Hasil untuk "Petrology"

Tan Zhang, Chao Ma, Yifan Li et al.

Abstract The current low-resolution chronostratigraphic framework for the early Ediacaran Period hampers a comprehensive understanding of potential trigger mechanisms for environmental upheavals and their connections to evolutionary innovation. Here, we establish a high-resolution astrochronological framework spanning ~57.6 million years of the early Ediacaran, anchored by the radioisotopic date of the Gaskiers glaciation onset, based on key sections from South China. Constrained by multiple radioisotopic dates, this framework precisely constrains the timing of the Marinoan deglaciation, Ediacaran Negative carbon isotope excursions 1 and 2 (EN1 and EN2), and key fossil assemblages (acanthomorphic acritarchs, Weng’an and Lantian biotas). These dates indicate the rapid termination of the Marinoan glaciation in South China within 106-107 years, while providing robust temporal evidence for the global synchroneity of EN1, EN2, and Marinoan deglaciation. The integrated chronology refines the age model for early Ediacaran biotic evolution, revealing that ecosystems gradually increased in complexity over multi-million-year timescales while global taxonomic diversity remained relatively stable, punctuated by rapid transitions to novel communities coinciding with biogeochemical perturbations.

Zahid Ullah Khan, Zulfiqar Ahmed, Muhammad Tayyab Naseer et al.

Abstract Kadanwari is a major gas-producing field in Pakistan's Lower Indus Basin (LIB), extensively explored for optimized production. However, the reservoir sands of the Lower Goru Formation (LGF), deposited in a complex river-dominated delta, bear severe variability and hinder accurate facies approximation for optimal production. Furthermore, the regionally extended NNW-SSE directed horst and graben structures significantly compartmentalized these reservoir facies. The main E-sand interval is analyzed for its geological properties, depositional environment, and distribution. The integration of various approaches, including seismic interpretation, attribute extraction, well-based facies modeling, and petrophysical evaluation, proved significant in evaluating the heterogeneous and tectonically influenced E-sands. The discontinuity attribute substantially highlighted the structural style and aided in analyzing the geometries of faults. The low values of the frequency attribute (< 10 Hz) signified the entrapped gas-bearing sands along the faulted zones. The high responses of instantaneous amplitude and sweetness profoundly illuminated the gas-significant deposits throughout the field in association with the well-identified gas-prone sand facies. The outcomes of the neutron-density crossplot depicted gas-bearing sands having low density (< 2.3 g/cc) and good porosity (12%) with the assessment of various cements. The facies modeling distinguished between clean and intermixed sand-shale reservoir zones. Petrophysical analysis revealed a net pay of 14 m within E-sand having gas saturation of about 68%. The adopted approach is robust and efficient, employing a limited data set for developing well-associated seismic responses for potential zone delineation within structural arrangements. The techniques can be optimistic about the LGF's complex potential sands demarcation throughout the Indus Basin.

Zhiliang He, Jianyun Feng, Jun Luo et al.

The part of China, east of the Hu Huanyong Line, is commonly referred to as eastern China. It is characterized by a high population density and a well-developed economy; it also has huge energy demands. This study assesses and promotes the large-scale development of geothermal resources in eastern China by analyzing deep geological structures, geothermal regimes, and typical geothermal systems. These analyses are based on data collected from geotectology, deep geophysics, geothermics, structural geology, and petrology. Determining the distribution patterns of intermediate-to-deep geothermal resources in the region helps develop prospects for their exploitation and utilization. Eastern China hosts superimposed layers of rocks from three major, global tectonic domains— namely Paleo-Asian, Circum-Pacific, and Tethyan rocks. The structure of its crust and mantle exhibits a special flyover pattern, with basins and mountains as well as well-spaced uplifts and depressions alternatively on top. The lithosphere in Northeast China and North China is characterized by a thin, low density crust and mantle, whereas the lithosphere in South China has a thin, low density crust and a thick, high density mantle. The middle and upper crust contain geobodies with high conductivity and low velocity, with varying degrees of development that create favorable conditions for the formation and enrichment of geothermal resources. Moderate-to-high temperature geothermal resources are distributed in the Mesozoic–Cenozoic basins in eastern China, although moderate temperature geothermal resources with low abundance dominate. Porous sandstone reservoirs, karstified fractured-vuggy carbonate reservoirs, and fissured granite reservoirs are the main types of geothermal reservoirs in this region. Under the currently available technical conditions, the exploitation and utilization of geothermal resources in eastern China favor direct utilization over large-scale geothermal power generation. In Northeast China and North China, geothermal resources could be applied for large-scale geothermal heating purposes; geothermal heating could be applied during winter along parts of the Yangtze River while geothermal cooling would be more suitable for summer there; geothermal cooling could also be applied to much of South China. Geothermal resources can also be applied to high value-added industries, to aid agricultural practices, and for tourism.

