marbles, as the latter are exposed in the Kerdilion Mt. It is traced westerly in the Vertiskos Mt. dipping with intermediate angles towards the SW, due to NW-trending, map-scale, isoclinal folding. The ultramafic rocks of the TVGC are in tectonic contact with the rocks of the Kerdilion Unit, but not the two-mica gneisses of the Vertiskos Unit, and the Arnea granite intrudes not only the Vertiskos Unit as previously considered, but the rocks of the Kerdilion Unit, as well.

scholarly journals The Moroccan Massive Sulphide Deposits: Evidence for a Polyphase Mineralization

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 156 ◽  
Author(s):  
Abderrahim Essaifi ◽  
Kathryn Goodenough ◽  
Fernando Tornos ◽  
Abdelhak Outigua ◽  
Abdelmalek Ouadjou ◽  
...  
Keyword(s):  
Lead Isotopes ◽  
Shear Zones ◽  
Structural Features ◽  
Isotopic Signature ◽  
Ore Deposits ◽  
Massive Sulphide ◽  
Isotopic Signatures ◽  
Crustal Block ◽  
Massive Sulphide Deposits ◽  
Sulphide Deposits

This work provides an overview of the geological, geochemical, and metallogenic data available up to date on the Moroccan massive sulphide deposits, including some new results, and then discusses the evidences for the epigenetic and syngenetic hypotheses. All of the ore deposits are located within a crustal block located at the intersection between two major shear zones and are characterized by a sustained and long-lived magmatic activity. The ore deposits are located within second-order shear zones, which played an important role in controlling the geometry of the mineralization. The mineralization lacks the unequivocal textural and structural features that are indicative of a sedimentary or diagenetic origin, and a syntectonic to late-tectonic pyrite-rich assemblage is superimposed on an earlier, pretectonic to syntectonic pyrrhotite-rich mineralization. Each deposit has a distinctive pyrrhotite sulfur isotopic signature, while the sulfur isotopic signature of pyrite is similar in all deposits. Lead isotopes suggest a shift from a magmatic source during the pyrrhotite-rich mineralization to a source that is inherited from the host shales during the pyrite-rich mineralization. The O/H isotopic signatures record a predominance of fluids of metamorphic derivation. These results are consistent with a model in which an earlier pyrrhotite-rich mineralization, which formed during transtension, was deformed and then remobilized to pyrite-rich mineralization during transpression.

scholarly journals Engineering Geological and Geotechnical Approaches for the Construction of Powerhouse Cavern of Tehri Pumped Storage Plant (1000 MW) - A Case Study

2019 ◽  
Vol 24 ◽  
pp. 35-44
Author(s):  
Rajeev Prasad ◽  
Nishith Sharma
Keyword(s):  
Underground Structure ◽  
Shear Zones ◽  
Structural Features ◽  
Geological Mapping ◽  
Left Bank ◽  
Rock Composition ◽  
Northern India ◽  
Set Up ◽  
Pumped Storage

Construction of underground Cavern in the Himalayan region is full of challenges and uncertainties. Experience has shown that construction in Himalayan regions requires good understanding of geology, adequate site investigations, proper design and selection of suitable construction methodology and technology. The most commonly encountered geological problems during excavation of underground structure in Hydroelectric Projects are, Fault/Thrust/Shear Zones squeezing and swelling, wedge block failure etc. Tehri Pumped Storage Plant (PSP) is located at the left bank of river Bhagirathi in the state of Uttarakhand in Northern India. This case study indicates about the geological challenges faced and their remedial measures during the construction of Tehri PSP Powerhouse Cavern having dimension of 203m x 24m x 58m.3D-geological mapping with 1:100 scales was carried out in excavated central drift of powerhouse to evaluate the rock composition, behavior of rock mass, structural features and further investigation to finalize the layout and orientation. During the investigation Sheared Phyllite with bands of thinly Phyllite Quartzite rock were encountered in the end portion of central drift of powerhouse which had posed a mammoth challenge in designing the powerhouse cavern. Keeping in view the recommendations of geotechnical experts and the design consultants, decision were made to shift the cavern further by 50 m to avoid Sheared Phyllite bands. The shifting of cavern led to the reorientation of structures like control room, service bay and location of units etc. This paper briefly describes the Engineering Geological and Geotechnical set up of powerhouse with proper investigation approaches and excavation sequences highlighting the importance of orientation and Sheared Phyllite Zone.

