TY - JOUR

T1 - Brine–Melts and Fluids of the Fe-F-P-(Ba)-(Sr)-REE Central Asian Carbonatite Province (Southern Siberia and Mongolia): The Petrogenetic Aspects

AU - Prokopyev, Ilya

AU - Doroshkevich, Anna

AU - Redina, Anna

N1 - Melt and fluid inclusion studies were supported by the Russian Science Foundation Grant No. 22-17-00078 (https://rscf.ru/en/project/22-17-00078/, accessed on 1 February 2023). Geological investigation is done on state assignment of IGM SB RAS (122041400241-5) and GIN SB RAS (AAAA-A21-121011390002-2). Field work of carbonatites from the Central Tuva region was executed under TuvIKOPR SB RAS state contract No. 121031500140-2.

PY - 2023/4

Y1 - 2023/4

N2 - The carbonatite complexes of the Central Asian carbonatite province comprise the Siberian carbonatites of the Western Transbaikalia and the Central Tuva regions, as well as those from the Mushugai-Khudag complex in Southern Mongolia. They are confined to Late Mesozoic rift structures and have endured considerable tectono-magmatic processes caused by intense plume activity, which also accompanied their formation. A systematic study of melt and fluid inclusions revealed that these carbonatites formed as a result of immiscibility processes in silicate–carbonate (salt) melts, as well as fractional crystallization. Alkaline–carbonatite rocks crystallized in the presence of brine–melts with different compositions, i.e., alkaline–fluorine, carbonate, sulfate, phosphate, and chloride. These melts are responsible for mineralization during the orthomagmatic stage and the primary phase of Fe-F-P-(Ba)-(Sr)-REE ore formation at temperature ranges of 850–830 °C, 650–610 °C, and 560–440 °C and pressures between 290 and 350 MPa. At a later stage, the brine–melts evolved into saline hydrothermal fluids, which are considered to be the source of the second stage of F-(Ba)-(Sr)-REE ore mineralization. The saline crystal–fluid inclusions consist mainly of fluorine–sulfate–carbonate–chloride and bicarbonate–chloride compositions, with temperatures of approximately 480–250 °C and pressures below 250 MPa. The shift from melt to fluid in carbonatite complexes could occur more frequently in nature than previously believed and could also apply to other F-REE carbonatite complexes that are linked to rifting and plume activity in mountain-building zones.

AB - The carbonatite complexes of the Central Asian carbonatite province comprise the Siberian carbonatites of the Western Transbaikalia and the Central Tuva regions, as well as those from the Mushugai-Khudag complex in Southern Mongolia. They are confined to Late Mesozoic rift structures and have endured considerable tectono-magmatic processes caused by intense plume activity, which also accompanied their formation. A systematic study of melt and fluid inclusions revealed that these carbonatites formed as a result of immiscibility processes in silicate–carbonate (salt) melts, as well as fractional crystallization. Alkaline–carbonatite rocks crystallized in the presence of brine–melts with different compositions, i.e., alkaline–fluorine, carbonate, sulfate, phosphate, and chloride. These melts are responsible for mineralization during the orthomagmatic stage and the primary phase of Fe-F-P-(Ba)-(Sr)-REE ore formation at temperature ranges of 850–830 °C, 650–610 °C, and 560–440 °C and pressures between 290 and 350 MPa. At a later stage, the brine–melts evolved into saline hydrothermal fluids, which are considered to be the source of the second stage of F-(Ba)-(Sr)-REE ore mineralization. The saline crystal–fluid inclusions consist mainly of fluorine–sulfate–carbonate–chloride and bicarbonate–chloride compositions, with temperatures of approximately 480–250 °C and pressures below 250 MPa. The shift from melt to fluid in carbonatite complexes could occur more frequently in nature than previously believed and could also apply to other F-REE carbonatite complexes that are linked to rifting and plume activity in mountain-building zones.

KW - Central Asian Carbonatite Province

KW - Fe-F-(Ba)-(Sr)-REE

KW - Late Mesozoic

KW - brine–melts

KW - carbonate–silicate immiscibility

KW - carbonatites

KW - melt and fluid inclusion

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85156181944&origin=inward&txGid=5d6a4de7cb67e5b56c208dfb755a71b2

UR - https://www.mendeley.com/catalogue/5b161733-6456-3384-9962-ef03327c2980/

U2 - 10.3390/min13040573

DO - 10.3390/min13040573

M3 - Article

VL - 13

JO - Minerals

JF - Minerals

SN - 2075-163X

IS - 4

M1 - 573

ER -