Platinum-Group Minerals in Lode and Placer Deposits Associated With the Ural-Alaskan-Type Gal'moenan Complex, Koryak Kamchatka Platinum Belt, Russia

Abstract

Mineralization in the platinum-group elements occurs in lodes in the dunite-clinopyroxenite-gabbro Gal'moenan complex, in the Koryak-Kamchatka Platinum Belt of Russia, and in associated placers, namely those along the Levtyrinyvayam River and Ledyanoy and Penistiy creeks at different distances from the source. The grains of Pt-Fe alloy in lode deposits are isoferroplatinum and have Pt 3 Fe compositions, whereas those in the Levtyrinyvayam River placer range in composition from native to ferroan platinum and having iron contents generally higher than in the lodes (30-35 at.% Fe). Platinum grains from the Ledyanoy Creek placer are larger and more commonly intergrown with chromite than those from the Levtyrinyvayam River. Minor elements, which are indicators of conditions of formation of the Pt-Fe alloy, exhibit different concentrations in lodes and in the nearby placers. Platinum-iron alloy from the Levtyrinyvayam placer, the farthest from the source, represents the eroded upper apical part of the intrusion, and contains mainly Pd. The Penistiy placer receives platinum from dunite and pyroxenite of a marginal facies of the complex, and thus platinum-iron alloy bearing Rh-Ir and Pd-Rh. Placer isoferroplatinum deposited in the Ledyanoy Creek, which drains dunite and chromite-bearing rocks in the south of the intrusion, is rich in Ir (up to 6.98 wt.%), as is the Pt-Fe alloy in the Gal'moenan complex (4.34 wt.% Ir). Most grains contain also a relatively high Rh content. Isoferroplatinum + iridium and isoferroplatinum + osmium are two main primary magmatic parageneses revealed in both placers and lodes, though the first is more commonly found in lodes and in the Ledyanoy Creek placer, and the latter in the Levtyrinyvayam River placer. Lodes mostly contain laurite, RuS 2 , and the Levtyrinyvayam placer bears all varieties of (Ru,Os)S 2 , including Ru-free Rh-rich erlichmanite (Os,Rh)S 2. The irarsite-hollingworthite series predominates in lodes, and the irarsite-platarsite and osarsiteplatarsite series predominate in the Levtyrinyvayam placer. Sperrylite in lodes may contain up to 6.94 wt.% Sb, and thus differs from that in placers. The phase (Pt 0.96 Fe 0.02) ⌺0.98 (As 1.17 Sb 0.75 S 0.09) ⌺2 , a member of the sperrylite-geversite solid solution, has been found in a lode. Complete solid-solution between RuS 2 and RuAsS on one hand, and PtAsS and PtAs 2 on the other, is demonstrated. In the Gal'moenan complex, concentrations of Ir decrease, and those of Pd and Os increase, toward the upper or apical parts of the complex.

Large-volume platinum ore deposits in zonal mafic-ultramafic complexes of the Ural-Alaskan type and the outlook for their development

“…Fluid facilitated the exchange reactions and the recrystallization of dunite. This concept was subse quently developed by researchers of zonal maficultramafic complexes in the Platinum Belt of the Urals (Razin, 1968(Razin, , 2008Ivanov, 1997;Anikina, Pushkarev, and Vilisov, 1999;Volchenko and Koroteev, 2000;Pushkarev, 2000;Pushkarev et al, 2007;Tolstykh et al, 2009) and the Koryak-Kamchatka Platinum belt (Sidorov et al, 2001(Sidorov et al, , 2009Vil'danova et al, 2002;Tolstykh, Sidorov, Kozlov, 2004;Kozlov, 2007;Moch alov and Bortnikov, 2008). In the opinion of Ivanov (1997), the transition zone between recrystallized coarse grained dunite in the central part of zonal mas sifs and high temperature fine grained dunite of mar ginal zone is most favorable for the late migration of ore matter through fracture and free cavities.…”

“…Romanov, and others. The first positive results in localization of placer forming PGM mineralization were obtained at the very end of the 20th century as a result of petrolog ical, mineralogical, and geochemical studies (Polya nin et al, 2000;Sidorov et al, 2001;Osipenko et al, 2002; Mochalov et al, 2002;Tolstykh, Sidorov, and Kozlov, 2004;Kozlov and Chanturiya, 2009). More than 350 points of mineralization with >1 gpt Pt con tent have been found in the southern part of the massif.…”

“…Ultramafic rocks covering more than 90% of the massif area comprise the dunite core and marginal wehrlite, olivine and magnetite clinopyroxenite, clinopyroxene hornblen dite, and gabbro (Batanova, Astrakhantsev, and Sidorov, 1991;Polyanin et al, 2000;Vil'danova et al, 2002;Mochalov et al, 2002). Chromitite bodies have insignificant thickness and extent (chromite segrega tions are less than 10 m 2 in area) but are characterized by diversity in morphology and texture (Zaitsev, Koly ada, and Melkomukov, 2001;Sidorov et al, 2004).…”

“…The lode platinum of the Gal'maenan massif was studied in the samples of dunite with accessory and schlieren chromite, as well as of chromitite from chromite veins containing 1.7-2.5 gpt Pt (Tolstykh, Sidorov, and Kozlov, 2004;Kozlov, 2009aKozlov, , 2009bSidorov et al, 2009). Pt-Fe alloys, awaruite, wairauite and other minerals have been identified (Table 3).…”

Zircon U–Pb geochronology, geochemistry, and Sr–Nd isotopes of the Ural–Alaskan type Tuerkubantao mafic–ultramafic intrusion in southern Altai orogen, China: Petrogenesis and tectonic implications

“…The UralAlaskan type intrusions are known as low-sulfide systems where PGE (platinum group element) enrichment may occur mainly as platinum-iron alloy. The economic mineralization can be found in spatially associated placer deposits, including the Koryak-Kamchatka platinum belt of Russia (Tolstykh et al, 2004), the Fifield district in New South Wales, Australia (Slansky et al, 1991), Union Bay (Freeman, 2001) and Salt Chuck (Freeman, 2008) in southeastern Alaska. The studies of Cu-Ni-PGE sulfide mineralization in the Ural-Alaskan type intrusions suggested that they have a potential to host world-class sulfide-rich Cu-Ni-PGE deposits (Nixon, 1998;Helmy and Mogessie, 2001;Naldrett, 2004;Pettigrew and Hattori, 2006;Thakurta et al, 2008Thakurta et al, , 2014Ripley, 2009).…”