Geochronology, petrology, and lithium isotope geochemistry of the Bailongshan granite-pegmatite system, northern Tibet: Implications for the ore-forming potential of pegmatites

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Publikace nespadá pod Ekonomicko-správní fakultu, ale pod Přírodovědeckou fakultu. Oficiální stránka publikace je na webu muni.cz.
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ZHOU Jin-Sheng WANG Qiang XU Yi-Gang CEMPÍREK Jan WANG He MA Jin-Long WEI Gang-Jian HUANG Tong-Yu ZHU Guan-Hong ZHANG Le

Rok publikování 2021
Druh Článek v odborném periodiku
Časopis / Zdroj Chemical Geology
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
www https://www.sciencedirect.com/science/article/pii/S0009254121004277
Doi http://dx.doi.org/10.1016/j.chemgeo.2021.120484
Klíčová slova Lithium pegmatite; Li isotopes; Diffusion; Fractional crystallization; Isotope fractionation
Popis Identification of possible factors that affect Li-mineralizing potential is important to the understanding of the genesis of Li pegmatites. This study provides a comprehensive characterization of the recently discovered Bailongshan Li pegmatite district based on geochronological, petrological, mineralogical, thermal modeling, and Li isotopic data. Columbite-(Fe) U–Pb dating of two pegmatite dikes indicates they were emplaced at 212.3 ± 0.9 and 213.9 ± 0.7 Ma. The spodumene-absent pegmatite dikes yield substantially higher ?7Li values (+2.0‰ to +4.9‰) than spodumene-bearing dikes (-1.9‰ to +0.8‰). Modeling of Li isotopic fractionation during fractional crystallization, fluid exsolution, and diffusion after pegmatite emplacement indicates that the lighter Li isotopic compositions of spodumene-bearing pegmatites are attributable to fluid exsolution or diffusion-driven fractionation of short duration, whereas the heavier isotopic compositions of spodumene-absent pegmatites can be attributed to longer-duration, diffusion-driven fractionation. Together with the results of thermal modeling, we suggest that the cooling rate of pegmatite dikes was an important factor controlling the Li isotopic compositions of pegmatites and slower cooling caused heavier Li isotopic compositions. It may have important implications for the ore-forming potential of Li in pegmatites that high cooling rate is beneficial for forming Li pegmatites.
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