The journey of K-MORBs, told through geological, geochemical and geophysical data

Geothermal resources assessment in Hawaii

Mineral resource potential mapping is an important procedure in mineral resource assessment. The aim of this study is to analyze relationships between sedimentary deposits and related factors and integrated the relationships using probabilistic and statistical models in GIS environment to identify areas that have not been subjected to the same degree of exploration. For this, a variety of spatial geological data were compiled, evaluated and integrated to produce a potential map for deposits in the Gangreung area, Korea. This empirical approach assumes that all deposits share a common genesis and comprises three main steps such as identification of spatial relationships, quantification of identified spatial relationships and integration of multiple quantified spatial relationships. For this, a spatial database including sedimentary mineral deposit, topographic, geologic, geophysical and geochemical data were constructed for the study area using Geographic Information System (GIS). The used 55 sedimentary mineral deposits and the related to factors, geological data such as lithology and fault, geochemical data such as Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sr, V, W, Zn, Cl, F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> , PO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-</sup> , NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> , NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-</sup> , HCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> , pH, Eh, Conductivity, geophysical data such as Bouguer and magnetic anomaly were used. Using the constructed spatial database, the relationships between minerals deposit areas and related 36 factors were identified and quantified by frequency ratio and logistic regression models which are probabilistic and statistical model. All factors were used for mapping of regional mineral potential using overlay method in GIS environment. Then, the mineral potential map was verified using existing mineral deposit area. The verification results showed 89.53% and 92.83% in frequency ratio and logistic regression models each.

The results of a pilot study into the application of an unsupervised clustering approach to the analysis of catchment-based National Geochemical Survey of Australia (NGSA) geochemical data combined with geophysical and geological data across northern Australia are documented. NGSA Mobile Metal Ion® (MMI) element concentrations and first and second order statistical summaries across catchments of geophysical data and geological data are integrated and analysed using Self-Organizing Maps (SOM). Input features that contribute significantly to the separation of catchment clusters are objectively identified and assessed.A case study of the application of SOM for assessing the spatial relationships between Au mines and mineral occurrences in catchment clusters is presented. Catchments with high mean Au code-vector concentrations are found downstream of areas known to host Au mineralization. This knowledge is used to identify upstream catchments exhibiting geophysical and geological features that indicate likely Au mineralization. The approach documented here suggests that catchment-based geochemical data and summaries of geophysical and geological data can be combined to highlight areas that potentially host previously unrecognised Au mineralization.

Lithological mapping plays a vital role in acquiring a comprehensive understanding of subsurface rocks and geological structures. Traditional lithological mapping relies heavily on manual field surveys, with the accuracy of the mapping greatly constrained by the expertise of mappers, and thus this process is commonly slow and costly. In the present study, the graph convolutional network (GCN) method was proposed for efficient and automatic lithological mapping, using various geological survey data (e.g. geochemical and geophysical data). The GCN is not limited by the spatial distribution of sampling data, and hence it can be directly applied to the integrated resampling data that do not adhere to the regular spatial distribution patterns of Euclidean space. To evaluate the potential application of the GCN method in lithological classification and mapping, a case study was conducted in the Maqin region (China). Geochemical and geophysical data were utilized as the basis for lithological classification, as they can provide valuable information on geochemical compositions and physical properties of geological bodies, respectively. The study process was primarily divided into three parts. First, basic pre-processing was conducted on the geochemical data and the geophysical data, including centred log-ratio transformation and resampling. Subsequently, the resampled points were divided into training and testing sets in the proportion of 5.5:1. In the training set, 20% of the points are randomly selected as the validation set. Ultimately, using each resampled point as a node and the integrated geochemical and geophysical data as features, a GCN model and an undirected graph were constructed based on an adjacency distance of 1 km. The graph was employed by the constructed GCN model for lithological classification. The results reveal that the majority of lithological units can be accurately classified with an overall accuracy of 86%, indicating that the GCN model exhibits good applicability in lithological classification.