Hassan Gohari, Mohammad Hassan Karimpour, Hooshang Asadi Haroni et al.

Granites are the most important components of the continental crusts. As an important part of the Alpine-Himalayan global belt and the result of the Tethys evolutionary cycle, the Urmia-Dokhtar Magmatic Arc (UDMA) has formed during different magmatic periods. The most important magmatic episode of UDMA igneous rocks, which is the result of lithospheric extenssion and extensive magmatism, occurred during 55 to 37 Ma (Moghadam et al., 2015). In order to enhance our understanding of tectonomagmic evolution of the continental crust during this period, in this research, the intrusive masses of Aftabru and Qlichkandi will be investigated using geochemical data and the isotopic composition of neodymium and strontium. The mentioned intrusive masses are located in the southwest region of Buin Zahra in Central Iran zone.Geology BackgroundUrmia-Dokhtar magmatic arc with Cenozoic intrusive and Eocene-Quaternary extrusive rocks shows different levels and rock outcrops in terms of time of origin and erosion rate, same what is seen in the subduction arc of the Andean continental margin. The lithospheric stresses caused by the interaction of the African-Eurasian-Indian lithosphere led to the emergence of Paleogene extensive magmatic activity and a magmatic flare-up lasting 30 Myrs during Eocene and Oligocene. As a result, more than 4 km of Paleogene igneous rocks formed in Saveh, Zarandiyeh, and Tafresh regions. In the south of Bouin Zahra region, pyroclastic outcrops and Eocene lava with a width of about 5km2 and 10 km2 are found in Aftabru and Qlichkandi areas, respectively.MethodsAfter field observations and detailed textural and petrographic studies, 12 suitable samples with minimal weathering and alteration were selected from intrusive rocks and analyzed by XRF and ICP-MS methods for major, trace and rare earth elements. 6 whole rock samples were analyzed for Sr-Nd isotopes.PetrographyIn Aftabru and Qlichkandi areas, quartz monzonites intruded the lower-middle Eocene volcanic and pyroclastic rocks.AftabruPetrological observations show that the Aftabru intrusion contains 7-16 Vol% quartz, 25-30 Vol% K-feldspar, 39-54 Vol% plagioclase, 5-10 Vol% pyroxene, 8-15 Vol% amphibole, as well as 1 Vol% accessory minerals.QlichkandiThe medium-grained Qlichkandi intrusive rocks with granular texture, composed of quartz 9-15 Vol% quartz, 25-28 Vol% K-feldspar, 35-45 Vol% plagioclase, 1-5 Vol% pyroxene, 5-10 Vol% of the common mafic mineral of amphibole, 5 Vol% biotite, and less than 1 Vol% accessory minerals.DiscussionBased on new geochemical and isotopic data, we will investigate the tectonic location, genesis and magmatic processes affecting the parental magma and the possible source rock of the intrusive masses in the south of Bouin Zahra region.Tectonic-magmatic zone:As  the pattern of rare earth elements and the spider diagrams of enrichment in LILE and LREE elements and depletion of HFSE and HREE elements display, the most important characteristic of intrusive rocks in the studied area is their similarity to continental margin arc rocks.   Generation and magmatic processes:Some incompatible trace elements ratios, such as Y/Nb, Nb/Ta and Nb/La that are less affected by diffrentiation are good indicators for investigation of the magma origin and the crustal contamination effect on the magma. The higher amounts of Y belong to crustal melts or impregnation with crustal materials, and the higher amounts of Nb belong to melts derived from the mantle. In the studied intrusive rocks, Y/Nb ratio is 1.6 on average with a range of 0.6-3.6, which probably indicates mantle with crustal mixing in the magama origin. The Nb/La value is 0.1 in primary mantle and 0.46 in the crustal rocks (Morata et al., 2005), it is about 0.86 on average and equals to the range of 0.1-0.52 in the intrusive rocks of the southern region of Buin Zahra (Qlichkandi, Aftabru). This value indicates a mantle origin for the studied rocks. The Nb/Ta value in mantle rocks is 17.5 and in crustal rocks it is equal to 11-12 (Green, 1995). This ratio is 15 on average (ranging from 8 to 8. 26), supporting the mantle origin as well.Neodymium model age (460-550 Ma) and positive ԑNd(t) indicate the Cadomian origin of lithospheric rocks of the Aftbaru region, while the model age of the samples from Qlichkandi region is 0.9. It shows ԑNd(t) less than zero. This difference is probably due to the high magma mixing with crustal materials in Qlichkandi region, which is confirmed by the diagram of ԑNd versus Sr isotope. 143Nd/144Nd ratio for the Aftabru samples is 0.51270-0.51280. But in the Qlichkandi samples, it is 0.51252-0.51242, which is a sign of contamination with the lower continental crust materials and a tendency towards lower crust. 87Sr/86Sr ratio is 0.70472-0.70510 in Aftabru and 0.70631-0.70607 in Qlichkandi samples. Therefore, according to the intrusive rock petrologic diagrams, it shows signs of contamination with the underlying crustal materials.AcknowledgementsThe authors would like to express their utmost gratitude for the research grant number 41200/3 from Ferdowsi University of Mashhad, and we are also grateful to all dear referees who did not spare their kindness in increasing the scientific richness and literature of this article.

