1. Millennial pulses of ore formation and an extra-high Tibetan Plateau.
- Author
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Yang Li, Allen, Mark B., and Xian-Hua Li
- Subjects
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GOLD ores , *ORES , *OROGENIC belts , *ION analysis , *SKARN , *SLABS (Structural geology) , *MILLENNIALS , *RESERVOIRS - Abstract
Quantifying the rhythms and rates of magmatic-hydrothermal systems is critical for a better understanding of their controls on ore formation and the dynamics of magmatic reservoirs that feed them. We reconstructed the evolution of ore-forming fluids using hydrothermal quartz from the 17.4 Ma Zhibula skarn, Tibet. Ion probe analysis reveals sharp and dramatic changes in quartz δ18O values between 5‰ and -9.3‰, with fluid δ18O values varying between 2.8‰ and -18.2‰, which are best explained by transient meteoric water incursion into a hydrothermal system dominated by magmatic fluids. Two pulses of magmatic fluids and a meteoric water incursion event are inferred, which operated at the millennium scale (760-1510 yr) as constrained by the aluminum diffusion chronometer. Our results indicate that magmatic reservoirs are likely water unsaturated for most of their lifetime (>105 -106 yr), with transient and episodic fluid exsolutions (-10³ yr) being driven by magma replenishment or crystallization-induced water saturation. With focused and efficient metal deposition, multiple pulses of metallifer- ous fluids favor the formation of giant deposits with high grade. Meteoric water δ18O values (-25.4 ± 2.3‰) derived from Zhibula quartz further suggest a paleo-elevation of 5.9 ± 0.3 km; this transient early Miocene surface uplift plausibly was due to break-off of the oceanic slab attached to the Indian Plate. Our research highlights that ubiquitous hydrothermal quartz in orogenic belts can probe the dynamics of magmatic-hydrothermal systems and also quantify paleo-elevations, which has significant tectonic implications. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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