Advanced Search

Indexed by SCI、CA、РЖ、PA、CSA、ZR、etc .

Volume 31 Issue 3
Jul.  2020
Turn off MathJax
Article Contents

Vasilii I. Leontev, Sergey G. Skublov, Nadezhda V. Shatova, Alexey V. Berezin. Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activation in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data. Journal of Earth Science, 2020, 31(3): 481-491. doi: 10.1007/s12583-020-1304-z
Citation: Vasilii I. Leontev, Sergey G. Skublov, Nadezhda V. Shatova, Alexey V. Berezin. Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activation in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data. Journal of Earth Science, 2020, 31(3): 481-491. doi: 10.1007/s12583-020-1304-z

Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activation in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data

doi: 10.1007/s12583-020-1304-z
More Information
  • The gold mineralization in the Central Aldan ore district is genetically related to potassic calc-alkaline and alkaline magmatism dated at 115-150 Ma. The objective of this study is to establish the age of hydrothermal processes that accompanied the formation of Au-Te mineralization at the Samolazovsky Deposit. Based on the isotope-geochemical study of zircons from quartz-feldspar metasomatic rocks of the deposit, the granitoids and charnokites of the Nimnyr Complex (1 900-1 960 Ma) at the contact with the Yukhta monzonite-syenite massif (~127 Ma) were studied. Zircon U-Pb dating was performed on a SHRIMP-II ion microprobe, and rare-earth and trace elements analyses of zircon were carried out in the same craters by secondary-ion mass spectrometry on a Cameca IMS-4f ion microprobe. It is revealed that the studied zircons have heterogeneous structures:dark core and lighter rim, which differ greatly in isotope-geochemical parameters. Zircon rims are cut by a network of fractures, extending into the central part of zircon grains. The rims yield a subconcordant age of 1 937±24 Ma, with an average total REE content of 550 ppm, which corresponds to the formation age of the Nimnyr Complex. All zircon cores yield a discordant age of 83±11 Ma and are characterized by a higher total REE content (~1 812 ppm), as well as higher contents of U and non-formula elements (Ca, Sr, and Y) with respect to rims, due to the effect of fluid on zircons. Despite the limited number of zircon grains, the additional geochronological study of zircons from syenites of the ore-bearing Ryabinovy Massif has revealed the presence of two distinct age clusters:~125-138 and 76-83 Ма. The older ages of zircons from syenites are typical for the Central Aldan ore district. Until now, there is still no explanation for an age range (76-83 Ma) of single zircon grains from ore-bearing syenites of the Ryabinovy Massif. The obtained data suggest that the processes of activation (the effect of fluid) within the Central Aldan ore district continued until Late Mesozoic. With regards to the equivocal geotectonic position of the Mesozoic potassic magmatism in the study area and its high metallogenic potential, there exists an absolute necessity to determine the geochronological age of the rock formations. Therefore this study presents the Late Cretaceous geochronological data for the first time which can constrain the time-frame for the formation of gold-bearing magmatic and metasomatic rocks of the Aldan ore district.
  • 加载中
  • Belousova, E., Griffin, W., O'Reilly, S. Y., et al., 2002. Igneous Zircon:Trace Element Composition as an Indicator of Source Rock Type. Contributions to Mineralogy and Petrology, 143(5):602-622. https://doi.org/10.1007/s00410-002-0364-7 doi:  10.1007/s00410-002-0364-7
    Black, L. P., Kamo, S. L., Allen, C. M., et al., 2003. TEMORA 1:A New Zircon Standard for Phanerozoic U-Pb Geochronology. Chemical Geology, 200(1/2):155-170. https://doi.org/10.1016/s0009-2541(03)00165-7 doi:  10.1016/s0009-2541(03)00165-7
    Borisenko, I. D., Borovikov, A. A., Borisenko, A. S., et al., 2017. Physicochemical Conditions of Ore Formation in the Samolazovskoe Gold Deposit (Central Aldan). Russian Geology and Geophysics, 58(12):1518-1529. https://doi.org/10.1016/j.rgg.2016.12.014 doi:  10.1016/j.rgg.2016.12.014
    Bröcker, M., Löwen, K., Rodionov, N., 2014. Unraveling Protolith Ages of Meta-Gabbros from Samos and the Attic-Cycladic Crystalline Belt, Greece:Results of a U-Pb Zircon and Sr-Nd Whole Rock Study. Lithos, 198/199:234-248. https://doi.org/10.1016/j.lithos.2014.03.029 doi:  10.1016/j.lithos.2014.03.029
    Dokukina, K. A., Kaulina, T. V., Konilov, A. N., et al., 2014. Archaean to Palaeoproterozoic High-Grade Evolution of the Belomorian Eclogite Province in the Gridino Area, Fennoscandian Shield:Geochronological Evidence. Gondwana Research, 25(2):585-613. https://doi.org/10.1016/j.gr.2013.02.014 doi:  10.1016/j.gr.2013.02.014
    Fedotova, A. A., Bibikova, E. V., Simakin, S. G., 2008. Ion-Microprobe Zircon Geochemistry as an Indicator of Mineral Genesis during Geochronological Studies. Geochemistry International, 46(9):912-927. https://doi.org/10.1134/s001670290809005x doi:  10.1134/s001670290809005x
    Fu, B., Mernagh, T. P., Kita, N. T., et al., 2009. Distinguishing Magmatic Zircon from Hydrothermal Zircon:A Case Study from the Gidginbung High-Sulphidation Au-Ag-(Cu) Deposit, SE Australia. Chemical Geology, 259(3/4):131-142. https://doi.org/10.1016/j.chemgeo.2008.10.035 doi:  10.1016/j.chemgeo.2008.10.035
    Geisler, T., Schleicher, H., 2000. Improved U-Th-Total Pb Dating of Zircons by Electron Microprobe Using a Simple New Background Modeling Procedure and Ca as a Chemical Criterion of Fluid-Induced U-Th-Pb Discordance in Zircon. Chemical Geology, 163(1/2/3/4):269-285. https://doi.org/10.1016/s0009-2541(99)00099-6 doi:  10.1016/s0009-2541(99)00099-6
    Glebovitskii, V. A., Sedova, I. S., Berezhnaya, N. G., et al., 2010. Isotope-Geochronological Timing of Metamorphic Events in the Boundary Zone between the Aldan Shield and the Dzhugdzhuro-Stanovoi Folded Area. Doklady Earth Sciences, 430(1):34-39. https://doi.org/10.1134/s1028334x10010071 doi:  10.1134/s1028334x10010071
    Glebovitskii, V. A., Sedova, I. S., Berezhnaya, N. G., et al., 2012a. U-Pb Age of Autochthonous Paleoproterozoic Charnockite in the Aldan Shield. Doklady Earth Sciences, 443(2):451-457. https://doi.org/10.1134/s1028334x12040198 doi:  10.1134/s1028334x12040198
    Glebovitskii, V. A., Sedova, I. S., Berezhnaya, N. G., et al., 2012b. New Data on the Age of Ultrametamorphic Granitoids of the Aldan Granulite Area (Eastern Siberia), Consequences of Metamorphic Processes and Possibilities of Regional Correlations of Geological Events. Stratigraphy and Geological Correlation, 20(2):139-165. https://doi.org/10.1134/s0869593812020049 doi:  10.1134/s0869593812020049
