| L6型普通球粒陨石茂名的岩石学、地球化学和年代学研究 |
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| 引用本文：月程,车晓超,龙涛,王子尧,王慧敏,王晨,刘敦一.2026.L6型普通球粒陨石茂名的岩石学、地球化学和年代学研究[J].地球学报,47(3):555-564. |
| DOI：10.3975/cagsb.2026.032421 |
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| 基金项目:本文由国家重点研发计划(编号: 2022YFF0704905)、上海科技馆陨石微结构与化学研究科研创新平台开放课题、国家自然科学基金(编号: 42241107)和天问三号任务关键技术攻关项目(编号: TW3004)联合资助。 |
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| 中文摘要:茂名(Maoming)陨石为2025年的目击L6型普通球粒陨石, 保存状态新鲜、风化极弱(W0)且冲击变质程度较低(C-S2)。本研究结合岩相学与矿物学观测、全岩主微量元素分析及磷酸盐原位SHRIMP U-Pb定年等方法, 对其岩石学特征、地球化学组成与年代学记录进行了系统研究。结果显示, 样品球粒边界模糊、硅酸盐高度重结晶, 矿物组合、结构和全岩主微量元素组成与已报道的L6型普通球粒陨石一致, 稀土元素呈平坦配分且无显著Eu异常。氯磷灰石207Pb/206Pb加权平均年龄为(4 480±12) Ma, 年轻于弱冲击的L6型样品, 其U-Pb同位素体系未受到~470 Ma奥陶纪L型母体小行星裂解事件的改造。上述结果表明, 茂名陨石可能来源于L型母体小行星中-深部区域, 未发生显著熔融分异, 经历充分热变质并缓慢冷却, 可作为约束L6型普通球粒陨石母体晚期冷却历史的重要端元样品。 |
| 中文关键词:L6型普通球粒陨石 茂名陨石 年代学 地球化学 |
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| Petrology, Geochemistry, and Geochronology of the L6 Ordinary Chondrite Maoming Meteorite |
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| Abstract:The Maoming meteorite, an L6 ordinary chondrite from a witnessed fall in 2025, is characterized by fresh preservation, negligible terrestrial weathering (W0), and a low degree of shock metamorphism (C-S2). In this study, the petrography, geochemistry, and phosphate U-Pb chronology of the Maoming meteorite were systematically investigated using scanning electron microscopy, bulk major- and trace-element analyses, and in-situ SHRIMP U-Pb dating. The sample exhibited indistinct chondrule boundaries and extensive silicate recrystallization. Its mineral assemblages, petrographic textures, and major- and trace-element compositions were comparable to those of previously reported L6 ordinary chondrites. The rare earth element pattern was nearly flat, with no significant Eu anomaly. Chlorapatite yields a weighted mean 207Pb/206Pb age of (4 480±12) Ma, which was younger than previously reported ages for weakly shocked L6 ordinary chondrites. Moreover, its U-Pb isotopic system showed no evidence of reset related to the ~470 Ma breakup of the L-chondrite parent body. These results indicate that the Maoming meteorite was derived from the middle to deep interior of the L-chondrite parent body, where it underwent extensive thermal metamorphism followed by slow cooling, without significant melt differentiation. Therefore, it provides a critical end-member constraint on the late-stage cooling history of L6 ordinary chondrites. |
| keywords:L6-chondrite Maoming geochronology geochemistry |
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