Rocks In Order Research Articles

Magma plumbing and hybrid magma formation at an active back-arc basin volcano: North Su, eastern Manus basin

North Su is the central volcanic edifice of the SuSu Knolls hydrothermal district, located in an extensional transform zone of the eastern Manus back-arc basin. The submarine volcano hosts a vigorous hydrothermal system with black and white smokers, diffuse fluid discharge, and accumulation of native sulfur. Among its dacitic to andesitic lavas are remarkable hybrid rocks, containing highly magnesian olivine (Fo81–94) phenocrysts with thin orthopyroxene reaction rims in a dacitic matrix. We investigated these rocks in order to understand their formation, to constrain temperature and depth of magma storage, and to identify links between magmatic processes and hydrothermal activity. The compositions, zonations and reaction rims of phenocrysts suggest that the hybrid lavas formed by mixing when dacitic to rhyodacitic magma was invaded by Mg-rich andesite to basaltic andesite with boninite affinities. The resulting melts show strong enrichment of large ion lithophile elements, moderate enrichment of light rare earth elements and depletion of Nb, Ta and Ti relative to N-MORB, characterizing them as back-arc basin magmas. Compositional zonations at the outermost rims of olivine phenocrysts suggest a period of no more than a few days between the inferred mixing event and eruption. Mineral-melt thermometers indicate a temperature of ∼1010 °C for the hybrid magma. Mineral-melt barometers give a wide range of pressures with a mean of 19 ± 217 MPa, reflecting equilibration at shallow depths as well as limited barometer performance at low pressures. In addition, many clinopyroxene phenocrysts lack equilibrium between their strongly zoned rims and the host melt. The H2O (0.9–5.3 wt%) and CO2 (70–4730 ppm) contents of melt inclusions in clinopyroxene and plagioclase phenocrysts provide better constraints on the pressure range for pre-eruptive magma storage. The data suggest that dacite phenocryst crystallization and magma mixing occurred at 40–140 MPa pressure, about 1–5 km beneath the summit of North Su. The sulfur–H2O relationship in melt inclusions reflect a degassing trend that is consistent with formation of an aqueous-sulfurous magmatic fluid, inferred to produce highly acidic vent fluids at North Su (Seewald et al., 2015). The melt inclusion data also indicate significant fractionation between F, Cl and H2O after magma degassing, possibly reflecting formation of a high-salinity brine at depth and fluorine fixation in minerals formed in the subsurface. Our results suggest that the dynamic magmatic system, with magma mixing occurring shortly before ascent and eruption, causes rapid changes in composition and quantity of exsolved fluids. Due to the short distance to the seafloor, such fluid fluctuations are rapidly transferred to the hydrothermal systems. This may be the main cause for the observed temporal, spatial and compositional variations in hydrothermal activity at North Su, and possibly at other vent fields of the Manus basin.

Analyzing Infiltration Characteristics through Rainfall Infiltration Test and Numerical Analysis

본 연구에서는 강우침투특성을 규명하기 위해 모암의 성질이 다른 풍화토를 대상으로 침투모형시험과 수치해석을 실시하여 풍화토별 간극수압 변화와 강우강도에 따른 간급수압 변화양상을 분석하였 다. 침투모형시험 장치는 자체 제작한 1차원 침투모형시험장비를 이용하였으며, 수치해석은 침투모 형시험장비와 동일한 실내시험 조건 및 경계조건으로 모델링하여 분석하였다. 모형시험 및 수치해석 결과 동일한 강우강도를 적용한 결과 습윤전선이 컬럼하부에 도달하는 시간차는 유사하게 나타 났으며, 투수계수가 크면 침투능 또한 높게 나온다는 사실을 파악할 수 있었다, 또한 강우강도변화에 따라 습윤전선의 진행이 빠르게 진행됨을 파악할 수 있었다. 이러한 분석결과를 통해 지반의 투수계 수, 강우강도와 지속시간은 지반의 침투과정에 영향을 주는 주요 인자임을 확인할 수 있었다. 이러한 침투 메커니즘은 사면 안정해석에 적용되며, 지반의 액상화(지진)에 의한 위험도 평가에 응용될 수있다.This study conducted a rainfall infiltration test for weathered soils of different parent rocks in order to investigate infiltration characteristics. The changing pattern of pore water pressure was identified and compared with the numerical analysis results to analyze ground infiltration characteristics in relation to rainfall characteristics. The results of rainfall infiltration test and numerical analysis showed that the infiltration capacity became higher when the infiltration coefficient of weathered soil was large given that the same rainfall intensity was applied. Additionally, it was found that the movement of wetting front was fast in accordance with the changing rainfall intensity. The analysis results indicated that ground infiltration coefficient, rainfall intensity and duration were the major factors influencing ground infiltration process.

