From a long-lived upper-crustal magma chamber to rapid porphyry copper emplacement: Reading the geochemistry of zircon crystals at Bajo de la Alumbrera (NW Argentina)

Buret, Yannick; Quadt, Albrecht von; Heinrich, Christoph A.; Selby, David; Wälle, Marküs; Peytcheva, Irena

doi:10.1016/j.epsl.2016.06.017

Cited by 144 publications

(95 citation statements)

References 68 publications

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“…The common occurrence of such pulses can be seen in the ubiquitous occurrence of multiple stages of quartz veins in porphyry deposits (Sillitoe, 2010) that are related to rapid overpressure-permeability waves (Weis et al, 2012). Such episodic events are very short (years) relative to the lifetimes of porphyry systems associated with individual intrusions, on the order of <10 5 years (~10 4 years for the initial potassic stage), as determined by dating results (Arribas et al, 1995a;Garwin, 2002;Buret et al, 2016) and consistent with the constraints from modeling (Cathles, 1977;Shinohara & Hedenquist, 1997;Weis, 2015). If the episodic fracture events reach the surface, they may be represented by phreatomagmatic activity, such as the eruption of altered material from active volcanic-hydrothermal systems at White Island, New Zealand, and Ontake, Japan (Hedenquist et al, 1993;Minami et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Zonation of Sulfate and Sulfide Minerals and Isotopic Composition in the Far Southeast Porphyry and Lepanto Epithermal Cu–Au Deposits, Philippines

2017

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The world-class Far Southeast (FSE) porphyry system, Philippines, includes the FSE Cu-Au porphyry deposit, the Lepanto Cu-Au high-sulfidation deposit and the Victoria-Teresa Au-Ag intermediate-sulfidation veins, centered on the intrusive complex of dioritic composition. The Lepanto and FSE deposits are genetically related and both share an evolution characterized by early stage 1 alteration (deep FSE potassic, shallow Lepanto advanced argillic-silicic, both at~1.4 Ma), followed by stage 2 phyllic alteration (at~1.3 Ma); the dominant ore mineral deposition within the FSE porphyry and the Lepanto epithermal deposits occurred during stage 2. We determined the chemical and S isotopic composition of sulfate and sulfide minerals from Lepanto, including stage 1 alunite (12 to 28 permil), aluminum-phosphate-sulfate (APS) minerals (14 to 21 permil) and pyrite (À4 to 2 permil), stage 2 sulfides (mainly enargite-luzonite and some pyrite, À10 to À1 permil), and late stage 2 sulfates (barite and anhydrite, 21 to 27 permil). The minerals from FSE include stage 2 chalcopyrite (1.6 to 2.6 permil), pyrite (1.1 to 3.4 permil) and anhydrite (13 to 25 permil). The whole-rock S isotopic composition of weakly altered syn-mineral intrusions is 2.0 permil. Stage 1 quartz-alunite-pyrite of the Lepanto lithocap, above about 650 m elevation, formed from acidic condensates of magmatic vapor at the same time as hypersaline liquid formed potassic alteration (biotite) near sea level. The S isotopic composition of stage 1 alunite-pyrite record temperatures of approximately 300-400°C for the vapor condensate directly over the porphyry deposit; this cooled to <250°C as the acidic condensate flowed to the NW along the Lepanto fault where it cut the unconformity at the top of the basement. Stage 1 alunite at the base of the advanced argillic lithocap over FSE contains cores of APS minerals with Sr, Ba and Ca; based on back-scattered electron images and ion microprobe data, these APS minerals show a large degree of chemical and S-isotopic heterogeneity within and between samples. The variation in S isotopic values in these finely banded stage 1 alunite and APS minerals (16 permil range), as well as that of pyrite (6 permil range) was due largely to changes in temperature, and perhaps variation in redox conditions (average~2:1 H 2 S:SO 4 ). Such fluctuations could have been related to fluid pulses caused by injection of mafic melt into the diorite magma chamber, supported by mafic xenoliths hosted in diorite of an earlier intrusion. Resource Geology Vol. 67, bs_bs_banner fluids were relatively oxidized in the Lepanto lithocap, with an H 2 S:SO 4 ratio of about 4. The oxidation resulted from cooling, which was caused by boiling during ascent and then dilution with steam-heated meteoric water in the lithocap. This cooling also resulted in the sulfidation state of minerals increasing from chalcopyrite stability in the porphyry deposit to that of enargite in the lithocap-hosted high-sulfidation deposit. The temperature at the base of the lithoca...

