Petrochemical Characteristics Research Articles

KIBARAN GRANITOID MAGMATISM IN THE REPUBLIC OF BURUNDI: GEOLOGY, COMPOSITIONAL FEATURES, TIME AND GEODYNAMIC CONDITIONS OF OCCURRENCE

The paper examines the specific granitoid magmatism of the northern sector of the Kibaran orogenic belt in the general context of geodynamic typification of granitoids. It presents parameters and main features of the structure with an emphasis on the sectorial nature of the belt typical of intraplate settings and shows the geological features of the eastern and western blocks of the northern sector. The paper provides general information on S- and A-type granitoids and a description of the geological position and macrofeatures of "reference" massifs. The petrochemical characteristics of S- and A-granitoids are given using various diagrams. Analysis of geochronological database available to date (including Rb-Sr isochron age of rocks and SHRIMP U-Pb age of zircons) shows the multi-pulse nature of the manifestation of intraplate granite formation. Along with the main stages (~1375, ~1205, ~986 Ma), there are five others. Based on the total dataset, S-type granitoids in Burundi are characterized by the crust-mantle interaction signs which are somewhat contrary to the generally accepted opinion that they are purely crustal. At the same time, some varieties of A-type granitoids are characterized by corundonormativity which makes them more similar to the S-type. Thus, signs of convergence between S- and A-granites are characteristic of some intraplate environments such as "hot spots", primarily of those longlived and multi-pulse, with the relevant protolith represented by a complex of sediments with high exogenous differentiation. One of the version of the granite formation model is illustrated by the corresponding figure.

Petrological and geochemical features of Middle Paleozoic basites in the Muna-Tyung interfluve region

The discovery of kimberlite pipes containing diamonds in the Viluy-Markha dyke belt led to a surge in interest in studying the products of Middle Paleozoic basic magmatism associated with these pipes in terms of their spatial and temporal characteristics. A distinct group of high-titanium rocks linked to diamond-bearing kimberlites was identified among the basic intrusions, serving as a key indicator for locating kimberlite pipes. This discovery prompted further research on basites and potential areas, such as the northeastern region of the dyke belt within the Muno-Tunga interfluve region, where alluvial diamonds have been found but their original sources remain unidentified. The presence ofdiamond varieties typical of kimberlites with high diamond concentrations in the placer diamonds of this area suggests the possibility of a new kimberlite field. The study of Middle Paleozoic basites in the Muno-Tunga interfluve region revealed high-titanium basites with similar petrochemical characteristics to those associated with diamond-bearing kimberlites. These basites are situated on the flanks of the dyke belt marked by compensating compression, making them a promising indicator for kimberlite prospecting. This study has demonstrated that areas with preferential compression are highly prospective for identifying primary diamond deposits.

THE BABYNSKA SUITE TUFFS OF THE CONTINENTAL FLOOD BASALTS OF WESTERN VOLYN: MINERALOGY, PETROGRAPHY, PETROCHEMISTRY, GENETIC AND APPLIED SIGNIFICANCE

According to the data of comprehensive precision research, the spatial distribution and mineral composition were revealed, the petrographic and petrochemical features, and the genetic and practical significance of the Babynska effusive-pyroclastic suite tuffs of the continental flood basalts of Western Volyn were clarified in connection with the copper content. The thicknesses and hypsometry of the relief of the paleosurface of the pyroclastic formations of the Babynska suite were analyzed and the important elements of its vertical and lateral structure (by area) were clarified, the real picture of which is reflected in the constructed maps of the thicknesses and relief of the paleosurface of the pyroclastic formations of the suite, in particular, on the Ratnе–-Kamin-Kashyrsk Area. The formation of the Babynska suite tuffs in the regime of gravitational deposition of pyroclastic material with the accumulation of tuff deposits at the stage of incomplete solidification of volcanic material and the formation of coarse, non-rhythmic layering, without clear signs of redeposition, i.e. of volcanomictіс origin, has been proven. Differences in the mineral composition and petrochemistry of tuffs of different colors: gray-green and red-brown were found. Emphasis is placed on the enrichment of native copper in tuffs of gray-green color and possible explanations for this correlation are proposed. The obtained results from a genetic point of view provide important information for paleovolcanogenic and paleogeographical reconstructions, in practical terms they contribute to the improvement of the copper bearing prospects of volcanogenic layers of the continental flood basalts and can be proposed for use by production organizations of the geological profile.

