Porphyry copper deposits, the principal source of copper and molybdenum, form at convergent margi... more Porphyry copper deposits, the principal source of copper and molybdenum, form at convergent margins. Copper is precipitated from fluids associated with cooling magmas that have formed in the mantle and evolved at mid- to lower crustal levels, before rising toward the surface where they saturate and exsolve an aqueous fluid and copper. Despite advances in the understanding of their formation, there are still underexplored aspects of the genesis of porphyry copper deposits. Here we examine the role played by magma injection rates into the upper crust on the formation of porphyry copper deposits with different copper endowments. Mass balance calculations suggest that supergiant porphyry copper deposits (>10 million tonnes copper) require magma volumes (up to >2500 km3) and magma injection rates (>0.001 km3 year−1) typical of large volcanic eruptions from rift, hot spot, and subduction-related settings. Because large volcanic eruptions would destroy magmatic-hydrothermal system...
This overview illustrates the processes controlling magma fertility in the formation of porphyry ... more This overview illustrates the processes controlling magma fertility in the formation of porphyry Cu-Au deposits. Magma fertility means all magmatic parameters (e.g., metal and volatile contents, magma and fluid volumes) that might result in higher amounts of metals, which are exsolvable from the magma. Mantle source processes seem to play a fundamental role in the enrichment of primary melts with H2O, S, and Cl, all essential ingredients to form porphyry deposits, but do not have a particular role in Cu enrichment. Cu-rich porphyry Cu-Au deposits (i.e., with Au/Cu ~4 × 10–6) are associated with large magmatic volumes accumulated in the lower thick crust of continental arcs during long-lived periods of compression in a synsubduction environment. Mineralization occurs after such accumulations have reached significant volumes and is the result of the transfer of hydrous magmas from deep to shallower crustal levels, probably favored by tectonic stress changes. Au-rich porphyry Cu-Au dep...
Porphyry deposits are large, low-grade metal ore bodies that are formed from hydrothermal fluids ... more Porphyry deposits are large, low-grade metal ore bodies that are formed from hydrothermal fluids derived from an underlying magma reservoir. They are important as major sources of critical metals for industry and society, such as copper and gold. However, the magmatic and redox processes required to form economic-grade porphyry deposits remain poorly understood. In this Review, we discuss advances in understanding crustal magmatic conditions that favour the formation of porphyry Cu deposits at subduction zones. Chalcophile metal fertility of mantle-derived arc magmas is primarily modulated by the amount and nature of residual sulfide phases in the mantle wedge during partial melting. Crustal thickness influences the longevity of lower crustal magma reservoirs and the sulfide saturation history. For example, in thick crust, prolonged magma activity with hydrous and oxidized evolving magmas increases ore potential, whereas thin crust favours high chalcophile element fertility, owing to late sulfide saturation. A shallow depth (<7 km) of fluid exsolution might play a role in increasing Au precipitation efficiency, as immiscible sulfide melts act as a transient storage of chalcophile metals and liberate them to ore fluids. Future studies should aim to identify the predominant sulfide phases in felsic systems to determine their influence on the behaviour of chalcophile elements during magma differentiation. The magmatic processes required to form economic-grade porphyry Cu deposits are still poorly understood. This Review discusses the magmatic, redox and hydrothermal processes required for porphyry ore formation, revealing that both crustal thickness and depth of ore body emplacement can influence metal endowment. Prolonged injection of hydrous basaltic magmas and accumulation of andesitic magmas in the mid to lower crust are prerequisites to forming large porphyry deposits because these processes are required to maintain a long-lived magmatic system and associated hydrothermal activity in the shallow crust. Crustal thickness influences