XZ Section Research Articles

Road resuspension PM2.5 from two vehicles driving in parallel by CFD method: The characteristics and population exposure

Particulate matter (PM) from the road resuspension dust of vehicles driving can deteriorate urban air quality. The goal of our study was to develop a discrete phase model and sliding grid technology to simulate the distribution characteristics of resuspension PM2.5 from vehicle road dust, and to analyze PM2.5 exposure of drivers and pedestrians caused by resuspension dust. The results indicated that the maximum height of PM2.5 concentration at the XZ section at 1–10 s varied in a zigzag pattern, with the lowest at 3.37 m at 1 s and the highest at 5.85 m at 2 s. PM2.5 concentration diffusion presented a "two lungs within one bracket" shape at Z = −0.03 m section and PM2.5 was gradually diffused from the tire to the two sides of the vehicle at 1–10 s. PM2.5 concentration at y = 5.5 m line of X = −15 m section gradually decreased with ground height increasing. The average PM2.5 concentration at Z = 1.25 m section at 1–10 s was 1.86, 3.17, 6.85, 8.85, 12.78, 14.69, 16.64, 18.96, 21.50, and 22.98 μg/m3, respectively. The average PM2.5 concentration was directly proportional to the change in road dust mass flow rate. The range of PM2.5 concentration of points a (left driver), b (right driver), c1 (pedestrian standing still for 3 m on right side of right vehicle) and c2 (pedestrian walking at a speed of 1.5 m/s) were 0–49.8, 0–183.0, 0–16.5, and 0–59.8 μg/m3, and the time of the maximum PM2.5 concentration for a, b, c1, and c2 was 5, 6.5, 4.5 and 5 s, respectively. These results indicated that the driver of point b had the highest exposure concentration within 1–10 s, which was 5.8 times that of the driver of point a, 7.7, and 2.9 times that of pedestrians of points c1 and c2. These results can provide basic data for road dust emissions and population exposure risk management.

Research on PM2.5 road resuspension dust and its population exposure based on sliding grids

The vehicles driving causes resuspension of road dust, which deteriorates air quality and poses population health risks. Based on sliding grid technology, the distribution characteristics of resuspended PM2.5 generated from a single vehicle driving are studied, and its population exposure for drivers and pedestrians are analyzed. The results show that the concentration of PM2.5 at z = −0.03 m has a “double bracket” shape with one front and one back. The length of PM2.5 concentration distribution gradually increases from 6.825 m to 60.825 m for 1 to 10 s. The maximum height of resuspension PM2.5 increases from 3.16 m to 5.13 m from 1 to 3 s and shows a sawtooth pattern from 3 to 10 s, reaching its highest at 5.62 m at 9 s at the XZ section. The dust gradually rises from 1 to 4 s and the dust gradually spreads to both sides of the vehicle from 4 to 10 s at X = -15 m section. PM2.5 concentration for a, b, and c ranges at 0–59.0, 0–63.1and 0–39.2 μg/m3, respectively. The driver in point a poses the highest exposure concentration within 1–10 s, which is 2.1 times that of pedestrian b and 4.1 times that of pedestrian c.

“In-plane” site-specific FIB lamella extraction from deformed magnetite and the investigation of low angle grain boundaries under TEM

In this study a modus operandi to investigate site-specific nanostructures in thin films (lamellae) excavated “in-plane” across (sub)grain boundaries is presented. This is done by discussing the case of a magnetite grain hosted in a thin section of banded iron formation (Norway) that is prepared parallel to the kinematic reference frame (XZ section of the strain ellipsoid). SEM-EBSD analysis reveal that the magnetite grains do not develop a strong crystallographic preferred orientation, although individual grains are strained and show evidence of intracrystalline deformation in form of low angle grain boundaries (LAGB's). Two “in-plane” lamellae using focused ion beam (FIB) technique are excavated from a magnetite grain in the kinematic reference frame, and nanostructures are studied along three LAGB's using high resolution transmission electron microscopy imaging followed by Fourier transformation (FT), inverse FT and estimation of dislocation densities. Our data establish an empirical relationship for the studied LAGBs, namely, the smaller the angle between LAGB and X-direction, the larger are the shear strain and dislocation density. This relationship is validated from numerical simulations of viscoplastic deformation and dynamic recrystallisation of polycrystalline aggregates of halite, which is also a cubic mineral analogous to magnetite. In addition to the site-specific “in-plane” FIB lamella information, this study also shows that in a deformed mineral the different orientations of the LAGB compared to the principal strain axes show a different dislocation density. This approach of full tracking of the extension direction (X) from the macroscopic to the nano-scale could play an important role in forward modelling of microstructure evolution in future studies.

