geophysical anomalies
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2021 ◽  
pp. 13-28
Author(s):  
Wojciech Ejsmond ◽  
Olivier Pierre Rochecouste ◽  
Taichi Kuronuma ◽  
Piotr Witkowski

Continued archaeological surveys at two sites in the Gebelein area, the Northern Necropolis and the temple complex, have contributed new data for a better understanding of the ancient remains. Geophysical anomalies detected in 2015 in the western part of the Northern Necropolis should now be interpreted most probably as tombs with mud-brick walls. Mounds of earth in the central part of the necropolis yielded numerous artifacts dating from between the Naqada I and the early Old Kingdom periods; they are likely to have been dumped from a nearby settlement site, probably the ancient town of Sumenu. Work in the temple complex was aimed at protecting the structure made of inscribed mud-bricks dating from the Twenty-first Dynasty.


2021 ◽  
Author(s):  
◽  
Om Prakash Pandey

<p>In this regional heat flow study of New Zealand temperatures have been measured in available boreholes using a specially constructed thermistor probe, and existing temperature information has been incorporated from various sources including oil prospecting boreholes. Thermal conductivity has been measured in the laboratory on 581 samples. Newly determined values of heat flow are given for 105 locations; values for the South Island are here presented for the first time. Most of the heat flow values have been grouped in eight regions based on the level of heat flow. This classification can be related to the occurrence of certain surface manifestations and geophysical anomalies, and to regional plate tectonics. High heat flow in three regions is consistent with melting conditions being reached at depths between 35km and 45km. These are the Taranaki Region, the West Coast Region and the Great South Basin. The average regional heat flow for these regions varies from 86.4 mW/m2 to 110.7 mW/m2. Much lower heat flow is obtained in the Hikurangi and Marlborough-Canterbury Regions; these may possibly be interconnected. Elsewhere the heat flow is low to normal with isolated highs. The broad distribution of heat flow in the North Island is typical for an active subduction region. Radioactive heat generation has been measured on rock types from various localities, and large variations have been found. The heat flow - heat generation relationship has been studied for 42 sites. A linear relationship is found only in the Taranaki and Hikurangi Regions. Temperature calculations show large differences in the deep-seated temperature distribution beneath New Zealand, and this has also been reflected in the distribution of "reduced heat flow". Temperature and heat flow can be correlated with upper mantle inhomogeneity. The inferred variation of radioactive heat generation with depth has been studied for areas beneath the Western Canterbury Region. A mean heat generation of 1.56 plus-minus .07 muW/m3 has been found in a sequence which has been inferred to occur between 17km and 30km in depth under the region; this is very much higher than the usually adopted values for the lower crust. Normal heat flow observed in the Western Cook Strait Region, and the existence of good seismic wave transmission beneath the same region, can be attributed to crustal and lithospheric thickening. The relevance of present study to petroleum occurrences has been examined and it is found that in areas of proven hydrocarbon potential the heat flow is high.</p>


2021 ◽  
Author(s):  
◽  
Om Prakash Pandey

<p>In this regional heat flow study of New Zealand temperatures have been measured in available boreholes using a specially constructed thermistor probe, and existing temperature information has been incorporated from various sources including oil prospecting boreholes. Thermal conductivity has been measured in the laboratory on 581 samples. Newly determined values of heat flow are given for 105 locations; values for the South Island are here presented for the first time. Most of the heat flow values have been grouped in eight regions based on the level of heat flow. This classification can be related to the occurrence of certain surface manifestations and geophysical anomalies, and to regional plate tectonics. High heat flow in three regions is consistent with melting conditions being reached at depths between 35km and 45km. These are the Taranaki Region, the West Coast Region and the Great South Basin. The average regional heat flow for these regions varies from 86.4 mW/m2 to 110.7 mW/m2. Much lower heat flow is obtained in the Hikurangi and Marlborough-Canterbury Regions; these may possibly be interconnected. Elsewhere the heat flow is low to normal with isolated highs. The broad distribution of heat flow in the North Island is typical for an active subduction region. Radioactive heat generation has been measured on rock types from various localities, and large variations have been found. The heat flow - heat generation relationship has been studied for 42 sites. A linear relationship is found only in the Taranaki and Hikurangi Regions. Temperature calculations show large differences in the deep-seated temperature distribution beneath New Zealand, and this has also been reflected in the distribution of "reduced heat flow". Temperature and heat flow can be correlated with upper mantle inhomogeneity. The inferred variation of radioactive heat generation with depth has been studied for areas beneath the Western Canterbury Region. A mean heat generation of 1.56 plus-minus .07 muW/m3 has been found in a sequence which has been inferred to occur between 17km and 30km in depth under the region; this is very much higher than the usually adopted values for the lower crust. Normal heat flow observed in the Western Cook Strait Region, and the existence of good seismic wave transmission beneath the same region, can be attributed to crustal and lithospheric thickening. The relevance of present study to petroleum occurrences has been examined and it is found that in areas of proven hydrocarbon potential the heat flow is high.</p>


2021 ◽  
Vol 48 (Spl.1) ◽  
Author(s):  
Manuel Puentes ◽  
Adriana Robayo ◽  
Ismael Moyano ◽  
Eduardo Henrique ◽  
Marcela Lara ◽  
...  