Middle Triassic basaltic pyroclastic rocks from the Mt. Medvednica ophiolitic mélange (NW Croatia): petrology, geochemistry and tectono-magmatic setting

Hectometric blocks of Middle Triassic mafic pyroclastic rocks, represented by volcanic agglomerates/breccias and lapilli tuffs, form part of the ophiolitic mélange of Mt. Medvednica, situated in the southwestern segment of the Zagorje-Mid-Transdanubian Zone. These rocks share petrochemical characteristics with pyroclastic derivatives of alkali, within-plate basaltic lavas of Mts. Medvednica, Samoborska Gora, and Kalnik, indicating the occurrence of explosive events preceding the dominant effusive submarine volcanism during the Middle Triassic (Illyrian-Fassanian?) stages. The formation of these pre-ophiolitic pyroclastics is associated with an intracontinental rift setting and reflects melts derived from an OIB-type enriched mantle plume source. These pyroclastics represent uncontaminated melts that erupted through a highly thinned continental crust. In geodynamic terms, the formation of pyroclastites occurred during the Late Anisian-Early Ladinian along the continental margin of Palaeotethys through the proto back-arc rifting of continental lithosphere (Adria Plate), leading to the formation of the Maliak/Balkan Neotethys Rift, in the emerging northwestern segment of Neotethys. The investigated pyroclastic rocks of Mt. Medvednica document the extension in an evolved intracontinental rift basin, which immediately preceded the generation of the initial Neotethyan oceanic lithosphere during the Upper Triassic.

Metasomatism in the Precambrian Crust of the Siberian Craton: Results of a Study of Garnet(±orthopyroxene)-biotite-feldspar Xenolith Rocks From Yubileinaya and Sytykanskaya Kimberlite Pipes, Yakutia

Xenoliths in kimberlites are the most perspective objects for studying the composition and structure of the lower levels of the continental crust. Present work is aimed at estimation of P-T fluid conditions of metamorphism for garnet-biotite-feldspar and orthopyroxene-garnet-biotite-feldspar rocks represented as xenoliths in kimberlites of the Yubileynaya and Sytykanskaya pipes, Yakutian kimberlite province. Seven studied samples show inverse dependences of relative contents of garnet and orthopyroxene, orthopyroxene and biotite, garnet and plagioclase, plagioclase and potassium feldspar. This indicates a consistent series of transformations of the assemblage garnet + plagioclase + orthopyroxene ± quartz to the assemblage garnet + biotite + potassium feldspar. In this process, the replacement of plagioclase by potassium feldspar was the leading reaction. Now it is represented by specific reaction textures in the rocks, negative correlations of the mineral contents, as well as in petrochemical characteristics of the rocks. Modeling of xenolith mineral assemblages using the pseudosection approach (PERPLE_X) revealed two groups of rocks corresponding to different depth levels of the Siberian cratonic crust. For rocks where orthopyroxene is absent or is present as single relics, pressure estimates are 9.5–10 kbar, and it is 6–7 kbar for orthopyroxene-bearing samples. The xenolith rocks have close metamorphic peak temperatures of 750–800°C. They experienced 200–250°C cooling and 3–4 kbar decompression, regardless of the level of the crust at which they were initially located. This points to the metamorphic evolution of the rocks during their exhumation, probably associated with collisional processes during the amalgamation of individual terrains of the Siberian craton. Xenoliths enriched in K-feldspar might have been products of metamorphic reactions with participation of aqueous-(carbonic)-salt fluids, which were sourced from basaltic magmas in the lower crust. The most metasomatized rocks were located closest to the place of accumulation of crystallizing magmas.

Maskelynite- as seen in shocked Lonar target basalt, India, and martian and lunar meteorites

