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

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Title: Tracing the evolution of granitic magmas revealed by fayalite–ferrosilite-bearing microgranular enclaves in Jiuyishan area of South China Block.
Authors: Liu, Jing-Yi1,2 (AUTHOR), Ou, Quan1,2,3 (AUTHOR) ouquanCSU@126.com, Lai, Jian-Qing3 (AUTHOR), Zi, Feng4 (AUTHOR), Wang, Kun5 (AUTHOR), Xiao, Wen-Zhou6 (AUTHOR), Lin, Zhi-Cheng1 (AUTHOR), Wang, Cui-Yun1 (AUTHOR), Feng, Qian-Cheng1 (AUTHOR), Liao, Jia1 (AUTHOR) liaojia2143@163.com
Source: Acta Geochimica. Jun2026, Vol. 45 Issue 3, p751-766. 16p.
Subjects: Pyroxene, Magmas, Silicate minerals, Crystallization, Rare earth metals
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. [ABSTRACT FROM AUTHOR]
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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. [ABSTRACT FROM AUTHOR]
ISSN:20960956
DOI:10.1007/s11631-025-00838-y