Microstructural and strain studies of neoproterozoic rocks encapsulating hammamat molasse deposits in theWadi El-Qash area, Central Eastern Desert, Egypt

Understanding deformational processes and related structures at various scales, necessitates an estimate of microstructural and finite strain characterization of deformed rocks. In the current research, 23 collected samples of metaconglomerates, metsediments, and metavolcanics from the Wadi El-Qash region, placed in the Central Eastern Desert of Egypt, were used to quantify the finite strain of quartz, feldspar porphyroclasts, and mafic grains. Finite strain techniques were utilized to produce and analyze 46 thin sections. The metaconglomerate rocks have undergone high to moderate grades of deformation, according to the strain results. Using the Rf/φ and the Fry techniques, the axial ratios in the XZ section vary from 2.20 to 5.40 and from 2.00 to 5.30, respectively. The strain results point out high to moderate rates of deformation of the metaconglomerates, metsediments, and metavolcanic rocks. The direction of finite strain in X axis exhibits shallow WNW dipping and grouping following an N-to-WNW trend in most of the measured samples. The subvertical and subhorizontal foliation related to the short axes in Z axis. The results show that contacts developed in semi-brittle to ductile deformation and the magnitude of strain is the same for all lithologic units that are exposed in the studied area. Also, these results contradict the generally accepted belief that simple-shear deformation is responsible for nappe development in orogens.

Opposite Shear Sense from Quartz Shape and Crystallographic Preferred Orientation – a Dichotomy and Its Implications for Kinematic Analysis

ABSTRACT The present paper is written to bring to light a dichotomy that is noted in a naturally deformed rock, where the sense of shear inferred from quartz shape preferred orientation (SPO) is opposite to that deciphered from the crystallographic preferred orientation (CPO). Microstructural and quartz CPO data (obtained through SEM-EBSD analysis) from a quartz vein hosted in sinistrally sheared mylonitized granite of Gadwal region (Dharwar Craton) are presented. The vein thin section is prepared parallel to the kinematic reference frame (XZ section of the strain ellipsoid) using field-based information, which allows determination of sense of shear using microstructures. Three domains viz. Domain-I, II and III are identified in the rock thin section with grain size being 300-180 µm, 70-35 µm, and <20 µm, respectively. Of these, quartz grains of Domain-II show a well-defined quartz oblique grain shape fabric, which is indicative of dextral sense of shear. However, quartz CPO from the same Domain-II, as well as Domains-I and III, consistently shows a sinistral sense of shear; the latter complements the kinematics noted from the host rock mylonite. The dichotomy noted from Domain-II indicates that there maybe pitfalls in direct interpretation of kinematics based exclusively on quartz SPO analysis. Hence, caution must be exercised while extrapolating microscale kinematics based on quartz SPO to the regional scale.

Structural evolution and Microstructural analysis for al Faydh area, southern Arabian shield, Saudi Arabia

Al Faydh area is a major significant tectonic structure in southwestern part of Arabian shield, and it was estimated using finite strain analysis and microstructural investigation. Our research focuses structural features of the Al Faydh area in order to obtain field identification and better comprehend the tectonic setting for studied region. The Rf/φ and Fry techniques were used the most of quartz and feldspar for felsic minerals and biotite and hornblende for mafic minerals. The axial ratios with the mean average about 1.09–1.83 (using Rf/φ method) and 1.13 to 1.95 (using the Fry method) in the XZ section for the collected samples of metavolcanic, metasedimentary and meta-granite (gneisses). The finite strain direction displays clustering with slight plunging along a W–E trend along the long axes. The Z axes are related the sub-vertical and sub-horizontal foliation. The majority results suggest oblate strain symmetry and there is noticeable rise in strain magnitudes toward the tectonic contacts. The volume change was related the accumulation of finite strain in the different lithologies during a polyphase deformation regime. Applying the finite strain and microstructural analysis data from Al Faydh region concluded that the structural contacts for different lithologies were generated during faults, plutonic intrusion and fracture zones. Also, the deformation in the Al Faydh region are formed under brittle to semi-ductile deformational with simple shearing.