Controlling the process of explosive destruction of rocks in order to minimize dust formation and improve quality of rock mass

Based on the adapted model by G.N. Lyakhov, we established a pattern in the propagation of pressure waves during explosive destruction of rocks, which relates to acoustic rigidity of the gap filler between the charge and the wall of the well and its size. It was determined that an increase in the acoustic rigidity of the solution proposed to be uses as a gap filler between the charge and the well reduces the peak of pressure in the zone close to the charge. In addition, the amplitude width of the pressure wave increases. An increase in the magnitude of the gap through the use of charges with smaller diameters enhances the effect of reducing the volume of dust formation. We have established regularities in the propagation of pressure waves related to acoustic rigidity of the gap filler between the charge and the borehole wall, as well as its magnitude, for different types of rocks. Specifically, for basalt, diabase, gabbro, granite, and limestone. It was determined that solutions with larger acoustic rigidity would reduce the amount of dust formation and improve the homogeneity of fractional composition of rock mass. That is possible by reducing the amplitude of pressure waves at the media interface and by increasing the width of the amplitude in any rock. In particular, filling the gap with the aqueous solution of iron (III) sulfate could reduce the amplitude of pressure waves by 20 %. The research results are important as they make it possible to control the process of explosive destruction of rocks. Such a control can be executed by changing the acoustic rigidity of the gap filler between the charge and the well, and by changing its size. Adjusting these parameters would not worsen the explosion results, such as, for example, reducing the consumption of an explosive or decreasing a diameter of the charge. On the contrary, it will ensure a more uniform distribution of pressure waves in rock, thereby reducing not only the environmental load, but the cost of finished products as well.

Quantitative prediction model of present-day low-TOC carbonate source rocks: Example from the Middle–upper Ordovician in the Tarim Basin

Plenty of marine crude oil generated by the Middle–Upper Ordovician source rocks has been discovered in the Tabei Uplift, Tarim Basin. Previous studies on the extensively distributed low organic matter source rock total organic carbon ≤ 0.5%) imply that this contributes to oil accumulation. Thus, the identification of present-day low-total organic carbon source rocks that experience hydrocarbon expulsion and evaluation of their contribution is of considerable significance to analyze marine oil accumulation and to assess the resources in the Tarim Basin. Using the mass balance approach, we identify and verify present-day low-total organic carbon carbonate source rocks and present a quantitative model using well-logging data to predict the present-day low-total organic carbon carbonate source rocks in order to evaluate their contribution in the Tarim Basin. Hydrocarbon expulsion has occurred in the Yijianfang formation, which has present-day low-total organic carbon, between 6452 and 6487 m in the Yangwu 2 well. In the horizons depicting carbonates with hydrocarbon expulsion, the porosity is relatively high and the daily oil production is 0.19 m3 according to the perforation tests. The extracts have similar biomarker signatures to that of the crude oils in the Tabei Uplift. In this study, a quick and cost-effective quantitative model is developed using double lateral resistivity and uranium/thorium well-logging data. By applying the prediction model, the contribution of present-day low-total organic carbon carbonate source rocks in the Middle–Upper Ordovician formation of the Tarim Basin is primarily evaluated to be 363.38 × 109 bbl oil equivalent.

