Incorporating geological dip information into geophysical inversions

ABSTRACT Geological bodies are often linear structures that have well-defined strike direction and dip angle. We develop a new model objective function that allows this important information to be incorporated into geophysical inversions. A rotation matrix is applied to the horizontal and vertical derivatives of the model so that the derivative in an arbitrary direction is obtained. A model objective function that measures the flatness with respect to the rotated derivatives favors models that have elongated features with the specified strike and dip angle. Formulations for both 2-D and 3-D cases are presented, and they are illustrated using examples from dc resistivity and induced polarization (IP) problems. Synthetic and field examples show that an inversion carried out using known dip information produces a model that has higher resolution and provides a better representation of the true structure

Evaluating time-lapse borehole gravity for CO2 plume detection at SECARB Cranfield

Bureau of Economic Geolog

3D modeling of deep borehole electromagnetic measurements with energized casing source for fracture mapping at the Utah Frontier Observatory for Research in Geothermal Energy

We present a 3D numerical modelling analysis evaluating the deployment of a borehole electromagnetic measurement tool to detect and image a stimulated zone at the Utah Frontier Observatory for Research in Geothermal Energy geothermal site. As the depth to the geothermal reservoir is several kilometres and the size of the stimulated zone is limited to several 100 m, surface-based controlled-source electromagnetic measurements lack the sensitivity for detecting changes in electrical resistivity caused by the stimulation. To overcome the limitation, the study evaluates the feasibility of using a three-component borehole magnetic receiver system at the Frontier Observatory for Research in Geothermal Energy site. To provide sufficient currents inside and around the enhanced geothermal reservoir, we use an injection well as an energized casing source. To efficiently simulate energizing the injection well in a realistic 3D resistivity model, we introduce a novel modelling workflow that leverages the strengths of both 3D cylindrical-mesh-based electromagnetic modelling code and 3D tetrahedral-mesh-based electromagnetic modelling code. The former is particularly well-suited for modelling hollow cylindrical objects like casings, whereas the latter excels at representing more complex 3D geological structures. In this workflow, our initial step involves computing current densities along a vertical steel-cased well using a 3D cylindrical electromagnetic modelling code. Subsequently, we distribute a series of equivalent current sources along the well's trajectory within a complex 3D resistivity model. We then discretize this model using a tetrahedral mesh and simulate the borehole electromagnetic responses excited by the casing source using a 3D finite-element electromagnetic code. This multi-step approach enables us to simulate 3D casing source electromagnetic responses within a complex 3D resistivity model, without the need for explicit discretization of the well using an excessive number of fine cells. We discuss the applicability and limitations of this proposed workflow within an electromagnetic modelling scenario where an energized well is deviated, such as at the Frontier Observatory for Research in Geothermal Energy site. Using the workflow, we demonstrate that the combined use of the energized casing source and the borehole electromagnetic receiver system offer measurable magnetic field amplitudes and sensitivity to the deep localized stimulated zone. The measurements can also distinguish between parallel-fracture anisotropic reservoirs and isotropic cases, providing valuable insights into the fracture system of the stimulated zone. Besides the magnetic field measurements, vertical electric field measurements in the open well sections are also highly sensitive to the stimulated zone and can be used as additional data for detecting and imaging the target. We can also acquire additional multiple-source data by grounding the surface electrode at various locations and repeating borehole electromagnetic measurements. This approach can increase the number of monitoring data by several factors, providing a more comprehensive dataset for analysing the deep-localized stimulated zone. The numerical analysis indicates that it is feasible to use the combination of the energized casing and downhole electromagnetic measurements in monitoring localized stimulated zone at large depths

