Crust-mantle geodynamic origin of similar to 2.7 Ga granitoid diversification in the Jiaobei terrane, North China Craton
Crust-mantle geodynamic origin of similar to 2.7 Ga granitoid diversification in the Jiaobei terrane, North China Craton
复制标题
华北克拉通胶北地体类似2.7 Ga花岗岩类多样化的壳幔地球动力学成因
DOI：
10.1016/j.precamres.2020.105821
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发表时间：
2020
影响因子：
3.8
通讯作者：
Lishuang Guo
中科院分区：
文献类型：
--
作者：
Jiachen Yao;Wei Wang;Shuwen Liu;Peter A. Cawood;Pengbo Niu;Denggang Lu;Lishuang Guo
全球晚太古代花岗岩类分异的壳幔动力学成因仍然是个谜。在华北北部胶北地区新太古代早期新发现了一系列花岗岩类，包括~2749-2739 Ma富钠石英闪长质、英云闪长质和奥长花岗质（DTTG）片麻岩，~2718-2701 Ma富钾石英二长闪长质、花岗闪长质和二长花岗质片麻岩。它们具有低K2 O/Na 2 O（0.19-0.59），并具有MgO、FeOT、TiO 2、P2 O 5和CaO减少，Eu异常由负变正，以及更多分馏的稀土元素，随着SiO2增加的特征。石英闪长岩和TTG片麻岩均具有亏损锆石εHf（t2）值（+1.4至+7.0）。通过定量成岩建模，调用分离结晶模型，即，石英闪长质片麻岩是由亏损地幔源部分熔融而成，并被板状熔体交代，而TTG片麻岩（低硅和高硅组）则是由石英闪长质岩浆不同程度分馏而成，推测液相线矿物为角闪石、单斜辉石、斜长石和磷灰石。相比之下，富钾花岗岩类显示出较高的K2 O/Na 2 O（0.69-2.87），其中一些含有自形白云母。石英二长闪长质和花岗闪长质片麻岩比二长花岗质片麻岩具有更高的MgO和Mg#，但Fe*（FeOT/（FeOT+ MgO））较低。锆石εHf（t2）值（-0.5 ~+5.6）低于DTTG片麻岩。这些富钾花岗岩可能是地幔交代源区部分熔融形成的重建了胶北地区新太古代早期壳幔相互作用，包括：（1）早期陆缘弧下的板幔楔相互作用，形成石英闪长岩及其衍生的英云闪长岩和奥长闪长岩;（2）持续的汇聚作用导致弧山高度起伏，有利于沉积物的侵蚀和再加工/再循环;（3）上述弧系统与区域~ 2.9Ga或更老的陆核之间的增生作用导致壳幔耦合系统的部分熔融，产生不同的富钾花岗岩类。强调加厚弧的建造和侵蚀有利于高压TTG和富钾花岗岩类的形成，导致全球晚太古代花岗岩类的多样化。
The crust-mantle geodynamic origin of global late Archean granitoid diversification remains enigmatic. A series of early Neoarchean diversified granitoids were newly identified in the Jiaobei terrane of the North China Craton, including ~2749–2739 Ma Na-rich quartz dioritic, tonalitic, and trondhjemitic (DTTG) gneisses, and ~2718–2701 Ma K-rich quartz monzodioritic, granodioritic, and monzogranitic gneisses.The quartz dioritic and TTG gneisses commonly show transitional field relationships. They have low K2O/Na2O (0.19–0.59), and are characterized by decreasing MgO, FeOT, TiO2, P2O5, and CaO, changing Eu anomalies from negative to positive, and more fractionated REEs, with increasing SiO2. Both the quartz dioritic and TTG gneisses possess depleted zircon εHf(t2) values (+1.4 to + 7.0). Through quantitative petrogenetic modeling, a fractional crystallization model is invoked, i.e., the quartz dioritic gneisses were derived from partial melting of a depleted mantle source metasomatized by slab-derived melts, whereas TTG gneisses (a low silica and a high silica group) formed by different degrees of fractionation from the quartz dioritic magmas, with inferred liquidus minerals of hornblende, clinopyroxene, plagioclase, and apatite. In comparison, the K-rich granitoids show higher K2O/Na2O (0.69–2.87), with some containing euhedral muscovites. The quartz monzodioritic and granodioritic gneisses have higher MgO and Mg#, but lower Fe* (FeOT/(FeOT+ MgO)) than the monzogranitic gneisses. The zircon εHf(t2) values (-0.5 to + 5.6) are lower than those of DTTG gneisses. It is suggested that these K-rich granitoids formed by partial melting of either a metasomatized mantle source (with recycled sediments) or metasedimentary rocks at diverse crustal levels.Early Neoarchean crust-mantle interactions of the Jiaobei terrane are reconstructed, including (1) earlier slab-mantle wedge interactions under a continental marginal arc, forming quartz dioritic and the derivative tonalitic and trondhjemitic rocks; (2) ongoing convergence led to high relief of the arc mountain, facilitating erosion and reworking/recycling of sediments; and (3) partial melting of coupled crust-mantle system following accretion between the above arc system and regional ~2.9 Ga or older continental nucleus generated different K-rich granitoids. It is emphasized that the construction and erosion of thickened arcs are prone to the formation of both high pressure TTGs and K-rich granitoids, leading to the late Archean granitoid diversification globally.