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.

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]

scholarly journals Geology and deformation of the Serbo-Macedonian massif in the northern part of the Athos Peninsula, Northern Greece: Insights from two detailed cross-sections

2020 ◽  
Vol 56 (1) ◽  
pp. 167
Author(s):  
Petros Georgios Neofotistos ◽  
Markos Damianos Tranos ◽  
Renée Heilbronner
Keyword(s):  
Structural Analysis ◽  
Shear Zone ◽  
Cross Sections ◽  
Crystalline Rocks ◽  
Ultramafic Rocks ◽  
Northern Greece ◽  
Tectonic Event ◽  
Normal Contact ◽  
Facies Metamorphism ◽  
Geological Map

The Athos peninsula occupies the south-eastern part of the wider Chalkidiki peninsula in Central Macedonia, Greece. It is mainly built up by crystalline rocks belonging to the Serbo-Macedonian massif, traditionally constituting, along with the Rhodope massif, the Hellenic hinterland. According to the basic geological map of the peninsula, its northern part is mainly composed of marbles grouped into the Kerdyllion Unit, and biotite gneisses and two-mica gneisses grouped into the Vertiskos Unit of the Serbo-Macedonian massif, whereas the contact between the units is considered as a normal contact, although it has been re-evaluated as tectonic later on. Moreover, amphibolites and ultramafic rocks exist along with the previously mentioned rocks, making the geology and relationship between the two units much more complicated. Two detailed cross-sections and structural analysis permit us to revise the geology of the region concluding that the marbles, the amphibolite gneisses, formerly independent amphibolites, and the biotite gneisses belong to the Kerdyllion Unit that is strongly characterized by migmatization and anatexis, whereas the Vertiskos Unit is represented predominantly by two-mica gneisses that were not extensively, if at all, affected by these phenomena. Isoclinal folding and intense shearing with an overall top-to-the-S sense of shear resulted in the main fabric of the rocks and the mylonitic shear zone between the units. More importantly, the two-mica gneiss of the Vertiskos Unit is sandwiched between the rocks of the Kerdyllion Unit. We attribute both isoclinal folding and shearing to a Mesozoic tectonic event associated with an amphibolite facies metamorphism, leading to an Alpine reworking of the Serbo-Macedonian massif. This Alpine reworking continues during Eocene times with an ENE-WSW compression, giving rise to asymmetric to inverted folds, co-axially refolding pre-existing fabrics and structures. Our work strongly suggests that the overall structure and tectono-stratigraphy concerning the Vertiskos and Kerdyllion Units as well as the contact between them should not be based on the existence of the marbles, as traditionally followed up till now, but on the migmatization and anatexis processes that are almost absent from the rocks of the Vertiskos Unit.

scholarly journals Rheological Contrast between Quartz and Coesite Generates Strain Localization in Deeply Subducted Continental Crust

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 842
Author(s):  
Kouhei Asano ◽  
Katsuyoshi Michibayashi ◽  
Tomohiro Takebayashi
Keyword(s):  
Rheological Behavior ◽  
Strain Localization ◽  
Shear Zones ◽  
Ultrahigh Pressure ◽  
Ultramafic Rocks ◽  
Crustal Material ◽  
Orientation Data ◽  
Crystallographic Preferred Orientation ◽  
Dabie Shan ◽  
Felsic Rocks

Deformation microstructures of peak metamorphic conditions in ultrahigh-pressure (UHP) metamorphic rocks constrain the rheological behavior of deeply subducted crustal material within a subduction channel. However, studies of such rocks are limited by the overprinting effects of retrograde metamorphism during exhumation. Here, we present the deformation microstructures and crystallographic-preferred orientation data of minerals in UHP rocks from the Dabie–Shan to study the rheological behavior of deeply subducted continental material under UHP conditions. The studied samples preserve deformation microstructures that formed under UHP conditions and can be distinguished into two types: high-strain mafic–ultramafic samples (eclogite and garnet-clinopyroxenite) and low-strain felsic samples (jadeite quartzite). This distinction suggests that felsic rocks are less strained than mafic–ultramafic rocks under UHP conditions. We argue that the phase transition from quartz to coesite in the felsic rocks may explain the microstructural differences between the studied mafic–ultramafic and felsic rock samples. The presence of coesite, which has a higher strength than quartz, may result in an increase in the bulk strength of felsic rocks, leading to strain localization in nearby mafic–ultramafic rocks. The formation of shear zones associated with strain localization under HP/UHP conditions can induce the detachment of subducted crustal material from subducting lithosphere, which is a prerequisite for the exhumation of UHP rocks. These findings suggest that coesite has an important influence on the rheological behavior of crustal material that is subducted to coesite-stable depths.

