Geological Constraints Research Articles

Targeting Ni-Cu mineralization in the Canadian High Arctic large igneous province: integrating geochemistry, magmatic architecture and structure

Mafic-ultramafic subvolcanic intrusive complexes, at the 1–10-km scale, constitute favorable environments for the formation of orthomagmatic Ni-Cu-PGE sulfide deposits. Within 100–1000-km scale large igneous provinces (LIPs), the most favorable economic target areas may be difficult to identify using a traditional regional exploration approach. We report results of field and laboratory studies focused on an integrated geochemical-architectural model for the Ni-Cu-PGE sulfide potential of the High Arctic large igneous province (HALIP) of Canada, the largest and best-exposed portion of this circum-arctic LIP. Previous lithogeochemical studies of the Canadian HALIP (130–80 Ma) concluded that subalkaline mafic units located on Axel Heiberg Island were more prospective than younger, alkalic igneous rocks (alkaline basalts to basanites) exposed on northern Ellesmere Island. Mapping carried out for this study revealed the presence of abundant subalkaline igneous rocks on western Ellesmere Island. We interpret these units as an extension of the Schei Sills, a stratigraphically bound sequence of intrusions exposed along a ~ N-S belt on eastern Axel Heiberg Island. Samples from the Schei Sills and from the Middle Fiord Intrusive Complex (~ 20 km2, central Axel Heiberg Island) show Cu/Zr values above and below unity, consistent with complementary sulfide enrichment and removal, respectively, within these intrusive systems. The spatial association of the Schei Sills with the post-emplacement Eocene Stolz Thrust is noteworthy, as later thrusting associated with the Paleogene Eurekan Orogeny caused the uplift of deeper parts of the HALIP subvolcanic feeder system and associated wall-rock stratigraphy. Absolute Ir-group PGE contents are low throughout the HALIP; however, Pt-group PGE contents range widely among analyzed tholeiitic intrusive rocks. For example, relatively elevated Pt + Pd values of 10–30 ppb in samples from the Middle Fiord Intrusive Complex and the Schei Sills suggest heightened prospectivity in these two areas. In contrast, tholeiitic flood basalts in the Strand Fiord Formation and associated intrusions exposed in western Axel Heiberg Island (~ 95 Ma) exhibit Cu/Zr < 1 and low Pt + Pd contents (below 10 ppb). The ca. 120 Ma magmatic event associated with the Schei Sills and Middle Fiord Intrusive Complex appears to have generated magmas that are more prospective than those of the younger (ca. 95 Ma) magmatic pulse associated with the flood basalts of the Strand Fiord Formation. This work demonstrates that not all architectural elements of a LIP are equal in terms of metallogenic potential, and that nested zones of higher prospectivity can be identified through the integration of several geological constraints.

Stope boundary optimization for an underground copper deposit using mixed integer linear programming based algorithm

Optimal ore body boundary and production area geometry (Stope) are essential to maximize the profit from an underground mining project subject to inherent physical, geotechnical and geological constraints. Number of researches have been introduced for stope boundary optimization but true optimal solution in three dimensional spaces is still out of reach. This article proposed a computer programming based optimization model using mixed integer linear programming based algorithm that incorporate stope boundary optimization with varying cost of mining and selling price of the metal. An actual ore body model was taken as case study to implement the algorithm in real mining scenario. In validation study, it is observed that, by using proposed model, the profit can be increased by 10% - 15% as compared to the present stoping practice. Simulating the optimal stope boundary by changing the various cost and price parameters helps to opt the best possible option for a given mining scenario to make most realistic plan.

