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Zircon petrochronological evidence for a plutonic-volcanic connection in porphyry copper deposits

Yannick Buret, Joern-Frederik Wotzlaw, Stan Roozen, Marcel Guillong, Albrecht von Quadt and Christoph A. Heinrich
Zircon petrochronological evidence for a plutonic-volcanic connection in porphyry copper deposits
Geology (Boulder) (May 2017) 45 (7): 623-626


Bridging the gap between the plutonic and volcanic realms is essential for understanding a variety of magmatic processes from caldera-forming eruptions to the formation of magmatic-hydrothermal ore deposits. Porphyry copper deposits are commonly associated with large and long-lived volcanic centers, but the temporal and dynamic link between mineralized intrusions and volcanic eruptions has remained controversial. Based on the combination of (1) high-precision zircon U-Pb geochronology and trace element geochemistry with (2) plagioclase textures, we discovered an intimate connection between an ignimbrite eruption and a nearby world-class porphyry deposit (Bajo de la Alumbrera in the late Miocene Farallon Negro Volcanic Complex of Argentina). Our results indicate that the magmatic-hydrothermal deposit and explosive volcanism were derived from a common magma reservoir that evolved over a minimum duration of 217 + or - 25 k.y. before the final eruption. We show that the volcanic pile represents the inverted magma reservoir, recording systematic differences in plagioclase textures and juvenile clast content from bottom to top. This tight temporal and geochemical link suggests that deposit formation and volcanic eruption were both triggered by the same injection of a volatile-saturated primitive magma into the base of the magma chamber. A time gap of 19 + or - 12 k.y. between porphyry mineralization and the onset of explosive volcanism indicates a minimum duration of magma reservoir rejuvenation that led to the explosive eruptive event. Catastrophic loss of volatiles by explosive volcanism terminated the ore-forming capacity of the upper-crustal magma chamber, as evidenced by the intrusion of a syn-eruptive barren quartz-feldspar porphyry. Our results demonstrate that porphyry copper deposits provide critical information to understand how volatiles control the fate of hydrous magmas between pluton formation and explosive volcanism.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 45
Serial Issue: 7
Title: Zircon petrochronological evidence for a plutonic-volcanic connection in porphyry copper deposits
Affiliation: Eidgenoessische Technische Hochschule Zuerich, Department of Earth Sciences, Zurich, Switzerland
Pages: 623-626
Published: 20170501
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2017-042146
Categories: Economic geology, geology of ore depositsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017203
Illustration Description: illus. incl. geol. sketch map
S26°08'60" - S26°08'60", W67°24'00" - W67°24'00"
Secondary Affiliation: University of Zurich, CHE, Switzerland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201723
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