The Scotia Sea is one of the tectonically most complex and least understood back-arc basins on Earth, which partly results from its remote location making the acquisition of data challenging. Here, we provide a review of current, publicly available geophysical and geological data in the Scotia Sea realm, including magnetic, Bouguer gravity anomaly, high-resolution bathymetric, heat flow and reflection seismic data and rock type data from cored and dredged samples. With this inter-disciplinary data-set, we performed an offshore geological mapping exercise that allowed us to identify lithologies in the predominantly submerged Scotia Sea domain. Cross-sections combining crustal structure and mantle tomography enabled us to address some of the still persisting geological challenges in this tectonically complex area.The data-review revealed that basalt is the dominant lithology in the Scotia Sea area, occupying most of the West and East Scotia Sea (WSS and ESS). Andesitic and more felsic lithologies are identified in the Central Scotia Sea (CSS) and the northern East Scotia Sea (ESS). Mesozoic/Palaeozoic metamorphic/sedimentary lithologies are reported from the highs along the North and South Scotia Ridges (NSR and SSR). These highs originate from a land bridge that, until the late-Mesozoic, connected the South American and Antarctic continents. Scarcely available and contradicting data prevent the age determination of several structural units surrounding and located on the Scotia plate, but our mapping exercise allowed us to confirm the presence of the early Oligocene - late Miocene Ancestral South Sandwich Arc (ASSA) in the east of the CSS, setting the minimum age of the older segment of the CSS crust to Eocene-earliest Oligocene.Three cross-sections cross-cutting the Scotia Sea reveal two high velocity zones, indicating cold mantle material. One is situated below the structural highs along the SSR, which we interpreted as remnant slab material of the ASSA and another below South Georgia and the CSS, which we interpreted as the front of the slab that currently subducts at the South Sandwich Trench (SSaT). The neutral velocity discontinuity below the WSS implies mantle conditions of a recently extinct spreading centre. The upper mantle low velocity anomaly below the CSS is interpreted as warmer toroidal flows around the slab edges of the subducting plate at the SSaT.We have demonstrated that the geological and geophysical data publicly available today allows us to create offshore geological maps in remote, inaccessible offshore domains. This is a less time-consuming, economically advantageous exercise, which re-uses existing geological and geophysical data for a new purpose. It is the most data-inclusive study there is today of the Scotia Sea region and serves as a guideline for future expeditions targeting the CSS and the structural features along the NSR to identify their age and origin. A georeferenced version of the map is provided in the supplementary material.

Investigation of the main reservoir of the Tulehu geothermal system (Indonesia) using 3-D inversion of MT data

&amp;lt;p&amp;gt;The presented study is part of an international multidisciplinary project aiming to investigate the geothermal potential of the Baia Mare volcanic province in north-western Romania. We integrate existing geological, geochemical, hydrogeological, and geophysical data into a 3D lithospheric temperature model. In addition, new seismic reflection and broadband magnetotelluric data, acquired in the study region, provide additional constraints on the crustal-scale structures possibly controlling the transport of deep heat to the surface.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The study area is located within the Neogene Inner Carpathian volcanic arc and includes the area of the recent crustal uplift between the north-eastern part of the Pannonian Basin and the Transylvanian Basin. Borehole temperature measurements showed a geothermal gradient of 45-55 &amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt;C km&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; and temperatures higher than 150 &amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt;C at depths of 3000 m, the highest values of heat flow recorded to date in Romania. The region is known for surface hot springs and hydrothermal and epithermal volcanic ore deposits.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The heterogeneous pre-Neogene basement contains metamorphic and igneous rocks deformed or emplaced during Precambrian to Paleozoic orogenic cycles and a Triassic-Paleogene sedimentary cover with a variable radioactive heat production rate. The Miocene magmatic plumbing system within the Neogene sedimentary sequence includes intrusive bodies of 1-10s of km size. Crustal hydraulic properties and associated hydrothermal systems are possibly controlled by the regional Bogdan Voda &amp;amp;#8211; Dragos Voda strike-slip faults system, which provided pathways for the Miocene volcanic emplacement and sub-volcanic intrusions.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The knowledge of deep lithospheric structure is important for the characterisation of sedimentary basins with a geothermal exploration potential. In this contribution, we present geophysical and geological data and describe the construction of a regional 3D lithospheric temperature model. The structural model includes sedimentary successions, crystalline crustal layers and lithosphere-asthenosphere boundary constrained by gravity, seismic tomography and magnetotelluric data. The temperature modelling is performed by solving 3-D steady state heat conduction equation using a finite element method. We compare the model responses with available surface heat flow and borehole temperature measurements and discuss the role of local crustal heterogeneities, transient heat transfer and fluid circulation on the thermal state of the Baia Mare region.&amp;lt;/p&amp;gt;