Introduction to special section: Mining and minerals exploration interpretation

Mineral deposits are found in a variety of geologic settings and ore-forming minerals can have a vast range of physical properties. The search for these deposits is also relatively near-surface thus far. These factors allow for a large number of possible airborne and ground-based techniques to be used in geophysical exploration. Deciding on the proper geophysical technique and survey layout requires an understanding of the target, its associated alteration, the variations in physical properties and the geologic and structural setting. Knowing the exploration history is important, particularly in exploration programs that are more mature. Interpretation of the data requires the integration of the myriad of information ranging from physical property models constructed from inversions or forward modeling, physical property data, geochemical data, mineral deposit model, and host geology. We envisioned a special section on mining geophysics to highlight the integrative nature of mining geophysics through a collection of papers using multiple geophysical data to provide geology and exploration rationale along with the interpretations. So in collaboration with the editor of Interpretation, we issued a call for papers that discussed geophysics as applied to mining, discussed all relevant geophysical data and provided geologic information and the exploration rationale along with the interpretations. The following papers provide insight into the importance of geophysics in mineral exploration from the belt or camp scale to exploration focused on a specific orebody. Wright and Koehler combine controlled-source audio magnetotelluric and gravity data in a previously explored terrain of the Carlin trend. The authors demonstrate that successive geophysical surveys, combined with geologic understanding and target model development were key to a significant gold discovery. Martinez and Li demonstrate that lithological interpretation techniques based on inversion of airborne gravity gradiometry and aeromagnetic data can be used to characterize an iron-ore formation in Minas Gerais. The authors show that lithology differentiation using either generic physical property constraints or geologic constraints can contribute to a geologic understanding at the deposit scale. Olaniyan et al. study the 3D geologic and structural setting of the Sudbury structure using an integration of geologic data with airborne gravity and magnetic data. Using standard 2.5D modeling and 3D Geomodeller software, they generate continuous surfaces in three dimensions for each geologic interface, which leads them to suggest a possible deformation history of the Sudbury structure. Woolrych et al. present data from a range of airborne and ground-based geophysical techniques that have contributed to the discovery of the Kitumba iron oxide copper gold (IOCG) deposit in central Zambia. The interpretation of geophysical data following an exploration criteria of an IOCG-type deposit model has opened up exploration for this style of deposit in Central Zambia. Lü et al. present a case study that demonstrates the use of integrating seismic, magnetotelluric, gravity, and magnetic data to interpret the 3D structure and deformation at depth in the Lu-Zong ore district of Eastern China. Insights were obtained into the fault systems and crustal architecture that are essential for understanding the Lu-Zong ore district mineral system and for mineral exploration at depth. Legault et al. present the results of three different airborne electromagnetic (EM) surveys over the Lalor copper-zinc-gold volcanogenic massive sulfide deposit, which is more than 500 m deep and is in the Flin Flon Greenstone Belt of north-central Manitoba. The active and passive source EM surveys span a five year period, which means that the development of EM systems over this period can be assessed

Free sulfurous acid (FSA) inhibition of biological thiosulfate reduction (BTR) in the sulfur cycle-driven wastewater treatment process

A sulfur cycle-based bioprocess for co-treatment of wet flue gas desulfurization (WFGD) wastes with freshwater sewage has been developed. In this process the removal of organic carbon is mainly associated with biological sulfate or sulfite reduction. Thiosulfate is a major intermediate during biological sulfate/sulfite reduction, and its reduction to sulfide is the rate-limiting step. In this study, the impacts of saline sulfite (the ionized form: HSO + SO ) and free sulfurous acid (FSA, the unionized form: HSO) sourced from WGFD wastes on the biological thiosulfate reduction (BTR) activities were thoroughly investigated. The BTR activity and sulfate/sulfite-reducing bacteria (SRB) populations in the thiosulfate-reducing up-flow anaerobic sludge bed (UASB) reactor decreased when the FSA was added to the UASB influent. Batch experiment results confirmed that FSA, instead of saline sulfite, was the true inhibitor of BTR. And BTR activities dropped by 50% as the FSA concentrations were increased from 8.0 × 10to 2.0 × 10mg HSO-S/L. From an engineering perspective, the findings of this study provide some hints on how to ensure effective thiosulfate accumulation in biological sulfate/sulfite reduction for the subsequent denitrification/denitritation. Such manipulation would result in higher nitrogen removal rates in this co-treatment process of WFGD wastes with municipal sewage

A chromosome-level draft genome of the grain aphid Sitobion miscanthi.

