This study aims to evaluate the activity concentrations of
238
U,
226
Ra,
232
Th,
228
Th and
40
K along the beaches of Sithonia Peninsula which are adjacent to the rock-types of the Sithonia Plutonic ...Complex. These range from 6–673, 5–767, 5–1750, 6–1760 and 185–875 Bq/kg respectively. The (% wt.) heavy magnetic (HM) fraction (epidote, allanite, hornblende, biotite and garnet), the heavy non-magnetic (HNM) fraction (monazite, zircon, titanite and apatite) and the total heavy (TH) fraction, were correlated with the concentrations of the measured radionuclides in the bulk samples. The HNM fraction seems to control the activity concentrations of
238
U in all samples, while the HM fraction, at least for the heavy mineral rich samples bearing high amounts of epidote crystals with allanite cores, controls their
232
Th content. The measured radionuclides in beach sands were normalized to the respective values measured in the granitic rocks, which are their most probable parent rocks, in order to provide data on their enrichment or depletion. The annual effective dose varies from 0.013 to 0.688 mSv y
−1
for local people working on the beach, while for tourists the annual external effective dose ranges between 0.003 and 0.165 mSv y
−1
.
Beach sands from Aggelochori coast line are investigated for their geochemistry and REE content, mineralogy and their provenance. These fluvial sands bear heavy minerals enriched horizons (containing ...minerals such as magnetite, zircon, ilmenite, hematite, rutile and titanite) that can be distinguished due to their black color and are formed usually due to the action of sea waves that deposit the heavy minerals and remove the lighter ones. After a suitable processing (washing, sieving, drying and magnetic separation) of the samples, the mineral constituents and their presence (wt.%) were estimated by XRD. Among the samples, the one being simultaneously the more fine grained and the more zircon-enriched (as suggested by XRPD data and optical microscopy analysis) has been selected for further geochemical analyses. The major and trace elements contents were compared to previously studied REE enriched beach sands from Kavala and Sithonia. Beach sands from Aggelochori area appear to have relatively low REE contents. Considering the provenance of these sediments, we suggest that these sands, are a product of the erosion of multi-sources, including the near-by Monopigado granite, as well as metamorphic rocks, as indicated by the presence of rutile and both ilmenite and magnetite in some samples. Therefore, there are indications of a complex flow pattern that existed at the paleo-catchment area of the deposition.
This study aims to evaluate the activity concentrationsof
U,
Ra,
Th,
Th and
K along thebeaches of Kavala being adjacent to the rock-types of theKavala pluton. These ranged from 14–940, 16–1710, ...26–4547, 27–4488 and 194–1307 Bq/kg respectively, representingthe highest values of natural radioactivity measuredin sediments of Greece. The (%wt.) heavy magnetic (HM)(allanite, amphibole, mica, clinopyroxene, magnetite andhematite) fraction, the heavy non-magnetic (HNM) (monazite,zircon, titanite and apatite) fraction and the totalheavy fraction (TH), were correlated with the concentrationsof the measured radionuclides in the bulk samples.The heavy fractions seem to control the activity concentrationsof
U and 232Th of all the samples, showingsome local differences in the main
U and
Th mineralcarrier. The measured radionuclides in the beach sandswere normalized to the respective values measured in thegranitic rocks, which are their most probable parentalrocks, so as to provide data upon their enrichment or depletion.The annual equivalent dose varies between 0.01and 0.35 mSv y
for tourists and from 0.03 to 1.48 mSv y
for local people working on the beach.
The present contribution reports new whole-rock major and trace element data, REE, and Sr–Nd isotopic ratios for the early Miocene Pohorje igneous complex (PIC) in Slovenia (Eastern Alps), which, ...along with published data, are used to investigate its genesis and evolution. The complex comprises three main rock-groups. The largest one is made of granodiorite and minor tonalite (GTD) enclosing mafic microgranular enclaves (MME), and a small Q-dioritic body. The second group prevailingly consists of dacite stocks and dykes, and porphyritic microgranodiorite (DAMG). Andesitic dykes (AD), intruding metamorphic rocks and less often the GDT, constitute the third group. Aplites and pegmatites intrude both the Pohorje igneous complex and the country rocks.
Evidence of interaction between magmas has been observed only in the GDT rocks. In the southeastern part of the complex the GDT rocks are less evolved and emplaced at greater depth (ca. 16.5–17.6 km) than the rocks cropping out in the northwestern part (ca. 12.4–13.8 km). DAMG rocks can be divided geochemically into two groups, high-Ga DAMG and low-Ga DAMG, having similar chemical composition with the most evolved GDT, and the most evolved andesitic dykes, respectively. The andesitic dykes can be divided into three groups that differ in LILE contents from each other up to three orders of magnitude.
