Age and origin of a Palaeozoic nepheline syenite from northern Shanxi Province, China: U–Pb zircon age and whole-rock geochemical and Sr–Nd isotopic constraints
Age and origin of a Palaeozoic nepheline syenite from northern Shanxi Province, China: U–Pb zircon age and whole-rock geochemical and Sr–Nd isotopic constraints
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DOI：
10.1080/00206814.2011.638436
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发表时间：
2012-07
影响因子：
2.6
通讯作者：
Shen Liu;R. Hu;Shan Gao;Caixia Feng;I. Coulson;Guangying Feng;Yuhong Yang;Youqiang Qi;Chaogui Yang;Liang Tang
中科院分区：
文献类型：
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作者：
Shen Liu;R. Hu;Shan Gao;Caixia Feng;I. Coulson;Guangying Feng;Yuhong Yang;Youqiang Qi;Chaogui Yang;Liang Tang
对紫金山的一组古生代霞石正长岩进行了年代学、地球化学和全岩 Sr-Nd 同位素分析，以表征其年龄和岩石成因。激光烧蚀电感耦合等离子体质谱 U-Pb 锆石分析得出样品 (HYK01) 的一致年龄为 525.7 ± 280 万年。这些侵入岩在 K2O + Na2O 含量（14.3-15.2 wt.%）方面属于正长岩岩浆系列，并且由于其高 K2O 含量（5.42-5.61 wt.%）而属于钾闪岩系列。霞石正长岩的进一步特征是轻稀土元素含量高[(La/Yb) N = 29.1–36.1]；显示适度的负 Eu 异常 (δEu = 0.5–0.6) 和 Rb、Th、U、Pb、Zr 和 Hf 的正异常；缺乏 Ba 和高场强元素（P 和 Ti）。此外，本研究中的所有霞石正长岩均表现出相对较低的放射性 Sr (87Sr/86Sr) i (0.7042–0.7043) 和正 ϵNd (t) (0.7–0.8)。这些结果表明霞石正长岩源自贫乏的大陆地壳。母岩浆在上升过程中可能经历了斜长石、含钛氧化物（例如金红石、钛铁矿和钛矿）、磷灰石和锆石的分级结晶，在最终侵位到高地壳水平之前，地壳污染可以忽略不计。
Geochronological, geochemical, and whole-rock Sr–Nd isotopic analyses were performed on a suite of Palaeozoic nepheline syenites from Zijinshan to characterize their ages and petrogenesis. Laser ablation inductively coupled plasma-mass spectrometry U–Pb zircon analyses yield consistent ages of 525.7 ± 2.8 million years for a sample (HYK01). These intrusive rocks belong to the foid syenite magma series in terms of K2O + Na2O contents (14.3–15.2 wt.%) and to the shoshonitic series based on their high K2O contents (5.42–5.61 wt.%). The nepheline syenites are further characterized by high light rare earth element contents [(La/Yb) N = 29.1–36.1]; show modest negative Eu anomalies (δEu = 0.5–0.6) and positive anomalies in Rb, Th, U, Pb, Zr, and Hf; are depleted in Ba and high field strength elements (P and Ti). In addition, all the nepheline syenites in this study display relatively low radiogenic Sr (87Sr/86Sr) i (0.7042–0.7043) and positive ϵNd (t) (0.7–0.8). These results suggest that the nepheline syenites were derived from depleted continental crust. The parent magmas likely experienced fractional crystallization of plagioclase, Ti-bearing oxides (e.g. rutile, ilmenite, and titanite), apatite, and zircon during ascent, with negligible crustal contamination before final emplacement at a high crustal level.