Origin of noble-metal nuggets in sulfide-saturated arc magmas: A case study of olivine-hosted sulfide melt inclusions from the Tolbachik volcano (Kamchatka, Russia)

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 620-624
Author(s):  
Vadim S. Kamenetsky ◽  
Michael Zelenski
Keyword(s):  
Noble Metals ◽  
Melt Inclusions ◽  
Basaltic Magma ◽  
Sulfide Liquid ◽  
Direct Crystallization ◽  
Arc Magmas ◽  
Tolbachik Volcano ◽  
Sulfide Melt ◽  
Significant Uptake

Abstract Minerals that contain platinum-group elements (PGEs) and occur in some magmatic Cu-Ni sulfide deposits have been ascribed to crystallization from an originally PGE-rich sulfide liquid. The occurrence of PGE-bearing minerals (PGMs) in some sulfide-undersaturated primitive melts has been envisaged and recently reported, whereas direct crystallization of PGMs in sulfide-saturated silicate magmas is seemingly hindered by strong partitioning of PGE into immiscible sulfide melts. In this study, we discovered abundant nanoparticles containing noble metals in association with sulfide melt inclusions entrapped inside primitive olivine phenocrysts (Fo85–92) from the recent basaltic magma of the Tolbachik volcano (Kamchatka arc, Russia). These nuggets occur in swarms on the surface of the sulfide globules and are represented by native metals, sulfides, and alloys of Pd, Pt, Au, Pb, and Bi. The nuggets on different globules can be either Pd- or Pt-rich nuggets, and the compositions are highly variable, even among adjacent nuggets. We argue that the diffusive supply of Pd from the external nuggets can be responsible for significant uptake of Pd (up to 2 wt%) in the sulfide melt. We consider direct crystallization of PGMs in a primitive basaltic melt undergoing sulfide unmixing, and possibly sulfide breakdown due to oxidation, as another mechanism additional to their “classic” origin from the PGE-rich sulfide melt in response to solidification.

scholarly journals Noble Metals in Arc Basaltic Magmas Worldwide: A Case Study of Modern and Pre-Historic Lavas of the Tolbachik Volcano, Kamchatka

2021 ◽  
Vol 9 ◽  
Author(s):  
Anton Kutyrev ◽  
Michael Zelenski ◽  
Nikolai Nekrylov ◽  
Dmitry Savelyev ◽  
Alkiviadis Kontonikas-Charos ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Noble Metals ◽  
Mantle Wedge ◽  
Mantle Melting ◽  
Magmatic Differentiation ◽  
Arc Magmas ◽  
Promising Tool ◽  
Tolbachik Volcano ◽  
Single Arc

Platinum-group elements (PGE) and gold are a promising tool to assess the processes of mantle melting beneath the subduction zones. However, fractionation processes in magmas inevitably overwrite the initial metal budgets of magmas, making constraints on the melting processes inconclusive. Moreover, little is still known about the geochemical behavior of a particular metal in a single arc magmatic system, from mantle melting towards magma solidification. Here we compare noble metals in lavas from several eruptions of the Tolbachik volcano (Kamchatka arc) to better understand the effects of magma differentiation, estimate primary melt compositions and make constraints on the mantle melting. We show that Ir, Ru, Rh and, to a lesser extent, Pt are compatible during magmatic differentiation. The pronounced incompatible behavior of Cu and Pd, observed in Tolbachik magmas, rules out the significant influence of sulfide melts on the early magmatic evolution in this particular case. Gold is also incompatible during magmatic differentiation; however, its systematics can be affected by the inferred gold recycling in the plumbing system of Tolbachik. Although the Tolbachik lavas show only slightly higher PGE fractionation than in MORB, a notable negative Ru anomaly (higher Pt/Ru and Ir/Ru) is observed. We attribute this to be a result of greater oxidation in the subarc mantle (by 1–4 log units), which promotes crystallization of Ru-bearing phases such as Fe3+-rich Cr-spinel and laurite. The estimated Pd contents for the parental melt of the Tolbachik lavas approaches 6.5 ppb. This is several times higher than reported MORB values (1.5 ± 0.5 ppb), suggesting the enrichment of Pd in the mantle wedge. Our results highlight the influence of the subduction-related processes and mantle wedge refertilization on the noble metal budgets of arc magmas.

scholarly journals High Sulfur in Primitive Arc Magmas, Its Origin and Implications

Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 37
Author(s):  
Michael Zelenski ◽  
Vadim S. Kamenetsky ◽  
Nikolai Nekrylov ◽  
Alkiviadis Kontonikas-Charos
Keyword(s):  
Subduction Zones ◽  
Melt Inclusions ◽  
Solubility Limit ◽  
Calc Alkaline ◽  
Sulfur Solubility ◽  
Arc Magmas ◽  
Tolbachik Volcano ◽  
Magmatic Sulfide ◽  
Low Sulfur ◽  
Basaltic Melts

