Lithology and Mineral Resources最新文献

A new occurrence of phosphate mineralization (Shankinka) has been explored in the Fedkovskaya River mouth, Ruza district, Moscow region. The most common mineral phases are delvauxite, mitridatite, fluorapatite, and crandallite. The Fe–Ca–Al phosphate occurrences in the region are associated with the Bajocian–Bathonian paleovalleys embedded in Carboniferous rocks and partially filled with Callovian sediments. The structural features of the phosphatization zone along with its enrichment with Co, Ni, Zn, Cu, and REE indicate a possible link between the overlying Oxfordian sediments and phosphate mineralization. The epigenetic phosphate mineralization can be related to the seepage of phosphorus-rich interstitial waters released from the Oxfordian organic-rich sediments into the underlying Callovian friable rocks enriched with Fe minerals.

Dhodak concession is a part of eastern margin of Sulaiman Fold and Thrust Belt formed as a result of complex transpressional interactions during the Indian-Eurasian collision. Study area reveals the compressional structures that provide suitable hydrocarbon traps of Cretaceous age. Different lithological boundaries and structural properties are identified from 2D seismic, amplitude, and frequency derived seismic attributes. Time and depth structural mapping of the Pab Sandstone (Late Cretaceous) demonstrated an ideal doubly plunging anticlinal structure that represents four way closure for hydrocarbons accumulation in the study area. Observed relatively low-frequency anomaly confirms the hydrocarbon-bearing reservoirs. Since hydrocarbon quantity in a reservoir also depends on the generation potential of source rock, so an attempt has been made to estimate the Total Organic Carbon (TOC) of the source i.e. Sembar Formation. The latter was divided divided into three parts based on the calculated TOC using the Δ log R technique. Upper and lower parts of the Sembar Formation chiefly comprise the lower TOC values (1.90 and 2.1 wt %), whereas the middle part comprises the higher TOC values averaging 3.01 wt %.

The article presents the results of studying alteration of the hydrothermal solution composition during its percolation in the Pleistocene sediments drilled by ODP Hole 858B (38.6 m deep) in the northern segment of Middle Valley, Juan de Fuca Ridge (Dead Dog hydrothermal field), 20 m away from the hydrothermal source with a temperature 276°C. Influence of sediments in Units I, IIB, and IID from this hole on the solution composition variation during the solution–sediment interaction has been established. The greatest influence on the solution composition occurred during its interaction with sediments of Units IIB and IID under high-temperature conditions (200–350°C) expressed in enrichment of the solution with a large amount of chemical elements. A possible alteration in the solution composition is shown in the process of solution–sediment interaction during its percolation in the sedimentary cover 250–300 m thick.

The study of terrigenous rocks of the Shatak Complex, which includes rocks of the Kuz”elga and Karan subformations (Mashak Formation, Upper Riphean) revealed numerous rare-earth minerals: allanite-(Ce), monazite-(Se), monazite-(Nd), xenotime-(Y), REE-bearing epidote, and unidentified compounds. It has been established that the detrital zircon plays the role of a selective concentrator of Y, HREE, and Th during the terrigenous rock metamorphism. The comparative analysis showed that rare-earth minerals, such as monazite-(Ce) and xenotime-(Y), in the Shatak Complex differ significantly (in terms of chemical composition) from counterparts in other complexes located on the western slope of the Southern Urals by the presence of Gd in monazite, and LREE (Ce, Nd, Sm) in xenotime. In the case of similar thermobaric parameters of rock metamorphism characterizing the alteration degree of lithostructural complexes in the Southern Urals, the chemistry of mineral formation environment is among the main factors governing the compositional features of rare-earth minerals.