    Hinton, R. W., Upton, B. G. J., 1991. The Chemistry of Zircon:Variations within and between Large Crystals from Syenite and Alkali Basalt Xenoliths. Geochimica et Cosmochimica Acta, 55(11):3287-3302. https://doi.org/10.1016/0016-7037(91)90489-r doi:  10.1016/0016-7037(91)90489-r
    Jiang, W. C., Li, H., Evans, N. J., et al., 2019. Zircon Records Multiple Magmatic-Hydrothermal Processes at the Giant Shizhuyuan W-Sn-Mo-Bi Polymetallic Deposit, South China. Ore Geology Reviews, 115:103160. https://doi.org/10.1016/j.oregeorev.2019.103160 doi:  10.1016/j.oregeorev.2019.103160
    Jochum, K. P., Dingwell, D. B., Rocholl, A., et al., 2000. The Preparation and Preliminary Characterisation of Eight Geological MPI-DING Reference Glasses for in-situ Microanalysis. Geostandards and Geoanalytical Research, 24(1):87-133. https://doi.org/10.1111/j.1751-908x.2000.tb00590.x doi:  10.1111/j.1751-908x.2000.tb00590.x
    Jochum, K. P., Stoll, B., Herwig, K., et al., 2006. MPI-DING Reference Glasses for in situ Microanalysis:New Reference Values for Element Concentrations and Isotope Ratios. Geochemistry, Geophysics, Geosystems, 7(2). https://doi.org/10.1029/2005gc001060 doi:  10.1029/2005gc001060
    Kazansky, V. I., 2004. The Unique Central Aldan Gold-Uranium Ore District (Russia). Geology of Ore Deposits, 46:167-181
    Khomich, V. G., Boriskina, N. G., Santosh, M., 2014. A Geodynamic Perspective of World-Class Gold Deposits in East Asia. Gondwana Research, 26(3/4):816-833. https://doi.org/10.1016/j.gr.2014.05.007 doi:  10.1016/j.gr.2014.05.007
    Khomich, V. G., Boriskina, N. G., Santosh, M., 2015. Geodynamics of Late Mesozoic PGE, Au, and U Mineralization in the Aldan Shield, North Asian Craton. Ore Geology Reviews, 68:30-42. https://doi.org/10.1016/j.oregeorev.2015.01.007 doi:  10.1016/j.oregeorev.2015.01.007
    Kononova, V. A., Pervov, V. A., Bogatikov, O. A., et al., 1995. Mesozoic Potassium-Rich Magmatism of the Central Aldan:Geodynamics and Genesis. Geotectonics, 3:35-45
    Kukuschkin, K. A., Molchanov, A. V., Radkov, V. V., et al., 2015. Towards Differentiation of the Mesozoic Intrusive Rocks in the Central Aldan District (South Yakutia). Regional Geology and Metallogeny, 64:48-58 (in Russian)
    Leontev, V. I., Bushuev, Y. Y., 2017. Ore Mineralization in Adular-Fluorite Metasomatites:Evidence of the Podgolechnoe Alkalic-Type Epithermal Gold Deposit (Central Aldan Ore District, Russia). Key Engineering Materials, 743:417-421. https://doi.org/10.4028/www.scientific.net/kem.743.417 doi:  10.4028/www.scientific.net/kem.743.417
    Leontev, V. I., Bushuev, Y. Y., Chernigovtsev, K. A., 2018. Samolazovskoe Gold Deposit (Central Aldan Ore District):Geological Structure and Mineralization of Deep Horizons. Regional Geology and Metallogeny, 75:90-103 (in Russian)
    Leontev, V. I., Chernigovtsev, K., 2018. Ore Mineralization of the Epithermal Samolazovskoe Gold-Ore Deposit, Aldan Shield (Russia). Key Engineering Materials, 769:213-219. https://doi.org/10.4028/www.scientific.net/kem.769.213 doi:  10.4028/www.scientific.net/kem.769.213
    Li, G. M., Qin, K. Z., Li, J. X., et al., 2017. Cretaceous Magmatism and Metallogeny in the Bangong-Nujiang Metallogenic Belt, Central Tibet:Evidence from Petrogeochemistry, Zircon U-Pb Ages, and Hf-O Isotopic Compositions. Gondwana Research, 41:110-127. https://doi.org/10.1016/j.gr.2015.09.006 doi:  10.1016/j.gr.2015.09.006
    Li, H., Li, J. W., Algeo, T. J., et al., 2018a. Zircon Indicators of Fluid Sources and Ore Genesis in a Multi-Stage Hydrothermal System:The Dongping Au Deposit in North China. Lithos, 314/315:463-478. https://doi.org/10.1016/j.lithos.2018.06.025 doi:  10.1016/j.lithos.2018.06.025
    Li, H., Myint, A. Z., Yonezu, K., et al., 2018b. Geochemistry and U-Pb Geochronology of the Wagone and Hermyingyi A-Type Granites, Southern Myanmar:Implications for Tectonic Setting, Magma Evolution and Sn-W Mineralization. Ore Geology Reviews, 95:575-592. https://doi.org/10.1016/j.oregeorev.2018.03.015 doi:  10.1016/j.oregeorev.2018.03.015
    Li, H., Wu, J. H., Evans, N. J., et al., 2018c. Zircon Geochronology and Geochemistry of the Xianghualing A-Type Granitic Rocks:Insights into Multi-Stage Sn-Polymetallic Mineralization in South China. Lithos, 312/313:1-20. https://doi.org/10.1016/j.lithos.2018.05.001 doi:  10.1016/j.lithos.2018.05.001
    Li, H., Cao, J. Y., Algeo, T. J., et al., 2019a. Zircons Reveal Multi-Stage Genesis of the Xiangdong (Dengfuxian) Tungsten Deposit, South China. Ore Geology Reviews, 111:102979. https://doi.org/10.1016/j.oregeorev.2019.102979 doi:  10.1016/j.oregeorev.2019.102979
    Li, H., Sun, H. S., Algeo, T. J., et al., 2019b. Mesozoic Multi-Stage W-Sn Polymetallic Mineralization in the Nanling Range, South China:An Example from the Dengfuxian-Xitian Ore Field. Geological Journal, 54(6):3755-3785. https://doi.org/10.1002/gj.3369 doi:  10.1002/gj.3369
    Li, H., Sun, H. S., Evans, N. J., et al., 2019c. Geochemistry and Geochronology of Zircons from Granite-Hosted Gold Mineralization in the Jiaodong Peninsula, North China:Implications for Ore Genesis. Ore Geology Reviews, 115:103188. https://doi.org/10.1016/j.oregeorev.2019.103188 doi:  10.1016/j.oregeorev.2019.103188
    Li, H., Zhou, Z. K., Evans, N. J., et al., 2019d. Fluid-Zircon Interaction during Low-Temperature Hydrothermal Processes:Implications for the Genesis of the Banxi Antimony Deposit, South China. Ore Geology Reviews, 114:103137. https://doi.org/10.1016/j.oregeorev.2019.103137 doi:  10.1016/j.oregeorev.2019.103137
    Ludwig, K. R., 2001. SQUID 1.02, A User Manual, A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center Spec. Publ., Berkeley
    Ludwig, K. R., 2003. Userʼs Manual for Isoplot/Ex, Version 3.00, A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center Spec. Publ., Berkeley
    Maximov, E. P., Uyutov, V. I., Nikitin, V. M., 2010. The Central Aldan Gold-Uranium Ore Magmatogenic System, Aldan-Stanovoy Shield, Russia. Russian Journal of Pacific Geology, 4(2):95-115. https://doi.org/10.1134/s1819714010020016 doi:  10.1134/s1819714010020016
    McDonough, W. F., Sun, S. S., 1995. The Composition of the Earth. Chemical Geology, 120(3/4):223-253. https://doi.org/10.1016/0009-2541(94)00140-4 doi:  10.1016/0009-2541(94)00140-4