scholarly journals Mineralogy and Geochemistry of Ultramafic Rocks from Rachoni Magnesite Mine, Gerakini (Chalkidiki, Northern Greece)

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 934
Author(s):  
Evangelos Tzamos ◽  
Micol Bussolesi ◽  
Giovanni Grieco ◽  
Pietro Marescotti ◽  
Laura Crispini ◽  
...  
Keyword(s):  
Raw Materials ◽  
Mining Area ◽  
Ultramafic Rocks ◽  
Northern Greece ◽  
Icp Ms ◽  
Time In Literature ◽  
History Of ◽  
First Time ◽  
The Eu

The importance of magnesite for the EU economy and industry is very high, making the understanding of their genesis for the exploration for new deposits a priority for the raw materials scientific community. In this direction, the study of the magnesite-hosting ultramafic rocks can be proved very useful. For the present study, ultramafic rock samples were collected from the magnesite ore-hosting ophiolite of the Gerakini mining area (Chalkidiki, Greece) to investigate the consecutive alteration events of the rocks which led to the metallogenesis of the significant magnesite ores of the area. All samples were subjected to a series of analytical methods for the determination of their mineralogical and geochemical characteristics: optical microscopy, XRD, SEM, EMPA, ICP–MS/OES and CIPW normalization. The results of these analyses revealed that the ultramafic rocks of the area have not only all been subjected to serpentinization, but these rocks have also undergone carbonation, silification and clay alteration. The latter events are attributed to the circulation of CO2-rich fluids responsible for the formation of the magnesite ores and locally, the further alteration of the serpentinites into listvenites. The current mineralogy of these rocks was found to be linked to one or more alteration event that took place, thus a significant contribution to the metallo- and petrogenetic history of the Gerakini ophiolite has been made. Furthermore, for the first time in literature, Fe inclusions in olivines from Greece were reported.

A comparison of theory and experiment for photo-ionization cross-sections I. Neon and the elements from boron to neon

1951 ◽  
Vol 208 (1094) ◽  
pp. 408-418 ◽  
Keyword(s):  
Cross Sections ◽  
General Trend ◽  
Wave Functions ◽  
Ionization Cross ◽  
Hartree Fock ◽  
Quantal Theory ◽  
Ionization Cross Sections ◽  
Photo Ionization ◽  
Near Future ◽  
Dipole Length

The quantal theory of the continuous photo-electric absorption of radiation is briefly summarized, pàrticular attention being given to the alternative formulae available and to the accuracy to be expected in practical calculations. Detailed calculations are described for the photo-ionization cross-section of neon, a system for which it is understood that experimental data should be available in the near future. The calculation is made using Hartree-Fock wave functions and the two formulae of the dipole length and the dipole velocity. The corresponding cross-sections are found to be 5.8 and 4.4 x 10- 18 cm 2 . at the spectral head and to rise slowly with increasing frequency until a broad maximum is reached for an energy of the ejected electron of about 11 eV. A comparison is made with previous calculations on the elements from boron to neon ; the general trend of the results is discussed and improved estimates for boron and fluorine are given (10 x 10 -18 cm 2 . for boron and 4.3 x 10- 18 cm 2 . for fluorine at the spectral head).

scholarly journals Supplemental Material: Quantifying shortening across the central Appalachian fold-thrust belt, Virginia and West Virginia, USA: Reconciling grain-, outcrop-, and map-scale shortening

2020 ◽  
Author(s):  
D. Lammie ◽  
et al.
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Thickness Variation ◽  
Sample Mean ◽  
Appalachian Plateau ◽  
Scale Layer ◽  
Vertical Bars ◽  
Map Scale ◽  
Great Valley ◽  
Western Limb

Plate 1. (A and B) Balanced (A) and restored (B) cross section A-A' extending from the eastern Great Valley westward to the Burning Spring anticline (Fig. 1). Total deformed length (274 km) and undeformed restored length (346 km) are measured from a pin line east of the extent of documented map-scale shortening on the Appalachian Plateau, resulting in 78 km (23%) total shortening. (C) As shown, shortening in Upper Devonian through Permian rocks assumes 10% layer-parallel shortening (LPS) in the Appalachian Plateau and across the Appalachian front (to thick vertical bar) and 25% LPS in the Valley and Ridge (region between thick vertical bars). Shortening in the Great Valley requires 35% LPS, compared to the >50% LPS measured in that region (Wright and Platt, 1982). Cross sections drawn with no vertical exaggeration; Circled numbers—duplex numbers; Fm–Formation; Gp—Group. Plate 2. Geologic cross section divided into 16 sequentially numbered intervals (circled numbers above the cross section) spanning from the western limb of the Burning Springs anticline eastward to the Great Valley. Locations of each of the 40 samples used to constrain grain-scale layer-parallel shortening (LPS) are shown as small white dots projected into the line of section; calculated LPS (as a percentage) are shown above each sample. Mean LPS values for each interval are summarized in Table 2. (A) Cross section constructed to minimize the amount of unit thickness variation in the Reedsville-Martinsburg Formations. Balancing this section requires 10% outcrop-scale shortening between the Elkins Valley anticline and the boundary between the Valley and Ridge and Great Valley. (B) Cross section constructed to minimize contributions from outcrop-scale shortening. Balancing this section requires 5% outcrop-scale shortening between the Elkins Valley anticline and the boundary between the Valley and Ridge and Great Valley. Cross sections drawn with no vertical exaggeration; circled numbers—duplex numbers; Fm—Formation; Gp—Group.