Formation age and geodynamic setting of the Neoproterozoic Shalong iron formation in the Central Tianshan, NW China: Constraints from zircon U–Pb dating, geochemistry, and Hf–Nd isotopes of the host rocks

The recently discovered Shalong iron deposit in the Central Tianshan with a reserve of 14 Mt of iron at 25–30 wt.% Fe shows the typical iron formation geological characteristics: The host rocks are mainly metamorphosed volcanic rocks including quartz hornblende schist, mica quartz schist, and plagioclase amphibolite; the iron orebodies are stratiform and bedded, indicative of strata‐controlled deposits; metallic minerals are dominated by magnetite with haematite and ilmenite in minor quantities, whereas gangue minerals are quartz, amphibole, chloritoid, and plagioclase; and ore textures are banded and laminated. Here, we present LA‐ICP‐MS zircon U–Pb ages, whole‐rock geochemistry, Sm–Nd isotope, and zircon Lu–Hf isotope analyses on the host rocks in order to constrain the timing and geodynamic setting of the deposit. The geochemical characteristics, Sm–Nd isotope, and zircon Lu–Hf isotope compositions of the host rocks indicate that their protoliths were likely basic and felsic volcanic rocks. The bimodal kind rock types, the juvenile Nd–Hf isotopic characters, and the within‐plate trace element geochemical features of the host rocks together indicate that these rocks formed in a rift‐like extensional setting. Zircon U–Pb dating of the host rock interlayer suggests that the Shalong iron formation was formed in the Neoproterozoic (ca. 760 Ma). Combined with geological characteristics, close association with meta‐volcanic rocks, absence of glacial deposits, and within‐plate geochemical and juvenile isotopic signatures of the host rocks, the Shalong iron deposit is interpreted to be an Algoma‐type Neoproterozoic iron formation. The formation of this deposit can be linked to rift‐like volcanic activities related to the breakup of the Rodinia supercontinent. Our results in conjunction with previous studies suggest that the Central Tianshan should be related to the breakup of Rodinia, as indicated by the Neoproterozoic rift‐related igneous events of the Central Tianshan.

Scratching the Stones of Rock and Roll: Love Lyrics in the Times of the Argentinian Dictatorship

Argentinian rock has been marked by the last two dictatorships (1966–1973 and 1976–1983) and the 1982 Falklands War against Britain. To enhance the discussion about youth’s collective image during these periods, this article examines the context and texts of national rock in order to identify the transformations of the representation of love by taking into account the changing phases of the genre. Totalitarian regimes and war are at odds with love since they constrain fundamental rights. Both dictatorships even legislated (against) love by imposing Catholic dogmas. Love rock songs were subversive: they treated taboo topics and questioned the decisions of the junta.

The Purpose of Kata: When, Why, and for Whom Kata Forms Have Occurred in Okinawa

Abstract The primary aim of this research is to prove that the Kata forms were created for the self-defense of a weaker person against a stronger one. The materials and methods used for this research include a study of literature, old Chinese drawings, practical experience with Monku Jutsu, acupressure point fighting, history, Kata forms, anatomy, and body kinetics, as well as Chinese and modern philosophy. The most significant result of this study is a new approach to understanding Kata forms, with the most important conclusion being that Kata forms are an art of selfdefense that do not require fingers like iron or a body as hard as a rock in order for this knowledge to be used in a real life situation.

Purification of flowback fluids after hydraulic fracturing of Polish gas shales by hybrid methods

ABSTRACTHydraulic fracturing is a process that is used for the stimulation of impermeable rocks in order to release the trapped natural gas. Flowback fluid contains many different chemical ingredients used in the fracturing process; it also holds compounds leached from the bedrock. The production of a large amount of toxic fluids leads to the necessity of purification for recycling to reduce environmental impact. In this paper, the results of studies on the purification of flowback fluids by the combination of various processes such as filtration, advanced oxidation, and ion exchange are presented. The technological scheme of the treatment is proposed.