    Page, F. Z., Fu, B., Kita, N. T., et al., 2007. Zircons from Kimberlite:New Insights from Oxygen Isotopes, Trace Elements, and Ti in Zircon Thermometry. Geochimica et Cosmochimica Acta, 71(15):3887-3903. https://doi.org/10.1016/j.gca.2007.04.031 doi:  10.1016/j.gca.2007.04.031
    Pelleter, E., Cheilletz, A., Gasquet, D., et al., 2007. Hydrothermal Zircons:A Tool for Ion Microprobe U-Pb Dating of Gold Mineralization (Tamlalt-Menhouhou Gold Deposit-Morocco). Chemical Geology, 245(3/4):135-161. https://doi.org/10.1016/j.chemgeo.2007.07.026 doi:  10.1016/j.chemgeo.2007.07.026
    Polin, V. F., Glebovitskii, V. A., Mitsuk, V. V., et al., 2014. Two-Stage Formation of the Alcaline Volcano-Plutonic Complexes in the Ketkap-Yuna Igneous Province of the Aldan Shield:New Isotopic Data. Doklady Earth Sciences, 459(1):1322-1327. https://doi.org/10.1134/s1028334x14110051 doi:  10.1134/s1028334x14110051
    Polin, V. F., Mitsuk, V. V., Khanchuk, A. I., et al., 2012. Geochronological Limits of Subalkaline Magmatism in the Ket-Kap-Yuna Igneous Province, Aldan Shield. Doklady Earth Sciences, 442(1):17-23. https://doi.org/10.1134/s1028334x12010096 doi:  10.1134/s1028334x12010096
    Prokopyev, I. R., Doroshkevich, A. G., Ponomarchuk, A. V., et al., 2019. U-Pb SIMS and Ar-Ar Geochronology, Petrography, Mineralogy and Gold Mineralization of the Late Mesozoic Amga Alkaline Rocks (Aldan Shield, Russia). Ore Geology Reviews, 109:520-534. https://doi.org/10.1016/j.oregeorev.2019.05.011 doi:  10.1016/j.oregeorev.2019.05.011
    Prokopyev, I. R., Kravchenko, A. A., Ivanov, A. I., et al., 2018. Geochronology and Ore Mineralization of the Dzheltula Alkaline Massif (Aldan Shield, South Yakutia). Russian Journal of Pacific Geology, 12(1):34-45. https://doi.org/10.1134/s1819714018010062 doi:  10.1134/s1819714018010062
    Rocholl, A. B. E., Simon, K., Jochum, K. P., et al., 1997. Chemical Characterisation of NIST Silicate Glass Certified Reference Material SRM 610 by ICP-MS, TIMS, LIMS, SSMS, INAA, AAS and PIXE. Geostandards Newsletter, 21(1):101-114. https://doi.org/10.1111/j.1751-908x.1997.tb00537.x doi:  10.1111/j.1751-908x.1997.tb00537.x
    Rodionov, N. V., Belyatsky, B. V., Antonov, A. V., et al., 2012. Comparative in-situ U-Th-Pb Geochronology and Trace Element Composition of Baddeleyite and Low-U Zircon from Carbonatites of the Palaeozoic Kovdor Alkaline-Ultramafic Complex, Kola Peninsula, Russia. Gondwana Research, 21(4):728-744. https://doi.org/10.1016/j.gr.2011.10.005 doi:  10.1016/j.gr.2011.10.005
    Rodionov, S. M., Fredericksen, R. S., Berdnikov, N. V., et al., 2014. The Kuranakh Epithermal Gold Deposit (Aldan Shield, East Russia). Ore Geology Reviews, 59:55-65. https://doi.org/10.1016/j.oregeorev.2013.12.004 doi:  10.1016/j.oregeorev.2013.12.004
    Schaltegger, U., 2007. Hydrothermal Zircon. Elements, 3(1):51-79. https://doi.org/10.2113/gselements.3.1.51 doi:  10.2113/gselements.3.1.51
    Shatov, V. V., Molchanov, A. V., Shatova, N. V., et al., 2012. Petrography, Geochemistry and Isotopic (U-Pb and Rb-Sr) Dating of Alkaline Magmatic Rocks of the Ryabinovy Massif (South Yakutia). Regional Geology and Metallogeny, 51:62-78 (in Russian)
    Shatova, N. V., Skublov, S. G., Melnik, А. Е., et al., 2017. Geochronology of Alkaline Magmatic Rocks and Metasomatites of the Ryabinovy Stock (South Yakutia) Based on Zircon Isotopic and Geochemical (U-Pb, REE) Investigations. Regional Geology and Metallogeny, 69:33-48 (in Russian)
    Skublov, S. G., Berezin, A. V., Berezhnaya, N. G., 2012. General Relations in the Trace-Element Composition of Zircons from Eclogites with Implications for the Age of Eclogites in the Belomorian Mobile Belt. Petrology, 20(5):427-449. https://doi.org/10.1134/s0869591112050062 doi:  10.1134/s0869591112050062
    Soloviev, S. G., 2014. The Metallogeny of Shoshonitic Magmatism. Vol. 2. Scientific World, Moscow. 472 (in Russian)
    Terekhov, A. V., Molchanov, A. V., Shatov, V. V., et al., 2013. Fluid Characteristic of Formation Ore-Bearing Alteration Rocks of Elkon Gold-Uranium Ore Cluster. Journal of Mining Institute, 200:321-326
    Ushikubo, T., Kita, N. T., Cavosie, A. J., et al., 2008. Lithium in Jack Hills Zircons:Evidence for Extensive Weathering of Earthʼs Earliest Crust. Earth and Planetary Science Letters, 272(3/4):666-676. https://doi.org/10.1016/j.epsl.2008.05.032 doi:  10.1016/j.epsl.2008.05.032
    Vetluzhskikh, V. G., Kazansky, V. I., Kochetkov, A. Y., et al., 2002. Central Aldan Gold Deposits. Geology of Ore Deposits, 44:405-434 http://d.old.wanfangdata.com.cn/NSTLQK/NSTL_QKJJ027044372/
    Wang, Y., He, H. Y., Ivanov, A. V., et al., 2014. Age and Origin of Charoitite, Malyy Murun Massif, Siberia, Russia. International Geology Review, 56(8):1007-1019. https://doi.org/10.1080/00206814.2014.914860 doi:  10.1080/00206814.2014.914860
    Watson, E. B., Wark, D. A., Thomas, J. B., 2006. Crystallization Thermometers for Zircon and Rutile. Contributions to Mineralogy and Petrology, 151(4):413-433. https://doi.org/10.1007/s00410-006-0068-5 doi:  10.1007/s00410-006-0068-5
    Wiedenbeck, M., Allé, P., Corfu, F., et al., 1995. Three Natural Zircon Standards for U-Th-Pb, Lu-Hf, Trace Element and REE Analyses. Geostandards Newsletter, 19(1):1-23. https://doi.org/10.1111/j.1751-908x.1995.tb00147.x doi:  10.1111/j.1751-908x.1995.tb00147.x
    Williams, I. S., McKibben, M. A., Shanks, W. C. III, et al., 1998. U-Th-Pb Geochronology by Ion Microprobe. In: Applications of Microanalytical Techniques to Understanding Mineralizing Processes. Reviews of Economic Geology, 7: 1-35
    Yang, W. B., Niu, H. C., Shan, Q., et al., 2014. Geochemistry of Magmatic and Hydrothermal Zircon from the Highly Evolved Baerzhe Alkaline Granite:Implications for Zr-REE-Nb Mineralization. Mineralium Deposita, 49(4):451-470. https://doi.org/10.1007/s00126-013-0504-1 doi:  10.1007/s00126-013-0504-1
    Yarmolyuk, V. V., Nikiforov, A. V., Kozlovsky, A. M., et al., 2019. Late Mesozoic East Asian Magmatic Province:Structure, Magmatic Signature, Formation Conditions. Geotectonics, 53(4):500-516. https://doi.org/10.1134/s0016852119040071 doi:  10.1134/s0016852119040071
    Zhang, L., Zhu, J. J., Xia, B., et al., 2019. Metamorphism and Zircon Geochronological Studies of Metagabbro Vein in the Yushugou Granulite-Peridotite Complex from South Tianshan, China. Journal of Earth Science, 30(6):1215-1229. https://doi.org/10.1007/s12583-019-1254-5 doi:  10.1007/s12583-019-1254-5
    Zorin, Y. A., Turutanov, E. K., 2005. Plumes and Geodynamics of the Baikal Rift Zone. Russian Geology and Geophysics, 46:685-699
  • 加载中
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Figures(5)  / Tables(2)