In this study, we investigate the mineralogical and petrochemical characteristics of maskelynite occurring in a shocked basalt boulder from a terrestrial impact crater on a basaltic target – the Lonar impact crater in India, and the martian and lunar meteorites. The majority of Lonar maskelynite experienced solid-state transformation and maintained almost a uniform chemical composition, consistent with the unshocked feldspar. The locally flow-like texture and marginal vesiculation in feldspathic glass are needed in interaction with the impact-melt. The vesiculated melt occasionally occurring at the margins of maskelynite is characterised by Na-loss due to the shock-induced volatility. A shock pressure of ≤42 GPa and at a temperature of ≤1000 °C appear consistent for the formation of Lonar vesiculated melt/ feldspathic glass. Under the impact-induced shock metamorphism, maskelynite samples from the moon retain both the crystalline and amorphous domains with a distinct chemical heterogeneity attributed to different shock metamorphism effects of the plagioclase. In contrast, the martian maskelynites exhibit a smooth, homogeneous composition. The estimated shock pressure is relatively higher at ∼42–45 GPa based on experiments and models. The difference in Si/Al ratio in lunar (1–1.3) and martian maskelynite (1.5–1.9) suggests its inherent difference in composition of the crust, whereas the Lonar maskelynite shows overlapping composition with the martian maskelynite contending Lonar basalt as a potential terrestrial analogue to the martian crust.

Метабазиты р. Лунвож (Средний Тиман): петрография, минералогия, петрохимия

A small dike of unknown age was found on the territory of the Kanin-Timan region within the Middle Timan along the Lunvozh river. Our studies revealed that the rocks, composing this intrusive body, corresponded to basaltic andesites according to the content of the main rock-forming elements. They were almost completely recrystallized and composed of chlorite (30—40 %), carbonates (25—40 %), albite (10—15 %), quartz (10—15 %), muscovite (5—8 %) and plagioclase (less than 1 %). Accessory minerals were represented by apatite, monazite and rutile. Ore minerals included pyrite, chalcopyrite, and cobaltine. According to the mineral composition and petrochemical characteristics, the rocks composing the dike body along the Lunvozh river, differed from the basites of the Middle Riphean Middle Timan and Devonian Kanin-Timan complexes identified in the Kanin-Timan region.

Zircon and cassiterite U-Pb geochronology and petrochemical characteristics of early Tertiary tin mineralization at Mayo Darlé, Cameroon Volcanic Line

Tin mineralization at Mayo-Darlé in the Cameroon Volcanic Line is associated with highly evolved anorogenic ferroan granite magmatism with a pervasive hydrothermal overprint. Mineralization occurs as cassiterite-quartz-muscovite stockwork and disseminated in quartz-mica and quartz-topaz greisen in low-Ca alkali feldspar granite with a composition near the 1 kbar haplogranitic thermal minimum. The trace element composition of zircon indicates elevated temperature (880 ± 55 °C) and very low oxidation state below the quartz-fayalite-magnetite buffer. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) identifies a partly disturbed U-Pb system for igneous zircon (U and Th contents >1000 ppm) but defines Tera-Wasserburg concordia ages and common-lead-corrected weighted 206Pb/238U ages of about 54 Ma, similar to a previous 87Rb/86Sr vs 87Sr/86Sr regression with a date of 56.1 ± 1.7 Ma (MSWD = 58; n = 9) and an initial 87Sr/86Sr ratio of 0.7085 ± 0.0035 (2 s). Hydrothermal cassiterite gives a pooled LA-ICPMS Tera-Wasserburg concordia age of 56.7 ± 0.6 Ma on two samples (each about 20 points, MSWD = 0.54 and 1.3). These new age data define a period of early Cenozoic intraplate calc-alkalic felsic magmatism as a precursor to abundant Oligocene to Recent alkali basalt volcanism along the Cameroon Volcanic Line. Geochemical and Sr–Nd–Hf isotopic data suggest that the granitic rocks from Mayo Darlé were largely derived by partial melting of Mesoproterozoic basement and modified by strong differentiation, all likely powered by heat (and possibly fluids) from the mantle. The Tertiary age of the rare-metal magmatism sets this system apart from the widespread Late Neoproterozoic to Early Paleozoic rare-metal pegmatites and granites in the Pan-African collisional belts of Africa, and also from the anorogenic Mesozoic ring complexes in Central Nigeria.

Complex characteristics of suevites at the B. Vanuyta river (Kara astrobleme, Russia)