Geochemical behavior during mineralization and alteration events in the Baiyinchang volcanic-hosted massive sulfide deposits, Gansu Province, China

The Zheyaoshan deposit is the largest within the Baiyinchang (BYC) volcanic-hosted massive sulfide (VHMS) district, located in the northern Qilian orogenic belt of North China. The deposit is hosted by quartz keratophyre tuffs, with wall-rock alteration mainly comprising chlorite, sericite, quartz, pyrite and epidote. Mineral assemblages within the altered host rocks can be divided into a sericite-quartz-dominant assemblage (sericite-silicified zone), a chlorite-dominant assemblage (chlorite-dominant zone) and a pyrite-dominant assemblage (mineralized zone) based on geochemical analysis and alteration characteristics. We have conducted detailed processing and critical analysis of the geochemical data of both the altered and least-altered host rocks in order to investigate the problem of closure in the geochemical dataset to eliminate the influence that each component has on the other in terms of mass change, and have applied the standardized method of the mass change calculation to analyze this data. The results show that: (1) the sericite-silicified zone formed along fissures due to the ingress of hydrothermal fluids, with MnO2, Na2O and CaO being mobilized into the hydrothermal fluids leached and MgO, Fe2O3, SiO2, K2O, BaO deposited. Additionally, Ag, Cu and chalcophile elements (Ag, As and Bi) were enriched while Pb, Zn and large ion lithophile elements (LILEs) (Cs, Sr, Eu, Be) were mobilized into hydrothermal fluids; (2) the physiochemical conditions and pH levels of the hydrothermal fluids changed during sericitization, with MgO, Fe2O3, BaO being further enriched and MnO, Na2O, CaO further depleted, leading to formation of chlorite and the initial precipitation of metallogenic the (Cu, Zn, Pb) and chalcophile elements (Ag, As, Bi); (3) the negative Eu anomaly was mainly due to its strong activity when Eu is mobilized into the hydrothermal fluids during since plagioclase break-down during the sericite-silicification process; (4) AI and CCPI values gradually increase towards the orebody. The chlorite-dominant assemblage and sericite-quartz-dominant assemblage on the periphery of the chlorite-dominant zone can all be used as vectors towards the volcanic massive sulfide orebody and for regional-scale mineral exploration. Either leached elements or enriched elements can be considered as significant indicator elements and as prospective indicators for geochemical exploration within the BYC district. The Eu anomaly may be especially useful as an indicator for distinguishing the least-altered rocks which has great significance for exploration on the regional scale.

Influence of Rock Chemical Composition in Microwave Heating and Decontamination of Drill Cuttings

Drill cuttings generated by oil and gas drilling process are incorporated into the drilling fluid to ensure an efficient drilling and solids removal. The drilling rigs have a separation system accountable for separating drill cuttings and drilling fluids. Microwave drying is a new technology of separation that has been studied as an alternative to the currently drill cuttings dryer used. The results obtained in preliminary studies showed that this microwave drying is sensitive to different oxides presents into the rock. Thus, this study aimed to describe the microwave heating kinetics of some rocks in order to verify the interaction of oxides with electromagnetic waves. For this, the oxide contents of the rocks were determined by X-ray Fluorescence and different rocks were heated in a microwave heating unit. The results showed that the relationship between the temperature and heating time is exponential and depends on the rock oxide contents. It was found that the iron oxides may be unstable at microwave and rocks with high levels of magnesium oxides and sulfates tend to be good absorbers of microwave. Rocks containing high levels of calcium, silicon, titanium, barium and chloride (NaCl) are not good absorbers of microwave. It was also noted that faster solid heating, lesser the efficiency of microwave drying.

