近日，中国地质调查局Liao, Jia团队研究了华南地块九嶷山地区含铁硅铁岩微颗粒包裹体显示的花岗质岩浆演化。相关论文于2025年12月18日发表在《地球化学学报》杂志上。

花岗岩中含铁橄榄石-铁辉石的包体是一种特殊现象，其形成机制尚不明确。

研究组在华南地块九嶷山地区的花岗岩中发现一组含铁橄榄石-铁辉石的细粒包体。寄主岩中矿物颗粒（如石英-长石-黑云母）呈现明显的碎裂结构，而细粒包体内则发育多种矿物反应结构（如铁辉石交代铁橄榄石）。寄主岩具有高SiO?含量（68.40–70.59 wt%）和低Mg#值（15–19），显示分馏的球粒陨石标准化稀土元素配分模式，具负Eu异常、Nb-Ta亏损、显著正Pb异常及负Sr异常。铁橄榄石（Fa_87.5–92.7，Fe₂SiO₄比值）与铁辉石（Fs_74.6–79.9，Fe₂Si₂O₆比值）颗粒的主量元素组成变化范围狭窄，其稀土元素配分模式均呈现重稀土富集特征。

所有矿物结晶条件的估算结果均表明相关岩浆经历了正常的演化趋势。此外，两类细粒包体与其寄主岩中常见矿物（如黑云母和铁钛氧化物）的结晶条件未显示明显差异。基于前人研究，研究组认为这些细粒包体很可能是花岗质岩浆快速上升侵位过程中，早期结晶矿物堆积并伴随与寄主岩浆反应的产物。与全球其他含铁镁质矿物花岗岩对比表明，该研究中的铁镁质矿物与其寄主岩尚未达到平衡状态，这可能为含铁镁质矿物花岗岩的成因提供了新的例证。

附：英文原文

Title: Tracing the evolution of granitic magmas revealed by fayalite–ferrosilite-bearing microgranular enclaves in Jiuyishan area of South China Block

Author: Liu, Jing-Yi, Ou, Quan, Lai, Jian-Qing, Zi, Feng, Wang, Kun, Xiao, Wen-Zhou, Lin, Zhi-Cheng, Wang, Cui-Yun, Feng, Qian-Cheng, Liao, Jia

Issue&Volume: 2025-12-18

Abstract: Fayalite–ferrosilite-bearing enclaves in granite are a special phenomenon, and their formation mechanism is unclear. Here, a set of fayalite–ferrosilite-bearing microgranular enclaves occurred in granites from the Jiuyishan area, South China Block. The mineral grains (e.g., quartz–feldspar–biotite) show obvious cataclastic textures in host, while there are various mineral reaction textures (e.g., fayalite replaced by ferrosilite) in microgranular enclaves. The host rocks have high SiO2 (68.40–70.59 wt%) contents and low Mg# (15–19). They exhibit fractionated chondrite-normalized rare-earth element (REE) patterns with negative Eu anomalies, Nb–Ta depletion, strongly positive Pb, and negative Sr anomalies. Both fayalite [Fa87.5–92.7, (Fe2SiO4) ratios] and ferrosilite [Fs74.6–79.9; (Fe2Si2O6) ratios] grains show narrow variations in major elemental compositions, and their REE patterns are characteristic of heavy REE enrichment. All the estimated results of mineral crystallization conditions indicate that the related magma experienced a normal evolutionary trend. Moreover, there is no obvious difference in the crystallization conditions of the common minerals (e.g., biotites and Fe–Ti oxides) in the two microgranular enclaves and their host. Based on a previous study, we suggest that the studied microgranular enclaves were most likely generated by the accumulation of early crystallized minerals accompanied by their reactions with host magma during the rapid ascent and emplacement of granitic magmas. Comparison with other ferromagnesian mineral-bearing granites worldwide, the equilibrium state has not yet been reached between the studied ferromagnesian mineral and its host. This could be a new case for the genesis of ferromagnesian mineral-bearing granites.

DOI: 10.1007/s11631-025-00838-y

Source: https://link.springer.com/article/10.1007/s11631-025-00838-y