| 锆石U-Pb年龄及地球化学特征对成矿作用的指示——以鄂东地区阮家湾钨铜钼矿床为例 |
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| 引用本文：周润杰,周 豹,文 广,孙 悦,吴昌雄,朱 金,尚世超,李柏村,廖 旺,宋威方,刘晓阳,程孝增.2025.锆石U-Pb年龄及地球化学特征对成矿作用的指示——以鄂东地区阮家湾钨铜钼矿床为例[J].地球学报,46(4):800-814. |
| DOI：10.3975/cagsb.2024.123001 |
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| 作者 | 单位 | E-mail | | 周润杰 | 湖北省地质调查院, 湖北武汉 430034；资源与生态环境地质湖北省重点实验室, 湖北武汉 430022 | rjzhou@foxmail.com | | 周 豹 | 湖北省地质调查院, 湖北武汉 430034
资源与生态环境地质湖北省重点实验室, 湖北武汉 430022 | 278776817@qq.com | | 文 广 | 中国地质大学(武汉)资源学院, 湖北武汉 430074 | | | 孙 悦 | 湖北国土资源职业学院, 湖北武汉 430090 | | | 吴昌雄 | 湖北省地质局第一地质大队, 湖北大冶 435100 | | | 朱 金 | 湖北省地质调查院, 湖北武汉 430034 | | | 尚世超 | 湖北省地质局第一地质大队, 湖北大冶 435100 | | | 李柏村 | 湖北省地质局第一地质大队, 湖北大冶 435100 | | | 廖 旺 | 资源与生态环境地质湖北省重点实验室, 湖北武汉 430022
湖北省地质科学研究院, 湖北武汉 430034 | | | 宋威方 | 资源与生态环境地质湖北省重点实验室, 湖北武汉 430022；湖北省地质局第六地质大队, 湖北孝感 432000 | | | 刘晓阳 | 湖北省地质调查院, 湖北武汉 430034
资源与生态环境地质湖北省重点实验室, 湖北武汉 430022 | | | 程孝增 | 湖北省地质调查院, 湖北武汉 430034 | |
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| 基金项目:地球深部探测与矿产资源勘查国家科技重大专项(编号: 2024ZD1002203); 湖北省自然科学基金项目(编号: 2025AFB351; 2023AFD213); 地质过程与成矿预测全国重点实验室科技部专项经费(编号: GPMR202427); 湖北省地质局项目(编号: KJ2023-60; KCDZ2024-17) |
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| 中文摘要:位于鄂东地区毛铺—两剑桥东西向断裂带东段的阮家湾钨铜钼矿床是该区最大的钨铜钼矿床, 累计查明WO3金属量2.40万t, 铜金属量1.80万t, 钼金属量2 439 t。本文对与该矿床形成密切相关的阮家湾花岗闪长岩开展了系统的主微量元素地球化学、锆石U-Pb年代学、锆石微量元素地球化学和Hf同位素组成的研究, 以深入讨论岩石的成因和锆石的成矿和找矿指示意义。测得锆石U-Pb年龄为(143.00±0.74) Ma, 此年龄可代表阮家湾花岗闪长岩的侵位年龄, 表明其为鄂东地区晚中生代岩浆作用的产物。阮家湾花岗闪长岩具有相对均一的Hf同位素组成(εHf(t)= –5.4 ~ –2.2), 与区域上铜山口、铜绿山、龙角山等岩株锆石Hf同位素组成相近, 表明它们来源于富集的岩石圈地幔, 在岩浆上侵的过程中混染了少部分的地壳物质。阮家湾花岗闪长岩具有高Sr/Y和(La/Yb)N比值, 其锆石具有低Dy/Yb(<0.3)值和高Eu/Eu(>0.4)值, 表明形成阮家湾岩株的岩浆是相对富水的熔体。这种富水特征也与通过锆石-全岩成分获取的花岗闪长岩中水含量值(6.85%~8.45%)相一致。基于阮家湾花岗闪长岩中锆石微量元素, 计算得到岩浆氧逸度值为ΔFMQ+1.07~ ΔFMQ+2.88, 表明其具有相对氧化的特征。阮家湾花岗闪长岩中锆石Ce4+/Ce3+为93~190, 略低于铜山口花岗闪长岩和铜绿山石英闪长岩, 表明从铜山口铜钼矿床, 到铜绿山铜铁金矿床再到阮家湾钨铜钼矿床, 其成矿岩浆的氧逸度具有一个逐渐降低的趋势。锆石中Hf元素含量与锆石Ti温度成负相关, 反映了在岩浆演化和冷却过程中分离结晶作用的进行。阮家湾花岗闪长岩中锆石Ti温度为660~727 °C, 与区域上铜山口花岗闪长岩和铜绿山石英闪长岩中锆石的结晶温度相近。本文研究表明, 锆石的微量元素组成例如Eu/Eu*、Dy/Yb和Ce??/Ce3?比值能够较好的指示岩浆的分异结晶作用、水含量和岩浆氧逸度特征, 可以作为成矿和找矿的重要指示工具, 通过分析锆石中的微量元素, 可以有效地评估相关侵入体的成矿潜力, 并应用于前期矿产勘查工作。 |
| 中文关键词:鄂东地区 钨铜钼矿床 锆石U-Pb 锆石地球化学 成矿作用 |
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| Metallogenic Significance of Zircon U-Pb Age and Geochemical Characteristics: A Case Study of the Ruanjia-wan W-Cu-Mo Deposit in Edong District |