Study of structural, deformation temperature, and strain analysis of the quartzarenites of south-central Kaladgi basin, exposed at and around Mullur ghat and Kallur village of Belgaum district, Karnataka, India

Kaladgi rocks are magnificently exposed in Belgaum district of Karnataka state, with adjacent to Maharashtra, the Kaladgi Basin, evolved as a consequence of crustal extension which are resting on the basement of the Archaean Gneisses and are also overlaid by Deccan Traps. The outcrops in the present study area have very well-exposed quartzarenites of south-central part of Kaladgi Basin. New meso- and microscale structural analyses indicate that Kaladgi rocks suffered at least two episodes of deformation preserved in ductile and ductile-brittle structures. Finite strain analyses of the XZ and YZ sections on the collected samples from the Kaladgi basin show pure flattening strain pattern on Hsu and Flinn diagram. This simple flattening strain is attributed due to the sedimentation or lithological loading in the basin. This study area traversed by 3 transverse faults, namely F1, F2, and F3 through K-1, K-5, and M-4 locations, respectively. Finite strain analyses show high strain value in XZ section along the faults as F1 show 1.32 to 1.44, F2 has 2.3 to 1.45, and F3 reflect 1.57 Rs values. Deformation temperature based on the microstructures has high value along the faults as 400 to 500°C; however, rest of the area show low temperature deformation <300°C. This study brings new insights on deformation structures in field and under a microscope.

Petrographic, structural and textural analysis of the Atuba Complex, Southern Ribeira Belt: Case study in the Greca quarry

The Greca quarry is located in the Colombo municipality, close to the Curitiba Shear Zone, south of the Lancinha Shear Zone in the State of Paraná. It is inserted in the Atuba Complex (Curitiba Terrane) and comprises the meridional portion of the Ribeira Belt. This work was carried out by means of field work, petrography, electron backscattered diffraction analysis and strain analysis using the Fry, Polar and Rf/φ methods. Thus, it aims to analyze meso and micro scale strain in tectonites in a key area of the Atuba Complex. The heterogeneous ductile strain observed at a microscopic and macroscopic scale resulted in stromatic, protomylonitic and mylonitic metatexites, of submillimetric to metric widths. The occurrence of quartz and leucocratic veins of centimetric to metric thickness is rare, either discordant or concordant to the foliation of migmatites. Two deformation phases were found, both derived from ductile shear: the first is associated with the thrusting tectonics (Dn-1); and the second has a sinistral transcurrent-transpressive nature (Dn). The presence of new quartz grains observed by subgrain rotation (SGR) recrystallisation and new grains by bulging (BLG) recrystallisation in the feldspar crystals indicates temperatures above 450 °C (lower amphibolite facies) during the shear of both phases. The strain analysis was generated based on the investigation of quartz crystals of 2 samples and 4 thin sections (XZ and YZ planes). The analyzes indicated approximate strain ratios (R) for all methods used in the XZ and YZ planes. Quartz presented values between 2.250 and 1.304 (XZ section) and 2.237 to 1.110 (YZ section). The ellipsoids are mainly oblate and are equivalent to the apparent flattening group. The tectonites are predominantly of S or SL type. According to the EBSD data, it was possible to identify that the strain occurred by dislocation creep mechanisms, associated with the dynamic recrystallisation processes. The samples analyzed by EBSD indicated that the feldspar crystals have poles (010) in the <001> direction and the quartz crystals show the activation of the basal sliding system with the aid of the rhombohedral system. The results also indicate low temperatures, probably due to the retrometamorphic event that occurred in the last strain stage of the Atuba Complex.

