PHASE RELATIONS IN THE SYSTEM Au Cu Ag AT LOW TEMPERATURES, BASED ON NATURAL ASSEMBLAGES

Abstract

The composition of some 85 particles of native gold from the 15 Mile rodingite in serpentinite showing in the Coquihalla gold district and the Wheaton Creek placer in the Dease Lake district, British Columbia, falls mainly within the Cu-rich portion of the Au-Ag-Cu phase diagram. The particles display a variety of textures, including exsolution-induced textures. The textures and phase compositions are used to construct a low-temperature phase diagram for the system Au-Ag-Cu. This diagram represents a system that equilibrated for a longer period of time at a lower temperature than is accessible in synthetic systems. In this diagram, the composition AuCu is nearly stoichiometric, a three-phase region is found among AuCu (Au 1 SOMMAIRELa composition d'environ 85 particules d'or natif provenant de l'indice 15 Mile, dans une rodingite associée à une serpentinite du district aurifère de Coquihalla, et du placer de Wheaton Creek, du district de Dease Lake, en Colombie-Britannique, se situe surtout dans la partie riche en cuivre du système Au-Ag-Cu. Ces particules font preuve d'une variété de textures, dont des textures indicatives d'une exsolution. Les textures et la composition des phases servent à construire un diagramme de phases pour le système Au-Ag-Cu approprié à de faibles températures. Ce diagramme représente un système qui a progressé vers un état d'équilibre durant une période de temps beaucoup plus longue que ne serait possible en système synthétique. Dans ce diagramme, la composition AuCu est presque stoéchiométrique, une région à trois phases a été découverte impliquant AuCu

Gold in Mineralized Volcanic Systems from the Lesser Khingan Range (Russian Far East): Textural Types, Composition and Possible Origins

“…Decrease of temperature in the molten Cu-Ag-Au alloys will trigger their solidification followed by the exsolution of solid phases with variable concentrations of Cu, Ag and Au [82]. As we do not observe Cu-, Ag-and Au-rich exsolution structures similar to [82] in our samples, we conclude that homogenous intermetallic spherules in the LKR deposits have experienced very fast cooling, possibly below the solidus temperature. Since Cu-Ag-Au alloys produced in our experiments and natural spherules share clear compositional similarities, we propose that the matrix of the latter is also dominated by Cu3Au compositions.…”

“…Gold and silver form homogeneous alloys with copper within the temperature range characteristic of most high-temperature hydrothermal and magmatic processes [80,81]. Decrease of temperature in the molten Cu-Ag-Au alloys will trigger their solidification followed by the exsolution of solid phases with variable concentrations of Cu, Ag and Au [82]. As we do not observe Cu-, Ag-and Au-rich exsolution structures similar to [82] in our samples, we conclude that homogenous intermetallic spherules in the LKR deposits have experienced very fast cooling, possibly below the solidus temperature.…”

Relationship Between Some Selected Major, Minor and Trace Elements in the Iocg Deposits (On the Example of the Unique Sin Quyen Deposit, Lao Cai Province, North Vietnam)

“…9) indicating high similarity in their geochemical properties. Au-Ag alloy often commonly occurs in micro-vein form in gold and copper minerals with trace elements of Hg (Knight and Leitch, 2001;Gas'kov et al, 2001). The correlation Cu-Au is lower than Cu-Ag (compare Fig.…”

Mineralogy of Fluidolites and Genetically Related With Them Magmatic Rocks of the Mokrushinsky Area, the Taukha Terrane, Sikhote-Alin

“…Южного Урала, Агардагского массива альпинотипных гипер-базитов Южной Тувы (Au) [19], Корякского Нагорья (Au и ЭПГ) [6], Сахалина (Au) [26], Восточных Саян (Au, Ag, Pd) [8 и др.] и Британской Колумбии (Канада) (Au) [38]. Наибольшую известность получили родингиты Карабашского массива альпинотипных гипербазитов на Южном Урале, которые являлись объектом добычи золота (месторождение Золотая Гора).…”