| 甘肃庙庙井南铍钨矿年代学、岩石地球化学、Sr-Nd-Pb-Hf同位素特征及其地质意义 |
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| 引用本文：楚克磊,王佳鑫,方 向,郭东宝,黄世军,祁永恒.2025.甘肃庙庙井南铍钨矿年代学、岩石地球化学、Sr-Nd-Pb-Hf同位素特征及其地质意义[J].地球学报,46(2):299-320. |
| DOI：10.3975/cagsb.2024.070401 |
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| 基金项目:甘肃省有色金属地质勘查局局管项目“甘肃省瓜州县庙庙井南钨铍矿成矿与找矿方向研究”(编号: YSJD2022-13)；国家自然科学基金项目(编号: 42102109)；中国地质调查局地质调查项目(编号: DD20243483)；中国科协青年人才托举工程(编号: 2022QNRC001) |
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| 中文摘要:庙庙井南铍钨矿区位于甘肃新疆交界的北山山系, 地处塔里木板块敦煌地块柳园裂谷活动带北缘。该区域关于岩浆成岩成矿的报道较少, 为了查明庙庙井南矿床的矿化特征、花岗岩类型、成因和源区特征, 厘清成岩成矿时代, 探究成岩与成矿的关系, 揭示成矿动力学背景, 本文对庙庙井南矿区的花岗岩开展了系统的岩相学、年代学、岩石地球化学、锆石Lu-Hf、Sr-Nd-Pb同位素等研究。结果表明, 庙庙井南矿区出露岩体主要为二长花岗岩, 锆石U-Pb年龄介于411~404 Ma, 为晚古生代早泥盆世岩浆岩; 富Si、Al, A/CNK介于0.89~0.99, 为准铝质岩石, 里特曼指数2~2.6, 属高钾钙碱性系列; 微量元素富集Rb、U等大离子亲石元素(LILE), 不同程度亏损Nb、Ti等高场强元素(HFSE), 稀土元素配分曲线右倾, 即轻稀土富集(LREE), 重稀土亏损(HREE), 具有较强的负Eu异常; 锆石(176Hf/177Hf)i为0.282 452~0.282 891, εHf(t)介于–2.78 ~ +12.78, 平均值6.35, 中值6.40, TDM2为559~1 544 Ma, 全岩(143Nd/144Nd)i为0.512 092~0.512 210, εNd(t)值为–0.5 ~ +1.8, 平均值0.37, (206Pb/204Pb)i=16.793~18.516, (207Pb/204Pb)i=15.540~15.642, (208Pb/204Pb)i= 36.882~38.484。同位素测试结果显示花岗岩可能来源于具有亏损地幔特征新生下地壳的部分熔融, 并在上升过程中与古元古界北山岩群古老地壳混染。综合研究表明, 庙庙井南矿区花岗岩属于高分异I型花岗岩, 其成因可能与晚古生代早—中泥盆世Zoolen大洋与中亚造山带南部北山造山带俯冲-碰撞有关, 由于Zoolen大洋与柳园微陆块俯冲-碰撞, 产生大量弧后裂谷及弧后盆地, 区域上整体处于弧后伸展构造背景, 软流圈上涌, 提供大量热量, 导致新生下地壳部分熔融, 产生基-中性岩浆沿断裂不断上侵, 与碳酸盐岩围岩接触交代形成矽卡岩型铍钨矿床。 |
| 中文关键词:二长花岗岩 岩石地球化学 锆石U-Pb Sr-Nd-Pb-Hf同位素 庙庙井南 铍钨矿化 |
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| Geochronology, Petrogeochemistry, Sr-Nd-Pb-Hf Isotope Characteristics, and Geological Significance of a Beryllium-tungsten Deposit in Southern Miaomiaojing, Gansu Province |
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| Abstract:The southern Miaomiaojing W-Be deposit is located in the Beishan Mountain system at the border of the Gansu and Xin-jiang and the northern margin of the Liuyuan Rift active belt of the Dunhuang Block and Tarim Plate. There are few re-ports on magmatic diagenesis and mineralization in this region. Here, a systematic study of lithography, chronology, petrogeochemistry, zircon Lu-Hf, and Sr-Nd-Pb isotopes was carried out on the granite in the southern Miaomiaojing mining area to understand the mineralization characteristics of the southern Miaomiaojing deposit, including the types, genesis, and source characteristics of granite, to clarify the diagenesis and mineralization age, explore the relationship be-tween diagenesis and mineralization, and reveal the metallogenic dynamic background. Results show that the ex-posed rock mass is mainly monzonitic granite, and the age of zircon U-Pb is 411–404 Ma, which is Late Paleozoic and Early Devonian magmatic rock. The enrichment of Si and Al elements resulted in A/CNK values ranging from 0.89 to 0.99, indicating quasi-aluminous rocks. The Rittman index is 2–2.6, suggesting that these rocks belong to the high potassium calc-alkaline series. Large ion-lithophilic elements, such as Rb and U, are enriched in trace elements, and high field-strength elements such as Nb and Ti are depleted to varying degrees. The distribution curve of rare earth elements is skewed to the right; that is, light rare earth elements are enriched, and heavy rare earth elements are depleted, with a strong negative Eu anomaly. Zircon (176Hf/177Hf)i ranges from 0.282 452 to 0.282 891, εHf(t) ranges from –2.78 to +12.78, with an average value of 6.35 and a median value of 6.40. TDM2 ranges between 559 and 1 544 Ma. (143Nd/144Nd)i ranges from 0.512 092 to 0.512 210, εNd(t) values range from –0.5 to +1.8, with an average value of 0.37, (206Pb/204Pb)i ranges be-tween 16.793 and 18.516, (207Pb/204Pb)i ranges from 15.540 to 15.642, and (208Pb/204Pb)i ranges between 36.882 and 38.484. The isotope test results showed that the granite may have been derived from the partial melting of the new lower crust with the characteristics of a depleted mantle and mixed with the old crust of the Paleoproterozoic Beishanite group during the ascent. Comprehensive studies have shown that the granite in the southern Miaomiaojing mining area is a high-differentiation type I granite, and its genesis may be related to the subduction-collision of the Zoolen and Beishan orogenic belts in the southern Central Asia orogenic belt in the Early and Middle Devonian of the Late Paleozoic. The en-tire area is in the back arc extension-tectonic background, where the upsurge of the asthenosphere provided extreme heat, leading to the partial melting of the new lower crust. This resulted in the continuous invasion of basic-neutral magma along the fault and contact metasomatism with the surrounding carbonate rock, forming a skarn-type W-Be deposit. |
| keywords:monzonitic granite petrogeochemistry Zircon U-Pb Sr-Nd-Pb-Hf isotope southern Miaomiaojing W-Be mineralization |
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