Geophysical prospecting for epithermal gold deposits (a case study from the Maletoivayam gold ore field, Kamchatka Peninsula)

Abstract

Research subject. The high-sulfidation (HS-type) epithermal gold deposits of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula. Materials and methods. The paper presents the results of geophysical and petrophysical studies carried out by “NPP VIRG-Rudgeofizika” (2016–2017 years) in the central part of the Maletoyvayam ore field hosting HS-type gold deposits. Results. The presented case study shows the potential of geophysical prospecting for HS-type epithermal gold deposits located within altered rock areas. On the basis of the conducted magnetic surveys, fragments of a ring structure broken by faults and the hydrothermally altered bodies within the Neogene volcanogenic-sedimentary sequence of the andesite composition were identified. Using the 3D inversion of magnetic data, the shape, size and structure of the hydrothermally altered bodies were estimated. The electrical survey data allowed the hydrothermally altered areas to be differentiated in terms of composition. As a result, zoning of hydrothermally altered areas was conducted, and ore-bearing sites and gold-bearing bodies of monoquartzites in the plan and cross-section were determined. Conclusions. Geophysical techniques for prospecting HS-type epithermal gold deposits are effective in distinguishing important gold-related features within the altered zone thereby facilitating identification of specific drill targets.

Conversion of Induced Polarization Data and Their Uncertainty from Time Domain to Frequency Domain Using Debye Decomposition

“…With respect to the possible exploration of deposits in the MOF, the described region can be classified as a promising area for potential copper mining. For further information on prospective areas in the MOF deduced from geophysical measurements at the study site, we refer the reader to Gurin [43]. Although the frequency dependence of the magnitude was negligible, the frequency dependence of the phase can be clearly seen from the comparison of the inversion results at 1 Hz and 20 Hz, as displayed in Figure 14.…”

“…The MOF includes three gold objects considered small HS (high sulfidation)-type gold deposits (Yugo-Zapadnoye, Gaching, and Yubileinoye), several gold anomalies superimposed with copper-arsenic sulfosalt mineralization, and copper anomalies [41,42]. Most of the discovered ore bodies are of high chargeability (e.g., [43]). The MOF features massifs of secondary quartzites with pronounced horizontal zonality, which are typical for HS-type deposits.…”

“…Geoelectric measurements have been complemented by information from other geophysical methods, such as geomagnetic measurements, and geological surveys. Gurin [43] presented the results and interpretations of multiple geophysical and petrophysical surveys carried out between 2016 and 2017 in the central part of the MOF. The IP characteristics of the field site have been previously analyzed (e.g., [44]).…”