TY - JOUR

T1 - Hydrothermal alteration of chevkinite-group minerals

T2 - Part 2. Metasomatite from the Keivy massif, Kola Peninsula, Russia

AU - MacDonald, Raymond

AU - Bagiński, Bogusław

AU - Kartashov, Pavel M.

AU - Zozulya, Dmitry

AU - Dzierzanowski, Piotr

PY - 2015/10

Y1 - 2015/10

N2 - Chevkinite-(Ce) in a mineralized quartz-epidote metasomatite from the Keivy massif, Kola Peninsula, Russia, underwent at least two stages of low-temperature alteration. In the first, it interacted with hydrothermal fluids, with loss of Ca, Fe, LREE and Si and strong enrichment in Ti. The altered chevkinite was then rimmed and partially replaced by a zone of ferriallanite-(Ce) and davidite-(La), in turn rimmed by a zone of allanite-(Ce) richer in the epidote component. The allanite zone was in turn partially replaced by rutile-titanite-quartz assemblages, the formation of titanite postdating that of rutile. Aeschynite-(Y), aeschynite-(Ce) and REE-carbonates are accessory phases in all zones. The hydrothermal fluids were alkaline, with significant proportions of CO2 and F. At various alteration stages, the Ca, Si ± Al activities in the fluid were high. Formation of the aeschynite is discussed in relation to its stability in broadly similar parageneses; it was a primary phase in the unaltered chevkinite zone whereas in other zones it formed from Nb, Ti, REE and Th released from the major phases.

AB - Chevkinite-(Ce) in a mineralized quartz-epidote metasomatite from the Keivy massif, Kola Peninsula, Russia, underwent at least two stages of low-temperature alteration. In the first, it interacted with hydrothermal fluids, with loss of Ca, Fe, LREE and Si and strong enrichment in Ti. The altered chevkinite was then rimmed and partially replaced by a zone of ferriallanite-(Ce) and davidite-(La), in turn rimmed by a zone of allanite-(Ce) richer in the epidote component. The allanite zone was in turn partially replaced by rutile-titanite-quartz assemblages, the formation of titanite postdating that of rutile. Aeschynite-(Y), aeschynite-(Ce) and REE-carbonates are accessory phases in all zones. The hydrothermal fluids were alkaline, with significant proportions of CO2 and F. At various alteration stages, the Ca, Si ± Al activities in the fluid were high. Formation of the aeschynite is discussed in relation to its stability in broadly similar parageneses; it was a primary phase in the unaltered chevkinite zone whereas in other zones it formed from Nb, Ti, REE and Th released from the major phases.

KW - AESCHYNITE

KW - CHEVKINITE GROUP

KW - DAVIDITE

KW - EPIDOTE SUPERGROUP

KW - HYDROTHERMAL FLUIDS

U2 - 10.1180/minmag.2015.079.5.02

DO - 10.1180/minmag.2015.079.5.02

M3 - Journal article

VL - 79

SP - 1039

EP - 1059

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 5

ER -