TY - JOUR

T1 - Spinel-group minerals in peridotites of the guli and boruryakh intrusions (Meimecha-Kotuy Province, Northern Siberia)

AU - Chayka, Ivan

AU - Kamenetsky, Vadim

AU - Vasilyev, Yuriy

AU - Prokopyev, Ilya

N1 - Funding Information: The authors kindly thank Marina Gora and Maya Kamenetsky for the assistance in samples’ selection and preparation, and Karsten Goemann for assistance with SEM. The work was done on state assignment of IGM SB RAS, SEM analyses were financially supported by the grant of Russian Science Foundation #19-77-10004. Publisher Copyright: © 2020 International Multidisciplinary Scientific Geoconference. All rights reserved. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2020

Y1 - 2020

N2 - The Guli and Bor-Uryakh massifs, a part of the Siberian Large igneous province (LIP) are mafic-ultramafic intrusive complexes, with strong alkaline affinity. They contain deposits of apatite and are also known to be source rocks of Os-Ir-Ru placers. These massifs are of great interest for petrologists worldwide, as they are composed of an unusual variety of rocks (dunites/olivinites, shonkinites, melilitites, alkali syenites and carbonatites) and being coeval with Siberian trap volcanic rocks, including diamondiferous kimberlites. Since mineralogical approaches based on spinel-group minerals have been proved to be efficient in constraining origin of the ultramafics, we present the first descriptive study of chromite and magnetite mineralization, observed in olivine-dominated rocks of the Guli and Bor-Uryakh intrusions. In dunites of Guli massif spinel-group minerals are dominated by Mg-poor chromite (FeMg)Cr2O4 and Cr-Ti-rich magnetite FeFe2O4, while in Bor-Uryakh massif spinel-group minerals are predominantly magnetite with only minor Mg-poor chromite. These minerals form either small euhedral inclusions in olivine or large subhedral to anhedral grains in serpentinized fractures and interstitial space. The latter type of grains can have intricated irregular shape and contain inclusions. We also observed abundant Cr-magnetite lamellae in olivine and chromite/magnetite micro-grains within olivine-hosted multiphase inclusions. Spinel (MgAl2O4) is occasionally found in intergrowths with chromite and magnetite. The obtained data show that spinel-group minerals in the massifs do not correspond to primary-magmatic varieties and suggest extensive alteration during post-magmatic processes. Textural and chemical evidence of substantial modification of initially-cumulative lithologies of Guli and Bor-Uryakh massifs favors meta-magmatic origin for these massifs.

AB - The Guli and Bor-Uryakh massifs, a part of the Siberian Large igneous province (LIP) are mafic-ultramafic intrusive complexes, with strong alkaline affinity. They contain deposits of apatite and are also known to be source rocks of Os-Ir-Ru placers. These massifs are of great interest for petrologists worldwide, as they are composed of an unusual variety of rocks (dunites/olivinites, shonkinites, melilitites, alkali syenites and carbonatites) and being coeval with Siberian trap volcanic rocks, including diamondiferous kimberlites. Since mineralogical approaches based on spinel-group minerals have been proved to be efficient in constraining origin of the ultramafics, we present the first descriptive study of chromite and magnetite mineralization, observed in olivine-dominated rocks of the Guli and Bor-Uryakh intrusions. In dunites of Guli massif spinel-group minerals are dominated by Mg-poor chromite (FeMg)Cr2O4 and Cr-Ti-rich magnetite FeFe2O4, while in Bor-Uryakh massif spinel-group minerals are predominantly magnetite with only minor Mg-poor chromite. These minerals form either small euhedral inclusions in olivine or large subhedral to anhedral grains in serpentinized fractures and interstitial space. The latter type of grains can have intricated irregular shape and contain inclusions. We also observed abundant Cr-magnetite lamellae in olivine and chromite/magnetite micro-grains within olivine-hosted multiphase inclusions. Spinel (MgAl2O4) is occasionally found in intergrowths with chromite and magnetite. The obtained data show that spinel-group minerals in the massifs do not correspond to primary-magmatic varieties and suggest extensive alteration during post-magmatic processes. Textural and chemical evidence of substantial modification of initially-cumulative lithologies of Guli and Bor-Uryakh massifs favors meta-magmatic origin for these massifs.

KW - Chromite

KW - Cr-spinel

KW - Dunite

KW - Guli massif

KW - Maimecha-Kotuy province

KW - Siberian LIP

UR - http://www.scopus.com/inward/record.url?scp=85099738494&partnerID=8YFLogxK

U2 - 10.5593/sgem2020/1.1/s01.038

DO - 10.5593/sgem2020/1.1/s01.038

M3 - Conference article

AN - SCOPUS:85099738494

VL - 2020-August

SP - 301

EP - 308

JO - International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM

JF - International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM

SN - 1314-2704

IS - 1.1

T2 - 20th International Multidisciplinary Scientific Geoconference: Science and Technologies in Geology, Exploration and Mining, SGEM 2020

Y2 - 18 August 2020 through 24 August 2020

ER -