Precise ages of gold mineralization and pre-gold hydrothermal activity in the Baiyun gold deposit, northeastern China: in situ U–Pb dating of hydrothermal xenotime and rutile

被引:0
作者
Haoxuan Feng
Ping Shen
Rixiang Zhu
Jian-Wei Zi
David I. Groves
Changhao Li
Yang Wu
Ge Ma
Taiyang Li
机构
[1] Chinese Academy of Sciences,Key Laboratory of Mineral Resources, Institute of Geology and Geophysics
[2] University of Chinese Academy of Sciences,College of Earth and Planetary Sciences
[3] Chinese Academy of Sciences,State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics
[4] China University of Geosciences,State Key Laboratory of Geological Processes and Mineral Resources
[5] Curtin University,John de Laeter Centre
[6] China University of Geosciences,State Key Laboratory of Geological Processes and Mineral Resources
[7] University of Western Australia,Centre for Exploration Targeting
[8] Liaoning Zhaojin Baiyun Gold Mining Corporation,undefined
来源
Mineralium Deposita | 2022年 / 57卷
关键词
Hydrothermal rutile and xenotime; In situ U–Pb dating; Trace element geochemistry; Gold ore genesis; Baiyun gold deposit; North China Craton;
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学科分类号
摘要
Timing of the major Baiyun gold deposit (~ 70 t Au) in the northeastern North China Craton is controversial. A textural and geochronological study of high-grade gold ores identifies three generations of xenotime (Xtm-1, Xtm-2 and Xtm-3), even in single grains. The oldest Xtm-1, in grain cores, is of metamorphic origin, with very high U and U/Th ratios, and hump-shaped, HREE-enriched patterns with maximum normalized values at Yb and large negative Eu anomalies. It is dated at 1856 ± 6 Ma, consistent with its crystallization during regional metamorphism related to cratonization. In contrast, 244 ± 2 Ma Xtm-2 overgrowths are of hydrothermal origin, having low U and U/Th ratios and hump-shaped, MREE-enriched patterns with maximum normalized values at Ho and negligible Eu anomalies. Xtm-2 records a previously unrecognized Middle Triassic hydrothermal episode. Xtm-3, in equilibrium with native gold-hosting pyrite and rutile, is also hydrothermal. The Xtm-3 domains have similar U, U/Th ratios, and MREE-enriched patterns to Xtm-2, but a younger crystallization age of 231 ± 1 Ma. Associated rutile grains that show close textural associations with auriferous pyrite and native gold have an in situ SIMS U–Pb an intercept age of 229 ± 4 Ma, consistent with that of Xtm-3. Collectively, these reliable ages indicate that gold mineralization at Baiyun occurred at ca. 230 Ma, predating the emplacement of granite intrusions by more than 3 million years. Both the Middle Triassic hydrothermal event (~244 Ma) and the Late Triassic gold mineralization event (~230 Ma) lie within the temporal window of collisional tectonics in the host orogen. In combination, the new geochronology and fluid-inclusion and geological data support Bayun’s classification as an orogenic gold deposit.
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页码:1001 / 1022
页数:21
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