&amp;lt;p&amp;gt;In Afar, an active mature rift, close to break-up have been described for many decades. However, no data were provided so far to precisely constrain the long-term structure of the rift, its evolution, and the rift maturity, i.e. the documentation of ongoing break-up processes. Here, we synthetize structural, geophysical, and geochemical data that show that break-up is indeed ongoing in Central Afar.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Geological mapping and dating of volcanic units provided data to build a detailed surface cross-section, showing a dense network of continentward dipping normal faults and two main unconformities. The field cross-section allows to estimate the amount of crustal thinning and stretching (beta factor &amp;gt; 2.5 in the rift center). The crust first stretched quite uniformly during late Oligocene-early Miocene times and then thinned is a more localized manner during late Miocene times. Subsequently, during Plio-Quaternary times the volcanic Strato&amp;amp;#239;d series emplaced in the thinned area. Eventually, the present-day magmatic axes have been active for about 500 kyr in the thinned continental crust.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The crust decreases in thickness from 40 km beneath the Ethiopian plateau to about 20-25 km in Central Afar, from receiver functions (RF). New RF data and tomographic models confirm that thickness and show that a necking zone formed at depth most likely during late Miocene times (thinning phase).&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The combination of geological and geophysical data allows to attempt for balancing the cross-section. This balancing suggests that, beneath Central Afar, the crust is much thicker than it should be. This crust in excess is interpreted as representing magma intrusions and/or underplating that occurred in the course of the Cenozoic rifting.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Trace element analyses suggest that the depth of melting has strongly decreased just after the plume impingement, suggesting an early thermal erosion of the lithosphere base. Geochemical (isotopic) data show that in Central Afar most of the magma sources were in the plume head/tail since its impingement. These data also show that the recent lavas (&amp;lt; 500 kyr) were almost not contaminated by continental crustal rocks, attesting for a transitional crust beneath Afar and suggesting a recent switch from crustal thinning to dyke-related divergence.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;To sum up, we propose that (1) the Afar plume was channelized in the lithosphere, probably since late Oligocene times, (2) a late Miocene thinning event (necking) predated a Quaternary SDR-like volcanic wedge emplacement, and (3) divergence is now accommodated by magmatic accretion.&amp;lt;/p&amp;gt;

Data from the Gravity Recovery and Climate Experiment (GRACE) and outputs of the CLM4.5 model were used to estimate recharge and depletion rates for large aquifers, investigate the connectivity of an aquifer’s subbasins, and identify barriers and preferred pathways for groundwater flow within an aquifer system. The Nubian Sandstone Aquifer System and its subbasins (Dakhla, Northern Sudan Platform, and Kufra) in northeast Africa were used for demonstration purposes, and findings were tested and verified against geological, geophysical, remote sensing, geochronologic, and geochemical data. There are four major findings. (1) The average annual precipitation data over recharge areas in the southern Kufra section and the Northern Sudan Platform subbasin were estimated at 54.8 km 3 , and 32.8 km 3 , respectively, and knowing the annual extraction rates over these two areas (∼0.40 ± 0.20 km 3 ), recharge rates were estimated at 0.78 ± 0.49 km 3 /yr and 1.44 ± 0.42 km 3 /yr, respectively. (2) GRACE-derived groundwater depletion rates over the Dakhla subbasin and the Northern Kufra section were estimated at 4.44 ± 0.42 km 3 /yr and 0.48 ± 0.32 km 3 /yr, respectively. (3) The observed depletion in the southern parts of the Dakhla subbasin is apparently caused by the presence of the east-west−trending Uweinat-Aswan basement uplift, which impedes the south-to-north groundwater flow and hence reduces replenishment from recharge areas in the south. (4) A major northeast-southwest−trending shear zone (Pelusium shear system) is apparently providing a preferred groundwater flow pathway from the Kufra to the Dakhla subbasin. Our integrated approach provides a replicable and cost-effective model for better understanding of the hydrogeologic setting of large aquifers worldwide and for optimum management of these groundwater resources.