Sulfur contents in 98.5% of melt inclusions (MI) from calc-alkaline subduction basalts do not exceed 4000 ppm, whereas experimentally established limits of sulfur solubility in basaltic melts with high fO2 (characteristic of subduction zones, e.g., QFM + 2) surpass 14,000 ppm. Here we show that primitive (Mg# 62-64) subduction melts may contain high sulfur, approaching the experimental limit of sulfur solubility. Up to 11,700 ppm S was measured in olivine-hosted MI from primitive arc basalt from the 1941 eruption of the Tolbachik volcano, Kamchatka. These MI often contain magmatic sulfide globules (occasionally enriched in Cu, Ni, and platinum-group elements) and anhydrite enclosed within a brown, oxidized glass. We conclude that the ubiquitous low sulfur contents in MI may originate either from insufficient availability of sulfur in the magma generation zone or early magma degassing prior to inclusion entrapment. Our findings extend the measured range of sulfur concentrations in primitive calc-alkaline basaltic melts and demonstrate that no fundamental limit of 4000 ppm S exists for relatively oxidized subduction basalts, where the maximum sulfur content may approach the solubility limit determined by crystallization of magmatic anhydrite.

NI-RICH SULFIDE MELT INCLUSIONS IN YAKUTIAN DIAMONDS

2019 ◽  
Author(s):  
Alla M. Logvinova ◽  
◽  
Richard Wirth ◽  
Alexey O. Serebriannikov ◽  
Nikolay V. Sobolev
Keyword(s):  
Melt Inclusions ◽  
Sulfide Melt

scholarly journals Anorthosites of the low-sulfide platiniferous horizon (Reef I) in the upper riphean Yoko-Dovyren massif (Northern Cisbaikalia): new data on the composition, PGE-Cu-Ni mineralization, fluid regime and formation conditions

2019 ◽  
Vol 61 (4) ◽  
pp. 15-43
Author(s):  
D. A. Orsoev
Keyword(s):  
Noble Metals ◽  
Decisive Role ◽  
Platinum Metal ◽  
Thermal Shrinkage ◽  
Volatile Components ◽  
Sulfide Liquid ◽  
Upper Riphean ◽  
Mineral Associations ◽  
Composition And Structure ◽  
Formation Conditions

The carried out studies based on new data allowed to give mineralogical, petro- and geochemical characteristics to anorthosites, which are the main link and the major concentrator of PGE and Au in the composition of low-sulfide platinum metal mineralization, localized in a specific taxitic horizon (Reef I) of the Yoko-Dovyren massif. The revealed features of the composition and structure of this horizon indicate that the formation of anorthosites is caused by both the actual magmatic and the late- and postmagmatic processes with a high activity of volatile components. The horizon occurrence can be explained in terms of the “compaction” hypothesis and thermal shrinkage phenomenon. At the boundary of the rocks contrasting in composition and characteristics, when they are cooled, weakened zones form up to cracks and cavities, into which the interstitial leucocratic melt and volatiles squeezed out of the underlying horizons of the massif sucked as a result of the decompression effect. The revealed patterns of changes in the compositions of Pl (82-88% An), Ol (78-81% Fo), Cpx (40-44% En, 9-18% Fs, 41-47% Wo) and Opx (74-78% En, 16-24% Fs, 2-5% Wo) indicate fractional crystallization of the detrital melt. The processes of fluid-magmatic interaction led to a considerable heterogeneity of anorthosites and other rocks, the formation of disequilibrium mineral associations and concentration of ore-generating components. Sulfide associations are considered as products of the subsolidus transformation of solid solutions (mss and iss + poss) formed during the crystallization of an immiscible sulfide liquid enriched in Cu. It is demonstrated that noble metals were associated not only with a limited amount of sulfide liquid. The major part of noble metals with “crust” components (Sn, Pb, Hg, Bi, As, Sb, Te, S, etc.) entered the anorthosite cavities along with volatile components and chlorine, thus causing an abundance of native minerals among platinoids. The decisive role of reduced gases (H2, CH4, CO), H2O and Cl in the genesis of precious metal minerals is estimated.

SULFIDE MELT INCLUSIONS AS EVIDENCE FOR THE EXISTENCE OF A SULFIDE PARTIAL MELT AT BROKEN HILL, AUSTRALIA

2005 ◽  
Vol 100 (4) ◽  
pp. 773-779 ◽  
Author(s):  
Heather A. Sparks ◽  
John A. Mavrogenes
Keyword(s):  
Melt Inclusions ◽  
Partial Melt ◽  
Broken Hill ◽  
Sulfide Melt

Comparative Petrological Studies of 1962 and 1988–1989 Eruptions of Tokachidake Volcano, Japan: A Case Study for Understanding the Relationship Between Eruption Style and Magma Processes

2019 ◽  
Vol 14 (5) ◽  
pp. 766-779
Author(s):  
Mitsuhiro Nakagawa ◽  
Akiko Matsumoto ◽  
Kyohei Kobayashi ◽  
Keiji Wada ◽  
◽  
...  
Keyword(s):  
Basaltic Magma ◽  
Magma Ascent ◽  
Eruption Style ◽  
Magma Plumbing System ◽  
Magma Supply ◽  
The Matrix ◽  
Cap Rock ◽  
The Difference ◽  
The Relationship

