| 豫西崤山小妹河岩体LA-ICP-MS锆石U-Pb定年、地球化学特征及地质意义 |
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| 引用本文： | 梁 涛,卢 仁.豫西崤山小妹河岩体LA-ICP-MS锆石U-Pb定年、地球化学特征及地质意义[J].地质通报,2015,34(8):1526-1540. |
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| 作者姓名： | 梁 涛 卢 仁 |
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| 作者单位： | 1.河南省有色金属地质勘查总院，河南 郑州 450052；2.河南省有色金属深部找矿勘查技术研究重点实验室，河南 郑州 450052 |
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| 基金项目： | 河南省国土资源厅科技攻关项目（编号：2011-622-25、2011-622-36、2014-06）、河南省有色金属地质矿产局科研项目（编号：YSDK2013-08、YSDK2012-03） |
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| 摘 要： | 对豫西崤山北部的小妹河岩体中的黑云母石英二长岩进行了LA-ICP-MS锆石U-Pb定年,30个锆石测点中有23个测点的U-Pb同位素测定值位于或接近一致线,年龄值集中于2644~2695Ma、2490~2546Ma、2367Ma、1844~1859Ma、143.6Ma和129.6~133.8Ma 6个年龄段内。最新年龄段内的9个锆石测点206Pb/238U年龄加权平均值为131.5±0.9Ma,代表了小妹河岩体的形成时代。23颗锆石的U–Pb年龄形成了一个新太古代—早白垩世的锆石年龄谱,区域上均存在与之对应的岩浆热事件。小妹河岩体具有富碱、贫镁的特征,属于高钾钙碱性系列;其稀土元素配分模式显示富集轻稀土元素、亏损重稀土元素,(La/Yb)N值为18.36~24.78,无明显Eu异常;微量元素蛛网图显示Nb、Ta槽及P、Ti负异常。小妹河岩体样品高Sr、低Yb及Y,具有埃达克岩属性,是加厚大陆下地壳的部分熔融形成的,部分熔融源区残余相矿物包括石榴子石和金红石。小妹河岩体形成的构造背景为早白垩世岩石圈拆沉作用,由此触发的岩浆(流体)混合作用成就了小妹河岩体的锆石U-Pb年龄谱。小妹河岩体的形成时代与小秦岭-崤山-熊耳山地区早白垩世广泛而强烈的成岩成矿时代接近,岩石圈拆沉作用利于深部含矿流体快速释放,小妹河岩体及其周缘应当具有较大的成矿潜力,应当被视为崤山北部的找矿靶区之一。
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| 关 键 词： | 小妹河岩体 LA-ICP-MS锆石U-Pb年龄 埃达克质 岩石圈拆沉 成矿潜力 崤山 |
LA-ICP-MS zircon U-Pb dating, geochemical features and geological implications of Xiaomeihe rock mass in Xiaoshan Mountain, western Henan Province |
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| LIANG Tao,LU Ren.LA-ICP-MS zircon U-Pb dating, geochemical features and geological implications of Xiaomeihe rock mass in Xiaoshan Mountain, western Henan Province[J].Geologcal Bulletin OF China,2015,34(8):1526-1540. |
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| Authors: | LIANG Tao LU Ren |
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| Abstract: | The Xiaomeihe rock mass lies in northern Xiaoshan Mountain. In this study, sample XMH01 of biotite quartz monzonite was analysed by LA-ICP-MS. 30 zircon spots were analyzed, and results of 23 spots are adjacent to 207Pb/235U-206Pb/238U in the concordia diagram, with U-Pb ages clustered in 2644~2695Ma, 2490~2546Ma, 2367Ma, 1844~1859Ma, 143.6Ma and 129.6~133.8Ma. The weighted average 206Pb/238U age of 9 zircon spots ranging from 129.6Ma to 133.8Ma is 131.5±0.9Ma, which is regarded as the formation age of the Xiaomeihe rock mass. The ages of total 23 U-Pb zircon spots of the Xiaomeihe rock mass formed a zircon age spectrum from late Archean to early Cretaceous, which recorded the corresponding regional magmatic theramal events. The Xiaomeihe rock mass is characterized by higher alkali and lower MgO. Compositional spots of the Xiaomeihe rock mass fall into the high-K calc-alkaline series. In chondrite-normalized REE patterns, the characteristics of LREE enrichment and HREE depletion without obvious Eu anomaly have been shown. The (La/Yb)N ratios are from 18.36 to 24.78. In the spider diagram, negative anomalies of Nb, Ta, P and Ti are displayed. Samples of the Xiaomeihe rock mass have higher Sr and lower Yb and Y, suggesting adakitic granite. The Xiaomeihe rock mass originated from partial melting of the thickened lower crust, and its residual phases of partial melting source included garnet and rutile. The Xiaomeihe rock mass was the product of lithosphere delamination in the early Cretaceous, and magma (fluid) mixing triggered by it formed the zircon U-Pb age spectrum. The formation of the Xiaomeihe rock mass was close to the Early Cretaceous extensive and intense mineralization and diagenetic epoch of Xiaoqinling-Xiaoshan Mountain-Xiong'er Mountain area, during which deep fluids were rapidly discharged in the process of lithosphere delamination. It is concluded that the Xiaomeihe rock mass possesses endogenetic metallogenic potential and hence should be considered as one of the prospecting targets in northern Xiaoshan Mountain area. |
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| Keywords: | Xiaomeihe rock mass LA-ICP-MS zircon U-Pb ages adakitic lithosphere delamination metallogenic potential Xiaoshan Mountain |
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