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| Abstract:The Ruanjiawan W-Cu-Mo deposit, situated in the eastern part of the Maopu–Liangjianqiao East–West fault zone in the Edong district, with a proven reserve of 24 000 t WO3, 18 000 t Cu and 2 439 t Mo, is the largest W-Cu-Mo deposit in this region. The Ruanjiawan W-Cu-Mo deposit shows a close association with the occurrence of granodiorites of the region. This study investigates the whole-rock geochemistry, zircon U-Pb geochronology, zircon trace elements, and Hf isotopic composition of the Ruanjiawan granodiorite to constrain its age and petrogenesis and establish the significance of zircon as an indicator of W-Cu-Mo mineralization in the Edong district. Zircon U-Pb geochronology results show that the emplacement age of the Ruanjiawan granodiorite is (143.00±0.74) Ma, corresponding to the Late Mesozoic magmatism and metallogeny in the Edong district. The Ruanjiawan granodiorite has a relatively uniform Hf isotopic composition (εHf(t) = ?5.4 to ?2.2), similar to the zircon Hf isotopic composition of the Tongshankou granodiorite, Tonglüshan quartz diorite, and Longjiaoshan granodiorite. This indicates that these rocks are mainly derived from an enriched lithospheric mantle with minor crustal contamination during magmatic evolution. Zircons from the Ruanjiawan granodiorite exhibit high Eu/Eu* (>0.4) and low Dy/Yb (<0.3) values, suggesting that the magma was relatively hydrous, which is consistent with the water content values (6.85%–8.45%) obtained from the whole rock and composition. Based on trace element analyses of zircons from the Ruanjiawan granodiorite, the calculated magma oxygen fugacity values range from ΔFMQ+1.07 to ΔFMQ+2.88, indicating relatively oxidized conditions. In addition, the zircon Ce4+/Ce3+ ratios range from 93 to 190, which is slightly lower than those from the Tongshankou granodiorite and Tonglüshan quartz diorite. This suggests a relative decrease in the oxidation state of the metallogenic magma from the Tongshankou Cu-Mo deposit to the Tonglüshan Cu-Fe-Au deposit, and subsequently to the Ruanjiawan W-Cu-Mo deposit. The zircon Hf content of the Ruanjiawan granodiorite is negatively correlated with the Ti-in-zircon temperatures, reflecting fractional crystallization during magma evolution and cooling. Ti-in-zircon temperatures range from 660 °C to 727 °C, similar to the crystallization temperatures of zircon in the regional Tongshankou granodiorite and Tonglüshan quartz diorite. This study demonstrates that the trace element compositions of zircon, such as the Eu/Eu*, Dy/Yb, and Ce4+/Ce3+ ratios, are effective indicators of water content characteristics, oxygen fugacity, and magmatic differentiation. Zircon geochemistry and geochronology thus serve as effective means for identifying granitoids with the potential for skarn mineralization. |
| keywords:Edong district W-Cu-Mo deposit zircon U-Pb zircon geochemistry mineralization |
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