Absence of West Antarctic-sourced silt at ODP Site 1096 in the Bellingshausen Sea during the last interglaciation: Support for West Antarctic ice-sheet deglaciation

During the last interglaciation (LIG; ∼129–116 ka), global mean sea level (GMSL) was 6–9 m above present. However, the source, or sources, of the higher-than-present sea level are only partially confirmed with far fewer geologic constraints than GMSL itself. Because of modest LIG Greenland Ice-Sheet retreat that raised sea level by < 2.5 m, Antarctic ice sheets are hypothesized to have contributed significantly to the LIG GMSL highstand, but direct evidence is limited. Here we infer ice-sheet presence or absence on West Antarctica and the Antarctic Peninsula using sediment geochemistry in the Bellingshausen Sea at Ocean Drilling Program (ODP) Site 1096. In particular, a combination of Sr-Nd-Pb isotopes and trace-element ratios allows differentiation between silt sourced from West Antarctica and the Antarctic Peninsula. From the Holocene (<11.7 ka) back through Marine Isotope Stage (MIS) 5d (∼116 ka), we find in ∼50% of our samples glacially eroded silt sourced from under the West Antarctic Ice Sheet that was transported to the Bellingshausen Sea in the Antarctic Circumpolar Current, in addition to silt sourced from under the proximal Antarctic Peninsula Ice Sheet. However, West Antarctic-sourced silt is absent during the LIG (MIS 5e) when only Antarctic Peninsula-sourced silt was deposited at ODP Site 1096. This lack of West Antarctic-sourced silt is consistent with the two ice-core constraints on West Antarctic Ice Sheet LIG size, which combined with our record point towards the absence of the West Antarctic Ice Sheet during the LIG. We therefore provide the first marine-based sedimentary evidence that supports West Antarctic Ice-Sheet absence during the LIG.

The Slope-Attribute-Regularized High-Resolution Prestack Seismic Inversion

Prestack seismic inversion can be regarded as an optimization problem, which minimizes the error between the observed and synthetic data under the premise of certain geological/geophysical a priori information constraints. It has been proved to be a powerful approach for reconstructing the subsurface properties and building the elastic parameter models (e.g., P- and S-wave velocity, and density). With respect to the specific expressions of a priori information, the starting model and regularization are expected to be the most widely used and indispensable constraints to reconstruct structural features and subsurface properties. The conventional prestack inversion (trace-by-trace) methods perform well when the geological structure of the target area is not too complex. However, due to the lack of lateral constraint, such trace-independent methods are inevitably limited by their capability of characterization (including accuracy, resolution, and robustness) in the case of geologically complex structures, such as tilted stratum and steep faults. The geological structure-guided constraint, herein referred to as the seismic slope attribute, can be exploited as a lateral constraint integrated into the prestack inversion algorithm. In this work, the seismic slope attribute is introduced to the amplitude variation with offset/angle inversion from two aspects, i.e., starting model building and regularization penalty. Firstly, using the seismic slope attribute, instead of the traditional manual interpreted geological horizons, as a constraint, the well-log data are interpolated to build the initial model. The interpolation algorithm is formulated as solving the inverse problem by using the shaping regularization method rather than the kriging-based algorithm. Secondly, by rotating the coordinate system according to the seismic slope attribute, the directional total variation regularization is used as a constraint to improve the resolution (in both vertical and horizontal directions) and lateral continuity of the inversion results. Finally, the proposed methods are applied to synthetic and real seismic data. Synthetic tests and field data applications demonstrate that the proposed method is capable of revealing complex structural features and achieving stabilized inversion of multi-parameters with less uncertainty.

Morphometric investigations on the NW Bitlis-Zagros mountain range (SE Turkey): Implications for the internal deformation of the western Turkish-Iranian Plateau

Collision of the Arabian and Eurasian plates has resulted in uplift of the Turkish-Iranian Plateau, where debate continues over how post-collisional convergence is being converted to strain. The internal deformation models of the plateau have taken into account the distribution of deformation in the NW-trending Bitlis-Zagros Mountain Range (BZMR), the southern boundary of the collision. The western end of the BZMR is marked by contrasting topographic relief resulting from the coupling of tectonic and erosional processes. This region providing an excellent record for undertaking quantitative analysis which can improve our understanding of its tectonic evolution. Mountain front analyses reveal that each fault segment located in front of the western BZMR falls within the limits of Class-1 that corresponds to an uplift rate of >0.5 mm yr−1. Hypsometric and basin asymmetry analysis were analyzed for 93 drainage basins, indicating that weakly to moderately eroded basins can be moderately to strongly asymmetric but show no uniform tilting direction. Channel concavity, integral and knickpoint analyses suggest that, apart from the thrust fault that represents the margin of the collision zone, there is no pronounced single geological constraint that causes differential tectonic uplift and furthermore implies that the effect is distributed across multiple different structures. The findings of this study suggest that continuous lower rate horizontal displacement has occurred in this region since the onset of collision, but also indicates that the western end of the BZMR represents a zone of higher convergence, in which shortening is being converted to the vertical plane strain.