Research subject. Suevites from the eastern sector of the Kara astrobleme, located in the basin of the Bolshaya Vanuyta river. Aim. To identify the suevitic type and to clarify the facial features of the suevites from the B. Vanuyta River. Materials. Hand-size samples of suevites collecteed in the basins of B. Vanuyta, Anaroga, Kara, and Sopchayu rivers, as well as samples of siltstones collected outside the Kara crater (rivers Halmeryu, Sayakha, Putyu, Anaroga and the creek Lavovyi). The samples were used for preparing polished thin sections and powder specimens for analytical works. Methods. Field observations, optical and electron scanning microscopy, and silicate analysis by the wet chemical method. Results and conclusions. The structural-textural and petrochemical features of the matrix, fragments of impact glasses, and lithoclasts of suevites from the B. Vanuyta river were characterized. The suevite matrix was found to exhibit an intensely sintered character and to be presented by feldspar, quartz, calcite, chlorite, muscovite, glauconite, and titanite. Lithoclasts include siltstones, sandstones, limestones, mudstones, and shales. Vitroclasts are characterized by angular and irregular morphology with different border patterns, and spotted, fluid, and porous textures. The similarity of the chemical composition of siltstone clusters and similar target rocks confirms the genetic relationship and the leading role of this type of target rocks in the formation of the studied suevites. The proximity in the composition of the impact glasses of the studied suevites and the glasses of type I and II suevites indicates the formation of suevite vitroclasts in the river B. Vanuyta by a similar protolith – siltstones and a clay component of the limestones. The matrix lithification character, morphology and nature of the vitroclast outlines indicate that the suevites from the B. Vanuyta river are the rocks of an aerodynamic facies formed under relatively high-temperature conditions, which structurally lie at the lower part of the detrital impactites sequence of the aerodynamic facies. The studied rocks are close to the type I suevites by the composition of the protolith and differ in the conditions of their formation. With the type II suevites, they have similar facies characteristics, but differ in the composition of the target rocks fragments. It is determined that the leading factor in the typification of suevites from the Kara astrobleme is the chemical composition, at the same time, the types can be subdivided more fractionally based on the specifics of the facies environments of their formation.

Petrogenesis of Late Cretaceous A-type plutonic rocks from the Eastern Pontides Orogenic Belt (NE Turkey): constraints from zircon U-Pb geochronology, zircon Lu-Hf and whole-rock Sr-Nd-Pb-Hf isotopes

ABSTRACT The Late Cretaceous magmatic history of the Eastern Pontides Orogenic Belt (NE Turkey) was generally characterized by common I-type and lesser A-type plutons in varying size and composition. Of these, A-type plutons from the Şebinkarahisar (Giresun) area yield SHRIMP zircon U-Pb age of 77.36 ± 0.96 Ma. The rocks of these plutons display a wide range of SiO2 contents (53.63 to 70.96 wt.%) and Mg-numbers (6.2–32.19) with A-type affinities characterized by enrichment in K2O and Na2O, Ga, Zr, and strong negative Eu anomalies. They also show arc-type petrochemical features including enrichment of large-ion lithophile elements (e.g. Cs, K, Rb) and light rare earth elements (LaN/LuN = 6.27–15.61), but depletion in high strength field elements (e.g. Nb, Ta, Ti, and P). The (87Sr/86Sr)i ratios and ɛNd(i) values of the studied rocks are in the range of 0.705129 to 0.0705347 and −3.64 to −3.12, respectively, while bulk rock ɛHf(i) values are between 1.86 and 4.36. They are characterized by positive zircon ɛHf(i) (1.74 to 10.88) plotting between the chondrite and depleted mantle evolutionary line values. Our data combined with the previous studies suggest that the magmas, that formed the Late Cretaceous plutons, were generated in an extensional tectonic environment due to slap roll-back and trench ward migration of the subduction zone to the south. The generation of hybrid magmas forming the studied plutons is in response to the melts derived from a metasomatized lithospheric mantle source, a relatively deeper mantle source, and the juvenile crust along with the heat transfer and decompression. Multi-sourced magmas rise through the continental crust and reach the final composition by predominantly fractional crystallization processes.

Munabulake ophiolitic mélange: Implication for the evolution history of the north branch of the Proto-Tethys ocean

