TY - JOUR

T1 - Caught in the moment: interaction of immiscible carbonate and sulfide liquids in mafic silicate magma—insights from the Rudniy intrusion (NW Mongolia)

AU - Cherdantseva, Maria

AU - Vishnevskiy, Andrey

AU - Jugo, Pedro J.

AU - Martin, Laure A.J.

AU - Aleshin, Matvei

AU - Roberts, Malcolm P.

AU - Shaparenko, Elena

AU - Langendam, Andrew

AU - Howard, Daryl L.

AU - Fiorentini, Marco L.

N1 - Open Access funding enabled and organized by CAUL and its Member Institutions This research is a part of the PhD thesis of MC, who acknowledges the support of the University of Western Australia through the SIRF scholarship. The funding was also provided by the Russian Foundation of Basic Research (project no 16–35-00100) and by the Australian Research Council through grant DP190102422 awarded to MF. Part of this research was undertaken on the X-ray fluorescence microscopy beamline at the Australian Synchrotron, part of ANSTO (Projects 17174 and 18626). Part of this work was done on state assignment of IGM SB RAS (№ 122041400044–2; № 122041400312–2). Публикация для корректировки.

PY - 2024/4

Y1 - 2024/4

N2 - The Devonian Rudniy intrusion is a composite magmatic body comprising two gabbroid units. Located in the Tsagaan-Shuvuut ridge in NW Mongolia, it is the only one known to contain disseminated sulfide Ni-Cu-PGE minerals out of numerous gabbroid intrusions surrounding the Tuva depression. The ore occurs as disseminated sulfide globules made of pyrrhotite, pentlandite, chalcopyrite, and cubanite, confined to a narrow troctolitic layer at the margins of a melanogabbro, at the contact with a previously emplaced leucogabbro. Globules generally display mantle-dominated sulfur isotopic signatures but show variable metallogenic and mineralogical characteristics, as well as notably different sizes and morphologies reflecting variable cooling and crystallization regimes in different parts of the intrusion. Sulfides from the chilled margin of the melanogabbro are surrounded and intergrown with volatile-rich (i.e., CO2-, H2O-, F-, and Cl) phases such as calcite, chlorite, mica, amphibole, and apatite. Based on the mineralogical and textural relationships of volatile-rich phases with sulfides, we argue that this assemblage represents the product of the crystallization of volatile-rich carbonate melt immiscible with both silicate and sulfide liquids. We put forward the hypothesis that volatile-rich carbonate melt envelops sulfide droplets facilitating their transport in magmatic conduits and that this process may be more widespread than commonly thought. The smaller sulfide globules, which are interpreted to derive from the breakup of larger globules during transport and emplacement, do not display an association with volatile-rich phases, suggesting that the original carbonate melt could have been detached from them during the evolution of the magmatic system. Variable rates of crystallization may have been responsible for the observed disparities in the mineralogical and metallogenic characteristics of different sulfide globules entrained in the Rudniy intrusion.

AB - The Devonian Rudniy intrusion is a composite magmatic body comprising two gabbroid units. Located in the Tsagaan-Shuvuut ridge in NW Mongolia, it is the only one known to contain disseminated sulfide Ni-Cu-PGE minerals out of numerous gabbroid intrusions surrounding the Tuva depression. The ore occurs as disseminated sulfide globules made of pyrrhotite, pentlandite, chalcopyrite, and cubanite, confined to a narrow troctolitic layer at the margins of a melanogabbro, at the contact with a previously emplaced leucogabbro. Globules generally display mantle-dominated sulfur isotopic signatures but show variable metallogenic and mineralogical characteristics, as well as notably different sizes and morphologies reflecting variable cooling and crystallization regimes in different parts of the intrusion. Sulfides from the chilled margin of the melanogabbro are surrounded and intergrown with volatile-rich (i.e., CO2-, H2O-, F-, and Cl) phases such as calcite, chlorite, mica, amphibole, and apatite. Based on the mineralogical and textural relationships of volatile-rich phases with sulfides, we argue that this assemblage represents the product of the crystallization of volatile-rich carbonate melt immiscible with both silicate and sulfide liquids. We put forward the hypothesis that volatile-rich carbonate melt envelops sulfide droplets facilitating their transport in magmatic conduits and that this process may be more widespread than commonly thought. The smaller sulfide globules, which are interpreted to derive from the breakup of larger globules during transport and emplacement, do not display an association with volatile-rich phases, suggesting that the original carbonate melt could have been detached from them during the evolution of the magmatic system. Variable rates of crystallization may have been responsible for the observed disparities in the mineralogical and metallogenic characteristics of different sulfide globules entrained in the Rudniy intrusion.

KW - CO2

KW - Carbonate melt

KW - Magmatic sulfides

KW - Platinum group elements

KW - Silicate cap

KW - Sulfide globules

KW - Sulfur isotopes

KW - Volatile

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85176456863&origin=inward&txGid=1a9142519a6fc0adb0786c350dd0598d

UR - https://www.mendeley.com/catalogue/66244a91-1b7c-3288-a1ee-8fdd368c32cc/

U2 - 10.1007/s00126-023-01228-1

DO - 10.1007/s00126-023-01228-1

M3 - Article

VL - 59

SP - 733

EP - 755

JO - Mineralium Deposita

JF - Mineralium Deposita

SN - 0026-4598

IS - 4

ER -