Episodic mantle melting-crustal reworking in the late Neoarchean of the northwestern North China Craton: Zircon ages of magmatic and metamorphic rocks from the Yinshan Block
Episodic mantle melting-crustal reworking in the late Neoarchean of the northwestern North China Craton: Zircon ages of magmatic and metamorphic rocks from the Yinshan Block
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华北克拉通西北缘新太古代晚期幕式地幔熔融-地壳改造:阴山地块岩浆岩和变质岩的锆石年龄
DOI：
10.1016/j.precamres.2012.03.002
复制
发表时间：
2012-12
影响因子：
3.8
通讯作者：
Zhang, Liqao
中科院分区：
文献类型：
--
作者：
Jian, Ping;Kroener, Alfred;Windley, Brian F.;Zhang, Qi;Zhang, Wei;Zhang, Liqao
华北克拉通西北部阴山地块由晚新太古代绿岩、高变质岩（麻粒岩、绿粒岩、暗长岩和角闪洞片麻岩）、闪长岩（麻粒岩和镁埃达克岩）和花岗岩（主要是闪长岩-闪长岩）组成。绿岩地体由以玄武岩和英安岩为主的火山层序和少量安山岩组成。高镁安山岩和高镁安山岩的锆石加权平均207pb /206Pb年龄分别为2533±5Ma和2510±7Ma，反映了两个不同的火山期。这两个峰的形成时间或早或晚于2515±10 ma（玄武岩）至2516±10Ma（英安岩）期间的一次大型火山活动，形成了玄武岩-英安岩双峰套。高变质岩岩浆锆石的207pb /206Pb加权平均年龄分别为：基性麻粒岩（2544±5Ma）、麻粒片麻岩（2521±6Ma）、绿粒岩（2535±5Ma）、角闪片麻岩（2526±5Ma）。这些年龄反映了构成高变质杂岩原岩的岩石（最小）侵位时间。高档杂岩的变质年龄分别为2515±18Ma（镁质麻粒岩）和2503±12Ma（石榴质片麻岩）。高镁闪长岩（即似镁闪长岩）锆石的加权平均年龄为2520±6Ma，明显小于同一闪长岩体中镁质闪长岩（mg -埃达克岩）的2556±14Ma。这些年龄反映了产生闪长岩块的独特岩浆脉冲。锆石年龄为2516±7Ma，与同一石英/石英为主的石英基岩的锆石年龄（2520±9Ma）难以区分。2516±7Ma闪长岩中的花岗岩组成层锆石年龄分别为2515±6Ma（高u锆石域）和2512±22Ma（低u锆石域），反映了地壳内熔融事件。闪长岩地块中2594±4Ma的亮花岗质包体和广泛存在的约2583-3485Ma（大部分约2700Ma）的锆石包体表明，在阴山地块形成之前存在着一个更古老的地壳遗迹（约bb0 ~ 2600Ma）。高镁安山岩中未变形伟晶岩岩脉的侵位年龄为2508±17Ma（锆石）。一条切割上地壳绿岩层序的未变形的闪晶岩岩脉的锆石年龄为2502±6Ma，与伟晶岩岩脉的锆石年龄相似，代表了银山地块最晚的太古代岩浆事件。这些未变形花岗岩类岩脉的年龄标志着阴山地块热构造发育的终结。根据这些新时代和已发表的地质年代学资料，我们认为阴山地块是一个典型的新太古代克拉通地块，而不是所谓的“古元古代内蒙古-冀北造山带”的一段。新太古代晚期短暂（约2556-2502Ma）内的幕式地幔熔融和由此产生的地壳改造说明了阴山地块的热构造发育，并基于它们的区域年代学相关性论证了它们在克拉通尺度上的意义。
The Yinshan Block in the northwestern North China Craton comprises late Neoarchean greenstones, high-grade metamorphic rocks (granulite, charnockite, enderbite and amphibole gneiss), diorites (sanukitoid and Mg-adakite) and granitoids (predominantly trondhjemite-tonalite). A greenstone terrane comprises a volcanic sequence of predominant basalt and dacite, with minor andesite. Zircons from a high-Mg andesite and an andesite have weighted mean207Pb/206Pb ages of 2533±5Ma and 2510±7Ma, respectively, which reflect the timing of two distinct volcanic episodes. These two either predated or postdated a major volcanic episode that formed a basalt-dacite bimodal suite during 2515±10 (basalt) to 2516±10Ma (dacite). Magmatic zircons from the high-grade metamorphic rocks yielded weighted mean207Pb/206Pb ages of 2544±5Ma for a mafic granulite, 2521±6Ma for a garnetiferous gneiss, 2535±5Ma for a charnockite, and 2526±5Ma for an amphibole gneiss. These ages reflect the (minimum) emplacement time of rocks that make up the protoliths of the high-grade metamorphic complex. The metamorphic ages of the high-grade complex were determined at 2515±18Ma for mafic granulite and 2503±12Ma for garnetiferous gneiss. Zircons from a high-Mg diorite (i.e. sanukitoid) have a weighted mean age of 2520±6Ma, which is significantly younger than the 2556±14Ma age of a magnesian diorite (Mg-adakite) from the same diorite massif. These ages reflect distinctive magmatic pulses that generated the diorite massif. A tonalite has a zircon age of 2516±7Ma, indistinguishable from the 2520±9Ma age of a trondhjemite from the same trondhjemite/tonalite-dominated batholith. A granitic compositional layer in the 2516±7Ma tonalite has zircon ages of 2515±6Ma (high-U zircon domains) and 2512±22Ma (low-U zircon domains), which reflect an intracrustal melting event. The presence of an older crustal remnant (ca. >2600Ma) prior to the formation of the Yinshan Block is indicated by a 2594±4Ma leucogranite xenolith in the diorite massif and by the widespread presence of ca. 2583–3485Ma (mostly, ca. 2700Ma) zircon xenocrysts in a variety of volcanic and plutonic rocks. An undeformed pegmatite dike in high-Mg andesite has an emplacement age of 2508±17Ma (zircon). An undeformed trondhjemite dike that cuts the supracrustal greenstone sequence yielded a zircon age of 2502±6Ma, similar to that of the pegmatite dike, and representing the latest Archean magmatic event in the Yinshan Block. These ages of undeformed granitoid dikes delimit the termination of thermo-tectonic development of the Yinshan Block. Based on these new ages and published geological and geochronological data, we conclude that the Yinshan Block is a typical Neoarchean cratonic block, not a segment of the so-called “Paleoproterozoic Inner Mongolia-North Hebei Orogen”. Episodic mantle melting and resultant crustal reworking account for the thermo-tectonic development of the Yinshan Block in a brief period (ca. 2556–2502Ma) in the late Neoarchean, and based on their regional chronological correlations we argue for their craton-scale significance.
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DOI：
--
发表时间：
2004
期刊：
Geology and Mineral Resources of South China
影响因子：
--
作者：
Liu Jun-jie
通讯作者：
Liu Jun-jie
影响因子：
64.8
作者：
S. Shirey;G. Hanson
通讯作者：
S. Shirey;G. Hanson
影响因子：
3.5
作者：
R. Pidgeon
通讯作者：
R. Pidgeon
影响因子：
3.8
作者：
Guochun Zhao;M. Sun;S. Wilde
通讯作者：
Guochun Zhao;M. Sun;S. Wilde
影响因子：
3.9
作者：
R. Rudnick
通讯作者：
R. Rudnick