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| 西大别小罗山钼多金属矿区花岗斑岩脉年代学、岩石地球化学、Sr-Nd-Pb同位素特征及其地质意义 |
| Geochronology, Geochemistry, Sr-Nd-Pb isotopic characteristics and Geological Significance of the Ore-related Granite Porphyry from Xiaoluoshan molybdenum polymetallic deposit in the western Dabie Orogenic Belt |
| 投稿时间：2025-05-19 修订日期：2026-03-23 |
| DOI： |
| 中文关键词: 小罗山钼多金属矿床 花岗斑岩脉 年代学 地球化学 Sr-Nd-Pb同位素 西大别 |
| 英文关键词:Xiaoluoshan molybdenum polymetallic deposit granite porphyry dyke geochronology geochemistry Sr-Nd-Pb isotope Western Dabie Orogen |
| 基金项目:湖北省地质局科研项目“鄂东北地区燕山期岩浆成矿作用与找矿预测研究”(项目编号：KJ2025-31)、湖北省自然科学基金联合(2023AFD230、2024AFD401、2025AFD439)联合资助。 |
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| 中文摘要: |
| 小罗山钼多金属矿床位于西大别灵山岩体南缘，矿体与矿区花岗斑岩脉空间关系密切，多赋存在花岗斑岩脉裂隙或破碎带中，矿化围岩蚀变具有明显的绢英岩化-泥化-青磐岩化等的分带特征，深部具有寻找斑岩型矿体的前景。LA-ICP-MS 锆石U-Pb 定年结果表明，小罗山花岗斑岩脉的成岩年龄为117.66±0.74Ma，为早白垩世中晚期。岩石地球化学数据显示岩石具有高硅（72.75%~78.54%）、高碱（7.99%~9.82%）、准铝质-弱过铝质、高岩石分异指数特征；岩石相对富集轻稀土元素（ΣLREE/ΣHREE为5.94~12.78），Eu负异常明显；微量元素富集Rb、Th等大离子亲石元素，亏损Nb、P、Sr、Ti等高场强元素。岩石锶元素初始比值为Isr=0.708023~0.712109, 钕同位素εNd( t)值变化于?9.6~?8.2之间，TDM2=1.67~1.80 Ga。岩石地球化学和Sr-Nd-Pb同位素特征显示，该区花岗斑岩脉可能是扬子地块北缘中-古元古代古老地壳物质部分熔融的产物，同时岩石源区有区域上大别片麻岩部分熔融物质的贡献，其形成的地球动力学背景为白垩纪构造拆沉作用之后地壳伸展环境。 |
| 英文摘要: |
| The Xiaoluoshan molybdenum-polymetallic deposit occurs along the southern boundary of the Lingshan intrusive complex within the western Dabie orogenic belt. Mineralization exhibits intimate spatial association with granitic porphyry dikes, predominantly hosted within fractures and breccia zones of these intrusive bodies. The alteration mineralogy displays well-defined zoning patterns characterized by sericitization-argillization-pyritization assemblages, suggesting exploration potential for porphyry-style mineralization at depth. High-precision LA-ICP-MS zircon U-Pb geochronology yields an emplacement age of 117.66 ± 0.74 Ma for the granitic porphyry dikes, corresponding to the mid-late Early Cretaceous epoch. Comprehensive petrochemical analyses reveal the following characteristics: (1) elevated SiO? contents (72.75-78.54 wt%) with corresponding high alkali concentrations (7.99-9.82 wt%); (2) metaluminous- to weakly peraluminous compositions; (3) pronounced fractionation indices; (4) light rare earth element enrichment (ΣLREE/ΣHREE = 5.94-12.78) accompanied by significant negative Eu anomalies; (5) enrichment of large-ion lithophile elements (Rb, Th) coupled with depletion of high-field-strength elements (Nb, P, Sr, Ti). Isotopic investigations demonstrate initial 87Sr/87Sr ratios ranging from 0.708023 to 0.712109 (Isr), εNd(t) values between -9.6 and -8.2, and two-stage depleted mantle model ages (TDM?) of 1.67-1.80 Ga.Integrated geochemical and isotopic evidence indicates that these granitic porphyry dikes likely originated through partial melting of Meso- to Paleoproterozoic crustal materials at the northern Yangtze Block margin, with significant contributions from regional Dabie gneiss protoliths. Their formation is interpreted to have occurred in a post-orogenic extensional regime following Cretaceous post-orogenic extension. |
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