| 祁连地块西段硫磺矿北花岗闪长岩的岩石成因及其地质意义:年代学、地球化学及Hf同位素证据 |
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| 引用本文： | 陶刚,朱利东,李智武,欧阳慧子,解龙,杨文光,杨珍.祁连地块西段硫磺矿北花岗闪长岩的岩石成因及其地质意义:年代学、地球化学及Hf同位素证据[J].地球科学,2017,42(12):2258-2275. |
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| 作者姓名： | 陶刚 朱利东 李智武 欧阳慧子 解龙 杨文光 杨珍 |
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| 作者单位： | 1.成都理工大学沉积地质研究院, 四川成都 610059 |
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| 基金项目： | 中国地质调查项目12120113033004高等学校博士学科点专项科研基金资助项目20125122110010冈底斯-喜马拉雅铜矿资源基地调查项目DD20160015 |
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| 摘 要： | 祁连地区与Rodinia超大陆汇聚有关的新元古代岩浆活动越来越受到地质学者的关注和研究.对硫磺矿北花岗闪长岩体进行了锆石LA-ICP-MS U-Pb定年，结果显示岩体锆石U-Pb年龄加权平均值为926±4 Ma，表明其形成时代新元古代早期.花岗闪长岩的SiO2为59.47%~62.96%，P2O5为0.12%~0.14%，铝饱和指数（A/CNK）为1.01~1.15，主要为一套弱过铝质的高钾钙碱型系列，具Ⅰ型花岗岩的特征.稀土元素总量在118.80×10-6~253.07×10-6之间，（La/Yb）N为7.87~16.17，明显富集轻稀土，具有中等-强Eu负异常（δEu=0.33~0.68），稀土元素配分图呈右倾型特征；微量元素上具有富集大离子亲石元素和不相容元素（Rb、Th和U），亏损高场强元素Nb、Ta、Ti、Sr和P的特征；Nb/Ta、La/Nb、Nb/U及Sm/Nd比值整体反映花岗闪长岩壳源特点；硫磺矿北花岗闪长岩体εHf（t）主要在0~7之间，二阶段地壳模式年龄主要在1 247~1 801 Ma之间.结合区域新元古代岩浆活动认为硫磺矿北花岗闪长岩体形成于活动大陆边缘，而硫磺矿北花岗闪长岩为中元古代增生的年轻地壳部分熔融的产物，经历一定程度分离结晶，可能也有古老地壳部分熔融成分参与该岩体形成.同时，该时期岩浆活动可能为祁连地块在中新元古代时期对全球Rodinia超大陆聚合事件的响应，进一步为祁连地块属性提供可信研究资料.
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| 关 键 词： | 祁连地块 花岗闪长岩 锆石U-Pb年龄 Lu-Hf同位素 新生地壳 罗迪尼亚超大陆 地球化学 |
| 收稿时间： | 2017-03-15 |
Petrogenesis and Geological Significance of the North Liuhuangkuang Granodiorite in the West Sement of the Qilian Terrane: Evidences from Geochronology,Geochemistry, and Hf Isotopes |
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| Abstract: | More geological researchers are focusing on the Neoproterozoic magmatic activities of Qilian Terrane and little chronological and geochemical materials are about the North Liuhuangkuang Granodiorites (NLG) in the western segment of Qilian Terrane.The zircons of rock samples which havedistinct rhythmic growth zoning are long cylindrical and euhedral well, implying the features of magmatic origin. The resultsof dating indicate that the rocks were formed in the Early Neoproterozoic (926±4 Ma).11 samples' new whole-rock geochemical analysis results have SiO2 content of 59.47%~62.96%, P2O5 content of 0.12%~0.14% with A/CNK values of 1.01~1.15, which showed that the NLG were high-K calc-alkaline with characteristics of I-type. The ∑REE content was between 118.80×10-6 and 253.07×10-6, with (La/Yb)N ratio of 7.87~16.17 and δEu (0.89~1.03). The REE diagram showed rightward incline and mid-negative weekly negative Eu abnormity. The NLG were enriched in large-ion lithophile elements:Rb, Th, U, LREE and depleted in high field strength elements:Nb, Ta, Ti, P. The ratios of Nb/Ta, La/Nb, Nb/U and Sm/Nd show crustal characteristics. The Hf isotopes showed that the εHf(t) of NLG mainly ranged from 0 to 7 and its crustal model ages were between 1 247 Ma and 1 801 Ma. With the regional magmatic activities, the NLG probably were formed in a subduction tectonic environment of continental margin arc and it suggested that the primary magma was derived from the remelting of juvenile crustal materials in Mesoproterozic, experiencinga certain extent of fractional crystallization. Otherwise, the melting of the ancient crust also probably participated the formation of the NLG. The NLG magma activities may the response of the converge of the Rodinia Supercontinental, during the Neoproterozoic, which provided the attribute of the Qilian Terrane with credible research materials. |
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