Origin of unusual HREE-Mo-rich carbonatites in the Qinling orogen, China

Abstract

Carbonatites, usually occurring within intra-continental rift-related settings, have strong light rare earth element (LREE) enrichment; they rarely contain economic heavy REE (HREE). Here, we report the identification of Late Triassic HREE-Mo-rich carbonatites in the northernmost Qinling orogen. The rocks contain abundant primary HREE minerals and molybdenite. Calcite-hosted fluid inclusions, inferred to represent a magmatic-derived aqueous fluid phase, contain significant concentrations of Mo (~17 ppm), reinforcing the inference that these carbonatitic magmas had high Mo concentrations. By contrast, Late Triassic carbonatites in southernmost Qinling have economic LREE concentrations, but are depleted in HREE and Mo. Both of these carbonatite types have low δ26Mg values (−1.89 to −1.07‰), similar to sedimentary carbonates, suggesting a recycled sediment contribution for REE enrichment in their mantle sources. We propose that the carbonatites in the Qinling orogen were formed, at least in part, by the melting of a subducted carbonate-bearing slab, and that 10 Ma younger carbonatite magmas in the northernmost Qinling metasomatized the thickened eclogitic lower crust to produce high levels of HREE and Mo.

The Petyayan-Vara Carbonatite-Hosted Rare Earth Deposit (Vuoriyarvi, NW Russia): Mineralogy and Geochemistry

“…Therefore, rare earth carbonatites are a major focus of critical metal research. Over the past five years, several dozens of papers have been published on the subject of rare earth carbonatites (RE carbonatites) in Angola [5,6], Australia [7][8][9], Brazil [10,11], Canada [12][13][14][15][16][17], China [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], Finland [38], India [39][40][41][42], Italy [43,44], Malawi [45][46][47][48][49][50][51], Mongolia [52,53], Namibia…”

The origin of secondary heavy rare earth element enrichment in carbonatites: Constraints from the evolution of the Huanglongpu district, China

“…The overall HREE enrichment of the Huanglongpu carbonatites has been previously related to a recycled ocean crust component in the lithospheric mantle indicated by Nd-Sr radioisotope studies and Mg stable isotope analyses of calcite (Table 8; Xu et al, 2010Xu et al, , 2011Song et al, 2016), accounting for the district scale enrichment in Mo, accompanied by small degrees of melting from a garnet-poor source (Xu et al, 2007). This primary source control has been proposed to be enhanced by fractional crystallisation of calcite, with the dykes at the current level of exposure representing relatively HREE-enriched carbonate left as residuum on the walls of flowing carbonatite dykes from an initially more LREE-enriched melt (Xu et al, 2007).…”

“…Chondrite values from Sun and McDonough (1989) here and throughout. associated porphyry and porphyry-skarn Mo deposits in the Qinling belt formed in the Late Jurassic-Early Cretaceous, as indicated by molybdenite Re-Os dates ranging from 148 to 112 Ma (Huang et al, 1994;Mao et al, 2008), whereas molybdenite from the Huanglongpu deposits is much older, yielding Re-Os ages from 209 to 221 Ma and monazite U-Pb and Th-Pb ages from 208.9 ± 4.6 Ma and 213.6 ± 4.0 Ma (Huang et al, 1994;Song et al, 2016;Stein et al, 1997). Alkali granites and syenites have been identified in the area, but these are peraluminous, inferred to be derived from similar sources to the Mo-bearing granitoids (typically granodiorite) and have zircon U-Pb ages of 131 ± 1 Ma (Zhao et al, 2010), and are therefore unrelated to the carbonatites and REE-mineralisation.…”

“…Carbonate is also a potentially less LREE selective ligand at hydrothermal temperatures (Haas et al, 1995). Fluid inclusion data from quartz cores to the carbonatite dykes (Cangelosi, 2016;Song et al, 2016) indicate hydrothermal fluids in the Huanglongpu district were saturated with respect to sulphate minerals, and arcanite (K 2 SO 4 ), anhydrite (CaSO 4 ), glauberite (Na 2 Ca(SO 4 ) 2 ), and gorgeyite (K 2 Ca 5 (SO 4 ) 6 ·H 2 O) have all been identified as either daughter or heterogeneously trapped phases in fluid inclusions (Cangelosi, 2016 …”

Geochronology and fluid source constraints of the Songligou gold‐telluride deposit, western Henan Province, China: Analysis of genetic implications

“…The southern margin of the NCC has experienced multiple subduction events. The Proterozoic-Paleozoic subduction of the Shangdan oceanic crust Dong et al, 2011;Yang et al, 2003) and Mesozoic subduction of the Izanagi plate Liu, Gurnis, Ma, & Zhang, 2017) beneath the NCC could both contribute to the metasomatism of the NCC (Xu, Zheng, & Zhao, 2011b;Yang, Teng, Zhang, & Li, 2012;Li, 2015;Song et al, 2016). The presence of a metasomatized lithospheric mantle beneath the southern margin of the NCC has also been supported by the emplacement of many intrusions, including the 245-210 Ma Mogou alkali pluton Lu, Liang, Bai, & Lu, 2013;He et al, 2016), the 225-209 Ma Huangshuian and Huanglongpu carbonatites (Stein et al, 1997;Huang, Wu, Du, & He, 1994;Huang, Hou, Yang, Li, & Xu, 2009;Du et al, 2004;Xu et al, 2011a;Cao et al, 2014;Song et al, 2015Song et al, , 2016, the ca.160 Ma Xinyang peridotitic xenolithos (Zheng, Sun, Zhou, & Robinson, 2005, Zheng et al, 2008; enriched by South China), the 129 Ma Huanglongpu diabase dikes (Zhao, Mao, Ye, Xie, & Yang, 2010), and the 122 Ma Tianqiaogou monzodiorites (Gao, Zhao, Bao, & Yang, 2014).…”