Disseminated Gold–Sulfide Mineralization in Metasomatites of the Khangalas Deposit, Yana–Kolyma Metallogenic Belt (Northeast Russia): Analysis of the Texture, Geochemistry, and S Isotopic Composition of Pyrite and Arsenopyrite

Abstract

At the orogenic gold deposits of the Yana–Kolyma metallogenic belt (northeast Russia) both Au–quartz-sulfide mineralization with native gold and disseminated sulfide mineralization with invisible Au developed. The textural and mineralogical-geochemical features, isotope-geochemical characteristics of gold-bearing sulfides from proximal metasomatites, and possible forms of Au occurrence in pyrite and arsenopyrite have been studied using electron microprobe, atomic absorption, LA-ICP-MS trace element, isotope analysis, and computed microtomography. Four generations of pyrite (Py1, diagenetic; Py2, metamorphic; Py3, metasomatic; Py4, veined) and two generations of arsenopyrite (Apy1, metasomatic; Apy2, veined) have been identified at the Khangalas deposit. In the proximal metasomatites, the most common are Py3 and Apy1. Studying their chemical composition makes it possible to identify the features of the distribution patterns of typochemical trace elements in pyrite and arsenopyrite, and to establish the nature of the relationship between Au and these elements. In Py3 and Apy1, structurally bound (solid solution) Au+ prevails, isomorphically entering the crystal lattice or its defects. Isotope characteristics of hydrothermal sulfides (d34S = –2.0 to –0.6‰) indicate that mantle/magmatic sulfur was involved in the formation of the deposit, though the participation of sulfur from the host rocks of the Verkhoyansk clastic complex cannot be ruled out. The Khangalas deposit has much in common with other gold deposits of the Yana–Kolyma metallogenic belt, and from this point of view, the results obtained will help to better reveal their gold potential and understand their origin.

Geology, fluid inclusions, mineral and (S-O) isotope chemistry of the Badran orogenic Au deposit, Yana-Kolyma belt, eastern Siberia: implications for ore genesis

“…The values of δ 34 S close to zero are characteristic of mantle or mantle-derived sources. The average isotopic composition of sulfur pyrite and arsenopyrite from alterations and ore veins of the Badran deposit is close to 0‰ (Figure 10A) and is consistent with the data obtained from other OGD of the western part of the YKMB (Fridovsky et al, 2013;Fridovsky et al, 2014;Gamyanin et al, 2018;Kudrin et al, 2021;.…”

“…The analyses of minerals were performed at the Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences (RAS), Yakutsk, Russia following the procedure of Kudrin et al (2021). The qualitative chemical and mineral compositions of the samples were studied with the use of a JEOL JSM-6480LV scanning electron microscope (SEM) equipped with an Energy 350 Oxford energy dispersive spectrometer (acceleration voltage was 20 kV, current through the sample was 1 nA, beam diameter was 1 µm).…”

“…Sulfur аnd oxygen isotope data provide an opportunity to gain useful information about possible sources of metals and ore fluids (Wilkinson, 2001). Studies of the isotopic composition of sulfur pyrite (δ 34 S from −0.7 to +2.1‰) and arsenopyrite (δ 34 S from −1.1 to +2.4‰) of the Badran deposit have shown that δ 34 S are close to sulfides from gold-quartz veins of orogenic deposits in the western part of the YKMB (arsenopyrite-from −2.1 to +2.4‰, pyrite-from −6.6 to +5.4‰ (Gamyanin et al, 2018;Kudrin et al, 2021; and are characterized by a smaller range of variations than δ 34 S in pyrite from quartz veins and alterations (mean +4.0‰) of the Upper-Kolyma gold-bearing area (Tyukova and Voroshin, 2008). Similar isotopic composition of sulfur arsenopyrite and pyrite of orogenic OGDs of the western part of the YKMB and disseminated mineralization from ore alterations of the Badran deposit indicates their formation during a single isotope equilibrium evolving hydrothermal event under conditions of phase separation of ore-forming fluids.…”

Metallogenic Mechanism of Carlin-Type Gold Deposit in Zhen’an-Xunyang Basin, in the South Qinling of China: Constraints of In Situ Trace Elements and S Isotopes from Newly Discovered Wangzhuang Gold Deposit

“…Gold is predominantly isomorphic in pyrite with conductivity (Ni/Co > 1), and Co-rich pyrite is not gold-bearing (Figure 11). The Co/Ni ratio reflects the genesis of pyrite and arsenopyrite [42][43][44][45]. In the studied samples, Co/Ni varied over a narrow range (0.1-4.5), and in 80% of analyses, 10.0 > Co/Ni > 0.1, which is typical for hydrothermal pyrite (Figure 12A) [46].…”