Geochronology of granites of the western Korosten AMCG complex (Ukrainian Shield): implications for the emplacement history and origin of miarolitic pegmatites

The origin of large miarolitic (also known as “chamber”) pegmatites is not fully understood although they may have great economic value. The formation of cavities in magmatic bodies is related to melt degassing and gas or fluid flow through partially solidified magma. In this paper, the origin of the Volyn pegmatite field, located in the Palaeoproterozoic Korosten anorthosite–mangerite–charnockite–granite (AMCG) complex, North-Western region of the Ukrainian Shield, is discussed. Pegmatites of the field host deposits of piezoelectric quartz that is accompanied by gem-quality beryl and topaz. The Volyn pegmatite field is confined to granites located in the south-western part of the Korosten complex and extends for 22 km along the contact with the anorthosite massif within the Korosten plutonic complex. Geological data indicate hybridization of basic melts and partly crystallized granites, as well as direct impact of fluids derived from basic melts on the chamber pegmatites. The new U–Pb zircon ages obtained for granites and pegmatites of the Korosten complex confirm that the rock assemblage in the northern part of the complex crystallized between 1800 and 1780 Ma, whereas rocks in the southern part intruded mainly between 1768 and 1755 Ma. U–Pb zircon ages for granites from the south-western part of the Korosten complex indicate that granites were emplaced at 1770–1765 Ma, a few million years prior to the intrusion of the gabbro–anorthosite massif (1762–1758 Ma), while chamber pegmatites in these granites crystallized at 1760 ± 3 Ma, coevally with the basic rocks. Ultimately, the formation of the chamber pegmatites was related to the reheating of the semi-crystallized granitic intrusion and to fluids migrating from the underlying gabbro–anorthosite massif.

Tarawera Volcanic Complex

<p>The Tarawera Volcanic Complex is situated on the south eastern side of the Okataina Volcanic Centre, and is an association of rhyolite domes, flows and tephra, and basalt scoria. Twelve rhyolite domes are described, and using evidence obtained from the good internal sections available, the general structure of volcanic domes is discussed. Tephra stratigraphy of the Tarawera-Rerewhakaaitu region is described and by relating stratigraphy on the mountain to this tephra, four major eruptions can be recognized. A sequence of events for the Kaharoa eruption about 1020 A.D. can be postulated. The Tarawera eruption in 1886, however, was observed, and from the eye witness accounts, together with present day field evidence, a detailed account can be written. All the rocks of the Complex are described petrographically, mineralogically, and in some cases petrochemically. Twelve new full analyses; nine partial analyses of plagioclase, and eight partial analyses of residual glass are given, and the relationship of these is illustrated by variation diagrams. Finally, the origins of the acid and basic rocks of the Complex are discussed, and a hypothesis for the occurrence of the two lava types is given.</p>

Tarawera Volcanic Complex

<p>The Tarawera Volcanic Complex is situated on the south eastern side of the Okataina Volcanic Centre, and is an association of rhyolite domes, flows and tephra, and basalt scoria. Twelve rhyolite domes are described, and using evidence obtained from the good internal sections available, the general structure of volcanic domes is discussed. Tephra stratigraphy of the Tarawera-Rerewhakaaitu region is described and by relating stratigraphy on the mountain to this tephra, four major eruptions can be recognized. A sequence of events for the Kaharoa eruption about 1020 A.D. can be postulated. The Tarawera eruption in 1886, however, was observed, and from the eye witness accounts, together with present day field evidence, a detailed account can be written. All the rocks of the Complex are described petrographically, mineralogically, and in some cases petrochemically. Twelve new full analyses; nine partial analyses of plagioclase, and eight partial analyses of residual glass are given, and the relationship of these is illustrated by variation diagrams. Finally, the origins of the acid and basic rocks of the Complex are discussed, and a hypothesis for the occurrence of the two lava types is given.</p>

Polyformational Agdai Massif (Verkhoyansk-Kolyma Orogenic Region)

The earliest Mesozoic granitoid formations of the Verkhoyansk-Kolyma orogenic region are derivatives of the Late Jurassic-Early Cretaceous gabbro-diorite-granodiorite formation, involvinggold and polymetallic mineralization. Late Cretaceous alkaline-feldspar or alkaline granites with associated rare-earth mineralization complete the granitoid magmatism of the region. The Agdai massif, which combines both of the mentioned groups of rocks, was the object of our research. Therefore, understanding their petrological and genetic features is of great interest. It is determined that the eastern part of the massif is composed of diorites and granodiorites and includes autoliths and xenoliths of gabbro-diorite composition. The isotopic K-Ar age of gabbro-diorites is 154Ma, diorites –148 Ma, granodiorites –117–124 Ma, and dike granites – 114 Ma. The rocks are characterized bydisequilibrium mineral assemblages: early magmatic pyroxene-Labrador, typical for the basic rocks, and late - micropegmatite granitoid. The origin of the parent melts occurred within the lower crust in amphibolite substrates at temperatures of 1000–1150°C and a pressure of 1.4-1.6 GPa under the influence of the mantle main melt and the partial mixing of the latter with the resulting crustal melt. The western part of the outcrop was formed at the beginning of the Late Cretaceous (the isotopic K-Ar age of the granites is 92+/-3 Ma) and is composed of alkaline feldspar leucogranites. According to all petro - and geochemical parameters, the rocks are defined as post-orogenic or rift-related granites of the A-type. The presence of inclusions of pyroxene-labrador composition, titanomagnetite, zircon of morphotype D and the ratio of the basic petrochemical parameters allow us to refer them to A-type granites related to continental rifting. High melt temperatures (990-1030°C) at relatively low pressures during magma generation (0.7–0.8 GPa) could be achieved only when additional heat was supplied from an external (deep) source. The presence of nonequilibrium mineral associations indicates a possible syntax of the granite and the main melt. In general, the Agdai massif is a polyformational, polygenic structure formed by the intrusion of melts through common or closely located magma conduits.