CPO and kinematic analysis of the Bitou S-tectonites (Central Cameroon shear zone): AMS and EBSD investigations

The development of foliation is not always associated with mineral stretching lineation in deformed rocks. Sometimes, S-tectonites only display foliation with no mineral stretching lineation, and it becomes a real challenge to perform kinematic analysis, i.e., to define the XZ section of the ellipsoid. In this study, we present in a portion of the Central Cameroon Shear Zone (CCSZ) (the Bitou biotite gneiss mylonite), the usefulness of anisotropy of magnetic susceptibility (AMS) studies to identify the three principal axes of the AMS ellipsoid (K1 ≤ K2 ≤ K3), equivalents respectively to the principal axes of the strain ellipsoid (X ≤ Y ≤ Z). The K1K3 plane of the AMS ellipsoid is equivalent to the XZ section of the strain ellipsoid. The fabrics developed in the studied mylonitised biotite gneiss strike ENE–WSW to E–W with steep dips for the mylonitic and magnetic foliations and moderate plunges for the magnetic lineation. The rock is paramagnetic. The AMS ellipsoids are mostly of oblate shape, while the quartz c-axis pattern is typical of non-coaxial flow. This implies that deformation partitioning took place during mylonitisation. Quartz crystallographic preferred orientation (CPO) measured using electron backscatter diffraction reveals the activation of prism <a> slip, implying that the mylonitisation occurs under moderate temperature conditions (450°C < T < 550°C). Microstructures observed in the K1K3 section of the AMS ellipsoid and CPO of the quartz c-axis indicate sinistral top-to-SW sense of shear. These results support the shear senses of movement that earlier studies in the CCSZ have emphasised and are assumed to be related to the early syn-D2 and D3 events of the Pan-African tectonic dated at ca. 613–585 Ma.

Microstructural Study and Strain Analysis of Deformed Neoproterozoic Lithologies in the Um Junud Area, Northern Nubian Shield

Estimation of finite strain and microstructural analysis of deformed rocks are keys to better understanding deformational processes and related structures in a variety of scales started from microscopic fabric development to regional-scale structures. In the present work, we carried out the quantitative calculation of strain using the Rf/φ and Fry methods for quartz, feldspar and mafic grains (e.g. biotite and hornblende) from twenty two collected samples for granitic gneiss, amphibolite and hornblende schist samples from the Um Junud area situated in south Eastern Desert of Egypt. Forty four thin sections were prepared and measured by using finite strain methods. The strain data indicate high to moderate ranges of deformation of the amphibolite to granitic rocks. The axial ratios in the XZ section range from 1.74 to 4.37 and 1.50 to 4.46 for the Rf/φ and the Fry methods respectively. The finite strain direction for the long axes displays clustering along N to WNW trend, and shallow WNW plunging in the majority of the studied samples. The short axes are found to be subvertical associated with a subhorizontal foliation. It is concluded that finite strain is of the same order of magnitude for various lithologic units outcropping in the area, and that contacts were formed under semi-brittle to semi-ductile deformation conditions. Thus, the finite strain accumulated during superimposed deformation on a previously nappe structure assemblage, which pointed out that these contacts were created during the accumulation of finite strain. This result is inconsistent with the generally believed that nappe creation in orogens carried out by simple shear deformation.

Strain analysis and deformation history of Zalm area, Arabian shield, Saudi Arabia

The present work deals with the strain analysis and deformation of the Zalm area which is located in the central part of the central Nabitah suture belt, which separates the continental Afif terrane from the ensimatic arc terranes of the western Arabian Shield. This study carried out through field investigation, strain parameters, and microscopic examination for understanding the nature of deformation in the Zalm area. On the basis of the field investigation and the geometry of the contact, it is more likely that the contact between ultramafic rocks and gabbroic rock complex is low-angle thrust faulting. The granitoid rocks are divided into the quartz monzodiorite, monzogranite, alkali-feldspar granite and leucocratic-granodiorite. The Rf/ϕ and Fry techniques on feldspar and mafic grains from 53 samples representative of each rock type were collected in the field. Strain data shows that the deformation of the granitic, metavolcanic and amphibole schist samples range from high to moderate. The axial ratios (XZ section) range from 1.60 to 4.10 for the Rf/ϕ method and 2.80 to 4.90 for the Fry method. Furthermore, the finite strain data does not dispay any significant difference in the deformation behavior between Rf/ϕ and Fry methods. We concluded that the strain magnitude has the same order of deformation in the deformed granitoid and amphibole schist rocks. The majority of samples are in a zone of flattening symmetry, while a few samples are showing constrictional symmetry. In addition, it is noted that the short axes (Z) are sub-perpendicular related with a sub-parallel foliation. Furthermore, the nappe contact are designed during the intrusion of plutons associated with faults in the Zalm regions under brittle to semi-ductile deformation conditions.