Distribution characteristics and controlling factors of vertical joint spacing in sand-mud interbedded strata

2019 ◽  
Vol 128 ◽  
pp. 103886 ◽  
Author(s):  
Han Bao ◽  
Yong Zhai ◽  
Hengxing Lan ◽  
Keke Zhang ◽  
Qun Qi ◽  
...  
Keyword(s):  
Controlling Factors ◽  
Distribution Characteristics ◽  
Joint Spacing ◽  
Vertical Joint

KINEMATICAL MODEL FOR FORMING THE SIMEAN LOW OF THE URALIAN FORELAND BASIN

2018 ◽  
pp. 23-32
Author(s):  
Al. V. Tevelev ◽  
I. A. Prudnikov ◽  
Ark. V. Tevelev ◽  
A. O. Khotylev ◽  
E. A. Volodina
Keyword(s):  
Foreland Basin ◽  
Shear Zones ◽  
Structural Features ◽  
The North ◽  
Lateral Extrusion ◽  
Kinematical Model

In this work we reported the structural features and mechanism of the formation of the Simskaya low of the Uralian foreland basin, besides the Karatau-Suleyman block as a whole. This block has the shape of a wedge, so with a general latitudinal compression, it experienced lateral extrusion to the north along the conjugated shear zones. This factor determined the local situation of meridional compression and latitudinal tension. In the central part of the block, the latitudinal stretching was compensated for by gradual deflection, which led to the formation of the Simskaya low.

Early Devonian sinistral strike-slip in the Caledonian basement of Oscar II Land advocates for escape tectonics as a major mechanism for Svalbard terranes assembly

2020 ◽  
Author(s):  
Grzegorz Ziemniak ◽  
Jarosław Majka ◽  
Maciej Manecki ◽  
Katarzyna Walczak ◽  
Pauline Jeanneret ◽  
...  
Keyword(s):  
Shear Zone ◽  
Barents Sea ◽  
Weighted Average ◽  
Shear Zones ◽  
Structural Features ◽  
Greenschist Facies ◽  
Western Boundary ◽  
Structural Development ◽  
Early Devonian ◽  
Mylonitic Foliation

