Titanium geophysics: The application of induced polarization to sea‐floor mineral exploration

Geophysics ◽  
1988 ◽  
Vol 53 (3) ◽  
pp. 386-401 ◽  
Author(s):  
Jeffrey C. Wynn

Titanium is abundant in the Earth's crust, but it can be economically extracted from only a limited group of minerals, principally rutile [Formula: see text] and ilmenite [Formula: see text], both found mainly in fossil beach‐complex placer deposits. Both minerals have only a weak magnetic susceptibility, insufficient to permit correlation between magnetic surveys and known titanium‐rich deposits. However, ilmenite shows an unusually strong induced‐polarization (IP) response, whereas the IP response of rutile is relatively weak. IP spectral signatures for ilmenite acquired in laboratory and field settings are also distinctly different from those of other polarizing materials, for instance pyrite. A nonfloating, towed‐streamer IP system was designed and deployed in surveys off the coasts of Virginia and Georgia. When the cable lies on the sea floor, calculations indicate that only about 8 percent of the injected current actually finds its way into the underlying sediment. Partly because of this high transmitted‐current to injected‐current ratio, a stationary‐streamer IP noise envelope of about 2–4 milliradians (mrad) phase shift and a towed‐streamer noise envelope of 4–6 mrad were measured. Two surveys were undertaken, one of which covered about 30 traverse km of the Atlantic continental shelf (ACS) and crossed two vibracore sites where geologic control could be obtained. Many IP anomalies were observed, with some ranging as high as 20+ mrad; about one‐third of the shallow bathymetric lows (probable paleochannels) showed anomalous IP results. Modeling suggests that these anomalies may have been caused by significant heavy‐mineral placer bodies containing as much as 20 percent ilmenite. Identification of an anomaly in towed‐streamer (conventional IP) mode data will probably be posibble only if the deposit contains more than 1 to 2 weight percentage of ilmenite. Attempts to use the spectral IP method to identify ilmenite directly with the marine IP streamer in a stationary sampling mode gave equivocal results. Although the spectral IP method appears to work well on land, in the marine application the ilmenite was present in only small quantities at the vibracore sites investigated, and the resulting weak signal was partially masked by the noise present in the IP measurement. To make spectral measurements, the streamer must be positioned accurately over a polarizing source. This task is difficult, because the deposits tend to be made up of numerous discrete, kilometer‐long bodies, perhaps no more than 50 m wide and usually only 5 to 15 m thick. Such deposits cannot be adequately tested by a vibracore survey designed to sample every 300 or 1000 m, even if the survey is augmented with a high‐resolution seismic profile. This work suggests that the large IP response of ilmenite may permit rough quantification of sea‐floor placer mineral sources from a shipborne platform while the ship is in motion. Polarizing mineral species might even be identified by using spectral IP measurements. Applications of the technology to identifying other marine mineral deposits, such as smokers at ocean‐floor spreading centers and cobalt‐rich manganese crusts, are logical extensions of this research.

2020 ◽  
Vol 168 ◽  
pp. 00002
Author(s):  
Mosaad Ali ◽  
Shulin Sun ◽  
Wei Qian ◽  
Abdou Dodo Bohari ◽  
Dusabemariya Claire ◽  
...  

Mineral exploration in the Canadian shield is a major challenge nowadays. This is because of the thick overburden cover and complex geology. Borehole tomography using resistivity and induced polarization (BHDCIP) method has a big advantage here due to that the data is acquired underneath the cover and data quality, in general, is superior to that acquired at the surface. BHDCIP provides good resistivity and chargeability data, which can identify mineralization easily. In this study, the BHDCIP survey with high-resolution data was carried out to identify mineralization zones in the McCreedy West zone, north-western Sudbury, Ontario, Canada. Two and three-dimensional (2-D and 3-D) inversion results of three boreholes clearly revealed the mineralization zones and that harmonised with previous geological studies in the study area. The BHDCIP method provided insight and developed an informative subsurface map to identify the mineralization zones, thus proving it as a beneficial tool used for mineral exploration in complex geology with a minimal data survey and an irregular geometrical distribution.


Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. E213-E225 ◽  
Author(s):  
Gianluca Fiandaca ◽  
Esben Auken ◽  
Anders Vest Christiansen ◽  
Aurélie Gazoty

Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use of time-domain-induced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function, to reconstruct the distribution of the Cole-Cole parameters of the earth. The accurate modeling of the transmitter waveform had a strong influence on the forward response, and we showed that the difference between a solution using a step response and a solution using the accurate modeling often is above 100%. Furthermore, the presence of low-pass filters in time-domain-induced polarization instruments affects the early times of the acquired decays (typically up to 100 ms) and has to be modeled in the forward response to avoid significant loss of resolution. The developed forward code has been implemented in a 1D laterally constrained inversion algorithm that extracts the spectral content of the induced polarization phenomenon in terms of the Cole-Cole parameters. Synthetic examples and field examples from Denmark showed a significant improvement in the resolution of the parameters that control the induced polarization response when compared to traditional integral chargeability inversion. The quality of the inversion results has been assessed by a complete uncertainty analysis of the model parameters; furthermore, borehole information confirm the outcomes of the field interpretations. With this new accurate code in situ time-domain-induced polarization measurements give access to new applications in environmental and hydrogeophysical investigations, e.g., accurate landfill delineation or on the relation between Cole-Cole and hydraulic parameters.


2019 ◽  
Vol 16 (2) ◽  
Author(s):  
Ir. Udaya Kamiludin

Secara regional daerah Bangka merupakan bagian dari Jalur Granit Utama Pembawa Timah.  Daratan nya ditandai oleh intrusi Granit Klabat yang merupakan batuan penting sumber endapan plaser. Untuk mengetahui lembah purba  maka dilakukan perekaman seismik saluran tunggal. Daerah penelitian secara administratif merupakan bagian dari wilayah Kabupaten Bangka Tengah, Propinsi Bangka Belitung. Perairan  Tanjung Berikat dan sekitarnya dicirikan oleh kelerengan dasar laut rata-curam dengan  kedalaman terukur antara 0-45 meter. Interpretasi seismik saluran tunggal menunjukkan stratigrafi seismik dari muda ke tua yaitu Runtunan A, Runtunan B, intrusi, dan Runtunan C sebagai dasar akustik. Ketebalan sedimen Runtunan A antara  5-30 meter dari  permukaan dasar laut. Lembah purba memanjang cukup lebar dan dalam pada Runtunan B yang diduga sebagai fasies pengisian lembah berupa onlap fill.  Fasies ini memiliki internal reflektor bebas pantulan-kaotik yang ditafsirkan sebagai wadah mineral plaser dan mineral ikutan pembawa  unsur tanah jarang. Endapan plaser diperkirakan merupakan  hasil pengerjaan ulang batuan granitoid.Kata Kunci : Dasar laut, runtunan stratigrafi, lembah/alur Purba, endapan plaser, dan Perairan Tanjung Berikat dan Sekitarnya, Bangka-Belitung. Geologically regional, the Bangka area is part of the Main Tin Belt Granite. The mainland of the study area is characterized by Klabat Granite intrusion which is an important rock source of placer deposits. To find out the placer availability of deposits on Paleo channel it was carried out for the recording of single channel seismic data. The study area is administratively part of the area of Central Bangka, Bangka-Belitung Province. Tanjung Berikat waters and its vicinity are characterized by the slope of the flat sea floor to steep with a measured depth of 0-45 meters. Seismic interpretation shows seismic stratigraphic from young to old consisting of sequence A, sequence B, Intrusion, and sequence C as acoustic basement. Sediment thickness of sequence A between 5-30 meters from seafloor surface sediment. Paleo channel with an elongated shape that is wide enough and deep in sequence B is interpreted as a channel filling facies in the form of onlap fill. This facies is characterized by the free to chaotic reflector configuration which is interpreted as a place for mineral placer and accessory minerals which contain rare earth elements. The availability of placer deposits is interpreted as the result of reworking of granitoid source rock.Keywords: Sea floor, stratigraphic seismic, Paleo channel, placer deposits, and Tanjung Berikat waters and surrounding, Bangka-Belitung.