One of the ophiolites that record the Proto-Tethys Ocean’s episodic closure is the Munabulake ophiolitic mélange, which is situated in the middle of the Kunlun–Qaidam and Altun–Qilian blocks. Detailed field mapping revealed that the Munabulake ophiolitic mélange comprises local (ultramafic rocks, basalts, andesites, gabbros, diorites, and plagiogranites) and exotic (marble, gneiss, schist, and amphibolite) blocks, many of which are in the schist matrix (Qimantage Group). Based on geochronological, geochemical, and petrological observations, the mafic rocks in the Munabulake ophiolitic mélange can be categorized into three categories: 498-Ma OIB-like gabbros, 468-Ma Hawaiian alkaline basalt-like dolerite and pillow basaltic slices, and 428 Ma massive SSZ-like ultramafic rocks. The 501–452 Ma I-type granites exhibit arc affinities due to the oceanic crust subduction. These findings, along with spatial relationships, suggest that the Early Paleozoic ophiolite complex, island arc rocks, and accretionary complex generated as an intra-oceanic arc system as a result of obduction of the south Altun Ocean’s onto the Central Altun block within a north-directed subduction event. A dextral strike–slip was evident throughout the Early Paleozoic oceanic crust subduction based on the whole set of planar and linear structural data, and the subduction polarity was likely to the north. According to the ophiolitic mélange’s youngest rocks and the existence of 413 Ma granite dykes that are widely exposed in the Munabulake ophiolitic mélange, the Munabulake ophiolitic mélange was most likely emplaced during the Middle Silurian. This Munabulake ophiolitic mélange is similar in age and petrochemical characteristics to the other ophiolites in the South Altun subduction–collision belt, indicating that the Manabulak ophiolite mélange is a westward extension of the Apa–Mangya subduction–collision belt, which formed during the northward subduction of the South Altun Ocean slab during the Early Paleozoic. Thus, the final closing time of the South Altun Ocean is between 413 and 428 Ma.

Geological Structure Features and Rocks Composition of Kronotsky Volcano, the Largest Stratovolcano in the Frontal Zone of the Eastern Volcanic Belt of Kamchatka

Based on the results of 2020‒2022 field works, this paper presents a characterization of the geological structure and whole rock composition of Kronotsky volcano, one of the poorly studied eruptive centers of the Eastern Volcanic Belt (EVB) of Kamchatka. The volume of the volcanic edifice is estimated at 350 km3, that significantly exceeds the volumes of other stratovolcanoes of the frontal zone of EVB. Rocks of a volcano are presented by low-K, high-Fe tholeiitic basalts and basaltic andesites (SiO2 = 47.04–53.15 wt %; K2O = = 0.24‒0.65 wt %; FeO*/MgO = 1.2‒2.89). The basalts show extremely low contents of silica, potassium, titanium, and phosphorus in comparison with rocks of other frontal volcanoes of Kamchatka. The revealed petrochemical features were used to clarify the belonging of the objects located at the junction of Kronotsky and Krasheninnikov volcanic edifices. The obtained data will serve as the background for further petrological and geochemical studies of the volcano, and also may be used for reconstruction the sequence of volcanic events in this area, including clarification of the history of Kronotsky Lake formation.

Research on Strategies of Specialty Construction of Environmental Disciplines in the Context of Petroleum and Petrochemical Characteristics

In the context of the new era, with the focus on talent training, "government, industry, academia and research" integration, environmental disciplines construction deficiencies are increasingly apparent, in view of its problems, in the context of petroleum and petrochemical characteristics of the construction of the whole process of the linkage mechanism, a full range of evaluation system. This article not only provides comprehensive guidance for the construction of the environmental discipline in our school, but also provides effective mechanism and method guarantees for the deep integration of the demand side of senior environmental protection professionals and the supply side of universities exporting talents to the chemical industry. It has important practical and far-reaching strategic significance for the construction and development of the environmental discipline in our school.

PETROCHEMICAL AND STRUCTURAL CHARACTERISTICS OF PORPHYRY COPPER MINERALIZATION IN THE ASTANEH ORE DEPOSIT, MIDDLE PART OF THE URUMIEH-DOKHTAR MAGMATIC ARC (IRAN)

Within the Urumieh-Dokhtar Magmatic Arc in the central part of Iran, the formation of which is associated with the Neotethys closure, there are many porphyry copper deposits and ore occurrences. One of them is the Astaneh porphyry copper ore deposit, located in the central part of the Saveh-Ardestan ore region southeast of Ardestan city. The purpose of this study is to investigate the petrochemical characteristics of rocks and to determine the relationship between the distribution of porphyry copper mineralization and tectonic position of faults within the study area. To achieve the goal, there were used the structural and geological data obtained in the fieldwork, as well as the results of mineralogical and geochemical analyses. The obtained results show that rocks of different composition of the Astaneh ore deposit (andesite, andesite-basalt, basalt, trachybasalt) were formed in the suprasubduction zone, and probably in the environment prior to the collision of the of continental plates. Paragenetic relationships and mineralogical analysis show that the evolution of mineralization of the Astaneh ore deposit can be divided into three stages: pre-ore, hypogene and supergene mineralization. Geochemical research based on the study of the content of the major chemical elements in the rocks of the region shows that igneous rocks belong to calc-alkaline basalts and geodynamically can be attributed to the products of magmatism of the ensial island arc. The results concluded that the main stages of the formation of a porphyry copper ore deposit in the study area attain maximum spatio-temporal similarity with the tectonomagmatic phases of the development of the Neotethys Ocean. In addition, the Southern Ardestan fault, running through the study area and intersecting the basement structures, forms wide permeable zones favorable for the formation of porphyry copper deposits therein.