Physical simulation and compatibility evaluation of multi-seam CBM co-production: Implications for the development of stacked CBM systems

Multi-layer co-production is a mainstream method for efficient development of coalbed methane (CBM) and coal series gas under multi-seam conditions. However, interlayer interferences during CBM co-production caused by differences in reservoir properties (especially permeability and pressure) between stacked CBM systems severely restrict the output of CBM from the production layers. The identification of interlayer interferences and optimization of production layer combinations are important scientific issues that need to be explored to achieve high CBM production. Physical simulation is an effective means of accomplishing this research objective. Physical simulations of CBM co-production were performed under designed permeability and pressure combinations based on self-developed experimental equipment, which is mainly composed of an injection subsystem, a vacuum subsystem, the model body subsystem, and a separation and metering subsystem. Coal samples were collected from three CBM basins in China to form a series of five permeability levels, specifically 0.2, 2, 10, 50, and 100 mD. We focused our analysis on the contribution of gas production from each production layer using the gas flow data obtained from the physical simulation experiments. The co-mining compatibility of the production layers is divided into four types based on the grading evaluation of gas contribution: Grade I, II, and III compatible, and incompatible, which represent gas production contribution of the weak seam ≥37.5%, 25%–37.5%, 12.5%–25%, and ≤12.5%, respectively. On this basis, a template for discriminating CBM co-production compatibility is constructed using the permeability ratio and pressure difference as basic parameters. The gas and water production data of representative CBM wells in the Bide-Santang basin were used to verify the reliability of the template, and the compatibility discrimination results show consistency with the production data. The average daily gas production per unit of coal thickness presents a decreasing trend with deteriorating compatibility of co-producing seams. Finally, an integrated technical process for the development of stacked CBM systems is proposed, including the hierarchical optimization of production layer combinations, identification of interlayer interferences and sources of produced water, and selection of suitable development methods and technology. We divided the production layer combinations into four types representing different development potentials based on the hierarchical method: most favorable, favorable, sub-favorable, and unfavorable. Suggestions are made for the key geological constraints (weak water-bearing reservoir, compatibility of CBM systems, shallow groundwater interference, and deep CBM condition) and specific development strategies for different types of production layer combinations. This study will enrich the geological understanding of CBM co-production and provide theoretical and technical support for the efficient development of stacked CBM systems.

Geological constraints on the mechanisms of slow earthquakes

The recognition of slow earthquakes in geodetic and seismological data has transformed the understanding of how plate motions are accommodated at major plate boundaries. Slow earthquakes, which slip more slowly than regular earthquakes but faster than plate motion velocities, occur in a range of tectonic and metamorphic settings. They exhibit spatiotemporal associations with large seismic events that indicate a causal relation between modes of slip at different slip rates. Defining the physical controls on slow earthquakes is, therefore, critical for understanding fault and shear zone mechanics. In this Review, we synthesize geological observations of a suite of ancient structures that were active in tectonic settings comparable to where slow earthquakes are observed today. At inferred slow earthquake regions, a range of grain-scale deformation mechanisms accommodated slip at low effective stresses. Material heterogeneity and the geometric complexity of structures that formed at different inferred strain rates are common to faults and shear zones in multiple tectonic environments, and might represent key limiting factors of slow earthquake slip rates. Further geological work is needed to resolve how the spectrum of slow earthquake slip rates can arise from different grain-scale deformation mechanisms and whether there is one universal rate-limiting mechanism that defines slow earthquake slip.