Back analysis of a large landslide in a flysch rock mass

Flysch is a sedimentary rock consisting of a rhythmic alternation of hard (limestone, sandstone, siltstone) and weak (marl, mudstone, claystone) layers. Because of the presence of layers with different physical properties, the mechanical characterization of heterogeneous rock masses such as flysch is a real challenge. Different methods have been proposed in the literature to characterize flysch, combining empirical classification indexes with laboratory tests. Most of these methods, however, were specifically designed for tunneling and underground excavations, and their applicability to slope stability problems is not yet fully investigated. In this study, we analyze a large landslide in a cretaceous flysch rock in order to compare the mobilized strength at failure with those predicted by the modified GSI method (Marinos and Hoek, 2001). The landslide occurred in the Savena River basin (Northern Apennines of Italy) on April 6, 2013, with a volume of about 3 million m3. Soon after the failure, geological, geotechnical, and geophysical investigations were carried out to detect the failure mechanism and define the landslide geometry. Back analyses of the failed slope were performed using both limit equilibrium and finite difference methods to estimate the in situ strength of the flysch. The results show that the mobilized rock mass cohesion is very low (c ' ≈ 20 ÷ 40 kPa) and that the modified GSI method can predict the in situ strength only assuming a disturbance factor D = 1. Moreover, the analysis shows that the linearization criteria proposed in literature to compute the equivalent Mohr-Coulomb parameters remarkably overestimate the rock mass strength.

Lead isotopic evidence for interaction between plume and lower crust during emplacement of peralkaline Lovozero rocks and related rare-metal deposits, East Fennoscandia, Kola Peninsula, Russia

The Lovozero alkaline massif—an agpaitic nepheline syenite layered intrusion—is located in the central part of the Kola Peninsula, Russia, and belongs to the Kola ultramafic alkaline and carbonatitic province (KACP) of Devonian age. Associated loparite and eudialyte deposits, which contain immense resources of REE, Nb, Ta, and Zr, constitute a world class mineral district. Previous Sr, Nd, and Hf isotope investigations demonstrated that these rocks and mineral deposits were derived from a depleted mantle source. However, because the Sr, Nd, and Hf abundances in the Kola alkaline rocks are significantly elevated, their isotopic compositions were relatively insensitive to contamination by the underlying crustal rocks through which the intruding magmas passed. Pb occurring in relatively lower abundance in the KACP rocks, by contrast, would have been a more sensitive indicator of an acquired crustal component. Here, we investigate the lead isotopic signature of representative types of Lovozero rocks in order to further characterize their sources. The measured Pb isotopic composition was corrected using the determined U and Th concentrations to the age of the crystallization of the intrusion (376 ± 28 Ma, based on a 206Pb/204Pb versus 238U/204Pb isochron and 373 ± 9 Ma, from a 208Pb/204Pb versus 232Th/204Pb isochron). Unlike the previously investigated Sr, Nd, and Hf isotopes, the lead isotopic composition plot was well outside the FOZO field. The 206Pb/204Pb values fall within the depleted MORB field, with some rocks having lower 207Pb/204Pb but higher 208Pb/204Pb values. Together with other related carbonatites having both lower and higher 206Pb/204Pb values, the combined KACP rocks form an extended linear array defining either a ~2.5-Ga secondary isochron or a mixing line. The projection of this isotopic array toward the very unradiogenic composition of underlying 2.4–2.5-Ga basaltic rocks of the Matachewan superplume and associated Archean granulite facies country rock provides strong evidence that this old lower crust was the contaminant responsible for the deviation of the Lovozero rocks from a presumed original FOZO lead isotopic composition. Evaluating the presence of such a lower crustal component in the Lovozero rock samples suggests a 5–10% contamination by such rocks. Contamination by upper crustal rock is limited to only a negligible amount.

Complex remanent magnetization in the Kızılkaya ignimbrite (central Anatolia): Implication for paleomagnetic directions

