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首页> 外文期刊>Precambrian Research >Zircon REE patterns and geochemical characteristics of Paleoproterozoic anatectic granite in the northern Tarim Craton, NW China: Implications for the reconstruction of the Columbia supercontinent
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Zircon REE patterns and geochemical characteristics of Paleoproterozoic anatectic granite in the northern Tarim Craton, NW China: Implications for the reconstruction of the Columbia supercontinent

机译：中国西北塔里木克拉通北部古元古代晚酸性花岗岩的锆石REE模式及地球化学特征：对哥伦比亚超大陆重建的启示

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摘要

Because Archean basement rocks are sparsely distributed around the Tarim Basin, little is known of the relationship between the Tarim Craton and the Paleo- to Mesoproterozoic Columbia supercontinent. Zircon U-Pb dating of a Paleoproterozoic gneissic granite in the northern Tarim Craton yielded a crystallization age of 1915±13Ma, consistent with global Paleoproterozoic collisional events (ca. 2.1-1.8Ga) recorded in most cratons. Despite the fact that some zircons display discordant U-Pb ages with a distinct loss of radiogenetic Pb, all grains have similar ~(176)Lu/~(177)Hf and ~(176)Hf/~(177)Hf(t) values. Zircons from this granite have high Th/U ratios (0.15-0.95), but contrasting rare earth element (REE) patterns. The REE patterns show that the incorporation of most REE elements correlates with increasing age discordance. The discordant zircons, unlike typical magmatic zircons, were probably formed in an open system with the participation of aqueous fluids or hydrous melts during late- to post-magmatic recrystallization. Rocks of this granite pluton have high contents of SiO_2 (75.45-78.49wt.%) and total alkali (6.38-9.00wt.%), and moderate Al_2O_3 (10.31-13.80wt.%), showing peraluminous characteristics. Their high contents of high field strength elements (HFSE) and significant negative Eu anomalies are consistent with the geochemical characteristics of A-type granites. The low ε_(Hf)(t) values of the granite suggest a derivation through anatexis of late Neoarchean tonalite-trondhjemite-granodiorite (TTG) rocks of the basement, indicating that the geochemical characteristics of A-type granites may originate from partial melting of Archean TTGs. In combination with previously published age data, the regional anatexis provides evidence of a late Paleoproterozoic orogenic event on the northern margin of the Tarim Craton. Because the Paleoproterozoic and Mesoproterozoic sedimentary rocks in the northern Tarim Craton show characteristics of sediments deposited on a passive continental margin, the craton is suggested to have occupy an outboard position in the Columbia supercontinent.
机译：由于太古宙基底岩石稀疏地分布在塔里木盆地周围，因此人们对塔里木克拉通与古至中元古代哥伦比亚超大陆之间的关系知之甚少。塔里木克拉通北部古元古代片麻岩花岗岩的锆石U-Pb测年产生了1915±13Ma的结晶年龄，与大多数克拉通中记录的全球古元古代碰撞事件（约2.1-1.8Ga）一致。尽管某些锆石显示出不一致的U-Pb年龄且放射源Pb明显损失，但所有晶粒的〜（176）Lu /〜（177）Hf和〜（176）Hf /〜（177）Hf（t）相似价值观。来自该花岗岩的锆石具有较高的Th / U比（0.15-0.95），但具有相反的稀土元素（REE）模式。 REE模式表明，大多数REE元素的掺入与年龄不一致性的增加有关。与典型的岩浆锆石不同，不一致的锆石可能是在开放系统中形成的，在晚期至岩浆再结晶过程中，含水流体或含水熔体参与其中。该花岗岩岩体的岩石具有高含量的SiO_2（75.45-78.49wt。％）和总碱（6.38-9.00wt。％），以及中等的Al_2O_3（10.31-13.80wt。％），表现出高铝特性。它们的高场强元素（HFSE）含量高且Eu异常显着负值与A型花岗岩的地球化学特征一致。花岗岩的低ε_（Hf）（t）值表明是通过基底的新新纪古代斜纹岩-长晶岩-花岗岩-闪长闪长岩（TTG）的后期反酸盐岩衍生而来的，表明A型花岗岩的地球化学特征可能源自于太古代的TTG。结合先前公布的年龄数据，该地区的无脊椎动物为塔里木克拉通北缘晚古元古代造山事件提供了证据。由于塔里木克拉通北部的古元古代和中元古代沉积岩具有沉积在被动大陆边缘的沉积物特征，因此建议克拉通在哥伦比亚超大陆的外侧位置。

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