The Age of the Epithermal Gold–Silver Mineralization at the Kubaka Deposit (Omolon Cratonic Terrane, Northeast Russia): Geological and Isotopic-Geochronological (U–Pb, 40Ar/39Ar) Constraints

The Age of the Epithermal Gold–Silver Mineralization at the Kubaka Deposit (Omolon Cratonic Terrane, Northeast Russia): Geological and Isotopic-Geochronological (U–Pb, 40Ar/39Ar) Constraints

Taking the heat out of British Jurassic septarian concretions

AbstractSeptarian carbonate concretions in marine mudrocks contain calcite cements that should represent evolving conditions from ambient temperature, shallow subsurface environments to warmer, burial diagenetic conditions. Clumped isotope results from British Middle and Upper Jurassic concretions indicate that most concretion body calcites formed at temperatures between 9 ± 5°C and 18 ± 5°C from marine pore waters with δ18O values between 0.2 ± 1.1‰ and −2.2 ± 1.1‰VSMOW. Early diagenetic, brown, fibrous calcite fracture cements mostly formed at temperatures between 15 ± 5°C and 19 ± 5°C, again from marine‐derived pore fluids with δ18O compositions between −0.5 ± 1.1‰ and 0.3 ± 1.2‰VSMOW. Two of these cements showed evolution to warmer temperatures and more evolved pore fluids with growth, indicating transition to deeper burial conditions. Later diagenetic, sparry calcite cements gave more variable temperatures but all indicated involvement of meteoric pore fluids. The highest clumped isotope temperature (43 ± 6°C) is within error of the 50°C regional maximum burial temperature estimate. These results are consistent with published geological and stable isotope constraints on the formation of Jurassic septarian concretions and highlight their potential as robust archives of marine benthic palaeotemperatures. Some of these results differ from clumped isotope data in an earlier study that reported higher temperatures for concretion body and early diagenetic fibrous cement fringes probably due to methodological differences.

Machine learning based fast forward modelling of ground-based time-domain electromagnetic data

Inversion of large-scale time-domain electromagnetic surveys are computationally expensive and time consuming. Deterministic or probabilistic inversion schemes usually require calculations of forward responses, and often thousands to millions of forward responses are computed. We propose a machine learning based forward modelling approach as a computationally feasible alternative to approximate numerical forward modelling where a neural network is employed to model the relationship between the resistivity models and corresponding forward responses. For training of the neural network, we generated forward responses using conventional numerical algorithm for 93,500 resistivity models derived from different surveys conducted in Denmark representing typical resistivities of sedimentary geological layers. The input resistivity models and the network target outputs, i.e. forward responses, are scaled using a novel normalization strategy to ensure each gate is equally prioritized. The performance of the network is evaluated on two test datasets consisting of 8942 resistivity models by comparing the forward responses generated by the neural network and the conventional algorithm. We also measure the performance for the time derivatives of forward responses, i.e. dB/dt, by incorporating a system response. The results show that the proposed strategy is at least 13 times faster than commonly used accurate modelling methods and achieves an accuracy of 98% within 3% relative error, which is comparable to data uncertainty. Additional experiments on surveys from two other continents show that the results generalize in similar geological settings. Thus, under certain geological constraints, the proposed methodology may be incorporated into the pre-existing inversion structures, allowing for significantly faster inversion of large datasets.

Review of Iberia–Eurasia plate‐boundary basins: Role of sedimentary burial and salt tectonics during rifting and continental breakup

AbstractWe document the role of sedimentary burial and salt tectonics in controlling the deformation style of continental crust during hyperextension. The Iberian‐European boundary records a complex history of Cretaceous continental extension, which has led to the development of so‐called smooth‐slope type basins. Based on the review of the available geological constraints (crustal‐balanced cross‐sections, sedimentary profile evolution, RSCM thermometer, low‐temperature thermochronology) and geophysical data (Bouguer anomaly, Moho depth, seismic reflection profiles and Vp/Vs velocity models) on the Tartas, Arzacq, Cameros, Parentis, Columbrets, Mauléon, Basque‐Cantabrian and Internal Metamorphic Zone basins, we shed light on the main characteristics of this type of basin. This synthesis indicates that crustal thinning was influenced by two decoupling horizons: the middle crust and Triassic prerift salt, initially located between the basement and prerift sedimentary cover. These two horizons remained active throughout basin formation and were responsible for depth‐dependent thinning of the crust and syn‐rift salt tectonics. We therefore identify several successive deformation phases involving (a) pure shear dominated thinning, (b) simple shear dominated thinning and (c) continental breakup. In the first phase, distributed deformation resulted in the development of a symmetric basin. Field observations indicate that the middle and lower crust were under dominantly ductile conditions at this stage. In the second phase, deformation was localised along a crustal detachment rooted between the crust and the mantle and connecting upwards with Triassic prerift salt. During continental breakup, basin shoulders recorded the occurrence of brittle deformation, whereas the hyperextended domain remained under predominantly ductile thinning. The formation of smooth‐slope‐type extensional basins was intrinsically linked to the combined deposition of thick syn‐rift and breakup sequences, and regional salt tectonics. They induced significant burial and allowed the continental crust and the prerift sequence to deform under high temperature conditions from the rifting to continental breakup stages.

