Details

Autor(en) / Beteiligte

• Zhang, Lu
• Jiang, Shao-Yong
• Romer, Rolf L.
• Zhang, Hao-Xiang
• Wan, Song-Lin

Titel

Characteristics and formation of rare-metal pegmatites and granites in the Duanfengshan-Guanyuan district of the northern Mufushan granite complex in South China

Ist Teil von

• Lithos, 2024-06, Vol.474-475, Article 107579

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2024

Link zum Volltext

Quelle

ScienceDirect

Beschreibungen/Notizen

• The Mufushan area, which has abundant rare-metal pegmatites within and around the Mufushan Granite Complex, has become a major target for Ta-Nb-(Li-Be) exploration in South China. The age and origin of the pegmatites and associated rare-metal mineralization are still under debate. Here, we report the in situ U-Pb ages and geochemical characteristics of granites and pegmatites in the Guanyuan and Duanfengshan districts, which are located in the central and northern parts of the Mufushan Complex. Combined zircon, apatite and monazite U-(Th)-Pb dating revealed that biotite, two-mica, and muscovite granites from the Guanyuan and Duanfengshan districts were emplaced at 143–139 Ma, which overlaps with the U-Pb ages of columbite-group minerals (CGM) from different internal zones of the Duanfengshan pegmatites (142–140 Ma). Whole-rock major and trace element compositions and Sr-Nd-Hf isotope data reveal that the granites and pegmatites experienced continuous evolution from biotite, two-mica, and muscovite granites to pegmatite and that the magma originated from the partial melting of mica schists that are abundant in the Mufushan area. Temporal, chemical and mineralogical evidence indicates a genetic link between muscovite granite and Ta-Nb pegmatites. The textures and chemical compositions of CGM from different pegmatites exhibit features typical of magmatic CGM, indicating that fractional crystallization was the driving force that promoted Ta-Nb enrichment. The increasing alumina saturation index [ASI: molar Al/(Ca–1.67P + Na + K)] of pegmatitic melt due to albite crystallization may have been the main factor controlling CGM deposition, explaining why major Ta-Nb mineralization is bound to albite pegmatites. The Duanfengshan and other rare-metal pegmatites in the Mufushan area are derivatives of the most evolved granitic facies (i.e., muscovite granite) of the Mufushan Complex. The Duanfengshan and Renli pegmatite fields indicate that the Early Cretaceous (∼140 Ma) may have been an important, underappreciated epoch for the formation of pegmatite-related rare-metal resources in the Mufushan area and beyond in South China. [Display omitted] •The rare metal pegmatites have genetic relationship with the muscovite granite in the Mufushan area.•In-situ U-Pb dating of columbite-group minerals indicate the rare metal mineralization occurred at 142–140 Ma.•Prolonged fractional crystallization is the driving force to promote rare metal mineralization in granite-pegmatite system.•Early Cretaceous is an important epoch for the formation of pegmatite rare-metal resources in South China.