The paper presents the results of studying the material composition of Early–Middle Permian terrigenous rocks of the Reshetnikovo Formation in the Laoeling–Grodekovo terrane of southwestern Primorye. Studies were carried out to reconstruct paleogeodynamic environments of the accumulation of rocks and to determine the tectonic type and composition of parent rocks in sources areas. It has been established that, in terms of mineral and geochemical parameters, sandstones of the Reshetnikovo Formation are petrogenic or “first cycle” rocks. They correspond to arkoses and, only partially, subarkoses and lithite arenites. They are characterized by a fairly high maturity of clastic material. Their appearance is related to the destruction of largely weathered parent rocks in sources areas. Paleogeodynamic interpretation of the obtained data indicates that sedimentation occurred in the Early–Middle Permian in basins of a passive continental margin (intra- and intercontinental rifts and aulacogens). Sedimentation processes were governed mainly by continental sources areas: cratons and uplifted basement blocks, which were projections of the crystalline basement framed by rift zones. Mainly felsic igneous and metamorphic rocks were eroded with the participation of ancient sedimentary rocks. The U–Pb isotopic dating of detrital zircons made it possible to establish the age and possible location of magmatic complexes, whose destruction produced rocks of the Reshetnikovo Formation.

The paper considers data on the composition, age, and formation conditions of the Ulzutui and Kydzhimit sequences, which are ascribed to the Eravna Series of the Eravna Subzone of the Uda–Vitim Zone. The Eravna Series, at least 2400 m thick, is composed of tephroturbidites with a significant amount of lavas and tuffs of felsic and intermediate compositions, with which tectonic-gravitational mixtites are spatially and genetically related. The features of the structure and composition of the Eravna Series indicate the formation of sediments in an open deepening marine basin adjacent to the zone of active volcanism. Based on miospores, the time of formation of the Ulzutui Sequence was constrained, for the first time, to the Late Devonian–Early Carboniferous (late Famennian–early Tournaisian), the Kydzhimit Sequence is limited to the Early Carboniferous (Visean) age. At this time, the Kydzhimit volcanic zone was formed. The suprasubduction nature of the zone is evidenced by the following features of volcanic rocks: predominance of felsic varieties, affiliation of basalts to the tholeiitic series, and dacites and rhyodacites to the calc-alkaline series, the presence of high-K rock varieties corresponding to the K-Na alkalinity, very low MgO contents, low and moderate TiO₂ contents, high Al₂O₃ and K₂O, enrichment of the volcanogenic rocks in large-ion lithophilic elements relatively to high-field strength elements, Nb minimum, and negative εNd, their spatial association with monzonites (with suprasubduction signatures) and tephroturbidites, as well as metallogenic specialization (Cu and Zn) of the Eravna Series. We believe that the ore-bearing sequence for the pyrite–base metal Ulzutui and Ozernoe deposits is the Upper Devonian–Lower Carboniferous Eravna Series.

Based on lithogeochemical data related to the fine-grained clastic rocks of the Volyn, Valdai, and Baltic groups in the western part of the East European Platform (Belarus and Volyn, partly Lithuania), categories of rivers that transported the fine-grained aluminosiliciclastics to the sinks were reconstructed. It is concluded that the formation of Vendian and Lower Cambrian sedimentary sequences in this area was controlled mainly by river systems similar to modern large rivers (catchment area >100 000 km²) and rivers draining sedimentary rocks (catchment area <100 000 km²). The fine-grained aluminosiliciclastics transported by them was delivered mainly from areas composed of rocks of the platform crystalline basement and, in part, sedimentary rocks. The distribution of data points of Vendian–Lower Cambrian mudstones on the (La/Yb)_N–Eu/Eu* and (La/Yb)_N–Th diagrams with fields of the pelitic and silty–pelitic sediments at the mouths of modern different-category rivers shows that mafic rocks of the Volyn–Brest large igneous province, apparently, were not suppliers of the fine-grained aluminosiliciclastics in the indicated time intervals.

