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新疆西准噶尔北部赛尔山地区早志留世流纹斑岩成因及其大地构造意义
The petrogenesis and implications of Early Silurian rhyolite porphyry in Saier Mountain region of the northern part of West Junggar
投稿时间:2018-04-14  修订日期:2018-09-10
中文关键词:流纹斑岩  下地壳熔融  后碰撞  西准噶尔  早志留世
英文关键词:rhyolite porphyry  partial melting of lower crust  post-collision  West Junggar  Early Silurian
基金项目:国家自然科学基金项目(41572206);中国地质调查项目(121201102000150009)
作者单位E-mail
杨亚琦 中国地质科学院 地质研究所, 自然资源部深地动力学重点实验室, 北京 100037  
赵磊 中国地质科学院 地质研究所, 自然资源部深地动力学重点实验室, 北京 100037 jleiz@163.com 
郑荣国 中国地质科学院 地质研究所, 自然资源部深地动力学重点实验室, 北京 100037  
徐芹芹 中国地质科学院 地质研究所, 自然资源部深地动力学重点实验室, 北京 100037  
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中文摘要:
      在新疆西准噶尔北部的赛尔山地区识别出早志留世喷发的流纹斑岩底垫侵入到和布克赛尔蛇绿混杂带内。流纹斑岩具有高SiO2(70.88%~73.36%)、Al2O3(14.30%~15.31%)和极低的MgO(0.36%~1.09%)含量,同时,还具有中-高的Sr含量(130×10-6~527×10-6)、高的Sr/Y(22.26~78.42)和(La/Yb)N(20.27~24.24)值及低的重稀土元素含量。此外,流纹斑岩与谢米斯台山北缘早志留世-早泥盆世埃达克质岩都具有正高的εHf(t)值和年轻的Hf模式年龄,同时它们还具有较高的K2O含量、较低的Mg#值和低的Cr、Ni等相容元素含量,认为它们均形成于年轻下地壳的部分熔融。在早奥陶世-早泥盆世,西准噶尔北部可能经历过洋内俯冲、弧-弧碰撞、洋盆闭合和碰撞后伸展阶段的构造演化过程,其中,早志留世之前洋盆已经闭合,随后西准噶尔北部逐渐进入碰撞后松弛期,幔源物质向下地壳渗透,与新生不久的下地壳发生混合形成岩浆池,岩浆通过多通道、多层次的复杂渠道到达中上部地壳,从而形成大量435~400 Ma的A2型和I型花岗岩以及少量埃达克质的中酸性岩浆岩,完成了大规模的地壳垂向增生过程。
英文摘要:
      The Hebukesaier ophiolite was intruded by Early Silurian rhyolite porphyry in the Saier Mountain region of northern West Junggar. The rhyolite porphyries exhibit obviously high SiO2 (70.88%~73.36%), Al2O3 (14.30%~15.31%) and extremely low MgO (0.36%~1.09%) values, and display relatively high Sr and low Y values with high Sr/Y (22.26~78.42) and (La/Yb)N (20.27~24.24) ratios. Moreover, both rhyolite porphyries in the Saier Mountain and Early Silurian-Early Devonian adakitic rocks in the north of Xiemisitai Mountain show high positive εHf(t) values and young Hf model ages, and have low K2O values, Mg# values as well as compatible elements (Cr, Co, Ni). All these features prove that in Early Silurian-Early Devonian period these rocks in Saier Mountain and the north of Xiemisitai Mountain were formed by partial melting of lower juvenile crust rather than by subducted oceanic crust. From Early Ordovician to Early Devonian, the north of West Junggar underwent intra-oceanic subduction, arc-arc collision, the closure of the ocean and post-collisional extension processes. The ocean in the north of West Junggar might have been closed before Early Silurian, followed subsequently by post-collisional extension. In the post-collisional extension stage, the mantle-derived materials migrated upward and were mixed with juvenile crust-derived materials, forming a mixed magma chamber. Lots of 435~400 Ma A2-type granites, I-type granites and a small amount of adakitic rocks were derived from this mixed magma chamber, and then the massive vertical crustal accretion was completed in this period.
杨亚琦,赵磊,郑荣国,徐芹芹,2018,新疆西准噶尔北部赛尔山地区早志留世流纹斑岩成因及其大地构造意义[J].岩石矿物学杂志,(6):901~916.
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