Hasil untuk "Petrology"

Nicy Carmel Bazebizonza Tchiguina, Prefina Risiany Rachelle Samba, Hardy Medry Dieu-Veill Nkodia et al.

Karst systems are increasingly recognized as valuable geoheritage sites. Although Africa hosts numerous karst landscapes, few countries maintain comprehensive inventories. Here, we investigated the karstic cavities within the Schisto-Calcaire Group in the Republic of the Congo and assessed their geoheritage potential. We identified 169 karstic cavities by compiling data from publications, speleological reports, and field expeditions mainly in the Bangou Forest, the Madingou and Loudima valley regions. The inventory shows that 42 cavities have archaeological or anthropological significance. The Madingou region was selected as a focal point for fieldwork due to its high concentration of karstic cavities. This led to the discovery of 24 new cavities and revealed advanced karst development, including cone karst morphologies (fengcong, fenglin), dolines, uvalas, and karst springs. These cavities host diverse speleothems, cave-dwelling fauna, and ceramic remains. The geomorphological features result from interactions between lithological variability, tectonic structures, and surface processes. The geoheritage potential was assessed using a six-criterion classification framework encompassing geomorphology, hydrology, endokarst, lithology-palaeontology, tectonics-structural, and archaeology. The results underscore the high scientific, touristic, and educational value of the Madingou karst, highlighting the need for geoconservation strategies and sustainable tourism development. This study marks the first implementation of a systematic inventory approach toward geoheritage promotion in a Congolese karstic region and in Central Africa. This approach offers a replicable model for other areas. Linking geoheritage to sustainable land management contributes to SDG 11.4 on safeguarding cultural and natural heritage, as well as SDG 4 (Quality Education), SDG 13 (Climate Action), and SDG 15 (Life on Land).

Christian Leipe, David Handfried, Tengwen Long et al.

Here, we present the first fully varve-based chronology for the deposits of the deep-water Lake Shira (Chulym-Yenisei Basin, South Siberia), derived from a new sediment core. The very well-preserved varves show typical properties of the clastic-biogenic and endogenic types that can be subdivided into four sublayers representing winter–early spring, late spring, early summer and late summer–autumn. The analysed sediment section of 147 cm length comprises 2491 varve years with a total counting error of 1.6 % (i.e. ±40 years), making the new sediment core from Lake Shira a unique high-resolution archive for multi-proxy studies of past climate/environmental change and human-environment interactions. Direct comparison of nine AMS radiocarbon (14C) dates based on sediment bulk organic fractions with an age-depth model based on varve counting made it possible to examine the 14C reservoir effect in the lake. The reservoir effect is a common issue when estimating the age of environmental proxies from lacustrine sedimentary archives in Inner Asia. Although a constant reservoir effect is commonly used to correct the 14C dates from a single core or lake basin, our results from Lake Shira demonstrate that it varies significantly over the last 2500 years, ranging from 240 ± 30 to 1045 ± 30 years. The spatiotemporal variability of the reservoir effect can considerably reduce the accuracy of age-depth models based solely on the bulk organic sediment fraction. Where varved sediment is unavailable, as is usually the case, lignin phenols, terrestrial plant remains and purified pollen concentrates should be considered as alternative dating materials.

Korolev, Yury P., Korolev, Pavel Yu.

The aim of the study was to confirm the possibility of forecasting tsunamis of non-seismic (volcanic) origin using the express method of operational forecasting. The surface wave formed as a result of the explosive volcanic eruption on January 15, 2022 was a superposition of forced (baric) waves caused by an atmospheric pressure wave and free (gravity) waves generated by the disintergration of the disturbance in the source. The express method of operational tsunami forecasting was used to compute the gravitational component of the surface wave. The method allows one to compute the tsunami waveform at any point in the ocean and near the coast in real time based on the data from the sea level measurement stations. The computation of the tsunami on 15.01.2022, its gravitational component, at the DART stations remote from the source was performed based on the data from the DART stations 51425 and 52406 closest to the volcano. For an adequate forecast, the information on the tsunami of the DART stations closest to the source with the duration of a quarter of the first period is sufficient, which is especially important in the operational mode. The result satisfies the definition of the concept of "tsunami forecast" formulated by the Intergovernmental Oceanographic Commission of UNESCO. It has been confirmed that the express method can provide a tsunami forecast regardless of the mechanism of its excitation. It remains unclear how adequate the assessment of the amplitude of surface waves is based on the bottom pressure data is.

