Petrogenesis of taxitic dioritic-tonalitic gneisses and Neoarchean crustal growth in Eastern Hebei, North China Craton
Petrogenesis of taxitic dioritic-tonalitic gneisses and Neoarchean crustal growth in Eastern Hebei, North China Craton
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华北克拉通冀东滑变闪长岩-英闪长片麻岩岩石成因与新太古代地壳生长
DOI：
10.1016/j.precamres.2016.08.002
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发表时间：
2016
影响因子：
3.8
通讯作者：
Wang Wei
中科院分区：
文献类型：
--
作者：
Fu Jinghao;Liu Shuwen;Chen Xu;Bai Xiang;Guo Rongrong;Wang Wei
冀东中国克拉通北部遵化-青龙微地块中的滑移闪长-英云闪长质片麻岩，由闪长岩、石英闪长岩、英云闪长质片麻岩和奥长花岗片麻岩组成。它们呈滑移岩或条带状构造，经历了角闪岩-局部麻粒岩相变质作用。闪长质片麻岩和石英闪长质片麻岩(DQ群)可分为高镍亚群(HNDQ亚群)和低镍亚群(LNDQ亚群)，英云闪长质片麻岩(TT群)可分为低分馏亚群(LFTT亚群)和高分馏亚群(HFTT亚群)。La-ICPMS锆石U-Pb同位素测年结果表明，HNDQ、LNDQ和LFTT亚群的岩浆前驱体侵位时间为2522 Ma±9.13 Ma~2533 Ma±9.14 Ma，而HFTT亚群的岩浆前兆侵位时间为2499 Ma±14.4 Ma。岩石成因研究表明，HNDQ亚群的岩浆前体来自以板片熔体交代为主的地幔橄榄岩的部分熔融，而LFTT亚群的岩浆前体是由HNDQ亚群的岩浆分离结晶形成的，主要分相为单斜辉石、磁铁矿、斜长石和磷灰石。LNDQ亚群的岩浆前体来自地幔橄榄岩的部分熔融，在岩浆演化过程中，熔体经历了角闪石、磁铁矿、斜长石和磷灰石的分馏，以板片流体交代为主。此外，HFTT亚群的岩浆前体来自于形成于弧前至海沟带的火山沉积岩的部分熔融，这些沉积岩与洋板一起被俯冲，熔体在通过地幔楔形上升过程中受到地幔橄榄岩的污染。这些新的数据结合前人对变火山岩和花岗质正长片麻岩的研究，表明这些英云闪长-英云闪长质片麻岩的岩浆前体形成于自北向南的弧后构造环境。此外，遵化-青龙微块晚新太古代变质火山岩和花岗片麻岩的Lu-Hf同位素资料表明，遵化-青龙微块在新太古代分别经历了2.72-2.70、2.64-2.56和2.53-2.50三个主要的年轻地壳生长时期，后两个时期伴随着旧地壳物质的改造。
The taxitic dioritic–tonalitic gneisses in the Zunhua–Qinglong microblock of Eastern Hebei, North China Craton, are composed of dioritic, quartz dioritic, tonalitic and trondhjemitic gneisses. They show taxitic or banded structures and were subjected to amphibolite- to local granulite-facies metamorphism. Based on their whole rock geochemistry, the dioritic and quartz dioritic gneisses (DQ Group) can be classified into a high Ni Subgroup (HNDQ Subgroup) and a low Ni Subgroup (LNDQ Subgroup), and the tonalitic and trondhjemitic gneisses (TT Group) into a low-fractionated Subgroup (LFTT Subgroup) and a high-fractionated Subgroup (HFTT Subgroup). LA-ICP-MS zircon U–Pb isotopic dating reveals that the magmatic precursors of the HNDQ, LNDQ and LFTT subgroups were emplaced from 2522 ± 13 to 2533 ± 14 Ma, whereas those of the HFTT Subgroup emplaced at 2499 ± 4 Ma. Studies in petrogenesis revealed that the magmatic precursors of the HNDQ Subgroup were derived from partial melting of mantle peridotites metasomatized chiefly by slab melts, while those of the LFTT Subgroup were formed by fractional crystallization of the magmas of the HNDQ Subgroup, with clinopyroxene, magnetite, plagioclase and apatite as the major fractionated phases. Magmatic precursors of the LNDQ Subgroup were derived from partial melting of mantle peridotites metasomatized in a dominant manner by slab-derived fluids, with melts experiencing fractionation of hornblende, magnetite, plagioclase and apatite during the magmatic evolution. Further, magmatic precursors of the HFTT Subgroup were derived from partial melting of volcanic sedimentary rocks formed in the fore arc to trench belt, which were subducted along with oceanic slabs, with the melts contaminated by mantle peridotites during their ascent through the mantle wedge.These new data, combined with previous investigations on metavolcanic rocks and granitoid orthogneisses, suggest that the magmatic precursors of these taxitic dioritic–tonalitic gneisses were formed in an arc to back-arc tectonic setting from north to south. Furthermore, Lu–Hf isotopic data from the late Neoarchean metavolcanic rocks and granitoid gneisses in the Zunhua–Qinglong microblock reveal that the Zunhua–Qinglong microblock experienced three major periods of juvenile crustal growth during Neoarchean at 2.72–2.70 Ga, 2.64–2.56 Ga and 2.53–2.50 Ga, respectively, with the latter two periods coupled with reworking of old crustal materials.