Comment on “Crustal faults in the Chilean Andes: geological constraints and seismic potential” by Santibáñez et al. (2019), Andean Geology 46 (1): 32-65

Understanding the location and nature of Quaternary active crustal faults is critical to reduce both the impact of fault rupture and strong ground motions hazards (when these faults rupture causing earthquakes). It is also important for understanding how and where deformation related to plate tectonics is accommodated along geological structures (oftentimes faults and folds). In Chile, work on active tectonics in the upper crust (neotectonics or earthquake geology) is relatively new, in particular regarding fault-focused studies. Therefore, any effort to further progress in our understanding of active fault systems for the benefit of the public, and for aiding local and regional governments and the earthquake engineering and scientific community with mitigation strategies should be applauded. Demonstrating where active faults are located through careful mapping, and to determine how fast they accommodate tectonic deformation and their seismic and fault rupture hazards are key questions in neotectonics. Recently Santibáñez et al. (2019) explore active fault systems in the Chilean Andes. In their paper they outline active and potentially seismogenic (i.e., earthquake producing) fault systems in the Chilean Andes through a review of the literature, seismicity, case studies (earthquakes), and modeling data and then they define potential tectonic domains for subdivision of Chile. These domains were suggested to allow “a first-order approach for seismic potential assessment” (Santibáñez et al., 2019). The three subdivisions they suggest, i.e., domains are the External Forearc, Inner Forearc and Volcanic Arc, were proposed based on several fault parameters (e.g., fault length), case studies, the morphotectonic setting and seismicity. Their paper generates a great foundation to build upon for both the active tectonics and geological hazards community, in addition to being useful for potential end users such as the Chilean local and national government from a planning perspective. Although the Santibáñez et al. (2019) paper takes steps in the right direction, and should be considered an important contribution to the scientific community, this comment addresses three potential issues with their analysis and conclusions that should be reflected upon by the seismic hazard and active tectonics community. These ideas are summarized below and expanded on in detail thereafter.

Evolution characteristics of maturity-related sterane and terpane biomarker parameters during hydrothermal experiments in a semi-open system under geological constraint

In order to accurately assess the thermal maturity of highly/over-mature shales in Paleozoic strata in southern China, hydrothermal experiments of shale samples from the Dalong Formation from bed 18 of well-exposed Shangsi PTB Section was conducted in a semi-open system under various conditions of geological constraint. The saturated extracts of pyrolyzed shale samples were subjected to gas chromatography and mass spectrometry (GC-MS) analyses. The results indicated that hydrothermal experiments of Dalong shales in the presence of fluid pressure (FP), lithostatic stress (LS), water, catalyst of clay minerals and trace elements, is partially equivalent to catalytic hydropyrolysis in terms of the catalytic hydrogen effect for the release of bound biomarkers from geomacromolecules of kerogen and asphaltene. The evolutional trend of maturity-related biomarkers were classified into the following three categories: (a) the most common maturity parameters (e.g., Ts/(Ts + Tm) and C29S/(S + R)) initially increased and then decreased with a pyrolysis temperature (450 °C) at the reversal point during maturation; (b) the parameters (e.g., C32S/(S + R)) primarily increased or decreased and reached a temperature (400 °C) of tuning point, and then remained unaltered with increasing temperature (c) the parameters (e.g., C27DS/S); firstly increased, and then declined at a specific turning point temperature (425–500 °C), and thereafter continued to increase until the end of heating process. As a result, the threshold temperature for the release of bound sterane or terpane occurred in the range 400–500 °C. Most maturity-related sterane and terpane biomarker parameters cannot be applied to evaluate the maturity of highly/over-mature shale. However, the C30M/C30H ratio and S/T ratio, which are strongly correlated with temperature, may be employed to assess extremely mature shale from these Paleozoic strata due to the integrated effects of multiple factors in the thermal evolution process of biomarkers. This is very important for the exploration and development of shale gas in southern China. Additionally, the values of several source-related biomarker parameters derived from C27–29 regular steranes are relatively constant during maturation, such as the ternary plot of the C27–29 αααR sterane versus the C27/C29 αααR sterane ratio. These are useful indicators for distinguishing the genetic source of highly/over-mature shales.