ABSTRACTA parameter‐estimation technique based on existing hydrological, geophysical, and geological data was developed to approximate transmissivity values for use in a ground‐water flow model of the Animas Valley, southwest New Mexico. Complete Bouguer gravity anomaly maps together with seismic‐refraction profiles, geologic maps, geologic, geophysical, and drillers' logs, water levels, and pumping‐test data provide insight into the transmissivity of bolson deposits throughout the basin.The transmissivity distribution was primarily based on reported pumping and specific‐capacity tests in conjunction with complete Bouguer gravity anomaly maps and well log data. Reported transmissivity values were characterized by gravity values and well log data. In grid blocks lacking pumping and specific‐capacity tests, transmissivity values were assigned based on the relationship of gravity values and well log data within the grid block to gravity values and well log data within other grid blocks for which transmissivity values are available.A two‐dimensional, finite‐difference, ground‐water flow computer code was used to evaluate the effectiveness of the parameter‐estimation technique. Although the trial‐and‐error method of calibration was employed, the actual computer time necessary for model calibration was minimal. The conceptually straightforward approach for parameter estimation utilizing existing hydrological, geophysical, and geological data provides realistic parameter estimates.

The objective of this study was to realize a three-dimensional (3-D) geological model of the deep basin structure of the Middle Durance region (of folds and faults) by integration of geological and geophysical data, and to evaluate its fault geometry and tectonic history. All of the available geophysical and geological data were compiled in three dimensions using the gOcad geomodeler. The geological and geophysical data were used to build a 3-D geological model of the Middle Durance region. The data on the 3-D geometry of fault surfaces and stratigraphic horizons and the thickness maps of the main stratigraphic units are supported by the 3-D geological model. We show that the Middle Durance Fault cannot be interpreted as a single fault plane that affected the entire Meso-Cenozoic sedimentary layers and the Paleozoic basement but as a listric segmented faulting system in sedimentary layers, rooted in Triassic evaporites and a normal block faulting system in the basement. This decoupling level in the Triassic layers reveals thin-skin deformation, formed by strong mechanical decoupling between the Mesozoic sedimentary cover and the Paleozoic basement. This study also confirms that the Provence geological structure has resulted mainly from Pyrenean deformation, which was partly reactivated by Alpine deformation. We demonstrate that the Middle Durance Fault Zone is a transfer fault that accommodates deformation of the sedimentary filling of the South-East Basin through modified fold geometry over a zone of 7 km to 8 km around the main segment of the fault zone.

When building 3D models of the subsurface, reconciling several geological and geophysical data of diverse nature, resolutions, coverage, or sensitivity, is challenging, both numerically and petrophysically. In this work, we propose a workflow for mapping selected geological features and characterise their uncertainty using a Bayesian Estimate Fusion algorithm. Different datasets such as 1D probabilistic models derived from geophysical data, drillholes and geological data are combined to produce probabilistic maps of selected geological boundaries, relying on petrophysical and geological assumptions. Leveraging large, high-quality geophysical datasets acquired in the eastern Gawler Craton in South Australia, we demonstrate the applicability of our approach with two examples: (1) we map in 3D the top of a stratigraphic unit in the cover, the Tregolana Shale, using 1D magnetotelluric (MT) and 1D Airborne Electromagnetic (AEM) probabilistic models, drill holes and surface geology; (2) we map the depth to basement using 1D probabilistic MT models, drill holes and interpreted structural information. Our results show that the different resolution, data sampling, depth of investigation and reliability of the utilised datasets can be combined in a complementary fashion, overcoming their respective limitations, to find solutions/models that satisfy all the datasets. We show that probabilistic workflows permit characterisation and reduce uncertainty when mapping the location of features of interest, but also permit the testing of geological hypotheses against other geophysical and geological data. These types of models are valuable to better characterise, interpret, and conceptualise the subsurface, enabling better exploration targeting and supporting efforts to discover new mineral deposits.

