TY - JOUR

T1 - Inclusions of crichtonite-group minerals in Cr-pyropes from the Internatsionalnaya kimberlite pipe, Siberian Craton

T2 - Crystal chemistry, parageneses and relationships to mantle metasomatism

AU - Rezvukhin, Dmitriy I.

AU - Malkovets, Vladimir G.

AU - Sharygin, Igor S.

AU - Tretiakova, Irina G.

AU - Griffin, William L.

AU - O'Reilly, Suzanne Y.

N1 - Publisher Copyright: © 2018 Elsevier B.V.

PY - 2018/5/1

Y1 - 2018/5/1

N2 - Cr-pyrope xenocrysts and associated inclusions of crichtonite-group minerals from the Internatsionalnaya kimberlite pipe were studied to provide new insights into processes in the lithospheric mantle beneath the Mirny kimberlite field, Siberian craton. Pyropes are predominantly of lherzolitic paragenesis (Cr2O3 2–6 wt%) and have trace-element spectra typical for garnets from fertile mantle (gradual increase in chondrite-normalized values from LREE to MREE-HREE). Crichtonite-group minerals commonly occur as monomineralic elongated inclusions, mostly in association with rutile, Mg-ilmenite and Cr-spinel within individual grains of pyrope. Sample INT-266 hosts intergrowth of crichtonite-group mineral and Cl-apatite, while sample INT-324 contains polymineralic apatite- and dolomite-bearing assemblages. Crichtonite-group minerals are Al-rich (1.1–4.5 wt% Al2O3), moderately Zr-enriched (1.3–4.3 wt% ZrO2), and are Ca-, Sr-, and occasionally Ba-dominant in terms of A-site occupancy; they also contain significant amounts of Na and LREE. T-estimates and chemical composition of Cr-pyropes imply that samples represent relatively low-T peridotite assemblages with ambient T ranging from 720 to 820°С. Projected onto the 35 mW/m2 cratonic paleogeotherm for the Mirny kimberlite field (Griffin et al., 1999b. Tectonophysics 310, 1–35), temperature estimates yield a P range of ~34–42 kbar (~110–130 km), which corresponds to a mantle domain in the uppermost part of the diamond stability field. The presence of crichtonite-group minerals in Cr-pyropes has petrological and geochemical implications as evidence for metasomatic enrichment of some incompatible elements in the lithospheric mantle beneath the Mirny kimberlite field. The genesis of Cr-pyropes with inclusions of crichtonite-group minerals is attributed to the percolation of Ca-Sr-Na-LREE-Zr-bearing carbonate-silicate metasomatic agents through Mg- and Cr-rich depleted peridotite protoliths. The findings of several potentially new members of the crichtonite group as inclusions in garnet extend existing knowledge on the compositions and occurrences of exotic titanates stable in the lithospheric mantle.

AB - Cr-pyrope xenocrysts and associated inclusions of crichtonite-group minerals from the Internatsionalnaya kimberlite pipe were studied to provide new insights into processes in the lithospheric mantle beneath the Mirny kimberlite field, Siberian craton. Pyropes are predominantly of lherzolitic paragenesis (Cr2O3 2–6 wt%) and have trace-element spectra typical for garnets from fertile mantle (gradual increase in chondrite-normalized values from LREE to MREE-HREE). Crichtonite-group minerals commonly occur as monomineralic elongated inclusions, mostly in association with rutile, Mg-ilmenite and Cr-spinel within individual grains of pyrope. Sample INT-266 hosts intergrowth of crichtonite-group mineral and Cl-apatite, while sample INT-324 contains polymineralic apatite- and dolomite-bearing assemblages. Crichtonite-group minerals are Al-rich (1.1–4.5 wt% Al2O3), moderately Zr-enriched (1.3–4.3 wt% ZrO2), and are Ca-, Sr-, and occasionally Ba-dominant in terms of A-site occupancy; they also contain significant amounts of Na and LREE. T-estimates and chemical composition of Cr-pyropes imply that samples represent relatively low-T peridotite assemblages with ambient T ranging from 720 to 820°С. Projected onto the 35 mW/m2 cratonic paleogeotherm for the Mirny kimberlite field (Griffin et al., 1999b. Tectonophysics 310, 1–35), temperature estimates yield a P range of ~34–42 kbar (~110–130 km), which corresponds to a mantle domain in the uppermost part of the diamond stability field. The presence of crichtonite-group minerals in Cr-pyropes has petrological and geochemical implications as evidence for metasomatic enrichment of some incompatible elements in the lithospheric mantle beneath the Mirny kimberlite field. The genesis of Cr-pyropes with inclusions of crichtonite-group minerals is attributed to the percolation of Ca-Sr-Na-LREE-Zr-bearing carbonate-silicate metasomatic agents through Mg- and Cr-rich depleted peridotite protoliths. The findings of several potentially new members of the crichtonite group as inclusions in garnet extend existing knowledge on the compositions and occurrences of exotic titanates stable in the lithospheric mantle.

KW - Crichtonite-group minerals

KW - Inclusion

KW - Kimberlite

KW - Mantle metasomatism

KW - Pyrope

KW - Siberian craton

KW - SUBCALCIC GARNET

KW - LITHOSPHERIC MANTLE

KW - DIAMOND

KW - ARMALCOLITE-BEARING

KW - PERIDOTITE XENOLITHS

KW - U-PB AGES

KW - QUANTITATIVE-ANALYSIS

KW - TRACE-ELEMENTS

KW - MAGMATISM BENEATH

KW - GARNET XENOCRYSTS

UR - http://www.scopus.com/inward/record.url?scp=85044121178&partnerID=8YFLogxK

U2 - 10.1016/j.lithos.2018.02.026

DO - 10.1016/j.lithos.2018.02.026

M3 - Article

AN - SCOPUS:85044121178

VL - 308

SP - 181

EP - 195

JO - Lithos

JF - Lithos

SN - 0024-4937

ER -