Detrital zircon and rutile geochronology, geochemistry and provenance of Cambrian sandstones of Iranian Azerbaijan: implications for the Neoproterozoic-Cambrian evolution of the northern Gondwana margin

IF 1.8 3区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY International Journal of Earth Sciences Pub Date : 2023-12-27 DOI:10.1007/s00531-023-02372-9

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Abstract

Within the Tethyan belt, the NW-Iranian block is bound by two sutures, the Sevan-Akera suture in the north, and the Zagros suture in the south, where the pre-Cambrian geology is poorly constrained. Lower-Middle Cambrian sandstone in NW Iran is represented by quartz and feldspar dominated sub-arkose and sub-litharenite with well-developed cross bedding structures. They are interlayered with shale and limestone and overlain unconformably by Middle Cambrian dolomite. Here we describe and present U–Pb ages of the detrital zircon and rutile together with in-situ ε-Hf data from Lower to Middle Cambrian sandstones. Some zircons are characterized by oscillatory zoning and Th/U ratios of 0.3 to 2.0, pointing to an igneous provenance. Ages of the detrital zircons range from 481 to 2762 Ma, whereby the majority of zircons have ages between 524 and 1000 Ma (Neoproterozoic), and small peaks at 1800–2000 and 2400–2600 Ma. Late Paleoproterozoic to Mesoproterozoic zircons (1100–1750 Ma) are absent in the detrital record which is a distinctive feature of Gondwana-related detrital zircons. Detrital rutile has elevated Cr contents and variable Zr content (88 to 1087 ppm), suggesting derivation mainly from amphibolite-facies meta-basic rocks. U–Pb rutile ages range from 561 to 1253 Ma. Initial ε-Hf values of the Neo-Proterozoic zircons range from -10 to 20, suggesting an association of highly depleted mantle and crustal magmas. Thus, the Lower-Middle Cambrian sandstones in Iranian Azerbaijan were supplied from a Neoproterozoic igneous and metamorphic provenance. Sandstone whole-rock major and trace elements are in accordance with a detrital material provenance from continental granitoids and Precambrian recycled sediments. These results support the hypothesis that Iranian Azerbaijan Cambrian detritus was supplied from repetitive recycling of the crystalline basement and related sedimentary cover of the Saharides and the Arabian-Nubian Shield and deposited in a passive-margin setting in northern Gondwana land. Our results show a close geological tie between Iranian Azerbaijan, Sanandaj-Sirjan, Zagros, Alborz, and other Gondwana-Land-derived units in terms of Early Paleozoic detritus sources. Northwest Iranian Block was probably a passive continental margin in Late Ediacaran-Cambrian after the so-called Cadomian orogeny.

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伊朗阿塞拜疆寒武纪砂岩的碎屑锆石和金红石地质年代、地球化学和产地：对冈瓦纳大陆北缘新元古代-寒武纪演化的影响

摘要在泰提安带中，西北伊朗地块被两条缝合线所束缚，即北部的塞万-阿克拉缝合线和南部的扎格罗斯缝合线。伊朗西北部的下-中寒武统砂岩以石英和长石为主的亚云英岩和亚闪长岩为代表，具有发达的交叉层理结构。它们与页岩和石灰岩互层，与中寒武统白云岩互不叠压。在此，我们描述并展示了下寒武统至中寒武统砂岩中的锆石和金红石的U-Pb年龄以及原位ε-Hf数据。一些锆石具有振荡区带和 0.3 至 2.0 的 Th/U 比值，表明其来源于火成岩。锆石碎片的年龄在 481 至 2762 Ma 之间，其中大部分锆石的年龄在 524 至 1000 Ma 之间（新元古代），在 1800 至 2000 Ma 和 2400 至 2600 Ma 之间有小高峰。晚古生代到中新生代的锆石（1100-1750 Ma）没有出现在碎屑记录中，这是冈瓦纳相关碎屑锆石的一个显著特点。碎屑金红石的铬含量较高，锆含量（88-1087 ppm）不等，表明主要来自闪长岩期元基性岩。金红石的U-Pb年龄在561至1253Ma之间。新近新生代锆石的初始ε-Hf值介于-10到20之间，表明与高度贫化的地幔和地壳岩浆有关。因此，伊朗阿塞拜疆的下-中寒武统砂岩是由新近新生代火成岩和变质岩提供的。砂岩的全岩主要元素和微量元素与来自大陆花岗岩和前寒武纪循环沉积物的碎屑物质来源一致。这些结果支持这样的假设，即伊朗阿塞拜疆寒武纪的碎屑是由撒哈拉沙漠和阿拉伯-努比亚地盾的结晶基底和相关沉积覆盖层的重复循环提供的，并沉积在冈瓦纳陆地北部的被动边缘环境中。我们的研究结果表明，就早古生代碎屑源而言，伊朗阿塞拜疆、萨南达杰-锡尔让、扎格罗斯、阿尔伯兹和其他冈瓦纳-陆地衍生单元之间有着密切的地质联系。伊朗西北地块很可能是晚埃迪卡拉-寒武纪所谓卡多米造山运动之后的被动大陆边缘。图表摘要

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来源期刊

International Journal of Earth Sciences 地学-地球科学综合

CiteScore

4.60

自引率

4.30%

发文量

120

审稿时长

4-8 weeks

期刊介绍： The International Journal of Earth Sciences publishes process-oriented original and review papers on the history of the earth, including - Dynamics of the lithosphere - Tectonics and volcanology - Sedimentology - Evolution of life - Marine and continental ecosystems - Global dynamics of physicochemical cycles - Mineral deposits and hydrocarbons - Surface processes.