Dongjun FENG

Productive breakthroughs have been achieved for the exploration and development of marine shale gas in the Sichuan Basin, and 6 shale gas fields have been built including Fuling, Weiyuan, Changning, Zhaotong, Weirong and Yongchuan. Continental shale gas is an important exploration replacement layer series with great potential. By the approaches of whole rock X-ray diffraction, TOC content, carbon isotope of kerogen, organic petrology, combined determination of high-pressure mercury injection and nitrogen adsorption, argon ion polishing and scanning electron microscope, and physical property test, the formation conditions of shale gas in the Jurassic Daanzhai Member of the Sichuan Basin were discussed, and the main controlling factors of shale gas enrichment were proposed. Results show that continental shale in the Jurassic Daanzhai Member in the Sichuan Basin is featured by rapid lithofacies changes, strong heterogeneity, frequent interbedding of shale, sandstones and limestones, low organic matter abundance, TOC ranging from 0.04% to 3.89% with type Ⅱ2 and Ⅲ of organic matters, low degree of thermal evolution with Ro values ranging from 1.10% to 1.83%, producing both condensate oil and wet gas. Continental shale has high porosity, ranging from 0.95% to 8.42%, There are mainly inorganic mineral pores dominated by micropores and mesopores. The average gas content of field test is 0.96 m3/t. It is clear that semi-deep lacustrine facies, favorable lithofacies assemblage, fractures and preservation conditions are the main controlling factors of continental shale gas enrichment. Based on the analysis of main controlling factors, highlighting the quality and thermal evolution degree of continental shale, combined with preservation conditions and engineering technical conditions, an evaluation criterion of favorable areas for continental shale gas in the Daanzhai Member in the Sichuan Basin was established. Combined with GIS integrated spatial superposition technology, several favorable zones were proposed, including the southwest of Yuanba, the southeast of Langzhong, Yilong, the northwest of Fuling and the northwest of Jiannan areas.

Kerstin Elert, Manuel Pérez Mendoza, Carolina Cardell

Photo-induced darkening of red cinnabar (α-HgS) often dramatically changes the appearance of artworks, but the reduction mechanism of Hg2+ remains unclear. Here, the authors propose an alternative pathway for the blackening reaction of cinnabar, considering its semiconductor properties and pigment-binder interactions

Rachida Talbi, Ahlem Amri, Abdelhamid Boujemaa et al.

