| 青海不同矿区软玉地球化学特征及Ar-Ar定年研究 |
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| 引用本文： | 于海燕,阮青锋,廖宝丽,李东升.青海不同矿区软玉地球化学特征及Ar-Ar定年研究[J].岩石矿物学杂志,2018,37(4):655-668. |
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| 作者姓名： | 于海燕 阮青锋 廖宝丽 李东升 |
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| 作者单位： | 桂林理工大学地球科学学院 |
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| 基金项目： | 广西自然科学基金资助项目（2014GXNSFAA118307）；桂林理工大学博士科研启动经费（002401003554） |
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| 摘 要： | 为了探讨青海软玉的成矿物质来源、成矿环境及成矿年代,对三岔口矿点、拖拉海沟矿点及大灶火矿点的样品进行了主量元素、微量元素、稀土元素及Ar-Ar法定年的测试。结果显示,软玉样品的主量元素变化不大,与透闪石的理论值相符;微量元素差异较大,说明不同矿点成矿环境不同;稀土元素总量较低(0.29×10-6~40.72×10-6),Eu中度负异常(0.49~0.84),除大灶火青玉样品具左倾的重稀土元素富集模式(La/Yb)N=0.16~0.61]外,其他样品都具有右倾的轻稀土元素富集模式,(La/Yb)N=2.87~6.34。三岔口矿点、拖拉海沟矿点软玉样品的稀土元素分配曲线与纳赤台基性辉长岩相似,大灶火矿点黄玉的稀土元素分配模式与二长花岗岩相似,而青玉的分配模式与斜长花岗岩相似。样品的~TAl~(3+)、~CAl~(3+)和Ti含量变化表明,翠青玉的成矿温度最高、压力最大,黄玉成矿温度较高、压力较大;烟青玉和青玉成矿温度较高、压力较低;白玉、青白玉和糖玉成矿温度较低、压力较低。翠青玉和黄玉中明显较低的Zr/Hf、Nb/Ta和Sr/Ba值提示其成矿环境酸性明显加强。3个矿点样品的成矿年代301.38~237.28 Ma介于晚石炭世—中三叠世之间,属于印支-海西运动阶段。成矿年代均晚于侵入岩形成年代,说明矿体经历了多次热液交代过程。
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| 关 键 词： | 软玉 微量元素 稀土元素 成矿年代 成矿环境 |
| 收稿时间： | 2017/8/7 0:00:00 |
Geochemical characteristics and Ar-Ar dating of different deposits in Qinghai Province |
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| YU Hai-yan,RUAN Qing-feng,LIAO Bao-li and LI Dong-sheng.Geochemical characteristics and Ar-Ar dating of different deposits in Qinghai Province[J].Acta Petrologica Et Mineralogica,2018,37(4):655-668. |
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| Authors: | YU Hai-yan RUAN Qing-feng LIAO Bao-li and LI Dong-sheng |
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| Institution: | College of Earth Sciences, Guilin University of Technology, Guilin 541004, China,College of Earth Sciences, Guilin University of Technology, Guilin 541004, China,College of Earth Sciences, Guilin University of Technology, Guilin 541004, China and College of Earth Sciences, Guilin University of Technology, Guilin 541004, China |
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| Abstract: | In order to explore the metallogenetic substances, environment and ore-forming age of Sanchakou, Tuolahaigou and Dazaohuo nephrite deposits in NS-trending metallogenic belt of Qinghai, the authors conducted Ar-Ar dating and analysis of major elements, trace elements and rare earth elements (REE). Major elements analysis shows little change in all samples from three deposits, which is in accordance with theoretical value of tremolite. The content of rare-earth elements in all samples is generally lower (0.29×10-6~40.72×10-6), with moderately negative Eu anomalies (0.49~0.84). Except for green nephrite, the chondrite-normalized REE patterns of samples exhibit relative light REE (LREE) enrichment and right-declined REE distribution patterns, with (La/Yb)N values ranging from 2.87 to 6.34. Green nephrite samples are characterized by the enrichment of heavy REE (HREE) in the left-declined REE distribution patterns, with (La/Yb)N values ranging from 0.16 to 0.61. REE distribution curves of samples from Sanchakou and Tuolahaigou nephrite deposits are similar to the patterns of Nachitai basic gabbro, and yellow nephrite samples from Dazaohuo deposit in northern metallogenic belt are similar to monzonitic granite, whereas green nephrite samples are similar to plagiogranite. The results indicate the source of mineralization of different deposits. The change of the content of Ti and Al2O3 in the sample shows changes in metallogenic temperature and pressure. The ratios of Zr/Hf, Nb/Ta and Sr/Ba in viridite and yellow nephrite samples are significantly lower than those of other samples, indicating that the alkalinity of metallogenic environment was obviously enhanced. The Ar-Ar dating shows that ore-forming ages of three deposits (301.38~237.28 Ma) are between Late Devonian to Middle Triassic, later than the geological age of intrusive rocks. The results indicate that Qinghai nephrite was mainly formed in the Hercynian-Indochina period, corresponding to multiple mineralization processes. |
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| Keywords: | nephrite trace elements rare-earth elements ore-forming age metallogenic environment |
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