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Section: Discussionmentioning

confidence: 99%

Zonation of Sulfate and Sulfide Minerals and Isotopic Composition in the Far Southeast Porphyry and Lepanto Epithermal Cu–Au Deposits, Philippines

2017

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“…This means that the crystallisation of titanite has the potential to impart a significant positive Eu anomaly on residual melts, which may be inherited by phases which crystallise subsequently (e.g. Buret et al, 2016;Lee et al, 2017). Critical to this is the timing of titanite crystallisation.…”

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confidence: 99%

The effect of titanite crystallisation on Eu and Ce anomalies in zircon and its implications for the assessment of porphyry Cu deposit fertility

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Wilkinson

Armstrong

2017

Earth and Planetary Science Letters

170

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The redox sensitivity of Ce and Eu anomalies in zircon has been clearly demonstrated by experimental studies, and these may represent an important tool in the exploration for porphyry Cu deposits which are thought to be derived from oxidised magmas. These deposits are significant because they are the source of much of the world's copper and almost all of the molybdenum and rhenium, key elements in many modern technologies. However, Ce and Eu anomalies in zircon are also affected by the co-crystallisation of REE bearing phases, such as titanite. Here, we report the trace element chemistry of zircons from titanite-bearing intrusions associated with mineralisation at the world class Oyu Tolgoi porphyry Cu-Au deposit (Mongolia). Based on these data, we suggest that neither zircon Eu/Eu*, nor Ce4+/Ce3+ are robust proxies for melt redox conditions, because they are both too strongly dependent on melt REE concentrations, which are usually poorly constrained and controlled by the crystallisation of titanite and other REE-bearing phases. In spite of this, Eu/Eu* can broadly distinguish between fertile and barren systems, so may still be an indicator of porphyry magma fertility, and a useful tool for exploration

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“…Porphyry deposits are produced by dynamically evolving magmatic-hydrothermal systems (e.g., Sillitoe, 2010). Detailed description of parameters can be found in McInnes et al (2005a) and Fu et al (2010) 1 Emplacement depth is defined as the distance from the paleosurface to the top of the igneous body 2 The igneous body has cooled when it reaches the same temperature as the surrounding country rock 3 Magmatic cooling refers to the cooling from emplacement to the cooled state as defined above 4 Exhumation cooling refers to the interval from the cooled state through cooling to surface temperature of 10°C 5 Exhumation rate of intrusion refers to the average exhumation rate for the intrusion from the emplacement to the paleosurface 6 Exhumation rate of country rock refers to the average exhumation rate for the country rocks from deep to the paleosurface 7 Age of exposure is defined as the age when the top of the igneous body is exposed to the paleosurface 8 Estimated eroded thickness refers to the eroded thickness of the intrusion since it was exposed to the paleosurface Understanding the duration of genetic magmatic-hydrothermal processes is fundamental to exploring the mechanisms of porphyry deposit formation (McInnes et al, 2005a, b;Chiaradia et al, 2009Chiaradia et al, , 2013von Quadt et al, 2011;Buret et al, 2016Buret et al, , 2017. The suite of radiometric ages obtained in this study (Table 2), combined with previously published geochronological and thermochronological data for the Pulang deposit (Table 1), places good temporal constraints on the initiation and duration of magmatic-hydrothermal activity at Pulang.…”