Janos Moga, Katalin Fehér, Daniela Strat

In this paper, we present the results of the geomorphological study of the micro pseudokarst landfoms developed on Pâclele Mari mud volcanic site that belongs to the famous mud volcanic area Berca-Arbănași, Buzău Subcarpathians, Romania. Different types of pseudokarstic cavity formation can be observed in the area, especially in the sloping periphery of the mud volcanic area, where badlands developed (badland pseudokarst), and rheogene pseudokarst in the mud flows. The liquid mud material gets denser and wimple on the surface of the mud that flows in the trough, it compiles and then covers the liquid mud channel. These micro-size covered tunnels are similarly formed as lava tubes at the lava flows of real volcanic areas. In order to complement the field measurements, we carried out surveys with a DJI Phantom 3 and 4, and Mavic Pro quadcopter to determine the landforms for the photogrammetry. Granular composition tests were carried out on sediment samples collected in the mud volcanic area by a laser diffraction particle analyser.

Toshiaki Tsunogae, Cheng-Xue Yang, M. Santosh

Charnockites (orthopyroxene-bearing granitoids) constitute one of the major components in many Precambrian high-grade metamorphic terranes of the world. They are broadly classified into two types based on the nature of occurrence as massive charnockite that forms large (magmatic) batholiths, and incipient charnockite which occurs as patches, veins and lenses of mesoscopic scale developed through local dehydration reactions within felsic (both igneous and sedimentary) protoliths. Here we present petrological data on representative charnockites of different ages and tectonic settings from various parts of the world and evaluate their formation conditions based on phase equilibrium modeling in the system NCKFMASHTO. Massive charnockites ranging from Neoarchean to Paleoproterozoic age from the Salem and Nagercoil Blocks (southern India), Napier Complex (Antarctica), and the Limpopo Complex (Zimbabwe) record P-T conditions that are broadly equivalent to the regional P-T conditions of high-grade metamorphism recorded in these terranes, ranging from normal granultes to ultrahigh-temperature metamorphic rocks. Typical unmetamorphosed magmatic charnockite in a late Paleoproterozoic post-collisional extensional setting and carrying K-feldspar phenocrysts from the North China Craton yield a wide P-T stability range. Incipient charnockite from southern India records P-T conditions that are slightly lower than the peak P-T regimes estimated for the region. Regardless of the discrepancies in P-T conditions estimated from the phase equilibria approach, the data confirm that these rocks, in all the cases considered in this study, were generated under low aH2O conditions. The available fluid inclusion data from both massive and incipient charnockites confirm that the water activity was buffered to low levels, possibly through the presence of CO2-rich fluids, to stabilize the index mineral orthopyroxene in these rocks. Charnockites formed in different plate tectonic settings; in most cases as arc magmas within subduction-collision settings and some cases, post-collisional extension during different periods in Earth history, and serve as potential archives of melt and fluid processes in the continental crust.

Liu Linsong, Shi Songlin, Sun Junmin et al.

