U-Pb Ages, O Isotope Compositions, Raman Spectrum, and Geochemistry of Cassiterites from the Xi’ao Copper-Tin Polymetallic Deposit in Gejiu District, Yunnan Province

Abstract

: The Xi’ao Cu-Sn polymetallic deposit is located in the inner alteration zone of the Laoka granite. The ore bodies extend to 400 m in the granite rock and primarily occur with fluorite and potassic alterations. Two cassiterite samples of altered rock-type ore and one tourmaline vein-type ore in the Xi’ao Cu-Sn polymetallic deposit yielded U-Pb ages of 83.3 ± 2.1 Ma, 84.9 ± 1.7 Ma, and 84.0 ± 5.6 Ma, respectively. The Raman spectrum peak values of A1g were shifted to a lower frequency, possibly due to the substitution of Sn with Nb, Ta, Fe, and Mn. Measured δ18O values of cassiterite samples and calculated δ18OH2O values for the ore-forming fluid indicate that the latter was mostly derived from magma. The high Fe and Mn abundances for cassiterite are consistent with those of hydrothermal origin. The Nb, Ta, and Ti contents indicate that cassiterites in the Xi’ao deposit likely formed in a metallogenic environment that was largely affected by granitic magmatism. Therefore, we conclude that the Xi’ao deposit is a magmatic hydrothermal deposit.

Trace element composition and U-Pb ages of cassiterite from the Bolivian tin belt

“…(2011), Hulsbosch and Muchez (2019), Kendall-Langley et al (2019. Xenothermal and epithermal environment: Murciego et al (1997), Pavlova et al (2015), Guo et al (2018), Cheng et al (2019), Zhao et al (2019).…”

“…Cheng et al (2019) attribute these variations to processes involving element fractionation during mineral growth due to fluid disequilibrium. However, variations in the concentration of Nb and Ta may also be related to the physical-chemical characteristics of the hydrothermal fluids (Zhao et al 2019;Lerouge et al 2017). Zhang et al (2017) noted that cassiterite from high-temperature systems related to highly fractionated Li-F granites and pegmatites has high Nb, Ta and Zr contents (with low Zr/Hf ratios) but low Fe and Mn contents, contrary to cassiterite from low-temperature hydrothermal deposits.…”

“…The broad range of P-T-X conditions in which cassiterite forms, its strong physical and chemical resistance and its plethora of chemical constituents including both compatible and incompatible elements makes this mineral useful as a petrogenetic indicator (Murciego et al 1977;Plimer et al 1991;Serranti et al 2002;Jiang et al 2004;. Furthermore, the moderate U 4+ and low Pb 2+ contents and high Pb isotope closure temperature (up to 860ºC; Zhang et al 2011) in cassiterite makes it suitable for U-Pb dating (e.g., Zhang et al 2017Zhang et al , 2019Guo et al 2018;Neymark et al 2018;Chen et al 2019;Cheng et al 2019;Kendall-Langley et al 2019;Moscati and Neymark 2019;Zhao et al 2019;Legros et al 2020;Lehmann et al 2020;Mao et al 2020). tectonic transition between the Eastern Cordillera and the nearly undeformed Amazonian Lowlands to the northeast and east.…”

LA–ICP–MS U–Pb Dating, Elemental Mapping and In Situ Trace Element Analyses of Cassiterites from the Gejiu Tin Polymetallic Deposit, SW China: Constraints on the Timing of Mineralization and Precipitation Environment

“…Cassiterite (SnO 2 ) is the most important ore mineral for tin deposits and has a tetragonal lattice structure similar to that of the rutile group (M 4+ O 2 ) [1][2][3][4]. Because cassiterite is resistant to chemical and physical alteration and weathering, trace elements, such as Fe, Ti, W, Zr, Hf, Ta, Nb, Mn, Sc, V, and Sb in cassiterite could be used to study mineralization processes and precipitation environments of tin mineralization [2][3][4][5][6][7][8][9][10]. Furthermore, the presence of U and Pb makes it possible to date cassiterite with U-Pb geochronology [1,2,4,[7][8][9][11][12][13][14][15].…”

“…The world-class Gejiu tin polymetallic deposit in SW China has large metal reserves with an endowment estimated at ~10 million metric tonnes of tin, copper, lead, and zinc, containing approximately 300 Mt of tin and copper ore averaging 1 wt% Sn and 2 wt% Cu, respectively, and 400 Mt of lead-zinc ore with 7 wt% Pb + Zn [3,18,19]. Many attempts at dating mineralization timing have been conducted on hydrothermal minerals, including K-Ar/ 40 Ar- 39 Ar dating on quartz/cassiterite [20], Pb-Pb dating on sulfide [20], Re-Os dating of molybdenite [21], and U-Pb dating of cassiterite [3,8,10,22]. However, there is still a lack of systematic cassiterite U-Pb dating of different ore styles.…”