Article Metrics

Article views(47) PDF downloads(4) Cited by()

Related
Proportional views

Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activation in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data

doi: 10.1007/s12583-020-1304-z
    Corresponding author: Vasilii I. Leontev, ORCID:0000-0001-7183-4772.E-mail:vsllntv@gmail.com

Abstract: The gold mineralization in the Central Aldan ore district is genetically related to potassic calc-alkaline and alkaline magmatism dated at 115-150 Ma. The objective of this study is to establish the age of hydrothermal processes that accompanied the formation of Au-Te mineralization at the Samolazovsky Deposit. Based on the isotope-geochemical study of zircons from quartz-feldspar metasomatic rocks of the deposit, the granitoids and charnokites of the Nimnyr Complex (1 900-1 960 Ma) at the contact with the Yukhta monzonite-syenite massif (~127 Ma) were studied. Zircon U-Pb dating was performed on a SHRIMP-II ion microprobe, and rare-earth and trace elements analyses of zircon were carried out in the same craters by secondary-ion mass spectrometry on a Cameca IMS-4f ion microprobe. It is revealed that the studied zircons have heterogeneous structures:dark core and lighter rim, which differ greatly in isotope-geochemical parameters. Zircon rims are cut by a network of fractures, extending into the central part of zircon grains. The rims yield a subconcordant age of 1 937±24 Ma, with an average total REE content of 550 ppm, which corresponds to the formation age of the Nimnyr Complex. All zircon cores yield a discordant age of 83±11 Ma and are characterized by a higher total REE content (~1 812 ppm), as well as higher contents of U and non-formula elements (Ca, Sr, and Y) with respect to rims, due to the effect of fluid on zircons. Despite the limited number of zircon grains, the additional geochronological study of zircons from syenites of the ore-bearing Ryabinovy Massif has revealed the presence of two distinct age clusters:~125-138 and 76-83 Ма. The older ages of zircons from syenites are typical for the Central Aldan ore district. Until now, there is still no explanation for an age range (76-83 Ma) of single zircon grains from ore-bearing syenites of the Ryabinovy Massif. The obtained data suggest that the processes of activation (the effect of fluid) within the Central Aldan ore district continued until Late Mesozoic. With regards to the equivocal geotectonic position of the Mesozoic potassic magmatism in the study area and its high metallogenic potential, there exists an absolute necessity to determine the geochronological age of the rock formations. Therefore this study presents the Late Cretaceous geochronological data for the first time which can constrain the time-frame for the formation of gold-bearing magmatic and metasomatic rocks of the Aldan ore district.

Vasilii I. Leontev, Sergey G. Skublov, Nadezhda V. Shatova, Alexey V. Berezin. Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activation in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data. Journal of Earth Science, 2020, 31(3): 481-491. doi: 10.1007/s12583-020-1304-z
Citation: Vasilii I. Leontev, Sergey G. Skublov, Nadezhda V. Shatova, Alexey V. Berezin. Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activation in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data. Journal of Earth Science, 2020, 31(3): 481-491. doi: 10.1007/s12583-020-1304-z
  • The central Aldan ore district is the unique ore-bearing structure with Au and U resources of ~1 000 and 600 000 tons, respectively (Kazansky, 2004). The economic gold mineralization in the central Aldan ore district is divided into several types: Lebedinsky-type (Au) (Vetluzhskikh et al., 2002), Kuranakh-type (Au) (Rodionov et al., 2014; Vetluzhskikh et al., 2002), Cu-Au porphyry (Shatova et al., 2017; Shatov et al., 2012; Vetluzhskikh, 2002), Au-Te epithermal (Leontev and Chernigovtsev, 2018; Leontev et al., 2018; Leontev and Bushuev, 2017), and Elkon-type (Au-U) (Terekhov et al., 2013; Kazansky, 2004). The ore mineralization in the central Aldan ore district, which forms part of the large Aldan igneous province, recognized within the Aldan Shield of the Siberian Craton, is spatially and genetically associated with the Mesozoic potassic calc-alkaline and alkaline magmatism (Yarmolyuk et al., 2019). Based on the K-Ar age dates, the age of magmatism which was determined within the Aldan igneous province falls within the range of 100–175 Ma (Maximov et al., 2010; Kononova et al., 1995). Further chronological studies included the use of zircon (U-Pb) and amphibole (Ar-Ar) dating which yielded ages of 115–150 Ma (Prokopyev et al., 2019, 2018; Shatova et al., 2017; Kukuschkin et al., 2015; Polin et al., 2014, 2012; Wang et al., 2014; Shatov et al., 2012). The late occurrence of magmatism, observed in the Ket-Kap-Yuna igneous province of the Aldan Shield, is confined within the age range of 86.6–87.4 Ma (Polin et al., 2014).

    There are different models, which enable the features of the Mesozoic potassic magmatism within the Aldan Shield to be well explained. Many researchers suggested that the magmatism was associated with the continental margin during Mesozoic. Moreover, in some works (Khomich et al., 2015, 2014; Zorin and Turutanov, 2005) this magmatic event is ascribed to the stopping of an oceanic plate at the mantle level, which caused the formation of local mantle diapirs. Other researchers considered the magmatism as a product of dehydration of a subducting oceanic plate and partial melting of a metasomatized mantle wedge, which is confirmed by compositional features of igneous rocks (Maximov et al., 2010; Kononova et al., 1995). In addition, some researchers suggested that the development of magmatism in the area was associated with a more complex geodynamic setting due to the interaction of the convergent margin with an intraplate mantle plume (Yarmolyuk et al., 2019; Soloviev, 2014). At present, there is no unambiguous model of the magmatic-evolution in the study area, due to, apparently, its integrated nature. In order to develop such a model, a comprehensive petrological investigation, including geochemical and isotope-geochronological studies, needs to be performed at the modern scientific and technical level.

    With regards to the equivocal geotectonic position of the Mesozoic potassic magmatism in the study area and its high metallogenic potential, there exists an absolute necessity to determine the geochronological age of the rock formations. The present study is therefore attempting to get the geochronological data which can constrain the time frame for the formation of gold-bearing magmatic and metasomatic rocks of the Aldan ore district.

  • The central Aldan ore district (Fig. 1a) is located on the Aldan Shield—the crystalline basement uplift within the ancient Siberian Craton. The lower level (i.e., crystalline basement) is composed of the Paleoarchean to Neoarchean and Paleoproterozoic magmatic, metamorphic, and ultrametamorphic complexes. The upper level (platform cover) is composed of Vendian–Lower Cambrian carbonate and Jurassic terrigenous rocks (Vetluzhskikh et al., 2002).

    Figure 1.  Samolazovskoe and Ryabinovoe gold deposits. (a) Regional geological map of the central Aldan ore district (modified after Maximov et al., 2010); (b) cross section of the Ryabinovoe Gold Deposit; (c) cross section of the Yukhta intrusive massif; and (d) cross section of the Samolazovskoe Gold Deposit.

    The formation of the ring structure, which is superimposed on the crystalline basement and the thin platform cover, is associated with the Mesozoic tectonomagmatic activation. At this stage, the development of new fault zones and rejuvenation of ancient ones took place, which controlled intrusion of magmatic bodies of alkaline syenite, monzonite-syenite, fergusite-dunite complexes. The most common morphology of magmatic rock bodies are plutonic stocks, sills and dikes; necks, diatremes, and subvolcanic bodies are less common (Maximov et al., 2010).

    The Ryabinovoe Au-Cu-porphyry deposit is confined within the Ryabinovy intrusive massif. The latter is composed of gneisses and granitic-gneisses of the crystalline basement (AR-PR) intruded by aegirine-augite syenites, syenite-porphyries and quartz syenites (142–144 Ma). Further, they were later intruded by alkaline gabbroids, monzonites, minettes and explosive breccias within the lamproite matrix (130–141 Ma) (Shatov et al., 2012). The stockwork-disseminated ore mineralization is confined within the sites of a two-stage metasomatic process: (1) pre-ore high-temperature aegirine-microcline-albite metasomatic rocks; (2) ore-bearing carbonate-muscovite-orthoclase and quartz-carbonate-barite-adular metasomatic rocks (Shatova et al., 2017). Samples (MT-60 and MT-61) of ore-bearing fluid-altered alkaline rocks of the Ryabinovoe Deposit were studied (Fig. 1b).