Based on the analysis of tectonic background and coal-accumulating environment of Jungar coalfield, the coal petrological characteristics, inorganic mineral composition, distribution and occurrence regularity of coal and gangue in No.6 coal of the Junger coalfield are studied, and the genesis is determined byutilizing the research methods of coal petrology, mineralogy and geochemistry.The study shows that the average contents of the inertinite, vitrinite and exinite in the maceral of No.6 coal in the study area are 59 %, 28 % and 13 %, respectively.Compared with the Late Paleozoic coals in other areas of North China, the content of the inertinite is high, which reflects an adequate supply of surface water during the formation of No.6 coal seam.The main inorganic minerals in coal and gangue are kaolinite and boehmite, associated with quartz, calcite, siderite, pyrite, anhydrite, anatase and svanbergite.The vertical changes of the mineral composition and main chemical elements of No.6 coal indicate that the middle of the coal seam is rich in boehmite, while the upper and lower parts are rich in kaolinite.There are three origins of kaolinite: colloidal precipitation crystallization, terrestrial transport sedimentation and volcanic ash alteration.And there are two origins of boehmite: alumina colloidal precipitation crystallization and desilication alteration of kaolinite.

CHEN Qianqian

The gas test breakthrough of mudstone shale of Taiyuan Formation in Well-MY1 and Well-ZDY2 has proved that the Upper Paleozoic marine-continental transitional shale gas in the South of North China Basin has potential for further tapping resources. Based on the latest data of Well-TX3 and Well-TX4, this paper comprehensively analyzes the shale geochemistry, petrology, reservoir space, physical properties and gas bearing properties of the Taiyuan Formation and Shanxi Formation of the Upper Paleozoic in Tongxu area in the South of North China Basin, the results show that: ① The organic matter of the mud shales of the Taiyuan and Shanxi Formations comes from the vascular plant and belongs to type Ⅲ Kerogen; <i>TOC</i> value is 1.0 %~4.5 % and belongs to good source rock; <i>R</i>_o value is 2.4 %~3.4 % and is in the over mature stage. The mud shale reservoir has higher brittle mineral content, which is favorable for the later fracturing reconstruction. ②The reservoir space is dominated by fractures and micro-fractures, followed by inorganic pores, less developed organic pores and isolated distribution. ③Based on the comparison of the gas test results and shale gas evaluation parameters, the shale gas resource potential of Taiyuan Formation is obviously better than that of Shanxi Formation.

Xiangdong Yin, Shu Jiang, Peng Wu et al.

The pH value of plaeofluid exerts great influence on the formation of the secondary pores of sandstones.In the paper, the control of the acid and alkaline diagenetic fluid environment on the reservoir quality was analyzed in the Upper Paleozoic tight sandstones in the Ordos basin.Based on the plenty of survey of casting thin section, scanning electron microscope, X-ray diffraction, routine testing of physical properties, and high pressure mercury injection, the characteristics of petrology and mineralogy, physical properties, diagenesis, genetic types of pores, and pore-throat structure within the Upper Paleozoic tight sandstones were detailedly investigated in the Linxing and Shenfu district, eastern Ordos Basin.The identification, zonage, and distribution of the acid and alkaline diagenetic environment within tight sandstones as well as the evolution of diagenetic fluid environment and its reponse of the physical properties were investigated.Results showed that the upper strata underwent a diagenetic fluid evolution of alkaline-acid-alkaline mode during the burial process, whereas the lower strata experienced a mode of acid-alkaline.Acid diagenetic environment was characterized by feldspar dissolution, quartz overgrowth, and deposition of authigenic kaolinite, in which feldspar dissolution pores, intercrystalline pores of clay minerals developed with relatively large pore radius and better reservoir quality.Alkaline diagenetic environment was featured by quartz dissolution and deposition of authigenic chlorite, in which quartz dissolution pores and intercrystalline pores of clay minerals developed with relatively small pore radius and poor reservoir quality.The case of transitional zone of acid and alkaline zone(TZAA) falls in between acid zone(AZ) and alkaline zone(AlZ).Nevertheless, the physical properties are best in the AZ, followed by TZAA.The distribution of the AZ, AIZ and TAZZ and their responds to the physical properties are significant to the reservoir evaluation.

akbar ahmadvand, Mohsen Nasrabady, Abbas Asiabanha et al.

