Changing Brine Inputs Into Hydrothermal Fluids: Southern Cleft Segment, Juan de Fuca Ridge
| Autor: | William W. Chadwick, David W. Caress, Jennifer B. Paduan, Robert A. Zierenberg, D. A. Clague, C. Geoffrey Wheat |
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| Rok vydání: | 2020 |
| Předmět: |
Geochemistry & Geophysics
Dike rock reaction 010504 meteorology & atmospheric sciences 010502 geochemistry & geophysics 01 natural sciences Juan de Fuca Hydrothermal circulation Brining Geochemistry and Petrology Fluid inclusions Chimney Petrology mid‐ 0105 earth and related environmental sciences geography geography.geographical_feature_category Mid-ocean ridge Cleft Segment Hydrothermal brine Geophysics water‐ Magma Physical Sciences Ridge (meteorology) Earth Sciences ocean ridge Geology |
| Zdroj: | Geochemistry Geophysics Geosystems, vol 21, iss 11 Geochemistry, Geophysics, Geosystems, vol 21, iss 11 |
| Popis: | Author(s): Wheat, CG; Zierenberg, RA; Paduan, JB; Caress, DW; Clague, DA; Chadwick, WW | Abstract: In 2016, temperature recorders were recovered, temperatures were measured, and fluid samples were collected from Vent 1, a high temperature (338°C) hydrothermal discharge site on the southern Cleft Segment of the Juan de Fuca Ridge. Coupled with previous sampling efforts, this collection represents a 32-year record of discharge from a single chimney structure, the longest record to date. Remarkably, the fluid has remained brine-dominated for more than three decades. This brine formed during phase separation and segregation prior to initial observations in 1984. Although the chloride concentration of the discharging fluid has decreased with time, the fluid temperature has remained nearly constant for at least 3.3nyears and probably for 15 or even 22nyears. Compositions of the discharging fluids are consistent with inputs from a deep-sourced brine, which was last equilibrated at g400°C at a depth consistent with the base of the sheeted dikes and the brittle-ductile transition. This brine mixed (diffusion or dispersion) with a likely non-phase-separated, hydrothermal fluid prior to discharge. A survey of hydrothermal endmember fluids with chlorinities in excess of 700nmmol/kg shows, with the exception of Fe, a single trend between major ion concentrations and chlorinity even though data are from a range of crustal compositions, spreading rates, and water and magma depths. Calculated deep-sourced brines from hydrothermal fluid data are similar to data based on fluid inclusions and estimates of brine assimilation in magmas. A better understanding of brines is required given their potential duration of discharge and capacity for mobilizing metals. |
| Databáze: | OpenAIRE |
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