Pyroclastic flow deposits, known as ash-flow tuffs or ignimbrites, are invaluable materials for paleomagnetic studies, with many applications for geological and tectonic purposes. However, little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy. In this work we investigate this issue by concentrating on the Kızılkaya ignimbrite, the youngest large-volume unit of the Neogene ignimbrite sequence of the Central Anatolian Volcanic Province in Turkey, bringing evidence of significant magnetic heterogeneities in ignimbrite deposits (magnetic mineralogy, susceptibility, magnetic remanence, coercivity, etc.) and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data. Six sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite. Isothermal remanence measurements point to low-Ti titanomagnetite as the main magnetic carrier at all sites; at some sites, the occurrence of oxidized Ti-magnetite and hematite is disclosed. The bulk susceptibility (km) decreases vertically at two out of six sections: its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base. In most cases, low km values relate to high coercivity of remanence (BCR) values, which range from 25 to >400mT, and to low S-ratios (measured at 0.3T) between 0.28 and 0.99. These data point to the occurrence of oxidized magnetic phases. We therefore consider the km parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized Ti-magnetite and hematite within the deposit. The characteristic remanent magnetization is determined after stepwise thermal and AF demagnetization and clearly isolated by principal component analysis at most sites. For these sites, the site-mean paleomagnetic direction is consistent with data from the literature. At a few other sites, the remanence is more complex: the direction moves along a great circle during demagnetization and no stable end-point is reached. The occurrence of oxidized Ti-magnetite or hematite as well as two remanence components with overlapping coercivity and blocking temperature spectra suggest that the Kızılkaya ignimbrite acquired first a thermal remanent magnetization and then, during the final cooling or a short time later, a secondary remanent magnetization component which is interpreted as a CRM acquired during post-emplacement devitrification processes. Notwithstanding the Kızılkaya ignimbrite is a single cooling unit, its magnetic properties suffered substantial variations laterally and vertically within the deposit. The Kızılkaya case shows that thick pyroclastic deposits should be sampled using a stratigraphic approach, at different sites and different stratigraphic heights at each individual sampling location, otherwise, under-sampling may significantly affect the paleomagnetic results. When sampling is performed on a short duration or on very poorly preserved deposits we recommend drilling the lower-central portion in the most strongly welded and devitrified facies. Such sampling strategy avoids complications arising from the potential presence of a pervasive secondary CRM masking the original ChRM.

Virtual palaeontology: the effects of mineral composition and texture of fossil shell and hosting rock on the quality of X-ray microtomography (XMT) outcomes using Palaeozoic brachiopods

X-ray microtomography (XMT) has become a popular tool for detailed investigations of a diverse range of fossils. However, XMT has not always guaranteed a satisfactory result, as the resolution of XMT images critically depends on the contrast between the fossil and its hosting rock. In this paper, XMT was applied to 11 Palaeozoic brachiopod specimens selected from a range of sedimentary rocks in order to investigate the extent of effects of mineral composition and texture in the rock and fossil shell on the quality of XMT outcomes. Our study shows that sufficient contrast in mineral composition and texture between the brachiopod shell and its infilling material is required to reproduce high-quality XMT results. Specifically, brachiopod specimens with their original calcium carbonate shell, infilled mainly with quartz grains, appear to produce the best XMT results characterized by sharply defined shell internal structures. We also found that diagenesis is significant in determining the XMT quality. Diagenetic processes including silicification and recrystallization in the brachiopod shell and/or the infilling material generally tends to diminish the resolution of the XMT results, although this impact is considerably complicated by the degree and aspect of diagenesis. Another factor of minor significance concerns the presence of bioclasts scattered in the hosting sediment that potentially could be confused with genuine shell internal structures.

Potassic volcanic rocks and adakitic intrusions in southern Tibet: Insights into mantle–crust interaction and mass transfer from Indian plate