<p>The Svalbard’s Southwestern Basement Province in contrary to the Northwestern and Eastern Basement Provinces is commonly correlated with the Pearya Terrane or Timanides and bears a complicated internal structure. Here, we present new data from Oscar II Land supporting the model of Svalbard’s Basement being divided into the Laurentia and Barentsia plates in the late-Caledonian period.</p><p>In Oscar II Land the enigmatic Müllerneset Formation is tectonically juxtaposed against the remaining greenschist facies metamorphosed basement. It consists of Mesoproterozoic to Neoproterozoic metapelites and metapsammites that experienced a polymetamorphic history. The progressive amphibolite facies event M1 of unknown age reached the pressure-temperatures conditions of 5-7 kbar at 500-560 °C. The subsequent greenschist facies overprint (M2) is associated with mylonitization strongly pronounced across the whole Müllerneset Formation. Mylonitic foliation S2 dips steeply to the SW and it is associated with a stretching lineation dipping moderately-to-shallowly to the SE. In the western part of the unit, monazite is growing within the S2 foliation and related shear bands mainly replacing allanite. Th-U-total Pb dating of homogenous monazite population yielded a weighted average age of 410 ± 7 Ma with MSWD = 0.26 and p = 0.997. In the western part, where mylonitic foliation is less prevalent, monazite growths within M1 porphyroblasts and within the S2 foliation. Th-U-total Pb dating revealed an array of ages between 480 – 280 Ma with no correlation of chemical or structural features allowing divisions into subgroups.</p><p>Dating results indicating an early Caledonian signal should be attributed to the progressive M1 event. Uniform monazite age of 410 ± 7 Ma in the western part represents the timing of the M2 greenschist facies overprint. Younger ages obtained in the eastern part suggest fluid related disturbance of Th-U-Pb system during late Caledonian, Ellesmerian and Eurekan events. The timing of monazite growth during the M2 event is identical with the 410 ± 2 Ma <sup>40</sup>Ar/<sup>39</sup>Ar cooling age reported by Dallmeyer (1989). Geochronological evidence combined with structural observations suggests that the Müllerneset Formation in the Early Devonian was tectonically exhumed on the NW-SE trending left-lateral strike- to oblique-slip shear zone. Similarly oriented tectonic zones within the Southwestern Basement Province, in the Berzeliuseggene unit and the Vimsodden-Kosibapasset Shear Zone are also of similar age. This set of anastomosing shear zones is roughly parallel to the proposed orientation of the suture between Barentsia and Laurentia (Gudlaugsson et al. 1998). The documented Early Devonian sinistral displacement may mark the western boundary of the Barentsia microplate laterally extruded during the final Caledonian collision in a style similar to present day Anatolian Plate escape.</p><p>This work is funded by NCN research project no. 2015/17/B/ST10/03114, AGH statutory funds 16.16.140.315 and RCN Arctic Field Grant no. 282546.</p><p>Dallmeyer, R. D. (1989). Partial thermal resetting of<sup> 40</sup>Ar/<sup>39</sup>Ar mineral ages in western Spitsbergen, Svalbard: possible evidence for Tertiary metamorphism. Geological Magazine, 126(5), 587-593.</p><p>Gudlaugsson, S. T., Faleide, J. I., Johansen, S. E., & Breivik, A. J. (1998). Late Palaeozoic structural development of the south-western Barents Sea. Marine and Petroleum Geology, 15(1), 73-102.</p>

Extension and transtension associated with strike-slip faults and its relation with aquifer potentials: a case study in Aravalli terrane (North Gujarat), India

2020 ◽  
Author(s):  
Rudra Mohan Pradhan ◽  
Tapas Kumar Biswal
Keyword(s):  
Complex Geometry ◽  
Fractured Rock ◽  
Primary Source ◽  
Structural Data ◽  
Shear Zones ◽  
Structural Features ◽  
Strike Slip ◽  
Normal Faults ◽  
Fold Belt ◽  
North Gujarat

<p>Fractured rock aquifers are one of the most difficult aquifers to characterize due to complex geometry and fracture network. In Aravalli terranes of North Gujarat, communities depend on basement rock aquifers as the primary source of water supply. The hydrogeology of these aquifers is poorly understood and the drinking/irrigation wells are frequently placed in this area with little appreciation of the fracture systems. Increasing water demand puts stress to explore groundwater from less reliable sources of basement rocks and hence, makes it vital to identify potential hydrogeological zones. Lineament studies are commonly used for targeting groundwater bearing zones in hard rock terrane and very often ignore the other important structural settings viz. extension, transtension etc. For the present study, structural data pertaining faults and fractures have been mapped through fieldwork and Electrical resistivity imaging (ERT) technique. The key objective of the study is to correlate the structural features (extensional and transtensional settings) with geophysical profiles and to find out potential hydrogeological zones from where water can be explored economically. The study area comes under the Ambaji basin of Aravalli-Delhi fold belt which is a Proterozoic fold belt running 700-800 km in NE-SW direction and situated in NW India. The Aravalli-Delhi fold belt had undergone multiple phases of deformation. In this area, three major sets of fractures are present and are oriented largely in WNW-ESE, NE-SW, and NW-SE direction. The WNW-ESE fracture is dextral in nature which has interpreted from the displacement of fold limbs. Further, these are right lateral en-echelon normal faults where NE-SW extension has been taken place. There is another set of fracture i.e. NW-SE which is due to stretching of strike-slip fault. The ductile shear zones in the area are also parallel to the NW-SE fracture set. The shear zones are opened-up due to extension and formed potential aquifers. ERT has been carried out along and across the fractures to understand the subsurface fracture geometry. The ERT shows deep sited fractures and low resistivity values at the cross-section of WNW-ESE faults with the shear zone. This concludes a strong correlation between different structural settings with potential aquifers which could be used for pumping as well as artificial recharge sites for long term sustainability.</p><p><strong>Keywords-</strong> Aravalli terrane, Aquifer, Extension, Fracture, ERT</p>

