| 青藏高原东北缘茶卡北山印支期(含绿柱石)锂辉石伟晶岩脉群的发现及Li-Be成矿意义 |
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| 引用本文： | 王秉璋,韩杰,谢祥镭,陈静,王涛,薛万文,白宗海,李善平.青藏高原东北缘茶卡北山印支期(含绿柱石)锂辉石伟晶岩脉群的发现及Li-Be成矿意义[J].大地构造与成矿学,2020(1):69-79. |
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| 作者姓名： | 王秉璋 韩杰 谢祥镭 陈静 王涛 薛万文 白宗海 李善平 |
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| 作者单位： | 青海省地质调查院青藏高原北部地质过程与矿产资源重点实验室 |
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| 基金项目： | 第二次青藏高原综合科学考察研究项目(2019QZKK0702);青海省地质矿产勘查开发局计划项目(青海省乌兰县察汗诺-茶卡北山地区1∶25000地球化学测量);青海省地质勘查基金项目(2018353008kc002)联合资助 |
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| 摘 要： | 青藏高原东北缘茶卡北山地区首次发现锂辉石伟晶岩脉群。这些伟晶岩脉沿宗务隆山南缘断裂北侧密集出露,并呈狭窄带状北西向展布。到目前为止,已发现9条含绿柱石锂辉石伟晶岩脉(Li2O平均品位为1.11%~3.13%,BeO平均品位为0.06%)和13条含绿柱石伟晶岩(BeO平均品位为0.044%~0.056%)。伟晶岩锆石U-Pb测年确定其成岩成矿年龄为217 Ma,含绿柱石伟晶岩具有高SiO2(71.62%~77.34%)、Al2O3(15.57%~17.55%)和富K2O(1.99%~2.02%)、Na2O(6.09%~6.24%),稀土元素总量非常低(ΣREE=5.2~9.1μg/g),轻稀土元素略微富集((La/Yb)N=6.8~10.1),Eu具负异常(δEu=0.25~0.92),具有Cs、Rb、Ta、P和Pb富集,以及Ba、Th、La、Ce、Sr、Nd和Ti的强烈亏损特征。含绿柱石锂辉石伟晶岩具有高SiO2(75.73%~77.34%)、Al2O3(15.58%~17.52%)和富Na2O(3.0%~3.16%)、贫K2O(0.36%~0.79%),稀土元素总量也很低(ΣREE=5.3~6.0μg/g),轻稀土元素略微富集((La/Yb)N=3.1~4.6),Eu具强烈负异常(δEu=0.17~0.23)。相对于含绿柱石伟晶岩,含绿柱石锂辉石伟晶岩更加富集Cs、U、Nb、Ta、Th、Sn和B,更亏损K和P。含绿柱石伟晶岩和含绿柱石锂辉石伟晶岩锆石具有相似的Hf同位素组成,εHf(t)值分布范围在–15.1~–12.9之间,对应的Hf同位素地壳模式年龄tDM2为1.99~2.22 Ga,表明伟晶岩源于全吉地块古元古代地壳物质的重熔再造。茶卡北山(含绿柱石)含绿柱石锂辉石伟晶岩的发现可推断宗务隆山构造带东段是青藏高原北部一条新的、重要的锂铍成矿带,除Li和Be外,Nb、Ta、Cs和Sn可能也是有潜力的成矿元素。
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| 关 键 词： | 含绿柱石锂辉石伟晶岩 含绿柱石伟晶岩 Li-Be成矿 锆石U-Pb年龄 Hf同位素地球化学 青藏高原 |
Discovery of the Indosinian(Beryl-bearing) Spodumene Pegmatitic Dike Swarm in the Chakaibeishan Area in the Northeastern Margin of the Tibetan Plateau: Implications for Li-Be Mineralization |
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| WANG Bingzhang,HAN Jie,XIE Xianglei,CHEN Jing,WANG Tao,XUE Wanwen,BAI Zonghai,LI Shanping.Discovery of the Indosinian(Beryl-bearing) Spodumene Pegmatitic Dike Swarm in the Chakaibeishan Area in the Northeastern Margin of the Tibetan Plateau: Implications for Li-Be Mineralization[J].Geotectonica et Metallogenia,2020(1):69-79. |
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| Authors: | WANG Bingzhang HAN Jie XIE Xianglei CHEN Jing WANG Tao XUE Wanwen BAI Zonghai LI Shanping |
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| Institution: | (Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources,Qinghai Geological Survey Institute,Xining 810012,Qinghai,China) |
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| Abstract: | A spodumene-bearing pegmatitic dike swarm was firstly discovered in the Chakaibeishan area in the northeastern margin of the Tibetan Plateau.These pegmatite dikes are intensively exposed and distributed in a narrow NW band along the northern side of the southern Zongwulong Mountain fault.So far,nine beryl-bearing spodumene pegmatite veins with average Li2O grade of 1.11%?3.13%and 13 beryl-bearing pegmatite veins with average BeO grade of 0.044%?0.056%have been found.Zircon U-Pb dating demonstrated that the pegmatites and mineralization were formed at 217 Ma.The beryl-bearing pegmatites have high SiO2(71.62%?77.34%),Al2O3(15.57%?17.55%),K2O(1.99%?2.02%)and Na2O(6.09%?6.24%)contents,low total rare earth elements(ΣREEs)(5.2–9.1μg/g),relatively enriched light rare earth elements((La/Yb)N=6.8?10.1),negative Eu anomalies(δEu=0.25–0.92),as well as enrichment of Cs,Rb,Ta,P,Pb and depletion of Ba,Th,La,Ce,Sr,Nd,and Ti.The beryl-bearing spodumene pegmatites have high SiO2(75.73%?77.34%),Al2O3(15.58%?17.52%)and Na2O(3.0%?3.16%),low K2O(0.36%?0.79%)andΣREEs(5.3?6.0μg/g),as well as slight enrichment of light rare earth elements((La/Yb)N=3.1?4.6)with strong negative Eu anomalies(δEu=0.17?0.23).Compared with the beryl-bearing pegmatites,the beryl-bearing spodumene pegmatites have higher Cs,U,Nb,Ta,Th,Sn and B,and lower K and P contents.These pegmatites have similar zirconεHf(t)values(from?15.1 to?12.9)and tDM2(1.99?2.22 Ga),indicating the pegmatites possibly originated from remelting of the Paleoproterozoic crustal materials in the Quanji Block.The discovery of the beryl-bearing spodumene pegmatite in the Chakaibeishan area implies that there should be a new and important Li and Be metallogenic belt in the eastern part of the Zongwulong tectonic belt,northern Tibet Plateau.Besides,Nb,Ta,Cs and Sn may also be potential metallogenic elements in the belt. |
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| Keywords: | beryl-bearing spodumene pegmatites beryl-bearing pegmatites Li-Be mineralization zircon U-Pb age Hf isotope geochemistry Tibetan Plateau |
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