Early Paleozoic Tectonic Evolution of the South Tianshan Collisional Belt: Evidence from Geochemistry and Zircon U-Pb Geochronology of the Tie’reke Monzonite Pluton, Northwest China
Early Paleozoic Tectonic Evolution of the South Tianshan Collisional Belt: Evidence from Geochemistry and Zircon U-Pb Geochronology of the Tie’reke Monzonite Pluton, Northwest China
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DOI：
10.1086/670653
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发表时间：
2013-06
期刊：
影响因子：
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通讯作者：
He Huang;Zhaochong Zhang;M. Santosh;Dongyang Zhang;Zhidan Zhao;Junlai Liu
中科院分区：
文献类型：
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作者：
He Huang;Zhaochong Zhang;M. Santosh;Dongyang Zhang;Zhidan Zhao;Junlai Liu
本文报道了南天山碰撞带中段铁热克地区早古生代一个角闪石石英二长岩体。激光烧蚀ICP-MS锆石U-Pb定年结果表明，该岩体侵位于晚志留世。我们的数据，加上新疆南部东部和塔里木地块东部北方边缘（NMTB）同时代侵入岩的数据，表明该地区早古生代晚期发生过一次重大的岩浆事件。康苏地区新生代砂岩样品和吉根地区早古生代变质砂岩样品的碎屑锆石U-Pb年龄为462-395 Ma，证实了这一岩浆事件。铁热克岩体的地球化学成分为中等，SiO_2含量为60.73 ~ 64.73wt%，属碱钙钾玄岩系列。岩体显示Nb、Ta、P和Ti的相对亏损和大离子亲石元素（Ba、K和Rb）的富集，这是典型的大陆弧相关火成岩。全岩Sr-Nd和锆石Hf同位素数据表明，岩浆主要来源于古元古代陆壳的部分熔融，并有来自亏损地幔楔的年轻物质的输入。塔里木地块北方边缘晚志留世火山岩的年代学、地球化学和同位素特征，结合碎屑锆石U-Pb年代学资料，表明塔里木地块北缘在中奥陶世-中泥盆世为安第斯型活动大陆边缘。考虑到中天山地块同时代的岩浆活动使古生代南天山洋向北俯冲，提出了晚奥陶世-中泥盆世古生代南天山洋演化的双重俯冲模式。晚泥盆世-中石炭世，塔里木地块北方边缘可能处于构造岩浆活动的平静期，而中天山地块仍广泛受到弧型岩浆活动的影响，促使古生代南天山洋向北俯冲。
We report an Early Paleozoic hornblende quartz monzonitic pluton from the Tie’reke region in the central South Tianshan Collisional Belt (STCB). Laser ablation ICP-MS U-Pb zircon dating reveals that the pluton was emplaced during the Late Silurian at ∼ Ma. Our data, together with those from coeval intrusive rocks in the eastern STCB and the eastern Northern Margin of the Tarim Block (NMTB), indicate a major late Early Paleozoic magmatic event in the region. This magmatic event is supported by a detrital zircon U-Pb age population of 462–395 Ma obtained from a Cenozoic sandstone sample from the Kangsu region and an Early Paleozoic metasandstone sample from the Jigen region. Geochemically, the Tie’reke pluton is intermediate in composition, with SiO2 contents ranging from 60.73 to 64.73 wt%, and belongs to the alkali-calcic and shoshonitic series. The pluton displays relative depletion of Nb, Ta, P, and Ti and enrichment of large-ion lithophile elements (Ba, K, and Rb), typical of continental arc–related igneous rocks. Whole-rock Sr-Nd and zircon Hf isotopic data reveal that the magma was derived dominantly from partial melting of the Paleoproterozoic continental crust, with input from juvenile materials from a depleted-mantle wedge. In general, geochronological, geochemical, and isotopic features of the Late Silurian igneous rocks in the present STCB and NMTB, coupled with detrital zircon U-Pb geochronological data from the two sedimentary rocks, suggest that the northern margin of the Paleozoic Tarim Block was an Andean-type active continental margin during Middle Ordovician to Middle Devonian time. Given the coeval magmatism in the Central Tianshan Block, which necessitates a northward subduction of the Paleozoic South Tianshan Ocean, we propose a double-subduction model for the evolution of the Paleozoic South Tianshan Ocean during the Late Ordovician to Middle Devonian period. During the Late Devonian to Middle Carboniferous, the northern margin of the Paleozoic Tarim Block was likely characterized by tectonomagmatic quiescence, whereas the Central Tianshan Block was still extensively affected by arc-type magmatism, furthering the northward subduction of the Paleozoic South Tianshan Ocean.