Quartz CPO and kinematic analysis in deformed rocks devoid of visible stretching lineations: An integrated AMS and EBSD investigation

Kinematic analysis of deformed rocks requires study of structures in a section parallel to the stretching lineation and perpendicular to the foliation, i.e., XZ section of the strain ellipsoid. However, presence of stretching lineation is more of an exception rather than a norm in naturally deformed rocks. This raises challenges for kinematic studies. In this study the authors advocate use of Anisotropy of Magnetic Susceptibility (AMS) to identify the three principal axes of AMS ellipsoid (K1>K2>K3), which are equated with principal axes of the strain ellipsoid (X > Y > Z). This helps identify X direction of strain ellipsoid in deformed rocks that lack visible stretching lineations. It is proposed that a section prepared parallel to the K1K3 plane of a deformed rock can be treated as equivalent to XZ section of strain ellipsoid, thus making it possible to perform kinematic studies in a rock that did not have stretching lineation. Use of this method is demonstrated on massive metavolcanic rocks of Hutti region (Dharwar Craton, South India), which is replete with quartz veins that contain gold. Crystallographic Preferred Orientation (CPO) of quartz veins is measured using SEM-EBSD studies of thin sections prepared parallel to K1K3 plane of the host rock. Obtained data help recognize the presence of down-dip sense of movement as well as strain partitioning within veins, which are aspects that were not recognized in earlier studies. It is concluded that integration of AMS and SEM-EBSD studies will play an important role in kinematic studies in future.

Determining the Reference Frame for Kinematic Analysis in S-tectonites Using AMS

ABSTRACT In this paper a methodology based on anisotropy of magnetic susceptibility (AMS) measurements is presented to identify XZ section of the strain ellipsoid in order to perform kinematic analysis in S-tectonites, which are rocks that lack stretching lineation on the foliation plane. The similarity between orientations of three principal axes of the AMS ellipsoid (K1&amp;gt;K2&amp;gt;K3) and strain ellipsoid (X&amp;gt;Y&amp;gt;Z) is demonstrated by discussing the case of a mylonite (LS-tectonite) that contains both foliation and stretching lineation. Subsequently, the case of S-tectonite from the peninsular gneiss (south India) is discussed, where the K1K3 plane of AMS ellipsoid is equated with XZ section of strain ellipsoid. Quartz crystallo-graphic preferred orientations are investigated using SEM-EBSD studies in thin section prepared parallel to the K1K3 plane. Quartz c-axis patterns characteristic of rhomb &amp;lt;a&amp;gt; slip and indicating top-to-325° sense of shear are recorded. This supports the move-ment sense inferred by earlier researchers from northern parts of the sampled locality. Thus the usefulness of AMS in determining the reference frame for kinematic studies in S-tectonites is documented.

Relationship between finite strain and tectonic setting in the Ar-Ruwaydah area, eastern Arabian Shield, Saudi Arabia

Our work deals with structural characteristics of the Ar-Ruwaydah area, which lie between the Al Amar–Idsas fault and the Halaban belt. Our goals are accomplished through field reconnaissance and finite strain analysis, as well as microstructural investigation to estimate the tectonic evolution and structures in the Ar-Ruwaydah area. Our strain data show that Abt schist, metavolcano-sedimentary rocks, and granitic gneiss are characterized by weak to moderate deformation, and the axial ratios for the XZ section range from 1.55 to 2.22. The long axes for ellipsoids (X) have NW–SE and W–E trend directions in the Ar-Ruwaydah area while their short axes (Z) are subhorizontal to subvertical foliations. The strain magnitude does not display any increase towards the tectonic contacts for varying rocks units. Most of the obtained data indicate a dominant oblate with minor prolate strain symmetries in the Abt schist and metavolcano-sedimentary and metagranite rocks. The strain data also display flattening with some constriction. It is concluded that Abt schist, granitic gneiss, and metavolcano-sedimentary rocks have the same deformation behavior. Our finite strain accumulated during the metamorphism which was investigated by thrusting activity in the studied rocks. Furthermore, the nappe contact for different types of rock formed during thrusting activity and intrusion of granitic plutons under semi-brittle to ductile deformation conditions in the Ar-Ruwaydah area.

