Decoupled geochemical behavior of As and Cu in hydrothermal systems
Journal
Geology
Journal Volume
37
Journal Issue
8
Start Page
707
End Page
710
ISSN
0091-7613
1943-2682
Date Issued
2009-07-30
Author(s)
Abstract
Cu-rich and As-rich growth zones in pyrite provide new insights into the composition of late-stage magmatic fluids and their host hydrothermal ore deposits. The pyrite is from the Pueblo Viejo (Dominican Republic) and Yanacocha (Peru) high-sulfidation gold-silver deposits, which are thought to form from hydrothermal systems that interacted with magmatic vapor plumes. Electron microprobe analysis, secondary ion mass spectrometry, and elemental maps show that pyrite, the most common sulfide mineral in both deposits, contains three different types of growth zones: (1) As-rich zones that are enriched in Au, Ag, Sb, Te, and Pb, (2) Cu-rich zones with significantly lower concentrations of these elements, and (3) barren pyrite zones with no other elements. These zones are interpreted to result from mixing between the pyrite-forming fluid and vapors that invaded the main hydrothermal system episodically. Comparison to experimental studies of elemental partitioning and analyses of fumaroles and fluid inclusions from magmatic-hydrothermal systems suggests that the As-rich vapor formed at high and possibly magmatic temperatures, whereas the Cu-rich vapor formed at lower temperatures, possibly during migration of the original magmatic vapor. The presence of finely spaced multiple growth zones in pyrite suggests that the composition of at least high-sulfidation hydrothermal systems can be affected intermittently and repetitively by vapors, probably from underlying magmas.
Subjects
Atlantic islands
Atlantic Ocean
Caribbean Islands
Dominican Republic
Greater Antilles
Peru
South America
Analytical geochemistry
Deposits
Electron probe microanalysis
Gold
Lead
Lead deposits
Mineralogy
Mining
Ore deposit geology
Pyrites
Secondary ion mass spectrometry
Silver deposits
Sulfide minerals
Tellurium compounds
Vapors
Electron microprobe analysis
Elemental maps
Experimental studies
Fluid inclusion
Geochemical behaviors
Gold-silver deposits
Hydrothermal ore deposit
Hydrothermal system
Magmatic fluids
Magmatic temperatures
Magmatic-hydrothermal systems
Sulfidation
Vapor plumes
arsenic
copper
experimental study
fluid composition
fluid inclusion
hydrogeochemistry
hydrothermal system
magma
mixing
ore deposit
partitioning
pyrite
sulfide group
Gold deposits
Publisher
Geological Society of America
Type
journal article