Multiple phases of the Neoproterozoic igneous activity in Quruqtagh of the northeastern Tarim Block, NW China: Interaction between plate subduction and mantle plume?
Multiple phases of the Neoproterozoic igneous activity in Quruqtagh of the northeastern Tarim Block, NW China: Interaction between plate subduction and mantle plume?
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塔里木地块东北部库鲁克塔格新元古代火成岩活动的多期：板块俯冲与地幔柱的相互作用？
DOI：
10.1016/j.precamres.2011.08.005
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发表时间：
2012-12
影响因子：
3.8
通讯作者：
Ye, Hai-Min
中科院分区：
文献类型：
--
作者：
Zou, Hai-Bo;Wang, Hong-Yan;Li, Huai-Kun;Ye, Hai-Min
塔里木盆地北方缘沿着曲鲁克塔格地区广泛分布新元古代火成岩。本文报道了库鲁克塔格地区两个新元古代双峰式侵入杂岩和中土站超基性岩墙的时代、岩石学和地球化学特征，以建立Rodinia解体期间塔里木新元古代构造演化的新模式。库鲁克塔格I号（约20 km ~ 2）和IV号（约10 km ~ 2）双峰式侵入杂岩由辉长岩和花岗质岩石组成。新的锆石U-Pb年龄表明，这两个侵入杂岩的锆石共同侵位时间约为2000年。735Ma。中土站超基性岩脉侵位于约1000年。802 Ma，与邻近的切干布拉克超镁铁质-镁铁质-碳酸盐岩杂岩大致同时代。Ⅰ号和Ⅳ号杂岩体的辉长岩具有拉斑玄武岩的特征，富集大离子亲石和轻稀土元素，亏损高场强和重稀土元素。在同位素上，它们的特征是全岩Nd（t）值范围很广（0到−0），（87 Sr/86 Sr）i值可变高（0.7095-0.7059）。第I号和第IV号杂岩辉长岩样品中的锆石具有略微不同的Nd-Hf（t）（分别为−1.5-0.9和−2.5 ~ −0.5），表明Nd-Hf同位素不耦合。中土站超镁铁质岩脉的锆石具有明显的负Hf（t）（-14.9 ~-11.9），与切干布拉克碳酸岩中斜锆石的Hf同位素组成相似。这些特征，结合存在的原生金云母和角闪石，表明辉长岩可能形成通过合并地壳同化和晶体分馏/累积（AFC效应）的拉斑玄武岩岩浆最初来自交代的次大陆岩石圈地幔（SCLM）。相比之下，混入I号杂岩的花岗岩显示埃达克质特征和明显的负Nd（t）值（≤−12），并且是由于同时代镁铁质岩浆底侵作用导致的镁铁质下地壳部分熔融的产物。结合前人的研究结果，我们认为库鲁克塔格新元古代岩浆活动大致可分为四个阶段。它们是：（1）。820- 800 Ma的超镁铁-镁铁-碳酸岩杂岩和大量埃达克质花岗岩及镁铁质岩墙群; 780- 760 Ma拉斑质超镁铁质-镁铁质杂岩和大量镁铁质岩墙群;（4）650- 635 Ma的小型基性岩墙。740 Ma以来，由于塔里木从Rodinia的扩张，新元古代岩浆活动减弱。本区大量的弧特征镁铁质岩和钙碱性花岗岩的出现，是760 Ma前Rodinian热柱与塔里木大陆下洋壳俯冲相互作用的结果。由于塔里木地块位于Rodinia的边缘，因此沿塔里木北方边缘的俯冲沿着可以持续到中元古代晚期至新元古代中期（约1000年）。760Ma）。在俯冲过程中，Rodinian热柱（脉冲825-800和780- 740 Ma）加热了塔里木北方大陆弧下的岩石圈地幔，形成了大量的、多样的弧标火成岩。俯冲停止在ca。760Ma。CA。735 Ma双峰侵入杂岩和同时代的北义溪玄武岩不整合地覆盖在该ca上。820- 800 Ma花岗岩，可能表明塔里木盆地从澳大利亚扩散。
Neoproterozoic igneous rocks are widely distributed in the Quruqtagh along the northern margin of the Tarim, NW China. Here we report ages, petrography, and geochemistry of two (No. I and No. IV) Neoproterozoic bimodal intrusive complexes and Zhongtuzhan ultramafic dykes in the Quruqtagh, in order to construct a new model of Neoproterozoic tectonic evolution of the Tarim during the breakup of Rodinia. The No. I (∼20km2) and No. IV (∼10km2) bimodal intrusive complexes in Quruqtagh are composed of gabbroic and granitic rocks. New U–Pb ages of the zircons from the two intrusive complexes demonstrate that they were coevally emplaced at ca. 735Ma. The Zhongtuzhan ultramafic dykes were emplaced at ca. 802Ma, broadly coeval with the nearby Qieganbulake ultamafic-mafic–carbonatite complex. The gabbroic rocks from both No. I and No. IV complexes exhibit tholeiitic characters, enrichment in LILE and LREE, and depletion in HFSE and HREE. Isotopically, they are characterized by wide range of whole-rock ɛNd(t) values (0 to −0) and variable high (87Sr/86Sr)i(0.7095–0.7059). Zircons from the gabbroic samples of the No. I and No. IV complexes have slightly different ɛHf(t) (−1.5–0.9 and −2.5 to −0.5, respectively), indicating Nd–Hf isotopic decoupling. Zircons from Zhongtuzhan ultramafic dykes have pronounced negative ɛHf(t) (−14.9 to −11.9), resembling the Hf isotopic compositions of the baddeleyites from the Qieganbulake carbonatite. These features, combined with the presence of the primary phlogopite and hornblende, suggest that the gabbroic rocks were likely formed via combined crustal assimilation and crystal fractionation/cumulation (AFC effects) of a tholeiitic magma originally derived from a metasomatized subcontinental lithosphere mantle (SCLM). In comparison, the granites mingled into the No. I complex display adakitic signatures and pronounced negative ɛNd(t) values (≤−12), and were derived from partial melting of mafic lower crust due to the underplating of the coeval mafic magma. Our results, in conjunction with previous data in literature, indicate that the Neoproterozoic igneous activities in Quruqtagh could be broadly divided into four phases. They are as follows: (1) the ca. 820–800Ma ultramafic–mafic–carbonatite complex and voluminous adakitic granites and mafic dyke swarm; (2) the ca. 780–760Ma tholeiitic ultramafic–mafic complex and voluminous mafic dyke swarm; (3) the ca. 740–735Ma bimodal complex and bimodal volcanic series; and (4) minor 650–635Ma mafic dykes. The Neoproterozoic igneous activities waned since 740Ma as a result of the dispersing of Tarim from Rodinia. The presence of voluminous mafic rocks of arc-signature and the calc-alkaline granites in this area is due to the interaction between the Rodinian plume and oceanic crust subduction under the Tarim continent before 760Ma. As the Tarim Block was at the periphery of the Rodinia, subduction along the northern margin of the Tarim could last from late Mesoproterozoic to mid-Neoproterozoic (ca. 760Ma). During the subduction, the Rodinian plume (pulses of 825–800 and 780–740Ma) could heat the lithospheric mantle under the continental arc along the northern margin of Tarim, leading to the formation of the voluminous and diverse igneous rocks of arc-signatures. The subduction ceased at ca. 760Ma. The ca. 735Ma bimodal intrusive complex and the coeval Beiyixi basalt unconformably overlying on the ca. 820–800Ma granites, might indicate the dispersing of the Tarim from Australia.
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影响因子：
3.1
作者：
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