Abstract The Jebel Oust region (north-eastern Tunisia) recorded two levels of marine black shale in the Lower Cretaceous marly series. Geodynamic evolution, biostratigraphic and Rock–Eval analysies allow classifying those black shales as unconventional shale oil resource systems that were deposited during two oceanic anoxic events: the Middel Barremian Event "MBE" and the Early Aptian Event "OAE1a". Paleogeographic evolution highlights two transgressive–regressive cycles: the first one is Valanginian-Early Barremian, and the second is Late Barremian–Early Aptian. Each black shale deposit occurs at the end of the transgression that coincides with the highest sea level. During the Barreman–Aptian interval, sedimentation was controlled by extensional faults in a system of tilted fault blocks which were reactivated several times. Kerogen is of type I, II origin in black shales and of type III origin in marls. Tmax values indicate "oil window" stage. Average transformation ratio is around 67% and 82%, respectively, in the Lower Aptian and Middel Barremian source rock related to the relatively high thermal maturity degree due to the deep burial of the later. Estimated initial hydrocarbon generation potential is moderate to high. Oil saturation index records an "oil crossover" indicating expelled and migrated hydrocarbons from the organic-rich to the organic-poor facies. The petroleum system of the two mature source rocks with a high hydrocarbon generation potential enclose all elements characterizing a "shale oil hybrid system with a combination of juxtaposed organic-rich and organic-lean facies associated with open fractures".

R. Hargraves

J. M. Munyithya, C. N. Ehirim, T. Dagogo

Abstract Reservoir characterization plays a significant role in the exploration, development, and production of hydrocarbon reservoirs. The use of integrated approach in characterization improves on the accuracy, certainty, and robust interpretation of reflectivity data. The study aimed to integrate reflectivity and spectral attributes to adequately characterize hydrocarbon reservoirs in MUN onshore Niger delta field. Well log and rock physics analyses identified and delineated reservoirs, discriminated lithology, characterized fluid, and established relations between elastic and reservoir properties for field-wide interpretation of the reflectivity data. The wells were tied to the reflectivity data, and H4 seismic horizon was mapped. Subsequently, sweetness, reflectivity and spectral attributes were extracted along H4 horizon after inversion and spectral decomposition of the reflectivity data and independently interpreted. Channel-like structure with high-amplitudes, low-to-moderate acoustic impedance (I p), lambda–rho (λρ) and mu–rho (µρ) attribute values, and high-amplitude low-frequency spectral attributes (15–35 Hz), respectively, characteristics of hydrocarbon saturated channel sands were delineated. The channel reservoir sand is thick, porous with low volume of shale and low to moderate water saturation. Analysis of data further shows that reflectivity attributes provided a better description of fluid characteristics than the sweetness and spectral attributes, but are less sensitive to structure and exaggerated the shape and limits of the channel sands. However, the spectral attributes seem to be more robust than the reflectivity attributes in providing subtle structural and stratigraphic details of the reservoir as well as delineating by-passed hydrocarbons in the field.

M. Hartley, E. Bali, J. Maclennan et al.

The 2014–2015 Holuhraun eruption, on the Bárðarbunga volcanic system in central Iceland, was one of the best-monitored basaltic fissure eruptions that has ever occurred, and presents a unique opportunity to link petrological and geochemical data with geophysical observations during a major rifting episode. We present major and trace element analyses of melt inclusions and matrix glasses from a suite of ten samples collected over the course of the Holuhraun eruption. The diversity of trace element ratios such as La/Yb in Holuhraun melt inclusions reveals that the magma evolved via concurrent mixing and crystallization of diverse primary melts in the mid-crust. Using olivine–plagioclase–augite–melt (OPAM) barometry, we calculate that the Holuhraun carrier melt equilibrated at 2.1 ± 0.7 kbar (7.5 ± 2.5 km), which is in agreement with the depths of earthquakes (6 ± 1 km) between Bárðarbunga central volcano and the eruption site in the days preceding eruption onset. Using the same approach, melt inclusions equilibrated at pressures between 0.5 and 8.0 kbar, with the most probable pressure being 3.2 kbar. Diffusion chronometry reveals minimum residence timescales of 1–12 days for melt inclusion-bearing macrocrysts in the Holuhraun carrier melt. By combining timescales of diffusive dehydration of melt inclusions with the calculated pressure of H2O saturation for the Holuhraun magma, we calculate indicative magma ascent rates of 0.12–0.29 m s−1. Our petrological and geochemical data are consistent with lateral magma transport from Bárðarbunga volcano to the eruption site in a shallow- to mid-crustal dyke, as has been suggested on the basis of seismic and geodetic datasets. This result is a significant step forward in reconciling petrological and geophysical interpretations of magma transport during volcano-tectonic episodes, and provides a critical framework for the interpretation of premonitory seismic and geodetic data in volcanically active regions.

