TY - JOUR

T1 - Origin of V. Grib pipe eclogites (Arkhangelsk region, NW Russia): geochemistry, Sm-Nd and Rb-Sr isotopes and relation to regional Precambrian tectonics

AU - Shchukina, Elena V.

AU - Agashev, Aleksey M.

AU - Soloshenko, Natalia G.

AU - Streletskaya, Mariya V.

AU - Zedgenizov, Dmitry A.

N1 - Publisher Copyright: © 2019, Springer-Verlag GmbH Austria, part of Springer Nature.

PY - 2019/10/1

Y1 - 2019/10/1

N2 - In this paper, new main and trace elements and isotopic data are presented for 14 coarse-grained eclogite xenoliths from the V. Grib kimberlite pipe in the central part of the Arkhangelsk Diamondiferous Province. Based on reconstructed whole rock MgO content, this suite is divided into high-MgO and low-MgO varieties. Eclogitic groups have a similar range of variations in the trace element compositions of garnet, clinopyroxene and reconstructed whole rock. All eclogites show positive Eu anomalies in garnet and Sr anomalies in the whole rock. The negative correlation between the Mg#, Sr/Lu ratio and HREE in a whole rock points to upper and lower oceanic crustal rocks as a protolith for eclogites with high and low whole rock HREEs, respectively. Low-MgO eclogites with higher whole rock HREEs have the basaltic upper oceanic crustal protolith, whereas the protoliths of eclogites with lower whole rock HREEs could be of gabbroic composition from the lower oceanic crust. High-MgO eclogites could represent MgO-rich portions of oceanic crustal rocks: picritic/MgO basalt portions in the upper oceanic crust and troctolite portions in the lower oceanic crust. The Sr and Nd isotope compositions suggest a complex history of eclogites during their residence in the lithospheric mantle. Similarities in the Nd isotope compositions and two-point Sm-Nd isochron ages are evidence for re-equilibration of the Sm-Nd isotope system between the eclogite garnet and clinopyroxene via a pre-kimberlite thermal event at 396 ± 24 Ma. The subset of clinopyroxenes from four eclogites has a Sr isotope composition that plots on the isochron at an age of 2.84 Ga, which reflects the time of the subduction event and emplacement into the lithosphere and corresponds to the time of the Belomorian Eclogite Province of Baltic Shield formation.

AB - In this paper, new main and trace elements and isotopic data are presented for 14 coarse-grained eclogite xenoliths from the V. Grib kimberlite pipe in the central part of the Arkhangelsk Diamondiferous Province. Based on reconstructed whole rock MgO content, this suite is divided into high-MgO and low-MgO varieties. Eclogitic groups have a similar range of variations in the trace element compositions of garnet, clinopyroxene and reconstructed whole rock. All eclogites show positive Eu anomalies in garnet and Sr anomalies in the whole rock. The negative correlation between the Mg#, Sr/Lu ratio and HREE in a whole rock points to upper and lower oceanic crustal rocks as a protolith for eclogites with high and low whole rock HREEs, respectively. Low-MgO eclogites with higher whole rock HREEs have the basaltic upper oceanic crustal protolith, whereas the protoliths of eclogites with lower whole rock HREEs could be of gabbroic composition from the lower oceanic crust. High-MgO eclogites could represent MgO-rich portions of oceanic crustal rocks: picritic/MgO basalt portions in the upper oceanic crust and troctolite portions in the lower oceanic crust. The Sr and Nd isotope compositions suggest a complex history of eclogites during their residence in the lithospheric mantle. Similarities in the Nd isotope compositions and two-point Sm-Nd isochron ages are evidence for re-equilibration of the Sm-Nd isotope system between the eclogite garnet and clinopyroxene via a pre-kimberlite thermal event at 396 ± 24 Ma. The subset of clinopyroxenes from four eclogites has a Sr isotope composition that plots on the isochron at an age of 2.84 Ga, which reflects the time of the subduction event and emplacement into the lithosphere and corresponds to the time of the Belomorian Eclogite Province of Baltic Shield formation.

KW - Arkhangelsk Diamondiferous Province

KW - Eclogite

KW - Kimberlite

KW - Sm-Nd and Rb-Sr isotopes

KW - Subduction

KW - KYANITE-ECLOGITE

KW - SOUTH-AFRICA

KW - UDACHNAYA KIMBERLITE PIPE

KW - XENOLITHIC ECLOGITES

KW - DIAMOND INCLUSIONS

KW - TRACE-ELEMENTS

KW - MANTLE ECLOGITES

KW - PALEOPROTEROZOIC SUBDUCTION

KW - SLAVE CRATON

KW - VICTOR-KIMBERLITE

UR - http://www.scopus.com/inward/record.url?scp=85068978706&partnerID=8YFLogxK

U2 - 10.1007/s00710-019-00679-7

DO - 10.1007/s00710-019-00679-7

M3 - Article

AN - SCOPUS:85068978706

VL - 113

SP - 593

EP - 612

JO - Mineralogy and Petrology

JF - Mineralogy and Petrology

SN - 0930-0708

IS - 5

ER -