Geochemical and Sr–Nd–Hf–O isotopic constraints on the source and petrogenesis of the Xiangshuigou silicic alkaline igneous complex from the northern margin of the North China Craton
Geochemical and Sr–Nd–Hf–O isotopic constraints on the source and petrogenesis of the Xiangshuigou silicic alkaline igneous complex from the northern margin of the North China Craton
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地球化学和Sr-Nd-Hf-O同位素对华北克拉通北缘响水沟硅质碱性火成杂岩的来源及岩石成因的制约
DOI：
10.1016/j.lithos.2020.105866
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发表时间：
2020-12
期刊：
影响因子：
3.5
通讯作者：
Wu Ya-Dong
中科院分区：
文献类型：
--
作者：
Zhu Yu-Sheng;Yang Jin-Hui;Wang Hao;Xu Lei;Li Rui;Wu Ya-Dong
本文报道了华北陆缘北方响水沟碱性岩浆杂岩的真渗析体和锆石U-Pb年龄、全岩地球化学、Sr-Nd-Hf和锆石Hf-O同位素数据。我们利用这些数据来研究这些碱性火成岩的来源和岩石成因以及NCC的岩石圈地幔演化。响水沟杂岩由霞石和斑状正长岩组成，不含镁铁质或中间岩。锆石和eudialyte U-Pb测年得到一致的年龄为227-219 Ma的这些岩石。响水沟杂岩碱性岩浆岩均富含Na_2 O、Al_2 O_3、Rb、Th、Zr，而MgO、CaO、P_2O_5、Ba含量较低，并富含大离子亲石元素和轻稀土元素。这些岩石并不缺乏高场强元素。全岩Nd-Hf同位素组成略有富集，εNd（t）= −3.7 ~ −3.0，εHf（t）= −3.1 ~+0.6。锆石Hf-O同位素分析得出εHf（t）和δ 18 O值分别为−0.6至−6.0和+5.1‰至+6.0‰。这些地球化学和同位素特征表明，中碱性岩浆岩是由富集的岩石圈地幔源在经历长期的两阶段分离结晶之前的部分熔融形成的。响水沟杂岩的岩石圈地幔源区不同于古生代的超高压岩石圈地幔，在碱性岩浆作用前经历了亏损的幔源含碳酸盐物质的地幔交代作用。这表明，除了俯冲地壳熔体/流体，软流圈衍生的物质也参与修改岩石圈地幔的北方NCC。因此，我们的工作不仅证实了利用全岩地球化学和Sr-Nd-Hf-O同位素资料揭示中碱性岩浆岩成因的有效性，而且还论证了北方北CC在晚古生代-早中生代的多次改造作用。
We present eudialyte and zircon U–Pb ages, whole-rock geochemical, and Sr–Nd–Hf and zircon Hf–O isotope data for the Xiangshuigou silicic alkaline igneous complex from the northern margin of the North China Craton (NCC). We use these data to investigate the source and petrogenesis of these alkaline igneous rocks and the lithospheric mantle evolution of the NCC. The Xiangshuigou complex consists of nepheline and porphyritic syenites without associated mafic or intermediate rocks. Zircon and eudialyte U–Pb dating yielded consistent ages of 227–219 Ma for these rocks. All the alkaline igneous rocks from the Xiangshuigou complex have high Na2O, Al2O3, Rb, Th, and Zr, and low MgO, CaO, P2O5, and Ba contents, and are enriched in large-ion lithophile and light rare earth elements. These rocks are not depleted in high-field-strength elements. Whole-rock Nd–Hf isotopic compositions are slightly enriched, with εNd(t) = −3.7 to −3.0 and εHf(t) = −3.1 to +0.6. Zircon Hf–O isotope analyses yielded εHf(t) and δ18O values of −0.6 to −6.0 and +5.1‰ to +6.0‰, respectively. These geochemical and isotopic features suggest that the silicic alkaline igneous rocks were derived by partial melting of an enriched lithospheric mantle source before experiencing protracted two-stage fractional crystallization. The lithospheric mantle source of the Xiangshuigou complex was distinct from the Paleozoic cratonic lithospheric mantle and experienced mantle metasomatism by depleted mantle-derived carbonate-bearing materials prior to the alkaline magmatism. This indicates that, in addition to subducted crustal melts/fluids, asthenosphere-derived materials were also involved in modifying the lithospheric mantle of the northern NCC. As such, our work not only approves the effectivity of using whole-rock geochemistry and Sr–Nd–Hf–O isotopic data to reveal origin of the silicic alkaline igneous rocks, but also argues for a multiple modification for the northern NCC during the late Paleozoic to early Mesozoic.
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