| 惠卫东.甘肃北山白山堂矿区流纹斑岩的U-Pb年代学、地球化学特征及其地质意义[J].地质与勘探,2013,49(3):484-495 |
| 甘肃北山白山堂矿区流纹斑岩的U-Pb年代学、地球化学特征及其地质意义 |
| Rhyolite Porphyry in the Baishantang Mine, Gnasu and Their Geological Implications |
| 投稿时间：2012-09-16 修订日期：2013-12-08 |
| DOI： |
| 中文关键词: U-Pb年龄 地球化学 流纹斑岩 岩石成因 白山堂 |
| 英文关键词: zircon U-Pb dating, geochemistry, rhyolite porphyry, petrogenesis, Baishantang mine |
| 基金项目:国家科技支撑计划重点项目（编号2007BA25B04和2011BAB06B04-05）资助。 |
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| 中文摘要: |
| [摘要] LA-ICP-MS锆石U-Pb定年结果表明，甘肃北山南部白山堂矿区流纹斑岩的形成年龄为374.9±2.3Ma(MSWD=1.5)。地球化学特征显示为钙碱性、过铝质的流纹斑岩特征，具高硅(70%～74%)、高钾(4.34%～8.75%)和低钙（0.13%～1.16%）含量特点，铝饱和指数A /CNK为1.12～1.65，稀土配分曲线上表现为左高右低的特征，负Eu异常明显，大离子亲石元素相对富集，Nb, Ta, Sr, P, Ti亏损。地球化学特征结合前人Sr-Nd同位素分析认为，该岩体起源于古老的地壳物质部分熔融。非常低Sr高Yb的特征表明岩体形成压力较低，深度较浅，全岩锆石饱和温度约为750℃。结合区域地质分析认为，该岩体与北山南部柳园埃达克岩、墩墩山地区岛弧火山岩具有一致的成岩年龄，形成于陆缘火山弧环境。 |
| 英文摘要: |
| Abstract: The LA-ICP-MS zircon U-Pb dating yields a 206Pb/238U age of 394.9 ± 2.3Ma (MSWD =1.5) for rhyolite porphyry in the Baishantang mine, Gansu, implying its Late Devonian intrusion. Geochemistry analyses show that the rocks are typically potassium-rich (K2O=4.34%～8.75%) and peraluminous (A/CNK= 1.12～1.65). REE is characterized by obvious negative Eu anomalies. The elements K, Rb, Ba, U and Pb are rich in the rhyolite while Nb, Ta, Sr, P, Ti are depleted. The geochemical data, coupled with the published Sr-Nd isotopic analysis, indicate that the Baishantang rhyolite was most likely generated by partial melting of the old crust material. We propose that the rhyolite was formed at a continental volcanic arc that was closely related to subduction. |
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