A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: active fault and seismogenic source databases for southern Malawi

Abstract. Seismic hazard is commonly characterised using instrumental seismic records. However, these records are short relative to earthquake repeat times, and extrapolating to estimate seismic hazard can misrepresent the probable location, magnitude, and frequency of future large earthquakes. Although paleoseismology can address this challenge, this approach requires certain geomorphic setting, is resource intensive, and can carry large inherent uncertainties. Here, we outline how fault slip rates and recurrence intervals can be estimated by combining fault geometry, earthquake-scaling relationships, geodetically derived regional strain rates, and geological constraints of regional strain distribution. We apply this approach to southern Malawi, near the southern end of the East African Rift, and where, although no on-fault slip rate measurements exist, there are constraints on strain partitioning between border and intra-basin faults. This has led to the development of the South Malawi Active Fault Database (SMAFD), a geographical database of 23 active fault traces, and the South Malawi Seismogenic Source Database (SMSSD), in which we apply our systems-based approach to estimate earthquake magnitudes and recurrence intervals for the faults compiled in the SMAFD. We estimate earthquake magnitudes of MW 5.4–7.2 for individual fault sections in the SMSSD and MW 5.6–7.8 for whole-fault ruptures. However, low fault slip rates (intermediate estimates ∼ 0.05–0.8 mm/yr) imply long recurrence intervals between events: 102–105 years for border faults and 103–106 years for intra-basin faults. Sensitivity analysis indicates that the large range of these estimates can best be reduced with improved geodetic constraints in southern Malawi. The SMAFD and SMSSD provide a framework for using geological and geodetic information to characterise seismic hazard in regions with few on-fault slip rate measurements, and they could be adapted for use elsewhere in the East African Rift and globally.

Geological constraints on the Western Kohat foreland basin, Khyber Pakhtunkhwa, Pakistan: Implication from 2D and 3D structural modelling

The Kohat Foreland Basin is an outcome of continental collision between Indian and Eurasian plates defining the southern edge of Himalayan Orogenic System in the north-western Pakistan. This study constrains the structural geometry and kinematics in 2-D and 3-D workflow, evaluation of the role of multiple detachments and the structural correlation between surface and sub-surface geology of the western Kohat Foreland Basin. The structural style of the western Kohat Foreland Basin evinces the thin skin deformation associated with a couple of structural detachments i.e. i) base-Eocene shale/ evaporite sequence ii) the upper interface of crystalline basement. These detachments separate the outcropping and buried stratigraphic sequence of the Kohat Foreland Basin into upper and lower structural-stratigraphic domains. The lower domain has a series of north-dipping or south-verging fold-thrust assemblages incorporating a rigid rock sequence of EoCambrian to Paleocene. The comparatively more ductile rocks of the upper domain comprising of Eocene to Pliocene are deformed into tight, overturned, doubly plunging and internally faulted anticlines intervened by broad synclines. The two domains dictate different deformational behavior and structural style, deforming in total disharmony; hence the structural geometry of shallow units does not match the sub-surface rocks. The total 37% of shortening in the sedimentary cover was revealed by structural balancing in 2-D and 3-D kinematic modelling. Stress analysis of Gurguri Fault unveiled 40% failure susceptibility and recorded positive values of effective normal stress (σn) with an orientation of maximum principle stress (σ1) as N17°.