1986 ◽  
Vol 23 (11) ◽  
pp. 1662-1672 ◽  
Author(s):  
L. Giusti

The morphology of a large number of gold grains from stream sediments of the North Saskatchewan River and the Athabasca River was studied, together with the partitioning of the placer gold between various size fractions.Two major morphological varieties of gold were observed: (1) flaky, scaly gold, with folded and hammered edges, and with crystals or crystal faces still visible on the surface; and (2) "sandwiched," droplike particles, sometimes toroidal. About 5% of both types of gold were found to be coated with "new," secondary gold.The size of the majority of the gold grains studied varies between 0.500 and 0.010 mm. The most frequent size range in the North Saskatchewan River is 0.125–0.250 mm, whereas in the Athabasca River it is 0.063–0.125 mm. An important fraction of the gold from both rivers is smaller than 0.063 mm.The average Corey shape factor (CSF) of the gravity-recovered gold increases as the particle size decreases, whereas the gold grains lost to the tailings indicate very low average shape factors (i.e., high degree of flattening). This apparent increase in CSF for the smallest fractions recovered when using mechanical techniques is due to the fact that the flaky gold particles are more difficult to recover than the more spherical ones. Moreover, the presence of a gold-rich rim on all the gold grains increases their hydrophobicity.The sampling procedure to be adopted in Alberta and, more generally, in glaciated terrains is discussed. In particular, the use of the −63 μm fraction for routine sampling of stream sediments is suggested.


1989 ◽  
Vol 26 (4) ◽  
pp. 536-550 ◽  
Author(s):  
Raymond N. Yong ◽  
Edward J. Hoppe

Preliminary experiments indicate the feasibility of constructing for field use a contaminant-detection instrumentation based on dielectric measurements. This study applies the technique of time-domain reflectometry to assess characteristic "signatures" of some selected contaminants and soil–contaminant mixtures. The results imply that a proper differentiation between various signatures can be attained, allowing an assessment in regard to soil–contaminant status. The proposed technique is similar in principle to the induced-polarization method applied in mineral exploration. Key words: electric polarization, contaminant transport, dielectrics, induced polarization, nonpolar liquids, time-domain reflectometry, relaxation, contaminant–soil interaction.


2021 ◽  
Vol 12 (3S) ◽  
pp. 731-747
Author(s):  
V. A. Kulikov ◽  
A. G. Yakovlev ◽  
V. A. Polikarpova

Electrical geophysical prospecting methods are widely used at different stages of geological exploration. In the last two decades, new computer technologies and satellite navigation systems were successfully introduced in the geophysical industry. As a result, exploration technologies have improved, and new geophysical methods have been developed, such as electrical resistivity tomography (ERT) and spectral induced polarization (SIP) methods. An important role in ore geophysics is played by magnetotelluric (MT) methods. In this article, we focus on the issues of methodology and interpretation of electrical prospecting data for solving ore exploration problems. Special attention is paid to the induced polarization (IP) method that is most widely used in mineral exploration and mining industry as one of the most important and most dynamically developing techniques of ore geophysics. In addition, the issues of correct choices of survey scales and the use of automatic 2D and 3D inversion programs are considered.


2018 ◽  
Vol 36 (3) ◽  
pp. 1
Author(s):  
Taíla Crístia Souza Sant’Ana ◽  
Edson Emanoel Starteri Sampaio