J. Stormer, J. Nicholls

M. O'hara, R. Mathews

A. Gourain, A. Gourain, H. Planquette et al.

<p>The aim of the GEOVIDE cruise (May–June 2014, R/V <i>Pourquoi Pas?</i>) was to provide a better understanding of trace metal biogeochemical cycles in the North Atlantic Ocean. As marine particles play a key role in the global biogeochemical cycle of trace elements in the ocean, we discuss the distribution of particulate iron (PFe), in relation to the distribution of particulate aluminium (PAl), manganese (PMn), and phosphorus (PP). Overall, 32 full vertical profiles were collected for trace metal analyses, representing more than 500 samples. This resolution provides a solid basis for assessing concentration distributions, elemental ratios, size fractionation, and adsorptive scavenging processes in key areas of the thermohaline overturning circulation. Total particulate iron concentrations ranged from as low as 9&thinsp;pmol&thinsp;L<span class="inline-formula">⁻¹</span> in surface waters of the Labrador Sea to 304&thinsp;nmol&thinsp;L<span class="inline-formula">⁻¹</span> near the Iberian margin, while median PFe concentrations of 1.15&thinsp;nmol&thinsp;L<span class="inline-formula">⁻¹</span> were measured over the sub-euphotic ocean interior.</p> <p>Within the Iberian Abyssal Plain, the ratio of PFe to PAl was identical to the continental crust molar ratio (0.21&thinsp;mol&thinsp;mol<span class="inline-formula">⁻¹</span>), indicating the important influence of crustal particles in the water column. Overall, the lithogenic component explained more than 87% of PFe variance along the section. Within the Irminger and Labrador basins, the formation of biogenic particles led to an increase in the <span class="inline-formula">PFe∕PAl</span> ratio (up to 0.64&thinsp;mol&thinsp;mol<span class="inline-formula">⁻¹</span>) compared to the continental crust ratio. Continental margins induce high concentrations of particulate trace elements within the surrounding water masses (up to 10&thinsp;nmol&thinsp;L<span class="inline-formula">⁻¹</span> of PFe). For example, horizontal advection of PFe was visible more than 250&thinsp;km away from the Iberian margin. Additionally, several benthic nepheloid layers were observed more than 200&thinsp;m above the seafloor along the transect, especially in the Icelandic, Irminger, and Labrador basins, suspending particles with high PFe content of up to 89&thinsp;nmol&thinsp;L<span class="inline-formula">⁻¹</span>.</p>

Umair Ishtiaq, Ali Samer Muhsan, Ain Syahirah Rozali et al.

Abstract The formation of mineral scale has been a major constraint in the oilfield operations as it leads to numerous flow assurance issues. Scale deposition in the formation and production tubing can restrict the flow of hydrocarbon and interferes with the running and operation of downhole equipment. Scale inhibition squeeze treatment is one of the most common form of scale prevention. Although current squeeze treatment is the optimal way to prevent scale from depositing, it is still lack in certain aspect such as adsorption ability and retention time within the rock formation. This paper presents promising advantages of engaging nanotechnology to enhance current scale inhibition treatment. Experimental studies were carried out to examine the potential benefits of using graphene oxide and carbon nanotubes to increase the adsorption of conventional scale inhibitor, ethylenediaminetetraacetic acid (EDTA) on rock formation in a process called nano-carbon enhanced squeeze treatment (NCEST). This process involves treating the rock surface in the near wellbore region with nanomaterials that allow better adsorption capacity of scale inhibitor. Analysis testing using various techniques including field-emission scanning electron microscopy, energy-dispersive X-ray and ultraviolet–visible spectrophotometer were conducted to study the adsorption, retention and bonding of the scale inhibitor with nanomaterials and rock. NCEST technique was observed to significantly increase the adsorption of EDTA on rock sample treated with nanomaterials with a maximum adsorption of 180 mg/g compared to 51 mg/g on rock sample without nanomaterials treatment. In terms of cost–benefit, it is estimated to have significant reduction in operating expenses (up to 50%) after implementing the NCEST technique compared to that of conventional squeeze treatment.