Integrated Remote Sensing and Structural Analysis Studies of Tayyib Al-Ism Area, Northwestern Arabian Shield, Saudi Arabia

Geological and structural mappings of Tayyib Al-Ism area were carried out using the rocks finite strain data, the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) data and the field based observations. To analyze the finite strain in the studied rocks, the Rf /ϕ and Fry methods are applied to feldspar porphyroclasts and mafic grains from nine metavolcano-sedimentary samples (Hegaf Formation), four diorite-gabbros suite samples (Sawawin Complex), two meta-granite samples (Ifal suite) and five Zuhd alkali granite samples. The obtained data indicate traces of high to moderate level of deformation in the meta-granite and metavolcano-sedimentary rocks. The axial ratios along the XZ section range from 1.70 to 4.80 for the Rf/ϕ method and from 1.50 to 4.50 for the Fry method. A sub-vertical trend of short axes in association with sub-horizontal foliation is also observed. These informations allow us to conclude that a finite strain in the deformed granitic rocks is of the same order of magnitude as in the metavolcano-sedimentary rocks. The contacts between the metavolcano-sedimentary and granitic rocks in Tayyib al Ism area were formed during the granitic intrusions along some of the faults under brittle to semi-ductile deformation conditions. These faults have significantly influenced the geometry and style of rifting in the Red Sea during the Neogene. The finite strain was accumulated in the area during the process of deformation, which superimpose the already existed nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain. In addition to finite strain analysis, band ratio images (3/1, 5/3, 7/5) and Principal Component Analysis (PCA) technique have been used, which proved effective in mapping geological and structural features of various rock bodies exposed in the study area.

Finite strain analysis of metavolcanics and metapyroclastics in gold-bearing shear zone of the Dungash area, Central Eastern Desert, Egypt

The Dungash gold mine area is situated in an EW-trending quartz vein along a shear zone in metavolcanic and metasedimentary host rocks in the Eastern Desert of Egypt. These rocks are associated with the major geologic structures, which are attributed to various deformational stages of the Neoproterozoic basement rocks. Field geology, finite strain and microstructural analyses were carried out and the relation-ships between the lithological contacts and major/minor structures have been studied. The Rf/ϕ and Fry methods were applied on the metavolcano-sedimentary and metapyroclastic samples from 5 quartz veins samples, 7 metavolcanics samples, 3 metasedimentary samples and 4 metapyroclastic samples in Dungash area. Finite-strain data show that a low to moderate range of deformation of the metavolcano-sedimentary samples and axial ratios in the XZ section range from 1.70 to 4.80 for the Rf/ϕ method and from 1.65 to 4.50 for the Fry method. We conclude that finite strain in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. Furthermore, the contact between principal rock units is sheared in the Dungash area under brittle to semi-ductile deformation conditions. In this case, the accumulated finite strain is associated with the deformation during thrusting to assemble nappe structure. It indicates that the sheared contacts have been formed during the accumulation of finite strain.

Structural and Mechanical Controls on Intrusion Related to Mahd Ad Dahab Area, Arabian Shield, Saudi Arabia

Mahd Ad Dahab area is located on the western side of the Arabian Precambrian Shield. In the study area, Mahd group rocks are deposited along margin of active extensional volcanotectonic basin. These rocks are associated with the major geologic structures which are attributed to various deformational stages of the Precambrian basement. Field geology, finite strain and microstructural studies were carried out and the relationships between the lithological contacts and major/minor structures have been studied. The Rf/φ and Fry methods on the metavolcano-sedimentary samples from 3 andesite samples, 2 lower agglomerate samples, 7 lower rhyolite samples, 3 upper agglomerate, 1 upper tuff sample and 2 rhyolite porphyry samples were used in Mahd Ad Dahab area. Finite-strain data shows that a low to moderate range of deformation of the metavolcanosedimentary samples and axial ratios in the XZ section range from 1.10 to 2.50 for the Rf/φ method and from 1.15 to 2.35 for the Fry method. Furthermore, the short axes are subvertical associated with a subhorizontal foliation. We conclude that finite strain in the deformed rocks is of the same order of magnitude for all units of metavolcano-sedimentary rocks. Furthermore, contacts formed during intrusion of plutons with some faults in the Mahd Ad Dahab area under brittle to semi-ductile deformation conditions. In this case, finite strain accumulated during superimposed deformation on the already assembled nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain.