Heterogeneity in kimberlite structure and composition as a reflection of its petrogenesis peculiarities

New data on the geological structure and petrochemical characteristics of the first kimberlite pipe in the Syuldyukar kimberlite field and its position in the Ygyatta diamond-bearing area are presented. The petrographic identification of the petrochemical varieties of kimberlites in this area was performed for the first time. The compositions of the rockforming and accessory minerals of kimberlites were studied using a modern hardware complex. The results showed that the directed change in the structural and material characteristics of kimberlites from peripheral to central parts in extended vertical bodies of the Syuldyukar tube type is expressed in the replacement of calcium kimberlites by magnesium kimberlites. Mg-kimberlites are characterized by the largest crystals of diamond, garnets, and ilmenites, high concentrations of magnesium, and a number of other components. All of these changes in kimberlites are caused by flow differentiation. This information allowed us to apply the obtained petrological results to the kimberlites of the Syuldyukar tube as search criteria for forecasting and identifying new kimberlite bodies in the Ygyatta diamond-bearing area.

”MINERALOGY OF IGNEOUS COMPLEXES OF WESTERN VOLYN” – THE FIRST FUNDAMENTAL MONOGRAPH ON REGIONAL MINERALOGY IN UKRAINE

The contribution of the authors of the monograph “Mineralogy of igneous complexes of Western Volyn”, headed by Academician Yevhen Kostiantynovych Lazarenko, to the mineralogy of igneous rocks of the region is highlighted. The results of a detailed geological and mineralogical study, a geological and petrographic essay and the characteristics of mineral formation processes of Archean metamorphic and Zhytomyr-Kirovohrad and Osnitsk intrusive as well as dyke-effusive igneous complexes are discussed. It is shown that the materials obtained by the authors of this first fundamental monograph on regional mineralogy of Ukraine, together with the full use of literature at the time, formed the basis for all subsequent studies of Western Volyn, given its prospects for identifying of copper fields within the Volyn series of the Lower Ediacaria flood continental basalts. The obtained results, together with а set of data obtained later, made it possible to justify the need to intensify targeted efforts in the region. In the future, special attention should be paid to continuing the detailed study of the geological structure, mineral composition, petrographic and petrochemical features of rock-ore complexes of Western Volyn, the fluid regime of mineralogenesis of copper-containing flood continental basalts. Further research in the region will contribute to detailing the conditions for the formation of native copper mineralization in traps of the Volyn series in the aspect of assessing their copper ore potential; their results should be used by production geological organizations to optimize prospecting and exploration work in the preparation of promising areas for exploration. The significance of Yevhen Lazarenko’s contribution to regional mineralogical research, which was initiated by the monograph “Mineralogy of igneous complexes of Western Volyn”, is growing under these conditions. The book is still a powerful source of inspiration for geologists who continue the work of an outstanding scientist in the field of Earth sciences and conduct regional mineralogical research not only in Volyn, but also in other regions of Ukraine.

Rare Earth-Mineralogical and Petrochemical Characters of Syenite Rocks of Rairakhol Alkaline Complex, Odisha, India

Rare Earth-Mineralogical and Petrochemical Characters of Syenite Rocks of Rairakhol Alkaline Complex, Odisha, India

Some geological and petrological characteristics of the Eocene trachybasalt-trachyandesite- basalt-phonolite formation of the Talysh zone (Azerbaijan)


 
 
