TY - JOUR

T1 - Mineralogy, geochemistry and U-Pb zircon age of the Karaotkel Ti-Zr placer deposit, Eastern Kazakhstan and its genetic link to the Karaotkel-Preobrazhenka intrusion

AU - Suiekpayev, Y. S.

AU - Sapargaliyev, Y. M.

AU - Dolgopolova, A. V.

AU - Pirajno, F.

AU - Seltmann, R.

AU - Khromykh, S. V.

AU - Bekenova, G. K.

AU - Kotler, P. D.

AU - Kravchenko, M. M.

AU - Azelkhanov, A. Zh

N1 - Funding Information: Authors express their gratitude and deep appreciation to the researchers of the Altai Geologic and Ecologic Institute, Oskemen for the materials provided for this study. Researchers of the Mineralogical Laboratory of the K.I. Satpayev Institute of Geological Sciences, Almaty and Laboratory of ?Analysis of metals? of the Al-Farabi Kazakh National University, Almaty are especially thanked for the assistance with the analyses. Authors also highly appreciate help and support of colleagues from the Centre for Russian and Central EurAsian Mineral Studies (CERCAMS), Natural History Museum, London, U.K. and V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia that allowed to achieve the goals of this research. The research was supported by the grant No. AR05134978 on ?Development of innovative technologies for the discovery of titanium-zirconium, rare and rare-earth placer deposits in the Zaysan depression in Eastern Kazakhstan? funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan. The research was carried out on a government assignment to the V.S. Sobolev Institute of Geology and Mineralogy (Novosibirsk). The work was supported by the Ministry of Science and Higher Education of the Russian Federation contract No. 14.Y26.31.0029 in the framework of the Resolution No.220 of the Government of the Russian Federation. This is a contribution to the International Geoscience Program (IGCP project #662) co-sponsored under the patronage of IUGS-UNESCO. The authors deeply appreciate the thorough review and critical comments of two peer-reviewers, of the handling Associate Editor Dr. Oliver Kreuzer, and the Editor-in-Chief Prof. Huayong Chen that helped to significantly improve the manuscript. Funding Information: Authors express their gratitude and deep appreciation to the researchers of the Altai Geologic and Ecologic Institute, Oskemen for the materials provided for this study. Researchers of the Mineralogical Laboratory of the K.I. Satpayev Institute of Geological Sciences, Almaty and Laboratory of “Analysis of metals” of the Al-Farabi Kazakh National University, Almaty are especially thanked for the assistance with the analyses. Authors also highly appreciate help and support of colleagues from the Centre for Russian and Central EurAsian Mineral Studies (CERCAMS), Natural History Museum, London, U.K. and V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia that allowed to achieve the goals of this research. The research was supported by the grant No. AR05134978 on “Development of innovative technologies for the discovery of titanium-zirconium, rare and rare-earth placer deposits in the Zaysan depression in Eastern Kazakhstan” funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan. The research was carried out on a government assignment to the V.S. Sobolev Institute of Geology and Mineralogy (Novosibirsk). The work was supported by the Ministry of Science and Higher Education of the Russian Federation contract No. 14.Y26.31.0029 in the framework of the Resolution No.220 of the Government of the Russian Federation. This is a contribution to the International Geoscience Program (IGCP project #662) co-sponsored under the patronage of IUGS-UNESCO. The authors deeply appreciate the thorough review and critical comments of two peer-reviewers, of the handling Associate Editor Dr. Oliver Kreuzer, and the Editor-in-Chief Prof. Huayong Chen that helped to significantly improve the manuscript. Publisher Copyright: © 2021 Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/4

