Platinum-Group Minerals From the Olkhovaya-1 Placers Related to the Karaginsky Ophiolite Complex, Kamchatskiy Mys Peninsula, Russia

Abstract

Mineral assemblages from the Olkhovaya-1 River placers, in Kamchatka, Far-Eastern Russia, provide genetic information on their evolution. The minerals are dominated by Os-Ir-Ru alloys (80%), consisting of all possible mineral species, and Pt-Fe alloys consisting of native platinum, Fe-rich platinum and isoferroplatinum. The following features of the mineral assemblage are characteristic of mineralization associated with an ophiolitic complex: (1) in the Os-Ru-Ir diagram, the compositions of the hexagonal alloy form a ruthenium trend; (2) there are two typical equilibrium magmatic parageneses of alloys: early osmiumiridium, and later isoferroplatinum-ruthenium, which both are associated with laurite and the solid solution laurite-irarsite (Ru,Ir) (S,As) 2 . The cooperite, sperrylite and Pd minerals formed at the postmagmatic stage. Tetraferroplatinum-tulameenite, replacing the Pt-Fe alloys, as well as the multicomponent compounds of Ru, Os, Ir, Rh, Pt with Fe replacing the Os-Ir-Ru alloys and PGE sulfides, result from serpentinization of PGM-bearing rocks. The PGM assemblage in the Ol'khovaya-1 River placers is related to the Karaginsky ophiolite complex of the Kamchatskiy Mys Peninsula.Keywords: platinum-group minerals, ophiolitic rocks, iridium-osmium paragenesis, isoferroplatinum-ruthenium paragenesis, Kamchatskiy Mys Peninsula, Russia. SOmmaiReLes assemblages de minéraux prélevés dans les placers de la rivière Olkhovaya-1, au Kamchatka, en Russie orientale, contiennent de l'information génétique concernant leur évolution. Les alliages Os-Ir-Ru sont les minéraux prédominants (80%); nous reconnaissons toutes les espèces connues. Parmi les alliages Pt-Fe, nous trouvons le platine natif, le platine riche en fer, et l'isoferroplatine. Les caractéristiques suivantes indiquent une minéralisation associée à un complexe ophiolitique: (1) dans le diagramme Os-Ru-Ir, les compositions de l'alliage hexagonal définissent un tracé d'enrichissement en ruthénium; (2) nous trouvons deux paragenèses magmatiques typiques parmi les alliages, osmium-iridium précoce et isoferroplatine-ruthénium tardif, les deux étant associés à la laurite et à la solution solide laurite-irarsite (Ru,Ir)(S,As) 2 . La cooperite, la sperrylite et les minéraux de Pd se sont formés à un stade postmagmatique. L'association tétraferroplatine-tulameenite, qui remplace les alliages Pt-Fe, ainsi que les composés à multi-composantes Ru, Os, Ir, Rh, Pt avec Fe, qui remplacent les alliages Os-Ir-Ru et les sulfures des éléments du groupe du platine, résulteraient de la serpentinisation des roches porteuses des minéraux du groupe du platine. Ces minéraux dans les placers de la rivière Ol'khovaya-1 proviendraient du massif ophiolitique de Karaginsky, qui affleure sur la péninsule de Kamchatskiy Mys.(Traduit par la Rédaction) Mots-clés: minéraux du groupe du platine, roches ophiolitiques, paragenèse iridium-osmium, paragenèse isoferroplatine-ruthé-nium, péninsule Kamchatskiy Mys, Russie. §

The system Pd–Ag–S: phase relations and mineral assemblages

“…Furthermore, the occurrences of unnamed phases with compositions that belong to the system Pd–Ag–S have also been reported in the literature, in particular from alluvial deposits related to mafic–ultramafic bedrock sources (e.g. Augé and Legendre 1992; Tolstykh et al , 2009). Therefore, the phase relations within the Pd–Ag–S system are of mineralogical interest.…”

Hydrothermal remobilization platinum group elements and their secondary minerals in chromitite deposits of the Eastern Sayan ophiolites (Russia)

“…During of these processes, native Os 0 and Ru 0 formed [17,18]. Fluids or/and hydrothermal solutions can affect on the boundaries or cracks of hightemperature PGM grains and they will change their composition according to their primary solubility [19,20]. During the alteration (desulphurisation or after) of the primary PGE phases, with high activity of metallic Fe, Ni, [16] this metals begins to enter platinum group phases with the formation of garutiite, zaccarinite.…”

Petrogenesis of the Platinum-Group Minerals

“…The vast majority of ophiolite-derived PGM-bearing placers are uneconomic but some of them were mined using artisanal methods for their associated gold in the Middle Ages (e.g., Krstić and Tarkian 1997 and references therein). Platinum-group mineral bearing placers are associated with ophiolites in Papua New Guinea (Harris and Cabri 1991;Weiser and Bachmann 1999), Adamsfield in Tasmania Brandon et al 1998Brandon et al , 2006, Meratus-Bobaris in Borneo (Harris and Cabri 1991;Hattori et al 2004;Coggon et al 2011), Samar in the Philippines (Nakagawa and Franco 1997), Hokkaido in Japan Nakawaga and Franco 1997;Hirata et al 1998), Veluce in Yugoslavia (Krstić and Tarkian 1997), the Rhodope Complex (Tsintsov and Damayanov 1994;Tsintsov 2000Tsintsov , 2003Tsintsov , 2004, Sagua de Tánamo in eastern Cuba (Díaz-Martínez et al 1998), southwestern Oregon and northern California (Walker et al 1997;Bird et al 1999;Meibom et al 2004;Walker et al 2005;, and in the ophiolites of Karaginsky in the Kamchatka peninsula (Tolstykh et al 2009). Additionally, placer PGM have been found in laterites developed on the ophiolites of Samar and Dinagat islands (Franco et al 1993;Nakawaga and Franco 1997) and the Pirogues River in New Caledonia (Augé and Legendre 1994).…”