the duration and volume of magma activity, timing of sulfide saturation, chalcophile element fertility and emplacement depth of porphyry intrusions. Thick crusts (>40 km) increase porphyry Cu ore potential by producing voluminous and hydrous magmas in long-lived (≥2–3 Ma) mid to lower crustal magma reservoirs at ∼30–70 km depth, which can result in the formation of supergiant to giant porphyry Cu deposits if a combination of other ore-forming conditions is fulfilled. In thin crust (<40 km), late sulfide saturation and high chalcophile element fertility in shallow magma reservoirs (∼5–15 km depth) increase Au-rich porphyry Cu ore potential. Immiscible sulfide melts can act as temporary metal storage locations when the sulfide melts and exsolved fluids interact in shallow magma reservoirs. Depth of porphyry emplacement (∼1–7 km), magma alkalinity and Au fertility control Au endowments in porphyry Cu deposits Prolonged injection of hydrous basaltic magmas and accumulation of andesitic magmas in the mid to lower crust are prerequisites to forming large porphyry deposits because these processes are required to maintain a long-lived magmatic system and associated hydrothermal activity in the shallow crust. Crustal thickness influences the duration and volume of magma activity, timing of sulfide saturation, chalcophile element fertility and emplacement depth of porphyry intrusions. Thick crusts (>40 km) increase porphyry Cu ore potential by producing voluminous and hydrous magmas in long-lived (≥2–3 Ma) mid to lower crustal magma reservoirs at ∼30–70 km depth, which can result in the formation of supergiant to giant porphyry Cu deposits if a combination of other ore-forming conditions is fulfilled. In thin crust (<40 km), late sulfide saturation and high chalcophile element fertility in shallow magma reservoirs (∼5–15 km depth) increase Au-rich porphyry Cu ore potential. Immiscible sulfide melts can act as temporary metal storage locations when the sulfide melts and exsolved fluids interact in shallow magma reservoirs. Depth of porphyry emplacement (∼1–7 km), magma alkalinity and Au fertility control Au endowments in porphyry Cu deposits
The composite Meghri-Ordubad and Bargushat plutons and associated porphyry Cu-Mo deposits of the ... more The composite Meghri-Ordubad and Bargushat plutons and associated porphyry Cu-Mo deposits of the Zangezur-Ordubad region, southernmost Lesser Caucasus, were emplaced during a long-lasting, stationary Tertiary magmatic evolution. All magmas have a subduction-related signature. Radiogenic isotopes reveal a mantle-dominated magmatism, with the mantle component becoming more predominant with time. Trace element geochemistry indicates progressive thickening of the crust from the Eocene to the Miocene. Eocene calcalkaline, normal arc (non-adakitic) magmatic activity was related to subduction of the Neotethys beneath Eurasia, and magmatism was dominated by fluid-related enrichment. The Eocenece magmatic stage generated the first pulse of porphyry Cu-Mo deposits. During collision to post-collision evolution, magmatism evolved to shoshonitic during the Oligocene, and calc-alkaline to high-K calc-alkaline and adakitic during the Late Oligocene and Mio-Pliocene. The younger magmatic evolution ...
The Jalal Abad magmatic rocks, situated at the southern edge of the Saghand-Bafgh-Zarand district... more The Jalal Abad magmatic rocks, situated at the southern edge of the Saghand-Bafgh-Zarand district, include a thick pile of Cadomian extrusive and pyroclastic units intruded by younger granitoid stocks. New zircon U–Pb ages show eruptions at ∼552 Ma, followed by emplacement of granodiorite at ∼537 Ma. The Jalal Abad magmatic rocks have typical high-K and shoshonitic signatures, and are characterized by enrichment in large-ion lithophile elements (LILEs) and depletion in high-field-strength elements (HFSE). Zircon ɛHf(t) from the Jalal Abad magmatic rocks ranges from +3.9 to −3.9 for volcanic rocks and −1.2 to +8.1 for granodiorite. Zircon δ18O values for the Jalal Abad are variable from +5.1 to +8.8‰, progressively higher than those of mantle-derived melts. The whole-rock ɛNd(t) values range between −7.7 to −7.4 for granodiorite, −4.6 to −3 for volcanic rocks and −6.2 to −8.2 for ignimbrites/tuff. The whole-rock Nd and zircon Hf crustal model ages (TDMC) for the Jalal Abad magmatic r...