A Mixing plus Fractional Crystallization (MFC) process between the least evolved MME and the most evolved DAMG rocks is considered responsible for the formation of the two diversely evolved GDT. Two of the three AD groups (AD1, AD3) originated in the mantle, whereas the third one (AD2) is considered as the result of an AFC process between the less enriched andesite (AD1) and continental crust (gneiss). The same process is considered responsible for the low-Ga DAMG genesis.
The most mafic magma is presumably the result of melting of mantle wedge differently metasomatized and enriched in LILE due to fluids, sediment melts, and bulk sediments. The felsic end-member magma of the MFC process originated from partial melting of intermediate-lower crust having intermediate to basaltic composition. Geodynamic sequence for the formation of the PIC comprehend mantle metasomatism during Alpine subduction, thickening of crust during the collision that followed subduction, and production of mantle melts in response to delamination caused by opening of the Pannonian basin and asthenospheric upwelling. Crustal derived melts resulted by underplating of mantle-derived magmas.
•Miocene Pohorje igneous complex comprises plutonic, volcanic and sub volcanic rocks.•Melting of mantle metasomatized by fluids, sediments, and sediment melts.•Delamination caused by opening of the Pannonian basin and asthenosphere upwelling.•Crust-derived melts generated through underplating of mantle-derived magmas.•Complex evolutionary process like fractionation, magma mixing and crustal assimilation.
Modern sand samples were collected from the Vertiskos Unit of the Serbomacedonian Massif, northern Greece, and were examined for their texture and mineralogical composition. They were collected from ...active channels and torrents. The textural study demonstrated that these modern sands are moderately to very-poorly sorted, often polymodal in grain size distribution, texturally and mineralogically immature to submature, and consist of coarse-grained gravelly sands to slightly-gravelly muddy sands. The dominant composition is quartzofeldspathic. All samples contain detrital minerals of metamorphic origin, mainly amphibole and garnet, in addition to minor amounts of pyroxene and detrital calcite. These sediments were deposited rapidly and close to their source, the metamorphic basement of the Vertiskos Unit. The mineral constituents of the samples indicate that the Vertiskos Unit is undergoing rapid physical weathering due to the temperate and seasonal climate. The results of this study suggest that these modern sands constitute one sedimentary petrologic province comprised of primarily of amphibole-garnet.
The Fanos granite occurs in the Peonias subzone of the eastern Axios-Vardar zone in northern Greece. The Fanos granite is Late Jurassic (158 ± 1 Ma) and trends N–S, intruding the Mesozoic back-arc ...Guevgueli ophiolitic complex. The intrusive character of the eastern contact of the Fanos granite with the host ophiolitic complex is well preserved. In turn the western contact is overprinted by a few meters thick, west- to southwest-directed semi-ductile thrust zone, of Late Jurassic-Early Cretaceous age. The Fanos granite is dominated by the typical, isotropic granitoid fabric, although in some places the initial magmatic flow fabric is preserved. The main deformation recognized in the Fanos granite occurred in brittle regime and expressed by Tertiary thrust faults and Neogene-Quaternary normal to oblique normal faults. The origin as well as the possible tectonic setting of the Fanos granite is the main topics that we address in our study. Rock samples of the Fanos granite along with the adjusted Kotza Dere quartz diorite were analyzed for major and trace elements and for Sr and Nd isotopes (only the quartz diorite). The geochemical data show that the granite has peraluminous characteristics, high-K calc-alkaline affinities, and I-type features. The Sr initial isotopic values of the Fanos granite are rather low (0.7053–0.7056) while for the quartz diorite range from 0.7066 to 0.7068. The Nd initial isotopic values range from 0.51235 to 0.51240 for the granite and from 0.51222 to 0.51233 for the quartz diorite. The source of the granitic melt is interpreted to be meta-basaltic amphibolites. These amphibolites are the metamorphic products of enriched mantle melts that underplated the oceanic lithosphere. Taking into account our and published structural and geochemical data for the Fanos granite along with the tectonic data of the broader Axios-Vardar zone, we suggest that the studied granitic rocks were formed during an intra-oceanic subduction within the Neotethyan Axios-Vardar ocean. The granite was obducted during the Late Jurassic, together with the Neotethyan ophiolites westwards, on the Paikon Massif, in the eastern margin of the Pelagonian continent.