    The Samolazovskoe Deposit, which belongs to the Au-Te epithermal type, is located in the central part of the Yukhta intrusive massif. The latter represents Late Mesozoic age (J3–K1); the U-Pb age of the latest magmatic bodies of explosive breccia with syenite porphyry cement is 127 Ma (Borisenko et al., 2017). The deposit is represented by a variety of the following rock types: poorly defined metamorphic and intrusive complexes of the crystalline basement, represented by granites, granitic-gneisses, and arfvedsonite granitic-gneisses (AR-PR); quartz syenite porphyry and monzodiorite porphyry (J3–K1); and dolomite marbles developed in a contact zone between Mesozoic intrusive formations and Vendian– Cambrian dolomites of the sedimentary cover (Fig. 1c). In total, there are four types of hydrothermal alteration assemblages, and these include: (1) high-temperature quartz-feldspar metasomatic rocks which is superimposed on crystalline basement rocks in the contact zone with intrusive bodies; (2) skarn (diopside+ phlogopite+tremolite+wollastonite+carbonate+quartz), developed in the contact zone between syenites and carbonate rocks of the sedimentary cover; (3) potassic (K-feldspar+phlogopite+ carbonates+fluorite±quartz) alteration, which is superimposed on rocks of an intrusive massif; (4) ore-bearing phyllic alteration, represented by rocks with roscoelite, carbonates, fluorite, adular, and quartz, superimposed on all of the above-mentioned rocks. On the basis of structural and textural features including conditions of occurrence, three types of precious metals of the ore mineralization were distinguished: (1) stratiform-disseminated mineralization, (2) stock-work-disseminated mineralization, and lastly (3) vein and breccia-like rich ores (Fig. 1d) (Leontev et al., 2018). This work is based on the study of the originally drilled core samples of quartz-feldspar metasomatic rock with superimposed ore-bearing phyllic hydrothermal-metasomatic mineral association, collected by the authors from drill hole-9507 at a depth of 178.6 m (sample 9507/178.6, Figs. 1d, 2).

    Figure 2.  Hand specimen and photomicrographs of the quartz-feldspar metasomatic rocks. Hand specimen: (a) quartz-feldspar metasomatic rocks; (b) superimposed on quartz-feldspar metasomatic rocks the phyllic ore bearing alteration. Thin section photomicrographs under microscope: (c) quartz-feldspar metasomatic rocks (cross-polarized light); (d) and (f) superimposed on quartz-feldspar metasomatic rocks the phyllic ore bearing alteration assemblages with relict zircon, (d) plane polarized light, (f) cross-polarized light. Qz. Quartz; Fsp. feldspar; Cal. calcite; Ap. apatite; Zrn. zircon; Adl. adularia; Py. pyrite; Ros. roscoelite.

  • The zircon grains used in our study were extracted by the standard heavy liquid and magnetic separation techniques at the Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences. Zircon grains were hand-picked from separates under a binocular microscope, then placed together with grains of TEMORA and 91500 zircon standards into a form which was filled with epoxy resin and polished to expose approximately half grain thickness. A total of 32 zircons were collected from quartz-feldspar metasomatic rocks of the Samolazovskoe Deposit (sample 9507/178.6). To minimize the influence of cracks and inclusions, spots were selected for in-situ analysis of zircons taking into consideration transmitted and reflected light images. Cathodoluminescence (CL) and back-scattered-electron (BSE) images were carried out on a Camscan MX2500S SEM equipped with a QLI/QUA2 CL detector at the Centre of Isotopic Research of the All-Russian Geological Research Institute, St. Petersburg. Operating conditions for the SEM were 12 kV, a beam current of 5–7 nA. The combined CL and BSE images that reveal the internal structure and zoning of zircons were used to choose the optimum target areas for our research of the most representative zircons with rims of size suitable for a local U-Pb SIMS analysis.

    The U-Pb dating of zircons was performed on a SHRIMP-II ion microprobe at the Centre of Isotopic Research of the All-Russian Geological Research Institute, St. Petersburg. The U-Th-Pb measurements were carried out by the procedure described by Williams et al. (1998), Rodionov et al. (2012), Bröcker et al. (2014). The intensity of primary O2- beam was 4 nA, and the spot (crater) was 25 μm across. Zircon Temora (Black et al., 2003) was measured as the main reference material (RM): one per every 3 analyses of unknowns to obtain their U/Pb ratios. One RM point analysis of zircon 91500 (Wiedenbeck et al., 1995) was also carried out (81.2 ppm of U content). Differential fractionation between U and Pb was monitored by reference to a 206Pb/238U ratio of 0.066 8 for interspersed analyses of the Temora zircon standard (416.8±0.3 Ma), based on the logarithmic law relationship 206Pb+/U+ versus UO+/U+. The observed slope of calibration line was 1.96 that is close to theoretical value of 2. Common lead correction was done based on the measured 204Pb/206Pb ratio. Portion of common lead in 206Pb was less than 0.6% for analyses of RMs. Therefore Temora ages of total 11 analyses had low scatter characterized by error in standard callibration of 0.7%.

    The obtained raw U-Pb data were processed using the SQUID program (Ludwig, 2001). The concordia plots were constructed using the ISOPLOT/EX software (Ludwig, 2003).

    Rare-earth and trace elements analyses in the zircons were carried out in the same craters by secondary-ion mass spectrometry on a Cameca IMS-4f ion microprobe at the Yaroslavl Branch of the Institute of Physics and Technology of Russian Academy of Sciences, Yaroslavl. Analytical and data processing techniques were used as described in Hinton and Upton (1991), Fedotova et al. (2008), Dokukina et al. (2014). For analytical purpose, the primary O2- ion beam was focused to a spot size of ~20–25 μm. Each analysis was averaged from 3 cycles of measurements. Concentrations of trace elements were calculated from the normalized to 30Si+ secondary ion intensities using calibration curves based on a set of reference glasses (Jochum et al., 2006, 2000). NIST-610 reference glass (Rocholl et al., 1997) was used as a daily monitor for trace element analyses. Accuracy of the trace element measurements is up to 10% for concentrations higher than 1 ppm and up to 20% for the concentration range of 0.1 ppm–1 ppm, respectively.

    To construct REE distribution spectra, the composition of zircon was normalized to that of chondrite СI (McDonough and Sun, 1995). Zircon crystallization temperature was estimated with a Ti-in-zircon thermometer (Watson et al., 2006).

  • Zircon from quartz-feldspar metasomatic rocks of the Samolazovskoe Deposit (sample 9507/178.6) is characterized by rounded isometric shapes; and attains 100 µm in diameter. A distinctive feature of zircon is heterogeneous internal structure, which is clearly seen in CL image (Fig. 3). In fact, almost every grain of zircon constitute of a core that occupies about 30% to 80% of the grain cross-sectional area. Typically, the cores are dark, locally black, in СL image and highly fractured. Some cores are characterized by a lighter shade and diffused fine growth oscillation zonation (for example, points 3.1, 4.1 and 8.1). In turn, such dark gray areas in the CL images, on the outer shell of the core are replaced by dark fractured areas (for example, points 7.1 and 7.2).

    Figure 3.  Cathodoluminescent (CL) photomicrographs of the zircons from sample 9507/178.6 of the Samolazovskoe Gold Deposit (ion microprobe crater is about 20 μm in size).

    Zircon cores are surrounded by rims with variable thickness, reaching 20–30 µm. In addition, both zircon cores and rims are heterogeneous in terms of zircon structure. Darker inner rims are clearly distinguishable from the light-gray outer rims (for example, points 2.2 and 2.1; Fig. 3). Zircon rims of both generations are cross-cut by fractures, penetrating towards the zircon cores. There are single zircon grains without cores (point 9.1), and these correspond to the light gray outer rim in the CL image.

