| 川西宝兴灵关晚二叠世玄武岩成因机制——对松潘—甘孜地块起源的约束 |
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| 引用本文：李宏博,周向科,韩鎏,李常权.2026.川西宝兴灵关晚二叠世玄武岩成因机制——对松潘—甘孜地块起源的约束[J].地球学报,47(5):987-1004. |
| DOI：10.3975/cagsb.2026.061221 |
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| 基金项目:本文由自然资源部科技创新发展项目(编号: 102121191130000009001)、自然资源部部门预算项目(编号: 12111300000018001-02)和国家自然科学基金项目(编号: 41772057; 42572028)联合资助。 |
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| 中文摘要:本文针对川西宝兴灵关地区晚二叠世玄武岩开展了矿物学、岩石学、地球化学和同位素特征研究, 结果表明灵关玄武岩属于高钛碱性玄武岩系列, 基于机器学习的单斜辉石温压计得出的结晶温度为1 056~ 1 078 ℃, 压力为1.24~2.53 kbar。稀土和微量元素配分模式与洋岛玄武岩(OIB)一致, 87Sr/86Sr(i)=0.705 34~ 0.705 93, εNd(t)=2.09~3.42。灵关玄武岩的原始岩浆是峨眉山地幔柱在石榴子石稳定区(78~85 km)经过较低程度部分熔融(9%~10%)产生的, 随后遭受了轻微地壳混染(1%~2%), 以及橄榄石、辉石、长石及Fe-Ti氧化物的分离结晶作用。地球化学和同位素特征表明, 灵关晚二叠世玄武岩与峨眉山大火成岩省外带高钛玄武岩、松潘—甘孜地块大石包组高钛玄武岩具有亲缘性, 形成于板内-裂谷构造环境, 是峨眉山地幔柱岩浆作用的产物。ca. 260 Ma, 峨眉山地幔柱上涌引发了扬子克拉通西北缘—松潘—甘孜地块东南缘岩石圈伸展减薄、大规模火山作用和裂谷作用, 从而导致松潘—甘孜地块和扬子克拉通裂解分离。后期的构造运动将扬子克拉通西北缘的部分晚二叠世溢流玄武岩推覆至灵关地区。 |
| 中文关键词:地球化学 峨眉山大火成岩省 地幔柱 松潘—甘孜地块 灵关地区 |
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| Petrogenesis of the Late Permian Basalts in Lingguan Area, Baoxing, Western Sichuan: Implications for the Origin of the Songpan–Ganzi Terrane |
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| Abstract:In this study, we report the mineralogical, geochemical, and Sr-Nd isotopic data of Late Permian basalts in Lingguan, Baoxing, western Sichuan Province. These basalts belong to the high-Ti alkaline basalt series. Based on the machine learning clinopyroxene thermobarometer, we estimated the crystallization temperatures and pressures to be 1 056–1 078 °C and 1.24–2.53 kbar, respectively. The chondrite-normalized rare earth element patterns and primitive mantle-normalized spidergrams showed that the Lingguan basalts have affinities with oceanic island basalt. The rocks have age-corrected 87Sr/86Sr(i) ratios of 0.705 34 to 0.705 93 and positive εNd(t) values of 2.09 to 3.42. The primary magmas of the Lingguan basalts were generated by low-degree partial melting (9%–10%) of the Emeishan mantle plume within the garnet stability field (78–85 km). Subsequently, the magma underwent slight crustal contamination (1%–2%) and fractional crystallization of olivine, pyroxene, feldspar, and Fe-Ti oxides. The geochemical and isotopic characteristics of the Late Permian Lingguan basalts indicate that they are petrogenetically related to high-Ti basalts in the Outer Zone of the Emeishan Large Igneous Province and to high-Ti basalts of the Dashibao Formation in the Songpan-Ganzi Terrane (SGT). All these basalts were formed in an intraplate-rift tectonic setting and are products of magmatism associated with the Emeishan mantle plume. At approximately 260 Ma, the upwelling of the Emeishan mantle plume triggered lithospheric extension and thinning, large-scale volcanism, and rifting along the northwestern margin of the Yangtze Craton and the southeastern margin of the SGT, leading to the following separation of the SGT from the Yangtze Craton. During the subsequent tectonic movements, some flood basalts at the northwestern margin of the Yangtze Craton overthrusted into the Lingguan area. |
| keywords:geochemistry Emeishan Large Igneous Province mantle plume Songpan–Ganzi Terrane Lingguan area |
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