Rethinking Geologic Carbon Storage Capacity: An Approach With Practical Considerations

A realistic and practical understanding of storage capacity is essential during the scoping and planning phases of carbon capture, utilization, and storage (CCUS) projects. This study developed from the need to redefine carbon storage capacity in a way that it provides CCUS project developers with the information they need, not only on the size of the accessible pore volume they would require, but also –and as importantly- on the rate at which CO2 can be injected into it considering geological, technical, and economic constraints. In this paper, we think of geologic storage capacity as the rate at which CO2 can be technically and economically injected into an accessible pore volume for a period of time constrained by either a maximum injection pressure or a geologic boundary. We applied this concept to a region in the Offshore Northern Gulf of Mexico to understand the opportunities of its oil and gas fields. To estimate the accessible storage capacity we used EASiTool (Enhanced Analytical Simulation Tool) capacity calculator, a closed-form analytical solution in a public Windows application that provides fast, yet reliable estimates in any geologic setting. Results from EASiTool capacity assessments indicate that the total accessible CO2 storage capacity for pure carbon storage (no production) in oil and gas fields within the area of study is up to ~200 MTonnes. This paper illustrates how an average, representative reservoir in the area of study would have an open boundary storage capacity of 2.3 MTonnes, accessible over a period of 8 years at a rate of 0.28 MTonnes/year through one injection well. This carbon storage resource is an attractive complement to the vast storage capacity of the Offshore Northern Gulf of Mexico stratigraphy.

Evolution of the Alpine orogenic belts in the Western Mediterranean region as resolved by the kinematics of the Europe-Africa diffuse plate boundary

The West European collisional Alpine belts are the result of the inversion, initiated in the middle Cretaceous, of the complex western Neotethys and the Atlantic continental rift domains and closure of remnants of Tethys between the North Africa and European cratons. While the kinematics of Africa relative to Europe is well understood, the kinematics of microplates such as Iberia and Adria within the diffuse collisional plate boundary is still a matter of debate. We review geological and stratigraphic constraints in the peri-Iberia fold-thrust belts and basins to define the deformation history and crustal segmentation of the West European realm. These data are then implemented with other constraints from recently published kinematic and paleogeographic reconstructions to propose a new regional tectonic and kinematic model for Western Europe from the late Permian to recent times. Our model suggests that the pre-collisional extension between Europe and Africa plates was distributed and oblique, hence building discontinuous rift segments between the southern Alpine Tethys and the Central Atlantic. They were characterised by variably extended crust and narrow oceanic domains segmented across transfer structures and micro-continental blocks. The main tectonic structures inherited from the late Variscan orogeny localized deformation associated with rifting and orogenic belts. We show that continental blocks, including the Ebro-Sardinia-Corsica block, have been key in accommodating strike-slip, extension, and contraction in both Iberia and Adria. The definition of a new Ebro-Sardinia-Corsica block allows refining the tectonic relationships between Iberia, Europe and Adria in the Alps. By the Paleogene, the convergence of Africa closed the spatially distributed oceanic domains, except for the Ionian basin. From this time onwards, collision spread over the different continental blocks from Africa to Europe. The area was eventually affected by the West European Rift, in the late Eocene, which may have controlled the opening of the West Mediterranean. The low convergence associated with the collisional evolution of Western Europe permits to resolve the control of the inherited crustal architecture on the distribution of strain in the collision zone, that is otherwise lost in more mature collisional domain such as the Himalaya.

