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本文系统报道了缅甸抹谷变质带中部Yinmabin花岗闪长岩体及其基性岩墙的主量元素、微量元素及锆石U-Pb年龄和Lu-Hf同位素组成,重点讨论了花岗闪长岩和基性岩墙的岩石成因、物质来源及其地质意义。抹谷Yinmabin花岗闪长岩体主量元素显示富钠(N2O/K2O=1.5~1.75)、准铝(ACNK=0.94~0.97)和钙碱性岩石系列的地球化学特征。样品富集轻稀土(LREE)元素、大离子亲石元素(LILE),相对亏损高场强元素(HFSE)。岩体的主、微量元素地球化学特征均显示其具有活动陆缘I型花岗岩的地球化学属性。抹谷Yinmabin花岗闪长岩的锆石U-Pb年龄为131~135 Ma,其εHf(t)值在-15.66~-2.99之间,平均值为-8.77,单阶段模式年龄(tDM)为795~1569 Ma;而后期侵位的辉绿岩的锆石U-Pb年龄为120~118 Ma,其εHf(t)值在-13.72~+5.82之间,平均值为-2.72,单阶段模式年龄(tDM)为570~1341 Ma,表明这些岩石可能主要来源于古老下地壳部分熔融但同时也受到地幔物质的加入混染。与滇西以及北拉萨岩浆带的Lu-Hf同位素特征十分相近,暗示抹谷-毛淡棉地块早白垩世岩浆岩带与波密-察隅-高黎贡-拉萨岩浆岩带形成环境相似,可能是腾冲岩浆岩带向南延伸的一部分。结合岩石成因、源区性质和区域构造演化,认为抹谷花岗闪长岩体及基性岩墙的形成与中特提斯洋板块的俯冲作用密切相关,同时俯冲-碰撞转换的时限应该在120 Ma左右。这对于研究抹谷地体在中生代期间中特提斯洋俯冲碰撞过程具有重要的地质意义。  相似文献   
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International Journal of Earth Sciences - The Indo-Burma Range (IBR) of Myanmar, the eastern extension of the Yarlung-Tsangpo Neotethyan belt of Tibet in China, contains mélanges with...  相似文献   
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Chen  Si  Chen  Yi  Li  Yibing  Su  Bin  Zhang  Qinghua  Aung  Me Me  Sein  Kyaing 《中国科学:地球科学(英文版)》2021,64(11):1873-1892
Science China Earth Sciences - Ultrahigh-temperature (UHT) metamorphism is critical for understanding the most extreme thermal evolution of continental crust. However, UHT metamorphism...  相似文献   
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Mesozoic ophiolites crop out discontinuously in the Indo-Myanmar Ranges in NE India and Myanmar,and represent the remnants of the Neotethyan oceanic lithosphere(Sengupta et al.,1990;Mitchell,1993).These ophiolites in the Indo-Myanmar Ranges are the southern continuation of the Neotethyan ophiolites occurring along the Yarlung Zangbo Suture Zone(YZSZ)in southern Tibet farther northwest(Mitchell,1993;Fareeduddin and Dilek,2015),as indicated by their coeval crystallization ages and geochemical compositions(Yang et al.,2012;Liu et al.,2016).The Kalaymyo ophiolite is located in the central part of the eastern Indo-Myanmar Ranges(Fig.1).composition of these ophiolites from the central Tibetan Plateau(CTP)is dominated by MORBs and minor OIBs and a distinct lack of IATs and BONs,which is inconsistent with most ophiolites worldwide(Robinson and Zhou,2008;Zhang et al.,2008).But the generation and tectonic nature of these ophiolites are still controversial.*The Kalaymyo peridotites consist mainly of harzburgites,which show typical porphyroclastic or coarse-grained equigranular textures.They are composed ofolivine(Fo=89.8–90.5),orthopyroxene(En86-91Wo1-4Fs8-10;Mg#=89.6–91.9),clinopyroxene(En46-49Wo47-50Fs3-5;Mg#=90.9–93.6)and spinel(Mg#=67.1–78.9;Cr#=13.5–31.5),and have relatively homogeneous whole-rock compositions with Mg#s of90.1–90.8 and Si O2(41.5–43.65 wt.%),Al2O3(1.66–2.66wt.%)and Ca O(1.45–2.67 wt.%)contents.TheydisplayLightRareEarthElement(LREE)-depleted chondrite-normalized REE patterns with(La/Yb)CN=0.04–0.21 and(Gd/Yb)CN=0.40–0.84,and show a slight enrichment from Pr to La with(La/Pr)CN in the range of 0.98–2.36.The Kalaymyo peridotites are characterized by Pd-enriched chondrite-normalized PGE patterns with superchondritic(Pd/Ir)CN ratios(1.15–2.36).Their calculated oxygen fugacities range between QFM–0.57 and QFM+0.90.These mineralogical and geochemical features collectively suggest that the Kalaymyo peridotites represent residual upper mantle rocks after low to moderate degrees(5–15%)of partial melting at a mid-ocean-ridge(MOR)environment.The observed enrichment in LREE and Pd was a result of their reactions with enriched MORB-like melts,percolating through these already depleted,residual peridotites.The Kalaymyo and other ophiolites in the Indo-Myanmar Ranges hence represent mid-ocean ridge(MOR)–type Tethyan oceanic lithosphere derived from a downgoing plate and accreted into a westward migrating subduction–accretion system along the eastern margin of India.  相似文献   
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