scholarly journals Determination of Scandium in mafic and ultramafic rocks of ophiolites from Luk Ulo Complex, Karangsambung, Central Java, Indonesia

2020 ◽  
Vol 200 ◽  
pp. 06003
Author(s):  
Nugroho Imam Setiawan ◽  
Kardo Polarman Rajoki Silitonga ◽  
Fahmi Adiyatma Makkaratte ◽  
Chusni Ansori
Keyword(s):  
Mineral Composition ◽  
General Trend ◽  
Elemental Abundance ◽  
Ultramafic Rocks ◽  
Mining Activities ◽  
Central Java ◽  
Parent Rocks ◽  
Modern Industry

Scandium (Sc) is important element for its utilization in modern industry. Initial Sc content in the parent rocks primary importance controlling the Sc concentrations in its weathered derivatives. This contribution examines the Sc concentrations in parent rocks of mafic and ultramafic rocks related to the ophiolite series in Luk Ulo Complex, Karangsambung, Central Java, Indonesia. The ophiolite series in this area are basalt, microgabbronorite, gabbronorite, websterite, and serpentinite from 5 locations of Medana, Lokidang, Parakansubah, Selogiri, and Pucangan areas. The general trend from the distribution of Sc in the ophiolite sequence of Medana and Parakansubah-Lokidang Rivers suggests the Sc contents increase from shallow to deeper levels of the sequence. The lowest concentrations of Sc in the ophiolite sequence of Medana and Parakansubah-Lokidang Rivers are in basalt, which are 24–29 ppm. In the middle sequence, the Sc concentrations are 27–34 ppm and 24–43 ppm, respectively in microgabbronorite and gabbronorite. The highest Sc concentrations are in websterite, which are 51–54 ppm, as the deepest sequence of the ophiolite in this area. Meanwhile, Sc contents in serpentinite from Selogiri and Pucangan areas are 5–11 ppm, which are considered the lowest Sc contents. It suggests that the pre-serpentinization mineral composition rather than the process of serpentinization determine the elemental abundance of Sc in serpentinite. The results are used to be an analog for Sc identification in the ophiolite belts in central Indonesia. This also considering that Luk Ulo Complex been established as National Geopark of Karangsambung-Karangbolong, so that mining activities are prohibited in this area.

scholarly journals Geochemistry of the Madawara Igneous Complex, Bundelkhand Craton, Central India: Implications for PGE Metallogeny

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Satyanarayanan Manavalan ◽  
Surya Prakash Singh ◽  
Vysetti Balaram ◽  
Mohanty Niranjan
Keyword(s):  
Central India ◽  
Shear Zones ◽  
Ultramafic Rocks ◽  
Spinel Peridotite ◽  
Igneous Complex ◽  
Total Platinum ◽  
Group I ◽  
Ultramafic Complex ◽  
Group Ii ◽  
High Degree

Abstract The southern part of the Bundelkhand craton contains a series of a E-W trending mafic and ultramafic rocks, about 40 km in length and 2–4 km wide, that occur as intrusions within the Bundelkhand Gneissic Complex (BnGC). They are confined between the Madawara- Karitoran and Sonrai-Girar shear zones. Dunite, harzburgite, lherzolite and websterite are the commonly occurring ultramafic rocks that have high MgO, Ni, Cr, PGE and low Al2O3, CaO, K2O, TiO2 and V contents, and shows peridotitic affinity. A distinct trend of crystallization from peridotite to komatiitic basalt has been inferred from geochemical plots, which also indicates the occurrence of at least two varieties among the ultramafic suite of the Madawara ultramafic complex, namely, Group I comprising dunite, spinel peridotite, harzburgite and lherzolite, and Group II consisting of pyroxenite, websterite and olivine websterite. In several places, the rocks of Group II have an intrusive relationship with Group I, and are relatively enriched in total platinum group elements (PGE ~ 300 ppb). The discrimination diagrams suggest that the PGE are enriched in low sulphur-fugacity source magma at moderate to deeper depths by high degree of partial melting of the mantle.

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.

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