Juvenile crustal recycling in an accretionary orogen: Insights from contrasting Early Permian granites from central Inner Mongolia, North China
Juvenile crustal recycling in an accretionary orogen: Insights from contrasting Early Permian granites from central Inner Mongolia, North China
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增生造山带中的幼年地壳再循环：来自内蒙古中部和华北早二叠世花岗岩对比的见解
DOI：
10.1016/j.lithos.2016.09.017
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发表时间：
2016-11
期刊：
影响因子：
3.5
通讯作者：
薛富红
中科院分区：
文献类型：
--
作者：
袁玲玲;张晓晖;薛富红
同时代高钾钙碱性-碱性花岗岩是地球上大多数不同时代造山带后碰撞-造山后火成岩的重要组成部分，其成因是确定大陆地壳形成和分异的关键地球动力学控制因素。本文对中亚造山带东部内蒙古二连浩特早二叠世花岗岩进行了锆石U-Pb定年和地球化学研究，揭示了不同原岩连续部分熔融形成的同步高钾钙碱性-碱性花岗岩组合。约280 Ma的马干次虎杜格岩体具有钙碱性I型特征，其初始~(87)Sr/~(86)Sr比值为0.7035~0.7039，ε_(ND)(T)为+81.87~+44.70，锆石ε_f(T)为+8.0~+13.2，δ_(18O)为7.4~8.7‰。长约276 Ma的麻柴里乌苏(CLS)岩体为镁质和过铝质，初始87Sr/86Sr比值为0.7036~0.7040，εNd(T)为+11.9~+22.4，锆石εHf(T)为+66.5~+12.1，δ18O为9.7~10.9‰。这些特征与由新底侵变质玄武岩-安山岩原岩和可变表壳成分组成的混合源区的部分熔体相一致，后者在CLS岩体中的比例明显较高。相比之下，约279英年的马昆都冷(Kdl)岩套表现出A型岩浆亲和力，具有典型的碱基、Ga、Zr、Nb和Y的富集性，εNd(T)为+22.39~+33.55，锆石εHf(T)为+88.3~+712.3，δ18O值为6.8~7.5‰。这些特征表明，它们来自于脱水富钾镁铁质岩石到中间原岩的高温熔融作用。除了呈现δ18O的层状地壳结构的快照外，这些对比强烈的花岗岩不仅可以作为一个时间标志来监测俯冲带撤退后的碰撞后伸展，而且还可以作为空间岩浆代理来追踪中国大洋协会弧后盆地环境中的地壳形成和分异。
Coeval high-K calc-alkaline to alkaline granites constitute important components of post-collisional to post-orogenic igneous suites in most orogenic belts of various ages on Earth and their genesis harbors a key to ascertaining critical geodynamic controls on continental crustal formation and differentiation. This zircon U–Pb dating and geochemical study documents three contrasting Early Permian granites from Erenhot of central Inner Mongolia, eastern Central Asian Orogenic Belt (CAOB) and reveals concurrent high-K calc-alkaline to alkaline granite association derived from successive partial melting of distinct protoliths. The ca. 280 Ma Gancihuduge (GCG) pluton shows a calc-alkaline I-type character, with initial87Sr/86Sr ratios of 0.7035 to 0.7039, εNd(t) of + 1.87 to + 4.70, zircon εHf(t) of + 8.0 to + 13.2 and δ18O from 7.4 to 8.7‰. The ca. 276 Ma Cailiwusu (CLS) pluton is magnesian and peraluminous, with initial87Sr/86Sr ratios of 0.7036 to 0.7040, εNd(t) of + 1.9 to + 2.4, zircon εHf(t) of + 6.5 to + 12.1 and δ18O from 9.7 to 10.9‰. These features are consistent with partial melts of mixed sources composed of newly underplated meta-basaltic to -andesitic protoliths and variable supracrustal components, with distinctively higher proportion of the latter in the CLS pluton. By contrast, the ca. 279 Ma Kunduleng (KDL) suite exhibits an A-type magmatic affinity, with typical enrichment in alkalis, Ga, Zr, Nb and Y, εNd(t) of + 2.39 to + 3.55, zircon εHf(t) from + 8.3 to + 12.3 and δ18O values from 6.8 to 7.5‰. These features suggest that they stem from high-temperature fusion of dehydrated K-rich mafic to intermediate protoliths. Besides presenting a snapshot into a stratified crustal architecture in δ18O, these contrasting granites could not only serve as a temporal marker for monitoring post-collisional extension in the aftermath of a retreating subduction zone, but also present spatial magmatic proxy for tracing crustal formation and differentiation within back-arc basin environments in the CAOB.
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影响因子：
3.5
作者：
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