The Map of Geophysical Anomalies of Colombia for mineral resources, MAGC 2020 version compiles the geophysical information acquired, processed and interpreted by the Servicio Geológico Colombiano (SGC) since 2013. This information was collected via airborne platforms (aircrafts) using magnetometry and gamma spectrometry. This version covers approximately 547 960 km2 of the national territory in the Andean (North and Central), Eastern (Eastern Plains and Amazon) and Caribbean zones (Perijá mountain range). This information consists of 17 blocks of geoscientific interest, covered by flight lines separated by 500 and 1000m, for a total of more than 907 566 linear km of airborne information, acquired at a nominal altitude of 100 m above the ground, with a sampling resolution that was not previously available at this scale and coverage. This document presents the methodology for compiling, processing and representing the thematic coverage included in MAGC 2020: Map of Total field magnetic anomaly (TFMA), Map of the analytic signal (AS) and radiometric ternary map of the distribution of the relative concentrations of uranium, thorium and potassium. Furthermore, the work identifies 1079 magnetometric anomalies of interest, which were subsequently analyzed and modeled in the Map of magnetic sources modeled from magnetization vector inversion, which contains a total of 1297 magnetic bodies interpreted from these anomalies. Integration of available geological and metallogenic information with each of these bodies allow the suggestion of possible geological sources and possible exploration targets. The objectives of this study were to generate and integrate geophysical information to identify new areas of interest with regards to potential mineral resources, and to generate new geoscientific knowledge about Colombia for land-use planning.


Author(s):  
N. A. Kasyanova

Background. The geodynamic approach is effectively used in regional forecasting and prospecting works. However, its application for local forecasting and prospecting for solid minerals is limited and sometimes impossible. One of the key problems of local forecasting and prospecting for minerals (solid, liquid, gaseous) is the presence of non-standard (flickering) geophysical anomalies, which complicates the interpretation of the results of geophysical surveys performed at different times at different stages of geological exploration. The article is devoted to clarifying the possibility of using geodynamic research in local forecasting and prospecting for solid minerals on the basis of attracting the latest scientific knowledge from the field of studying the spatio-temporal patterns of the development of modern geodynamic processes and their influence on the Earth’s geophysical fields. Aim. To increase the reliability of interpreting the results of geophysical surveys performed for local forecasting and prospecting for solid minerals.Materials and methods. The research was carried out on the basis of a comprehensive analysis of literature data, fund materials and the results of many years of the author’s own research in the fields of modern geodynamics and prospecting and exploration geodynamics. The initial data were based on the monitoring data of various Earth’s geophysical fields (deformation, seismic, and surface magnetic).Results. A geodynamic reason for the appearance of flickering anomalies in the Earth’s geophysical fields (in particular, magnetic) has been established, and a mechanism for their formation under the influence of modern geodynamic processes has been proposed. The possibility of using the geodynamic approach in the prospecting for solid minerals has been expanded, and ways to increasing the efficiency of local searches have been proposed.Conclusions. The research demonstrates the possibility of using geodynamic studies in local prospecting for solid minerals, which helps to increase the reliability of the results of interpretation of geophysical survey data, and, as a result, to reduce the overall financial and time costs involved with searching for mineral deposits.