peer reviewed[en] BACKGROUND: Sitobion miscanthi is an ideal model for studying host plant specificity, parthenogenesis-based phenotypic plasticity, and interactions between insects and other species of various trophic levels, such as viruses, bacteria, plants, and natural enemies. However, the genome information for this species has not yet to be sequenced and published. Here, we analyzed the entire genome of a parthenogenetic female aphid colony using Pacific Biosciences long-read sequencing and Hi-C data to generate chromosome-length scaffolds and a highly contiguous genome assembly. RESULTS: The final draft genome assembly from 33.88 Gb of raw data was ∼397.90 Mb in size, with a 2.05 Mb contig N50. Nine chromosomes were further assembled based on Hi-C data to a 377.19 Mb final size with a 36.26 Mb scaffold N50. The identified repeat sequences accounted for 26.41% of the genome, and 16,006 protein-coding genes were annotated. According to the phylogenetic analysis, S. miscanthi is closely related to Acyrthosiphon pisum, with S. miscanthi diverging from their common ancestor ∼25.0-44.9 million years ago. CONCLUSIONS: We generated a high-quality draft of the S. miscanthi genome. This genome assembly should help promote research on the lifestyle and feeding specificity of aphids and their interactions with each other and species at other trophic levels. It can serve as a resource for accelerating genome-assisted improvements in insecticide-resistant management and environmentally safe aphid management.National Key R & D Plan of Chin

Inversion of three-dimensional direct current resistivity data

A direct current (d.c.) resistivity experiment investigates subsurface geo-electrical structures by measuring the electric field set up by introducing current into the earth. Information about geo-electrical structures is extracted by inverting the observed data to generate an image of the conductivity or to construct a conductivity model. The goal of this thesis is to develop efficient inversion techniques for the interpretation of three-dimensional (3d) d.c. resistivity data. The study assumes data consisting of pole-pole potentials measured over a regular grid on the surface for many current locations. The Born approximation is employed to linearize the inverse problem. The source of the electric field measured in the d.c. resistivity is the accumulated electric charges. Different aspects of the charge accumulation are reviewed, enlarged with new insights and presented in a unified notation. This provides the basis for understanding the fundamentals of d.c. resistivity experiments. Two algorithms are developed to image simple 2d conductivities. The first constructs a structural image by combining the charge density images obtained by inverting multiple sets of common current potentials. The second constructs a conductivity image directly. Processing and displaying the apparent conductivity, and constructing equivalent sources from secondary potentials are studied as the means of imaging. Assuming a multiplicative perturbation to a uniform half-space, the potential anomaly of pole-pole arrays is expressed as a depth integral of the logarithmic perturbation convolved with a kernel function in the horizontal directions. Applying the Fourier transform decomposes the data equation for a 3d problem into a set of id equations. A rapid approximate 3d inversion is developed based upon this decomposition by solving a sequence of id inversions in the wavenumber domain. The approximate 3d inversion is used to construct iterative inversion algorithms using the AIM (Approximate Inverse Mapping) formalism. The approximate inversion and an exact forward mapping are used to update the model successively so that the final result reproduces the observed data. The AIM inversion is applied to analyse a set of field data.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Summary of the sex-average map for <i>Pinctada fucata.</i>

<p>Summary of the sex-average map for <i>Pinctada fucata.</i></p

Genetic Mapping and QTL Analysis of Growth-Related Traits in <i>Pinctada fucata</i> Using Restriction-Site Associated DNA Sequencing

<div><p>The pearl oyster, <i>Pinctada fucata</i> (<i>P. fucata</i>), is one of the marine bivalves that is predominantly cultured for pearl production. To obtain more genetic information for breeding purposes, we constructed a high-density linkage map of <i>P. fucata</i> and identified quantitative trait loci (QTL) for growth-related traits. One F1 family, which included the two parents, 48 largest progeny and 50 smallest progeny, was sampled to construct a linkage map using restriction site-associated DNA sequencing (RAD-Seq). With low coverage data, 1956.53 million clean reads and 86,342 candidate RAD loci were generated. A total of 1373 segregating SNPs were used to construct a sex-average linkage map. This spanned 1091.81 centimorgans (cM), with 14 linkage groups and an average marker interval of 1.41 cM. The genetic linkage map coverage, Coa, was 97.24%. Thirty-nine QTL-peak loci, for seven growth-related traits, were identified using the single-marker analysis, nonparametric mapping Kruskal-Wallis (KW) test. Parameters included three for shell height, six for shell length, five for shell width, four for hinge length, 11 for total weight, eight for soft tissue weight and two for shell weight. The QTL peak loci for shell height, shell length and shell weight were all located in linkage group 6. The genotype frequencies of most QTL peak loci showed significant differences between the large subpopulation and the small subpopulation (<i>P</i><0.05). These results highlight the effectiveness of RAD-Seq as a tool for generation of QTL-targeted and genome-wide marker data in the non-model animal, <i>P. fucata</i>, and its possible utility in marker-assisted selection (MAS).</p></div