Regional scale mineral exploration through joint inversion and geology differentiation based on multi-physics geoscientific data

Author(s):  
Jae Deok Kim ◽  
Jiajia Sun ◽  
Aline Melo
SEG Discovery ◽  
2000 ◽  
pp. 1-20
Author(s):  
JEREMY P. RICHARDS

ABSTRACT Large-scale crustal lineaments are recognized as corridors (up to 30 km wide) of aligned geological, structural, geomorphological, or geophysical features that are distinct from regional geological trends such as outcrop traces. They are commonly difficult to observe on the ground, the scale of the features and their interrelationships being too large to map except at a regional scale. They are therefore most easily identified from satellite imagery and geophysical (gravity, magnetic) maps. Lineaments are believed to be the surface expressions of ancient, deep-crustal or trans-lithospheric structures, which periodically have been reactivated as planes of weakness during subsequent tectonic events. These planes of weakness, and in particular their intersections, may provide high-permeability channels for ascent of deeply derived magmas and fluids. Optimum conditions for magma penetration are provided when these structures are placed under tension or transtension. In regions of subduction-related magmatism, porphyry copper and related deposits may be generated along these lineaments because the structures serve to focus the ascent of relatively evolved magmas and fluid distillates from deep-crustal magma reservoirs. However, lineament intersections can only focus such activity where a magma supply exists, and when lithospheric stress conditions permit. A comprehensive understanding of regional tectono-magmatic history is therefore required to interpret lineament maps in terms of their prospectivity for mineral exploration.


2020 ◽  
Vol 39 (10) ◽  
pp. 753-754
Author(s):  
Jiajia Sun ◽  
Daniele Colombo ◽  
Yaoguo Li ◽  
Jeffrey Shragge

Geophysicists seek to extract useful and potentially actionable information about the subsurface by interpreting various types of geophysical data together with prior geologic information. It is well recognized that reliable imaging, characterization, and monitoring of subsurface systems require integration of multiple sources of information from a multitude of geoscientific data sets. With increasing data volumes and computational power, new data types, constant development of inversion algorithms, and the advent of the big data era, Geophysics editors see multiphysics integration as an effective means of meeting some of the challenges arising from imaging subsurface systems with higher resolution and reliability as well as exploring geologically more complicated areas. To advance the field of multiphysics integration and to showcase its added value, Geophysics will introduce a new section “Multiphysics and Joint Inversion” in 2021. Submissions are accepted now.


Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 145 ◽  
Author(s):  
Mostafa Naghizadeh ◽  
David Snyder ◽  
Saeid Cheraghi ◽  
Steven Foster ◽  
Samo Cilensek ◽  
...  

The Metal Earth project acquired 927 km of deep seismic reflection profiles from August to November of 2017. Seismic data acquired in this early stage of the Metal Earth project benefited greatly from recent advances in the petroleum sector as well as those in mineral exploration. Vibroseis acquisition with receivers having a 5 Hz response (10 dB down) generated records from a sweep signal starting at 2 Hz, sweeping up to 150 Hz or 200 Hz. Not only does this broadband signal enhance reflections from the deepest to the shallowest crust, but it also helps the use of full waveform inversion (e.g., to mitigate cycle-skipping) and related techniques. Metal Earth regional-scale transects using over 5000 active sensors target mineralizing fluid pathways throughout the crust, whereas higher spatial-resolution reflection and full-waveform surveys target structures at mine camp scales. Because Metal Earth was proposed to map and compare entire Archean ore and geologically similar non-ore systems, regional sections cover the entire crust to the Moho in the Abitibi and Wabigoon greenstone belts of the Superior craton in central Canada. Where the new sections overlap with previous Lithoprobe surveys, a clear improvement in reflector detection and definition is observed. Improvements are here attributed to the increased bandwidth of the signal, better estimates of refraction and reflection velocities used in processing, and especially the pre-stack time migration of the data.


SEG Discovery ◽  
2019 ◽  
pp. 21-29
Author(s):  
Roderick Carlson

Editor’s note: The Geology and Mining series, edited by Dan Wood and Jeffrey Hedenquist, is designed to introduce early-career professionals and students to a variety of topics in mineral exploration, development, and mining, in order to provide insight into the many ways in which geoscientists contribute to the mineral industry. Abstract The role of geology in advanced mining studies, such as feasibility studies, is commonly dwarfed by the technical inputs from mining, metallurgical, and social license issues. Understanding and planning for geologic risk in the feasibility process is often overlooked for the higher-profile aspects required to establish an ore reserve. If the geologic model of a deposit cannot be reliably forecast, then there will be lower confidence in many of the modifying factors (which include mining, processing, environmental, social, governmental, and economic factors that influence the conversion of identified mineral resources into economic reserves). Understanding geologic risk requires characterization of all the chemical, physical, and spatial properties of mineralization and waste that form part of the mined material. It is essential to understand the scope of the professionals who use geoscientific data in order to assist the outcomes of the study, with the data types first identified, then collected in a comprehensive manner, and finally interpreted at the appropriate time to contribute to the outcomes of the study. If the study is not comprehensive, remedial collection of data is required at a cost to development timeline and budget; a worse scenario is that the development fails economically after it is built. Developing projects to a construction stage after a mining study typically involves international standards of assessment and verification, although the standards of geoscientific data collection differ between companies and countries. For this reason, recent efforts by international bodies such as the Committee for Mineral Reserves International Reporting Standards (CRIRSCO) are assisting many countries to work toward a standardized terminology in a feasibility study. There are many examples where the mining outcomes have not met the feasibility study forecast, with variable causes for a failure to deliver to plan; geoscientific data shortfalls often contribute significantly to these negative outcomes. Examination of case histories, knowledge of international standards for risk reporting, advances in measurement technology, and an understanding of the end users of geoscientific data will help geologists to better prepare the scope of a feasibility study for a potential mine, in order to deliver a product with lower risk related to geologic uncertainty.