Acadian deformation in the shallow crust: an example from the Siluro-Devonian Arisaig Group, Avalon terrane, mainland Nova Scotia

2006 ◽  
Vol 43 (1) ◽  
pp. 71-81 ◽  
Author(s):  
James A Braid ◽  
J Brendan Murphy
Keyword(s):  
Nova Scotia ◽  
Shear Zones ◽  
Thrust Fault ◽  
Structural Features ◽  
Strike Slip ◽  
Normal Faults ◽  
Progressive Deformation ◽  
Acadian Orogeny ◽  
Shallow Crust ◽  
Dextral Strike Slip

The Silurian – Early Devonian Arisaig Group of the Avalon terrane in northern mainland Nova Scotia consists mainly of thinly bedded sandstones, siltstones, and shales deposited in a near shore environment. These strata were deformed in the middle Devonian to form regional northeast- to NNE-trending folds and record deformation processes in the shallow crust during the Acadian orogeny, one of the most regionally extensive orogenic events in the Canadian Appalachians. Structural features in the Arisaig Group are consistent with fold propagation associated with thrust fault geometry and coeval local extension recorded by a set of conjugate normal faults. Many outcrop-scale folds have sheared limbs and show evidence of a complex progressive deformation. Folding was predominantly accomplished by bulk rotation and flattening above thrust fault tips. Early structures (D1–D2) produced regional cylindrical folds, whereas later (D3a, D3b, D3c) structures produced conical folds. D1–D3 fold orientations show high variability, but are consistent with progressive deformation related to reactivation and coeval dextral strike-slip movement along the Hollow Fault. The style of deformation is compatible with models in which strain is partitioned into preexisting shear zones in the basement, with folds in the overlying Arisaig Group initiated above the tips of upward-propagating thrusts as second-order structures related to movement along those shear zones. Taken together, these data indicate that fold mechanisms and geometry in the shallow crust during the Acadian orogeny in mainland Nova Scotia may be related to dextral strike-slip along major faults in the basement and co-genetic upward-propagating thrusts that rotated and flattened overlying strata.

Mise à l'évidence et cinématique de la faille de La Guadeloupe, Appalaches du sud du Québec

1989 ◽  
Vol 26 (10) ◽  
pp. 1932-1943 ◽  
Author(s):  
Alain Tremblay ◽  
Pierre St-Julien ◽  
Jean-Yves Labbé
Keyword(s):  
New England ◽  
Shear Zones ◽  
Structural Features ◽  
Ductile Deformation ◽  
Axis Orientation ◽  
Show Evidence ◽  
Tectonic Transport ◽  
Microscopic Studies ◽  
Connecticut Valley ◽  
Western Side

In the Appalachians of southern Quebec, the contact between Siluro-Devonian rocks of the Connecticut Valley – Gaspé Synclinorium and the Cambro-Ordovician rocks of the Dunnage Zone is marked by an important thrust fault striking northwest, La Guadeloupe fault. This fault separates two stratigraphically distinct domains, but the regional deformations are related to the same orogenic period. In the Sherbrooke and Weedon areas, different structural features show evidence of La Guadeloupe fault and reveal its kinematics. The exposed rocks near the fault exhibit structures that indicate a strong deformation zone. The deformation includes well-developed stretching lineations and shearing zones. The ductile deformation is restricted to the Cambro-Ordovician rocks. Macroscopic and microscopic studies of samples from the shear zones related to La Guadeloupe fault reveal, systematically, a tectonic transport from southwest to northwest. This interpretation is supported by the quartz crystallographic c-axis orientation. In New England, La Guadeloupe fault seems to coincide with the Taconic unconformity, though a bifurcation of the pre-Silurian units exposed on the western side of this unconformity remains possible. In Quebec, the correlation and kinematics of La Guadeloupe fault extension towards the northeast are not completely understood. [Journal Translation]

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