Lateral Structural Variation of the Lithosphere‐Asthenosphere System in the Northeastern to Eastern Iranian Plateau and Its Tectonic Implications

AbstractThe Iranian plateau is a natural laboratory for deciphering the lithospheric deformation and deep dynamics in response to the Neo‐Tethyan subduction and subsequent Arabia‐Eurasia continental collision. Here we used S‐wave receiver function data from a dense seismic array to construct the structural image of the lithosphere‐asthenosphere system across the northeastern to eastern Iranian plateau. The lithosphere‐asthenosphere boundary (LAB) is consistently imaged, being relatively flat at 80–90 km depth in eastern Iran, but deepening northward to ∼120 km depth beneath the Kopeh Dagh‐Turan platform boundary with an overall “root‐like” shape in northeastern Iran. A shallower (&lt;45 km) and a deeper Moho (∼50–55 km) are also observed beneath eastern and northeastern Iran, respectively, suggesting similar crustal deformation to mantle lithosphere but different patterns laterally. Moreover, a strong positive velocity discontinuity (PVD) is detected at ∼170 km depth beneath eastern Iran, possibly representing the base of an asthenospheric low‐velocity layer (LVL). Waveform modeling reveals large velocity contrasts of ∼4%–6% over a depth range of less than 30 and 20 km, respectively, across the LAB and the asthenospheric PVD. Combining our new results with geological and petrological constraints, we deduced that the asthenospheric LVL contains a small amount of melt, with sharp boundaries separating from the nearly melt‐free lithosphere above (LAB) and deeper mantle below (PVD). The observed structural variations of the lithosphere‐asthenosphere system across the study region may result from the complex lithospheric deformation in response to the Arabia‐Eurasia collision and effects of multiple tectono‐thermal events associated with the earlier Neo‐Tethyan subduction.

Prediction of properties of reservoir using Artificial Neural Network and Monte Carlo Simulation

Two methods for forecasting reservoir distribution are used: Monte Carlo Simulation and Artificial Neural Network. The data used in this research was obtained from the drilling sheet report of the Efe04 well located in the Northern Niger Delta Depobelt. The operator released the data set of the Efe field. Amukpe well data from the Amukpe field was also used as part of the test data to see how the model works on different fields. To minimize uncertainties, only the surface drilling parameters are used for the model. Mode of operation (rotation or sliding), Torque, Surface Revolution, Flow rate (gallons per minute), Stand Pipe Pressure, Revolutions per Minute, hole size. When reservoir distribution can be predicted, it is extremely beneficial since it increases exploration accuracy and lowers costs by delaying the next round of exploration. Geostatistics, on the other hand, is rarely used in areas with few wells drilled. A new technique called Geology Driven Integration Tool (GDI) has been developed to estimate reservoir parameters when just a few wells are available. Due to the lack of well data and regional geological constraints in the GDI model, several pseudo-wells are constructed by Monte Carlo Simulation to make up for the deficiency of a few real wells. They can also be used to create fake seismograms. To determine the weighting factors that link the selected seismic attributes to the given reservoir features, the appropriate seismic attributes and the given reservoir parameters are input to the Artificial Neural Network (ANN). In the end, the ANN is trained on all of the seismic data in the area and then used to estimate reservoir property distribution. In addition to the areas that have already been explored, the estimated results suggest exploring the southern portion of the Efe field and the northern portion of the Efe field as potential prospect locations. In the southern half of the Amukpe field, the gas zone's net thickness is expected to rise to 27 meters, thanks to increased porosity of 27%. North of the Efe field, a 15-25-meter-thick porosity-rich reservoir is predicted to be distributed.

Geological and geophysical constraints on Itokawa’s past spin periods

Itokawa has two distinct terrain types, rough highlands, and smooth lowlands. The lowlands formed by the movement of fine-grained materials from the highlands into topographic lows, covering up large boulders and producing a smooth surface. The topography of asteroids is a function of the shape, interior density, and spin rate. Itokawa, like many near-earth objects, may have experienced changes in its spin period due to YORP. Changes in spin period compared with the current 12.13 h period, may result in changes in the location of topographic lows and thus the concentration of fines in the lows. Under faster spin periods, ∼8 h or less, the northern topographic low, currently Sagamihara, changes location, but the southern lowland, Muses-Sea, stays in the same location. Above ∼8 h the topographic lows match the current geographic extent of the fine-grain lowlands. Current estimates of the timescale of regolith migration based on seismic shaking span several orders of magnitude. However, if these can be further refined, the location of the northern lowlands could be used as a constraint on the past spin rates of Itokawa The methods used in this study could be applied to other asteroids and may place an independent constraint on past spin periods.