Millennial pulses of ore formation and an extra-high Tibetan Plateau

Li, Yang; Allen, Mark B.; Li, Xian-Hua

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 metalliferous 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.

Citation

Li, Y., Allen, M. B., & Li, X.-H. (2022). Millennial pulses of ore formation and an extra-high Tibetan Plateau. Geology, 50(6), 665-669. https://doi.org/10.1130/g49911.1

• Journal Article Type: Article
• Acceptance Date: Jan 3, 2022
• Online Publication Date: Mar 8, 2022
• Publication Date: 2022
• Deposit Date: Jun 27, 2022
• Publicly Available Date: Jun 27, 2022
• Journal: Geology
• Print ISSN: 0091-7613
• Electronic ISSN: 1943-2682
• Publisher: Geological Society of America
• Peer Reviewed: Peer Reviewed
• Volume: 50
• Issue: 6
• Pages: 665-669
• DOI: https://doi.org/10.1130/g49911.1
• Public URL: https://durham-repository.worktribe.com/output/1203075