Skip to Main Content
GEOREF RECORD

Zircon compositional evidence for sulfur-degassing from ore-forming arc magmas

John H. Dilles, Adam J. R. Kent, Joseph L. Wooden, Richard M. Tosdal, Alison Koleszar, Robert G. Lee and Lucian P. Farmer
Zircon compositional evidence for sulfur-degassing from ore-forming arc magmas
Economic Geology and the Bulletin of the Society of Economic Geologists (January 2015) 110 (1): 241-251

Abstract

Porphyry Cu (+ or -Mo + or -Au) and epithermal Au-Ag deposits are major sources of mined metals and are commonly formed by magmatic-hydrothermal fluids derived from hydrous magmas in Phanerozoic convergent margin settings. The igneous rock assemblages associated with porphyry mineral deposits are common in modern convergent margin settings, but while many have produced acidic magmatic fluids, very few, past or present, have produced sufficient metal, chlorine, and sulfur enrichments necessary to engender an ore deposit. The reasons for this remain uncertain. We report SHRIMP-RG ion microprobe analyses of hafnium, titanium and rare earth element (REE) abundances in zircon, a nearly ubiquitous and robust trace mineral in crustal magmas. Comparison of the compositions of zircons in ore-forming and barren granitic plutons indicate that ore-forming granites crystallized at relatively low temperature and have relatively small negative europium anomalies (mostly Eu (sub N) /Eu (sub N) * > or =0.4). We interpret these small zircon europium anomalies to indicate oxidizing magmatic conditions and hypothesize that in many cases this reflects oxidation due to SO (sub 2) degassing from magmas with a relatively low Fe/S ratio. Oxidation of europium and iron in the melt is produced by reduction of magmatic sulfate (S (super 6+) ) to SO (sub 2) (S (super 4+) ) upon degassing. This interpretation reinforces the important role of oxidized sulfur-rich fluids in porphyry and epithermal mineral deposit formation. Zircon compositions thus may be used to identify ancient magmas that released significant amounts of SO (sub 2) -rich gases, and regional surveys of zircon composition are potentially a valuable tool for mineral exploration.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 110
Serial Issue: 1
Title: Zircon compositional evidence for sulfur-degassing from ore-forming arc magmas
Affiliation: Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States
Pages: 241-251
Published: 201501
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 91
Accession Number: 2015-007440
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Annotation: A digital suppl. to this paper is avail. at http://economicgeology.org/ and at http://econgeol.geoscienceworld.org/
Illustration Description: illus. incl. 1 table
N15°07'60" - N15°07'60", E120°20'60" - E120°20'60"
N39°00'00" - N39°00'00", W119°10'00" - W119°10'00"
N46°00'00" - N46°00'00", W112°31'00" - W112°31'00"
S26°16'60" - S26°16'60", W69°43'00" - W69°43'00"
Secondary Affiliation: Stanford University, USA, United StatesUniversity of British Columbia, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201504
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal