Late Triassic intrusive complex in the Jidong region, Jiamusi-Khanka Block, NE China: Geochemistry, zircon U-Pb ages, Lu-Hf isotopes, and implications for magma mingling and mixing
Late Triassic intrusive complex in the Jidong region, Jiamusi-Khanka Block, NE China: Geochemistry, zircon U-Pb ages, Lu-Hf isotopes, and implications for magma mingling and mixing
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中国东北佳木斯-兴卡地块冀东地区晚三叠世侵入杂岩：地球化学、锆石U-Pb年龄、Lu-Hf同位素以及对岩浆混合和混合的影响
DOI：
10.1016/j.lithos.2015.03.001
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发表时间：
2015
期刊：
影响因子：
3.5
通讯作者：
Yu Jiejiang
中科院分区：
文献类型：
--
作者：
Yang Hao;Ge Wenchun;Zhao Guochun;Dong Yu;Xu Wenliang;Ji Zheng;Yu Jiejiang
本文报道了中国东北佳木斯-坎卡地块冀东地区晚三叠世侵入杂岩的全岩主量元素和微量元素地球化学、锆石U-Pb年龄和Lu-Hf同位素组成。微粒闪长岩和石英闪长岩包体的锆石U-Pb年龄为211~208 Ma，寄主花岗岩的年龄为211~209 Ma。这些年龄与东亚边缘先前建立的一次强烈的晚三叠世岩浆事件有关。野外观察，加上岩石学特征、地球化学和锆石Hf同位素数据，排除了简单的晶体分馏或热铁矿混合作为侵入杂岩中各种岩石类型的成因联系的可能性。正长花岗岩套具有高的SiO_2(75.5~76.3%)和低的MgO(0.15~0.19%)，并产生丰富的LILE和LREE配分模式。正长花岗岩中的大多数锆石具有766 Ma和1461 Ma的两个阶段的模式年龄，以及正εHf(T)值+60.6-+9.1。这些结果表明，花岗岩类岩浆是中-新元古代下地壳部分熔融形成的。辉长岩套的二氧化硅含量范围有限(46.1-51.9wt%)，镁#值高(49-70)，镍、钴、铬含量高。两个闪长岩样品的单阶段Hf模式年龄为557~787Ma，εHf(T)值为+11.9~+88.3，与冀东地区已研究的同时代辉长岩一致。这些特征，再加上辉长岩均富含轻稀土和大分子稀土元素，表明镁铁质岩浆来源于新元古代岩石圈亏损地幔的熔融作用，这些岩石圈地幔已被板片流体交代。认为晚三叠世侵入杂岩中的主要火成岩是由长英质岩浆和镁铁质岩浆混合/混合形成的。地球化学资料结合区域地质调查表明，晚三叠世侵入杂岩形成于岩石圈伸展过程中，是佳木斯-坎卡地块下方向西俯冲的跃金山大洋板块向西俯冲导致的板片剥离所致。
Whole-rock major and trace element geochemistry together with zircon U–Pb ages and Lu–Hf isotope compositions are reported for a Late Triassic intrusive complex in the Jidong region, Jiamusi–Khanka Block, NE China. Zircon U–Pb dating yields ages between 211 and 208 Ma for enclaves of microgranular diorite and quartz diorite, and between 211 and 209 Ma for the host granitoids. These ages correlate with a previously established intensive Late Triassic magmatic event along the eastern Asian margin. Field observations, together with petrographic features, geochemistry, and zircon Hf isotope data, preclude simple crystal fractionation or restite unmixing as a genetic link for the various rock types within the intrusive complex. The syenogranite suite has high SiO2(75.5–76.3 wt.%) and low MgO (0.15–0.19 wt.%), and yields enriched LILE and LREE patterns. Most of the zircons in the syenogranites have two-stage model ages of 766 and 1461 Ma, together with positiveεHf(t) values of + 0.6 to + 9.1. These results indicate that the granitoid magmas were generated by partial melting of Meso- to Neoproterozoic lower crust. The gabbro suite has a restricted range of SiO2(46.1–51.9 wt.%) together with high Mg# values (49–70) and high concentrations of Ni, Co, and Cr. Zircons from two diorite samples have single-stage Hf model ages of 557–787 Ma andεHf(t) values of + 1.9 to + 8.3 that are consistent with the coeval gabbros previously studied in the Jidong region. These features, together with the observation that all the gabbros are enriched in LREE and LILE, suggest that the mafic magmas were derived from melting of depleted Neoproterozoic lithospheric mantle that had been metasomatized by slab-derived fluids. It is concluded that the dominant igneous suites within the Late Triassic intrusive complex formed by mingling/mixing of felsic and mafic magmas. The geochemical data, combined with regional geological investigations, indicate that the Late Triassic intrusive complex formed during lithospheric extension caused by slab break-off of the Yuejinshan oceanic plate that was subducting westward beneath the Jiamusi–Khanka Block.