Temporal and genetic link between incremental pluton assembly and pulsed porphyry Cu-Mo formation in accretionary orogens

Rezeau, Hervé; Moritz, Robert; Wotzlaw, Jörn‐Frederik; Tayan, Rodrik; Melkonyan, Rafael; Ulianov, Alexey; Selby, David; d’Abzac, François-Xavier; Stern, Richard A.

doi:10.1130/g38088.1

Cited by 88 publications

(51 citation statements)

References 23 publications

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“…The ages measured in this study, in conjunction with published ages, suggest that magmatism and resulting mineralization within the central deposit must have occurred over ~500 ka at most (between 25.02 Ma [unmineralized Cabresto Lake zircon age] and 24.50 Ma [barren dike zircon age]). This is consistent with a growing body of evidence for episodic porphyry mineralization (e.g., Carten et al, 1988;Seedorff and Einaudi, 2004;Rosera et al, 2013;Chelle-Michou et al, 2015;Mercer et al, 2015b;Spencer et al, 2015;Rezeau et al, 2016).…”

Section: Age Of Intrusions Within the Central Depositsupporting

confidence: 89%

Intrusive history of the Oligocene Questa porphyry molybdenum deposit, New Mexico

2019

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Subsurface mapping and core analyses of upper crustal intrusions and mineralization at the Questa porphyry molybdenum deposit, New Mexico, reveal that Mo-mineralization occurred through episodic emplacement of at least six intrusive units. The structure of intrusions associated with the Questa deposit is documented in a series of detailed cross sections and visualized with a 3D animation. Mineralizing intrusions are underlain by two post-mineralization intrusions and cut by late-stage barren dikes. The plutonic complex was structurally focused along a system of preexisting flat-lying faults and their associated fractures. Mineralization is spatially associated with specific intrusive units in the subsurface, and the highest Mo ore grades within established ore blocks are structurally associated with the smallest intrusions. Existing U/Pb thermal ionization mass spectrometry (TIMS) zircon geochronology in conjunction with new relative chronology presented herein indicate that mineralization began before 24.91 Ma. We present three new chemical abrasion U/Pb TIMS zircon ages-one from an amphibole-bearing intrusion associated with high-grade mineralization (dark-matrix porphyry, 24.74 ± 0.37 Ma), a rhyolite dike that cuts ore-grade rocks (24.50 ± 0.02 Ma), and an equigranular granite discovered during deep drilling (23.67 ± 0.02 Ma). The dark-matrix porphyry contains clasts of an earlier amphibole-free intrusion that is spatially associated with low-grade mineralization. Thus, mineralizing intrusions were, in part, intruded into slightly older porphyries, confirming that episodic mineralization continued after 24.91 Ma. The age of the barren dike (24.50 ± 0.02 Ma) is indistinguishable from that of a previously dated granite porphyry that is associated with low-grade mineralization (<0.05 wt% MoS 2 ; Questa granite porphyry). These data suggest that mineralization waned by 24.5 Ma and that ore deposition occurred over ~500 ka. The new 23.67 Ma age of the deep equigranular granite, which underlies the Questa granite porphyry, further suggests that intrusions underlying the deposit were not related to mineralization. Detailed subsurface mapping and exploratory drilling indicate that intrusions associated with mineralization were small in volume and cooled rapidly, as evidenced by multiple internal contacts within sheets and rebrecciation textures. On the basis of observed cross-section reconstructions, petrology, alteration, and mineralization, the porphyritic rhyolite intrusions associated with mineralization in one of the largest orebodies in the deposit (the deep northeast) are less than 20-m-thick sheets that are separated by andesite wall rock. Thus, there is no evidence that this orebody formed above a cylindrical magma conduit that facilitated rapid convection, as is often modeled in these systems. We hypothesize that a set of similarly small-volume intrusions were responsible for the bulk of the ore in the southwest ore zone. Our interpretation that the mineralizing intrusions are small, thin, and subhorizontal ...