New and compiled geochemical, isotopic and geochronological data allow us to propose a new explan... more New and compiled geochemical, isotopic and geochronological data allow us to propose a new explanation for Paleogene oceanic magmatic rocks along the Iran–Iraq border. These rocks are represented by a thick pile (>1000 m) of pillow lavas and pelagic sediments and underlying plutonic rocks. These are sometimes argued to represent a Paleogene ophiolite but there are no associated mantle rocks. Integrated zircon U–Pb ages, bulk rock major and trace element and radiogenic isotope data indicate that these rocks are more likely related to forearc rifting due to extreme extension during Late Paleogene time which also triggered high-flux magmatism in the Urumieh–Dokhtar Magmatic Belt and exhumation of core complexes in Iran. These observations are most consistent with formation of the Paleogene oceanic igneous rocks in a >220 km long forearc rift zone.Supplementary material: Detailed analytical procedure and tables S1 to S6 are available at: https://doi.org/10.6084/m9.figshare.c.4972994
The redox state of Earth’s upper mantle in several tectonic settings, such as cratonic mantle, oc... more The redox state of Earth’s upper mantle in several tectonic settings, such as cratonic mantle, oceanic mantle, and mantle wedges beneath magmatic arcs, has been well documented. In contrast, oxygen fugacity () data of upper mantle under orogens worldwide are rare, and the mechanism responsible for the mantle condition under orogens is not well constrained. In this study, we investigated the of mantle xenoliths derived from the southern Tibetan lithospheric mantle beneath the Himalayan orogen, and that of postcollisional ultrapotassic volcanic rocks hosting the xenoliths. The of mantle xenoliths ranges from ΔFMQ = +0.5 to +1.2 (where ΔFMQ is the deviation of log from the fayalite-magnetite-quartz buffer), indicating that the southern Tibetan lithospheric mantle is more oxidized than cratonic and oceanic mantle, and it falls within the typical range of mantle wedge values. Mineralogical evidence suggests that water-rich fluids and sediment melts liberated from both the subducting Neo-...
We focused on the Pirin–Pangeon–Thasos carbonate sequence of the Rhodope thrust system, combining... more We focused on the Pirin–Pangeon–Thasos carbonate sequence of the Rhodope thrust system, combining Sr isotopes from marble with U–Pb dating of detrital zircons from interlayered schists with outcrop near the villages of Ilindentsi and Petrovo in Bulgaria. The youngest zircon age at Ilindentsi is 266 Ma, i.e. Middle Permian, while the youngest zircon at Petrovo yielded an age of 290 Ma, i.e. Early Permian. Strontium isotopes range from 0.707420 to 0.707653, and are consistent with a Middle Permian maximum depositional age. Middle Permian sedimentation of this carbonate platform most likely occurred along the Eurasian margin rather than the Gondwana margin.
Porphyry copper deposits, the principal source of copper and molybdenum, form at convergent margi... more Porphyry copper deposits, the principal source of copper and molybdenum, form at convergent margins. Copper is precipitated from fluids associated with cooling magmas that have formed in the mantle and evolved at mid- to lower crustal levels, before rising toward the surface where they saturate and exsolve an aqueous fluid and copper. Despite advances in the understanding of their formation, there are still underexplored aspects of the genesis of porphyry copper deposits. Here we examine the role played by magma injection rates into the upper crust on the formation of porphyry copper deposits with different copper endowments. Mass balance calculations suggest that supergiant porphyry copper deposits (>10 million tonnes copper) require magma volumes (up to >2500 km3) and magma injection rates (>0.001 km3 year−1) typical of large volcanic eruptions from rift, hot spot, and subduction-related settings. Because large volcanic eruptions would destroy magmatic-hydrothermal system...
This overview illustrates the processes controlling magma fertility in the formation of porphyry ... more This overview illustrates the processes controlling magma fertility in the formation of porphyry Cu-Au deposits. Magma fertility means all magmatic parameters (e.g., metal and volatile contents, magma and fluid volumes) that might result in higher amounts of metals, which are exsolvable from the magma. Mantle source processes seem to play a fundamental role in the enrichment of primary melts with H2O, S, and Cl, all essential ingredients to form porphyry deposits, but do not have a particular role in Cu enrichment. Cu-rich porphyry Cu-Au deposits (i.e., with Au/Cu ~4 × 10–6) are associated with large magmatic volumes accumulated in the lower thick crust of continental arcs during long-lived periods of compression in a synsubduction environment. Mineralization occurs after such accumulations have reached significant volumes and is the result of the transfer of hydrous magmas from deep to shallower crustal levels, probably favored by tectonic stress changes. Au-rich porphyry Cu-Au dep...