ABSTRACT. The induced polarization characteristic is to provide geophysical and geological information via geoelectric parameters, making possible mineral discrimination in the scope of mineral exploration. Although represents one of the main noises in measurements of this method, electromagnetic coupling between current and potential electrodes also contributes to the understanding of the geological scenario. Thus, the most appropriate way to deal with such data is an integrated study of these two phenomena, taking into account their particularities. Forward modelling and Gauss-Newton inversion of the mutual impedance in the frequency domain provide the analysis of the complex apparent resistivity considering both spectral induced polarization and electromagnetic coupling for homogeneous and one-dimensional, non-polarizable and polarizable Earth models. Besides synthetic data, this new approach was applied to data from the Copper District of Vale do Curaçá, Bahia, Brazil. The results reveal the ability of the method to distinguish between induction, dominant at the highest frequencies, and induced polarization, which varies with depth and frequency. It also may constitute a basis for mineral discrimination with the analysis of analogous circuit parameters, a fundamental tool in the search for metallic targets in mineral exploration.Keywords: Forward Modelling, Geophysical Inversion, Electromagnetic Method, Mineral Exploration.RESUMO. A polarização induzida espectral se destaca por fornecer diversas informações geofísico-geológicas através dos parâmetros geoelétricos, viabilizando a discriminação mineral no âmbito da exploração mineral. Embora constitua um dos principais ruídos nas medidas desse método, o acoplamento eletromagnético entre eletrodos de corrente e potencial também auxilia na compreensão do cenário geológico. Dessa forma, a maneira mais adequada de lidar com tais dados espectrais é o estudo integrado desses dois fenômenos, levando em conta suas particularidades. A modelagem direta e a inversão Gauss-Newton da impedância elétrica mútua no domínio da frequência proporcionam a análise da resistividade complexa aparente considerando tanto a polarização induzida espectral como o acoplamento eletromagnético para modelos de terra homogênea e uni-dimensional, polarizável e não-polarizável. Além do dado sintético, essa nova abordagem foi aplicada a dados reais do Distrito Cuprífero do Vale do Curaçá, Bahia, Brasil. Os resultados revelam a capacidade do método em distinguir o efeito indutivo, dominante nas mais altas frequências, e a variação da polarização induzida com a profundidade e frequência. Isso contitui um estudo base para a discriminação mineral por meio da análise de parâmetros de circuitos análogos, uma ferramenta fundamental na investigação de alvos em exploração mineral.Palavras-chave: Modelagem direta, Inversão Geofísica, Método Eletromagnético, Exploração Mineral. 1Universidade


2016 ◽  
Vol 27 (1) ◽  
pp. 27 ◽  
Author(s):  
Ediar Usman ◽  
Priatin Hadi Widjaja

The study area is located at Masela Block and its surrounding, Moluccas Province. Result of the deep sea measurement and global data conversion provide description of three dimensions around the track lines area. This result is overlay with seismic data, that can give morphotectonic implication between Asian and Australian Plates. Track lines of MGI-2010-MSL-1, 2 and 3 show that the profile of the sea floor, form the high morphology which represents the volcanic islands. It forms west – east direction of fold-thrust belt non-volcanic outer Banda arc. The southern part trench of the Australian Continent reflected the platform system and undulation morphology. The sea floor profile ( VE 1:5 ) show that the slope profile ranges between 0º and 8º. Furthermore, the morphology of the sea floor can be classified as a relatively flat slope. Due to this condition, this area may be used for gas pipe laying along 146 km distance, between the Well of Abadi 1 at the Masela Block and Selaru Island at south Tanimbar Islands. Keywords: sea depth, sea floor morphology, seismic profile, tectonic, Masela Block Daerah penelitian terletak di Blok Masela dan sekitarnya, Provinsi Maluku. Hasil pengukuran kedalaman laut dan konversi data global diperoleh gambaran tiga dimensi di sekitar jalur lintasan. Hasil ini kemudian ditumpangtindihkan dengan data seismik, sehingga dapat memberikan gambaran morfologi dan implikasi tektonik antara Lempeng Asia dan Australia. Pada Lintasan MGI-2010-MSL-1, 2 dan 3, menunjukkan profil kedalaman dasar laut membentuk morfologi tinggian yang mewakili pulau-pulau vulkanik. Kondisi ini membentuk suatu jalur punggungan lipatan sesar naik non vulkanik Busur Luar Banda berarah barat – timur. Di bagian selatan palung, mewakili Benua Australia; menunjukkan suatu sistem paparan dan morfologi undulasi Penampang dasar laut (VE 1 : 5) memperlihatkan bahwa kemiringan lereng berkisar antara 0º dan 8º. Selanjutnya morfologi dasar laut ini dapat diklasifikasikan sebagai lereng yang relative landai. Berdasarkan kondisi ini daerah ini kemungkinan dapat digunakan untuk peletakan pipa gas sepanjang 146 km, antara Sumur Abadi 1 di Blok Marsela dan Pulau Selaru di sebelah selatan Pulau Tanimbar. Kata kunci: kedalaman laut, morfologi dasar laut, enampang seismik, tektonik, Blok Masela


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