首页|Genesis of the distal axis East Longjing-2 hydrothermal field on the ultraslow-spreading Southwest Indian Ridge: Evidences from fluid inclusions

Genesis of the distal axis East Longjing-2 hydrothermal field on the ultraslow-spreading Southwest Indian Ridge: Evidences from fluid inclusions

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  • NSTL
  • Elsevier
Tectonic-related hydrothermal fields constitute about half of the hydrothermal activities on slow-ultraslow spreading ridges, and may form sulfides large in size and rich in precious metals. Ore-forming fluids are critical for element migration progressions, thus are key parameter to reveal their genesis and sulfide mineralization processes. However, previous studies of this kind of hydrothermal activities primarily focused on vent fluids which have transient effects or based on surface samples, while the ore-forming fluid evolution and related subseafloor mineralization process are still poorly constrained. In this study, we analyzed the characteristics of fluid inclusions in the stockwork mineralization of the East Longjing-2 hydrothermal field (ELHF-2) on the Southwest Indian Ridge. The results showed that the fluids evolved gradually from medium-high temperatures (260-315 degrees C, mean of 284 degrees C) and low salinities (0.70-3.70 wt.% NaCl eq.) in the disseminated pyrite mineralization stage (Stage I) to medium temperatures (239-261 degrees C, mean of 249 degrees C) and low salinities (1.05-3.85 wt.% NaCl eq.) in the chalcopyrite-pyrite-quartz veinlet mineralization stage (Stage II). Laser Raman specular analysis indicated the fluid inclusions were mainly composed of H2O. The low salinity (lowest 0.7 wt.% NaCl eq.) and various vapor volume (0.05-0.5) observed in these fluid inclusions suggested the ore-forming fluids were probably mixtures of the low-salinity vapor phase formed by phase separation with large amounts of seawater. The precipitation of the ore-forming elements was likely induced by temperature decreasing. We propose that hydrothermal circulation in ELHF-2 was a result of coupled high-permeability detachment fault and shallow gabbro intrusion. Our results suggest that high temperature hydrothermal activities could be developed on distal axis area on ultraslow spreading ridges.

EditorShu GaoFluid inclusionPhysical and chemical conditionsThe East Longjing-2 hydrothermal fieldSouthwest Indian RidgeMID-ATLANTIC RIDGEOCEANIC CORE COMPLEXLA-ICP-MSPHASE-SEPARATIONVENT FLUIDSSULFIDE MINERALIZATIONMASSIVE SULFIDESHEAT-FLUXEVOLUTIONSYSTEMS

Yu, Junyu、Chen, Ming、Wang, Nannan、Chen, Kaiying、Tao, Chunhui、Liao, Shili、Ge, Chendong、Li, Wei、Liang, Jin、Yang, Weifang

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Zhejiang Univ

Shanghai Jiao Tong Univ

Nanjing Univ

Minist Nat Resources

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2022

10.1016/j.margeo.2022.106775

Marine Geology

Marine Geology

EISCI
ISSN：0025-3227
年,卷(期)：2022.446
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