Diabase from Drača open pit mine in central Serbia - quality assessment for building stone purposes

Vast masses of basic rocks are present as tectonic blocks and slices along the Eastern deep fault of the Vardar zone of Serbia. They are predominantly comprised of gabbro, with smaller part made up of diabase, and occurrences of granite, aplite and pegmatite dykes. Basic rock masses are trending along the line Kragujevac (Ždraljica)-Velika Pčelica-Bogalinac ~8 km west of Rekovac. A significantly smaller diabase massif is present along the same tectonic line, further toward SE, at Prevešt village by Kalenicka River, approximately 13 km south of Rekovac. Drača open pit mine is situated in this diabase massif. Geologic explorative works have confirmed the reserves of 1 846 695 t of stone mass for building purposes. For over a decade, Draca mine has been producing various types of building stone, mainly graded stone aggregate with favourable physico-mechanical properties for road-construction works. Chemical analyses and petrographic study have shown typical composition and fabric for this type of rock. Main constituents are plagioclase and pyroxene, with opaque minerals as accessory and varying secondary minerals – chlorite, calcite, in some places epidote and limonite. Pyrite enrichment is visible in some areas of the massif. Chlorite, calcite, epidote and pyrite are the products of propylitic alteration. Although products of alteration are present throughout the rock mass with variable intensity, as is typical for the basic rocks of the former ocean floor sequences, petrologic properties are favourable for building stone purposes. Physico-mechanical properties of diabase have favourable values and varying scattering degrees. Dry state uniaxial compressive strength average values from seven analyses vary in the range 130-169 MPa. Resistance to abrasion average values vary in the range 9.04-17.07 cm3/50cm2. Apparent density varies within the span 2759-2926 g/cm3 and real density 2804-2951 g/cm3. Water absorption values 0.08-1.04 %. Resistance to weathering through testing of stability using Sodium-sulphate values vary from 0.00 to 0.15 % and through frost resistance from 0.00 to 0.04 %. Porosity values are almost constant at 0.8 %. In more altered parts of the rock mass, porosity reaches 1.6 %. Graded crushed aggregate has favourable values of Los Angeles coefficient 14.2 and 14.3 % for gradation B. Taking into consideration all performed tests and analyses, it is concluded that diabase from Drača mine can be used as a building stone for production of aggregate for use in concrete and for road-construction (asphalt paving mixtures for moderate, light and very light traffic load as a top wearing layer; for lower and upper bearing layers; for classic and modern road foundations); for production of crushed and hewn stone for building; crushed stone for railroad ballast. Also, it can be and is used as a raw material for production of stone wool for thermal insulation purposes.

Features of biodiversity of the Uchursky landscape nature reserve (Ayano-Maiskoye district of Khabarovsk Territory)

It was revealed that the botanical and geographical feature of the vegetation cover of the Uchursky complex nature reserve is its position in the zone of convergence of the continental and monsoon climates, claimed by sharply contrasting phlorogenetic elements of the vegetation cover. The gradient of continentality - oceanicity in the vegetation cover is quite clearly traced between the eastern and western macroslopes of the mountain systems of the Uchur River basin. A complex history of the formation of the territory, the height difference from 1,000 to 2,000 meters, the variety of rocks created the conditions for the existence of floristic complexes of different ecology and origin. In this regard, on the territory of the nature reserve, an overlap of the marginal zones of plants ranges of oceanic and continental origin was found, which defines the richness of the region’s biodiversity, but makes both species and communities unstable. The uniqueness of the flora of the Geran Ridge was revealed, with the main core formed by species of non-Angarid origin, concentrated on the weathering crust of the basic rocks. The participation of alpinogenic, arctic and arctic-alpine species is noted. The pine-larch forests, which are unique in their species composition, are found on the outcrops of carbonate rocks on the right bank of the Uchur River, opposite the mouth of the Lyalmi River and in the Uchur-Ulkan interfluve. In this area, there are 79 species of endemic highland species of North Asia. The Red Book of Khabarovsk Territory includes 37 species of vascular plants, 4 species of lichens and 1 representative of the kingdom of mushrooms.

