The metasedimentary rocks from the eastern margin of the Tarim Craton: Petrology, geochemistry, zircon U–Pb dating, Hf isotopes and tectonic implications
The metasedimentary rocks from the eastern margin of the Tarim Craton: Petrology, geochemistry, zircon U–Pb dating, Hf isotopes and tectonic implications
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塔里木克拉通东缘变沉积岩：岩石学、地球化学、锆石U-Pb定年、Hf同位素及构造意义
DOI：
10.1016/j.lithos.2013.08.010
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发表时间：
2013-10
期刊：
影响因子：
3.5
通讯作者：
Luo-Juan Wang
中科院分区：
文献类型：
--
作者：
Patrick Asamoah Sakyi;Sanjeewa P.K. Malaviarachchi;Song-Jian Ao;Luo-Juan Wang
敦煌地块位于塔里木盆地东部，广泛出露前寒武纪TTG片麻岩和变质表壳岩。塔里木盆地东缘红柳峡地区敦煌群一套变质沉积岩以中等含量的石英、斜长石和黑云母，少量石榴石或蓝晶石为特征，多数岩石经历了强烈的变形，角闪岩相面理发育。样品中Fe 2 O3 + MgO和TiO 2含量适中，Al 2 O3/SiO2和K2 O/Na 2 O比值适中，化学蚀变指数（CIA）低，成分变异指数（ICV）高，表明其形成于大陆岛弧环境。红柳峡变质沉积岩中岩浆型碎屑锆石U-Pb年龄为2476 ~ 1950 Ma，峰值为2417 Ma。变质成因的碎屑锆石在1832 Ma时有一个年龄峰值，可能代表古元古代的一次构造热事件。考虑到所分析样品的主要年龄群体与塔里木盆地古元古代早期的构造热事件相一致，我们认为塔里木盆地可能是红柳峡地区变质沉积岩原岩沉积的主要物源。锆石Hf同位素组成（εHf（t）=-5.8 ~+2.9）表明塔里木盆地东部中太古代（TDMC= 2.8-2.9 Ga）有大量的新生物质加入到地壳中，并对古老物质进行了少量改造。红柳峡地区的变质沉积岩对塔里木盆地的演化具有明显的制约作用。一种可能的构造模式是，研究区发生了多次热事件（~ 2.4Ga、2.2Ga、2.0Ga和1.8Ga），中太古代是塔里木盆地东部地壳生长的重要时期，而~ 1.83Ga变质作用可能代表了与超大陆哥伦比亚内的塔里木盆地有关的热事件。
The Dunhuang Block, located in the eastern Tarim Craton, widely exposes Precambrian TTG gneisses and metamorphosed supracrustal rocks. A suite of metasedimentary rocks of the Dunhuang Group in the Hongliuxia area on the eastern margin of the Tarim Craton are characterized by moderate contents of quartz, plagioclase, and biotite, with minor amounts of garnet or kyanite, most of which have experienced strong deformation, resulting in well-developed amphibolite-facies foliations. The examined samples are characterized by moderate Fe2O3+ MgO and TiO2contents, and Al2O3/SiO2and K2O/Na2O ratios with low Chemical Index of Alteration (CIA) and high Index of Compositional Variability (ICV) values, suggesting that the protolith sediments originated from continental island arc environment. The U–Pb ages of magmatic-type detrital zircons from the Hongliuxia metasedimentary rocks range between 2476 Ma and 1950 Ma, with a peak at 2417 Ma. Detrital zircons of metamorphic origin yielded an age peak at 1832 Ma, which may represent a tectono-thermal event in the Paleoproterozoic. Considering that the main age populations of the analyzed samples are consistent with the tectono-thermal events in the Tarim Craton during the early Paleoproterozoic, we propose that the Tarim Craton was possibly the major source for the protolith sediments of the metasedimentary rocks in the Hongliuxia area. Zircon Hf isotopic compositions (εHf(t) =− 5.8 to + 2.9) suggest voluminous addition of juvenile materials to the crust and minor reworking of old materials in the eastern Tarim Craton during the Mesoarchean (TDMC= 2.8–2.9 Ga). The metasedimentary rocks of the Hongliuxia area provide clear constraints to the evolution of the Tarim Craton. A possible tectonic model is that multiple thermal events (~ 2.4 Ga, 2.2 Ga, 2.0 Ga and 1.8 Ga) occurred in the study area, and the time period of Mesoarchean was important for crustal growth in the eastern Tarim Craton, whereas the ~ 1.83 Ga metamorphism might represent a thermal event associated with the Tarim Craton within the supercontinent Columbia.
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