Strain analysis and microstructural evolution characteristic of neoproterozoic rocks associations of Wadi El Falek, centre Eastern Desert, Egypt

The estimation of finite strain in rocks is fundamental to a meaningful understanding of deformational processes and products on all scales from microscopic fabric development to regional structural analyses. The Rf/φ and Fry methods on feldspar porphyroclasts and mafic grains from 5 granite, 1 metavolcanic, 3 metasedimentary and 1 granodiorite samples were used in Wadi El Falek region. Finite-strain data shows that a high to moderate range of deformation of the granitic to metavolcano-sedimentary samples and axial ratios in the XZ section range from 1.60 to 4.10 for the Rf/φ method and from 2.80 to 4.90 for the Fry method. Furthermore, the short axes are subvertical associated with a subhorizontal foliation. We conclude that finite strain in the deformed granite rocks is of the same order of magnitude as that from metavolcano-sedimentary rocks. Furthermore, contacts formed during intrusion of plutons with some faults in the Wadi El Falek area under brittle to semi-ductile deformation conditions. In this case, finite strain accumulated during superimposed deformation on the already assembled nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain.

Determining heterogeneous deformation for granitic rocks in the northern thrust in Wadi Mubarak belt, Eastern Desert, Egypt

Finite-strain was studied in the mylonitic granitic and metasedimentary rocks in the northern thrust in Wadi Mubarak belt to show a relationship to nappe contacts between the old granitic and metavolcano-sedimentary rocks and to shed light on the heterogeneous deformation for the northern thrust in Wadi Mubarak belt. We used the Rf/ϕ and Fry methods on feldspar porphyroclasts, quartz and mafic grains from 7 old granitic and 7 metasedimentary samples in the northern thrust in Wadi Mubarak belt. The finite-strain data shows that old granitic rocks were moderate to highly deformed and axial ratios in the XZ section range from 3.05 to 7.10 for granitic and metasedimentary rocks. The long axes (X) of the finite-strain ellipsoids trend W/WNW and E/ENE in the northern thrust in Wadi Mubarak belt. Furthermore, the short axes (Z) are subvertical associated with a subhorizontal foliation. The value of strain magnitudes mainly constants towards the tectonic contacts between the mylonitic granite and metavolcano-sedimentary rocks. The data indicate oblate strain symmetry (flattening strain) in the mylonitic granite rocks. It is suggested that the accumulation of finite strain was formed before or/and during nappe contacts. The penetrative subhorizontal foliation is subparallel to the tectonic contacts with the overlying nappes and foliation was formed during nappe thrusting.

Finite-strain analysis of Metavolcano-sedimentary rocks at Gabel El Mayet area, Central Eastern Desert, Egypt

Finite strain was estimated in the metavolcano-sedimentary rocks, which surround by serpentinites of Gabel El Mayet area. Finite strain shows a relationship to nappe contacts between the metavolcano-sedimentary rocks and serpentinite and sheds light on the nature of the subhorizontal foliation typical for the Gable Mayet shear zone. We used the R f/ ϕ and Fry methods on feldspar porphyroclasts and mafic grains from 10 metasedimentary and six metavolcanic samples in Gabel El Mayet region. Our finite-strain data show that the metavolcano-sedimentary rocks were moderately deformed and axial ratios in the XZ section range from 1.9 to 3.9. The long axes of the finite-strain ellipsoids trend W/WNW in the north and W/WSW in the south of the Gabel El Mayet shear zone. Furthermore, the short axes are subvertical to a subhorizontal foliation. The strain magnitudes increase towards the tectonic contacts between the metavolcano-sedimentary rocks and serpentinite. The data indicate oblate strain symmetry in the metavolcano-sedimentary rocks. Hence, our strain data also indicate flattening strain. We assume that the metasedimentary and metavolcanics rocks have similar deformation behaviour. The fact that finite strain accumulated during the metamorphism indicates that the nappe contacts formed during the accumulation of finite strain and thus during thrusting. We conclude that the nappe contacts formed during progressive thrusting under brittle to semi-brittle deformation conditions by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gabel El Mayet shear zone.