Late Neoarchean subduction-related crustal growth in the Northern Liaoning region of the North China Craton: Evidence from ∼2.55 to 2.50 Ga granitoid gneisses
Late Neoarchean subduction-related crustal growth in the Northern Liaoning region of the North China Craton: Evidence from ∼2.55 to 2.50 Ga granitoid gneisses
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DOI：
10.1016/j.precamres.2016.05.018
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发表时间：
2016-08
影响因子：
3.8
通讯作者：
Wei Wang;Shuwen Liu;Peter A. Cawood;Xiang Bai;R. Guo;Boran Guo;Kang Wang
中科院分区：
文献类型：
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作者：
Wei Wang;Shuwen Liu;Peter A. Cawood;Xiang Bai;R. Guo;Boran Guo;Kang Wang
华北陆壳是研究新太古代地壳生长和地球动力学演化的天然实验室，其构造活动主要发生在2.6- 2.5Ga。辽北方晚新太古代花岗质片麻岩出露较好，位于华北克拉通东部地块东北缘古鞍山-本溪构造带的北部沿着。LA-ICPMS锆石U-Pb同位素研究表明，庆元地区花岗质片麻岩可划分为两大幕，2559-2534 Ma强片麻状石英闪长质和英云闪长质至奥长花岗质片麻岩; 2529-2495 Ma弱片麻状至块状石英二长闪长质和二长花岗质片麻岩，含次英云闪长质至奥长花岗质片麻岩。晚岩浆期伴随着区域高级变质作用（2510-2495 Ma）。大多数花岗质片麻岩显示高度亏损的锆石εHf（t2）值（+4.2到+8.1），而一个二长花岗质片麻岩显示负值-4.7到-1.0，地球化学和岩石成因研究表明，石英闪长质岩浆来源于斜长石的部分熔融，贫石榴石斜长角闪岩或榴辉岩，由大洋板片物质变质而成，上升过程中板片熔体被地幔楔橄榄岩混染。英云闪长质-奥长质岩浆来源于下弧地壳中主要为幼年变质基性岩石和少量变质杂岩的部分熔融。石英二长闪长质岩浆和二长花岗质岩浆分别来自亏损地幔源的部分熔融，并在中低地壳层次被不同地壳驻留年龄的板状流体和变灰岩交代。结合前人对表壳变质火山岩的研究，北方记录了晚新太古代地壳生长，从洋中脊演化而来，从洋内弧的形成和成熟到弧-陆碰撞。弧-大陆增生和可能的板片回滚过程可能引发了幼年弧壳和较小的古大陆边缘物质的改造，产生了二长花岗质片麻岩的岩浆前体。总的来说，强烈的晚新太古代地壳生长的EB主要是由弧-大陆增生，可能与全球组装的Escherichic碎片。
The North China Craton (NCC), dominated by ∼2.6–2.5 Ga tectonothermal events, provides a natural laboratory to study Neoarchean crustal growth and geodynamic evolution. Late Neoarchean granitoid gneisses are well exposed in the Northern Liaoning Province, located north of the ancient Anshan–Benxi terrane along the northeastern margin of the Eastern Block (EB) of the NCC. LA-ICPMS zircon U–Pb isotopic data reveal that granitoid gneisses in the Qingyuan area can be grouped into two major episodes, i.e., ∼2559–2534 Ma strongly gneissic quartz dioritic and tonalitic to trondhjemitic gneisses; and ∼2529–2495 Ma weakly gneissic to massive quartz monzodioritic and monzogranitic gneisses, with subordinate tonalitic to trondhjemitic gneisses. The late magmatic episode was accompanied by regionally high-grade metamorphism (∼2510–2495 Ma). Most granitoid gneisses display highly depleted zircon εHf(t2) values (+4.2 to +8.1), whereas one monzogranitic gneiss shows negative values of −4.7 to −1.0, indicating late Neoarchean crustal growth with minor involvement of ancient continental materials probably sourced from the Anshan–Benxi terrane.Geochemical and petrogenetic studies reveal that the quartz dioritic magmas were derived from partial melting of plagioclase-poor garnet amphibolites or eclogites metamorphosed from oceanic slab materials, with slab melts contaminated by mantle wedge peridotites during ascent. The tonalitic to trondhjemitic magmas stemmed from partial melting of mainly juvenile metabasaltic rocks with minor metagreywackes of lower arc crust. In comparison, the quartz monzodioritic and monzogranitic magmas were derived respectively from partial melting of depleted mantle sources metasomatized by slab-derived fluids and metagreywackes with different crustal resident ages at middle to lower crustal levels.Combined with previous studies of supracrustal metavolcanic rocks, the Northern Liaoning Province records late Neoarchean crustal growth, evolving from mid-ocean ridge, through initiation and maturation of an intra-oceanic arc, to arc–continent collision. Arc–continent accretion and possibly slab rollback processes may have triggered reworking of both juvenile arc crust and minor ancient continental margin materials, generating the magmatic precursors for the monzogranitic gneisses. Overall, the intense late Neoarchean crustal growth of the EB was controlled mainly by arc–continent accretion, possibly linked to global assembly of cratonic fragments.