Geosciences ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 262
Author(s):  
Michael S. Zhdanov ◽  
Michael Jorgensen ◽  
Leif Cox

Different geophysical methods provide information about various physical properties of rock formations and mineralization. In many cases, this information is mutually complementary. At the same time, inversion of the data for a particular survey is subject to considerable uncertainty and ambiguity as to causative body geometry and intrinsic physical property contrast. One productive approach to reducing uncertainty is to jointly invert several types of data. Non-uniqueness can also be reduced by incorporating additional information derived from available geological and/or geophysical data in the survey area to reduce the searching space for the solution. This additional information can be incorporated in the form of a joint inversion of multiphysics data. This paper presents an overview of the main ideas and principles of novel methods of joint inversion, developed over the last decade, which do not require a priori knowledge about specific empirical or statistical relationships between the different model parameters and/or their attributes. These approaches are designated as follows: (1) Gramian constraints; (2) Gramian-based structural constraints; (3) localized Gramian constraints; and (4) joint focusing constraints. We provide a short description of the mathematical foundations of each of these approaches and discuss the practical aspects of their applications in mineral exploration.


2021 ◽  
Author(s):  
Ivan Granados Chavarria ◽  
Marco Calò ◽  
Thomas Bodin ◽  
Angel Figueroa Soto

<p>Joint inversion of surfaces and teleseismic converted waves is commonly used to retrieve seismic structures beneath a seismic station. Currently, this approach is routinely applied at global and regional scale to probe the structures of the mantle and the lower-crust. However, the difficulty to retrieve reliable converted waves at high frequencies (> 1 Hz) makes challenging to apply this technique to resolve structures at shallow depths (<20 km). Here we explore the feasibility of using a trans-dimensional Bayesian scheme based on a reversible jump Markov Chains Monte Carlo method, to resolve shallow structure at local scale. We use phase and group velocity dispersion curves for Love and Rayleigh waves, from 0.5 to 10 s and tele-seismic converted waves in a distance range from 30<sup>o</sup> to 95<sup>o</sup>. We explore the ability of different approaches to retrieve high frequency converted phases that will be used in the framework of the Bayesian inversion. We present preliminary tests of the reliability of the method and applications to experimental data collected in the super-hot geothermal field of Los Humeros, México. This work is performed in the framework of the Mexican European consortium GeMex (Cooperation in Geothermal energy research Europe-Mexico, PT5.2 N: 267084 funded by CONACyT-SENER: S0019, 2015-04, and Horizon 2020, grant agreement No. 727550).</p>


Geophysics ◽  
2012 ◽  
Vol 77 (1) ◽  
pp. K1-K15 ◽  
Author(s):  
Peter G. Lelièvre ◽  
Colin G. Farquharson ◽  
Charles A. Hurich

Seismic methods continue to receive interest for use in mineral exploration due to the much higher resolution potential of seismic data compared to the techniques traditionally used, namely, gravity, magnetics, resistivity, and electromagnetics. However, the complicated geology often encountered in hard-rock exploration can make data processing and interpretation difficult. Inverting seismic data jointly with a complementary data set can help overcome these difficulties and facilitate the construction of a common earth model. We considered the joint inversion of seismic first-arrival traveltimes and gravity data to recover causative slowness and density distributions. Our joint inversion algorithm differs from previous work by (1) incorporating a large suite of measures for coupling the two physical property models, (2) slowly increasing the effect of the coupling to help avoid potential convergence issues, and (3) automatically adjusting two Tikhonov tradeoff parameters to achieve a desired fit to both data sets. The coupling measures used are both compositional and structural in nature and allow the inclusion of explicitly known or implicitly assumed empirical relationships, physical property distribution information, and cross-gradient structural coupling. For any particular exploration scenario, the combination of coupling measures used should be guided by the geologic knowledge available. We performed our inversions on unstructured grids comprised of triangular cells in 2D, or tetrahedral cells in 3D, but the joint inversion methods are equally applicable to rectilinear grids. We tested our joint inversion methodology on scenarios based on the Voisey’s Bay massive sulfide deposit in Labrador, Canada. These scenarios present a challenge to the inversion of first-arrival traveltimes and we show how joint inversion with gravity data can improve recovery of the subsurface features.


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