    In total, 18 points were dated with the local method (SHRIMP-II), all of which represent the distinguished zircon domain-cores and two types of rims (Table 1). Among them, there were nine zircon points, which formed the subconcordant assemblage, and the remaining nine points stretched along the discordia line (Fig. 4a). The discordia parameters were calculated based on 10 points-6 discordant points (except for the most distant points 6.1, 4.1 and 8.1 from the discordia line) and 4 points from the subconcordant assemblage (points 1.2, 9.1, 2.1 and 3.1). The upper discordia-concordia intercept yields the age of 1 937±24 Ma; the lower intercept yields an age of 83±11 Ma; MSWD is 5.3. Points 1.1 and 4.2 that lie close to the lower intersection of discordia line (Fig. 3a) are characterized by maximum percent discordancy (88% and 90%, respectively; Table 1). These values indicate a significant degree of alteration of the U-Pb isotopic system. Therefore, the individual values of 206Pb/238U-age for these points (close to 135 and 183 Ma, respectively, Table 1) are devoid of geological meaning. Only the age value at the lower intersection of the discordia line about 83 Ma is subject to further interpretation (Fig. 3a). An increase in a number of zircon points when calculating the discordia leads either to an increase in error on the lower intercept age determination or to an increase in MSWD value. All the zircon cores analyzed are discordant. In addition, there are two points on the discordia line (4.2 and 2.2), which correspond to the inner dark rim of zircon grains (Fig. 3).

    Spot 206Pbc (%) U (ppm) Th (ppm) 232Th/ 238U 206Pb* (ppm) 206Pb/238U age (Ma), ±σ 207Pb/206Pb age (Ma), ±σ D (%) 207Pb/ 235U ±σ (%) 206Pb/ 238U ±σ (%) ρ
    Discordia points
    1.1 309 54.7 0.18 5.62 135 4 1 028 28 88 0.21 3.4 0.021 3.1 0.912
    4.2 0.52 219 15.2 0.07 5.41 183 4 1 587 53 90 0.39 3.6 0.029 2.2 0.618
    5.1 0.34 260 50.3 0.20 14.8 413 9 1 837 70 80 1.03 4.4 0.066 2.2 0.497
    6.1 0.44 118 55.0 0.48 11.0 661 14 2 092 16 72 1.93 2.4 0.108 2.2 0.925
    7.2 0.10 238 15.5 0.07 25.1 746 35 1 909 41 64 1.98 5.4 0.123 5.0 0.910
    4.1 0.18 122 53.7 0.45 15.5 886 18 2 114 12 62 2.66 2.3 0.147 2.2 0.956
    2.2 99.4 30.7 0.32 16.5 1 137 28 1 869 12 43 3.04 2.8 0.193 2.7 0.972
    8.1 114 51.9 0.47 19.9 1 193 26 2 037 19 45 3.52 2.6 0.203 2.4 0.908
    7.1 87.1 19.9 0.24 19.4 1 484 30 1 957 11 27 4.29 2.3 0.259 2.2 0.961
    Subconcordant clusters
    7.3 0.29 34.1 28.3 0.86 9.84 1 870 39 1 845 19 -2 5.23 2.6 0.336 2.4 0.918
    8.2 0.21 32.2 28.3 0.91 9.43 1 889 38 1 872 18 -1 5.38 2.6 0.340 2.3 0.918
    1.2 42.6 26.4 0.64 11.4 1 743 35 1 906 15 10 5.00 2.4 0.311 2.3 0.940
    9.1 37.4 33.6 0.93 11.2 1 922 39 1 928 16 0 5.66 2.5 0.347 2.3 0.937
    2.1 26.3 19.9 0.78 7.93 1 939 40 1 938 19 0 5.75 2.6 0.351 2.4 0.917
    3.1 50.8 32.5 0.66 15.5 1 957 40 1 927 14 -2 5.77 2.5 0.355 2.3 0.950
    5.2 0.02 31.4 27.1 0.89 9.45 1 938 39 1 873 16 -4 5.54 2.5 0.351 2.3 0.933
    3.2 0.40 26.6 21.9 0.85 7.90 1 912 40 1 888 26 -1 5.50 2.8 0.345 2.4 0.853
    6.2 0.02 37.6 34.7 0.95 11.3 1 930 39 1 897 14 -2 5.58 2.4 0.349 2.3 0.945
    Errors are 1σ; Pbc and Pb* indicate the common and radiogenic portions, respectively. Error in standard calibration was 0.72% (not included in above errors but required when comparing data from different mounts). Common Pb corrected using measured 204Pb. D (%) discordancy: D=100×{[Age(207Pb/206Pb)]/[Age(206Pb/238U)]–1}.

    Table 1.  Results of U-Pb geochronological studies of zircons from the Samolazovskoe gold-ore field (sample 9507/178.6)

    Figure 4.  (a) Wetherill concordia diagram of the zircons from sample 9507/178.6 of the Samolazovskoe Gold Deposit; (b) Tera-Wasserburg concordia diagram of the zircons from syenites of the ore-bearing Ryabinovy Massif (samples MT-60 and MT-61).

    The discordant zircon points are characterized by a higher REE content (1 812 ppm, on average); an average total REE content in subconcordant zircon is 550 ppm (Table 2). Due to this, the REE distribution spectra for discordant zircon grains are less differentiated (Fig. 5a), than those of the subconcordant zircons (LuN/LaN 384 and 1 609, on average, respectively). The negative Eu anomaly in disconcordant zircon is less pronounced (Eu/Eu*, 0.63 and 0.22, on average, respectively). It is remarkable that the following parameters were obtained for zircon point 7.1 (on the upper part of discordia line): minimum LREE content (24.1 ppm), the most differentiated REE spectrum (LuN/LaN=1 281) and a distinct negative Eu anomaly (Eu/Eu*=0.11, Table 2). All these parameters are similar to those obtained from the subconcordant zircon assemblage. The positive Ce anomaly in discordant zircon is lower than that in subconcordant zircon (Се/Се*, 6.39 and 31.2, on average). The REE distribution spectra for discordant zircon points show a large spread in contrast to the subconcordant assemblage, where REE distribution spectra in zircon tend to merge together (Fig. 5b).

