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Quartzite–Schist Sequences of the Aktau – Mointy Massif (Central Kazakhstan): Structural Position, Provenance, and Formation Stages of the Earth Crust in the Precambrian
Geotectonics ( IF 1.1 ) Pub Date : 2020-05-13 , DOI: 10.1134/s0016852120020065
N. A. Kanygina , A. A. Tretyakov , K. E. Degtyarev , V. P. Kovach , J. V. Plotkina , K.-N. Pang , K.-L. Wang , H.-Y. Lee

Abstract

Detrital zircons from quartzite–schist sequences of the Aktau–Mointy Massif (Central Kazakhstan), which occur in various structural positions relative to the Early Neoproterozoic felsic volcanics, were studied. The obtained U–Pb zircon dating results suggest similarity of detrital zircon age populations with a lower limiting depositional age of 1220 Ma in all quartzite–schist sequences. The different positions of quartzite–schist sequences relative to the felsic volcanics are due to subsequent deformations. The ages of detrital zircons studied fall mostly within the intervals of 1149–2105 and 2354–3159 Ma with major peaks at 1218, 1338, 1468, 1581, 1628, 1743, 1851, and 2520 Ma and minor peaks at 2016, 2619, 2696, 2791, 2823, and 3114 Ma. The structural features of quartzite–schist sequences and the presence of heavy minerals that are unstable during long-term transport indicate the predominance of local source areas, which either form the buried part of the basement of the Aktau–Mointy Massif or have been eroded completely. Within the Aktau–Mointy Massif, it enables us to use the U–Pb ages and Lu–Hf isotope compositions of detrital zircons from quartzite–schist sequences to reconstruct the history of Precambrian continental crust formation. Results suggest that the production of juvenile continental crust prevailed only during Middle Mesoproterozoic, while formation during the Mesoarchean–Neoproterozoic time accompanied magmatic reworking of the older crustal complexes.


中文翻译:

阿克套-Mointy地块(哈萨克斯坦中部)的石英岩-片岩层序:前寒武纪地壳的结构位置,物源和形成阶段

摘要

研究了阿克套-Mointy地块(哈萨克斯坦中部)的石英岩-片岩层序中的碎屑锆石,这些碎屑锆石在相对于新元古代的长英质火山形成的不同结构位置中发生。获得的U–Pb锆石测年结果表明,碎屑锆石年龄种群具有相似性,在所有石英岩—片岩层序中的下限沉积年龄均为1220 Ma。石英岩-片岩序列相对于长英质火山的位置不同是由于随后的变形。研究的碎屑锆石年龄主要在1149–2105和2354–3159 Ma之间,主要峰值在1218、1338、1468、1581、1628、1743、1851和2520 Ma,次要峰值在2016、2619、2696 ,2791、2823和3114 Ma。石英岩-片岩层序的结构特征和长期运输过程中不稳定的重矿物的存在表明,局部来源地区占主导地位,这些地区要么形成了阿克套-Mointy地块地下的埋藏部分,要么已被完全侵蚀。 。在Aktau-Mointy地块内,它使我们能够利用石英岩-片岩层序中碎屑锆石的U-Pb年龄和Lu-Hf同位素组成来重建前寒武纪大陆壳形成的历史。结果表明,幼年大陆壳的生产仅在中元古生代时期盛行,而在中古统统-新元古生代时期则伴随着旧地壳复合体的岩浆改造。它们要么形成了Aktau-Mointy地块地下室的埋藏部分,要么已被完全侵蚀。在Aktau-Mointy地块内,它使我们能够利用石英岩-片岩层序中碎屑锆石的U-Pb年龄和Lu-Hf同位素组成来重建前寒武纪大陆壳形成的历史。结果表明,幼年大陆壳的生产仅在中元古生代时期才盛行,而在中古统统-新元古代时期的形成伴随着对旧地壳复合体的岩浆改造。它们要么形成了Aktau-Mointy地块地下室的埋藏部分,要么已被完全侵蚀。在Aktau-Mointy地块内,它使我们能够利用石英岩-片岩层序中碎屑锆石的U-Pb年龄和Lu-Hf同位素组成来重建前寒武纪大陆壳形成的历史。结果表明,幼年大陆壳的生产仅在中元古生代时期盛行,而在中古统统-新元古生代时期则伴随着旧地壳复合体的岩浆改造。
更新日期:2020-05-13
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