Petrographic and Geochemical Studies of the Host Rock of the Chaghoo Copper Orebody in the Southwest of Karaj

The study area is located 5 km southwest of Mahdasht city in Karaj on the Urmia-Dokhtar magmatic arc. In this area, Eocene volcanic and pyroclastic rocks are observed including basaltic andesite lavas, andesite, Trachyandesiticand trachyte lavas, tuff, and ignimbrite, along with plutonic rocks. There are two spectra of basic and acidic for the rocks in the area, of which basic rocks are chemically calc-alkaline in nature.Among the signs of subduction rocks in the area are enrichment in the Ta, Nb, and Ti lavas, as well as the anomaly of the HFSE index relative to the LILE of incompatible elements content. The geochemical and petrogenetic studies indicate the origin of the area’s plutonic rocks and the role of differential crystallization accompanied by the crustal rocks-contamination and digestion of magma in the evolution of the magma forming these rocks. This magma has been originated from the low-grade partial melting of an enriched mantle origin beneath the continental lithosphere with the lherzolite garnet composition at a depth of 100 to 110 km in a post-collision tensile environment. Investigating the fluids involved in the region, the homogenization temperature with the temperature of copper veins formation is between 120 to 306 ° C, with the salinity percentage varying between 6.45 to 15.96% of sodium chloride weight. Accordingly, this metamorphic hydrothermal orebodyis located in the mesothermal category. The presence of sub-faults, joints, and cracks in the host rock has provided a low-pressure environment for a proper place for copper mineralizationas veins.

Metamorphic gabbro and basalt in ophiolitic and continental nappes of the Zermatt region (Western Alps)

The composition of meta-gabbro and meta-basalt occurring abundant and widespread in all nappes of the nappe stack exposed in the Zermatt region of the Western Alp shows distinct patterns related to the geodynamic origin of metamorphic basic rocks. Eclogitic meta-basalts of the ophiolitic Zermatt-Saas Unit (ZSU) show enriched MORB signatures. The meta-basalts (eclogites) of the continental fragment of the Theodul Glacier Unit (TGU) derive from pre-Alpine metamorphic continental intraplate basalts. Meta-basalts (eclogites) from the continental basement of the Siviez-Mischabel nappe (SMN) derive from MORB thus a genetic relation to the TGU eclogites can be excluded. All basic igneous rocks experienced post-magmatic alteration by fluid-rock interaction ranging from processes at the seafloor, in the shallow crust, during subduction zone hydration, in the exhumation channel and late Alpine regional metamorphisms. The consequences of these alteration processes can be identified at various levels in the rock composition data. It was found that the REE data are little affected by fluid-rock alteration. Some trace elements, notably Cs, Rb, and Ba are typically massively altered relative to igneous compositions in all three groups of meta-basalts. Generally, meta-basalts from the TGU and the SMN preserved the features of the original composition whilst the ZSU meta-volcanic rocks experienced massive alteration. For the ZSU meta-volcanic rocks it is evident that Zr was gained and Y lost during high-pressure fluid-rock interaction indicating a mobile behavior of the two elements during HP-metamorphism in contrast to their behavior in hydrothermal near-surface fluid-rock interaction.

Mineral Prοpecting and Lithοlοgical Mapping Using Remοte Sensing Apprοaches in Between Yazihan-Heki̇mhan (Malatya) Turkey

The Remote Sensing processing analysis have become a directing and hopeful instrument for mineral investigation and lithological mapping. Mineral exploration in general and bearing chromites associated with ultrabasic and basic rocks of the ophiolite complex in particular has been successfully carried out in recent years using Remote Sensing techniques. Yazıhan-Hekimhan (Malatya) region of East Taurus mountain belt, ranks second in terms of iron mineralization in Turkey are accepted. The area is characterized by high grade iron ore deposits in use, development and exploration. Lithological mapping and chromite ore exploration of this area is challenging owing to difficult access (High Mountain 2243 m) using the traditional method of exploration. The main objective of this research is to evaluate the capacity of Landsat-8 OLI and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery to discriminate and detect the potential zone of chromites bearing mineralized in Malatya (Yazıhan). Several images processing techniques, Vegetation Mask, Band Ratio (BR), Band Ratio Color Composite (BRCC), Principal Component Analysis (PCA), Decorrelation Stretch, Minimum Noise Fraction and Supervised classification using Spectral Angle Mapper (SAM) exist in previous studies have been performed for lithological mapping. The obtained results show that, BR, PCA and Decorrelation Stretch methods applied on NVIR-SWIR bands of Landsat-8 and ASTER were clearly discriminate the ophiolite rocks at a regional scale. In Addition, SAM classification was applied on a spectral signature of differents ultrabasic and basic rocks extracted from ASTER data. The results are promising in identifying the potentials zones of chromite ore mineralization zones within the ophiolite region. Thus, the techniques used in this research are suitable to detect or identify the high-potential chromite bearing areas in the ophiolite complex rocks using Landsat-8 OLI and ASTER data.