    Spot Discordia points Subconcordant clusters
    Element 1.1 4.2 5.1 7.2 6.1 4.1 2.2 8.1 7.1 1.2 2.1 3.1 3.2 5.2 6.2 7.3 8.2 9.1
    La 10.0 6.44 10.0 10.2 13.0 2.19 1.02 3.02 0.59 1.32 0.14 0.13 0.12 0.97 0.99 0.93 0.35 0.12
    Ce 266 99.8 119 306 112 52.1 68.8 80.4 18.1 52.2 28.2 48.3 29.9 32.5 49.4 47.3 42.0 35.5
    Pr 11.1 4.29 5.63 13.9 13.7 1.63 1.24 3.48 0.62 0.94 0.21 0.31 0.16 0.49 0.70 1.05 0.45 0.18
    Nd 93.8 41.2 36.9 139 106 14.2 10.3 27.1 4.83 6.07 2.00 2.62 1.62 3.33 3.62 10.4 3.43 1.98
    Sm 138 49.9 31.8 87.2 97.4 13.6 10.3 18.0 3.78 7.08 3.15 3.94 3.16 3.84 4.04 8.88 3.92 3.46
    Eu 42.1 19.7 10.0 35.8 53.5 1.78 1.66 5.64 0.28 1.57 0.21 0.23 0.24 0.36 0.53 2.84 0.51 0.43
    Gd 265 65.9 77.6 108 225 55.1 35.9 56.2 15.9 20.4 15.7 18.7 15.3 16.7 17.7 25.0 16.7 16.4
    Dy 320 105 213 172 442 230 78.4 207 85.1 60.3 61.4 66.1 57.5 62.2 65.9 86.6 65.1 62.2
    Er 521 195 441 256 623 531 131 466 238 113 128 122 116 127 135 169 131 134
    Yb 1 123 472 952 570 1 034 942 240 886 483 212 252 220 220 244 253 316 239 246
    Lu 188 94.2 164 100 167 148 40.8 137 79.0 35.7 38.7 40.9 36.3 39.1 40.8 54.3 42.3 40.5
    Li 0.94 0.72 115 1.14 1.07 0.23 33.0 0.98 0.99 30.9 53.9 52.3 53.3 77.2 55.9 50.3 56.4 57.9
    P 221 130 380 215 796 490 238 480 377 220 275 214 277 302 285 328 245 314
    Ca 242 294 329 622 410 467 18.5 579 13.5 74.8 14.0 2.20 6.21 31.0 14.1 37.9 4.85 3.85
    Ti 68.2 44.1 506 78.7 38.6 43.7 30.7 26.5 16.9 26.6 16.0 18.9 52.1 130 18.2 60.6 18.7 30.2
    Sr 21.2 8.23 8.85 21.7 36.0 13.7 0.51 34.7 0.74 1.82 0.31 0.39 0.39 1.04 1.08 2.20 0.44 0.35
    Y 3 579 1 212 2 679 2 048 4 164 2 967 790 2 624 1 216 657 715 689 684 750 778 1 021 750 752
    Nb 163 66.3 74.5 56.1 56.9 63.1 55.1 40.1 49.0 56.0 59.6 48.9 47.3 42.2 31.9 39.7 16.5 18.1
    Ba 12.9 13.9 16.4 8.42 17.9 5.64 2.83 8.80 1.15 1.41 1.31 1.61 1.38 2.26 2.09 2.50 1.67 1.90
    Hf 12 253 13 791 10 695 11 572 10 863 10 295 12 266 10 555 11 928 13 558 9 665 18 989 9 794 9 296 9 522 10 406 10 438 9 664
    Th 288 87.9 257 109 395 339 148 272 83.2 125 98.2 161 113 115 160 166 146 155
    U 2 286 1 760 1 861 1 882 1 428 991 583 931 463 389 191 350 181 249 271 399 302 247
    Th/U 0.13 0.05 0.14 0.06 0.28 0.34 0.25 0.29 0.18 0.32 0.51 0.46 0.62 0.46 0.59 0.42 0.48 0.63
    Eu/Eu* 0.67 1.04 0.61 1.12 1.10 0.20 0.26 0.54 0.11 0.40 0.09 0.08 0.10 0.14 0.19 0.58 0.19 0.17
    Ce/Ce* 6.10 4.59 3.85 6.23 2.03 6.68 14.8 6.01 7.22 11.4 39.0 57.6 51.8 11.3 14.4 11.6 25.7 58.3
    ΣREE 2 978 1 154 2 061 1 799 2 886 1 992 620 1 891 929 511 530 524 480 530 572 722 545 540
    ΣLREE 381 152 172 469 244 70.1 81 114 24.1 60.5 30.5 51.4 31.8 37.3 54.8 59.7 46.3 37.7
    ΣHREE 2 417 933 1 848 1 206 2 490 1 906 526 1 753 901 442 496 468 445 489 512 650 494 499
    LuN/LaN 181 141 158 94.8 124 652 386 439 1 281 260 2 590 3 009 2 908 387 397 561 1 178 3 192
    LuN/GdN 5.74 11.6 17.1 7.48 6.01 21.8 9.20 19.8 40.1 14.1 20.0 17.7 19.2 19.0 18.6 17.5 20.4 19.9
    SmN/LaN 22.0 12.4 5.09 13.7 12.0 9.99 16.2 9.55 10.2 8.58 35.0 48.2 42.1 6.33 6.52 15.2 18.2 45.3
    T (Ti) (℃) 946 893 1 269 965 878 892 853 837 792 837 786 803 913 1 034 799 932 801 851

    Table 2.  Trace element concentrations (ppm) in zircons from the Samolazovskoe gold-ore field (sample 9507/178.6)

    Figure 5.  REE distribution spectra of zircon grains from the Samolazovskoe goldore field (sample 9507/178.6). (a) Discordia spots; (b) subconcordant clusters.

    Based on U content and lower Th/U ratio value, zircon points from the discordant cluster differ from those of the subconcordant clusters based on the SHRIMP-II (Table 1) and SIMS (Table 2) data analyses. The SIMS data analysis further indicate a minimum value of 583 ppm for zircon grains on the discordant cluster at a maximum content of 2 286 ppm (Table 2). The U content on the subconcordant zircon cluster is significantly lower varying from 181 ppm to 399 ppm. Similarly, discordant zircon is characterized by higher contents of non-formula elements such as the Ca, Sr and Y in comparison to zircon values along the concordant clusters (Table 2). According to Geisler and Schleicher (2000), the content of Ca in zircon normally reflects positive correlation with its discordant counterpart as a result of loss of radiogenic Pb under the influence of fluids. The latter observation is also reflective in our samples, with the exception of point 8.1. On zircon points (2.2 and 7.1) which lie along the upper section of the discordia line, the minimum content of discordant zircon for Ca is 18.5 ppm and 13.5 ppm, respectively (Table 2). The average Са content in the discordant zircon assemblage equates to 330 ppm, while in zircon from the subconcordant assemblage is 21 ppm.

    In the background of the complex enrichment of discordant zircon with impure-elements, only Li from this group has shown lower content (averaging up to 17.1 ppm) in comparison with zircon from the concordant cluster (averaging 54.2 ppm; Table 2). It is commonly known that the diffusion of Li in zircon is complex (Ushikubo et al., 2008). Therefore, the threefold decrease in Li content, on average, can only be due to intensive external fluid influence.

    The Hf content extensively varies in every distinguished zircon assemblages. In case of discordant zircon, the Hf content lies within the interval of 10 295 ppm–13 791 ppm at an average value of 11 580 ppm. The average Hf content in zircon from the subconcordant assemblage is lower (10 293 ppm). However, the content is abnormally increased reaching up to 18 989 ppm as noted on point 3.1 (Table 2). In general, such an interval of Hf content is a characteristic of zircon from metamorphic origin (Skublov et al., 2012; Belousova et al., 2002).

    The Ti content in the compared zircon groups does not differ in principle, if we do not take into account the abnormally high content of 506 ppm at the discordant point of zircon 5.1 (Table 2). During estimation of zircon crystallization temperature with the use of a Ti-in-zircon thermometer method by Watson et al. (2006) an account was not taken with regards to the Ti content of 130 ppm at point 5.2 due to the limitations of the Ti-thermometer (Page et al., 2007). The average zircon crystallization temperature was 882 ℃ for discordant zircon and 840 ℃ for zircon from the subconcordant assemblage. Both these values correspond to granulite-facies metamorphic conditions.

  • It is evident that quartz-feldspar metasomatic rocks are products of hydrothermal alteration of the crystalline basement rocks, which are represented by Nimnyr Complex of granitoids and charnokites with widespread processes of ultrametamorphism under the granulite-faces metamorphic conditions (Glebovitskii et al., 2012a, b, 2010). Due to a detailed isotope-geochronological study of zircons from the Aldan Shield granitoids, it was established that latest charnokite was formed between 1 900 and 1 960 Ma. This marks a geological period, which was characterized by the formation of late autochthonous charnokites under the granulite facies metamorphic conditions and allochtonous granites and charnokites-in the central part of the granulite aureole (Glebovitskii et al., 2012a). In comparison with early zircons, late varieties are more enriched in U and this led to a decrease in Th/U ratio. Zircon from diatectic charnokites of the Nimnyr Complex yields the concordant age of 1 945±13 Ма (Glebovitskii et al., 2012a). Later, the age determination of the same assemblages carried out by dating of monazite has indicated a relatively similar age of 1 946±7 Ма (Glebovitskii et al., 2012a). The Paleoproterozoic age of the granite complexes and associated metamorphism of granulite facies in Nimnyr Complex determined from zircon and monazite grains are within the measurement accuracy of the upper discordia intercept age obtained for zircons from quartzfeldspar metasomatic rocks of the Samolazovskoe Deposit (sample 9507/178.6), 1 937±24 Ма (Fig. 4a).

