TY - JOUR

T1 - Hydrothermal alteration of a chevkinite-group mineral to a bastnäsite-(Ce)-ilmenite- columbite-(Fe) assemblage

T2 - interaction with a F-, CO2-rich fluid

AU - MacDonald, Raymond

AU - Bagiński, Bogusław

AU - Kartashov, Pavel M.

AU - Zozulya, Dmitry

AU - Dzierzanowski, Piotr

AU - Jokubauskas, Petras

PY - 2015/12

Y1 - 2015/12

N2 - The results are presented of a textural and mineral chemical study of a previously undescribed type of hydrothermal alteration of chevkinite-(Ce) which occurs in a syenitic pegmatite from the Vishnevye Mountains, Urals Region, Russia. The progressive alteration of the chevkinite to a bastnäsite-(Ce)-ilmenite-columbite-(Fe) assemblage through a series of texturally complex intermediate stages is described and electron microprobe analyses are given of all the major phases. Unusual Nb ± Th-rich phases formed late in the alteration sequence provide evidence of local Nb mobility. The main compositional fluxes are traced, especially of the REE, HFSE, Th and U. It appears that almost all elements, with the exception of La, released from the chevkinite-(Ce) were reincorporated into later phases, such that they did not leave the alteration crust in significant amounts. The hydrothermal fluids are inferred to have been F- and CO2-rich, with variable levels of Ca activity, and with fO2 mainly between the nickel-nickel oxide and magnetite-hematite buffers. This occurrence represents a new paragenesis for a columbite-group mineral.

AB - The results are presented of a textural and mineral chemical study of a previously undescribed type of hydrothermal alteration of chevkinite-(Ce) which occurs in a syenitic pegmatite from the Vishnevye Mountains, Urals Region, Russia. The progressive alteration of the chevkinite to a bastnäsite-(Ce)-ilmenite-columbite-(Fe) assemblage through a series of texturally complex intermediate stages is described and electron microprobe analyses are given of all the major phases. Unusual Nb ± Th-rich phases formed late in the alteration sequence provide evidence of local Nb mobility. The main compositional fluxes are traced, especially of the REE, HFSE, Th and U. It appears that almost all elements, with the exception of La, released from the chevkinite-(Ce) were reincorporated into later phases, such that they did not leave the alteration crust in significant amounts. The hydrothermal fluids are inferred to have been F- and CO2-rich, with variable levels of Ca activity, and with fO2 mainly between the nickel-nickel oxide and magnetite-hematite buffers. This occurrence represents a new paragenesis for a columbite-group mineral.

U2 - 10.1007/s00710-015-0394-2

DO - 10.1007/s00710-015-0394-2

M3 - Journal article

VL - 109

SP - 659

EP - 678

JO - Mineralogy and Petrology

JF - Mineralogy and Petrology

SN - 0930-0708

IS - 6

ER -