TY - JOUR

T1 - Amazonite Li–F Granites with REE–Nb–Zr–Th–U Specialization

T2 - Geochemistry, Mineralogy, and Isotope Geochronology of the Turga Massif, Eastern Transbaikalia

AU - Syritso, L. F.

AU - Ivanova, A. A.

AU - Badanina, E. V.

AU - Volkova, E. V.

N1 - Syritso, L.F., Ivanova, A.A., Badanina, E.V. et al. Amazonite Li–F Granites with REE–Nb–Zr–Th–U Specialization: Geochemistry, Mineralogy, and Isotope Geochronology of the Turga Massif, Eastern Transbaikalia. Petrology 29, 54–76 (2021). https://doi.org/10.1134/S0869591121010069

PY - 2021/2/14

Y1 - 2021/2/14

N2 - Abstract: The paper reports major relations and trends determined in the distributions of trace elements and the Sr and Nd isotope composition of leucogranites of the Turga massif in Eastern Transbaikalia. Three varieties of the leucogranites are distinguished: porphyritic biotite granites, equigranular granites with Li-siderophyllite, and amazonite granites that make up small stocks and dikes. All of the rocks define a single Rb–Sr isochron that corresponds to an age of 134 ± 1 Ma at IR(Sr) = 0.71768 ± 22 and MSWD = 1.2, i.e., all of these rocks crystallized within a narrow age span. The porphyritic biotite granites, which are thought to be parental for the leucogranites, crystallized at lower temperatures (710–740°C) than the younger granites with Li-siderophyllite (810–850°C). Moreover, the granites with Li-siderophyllite have elevated Fe concentrations, which is reflected in that their micas are Fe-rich. The leucogranites are enriched in HFSE (270 ± 59 ppm Zr, 337 ± 93 ppm REE, 72 ± 31 ppm Th, and 16 ± 6 ppm U), which is atypical of amazonite granites in the study area. Considered together with very low Sr and low Ti and P concentrations, these compositional features are distinguishing features of A-type granites. The rare-metal granites of the Turga massif are unique in composition: being similar to amazonite granites in mineralized massifs, these rocks carry accessory minerals typical of peralkaline rocks. They contain LREE fluorides and fluorcarbonates (fluocerite, bastnaesite, and parisite), minerals of the pyrochlore and samarskite groups, and minerals of the isostructural group of REE–Y–Zr–Th–U silicate-phosphates. Our data provide grounds for classifying the rare-metal granites of the Turga massif with an unusual transitional geochemical subtype: peraluminous columbite-bearing amazonite granites of elevated alkalinity with peralkaline REE–Nb–Zr–Th–U mineralization.

AB - Abstract: The paper reports major relations and trends determined in the distributions of trace elements and the Sr and Nd isotope composition of leucogranites of the Turga massif in Eastern Transbaikalia. Three varieties of the leucogranites are distinguished: porphyritic biotite granites, equigranular granites with Li-siderophyllite, and amazonite granites that make up small stocks and dikes. All of the rocks define a single Rb–Sr isochron that corresponds to an age of 134 ± 1 Ma at IR(Sr) = 0.71768 ± 22 and MSWD = 1.2, i.e., all of these rocks crystallized within a narrow age span. The porphyritic biotite granites, which are thought to be parental for the leucogranites, crystallized at lower temperatures (710–740°C) than the younger granites with Li-siderophyllite (810–850°C). Moreover, the granites with Li-siderophyllite have elevated Fe concentrations, which is reflected in that their micas are Fe-rich. The leucogranites are enriched in HFSE (270 ± 59 ppm Zr, 337 ± 93 ppm REE, 72 ± 31 ppm Th, and 16 ± 6 ppm U), which is atypical of amazonite granites in the study area. Considered together with very low Sr and low Ti and P concentrations, these compositional features are distinguishing features of A-type granites. The rare-metal granites of the Turga massif are unique in composition: being similar to amazonite granites in mineralized massifs, these rocks carry accessory minerals typical of peralkaline rocks. They contain LREE fluorides and fluorcarbonates (fluocerite, bastnaesite, and parisite), minerals of the pyrochlore and samarskite groups, and minerals of the isostructural group of REE–Y–Zr–Th–U silicate-phosphates. Our data provide grounds for classifying the rare-metal granites of the Turga massif with an unusual transitional geochemical subtype: peraluminous columbite-bearing amazonite granites of elevated alkalinity with peralkaline REE–Nb–Zr–Th–U mineralization.

KW - bastnaesite

KW - Eastern Transbaikaklia

KW - fluocerite

KW - geochemistry

KW - LREE–Nb–Zr–Th specializaton

KW - peraluminous Li–F amazonite granites

KW - pyrochlore

KW - rock-forming processes

KW - samarskite

KW - thorite–xenotime–zircon–coffinite group

UR - http://www.scopus.com/inward/record.url?scp=85100861905&partnerID=8YFLogxK

U2 - 10.1134/S0869591121010069

DO - 10.1134/S0869591121010069

M3 - Article

AN - SCOPUS:85100861905

VL - 29

SP - 54

EP - 76

JO - Petrology

JF - Petrology

SN - 0869-5911

IS - 1

ER -