 This article discusses the stages of crystallization of the Eocene trachybasalt-tra- chyandesitebasalt-phonolith formation of the Talysh zone. Determination of the composi- tion of the primary magma, evolution and melting fraction of the initial melt of the Eocene volcanism of the Talysh zone within Azerbaijan. Eocene volcanism of the trachybasalt-tra-chyandesitebasalt-phonolith formation of the Talysh zone. Petrographic, petrochemical, geochemical studies of rocks, typomorphic features of mineral paragenesis, chemical composition of rocks were carried out by X-ray spectral and X-ray fluorescence analysis. The analyzes of the conducted studies show that the Talysh zone was formed in the Eocene time. Stages of evolution of the original magma and typomorphic features of mineral parageneses have been established. The distributions of microelements in mineral parageneses, which are direct participants in the crystallization processes that took place in intermediate chambers at different depths, have been studied. At present, the question arises of the need to clarify the typomorphic features of igneous complexes, as factors that determine the geodynamic regimes of their formation, and to determine the potential ore content. The petrographic and petrochemical characteristics of the volcanic rocks are given. It was found that if the process of differentiation in the Early-Middle Eocene was more distinct with the initial formation of more magnesian rock varieties (picrite-trachybasalts), and subsequently more ferruginous ones (trachyandesites and trachyandesitebasalts), then such accumulation of iron is not observed in porphyritic trachyandesites. This petrochemical feature is obviously associated with the duration of the break in volcanism, caused by the formation of a thick sedimentary-tuffaceous stratum, accompanied by the initiation and manifestation of an intermediate chamber of medium composition. Volcanism in the Late Eocene was undifferentiated and was not accompanied by the formation of medium differences. The appearance in the late Eocene of leucite phonolites, which represent an alkaline branch, and the absence of transitional varieties indicate the autonomous development of vit- robasalts and leucite phonolites. It is concluded that from the early phases of the manifestation of Eocene volcanism to the later phases, the change in the material composition along the lateral is expressed in the manifestation of more alkaline facies with a significant predominance of K over Na and with a greater correspondence to the differentials of the shoshonite series.
 
 

Typification of volcanogenic deposits of the Carboniferous complex of the Mindyak graben-syncline of the Voznesensko-Prisakmarskaya structural-formational zone of the Southern Urals

The results of the studies show that the volcanogenic deposits of the Carboniferous complex of the Mindyak graben-syncline in the Southern Urals were formed as a result of successively manifested synsedimentary volcanism: early moderately alkaline basaltoid fissure type and subsequent moderately alkaline basalt-basalt-andesite-dacitic type, more extensive in the area. 
 According to the conditions of localization, composition and petrochemical characteristics, the considered volcanic rocks are comparable with typical for the Ural-Tien Shan region volcanogenic deposits of the Varissky rift structures of deep fault zones (Magnitogorsk-Bogdanovskaya in the Southern Urals and Boztau-Kokpatasskaya in the Southwestern Tien Shan). Together they can serve as indicators for the riftogenic settings of the Late Paleozoic early orogenic (early collisional) tectonic-magmatic activation of this region. 
 The obtained data can be used to refine the geological structure and metallogeny of the Southern Urals.

Vein formation of the Monchepluton and the Monchetundra intrusion contact zone

The Monchegorsk region (Kola Peninsula) is distinguished by its platinum metal specialization and is a promising target for prospecting and exploration of valuable, strategically important platinum group metals. In the course of the study, the petrographic, petrochemical, and geochemical features of the vein bodies in the junction zone of large Early Proterozoic layered intrusions (the Monchegorsk pluton and the Monchetundra intrusion) have been characterized. Vein bodies are observed within the South Sopchinsky massif and the Moroshkovoe Lake massif. The veins are located near the contact of fine-medium-grained metapyroxenites (metanorites) and coarse-grained gabbronorites. Two main types of veins are identified: 1) veins of plagioclase-pyroxene and plagioclase-amphibole composition and 2) veins of quartz-feldspar and amphibole-plagioclase composition. Analysis of the content of chalcophilic elements in this area rocks has shown that the increased content of platinum group elements is associated with the first type of vein formations. Vein rocks of plagioclase-pyroxene and plagioclase-amphibole composition (type 1) contain on average Cu - 0.22 %, Ni - 0.11 %, ΣPGE - 1 g/t, Au - 0.042 ppm. Vein rocks of quartz-feldspar and amphibole-plagioclase composition (type 2) contain on average Cu - 0.04 %, Ni - 0.01 %, ΣPGE - 0.05 ppm, Au - 0.012 ppm. The distribution spectra of rare-earth and rare elements in the vein rocks of the South Sopchinsky massif and the Moroshkovoe Lake massif show both the commonality of all types of veins and the regular nature of differences in the composition of the veins.