Elucidating geodynamic processes at depth relies on a correct interpretation of petrological and geochemical features in magmatic records. In southern Tibet, both potassic volcanic rocks and adakitic intrusions exhibit high Sr/Y and La/Yb, and low Y and Yb concentrations. But these two rock types have contrasting temporal–spatial distributions and isotopic variations. Here we present a systematic study on the postcollisional potassic and adakitic rocks in order to investigate their petrogenetic links with the coeval mantle-derived ultrapotassic rocks and shed light on the potential input from underthrusted Indian continental crust. We found that adakitic intrusions with higher K2O/Na2O tend to display lower Y and higher SiO2, suggesting that the mantle-derived ultrapotassic melts, showing relatively high Y and Yb concentrations, only played a minor role in adakitic magmatism. Therefore, the unradiogenic 143Nd/144Nd and the dramatic decrease of zircon εHf(t) values since ~35Ma shown by postcollisional adakites should be interpreted as reflecting the crustal input from Indian plate. Unlike adakitic intrusions in southern Lhasa subterrane, potassic volcanic rocks share similar spatial distributions with ultrapotassic rocks, and their isotopic discrepancy is diminishing with volcanic activity becomes younger and migrates eastward. Evidence from whole-rock Pb and zircon Hf isotopes further indicates that potassic volcanic rocks are more likely to originate from partial melting of the overthickened and isotopically heterogeneous Lhasa terrane crust rather than the underthrusted Indian continental crust. The elevated Rb/Sr and varying Sr/CaO in potassic volcanic rocks provide an argument for sanidine+plagioclase+clinopyroxene as the major fractionating phases during magmatic differentiation. These findings not only highlight the significance of potassic and adakitic rocks in providing constraints on the geodynamic processes beneath southern Tibet, but also imply that special caution is needed if we attempt to probe into the nature of mantle lithosphere using isotopic tracers of the Tibetan ultrapotassic rocks.

Relationships between bright amplitudes in overburden rocks and leakage from underlying reservoirs on the Norwegian Continental Shelf

Identification of the locations where hydrocarbon traps leak is of significant practical importance, especially if the leakage controlled the present-day fluid contacts. We have investigated the fluid contacts of five structural traps offshore Norway that are dry or underfilled, and which have apparently had larger hydrocarbon columns in the past. The main focus of our work was to apply observations of bright amplitudes in overburden rocks in order to identify the most likely positions for vertical leakage, and to compare and contrast these observations from different parts of the Norwegian Continental Shelf. It was seen that bright amplitudes were present in overburden rocks above likely leakage locations in all of the investigated structures. The bright amplitudes line up along fault planes in some of the traps and, in other cases, are clustered along fault intersections. The leakage-related brights were only noted in parts of the overburden sequences, presumably because most of the overburden rocks did not have sufficient permeability to host the gas quantities that are needed for seismic imaging. We conclude that analyses of overburden brights above likely leakage locations can contribute to improved prediction of hydrocarbon–water contacts in the subsurface.

Petroleum geochemistry of crude oils and oil: source rock correlation of some wells in the North Western Desert, Egypt

Three crude oil and three extract samples collected from three source rocks namely Bahariya, Alam El Bueib, and Khatatba Formations from the Egyptian productive wells namely: Bed 2-1, Bed-2, and AG-1 oil fields. The oils were analyzed geochemically, including sulfur content and API gravity. Capillary gas chromatographic analysis was applied on each saturated hydrocarbons from oils and extracts to assess the correlation between the crude oils and the potential source rocks in order to confirm the indigenous sources for the petroleum generation of studied oil fields. The results show that the oil samples are originated mainly from marine organic sources deposited in reducing environment. By correlation between the source rocks and crude oils, we show that there is a good correlation between the extracts of Alam El Bueib and Khatatba source rocks with crude oils; while the extracts of Bahariya source rock show no correlation with the studied samples. These evidences indicate that Alam El Bueib and Khatatba source rocks seem to act as a source and reservoirs for oil generation in the studied oil fields.

Rare earth elements of shallow-water articulated brachiopods: A bathymetric sensor

