Sulfide melt-silicate melt distribution coefficients for noble metals and other chalcophile elements as deduced from MORB: Implications for partial melting

1990 ◽  
Vol 54 (12) ◽  
pp. 3379-3389 ◽  
Author(s):  
C.L Peach ◽  
E.A Mathez ◽  
R.R Keays
Keyword(s):  
Partial Melting ◽  
Noble Metals ◽  
Distribution Coefficients ◽  
Silicate Melt ◽  
Chalcophile Elements ◽  
Melt Distribution ◽  
Sulfide Melt

Quantification of excess 231Pa in late Quaternary igneous baddeleyite

2020 ◽  
Vol 105 (12) ◽  
pp. 1830-1840 ◽  
Author(s):  
Yi Sun ◽  
Axel K. Schmitt ◽  
Lucia Pappalardo ◽  
Massimo Russo
Keyword(s):  
Late Quaternary ◽  
Central Italy ◽  
Direct Analysis ◽  
Weight Percent ◽  
Volcanic Field ◽  
Distribution Coefficients ◽  
Secular Equilibrium ◽  
Melt Distribution ◽  
D Values ◽  
Significant Figures

Abstract Initial excess protactinium (231Pa) is a frequently suspected source of discordance in baddeleyite (ZrO2) geochronology, which limits accurate U/Pb dating, but such excesses have never been directly demonstrated. In this study, Pa incorporation in late Holocene baddeleyite from Somma-Vesuvius (Campanian Volcanic Province, central Italy) and Laacher See (East Eifel Volcanic Field, western Germany) was quantified by U-Th-Pa measurements using a large-geometry ion microprobe. Baddeleyite crystals isolated from subvolcanic syenites have average U concentrations of ~200 ppm and are largely stoichiometric with minor abundances of Nb, Hf, Ti, and Fe up to a few weight percent. Measured (231Pa)/(235U) activity ratios are significantly above the secular equilibrium value of unity and range from 3.4(8) to 14.9(2.6) in Vesuvius baddeleyite and from 3.6(9) to 8.9(1.4) in Laacher See baddeleyite (values within parentheses represent uncertainties in the last significant figures reported as 1σ throughout the text). Crystallization ages of 5.12(56) ka (Vesuvius; MSWD = 0.96, n = 12) and 15.6(2.0) ka (Laacher See; MSWD = 0.91, n = 10) were obtained from (230Th)/(238U) disequilibria for the same crystals, which are close to the respective eruption ages. Applying a corresponding age correction indicates average initial (231Pa)/(235U)0 of 8.8(1.0) (Vesuvius) and 7.9(5) (Laacher See). For reasonable melt activities, model baddeleyite-melt distribution coefficients of DPa/DU = 5.8(2) and 4.1(2) are obtained for Vesuvius and Laacher See, respectively. Speciation-dependent (Pa4+ vs. Pa5+) partitioning coefficients (D values) from crystal lattice strain models for tetra- and pentavalent proxy ions significantly exceed DPa/DU inferred from direct analysis of 231Pa for Pa5+. This is consistent with predominantly reduced Pa4+ in the melt, for which D values similar to U4+ are expected. Contrary to common assumptions, baddeleyite-crystallizing melts from Vesuvius and Laacher See appear to be dominated by Pa4+ rather than Pa5+. An initial disequilibrium correction for baddeleyite geochronology using DPa/DU = 5 ± 1 is recommended for oxidized phonolitic melt compositions.

Experimentally determined sulfide melt-silicate melt partition coefficients for iridium and palladium

1994 ◽  
Vol 117 (1-4) ◽  
pp. 361-377 ◽  
Author(s):  
C.L. Peach ◽  
Edmond A. Mathez ◽  
Reid R. Keays ◽  
S.J. Reeves
Keyword(s):  
Partition Coefficients ◽  
Silicate Melt ◽  
Sulfide Melt

Trace element abundances and mineral/melt distribution coefficients in phonolites from the Laacher See volcano (Germany)

1983 ◽  
Vol 84 (2-3) ◽  
pp. 152-173 ◽  
Author(s):  
G. W�rrier ◽  
J. -M. Beusen ◽  
N. Duchateau ◽  
R. Gijbels ◽  
H. -U. Schmincke
Keyword(s):  
Trace Element ◽  
Distribution Coefficients ◽  
Element Abundances ◽  
Melt Distribution

DC_BASE: a database system to manage Nernst distribution coefficients and its application to partial melting modeling

2003 ◽  
Vol 29 (9) ◽  
pp. 1191-1198 ◽  
Author(s):  
Ignacio S. Torres-Alvarado ◽  
Surendra P. Verma ◽  
Hypitia Palacios-Berruete ◽  
Mirna Guevara ◽  
Oriana Yuridia González-Castillo
Keyword(s):  
Partial Melting ◽  
Database System ◽  
Distribution Coefficients

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.

