Snowball quartz in highly fractionated peraluminous granites: An indicator of multiple magma degassing

作者：Daohan Zhang, Kunfeng Qiu, Chang Xu, Yuwei Luan, Yanjun Li, Junhao Wei, Jun Deng · 发表于：American Mineralogist · 年份：2025 · DOI：10.2138/am-2024-9649 · 被引用次数：9 · 研究领域：Geological and Geochemical Analysis、earthquake and tectonic studies、Geomagnetism and Paleomagnetism Studies

Abstract Snowball quartz is commonly found in highly fractionated peraluminous granites that may be associated with mineralization of Ta, Nb, Li, W, Sn, and Rb. The genesis of snowball quartz has been a subject of controversy, and its genetic relationship with potential rare metal mineralization remains poorly understood. This work presents a study of the mineralogy and chemistry of quartz and plagioclase from the Yashan pluton in southern China. The Yashan pluton hosts the Yichun Ta-Nb-Li deposit and is primarily composed of two-mica granite, Li-mica granite, and topaz-lepidolite granite, which were intruded by granite dikes. The texture known as “snowball” is observed in quartz from Li-mica granite, but it is more frequently and prominently developed in quartz from topaz-lepidolite granite and granite dikes. This texture is characterized by the zonal arrangement of prismatic albite (referred to as snowball albite) within quartz phenocrysts, with the {010} face of snowball albite preferentially adhering to the crystal faces of quartz. It typically develops in specific domains of the mantle and/or rim of quartz phenocrysts, and occasionally in their cores. The snowball texture is preferentially developed on the prism faces (m) of quartz, as indicated by a higher abundance of snowball albites on these faces compared to others. The snowball-textured quartz domain (SBTQD) is texturally similar to other domains from the same growth zone and chemically overlaps with magmatic quart...