| 赣东北珍珠山花岗岩脉地球化学、锆石U-Pb定年及Hf同位素组成研究 |
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| 引用本文： | 刘战庆,刘善宝,裴荣富,王成辉,陈国华,魏锦,张树德,刘小林.赣东北珍珠山花岗岩脉地球化学、锆石U-Pb定年及Hf同位素组成研究[J].大地构造与成矿学,2016(4):823-840. |
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| 作者姓名： | 刘战庆 刘善宝 裴荣富 王成辉 陈国华 魏锦 张树德 刘小林 |
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| 作者单位： | 1. 中国地质科学院矿产资源研究所，北京 100037; 桂林理工大学地球科学学院广西隐伏金属矿产勘查重点实验室，广西桂林 541004;2. 中国地质科学院矿产资源研究所,北京,100037;3. 江西省地质矿产勘查开发局九一二大队,江西鹰潭,335001;4. 崇义章源投资控股有限公司,江西赣州,341300 |
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| 基金项目： | 中央地质勘查基金(2013360010)，国土资源部公益性行业科研专项(201411035)，江西省国土资源厅地质勘查基金(矿[2012]01-06)，桂林理工大学博士科研启动基金(002401003373)，广西隐伏金属矿产勘查重点实验室系统研究课题(13-A-01-04)联合资助。 |
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| 摘 要： | 赣东北塔前–朱溪–赋春成矿带是一条重要的铜、钨、钼多金属成矿带,该成矿带及外围成矿潜力巨大,具有良好的找矿前景。本次选取该带南缘珍珠山出露的两条花岗岩脉为研究对象,开展LA-ICP-MS锆石U-Pb测年、Hf同位素及地球化学研究,对其成因、成岩时代和成矿作用进行约束。结果表明,花岗岩脉锆石的206Pb/238U加权平均年龄为129.3±0.5 Ma(MSWD=0.99)和133.3±0.8 Ma(MSWD=0.29),为早白垩世;花岗岩具有高SiO_2(74.10%~75.78%)、富Na_2O+K_2O(6.99%~7.89%)、富Al_2O_3(13.94%~15.15%)、高FeO~T/MgO值(7.50~12.36)、低CaO(0.31%~0.42%)及贫MgO(0.07%~0.13%)的特征。其中Na_2O/K_2O=3.14~9.09,A/CNK=1.08~1.30,属过铝质碱性岩系列。稀土总量较低,轻、重稀土分异较轻(LREE/HREE平均2.48),具强负Eu异常(δEu平均0.07),呈弱右倾海鸥形态;微量元素Ga/Al值高(3.41×10~(–4)~4.27×10~(–4)),相对亏损K、Ba、Nd、Sr等大离子亲石元素,富集U、Th、Nb、Ta、P等高场强元素。其中锆石εHf(t)值为–5.09~–0.05,显示成岩物质以壳源为主,并有地幔成分参与,Hf单阶段模式年龄范围为761~948 Ma,两阶段模式年龄范围为1153~1463 Ma。综合分析认为珍珠山花岗岩属于A1型花岗岩,是在早白垩世构造体制转换结束后非造山伸展拉张环境下侵位,岩脉中Sn、Nb含量高,暗示该区具有较大的钨锡铌钽矿找矿潜力。
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| 关 键 词： | 赣东北 珍珠山地区 A1型花岗岩 地球化学 锆石U-Pb测年 Hf同位素 |
Geochemistry,Zircon U-Pb Dating and Hf Isotope Composition of Zhenzhushan Granite in Northeast Jiangxi Province |
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| Abstract: | The discovery of the ultra-large skarn-type copper-tungsten deposit in the Taqian-Zhuxi-Fuchun metallogenic belt in Zhuxi, Northeast Jiangxi province, exhibits a huge metallogenic potential and prospect in the belt and its peripheral district. The Zhenzhushan area is located in the south margin of the Metallogenic belt where a number of granite veins exposed. Based on the detailed field geological survey, petrological and geochronological studies, LA-ICP-MS zircon U-Pb dating of two big veins of porphyritic muscovite albite granite yielded weighted average ages of 129.3±0.5 Ma (MSWD=0.99) and 133.3±0.8 Ma (MSWD=0.29), respectively. The granites are rich in SiO2(74.10% ~75.78%), Na2O+K2O (6.99%~7.89%), Al2O3 (13.94%~15.15%), poor in CaO (0.31%~0.42%) and MgO (0.07%~0.13%),with FeOT/MgO ratios of 7.50~12.36, Na2O/K2O ratios vary between 3.14 and 9.09, A/CNK=1.08~1.30, belonging to peraluminous alkaline rock series. The granites are characterized by lowSREE value and weak REE fractionation (LREE/HREE average value is 2.48), and showing weakly right dipping seagull shapes with obvious negative Eu anomalies (δEu average value is 0.07). Moreover, the rocks are characterized by high Ga/Al values (3.41×10–4~4.27×10–4), and relatively depleted in K, Ba, Nd, Sr and other LILEs, yet enriched in U, Th, Nb, Ta, P and other HFSEs. TheεHf(t) values of zircons range from –5.09 to –0.05, indicative of juvenile mantle components contribution. The granites were likely derived from mixed source of crust and mantle. The A1-type features of the granites in the Zhenzhushan area suggest that the area was in an anorogenic extensional setting. In addition, the high contents of Sn and Nb in the dykes implies a great potential for W-Sn-Nb-Ta prospecting in the area. |
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| Keywords: | Northeast Jiangxi province Zhenzhushan region A1-type granite rock geochemistry zircon U-Pb dating Hf isotopic |
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