| 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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| 关键词:monzonitic granite petrogeochemistry Zircon U-Pb Sr-Nd-Pb-Hf isotope southern Miaomiaojing W-Be mineralization |
| 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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| Geochronology, Petrogeochemistry, Sr-Nd-Pb-Hf Isotope Characteristics, and Geological Significance of a Beryllium-tungsten Deposit in Southern Miaomiaojing, Gansu Province |
| 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. |
| CHU Kelei,WANG Jiaxin,FANG Xiang,GUO Dongbao,HUANG Shijun,QI Yongheng.2025.Geochronology, Petrogeochemistry, Sr-Nd-Pb-Hf Isotope Characteristics, and Geological Significance of a Beryllium-tungsten Deposit in Southern Miaomiaojing, Gansu Province[J].Acta Geoscientica Sinica,46(2):299-320. |
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