The Seghin metamorphic complex of ophiolitic mélange from the north Soghan, composed of metamorphic suites varying in protolith and metamorphic grade. The rock units of this complex have been metamorphosed under PT conditions of pumpellyite- actinolite, greenschist- Ep amphibolite and blueschist facies enclosed by a serpentinitic mélange. The pumpellyite- actinolite and greenschist- Ep amphibolite facies rocks display overprinted metamorphic evidences of blueschist facies as glaucophane overgrowth around actinolite and magnesiohornblende crystals. The average temperature and pressure calculated by thermocalc software and petrogenetic grids is 6- 7, 290- 350 and 11 Kb, 350 ˚C for pumpellyite- actinolite schist and blueschist samples, respectively. The relations of minerals transformation, thermobarometry calculations and the lawsonite preservation are in accordance with counter- clockwise metamorphic path. Generally, the metamorphic blocks of serpentinitic mélange with counter- clockwise PT path like Seghin complex are characteristics of long- lived subduction systems. During the onset of subduction event and attaining to blueschis facies, metamorphic path of down- going slab has passed through greenschist- Ep amphibolite facies. Then, the prograde metamorphic path extending across Pmp- Act subfacies owing to decreasing of geothermal gradient during maturity of subduction setting. Consequently, hairpin- like PT path is governed that is characteristic of Franciscan- type accretionary prisms.

aghail madadi, ebrahim beheshti javid, nazfar aghazadeh

During the last years, following an increase in damages due to occurrence of landslides, human has decided to reduce such losses. Therefore, identifying regions susceptible to landslide and classifying them can partly help man to prevent from happening above phenomena. The current study aims to demonstrate factors contributing to occurrence of landslide in Candrigh Chay basin and then, flattening the basin regarding risks related to landslide event using one methods, Network Analysis Process. In this direction, as respects to basin morphology and also, findings of past researches , ten factors involved in occurring landslides in Candrigh Chay Basin were recognized and used : lithology , land use , rainfall , slope , slope aspect , road slide , sluice power index (SPI), sediment transfer index (STI).Network Analysis Process(ANP) Method was implemented to score and classify factors and  scales. Was carried out in order to measure classes of each parameter. The final map showed that the basin has 4 classes considering landslide. Findings reveal flats with low risk and flats with high risk have the least area in Candrigh Chay basin. On the other hand, flats with medium risk and high risk allocate the most area of basin for themself. Comparing slid surfaces with flats facing risks indicates regions located at high and average risk class possess most areas of slide surfaces so that a flat involving very high risk  and a flat with high risk devote 35 percent (79km²) and 32/6 (72km²) of landslides for themselves, respectively. In other words, more than 77 percent of landslides conform to flats covering very high and average risk. Moreover, petrology, slope, and, sluice slide were identified as the most effective agents in occurring land_slides. One models, Network Analysis Process (ANP) were utilized through this project

Yongliang Gao, Zhigang Wen, Yaohui Xu et al.

Abstract In order to study the geochemical characteristics of fine-grained sedimentary rocks and clarify its relationship with the tight oil reservoir, the Chang7 Member of Triassic Yanchang Formation in Longdong area was taken as an example to be studied by rock pyrolysis, isotopic determination, maceral analysis, gas chromatography and gas chromatography–mass spectrometry. Lacustrine organic-rich fine-grained sedimentary rocks can be divided into organic-rich shale and organic-rich mudstone according to their lithology and texture. The results show that the organic-rich shale was deposited in a quiet and anoxic deep lacustrine environment, the organic matter was of high abundance and mainly sourced from plankton and benthic algae (type I–II1). Organic-rich mudstone mainly deposited in the semi-deep lacustrine environment, where the water was relatively shallow and the salinity was low, the organic matter was of low abundance and came from the mixed source of plankton and terrestrial clastic (type II1–II2). The Chang7 tight oil is widely distributed in the turbidite sand bodies, and it was mainly sourced from the Chang7 organic-rich shale.