Variations in environmental physicochemical parameters result in corresponding changes in seawater rare earth element (REE) distributions. For an archive to be utilized in paleoceanographic and paleoenvironmental reconstructions, it should record these variations. Therefore, an archive's proxy potentiality should be assessed analogous to modern oceanic settings.Articulated brachiopods of several shallow water localities (<500m) of different water masses were evaluated for their REE contents. The affects of oceanographic factors such as depth, salinity, and temperature were investigated for REE uptake by the shells. Uptake of REE by dorsal and ventral valves of articulated shells are unequivocal, whereas shells of Thecideidines, the umbo region and primary layer of the Terebratulids are anomalous, and should be avoided. Water temperature and salinity appear to have minor to moderate impacts on the partition coefficients of REEs between seawater and brachiopod calcite.The mean REESN pattern of shallow-water brachiopods is significantly different from that of their deep-water counterparts, with lower enrichments in LREEs and MREEs, and depletion in HREEs. Depth exercises a major control on the LREE and MREE fractionation with a milder one on HREE fractionation. The Ce/Ce* anomaly is not affected by either of these parameters in shallow-water settings, but in deep settings the depth effect dominates. Due to the importance of depth on REE fractionation in the shells from shallow settings, their LREESN to HREESN ratios (L:H) were divided into six discrete intervals for the bathymetric sensor. The bathymetric sensor was applied to some fossils and whole rock in order to estimate their paleodepths. The evaluation was successful in placing the Permian Gyanyima, the Pennsylvanian Naco, Boggy and the Silurian Chicotte, Becscie and Jupiter Formations in shallow depths (<15–50m), which is consistent with their paleoenvironmental settings.

Geological and geomechanical properties of the carbonate rocks at the eastern Black Sea Region (NE Turkey)

Turkey located in the Alpine-Himalayan Mountain Belt has 35% of the natural stone reserves of the world and has good quality marble, limestone, travertine and onyx reserves especially in the western regions of the country. The eastern Black Sea Region with a 1.4 million meters cubes reserve has a little role on the natural stone production in the country. For this reason, this paper deals with investigation on the potential of carbonate stone in the region and determination of the geological and geo-mechanical properties of these rocks in order to provide economic contribution to the national economy. While the study sites are selected among the all carbonate rock sites, the importance as well as the representative of the sites were carefully considered for the region. After representative samples were analyzed for major oxide and trace element compositions to find out petrochemical variations, the experimental program conducted on rock samples for determination of both physical and strength properties of the carbonate rocks. The results of the tests showed that there are significant variations in the geo-mechanical properties of the studied rock groups. The density values vary from 2.48 to 2.70 gr/cm3, water absorption by weight values range from 0.07 to 1.15% and the apparent porosity of the carbonate rocks are between 0.19 and 3.29%. However, the values of the UCS shows variation from 36 to 80 MPa. Tensile and bending strength values range from 3.2 to 7.5 MPa and 6.0–9.2 MPa respectively. Although the onyx samples have the lowest values of apparent porosity and water absorption by weight, these samples do not have the highest values of UCS values owing to occurrence of the micro-cracks. The UCS values of the rock samples were also found after cycling tests However, the limestone samples have less than 5% deterioration after freezing-thawing and wetting-drying tests, but travertine and onyx samples have more than 15% deterioration. Exception of the apparent porosity values of travertine samples, all geo-mechanical properties of the studied carbonate rocks were determined in the acceptance values given by Turkish Standards Institute (TSE) for using as a natural dimension stone. After these investigations, it is anticipated that in the near future the number of quarries and factories will increase and more types of natural stones will be discovered in the eastern Black Sea Region and thus this will provide economic contribution to the economy of the country.

Estimation of 3-D pore network coordination number of rocks from watershed segmentation of a single 2-D image

In this study, we have utilized 3-D micro-tomography images of real and synthetic rocks to introduce two mathematical correlations which estimate the distribution parameters of 3-D coordination number using a single 2-D cross-sectional image. By applying a watershed segmentation algorithm, it is found that the distribution of 3-D coordination number is acceptably predictable by statistical analysis of the network extracted from 2-D images. In this study, we have utilized 25 volumetric images of rocks in order to propose two mathematical formulas. These formulas aim to approximate the average and standard deviation of coordination number in 3-D pore networks. Then, the formulas are applied for five independent test samples to evaluate the reliability. Finally, pore network flow modeling is used to find the error of absolute permeability prediction using estimated and measured coordination numbers. Results show that the 2-D images are considerably informative about the 3-D network of the rocks and can be utilized to approximate the 3-D connectivity of the porous spaces with determination coefficient of about 0.85 that seems to be acceptable considering the variety of the studied samples.