Boron, carbon, oxygen and radiogenic isotope investigation of carbonatite from the Miaoya complex, central China: Evidences for late-stage REE hydrothermal event and mantle source heterogeneity

Hydrothermal upgrading as an important tool for the REE mineralization in the Miaoya carbonatite-syenite complex, Central China

“…Moreover, a summary of previous C-O isotopic results from the altered rocks/ores in the Miaoya complex shows that these data plot the field in between the primary carbonatites and the Au-Ag deposits (Fig. 12) (Xu et al, 2014;Cimen et al, 2018;Su et al, 2019;Zhang et al, 2019b). Such an isotopic feature strongly indicates that the causative fluids are likely coeval and co-genetic with those of the This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.…”

“…2. (Xu et al, 2014;Cimen et al, 2018;Zhang et al, 2019b;Su et al, 2019). The data for the orogenic Au-Ag deposits in South Qinling unit are cited from Pang et al (2001), Zhang et al (2010), and Yue et al (2019), whereas the field of primary, mantle-derived carbonates is cited from Taylor et al (1967).…”

“…The REE mineralization was confirmed to be hydrothermal origin and is spatially restricted to the complex, but direct U-Pb dating of REE minerals obtained much younger ages of 230-210 Ma (Xu et al, 2014;Ying et al, 2017;Zhang et al, 2019a). As such, few studies have suggested that the younger REE minerals could have formed from secondary remobilization of early REE mineralization (Ying et al, 2017(Ying et al, , 2020Zhang et al, 2019aZhang et al, , 2019b or precipitated from external REE-rich fluids that overprinted the complex (Cimen et al, 2018). However, the reliability of these interpretations cannot be evaluated, as most of the data were obtained by analyses of bulk ore/rocks or minerals separates containing multiple generations of components (Ying et al, 2017(Ying et al, , 2020Cimen et al, 2018;Zhang et al, 2019aZhang et al, , 2019b.…”

Boron isotope compositions establish the origin of marble from metamorphic complexes: Québec, New York, and Sri Lanka

“…Boron-related investigations of geological samples are advantageous for many reasons, including its use as a paleo-pH proxy in marine carbonates (e.g., Deegan et al 2016;Rasbury and Hemming 2017;Rae 2018), isotopic sensitivity, especially in fluid-mediated processes (e.g., Spivack and Edmond 1987;Lemarchand et al 2000Lemarchand et al , 2002Gaillardet and Lemarchand 2018;De Hoog and Savov 2018), and limited isotopic fractionation during high-temperature metamorphism and/or hydrothermal activity associated with mantle-derived carbonates (e.g., Çimen et al 2018, 2019Kuebler et al 2020). Boron is a widespread trace element in natural carbonates (~1 to 100 ppm; Kowalski and Wunder 2018 and references therein); its incorporation depends on the conditions of the precipitating fluid (e.g., pH, temperature), the presence of other elements (e.g., Mg, Sr), and the type of carbonate present (biogenic or inorganic; Hemming and Hanson 1992;Hemming et al 1995;Sanyal et al 2000;Penman et al 2013;Rasbury and Hemming 2017;Sutton et al 2018).…”

“…In recent studies, boron has proven to be a powerful diagnostic tool even in complicated geologic settings. For instance, it has been possible to elucidate the mantle source region(s) of the Miaoya and Bayan Obo carbonatite complexes in China despite extensive hydrothermal activity or high-grade metamorphism or both (Çimen et al 2018, 2019Kuebler et al 2020). Furthermore, combining boron isotope values with C, O and Sr isotope compositions has established an effective means for identifying pristine (unaltered) mantle-derived carbonate samples that can then be used to decipher the chemical nature of their upper mantle source regions (Hulett et al 2016;Çimen et al 2018, 2019Kuebler et al 2020).…”