Mahsan Basafa, Kelly Hawboldt

Abstract Reservoir souring is a widespread phenomenon in reservoirs undergoing seawater injection. Sulfate in the injected seawater promotes the growth of sulfate-reducing bacteria (SRB) and archaea-generating hydrogen sulfide. However, as the reservoir fluid flows from injection well to topside facilities, reactions involving formation of different sulfur species with intermediate valence states such as elemental sulfur, sulfite, polysulfide ions, and polythionates can occur. A predictive reactive model was developed in this study to investigate the chemical reactivity of sulfur species and their partitioning behavior as a function of temperature, pressure, and pH in a seawater-flooded reservoir. The presence of sulfur species with different oxidation states impacts the amount and partitioning behavior of H2S and, therefore, the extent of reservoir souring. The injected sulfate is reduced to H2S microbially close to the injection well. The generated H2S partitions between phases depending on temperature, pressure, and pH. Without considering chemical reactivity and sulfur speciation, the gas phase under test separator conditions on the surface contains 1080 ppm H2S which is in equilibrium with the oil phase containing 295.7 ppm H2S and water phase with H2S content of 8.8 ppm. These values are higher than those obtained based on reactivity analysis, where sulfur speciation and chemical reactions are included. Under these conditions, the H2S content of the gas, oil, and aqueous phases are 487 ppm, 134 ppm, and 4 ppm, respectively.

Mariano Elías-Herrera, Fernando Ortega-Gutiérrez

The Guerrero terrane in southern Mexico (Figure 1) is considered a major tectonostratigraphic accretion to the Mesozoic continental crust of Mexico, and essentially lack­ing an old continental basement (Campa and Coney, 1993; Centeno-García et al.,1993)… in order to continue, download the full paper in PDF.

Yuvarajan Devarajan, Dineshbabu Munuswamy, Beemkumar Nagappan et al.

Abstract This work examines the effect of butanol as an oxygenated additive to lower carbon monoxide, smoke, nitrogen oxide and hydrocarbon emissions and to improve the performance aspects of Calophyllum inophyllum (Punnai) biodiesel. Single-cylinder, oil-cooled compression ignition engines are employed in this work. Neat Punnai biodiesel (P100) is blended with butanol at 10% and 20% by volume and labelled as B10P90 and B20P80, respectively. Methanol and alkaline catalyst (KOH) were used for the transesterification process for biodiesel production. The transesterification technique yielded 88% biodiesel from raw Punnai oil. Engine tests resulted in lower CO, smoke, NOx and HC emissions when fuelled with both butanol blends when compared to P100. In addition, BSFC (brake-specific fuel consumption) reduced and BTE (brake thermal efficiency) increased with the inclusion of butanol blends (B10 and B20) to neat Punnai biodiesel.

Majid Alipour, Bahram Alizadeh, Ali Chehrazi et al.

Abstract Biodegradation modeling is combined with petroleum system modeling along a regional 2D transect from the southern Persian Gulf basin. An advanced basement model was considered in the model that allowed a constant temperature to enter the entire sedimentary column. Modeling results were calibrated against existing temperature and vitrinite reflectance data from nearby wells. Temperature, burial, and charge histories are carefully monitored within the studied section through geological time. Based on our modeling results, biodegradation has been effective along the migration pathway and within the eventual accumulation sites to varying extents. These findings can have practical implications for pre-drill oil quality predictions and accurate geochemical evaluations of oils and reduce offshore oil and gas exploration risks.