New results of the lithological structural–textural observations and petrographic study of rocks of the Uryuk Formation (sandstones and gravelstone-sandstones with the subordinate mudstone interlayers) exposed in the Malyi Tolpar River basin in the Bashkir meganticlinorium. For the first time, a wide development of synsedimentary underwater landslide folds (varying from the first tens of centimeters to the first meters in size) has been established in the Uryuk deposits. The sandstones demonstrate the oblique, wavy, flaser, and horizontal (with paired thin clay lamina) stratification, as well as massive layers. Signs of shallow wave ripples have been established. The rocks are characterized by mechanoglyphs and textures similar to Arumberia banksi, which presumably represent the lithified textures of bacterial mats that existed under shallow-marine environments with sandy–clayey sedimentation. Despite the absence of direct lithological signs of diamictites, the Uryuk deposits likely form a single sedimentary sequence with the underlying Tolparovo–Suirovo marine glacial deposits, in which a shallow-sea sedimentation regime was established by the end of the Uryuk time. It is shown that the presence of ferruginous minerals in the sandstone cement is secondary in nature and is associated with their epigenetic transformations. It is concluded that the red color of rocks of the Uryuk Formation cannot be used for the stratification of its sections and reconstruction of sedimentation conditions in the Uryuk time.

The first results of the U–Th–Pb isotope dating of detrital zircons (dZr, N = 130, n = 91) from the middle Danian sandstones (63.9–65.3 Ma) of the Cretaceous–Eocene Novorossiisk–Anapa flysch widely developed in the Sochi synclinorium (southern slope of the Western Caucasus) are presented. The maximum and minimum dZr age is 2973 ± 12 Ma and 318 ± 3 Ma, respectively; weighted average age of the four youngest dZr is ~322 ± 7 Ma. There are no signs of erosion products of the Jurassic magmatites involved in the structure of the Greater Caucasus and Crimean Mountains into the sedimentary basin, where the Novorossiisk–Anapa flysch was formed. The results have revealed a high degree of similarity between the provenance signals of the Danian sandstones from the Novorossiisk–Anapa flysch, some Paleogene–Neogene and Early Quaternary (Early Pleistocene) sandstones of the Western Caucasus and Western Cis-Caucasia, red-colored Upper Permian and Lower Triassic sandstones of the Moscow syneclise, as well as Late Quaternary alluvium at lower reaches of the Don and Volga rivers draining vast expanses of the Russian Plate. These facts suggest: (1) the absence of eroded mountain structures of the Greater Caucasus and Crimea in the middle Danian; (2) the main volume of detrital material composing the Novorossiisk–Anapa flysch was formed due to the recycling of Permian–Triassic and younger sequences of the Russian Plate.

In two marginal depressions of the East European Platform (Pechora Syneclise and Caspian Basin), reef structures are widespread, but their stratigraphic intervals are far from similar. The reef formation began in the Caradocian in the Pechorian Ural, in the second half of the Llandoverian in the Pechora Syneclise, reached the maximum in the Frasnian, and gave way to the development of reef mounds in the Famennian. The structures are represented both as asymmetric reefs framing shallow zones at their boundary with the relatively deep paleobasins and as solitary structures within the latter. Reefs of the next global maximums (late Visean–Serpukhovian and Lower Permian) are confined to some places at the boundary with the Ural paleocean and its relict (Cis-Ural foredeep). The Caspian Basin accommodates reefs of all three global maximums of development—both asymmetric reef systems framing the shelf edges and symmetric intra-basin isolated structures. Such difference is due to the different paleogeomorphological type of basins. The Caspian Basin was sharply differentiated in depth throughout the Middle and Late Paleozoic, resulting in the formation of reefs rising above the bottom of these basins. In the Pechora Syneclise, depth differentiation of the basins occurred only in the Late Devonian. The Visean–Serpukhovian and early Permian shallow seas were generally weakly dissected and did not provide conditions for the formation of thick reefs protruding above the seafloor. Such reefs were formed only on the Ural paleocean edge in the Visean–Serpukhovian and on the Cis-Ural foredeep edge in the Permian.