Section: Formation and Duration Of The Pulang Porphyry Systemmentioning

confidence: 99%

“…5,6). Recent precise geochronological studies of porphyry deposits worldwide have indicated that deposits may form within tens of thousands of years (e.g., Henry et al, 1997;Shinohara and Hedenquist, 1997;Pollard et al, 2005;von Quadt et al, 2011;Chiaradia et al, 2013;Buret et al, 2016Buret et al, , 2017 or several million years (e.g., Ballard et al, 2001;Maksaev et al, 2006;Harris et al, 2008;Sillitoe and Mortensen, 2010;Barra et al, 2013;Deckart et al, 2013, 2014, andreferences therein;Leng et al, 2013). These longlived magmatic-hydrothermal events are typically attributed to episodic buildup and evolution of the underlying more voluminous pluton that feeds the upper crustal porphyritic intrusive complex (e.g., Sillitoe, 2010;Sillitoe and Mortensen, 2010;Chelle-Michou et al, 2014;Chiaradia and Caricchi, 2017;Leng et al, 2018).…”

Section: Formation and Duration Of The Pulang Porphyry Systemmentioning

confidence: 99%

Quantifying Exhumation at the Giant Pulang Porphyry Cu-Au Deposit Using U-Pb-He Dating

et al. 2018

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The Triassic Pulang porphyry Cu-Au deposit, located in the South Yidun terrane, is the oldest and one of the largest porphyry deposits in the southeastern Tibetan Plateau. The mineralization occurs mostly in the potassic alteration zone of the Pulang intrusive complex. U-Pb-He triple dating, namely apatite (U-Th)/He, zircon U-Pb, and zircon (U-Th)/He dating, together with inverse thermal modeling, reveals that the Pulang complex was emplaced at a paleodepth of ~5.0 to 6.5 km at 215 ± 2 Ma. The deep-level emplacement of the complex, coupled with the episodic replenishment of the magma chamber, gave rise to the establishment of a prolonged magmatic-hydrothermal system at Pulang. Although a range of single-grain zircon and apatite (U-Th)/He ages were obtained on each sample, the weighted mean zircon and apatite (U-Th)/He ages vary systematically with elevation, defining a multistage cooling/denudation history at Pulang. Specifically, three phases of cooling were recognized from inverse thermal modeling, including rapid cooling (80°-120°C/m.y.) in the Late Triassic, moderate cooling (3°-5°C/m.y.) from the Late Triassic to Early Cretaceous, and a protracted slow cooling period (<1°C/m.y.) from the Early Cretaceous to the present day. The first phase of cooling can be mainly attributed to magmatic cooling, whereas the later two phases of cooling were predominantly controlled by uplift and denudation processes. Moreover, the remarkable decrease in the cooling rate from the second to the third phase can be linked to a decreasing erosion rate during the third phase, supported by age-elevation relationships. Overall, our results indicate that the Pulang complex experienced two stages of exhumation at 33 to 45 m/m.y. and 5 to 17 m/m.y. Based on these data, we estimate that approximately 558-to 1,099-m thickness of materials have been removed from the Pulang complex during uplift and erosion, including a large volume of ore. The long time span (>50 m.y.) of extremely slow cooling and erosion at Pulang could be related to the formation and preservation of a peneplain on the southeastern Tibetan Plateau since the Late Cretaceous. A relict peneplain thus signifies a favorable tectonic environment for the preservation of ancient porphyry systems worldwide.

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From a long-lived upper-crustal magma chamber to rapid porphyry copper emplacement: Reading the geochemistry of zircon crystals at Bajo de la Alumbrera (NW Argentina)

Cited by 144 publications

References 68 publications

Zonation of Sulfate and Sulfide Minerals and Isotopic Composition in the Far Southeast Porphyry and Lepanto Epithermal Cu–Au Deposits, Philippines

Zonation of Sulfate and Sulfide Minerals and Isotopic Composition in the Far Southeast Porphyry and Lepanto Epithermal Cu–Au Deposits, Philippines

The effect of titanite crystallisation on Eu and Ce anomalies in zircon and its implications for the assessment of porphyry Cu deposit fertility

Quantifying Exhumation at the Giant Pulang Porphyry Cu-Au Deposit Using U-Pb-He Dating

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