Harinandan Kumar, M. K. Mishra, S. Mishra

Abstract The study of gas sorption characteristics is important for practical assessment of coal bed methane (CBM) production and CO2 sequestration in coal seam. Adsorption isotherm is one of the critical parameters for the establishment of production as well as injection well. Adsorption isotherm provides information about the reservoir conditions and critical desorption pressure as well as volume of gas that can be sequestered in deep coal seam. Alteration in sorption isotherm reflects the increase or decrease of the gas production as well as CO2 sequestration. Therefore, in this paper, experimental investigation was carried out to determine the CO2/CH4 sorption capacity of five different coal samples taken from different locations of Jharia coalfield (Moonidih area) of Gondwana basin. Gas sorption capacity was determined at 27 °C temperature and up to 7.5 MPa pressure. CO2 adsorption was observed to be higher than that of the CH4. The sorption ratio of CO2/CH4 varied from 1.6:1 to 1.2:1 for all coal samples. Furthermore, the experimental results were correlated using established Langmuir, Freundlich, Temkin and D–R isotherm models. Experimentally obtained values satisfactorily fitted to the Langmuir and Freundlich model with comparable accuracy. The excess adsorption capacity of coal was also compared with different rank parameters to understand the variation of sorption capacity with rank of coal.

C. G. Okeugo, K. M. Onuoha, C. A. Ekwe et al.

Abstract Lithofacies distributions and continuity are very important for proper reservoir development; and predicting the fluid types will also help in reducing uncertainties associated with characterizing hydrocarbon reservoirs. This study used Poisson impedance attributes and crossplots from prestack seismic inversion and well logs to discriminate and predict hydrocarbon-filled reservoirs in the Bumma Field, Greater Ughelli Depobelt, Niger Delta Basin. Seismic inversion and well log data were integrated to image and characterize lithofacies at reservoir zones of interest. A supervised model-based simultaneous inversion of Poisson impedance (PI) and crossplot was carried out on the prestack seismic data to understand the lithofacies classification and fluid types. Four classifications of lithofacies (clean sand, sandyshale, shaly-sand and shale) were discriminated based on the well log crossplot between gamma ray and Poisson impedance. The sand lithofacies shows low values of gamma ray (< 65 API) and PI (<− 100 ft/s*g/cc) while shale lithofacies possesses high values of gamma ray (> 65 API) and PI (>− 100 ft/s*g/cc). Also, well log and inverted results from PI showed that values with less than − 100 ft/s*g/cc represent hydrocarbon-filled sand, whereas greater values represent brine and shale. These classifications provide better decision in predicting and discriminating lithofacies accurately. Furthermore, generated map revealed the presence of hydrocarbon-filled reservoirs in a northeast–southwest trending meandering channel. The successful application of crossplot and seismic-based impedance inversion will be helpful in discriminating lithofacies and predicts fluids for accurate location of new wells for optimum production from the field.

Gregor Kovačič

Kraški izviri predstavljajo pomemben vir pitne vode tako v Sloveniji kot v svetu. Zaradi specifične zgradbe so kraški vodonosniki v večini zelo občutljivi na onesnaženje. Avtor na primeru kraškega izvira Bistrica izpostavi problematiko varovanja kraške podtalnice ter predstavi glavne pomanjkljivosti ter slabosti sedanje zakonodaje in uveljavljene prakse na področju varovanja kraških vodonosnikov v Sloveniji. Kljub relativno ugodnim razmeram za varovanje (redka poseljenost, manj intenzivno kmetijstvo,…) v primerjavi s kraškimi območji drugod po svetu je veliko pomembnih kraških izvirov slabo zavarovanih. Vodovarstveni režimi so največkrat slabo definirani, nadzor nad izvajanjem zaščitnih ukrepov pa neučinkovit. Karst springs are important drinking water sources both in Slovenia and elsewhere in the world. Due to their specific structure, karst aquifers are in most cases highly vulnerable to pollution. Through the example of the Bistrica karst spring, the author highlights the problems of karst groundwater protection and presents the main shortcomings and weaknesses of the relevant legislation in force and of established practices in the field of the protection of karst aquifers in Slovenia. Despite relatively favourable conditions for water protection (scarce population, less intensive agricultural activities etc.) as compared with karst areas elsewhere in the world, many important karst springs in Slovenia are improperly protected. Water protection regimes are often established inappropriately and control over the implementation of protective measures is inefficient.

D. Green

W. Melson, G. Thompson