    The next event, which is recorded in the U-Pb isotope system of zircon grains from quartz-feldspar metasomatic rocks of the Samolazovskoe Deposit, is characterized by lower discordiaconcordia intercept age of 83±11 Ма (Fig. 4a). Therefore, there is a clear distinction of the Late Cretaceous event, since the zircon points are evenly distributed along the entire segment of discordia line between intercepts with the concordia line. Due to this, two zircon points 4.2 and 1.1 are located close to the lower intercept. The influence of fluid on zircon grains resulted in the enrichment of zircon from the discordant cluster with nonformula elements (REE, Y, Ca, Sr and others) and a loss of radiogenic Pb dominantly from zircon cores. Zircons of hydrothermal origin are different from magmatic and metamorphic zircons by a number of signatures-specific features of inner structure and the features of distribution of rare earth and trace elements (Jiang et al., 2019; Li et al., 2019a, 2018b; Yang et al., 2014; Fu et al., 2009; Pelleter et al., 2007; Schaltegger, 2007). "Hydrothermal" zircon is characterized by higher concentrations of non-formula elements, such as Ca, Sr, Ti, LREE and some others. The REE distribution in hydrothermal zircons is less differentiated (more gentle), with decreased positive Ce anomaly, and a variable (from negative to positive) Eu anomaly. In addition hydrothermal zircons are usually darker in cathodoluminescent images and the oscillatory zonation of the precursor zircons is completely removed during the hydrothermal alteration process (Li et al., 2019c, d, 2018a). The zircons, the age (83±11 Ma) of which records the hydrothermal event (points on the discordia line; Table 2) have higher concentrations of elements, indicating their hydrothermal origin (an average content of the same element in zircons from the subconcordant cluster, corresponding to the protolith age is given in brackets): Сa 330 ppm (21 ppm), Sr 16 ppm (0.9 ppm), Ti 95 ppm (41 ppm), Nb 69 ppm (40 ppm), Ba 9.8 ppm (1.8 ppm), U 1 354 ppm (287 ppm), Y 2 365 ppm (755 ppm), LREE 190 ppm (46 ppm). In general, zircons, points of which lie on the discordia line have more gentle REE distribution spectra-LuN/LaN ratio is 384 on average at 1 609 for subconcordant zircon. This zircon is characterized by reduced Се-anomaly-Ce/Ce* ratio averages 6.4, with that averaging 31.2 in the subconcordant zircon). Eu-anomaly is also reduced (Eu/Eu* ratio averages 0.63, with that averaging 0.22 in the subconcordant zircon). In three points, Eu-anomaly becomes positive (Eu/Eu* > 1, Table 2). Apparently, zircon cores with high U content are characterized by partially metamict structure, which led to the removal of Pb by hydrothermal fluids resulting in a downward-shift of points on the concordia diagram along the discordia line. We believe that the zircon cores are more susceptible to metamict decay than zircon rims due to a higher U content. Accordingly, being affected by fluid transporting incompatible elements among others, rare-earth elements are more easily incorporated into zircon cores. In turn, the incorporation of incompatible (non-formula) elements increases a number of defects in the zircon structure and again makes the incorporation of impurity elements easier. Zircon rims with preserved crystalline structure remain resistant to hydrothermal alterations. However, even among the rims, there are two zircon points (2.2 and 4.2, Table 2), lying on the discordia line, which have the geochemical characters typical of zircons of hydrothermal origin.

    As noted above, the formation of Au deposits in the central Aldan was associated with the alkaline intrusions and related hydrothermal-metasomatic alteration. It was established that the U-Pb age of the latest magmatic bodies of explosive breccia with syenite porphyry cement within the Yukhta Massif, enclosing the Samolazovskoe Deposit, is 127 Ma (Borisenko et al., 2017). The Rb-Sr age dating (monofraction method) of feldspar and biotite from sample 9507/178.6 yields age of 128±1 Ma. This coincides with the geochronological data from the Yukhta Massif, but it is not a characteristic of zircon from quartz-feldspar metasomatic rocks, developed after the Nimnyr Complex of granitoids and charnokites in the near-contact zone.

    The ages of alkaline rocks of the ore-bearing Ryabinovy Massif (120–147 Ma) and related alkaline metasomatic rocks (125–133 Ма) were previously obtained using U-Pb and Rb-Sr age dating methods (Shatova et al., 2017; Shatov et al., 2012). Despite the limited number of zircon grains, the additional geochronological study of zircons from syenites of the ore-bearing Ryabinovy Massif (samples MT-60 and MT-61) has revealed the presence of two distinct age clusters ~125–138 and 76–83 Ма (Fig. 4b). The older ages of zircons from syenites correspond to the recent ages obtained for the central Aldan ore district (Shatova et al., 2017; Shatov et al., 2012). Until now, there is still no explanation for an age range (76–83 Ma) of single zircon grains from ore-bearing syenites of the Ryabinovy Massif. The lower intercept age (83±11 Ма) of zircons from the Samolazovskoe Deposit allows us to suggest the development of activation processes (fluid influence) in the Late Cretaceous time. These processes are recorded in the U-Pb isotope system and geochemical features of zircons from the Precambrian metamorphic rocks of the crystalline basement at the formation of the Samolazovskoe Deposit in the central Aldan ore district. A similar scenario is reflected in a number of ore fields where Cretaceous hydrothermal zircons were formed under the influence of fluid generated by deep Cretaceous magmatism which is not entirely visible at shallow depths (Li et al., 2019b, 2018c). These processes indicate the complex history of geological development of the study area and can reflect the effect of local mantle diapirs, penetrating into a slab window due to detachment of a subducting plate or the effect of an intraplate mantle plume. This plume originated (or continued its development) after the termination of the subduction and collision processes. The detailed study of geochemical and isotope-geochemical parameters of igneous rocks and ore mineralization can contribute to the interpretation of tectonic evolution of the central Aldan district. The association of telescoped ore mineralization with heterochronous stages of tectonic evolution which were revealed in some regions (Jiang et al., 2019; Li H et al., 2019a, 2018a, b, c; Zhang et al., 2019; Li G M et al., 2017) can serve as an example of such an approach.

    In total, two types of the hydrothermal-metasomatic paragenesis were recognized in sample 9507/178.6: quartz-feldspar and later phyllic (roscoelite, carbonate, fluorite, adular, quartz). Moreover, the age of the quartz-feldspar alteration process (128±1 Ма), which is not recorded in the U-Pb isotope system of zircon, was obtained with the Rb-Sr method. This age is correlated with the occurrences of magmatism. On the basis of paragenetic sequence of mineralization and age systems it is thus possible to suggest the relationships between the ore mineralization associated with phyllic alteration, and the Late Cretaceous tectonic-magmatic activation in the region.

  • (Ⅰ) Zircons from quartz-feldspar metasomatic rocks of the Samolazovskoe Deposit are characterized by heterogeneous structure. This comprises: (1) light rims with a subconcordant age of 1 937±24 Ma, with REE content of 550 ppm; (2) dark cores with a discordant age of 83±11 Ma, and higher REE (~1 812 ppm), U and non-formula elements (Ca, Sr, and Y) contents with respect to rims due to the fluid effect on zircons. These zircons originated from the Paleoproterozoic host rocks but were not formed by metasomatic processes, since the latter caused the re-arrangement of the U-Pb isotope system in the zircon cores.

    (Ⅱ) Single zircon grains from syenites of the ore-bearing Ryabinovy Massif yield age values in the range of 76–83 Ma.

    (Ⅲ) The data obtained suggest that the fluid supply related to the regional tectonic-magmatic activation in the central Aldan continued until the Late Mesozoic.

  • This study was supported by the Russian Foundation of Basic Research (RFBR) (No. 16-35-00334 mol_a), and a state contract of the Institute of Precambrian Geology and Geochronology of Russian Academy of Sciences (No. 0153-2019-0002). The final publication is available at Springer via https://doi.org/10.1007/s12583-020-1304-z.

Reference (60)

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return