Y1 - 2021/4

N2 - The Karaotkel deposit of fossil Ti-Zr placers is situated in the north-western edge of the Zaysan intermontane depression in Eastern Kazakhstan. The geological structure of the mineral sands is characterized by complex morphology and a two-layered assembly, formed as the result of long-term regional geodynamic processes during the Meso- and Cenozoic. Our study is aimed to establish a genetic model for the formation of the continental Karaotkel Ti-Zr placers by utilising novel data on geology, mineralogy, geochemistry and geochronology. Sedimentological facies analyses indicate an environment of coastal wave-built formation of the Late Cretaceous kaolin-dominated weathering crust and Paleogene sediments of the North Zaysan formation. A set of geochemical indices is applied on the base of key geochemical parameters of placer composition to allow quantitative and qualitative assessment and to establish genetic trends. Mineralogical composition of the heavy fraction of the productive sediments of the Ti-Zr placer (horizon “A” of the North Zaysan formation) was determined by XRD and microprobe-probe analyses. Microprobe analyses determined the elemental composition of mineral grains of zircon, ilmenite, monazite, staurolite, titanite, epidote and gold. Gold and monazite were found also as micro-inclusions in minerals. The sediments of the horizon “A” are characterized by elevated grades of light rare-earth elements (LREE) over heavy rare-earth elements (HREE). The weathering processes reveal a gradual transition from a moderately warm and humid climate to a cold and dry climate as the placer deposit was formed. The intercalations between horizontal- and crossbedding characterize the conditions of placers’ sedimentation by eluvial, eluvial-alluvial, alluvial-lacustrine and lacustrine environments. U-Pb dating of zircons from the productive horizon “A” of the Karaotkel placer deposit showed a crystallization age of 287 ± 1 Ma. This is identical with the age of the Karaotkel-Preobrazhenka multi-phase igneous intrusion suggesting that it can be considered as the source of the Karaotkel Ti-Zr placer. In addition, comparative analyses of elemental composition of zircons confirmed that monzonites and syenites of earlier phases of the Karaotkel-Preobrazhenka intrusion are the likely source rocks for the Karaotkel mineral sands. The formation of these Ti-Zr placers comprise the following stages: 1) establishment of the bedrock of the Karaotkel-Preobrazhenka multiphase igneous intrusion of the Permian Cisuralian epoch; 2) development of weathering crust during Upper Cretaceous period; 3) washing-out of the weathering crusts during the North Zaysan formation in the Paleogene, and 4) differential redeposition by temporary streams that resulted in the accumulation of Ti and Zr minerals.

AB - The Karaotkel deposit of fossil Ti-Zr placers is situated in the north-western edge of the Zaysan intermontane depression in Eastern Kazakhstan. The geological structure of the mineral sands is characterized by complex morphology and a two-layered assembly, formed as the result of long-term regional geodynamic processes during the Meso- and Cenozoic. Our study is aimed to establish a genetic model for the formation of the continental Karaotkel Ti-Zr placers by utilising novel data on geology, mineralogy, geochemistry and geochronology. Sedimentological facies analyses indicate an environment of coastal wave-built formation of the Late Cretaceous kaolin-dominated weathering crust and Paleogene sediments of the North Zaysan formation. A set of geochemical indices is applied on the base of key geochemical parameters of placer composition to allow quantitative and qualitative assessment and to establish genetic trends. Mineralogical composition of the heavy fraction of the productive sediments of the Ti-Zr placer (horizon “A” of the North Zaysan formation) was determined by XRD and microprobe-probe analyses. Microprobe analyses determined the elemental composition of mineral grains of zircon, ilmenite, monazite, staurolite, titanite, epidote and gold. Gold and monazite were found also as micro-inclusions in minerals. The sediments of the horizon “A” are characterized by elevated grades of light rare-earth elements (LREE) over heavy rare-earth elements (HREE). The weathering processes reveal a gradual transition from a moderately warm and humid climate to a cold and dry climate as the placer deposit was formed. The intercalations between horizontal- and crossbedding characterize the conditions of placers’ sedimentation by eluvial, eluvial-alluvial, alluvial-lacustrine and lacustrine environments. U-Pb dating of zircons from the productive horizon “A” of the Karaotkel placer deposit showed a crystallization age of 287 ± 1 Ma. This is identical with the age of the Karaotkel-Preobrazhenka multi-phase igneous intrusion suggesting that it can be considered as the source of the Karaotkel Ti-Zr placer. In addition, comparative analyses of elemental composition of zircons confirmed that monzonites and syenites of earlier phases of the Karaotkel-Preobrazhenka intrusion are the likely source rocks for the Karaotkel mineral sands. The formation of these Ti-Zr placers comprise the following stages: 1) establishment of the bedrock of the Karaotkel-Preobrazhenka multiphase igneous intrusion of the Permian Cisuralian epoch; 2) development of weathering crust during Upper Cretaceous period; 3) washing-out of the weathering crusts during the North Zaysan formation in the Paleogene, and 4) differential redeposition by temporary streams that resulted in the accumulation of Ti and Zr minerals.

KW - Continental placer

KW - Ilmenite

KW - Regolith

KW - Weathering crust

KW - Zaysan depression

KW - Zircon

UR - http://www.scopus.com/inward/record.url?scp=85100552829&partnerID=8YFLogxK

U2 - 10.1016/j.oregeorev.2021.104015

DO - 10.1016/j.oregeorev.2021.104015

M3 - Article

AN - SCOPUS:85100552829

VL - 131

JO - Ore Geology Reviews

JF - Ore Geology Reviews

SN - 0169-1368

M1 - 104015

ER -