P346 THE INTEGRATED ANALYSIS OF GEOLOGICAL GEOPHYSICAL AND REMOTE SENSING DATA AT THE GOLD PROSPECTING IN WESTERN UZBEKISTAN 1 Summary In the report the technology and results of gold prospecting in the territory of Western Uzbekistan is given. At the beginning of work process perspective sites in a scale of 1:50000 were determined based on complex of geological and geophysical data. Then inside of their limits detailing was performed and zones of auriferous mineralization were determined. The technique of search is based on integrated analysis of various geological and geophysical data and high-accuracy multispectral aerophotos. Introduction 0 200 400 km

&amp;lt;p&amp;gt;We produced the first geological map of the Scotia Sea area based on the available geophysical and geological data. Combining magnetic, Bouguer gravity anomaly and high-resolution bathymetric data with geological data from dredged samples allowed us to map lithologies and structural features in this mostly submerged and complex tectonic area. This geological map allowed us to integrate a very inter-disciplinary dataset, thereby reviewing the available data and addressing some of the still persisting geological challenges and controversies in the area.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;One of the most important and persistent discussions is the nature and age of the Central Scotia Sea. We mapped this part of the Scotia Sea as basaltic-andesitic lithology partly covered by thick, oceanic sediments. This differs in lithology from the West and East Scotia Sea, which we mapped as a basaltic lithology. Based on our lithological map, its unusual thickness and the presence of the Ancestral South Sandwich Arc (ASSA, early Oligocene-late Miocene) we argue that Central Scotia Sea has an Eocene to earliest Oligocene age.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Cross-sections combining the geology, crustal structure and mantle tomography reveal high velocity anomalies and colder mantle material below the structural highs along the South Scotia Ridge (Terror Rise, Pirie Bank, Bruce Bank and Discovery Bank) and below the South Sandwich Islands. We interpreted those as the southern, stagnated part of the subducting slab of the South Sandwich Trench, following the geometry of Jane Basin and the currently active subducting slab at the South Sandwich Trench. Low velocity anomalies are observed below Drake Passage and the East Scotia Sea, which are interpreted as warmer toroidal mantle flow around the slab edges below the Chilean trench and the South Sandwich trench.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Based on our geological map and integrated cross-sections we propose a multi-phase evolution of the Scotia Sea area with Eocene or older oceanic crust for the Central Scotia Sea. A first wide-rift-phase initiated before 30 Ma in the West Scotia Ridge, Protector Basin, Dove Basin and Jane Basin either as a result of the diverging South American and Antarctic continents and/or due to subduction rollback that commenced soon after subduction initiation that eventually caused the ASSA to form. The first full spreading center developed in the West Scotia Sea, aided by the warmer toroidal mantle flow causing spreading to be abandoned in the other basins (~30 Ma). A second rift phase in the fore-arc, in between the ASSA and the South Sandwich trench (~20 Ma), initiated through a redistribution of far-field forces as a result of continuous trench retreat. The warmer toroidal mantle concentrated on the East Scotia Ridge resulting in the second spreading system (15 Ma), abandoning the West Scotia Ridge spreading system 6-10 Ma.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We show that it is possible to create a geological map in a very remote area with an extreme environment with the available geological and geophysical data. This new way of producing geological maps in the offshore domain provides a better insight into the geological history of geologically complex areas that are largely submerged.&amp;lt;/p&amp;gt;

ABSTRACTGravity surveys of the past century established that mountains have roots, seismic refraction lines shot in the second half of this century confirmed the downbulge of the Moho under the Alps, and recent reflection traverses provided new details on the behaviour of crustal layers in the deep part of the Alps. However, geophysical data are ambiguous geologically. For models of the root in terms of rock distribution to be tectonophysically acceptable, they must be the retrodeformable result of kinematic sequence that fits the geological surface data. For a cross‐section through the Swiss Alps based on refraction data and somewhat modified by the recent reflection traverses, a kinematic model compatible with large‐scale geological data may be obtained by the superposition of three Neogene phases with alternating vergence. Although Alpine collision is largely dextrally compressive in the central Alps, the N‐S component may be discussed in a cross‐section. Particularly puzzling geophysical features include a high‐velocity body in the middle crust and the disappearance of the layered foreland crust in the root. In order to account for these phenomena, it is proposed that the crustal root is interpreted as the result of complex reshuffling of middle and lower crustal masses as well as large‐scale phase transformations. The mid‐crustal highvelocity body is interpreted as a delaminated section of the lower crust of the Adria plate that was wedged into the middle crust of the Alps in the middle Miocene. The disappearance of the foreland lower crust is attributed to eclogitization attendant on the subduction of continental crust. Material balance estimates suggest that during Alpine collision large volumes of continental crust have disappeared through subduction.