The Fanos granite occurs in the Peonias subzone of the eastern Axios-Vardar zone in northern Greece. The Fanos granite is Late Jurassic (158 ± 1 Ma) and trends N-S, intruding the Mesozoic back-arc ...Guevgueli ophiolitic complex. The intrusive character of the eastern contact of the Fanos granite with the host ophiolitic complex is well preserved. In turn the western contact is overprinted by a few meters thick, west- to southwest-directed semi-ductile thrust zone, of Late Jurassic-Early Cretaceous age. The Fanos granite is dominated by the typical, isotropic granitoid fabric, although in some places the initial magmatic flow fabric is preserved. The main deformation recognized in the Fanos granite occurred in brittle regime and expressed by Tertiary thrust faults and Neogene-Quaternary normal to oblique normal faults. The origin as well as the possible tectonic setting of the Fanos granite is the main topics that we address in our study. Rock samples of the Fanos granite along with the adjusted Kotza Dere quartz diorite were analyzed for major and trace elements and for Sr and Nd isotopes (only the quartz diorite). The geochemical data show that the granite has peraluminous characteristics, high-K calc-alkaline affinities, and I-type features. The Sr initial isotopic values of the Fanos granite are rather low (0.7053-0.7056) while for the quartz diorite range from 0.7066 to 0.7068. The Nd initial isotopic values range from 0.51235 to 0.51240 for the granite and from 0.51222 to 0.51233 for the quartz diorite. The source of the granitic melt is interpreted to be meta-basaltic amphibolites. These amphibolites are the metamorphic products of enriched mantle melts that underplated the oceanic lithosphere. Taking into account our and published structural and geochemical data for the Fanos granite along with the tectonic data of the broader Axios-Vardar zone, we suggest that the studied granitic rocks were formed during an intra-oceanic subduction within the Neotethyan Axios-Vardar ocean. The granite was obducted during the Late Jurassic, together with the Neotethyan ophiolites westwards, on the Paikon Massif, in the eastern margin of the Pelagonian continent.
Torud-Ahmad Abad magmatic belt is located 175km east and southeast of Shahrood in the northern part of the Central Iran Structural Zone and includes a thick sequence of Paleocene to middle Eocene ...volcanic and volcanosedimentary rocks. This magmatic belt was formed by numerous hypabyssal igneous adakitic domes constituting basaltic andesite, andesite, trachyandesite, dacite, trachydacite, and dacite. The investigated rocks are mainly composed of pyroxene, amphibole, and plagioclase, with minor biotite and opaque minerals. Mineral chemical analysis reveals that plagioclase composition varies from albite to labradorite, clinopyroxene varies from diopside to augite, and amphibole varies from Mg-hastingsite to Mg-hornblende.
Amphibole geothermobarometry suggests crystallization temperatures of 850–1050°C, at 2–6kbar and the temperature of 920–970°C, at a pressure of 3–4.5kbar, which are conditions in agreement with andesite and dacite formation. Clinopyroxene crystallized at temperatures of 1020–1170°C, at 2–10kbar, indicating crystallization at crustal depths of maximum 30km for the studied intrusive rocks in the Torud-Ahmad Abad magmatic belt.
•Mineral chemistry•P-T conditions of the mineral crystallization in hypabyssal igneous rocks of Torud-Ahmad Abad magmatic belt•Determine the depth of emplacement of rock.•Relation of the studied magmatic rocks to subduction of the Sabzevar–Darouneh Neotethyis oceanic slab
Seventy samples from major plutons (mainly granitic) of Western Anatolia (Turkey) have been analyzed by γ-ray spectrometry to determine the specific activities of
238
U,
226
Ra,
232
Th and
40
K ...(Bq/kg). Τhe natural radioactivity ranged up to 264 Bq/kg for
238
U, 229.62 Bq/kg for
226
Ra, up to 207.32 Bq/kg for
232
Th and up to 2541.95 Bq/kg for
40
K. Any possible relationship between the specific activities of
226
Ra,
238
U,
232
Th and
40
K and some characteristics of the studied samples (age, rock-type, colour, grain size, occurrence, chemical and mineralogical composition) was investigated. Age, major and trace element geochemistry, color, pluton location and mineralogical composition are likely to affect the concentrations of the measured radionuclides. The range of the Th/U ratio was large (0.003–11.374). The latter, along with
226
Ra/
238
U radioactive secular disequilibrium, is also discussed and explained by magmatic processes during differentiation.
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