Repeated magmatic eruptions of Tokachidake volcano have caused severe volcanic disasters on three occasions during the 20th century. To prepare for the next eruptive activity, understanding the structure of the magma plumbing system by using petrological analysis of juvenile materials is crucial. Here, we perform petrological analysis of juvenile materials to investigate the difference between two contrasting eruptions in 1962 and 1988–1989, respectively. All these juvenile materials are composed of mafic andesite, which were formed by mixing of olivine-bearing basaltic and pyroxene andesitic magmas. The compositional zonations of olivine phenocrysts in all of these rocks suggest that the injection of the basaltic magma into the andesitic magma occurred several months prior to the 1962 eruption and about six months before the 1988–1989 eruption. In the case of the 1962 activity, the mixed magma rapidly ascended without stagnation from the magma chamber and erupted as a sub-Plinian type. However, the juvenile materials of the 1988–1989 eruptions show distinct petrological features such as higher crystallinity of the matrix, orthopyroxene reaction rims around the olivine, and overgrowth mantle zones around Ti-magnetite phenocrysts. These features suggest that the mixed magma ascended slowly and possibly stagnated at shallower levels prior to eruption. The stagnated magma became a cap rock of the vent system and caused a series of Vulcanian eruptions. These distinct modes of magma ascent can be explained by differences in the magma supply rate. In the case of the 1962 eruption, the volume of magma that erupted in a period of less than 24 h was 7.1 × 107 m3. On the contrary, 23 explosions occurred over three months of the 1988–1989 activity and generated 1 × 105 m3 of ejecta including juvenile and non-juvenile materials. These large eruption rate differences can be attributed to the distinct ascent rates of the magma between the two eruptive activities.

scholarly journals Silicate-sulfide liquid immiscibility in modern arc basalt (Tolbachik volcano, Kamchatka): Part I. Occurrence and compositions of sulfide melts

2018 ◽  
Vol 478 ◽  
pp. 102-111 ◽  
Author(s):  
M. Zelenski ◽  
V.S. Kamenetsky ◽  
J.A. Mavrogenes ◽  
A.A. Gurenko ◽  
L.V. Danyushevsky
Keyword(s):  
Liquid Immiscibility ◽  
Sulfide Liquid ◽  
Tolbachik Volcano

The mechanism of Re enrichment in arc magmas: evidence from Lau Basin basaltic glasses and primitive melt inclusions

2004 ◽  
Vol 222 (1) ◽  
pp. 101-114 ◽  
Author(s):  
Weidong Sun ◽  
Victoria C Bennett ◽  
Vadim S Kamenetsky
Keyword(s):  
Melt Inclusions ◽  
Lau Basin ◽  
Arc Magmas

scholarly journals Magmatic architecture below the Okataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa New Zealand, inferred from basalt geochemistry

2021 ◽  
Author(s):  
Ery Hughes ◽  
Sally Law ◽  
Geoff Kilgour ◽  
Jon Blundy ◽  
Heidy Mader
Keyword(s):  
New Zealand ◽  
Melt Inclusions ◽  
Basaltic Magma ◽  
Taupo Volcanic Zone ◽  
Volcanic Centre ◽  
Volcanic Zone ◽  
Magma Evolution ◽  
Aotearoa New Zealand ◽  
Basalt Geochemistry ◽  
Rhyolitic Volcanism

The Okataina Volcanic Centre (OVC) is the most recently active rhyolitic volcanic centre in the Taupō Volcanic Zone, Aotearoa New Zealand. Although best known for its high rates of explosive rhyolitic volcanism, there are numerous examples of basaltic to basaltic-andesite contributions to OVC eruptions, ranging from minor involvement of basalt in rhyolitic eruptions to the exclusively basaltic 1886 C.E. Plinian eruption of Tarawera. To explore the basaltic component supplying this dominantly rhyolitic area, we analyse the textures and compositions (minerals and melt inclusions) of four basaltic eruptions within the OVC that have similar whole rock chemistry, namely: Terrace Rd, Rotomakariri, Rotokawau, and Tarawera. Data from these basaltic deposits provide constraints on the conditions of magma evolution and ascent in the crust prior to eruption, revealing that at least five different magma types (two basalts, two dacites, one rhyolite) are sampled during basaltic eruptions. The most abundant basaltic magma type is generated by cooling-induced crystallisation of a common, oxidised, basaltic melt at various depths throughout the crust. The volatile content of this melt was increased by protracted fluid-undersaturated crystallisation. All eruptions display abundant evidence for syn-eruptive mixing of the different magma types. Rotomakariri, consisting of a mafic crystal cargo mixed into a dacitic magma is the most extreme example of this process. Despite similar bulk compositions, comparable to other basaltic deposits in the region, these four OVC eruptions are texturally distinct as a consequence of their wide variation in eruption style.

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