Tangestani Ebrahim, Vafaie Sefti Mohsen, Shadman Mohammad Mahdi et al.

Abstract Low-salinity water injection has been utilized as a promising method for oil recovery in recent years. Low-salinity water flooding changes the ion composition or brine salinity for improving oil recovery. Recently, the application of nanoparticles with low-salinity water flooding has shown remarkable results in enhanced oil recovery (EOR). Many studies have been performed on the effect of nanofluids on EOR mechanisms. Their results showed that nanofluids can improve oil recovery when used in low-salinity water flooding. In this work, the effects of injection of low-salinity water and low-salinity nanofluid (prepared by adding SiO2 nanoparticles to low-salinity water) on oil recovery were investigated. At first, the effects of ions were investigated with equal concentrations in low-salinity water flooding. The experimental results showed that the monovalent ions had better performance than the divalent ions because of them having more negative zeta potential and less ionic strength. Also, low-salinity water flooding recovered 6.1% original oil in place (OOIP) more than the high-salinity flooding. Contact angle measurements demonstrated that low-salinity water could reduce the contact angle between oil and water. Then in the second stage, experiments were continued by adding SiO2 nanoparticles to the K+ solution which had the highest oil recovery at the first stage. The experimental results illustrated that the addition of SiO2 nanoparticles up to 0.05 wt% increased oil recovery by about 4% OOIP more than the low-salinity water flooding.

H. Helgeson

B. O’Driscoll, Jill VanTongeren

Guo Qi, Meng Lixin

Abstract Aiming at the problem of a reservoir in the high water cut stage, and specifically an understanding of the distribution of the residual oil, the existing evaluation methods cannot effectively reflect the flow and distribution of the underground fluid. In this contribution, the seepage field is divided into six sections based on the evaluation of the seepage characteristics of the high water content in the reservoir. The seepage field evolution processes were studied respectively from the different well patterns and the reservoir heterogeneity, and a corresponding seepage field reconstruction method is proposed based on the flow field equilibrium. The results show that the seepage field partition can well reflect the characteristics of the different development stages of reservoir seepage. The seepage field evaluation and reconstruction method is applied to the Nm3-4-1 layer of Gang Dong oilfield, where the water content decreased by 3.8%, and the variation coefficient of the seepage field decreased by 0.33. The evaluation method is of great significance for the exploitation of the remaining oil in high water cut reservoirs.

K. Cashman, J. Blundy

Hossein Narooie, Azadeh Malekzadeh Shafaroudi, Mohammad Hassan Karimpour

The Zeber Kuh prospect area is located southwest of Bardaskan, South Khorasan province, in the northeastern Iran. Lithologically, the area includes Rizu and Soltanieh Formations metamorphosed carbonate rocks, which were intruded by syenogranitic and syenodioritic intrusions. Field observations and laboratory studies such as structural controls of orebody, metasomatic replacement and formation of low temperature H2O-bearing minerals, and the occurrence of magnetite and pyrite associated with chlorite, epidote, calcite, and quartz indicate that  the iron mineralization is low temperature skarn-type. The source of Fe mineralization is probably a younger intrusive rock at depth. Hydrothermal ore fluid was ascended within fault zone and/or contact between the intrusive rock and the  carbonate unit and generated orebody. Iron grade ranges from 54 to 65 wt.% and sulfur value is > 3 wt.%. Magnetite chemistry and Ti, V, Al, Mn, Ni, and Cr contents are similar to skarn deposit. Biotite syenodiorite host rock has hypidiomorphic granular texture and it consists of plagioclase, K-feldspar, biotite, and apatite minerals. Chemically, this intrusive rock is K-series alkaline type, which was generated in within plate zone. This magma is characterized by strong enrichment in LREE, LILE (Rb, Cs, Ba, and K), HFSE (Nb, Zr, and Ti), and P elements. The primary magma is produced by low degree partial melting of garnet lherzolite from asthenospheric to boundary of asthenospheric-lithospheric mantle.