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Section: Age Of Intrusions Within the Central Depositsupporting

confidence: 89%

Intrusive history of the Oligocene Questa porphyry molybdenum deposit, New Mexico

2019

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“…2), the ages of porphyry Cu and Mo deposits in both areas may help to better understand the magmatic and mineralization activities in the whole region. Compared to the Cenozoic metallogenic evolution of the SAB proposed by Moritz et al (2016b) and Rezeau et al (2016), the Siah Kamar deposit fits with the second Cenozoic event dated as Oligocene, similar to the PCDs in northwest Iran. The Siah Kamar deposit is nearly coeval with the Paragachay and the first stage of mineralization in the world-class Kadjaran PCDs, although postdates most of the PCDs in SAB, especially those of the Late Eocene age (Fig.…”

supporting

confidence: 61%

“…2). The only younger event is the second stage of mineralization in the Kadjaran PCD, dating at 20.48 ± 0.1 Ma (molybdenite Re-Os age), as well as Cu-rich epithermal veins overprinting porphyritic granodioritic dikes (dated at 22.2 ± 0.30 Ma) (Rezeau et al 2016).…”

mentioning

confidence: 99%

U-Pb zircon and Re-Os molybdenite age of the Siah Kamar porphyry molybdenum deposit, NW Iran

Simmonds

Moazzen

Selby

2019

International Geology Review

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The Siah Kamar porphyry Mo deposit is the newly discovered deposit of this type in the Neo Tethysrelated Urumieh-Dokhtar magmatic arc, northwest Iran. Mineralization occurs as stock-work quartzmolybdenite and mono-mineralic molybdenite veinlets within the porphyry quartz-monzonite stock and the country rocks, accompanied by locally scattered later-stage and cross-cutting quartz-chalcopyrite-pyrite veinlets in the trachy-andesite and trachy-basalt country rocks. U-Pb zircon geochronology of the porphyry stock yielded Early Oligocene dates of 32.7 ± 0.4 to 30.9 ± 0.4 Ma (at 2σ level). The Th/U ratios of the zircon range between 0.48 and 0.77, and possess initial εHf(t) values of 3.2 to 12.1, which may suggest a dominant mantle source for the magma. Molybdenite separates yielded rhenium contents between ~10 and 41 ppm (average ~26 ppm, n = 4) and slightly younger Re-Os ages compared to the porphyry stock, ranging from 29.1 ± 0.2 to 28.1 ± 0.2 Ma (at 2σ level). The Siah Kamar porphyry Mo deposit is nearly temporally coeval with the vein-type Cu-Mo-Au mineralization in the Qarachilar and the Haft Cheshmeh porphyry Cu deposit, corresponding to the second porphyry Cu-Mo mineralization epoch in NW Iran. However, it is younger than the majority of the porphyry Cu deposits in the southern Lesser Caucasus, only showing temporal correlation with the Paragachay and first-stage Kadjaran porphyry Cu deposits. Moreover, it is older than all the porphyry Cu-Mo systems across the central and southeastern parts of the Urumieh-Dokhtar magmatic arc, except the Bondar Hanza deposit, which is nearly coeval with the Siah Kamar porphyry Mo deposit. All these data reveal an old to young trend along the UDMA and the porphyry Cu belt of Iran, further testifying the diachronous and later closure of the Neo-Tethyan oceanic basin in central and SE Iran.

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“…This includes both compositional and S (this study) as well as O (e.g., Fekete et al, 2016) and H isotopic analyses, integrated with information from fluid inclusion assemblages (e.g., Redmond et al, 2004;Landtwing et al, 2005). Such information from porphyry ore deposits can also be contrasted with the evolution of apparently barren intrusive systems (e.g., Rezeau et al, 2016) to determine regional controls on magmatism related to ore genesis.…”

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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Temporal and genetic link between incremental pluton assembly and pulsed porphyry Cu-Mo formation in accretionary orogens

Cited by 88 publications

References 23 publications

Intrusive history of the Oligocene Questa porphyry molybdenum deposit, New Mexico

Intrusive history of the Oligocene Questa porphyry molybdenum deposit, New Mexico

U-Pb zircon and Re-Os molybdenite age of the Siah Kamar porphyry molybdenum deposit, NW Iran

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

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