2021 ◽  
Vol 43 (4) ◽  
pp. 176-198
Author(s):  
V.T. Filatova

The current article presents stratified data on physical properties of rocks and ores from the Monchegorsk ore area (Kola region). The constructed petrodensity and petromagnetic maps reflect peculiar features of changes in petrophysical parameters of both Paleoproterozoic intrusive rocks and host rocks at the Archean basement of the area. To assess the complementarity degree of physical properties of the rocks and geophysical fields, we additionally analyzed the structure of geophysical anomalies (Δg, ΔZ) in the study area. It allowed constructing a distribution scheme for geophysical heterogeneity in the area and assessing their nature. The conducted studies showed that nickel-bearing and potentially nickel-bearing intrusions in the Monchegorsk ore area were highly dense, but composed of weakly magnetic rocks. Layering of the gabbro-labradorite massif of the Main Ridge is reflected in petrophysical parameters, i. e. endocontact gabbro and gabbronorite show an increased density and magnetic susceptibility compared to leucocratic gabbro and labradorite in the core of the intrusion. Thus, petrophysical data indicate a general increase in the basicity of the rocks towards the bottom of the intrusion. The discrepancy between intense geophysical anomalies and physical parameters of near-surface rocks of the block adjacent to the gabbro-labradorite massif of the Main Ridge in the southeast was revealed. This fact indicates a layer of dense rocks under the supracrustal basement rocks (a complex of gneisses and amphibolized volcanic-sedimentary rocks) and rocks of the Imandra-Varzuga structure. This layer can be composed of potentially nickel-bearing rocks of the Imandra complex, including intrusions of the clinopyroxene-wehrlite formation series exposed in some areas. According to the configuration pattern of the identified axes of local magnetic anomalies, the Archean blocks are considered isolated areas given the uniform pattern they create, i. e. Belomorian — isometric structures, Kola — linearly extended. Therefore, during transformation of the structural plan in the Paleoproterozoic, the Archean blocks gave differentiated responses to the emerging stress-strain state of the environment and were subject to heterogeneous deformations. The performed work, including integrated results of petrophysical studies with the analysis of the structure of geophysical anomalies in the ore region, is relevant in substantiating a strategy for prospecting for new ore occurrences and patterns of their localization, as well as for developing criteria for predicting industrial ores in the region. At the same time, the studies carried out make it possible to answer questions related to the reconstruction of the geodynamic settings that took place during the formation of the region’s crust.


Geosciences ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 382 ◽  
Author(s):  
Armin Schmidt ◽  
Michel Dabas ◽  
Apostolos Sarris

For the interpretation of archaeological geophysical data as archaeological features, it is essential that the recorded anomalies can be clearly delineated and analyzed, and therefore, care has been taken to obtain the best possible data. However, as with all measurements, data are degraded by unwanted components, or noise. This review clarifies the terminology, discusses the four major sources of noise (instrument, use of instrument, external, soil), and demonstrates how it can be characterized using geostatistical and wavenumber methods. It is important to recognize that even with improved instruments, some noise sources, like soil noise, may persist and that degraded data may be the result of unexpected sources, for example, global positioning system synchronization problems. Suggestions for the evaluation and recording of noise levels are provided to allow estimation of the limit of detection for archaeological geophysical anomalies.


Author(s):  
Vincent Gaffney ◽  
Eamonn Baldwin ◽  
Martin Bates ◽  
C. Richard Bates ◽  
Christopher Gaffney ◽  
...  

A series of massive geophysical anomalies, located south of the Durrington Walls henge monument, were identified during fluxgate gradiometer survey undertaken by the Stonehenge Hidden Landscapes Project (SHLP). Initially interpreted as dewponds, these data have been re-evaluated, along with information on similar features revealed by archaeological contractors undertaking survey and excavation to the north of the Durrington Walls henge. Analysis of the available data identified a total of 20 comparable features, which align within a series of arcs adjacent to Durrington Walls. Further geophysical survey, supported by mechanical coring, was undertaken on several geophysical anomalies to assess their nature, and to provide dating and environmental evidence. The results of fieldwork demonstrate that some of these features, at least, were massive, circular pits with a surface diameter of 20m or more and a depth of at least 5m. Struck flint and bone were recovered from primary silts and radiocarbon dating indicates a Late Neolithic date for the lower silts of one pit. The degree of similarity across the 20 features identified suggests that they could have formed part of a circuit of large pits around Durrington Walls, and this may also have incorporated the recently discovered Larkhill causewayed enclosure. The diameter of the circuit of pits exceeds 2km and there is some evidence that an intermittent, inner post alignment may have existed within the circuit of pits. One pit may provide evidence for a recut; suggesting that some of these features could have been maintained through to the Middle Bronze Age. Together, these features represent a unique group of features related to the henge at Durrington Walls, executed at a scale not previously recorded.


2020 ◽  
Author(s):  
Tamara Litvinova ◽  
Дмитрий Кашик ◽  
Сергей Тихомиров

&lt;p&gt;Please insert your abstract HTML here.&lt;/p&gt;&lt;p&gt;The energy supply of geodynamic processes is one of the most important factors in the evolution of the planet earth system.The continuity and relatively stable regime of the planetary dipole magnetic field of the Earth is due, first of all, to the constant level of rotation energy continuously generated by the Earth during its rotation around its axis. In the mantle, asthenosphere, and the earth's crust, the determining energy factor is the density inhomogeneity of matter.&lt;/p&gt;&lt;p&gt;The Earth&amp;#8217;s magnetic field, which is 99% generated by its internal sources, responds to phase transitions, which are the basis of the processes of self-organization of the planet Earth system.&lt;/p&gt;&lt;p&gt;The report presents ideas about energy sources, mechanisms and patterns of formation, transformation and replenishment of its reserves will significantly increase the reliability of the interpretation of cartographic information about structural and geophysical anomalies and related mineralogenesis processes.&lt;/p&gt;


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