Crystallization of sulfide liquids and the interpretation of ore composition

1997 ◽  
Vol 34 (4) ◽  
pp. 352-365 ◽  
Author(s):  
D. S. Ebel ◽  
A. J. Naldrett
Keyword(s):  
Major Elements ◽  
Distribution Coefficients ◽  
Liquid Composition ◽  
Sulfide Liquid ◽  
Free System ◽  
Element Partitioning ◽  
Ore Bodies ◽  
Sulfide Melt ◽  
Magmatic Sulfide ◽  
D Values

We have been exploring ways to quantitatively assess the extent to which fractionation of sulfide melt has effected variations in composition within magmatic sulfide ore bodies. Our approach has been to determine by experiment the crystallization paths of sulfide liquids in temperature and composition dimensions. In this paper, the results of new major-element partitioning experiments below 1050 °C in the nickel-free system are presented and summarized along with new and previous work in the Fe–Ni–Cu–S quaternary. The partition coefficients D for Cu between monosulfid solid solution (mss) and sulfide liquid in the Ni-free system (DCu = (wt.% Cu in mss)/(wt.% Cu in liquid)) cluster near 0.3, but decrease to nearly 0.1 for Cu-rich, S-poor liquids near 1000 °C. DNi also declines with decreasing sulfur content of the liquid, but increases with decreasing temperature. Preliminary data indicate that DNi exceeds 1.0 in low-Ni liquids with greater than 16 wt.% Cu, at 1050 °C. The quality of available data on the Fe–Ni–Cu–S system currently exceeds the sensitivity of crystallization models based on the distribution coefficient approximation for major elements. However, we present equations for variable distribution coefficients for Ni and Cu that can be incorporated into calculations of the ratio of trapped initial liquid to fractionated solid for bulk ore samples, using D values for platinum group elements from the literature. Fractionation can then be modeled quite well using an iterative approach, with D values changing in response to liquid composition with each increment of crystallization along an assumed temperature path.

scholarly journals Rh, Ir, and Ru Partitioning in the Cu-Poor IPGE Massive Ores, Talnakh Intrusion, Skalisty Mine, Russia

Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 18
Author(s):  
Nadezhda Tolstykh ◽  
Valeriya Brovchenko ◽  
Viktor Rad’ko ◽  
Maria Shapovalova ◽  
Vera Abramova ◽  
...  
Keyword(s):  
Trace Elements ◽  
Partial Melting ◽  
Base Metal ◽  
Bulk Composition ◽  
Metal Sulfides ◽  
Low Grade ◽  
Icp Ms ◽  
Platinum Group Minerals ◽  
Base Metal Sulfides ◽  
Sulfide Melt

Pyrrhotite (or Cu-poor) massive ores of the Skalisty mine located in Siberia, Russia, are unique in terms of their geochemical features. These ores are Ni-rich with Ni/Cu ratios in the range 1.3–1.9 and contain up to 12.25 ppm Ir + Rh + Ru in bulk composition, one of the highest IPGE contents for the Norilsk-Talnakh ore camp. The reasons behind such significant IPGE Contents cannot simply be explained by the influence of discrete platinum-group minerals on the final bulk composition of IPGE because only inclusions of Pd minerals such as menshikovite, majakite, and mertieite II in Pd-maucherite were observed. According to LA-ICP-MS data obtained, base metal sulfides such as pyrrhotite, pentlandite, and pyrite contain IPGE as the trace elements. The most significant IPGE concentrator being Py, which occurs only in the least fractionated ores, and contains Os up to 4.8 ppm, Ir about 6.9 ppm, Ru about 38.3 ppm, Rh about 36 ppm, and Pt about 62.6 ppm. High IPGE contents in the sulfide melt may be due to high degrees of partial melting of the mantle, interaction with several low-grade IPGE impulses of magma, and (or) fractionation of the sulfide melt in the magma chamber.

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