Porphyry deposits are large, low-grade metal ore bodies that are formed from hydrothermal fluids ... more Porphyry deposits are large, low-grade metal ore bodies that are formed from hydrothermal fluids derived from an underlying magma reservoir. They are important as major sources of critical metals for industry and society, such as copper and gold. However, the magmatic and redox processes required to form economic-grade porphyry deposits remain poorly understood. In this Review, we discuss advances in understanding crustal magmatic conditions that favour the formation of porphyry Cu deposits at subduction zones. Chalcophile metal fertility of mantle-derived arc magmas is primarily modulated by the amount and nature of residual sulfide phases in the mantle wedge during partial melting. Crustal thickness influences the longevity of lower crustal magma reservoirs and the sulfide saturation history. For example, in thick crust, prolonged magma activity with hydrous and oxidized evolving magmas increases ore potential, whereas thin crust favours high chalcophile element fertility, owing to late sulfide saturation. A shallow depth (<7 km) of fluid exsolution might play a role in increasing Au precipitation efficiency, as immiscible sulfide melts act as a transient storage of chalcophile metals and liberate them to ore fluids. Future studies should aim to identify the predominant sulfide phases in felsic systems to determine their influence on the behaviour of chalcophile elements during magma differentiation. The magmatic processes required to form economic-grade porphyry Cu deposits are still poorly understood. This Review discusses the magmatic, redox and hydrothermal processes required for porphyry ore formation, revealing that both crustal thickness and depth of ore body emplacement can influence metal endowment. Prolonged injection of hydrous basaltic magmas and accumulation of andesitic magmas in the mid to lower crust are prerequisites to forming large porphyry deposits because these processes are required to maintain a long-lived magmatic system and associated hydrothermal activity in the shallow crust. Crustal thickness influences the duration and volume of magma activity, timing of sulfide saturation, chalcophile element fertility and emplacement depth of porphyry intrusions. Thick crusts (>40 km) increase porphyry Cu ore potential by producing voluminous and hydrous magmas in long-lived (≥2–3 Ma) mid to lower crustal magma reservoirs at ∼30–70 km depth, which can result in the formation of supergiant to giant porphyry Cu deposits if a combination of other ore-forming conditions is fulfilled. In thin crust (<40 km), late sulfide saturation and high chalcophile element fertility in shallow magma reservoirs (∼5–15 km depth) increase Au-rich porphyry Cu ore potential. Immiscible sulfide melts can act as temporary metal storage locations when the sulfide melts and exsolved fluids interact in shallow magma reservoirs. Depth of porphyry emplacement (∼1–7 km), magma alkalinity and Au fertility control Au endowments in porphyry Cu deposits Prolonged injection of hydrous basaltic magmas and accumulation of andesitic magmas in the mid to lower crust are prerequisites to forming large porphyry deposits because these processes are required to maintain a long-lived magmatic system and associated hydrothermal activity in the shallow crust. Crustal thickness influences the duration and volume of magma activity, timing of sulfide saturation, chalcophile element fertility and emplacement depth of porphyry intrusions. Thick crusts (>40 km) increase porphyry Cu ore potential by producing voluminous and hydrous magmas in long-lived (≥2–3 Ma) mid to lower crustal magma reservoirs at ∼30–70 km depth, which can result in the formation of supergiant to giant porphyry Cu deposits if a combination of other ore-forming conditions is fulfilled. In thin crust (<40 km), late sulfide saturation and high chalcophile element fertility in shallow magma reservoirs (∼5–15 km depth) increase Au-rich porphyry Cu ore potential. Immiscible sulfide melts can act as temporary metal storage locations when the sulfide melts and exsolved fluids interact in shallow magma reservoirs. Depth of porphyry emplacement (∼1–7 km), magma alkalinity and Au fertility control Au endowments in porphyry Cu deposits
The composite Meghri-Ordubad and Bargushat plutons and associated porphyry Cu-Mo deposits of the ... more The composite Meghri-Ordubad and Bargushat plutons and associated porphyry Cu-Mo deposits of the Zangezur-Ordubad region, southernmost Lesser Caucasus, were emplaced during a long-lasting, stationary Tertiary magmatic evolution. All magmas have a subduction-related signature. Radiogenic isotopes reveal a mantle-dominated magmatism, with the mantle component becoming more predominant with time. Trace element geochemistry indicates progressive thickening of the crust from the Eocene to the Miocene. Eocene calcalkaline, normal arc (non-adakitic) magmatic activity was related to subduction of the Neotethys beneath Eurasia, and magmatism was dominated by fluid-related enrichment. The Eocenece magmatic stage generated the first pulse of porphyry Cu-Mo deposits. During collision to post-collision evolution, magmatism evolved to shoshonitic during the Oligocene, and calc-alkaline to high-K calc-alkaline and adakitic during the Late Oligocene and Mio-Pliocene. The younger magmatic evolution ...
The Jalal Abad magmatic rocks, situated at the southern edge of the Saghand-Bafgh-Zarand district... more The Jalal Abad magmatic rocks, situated at the southern edge of the Saghand-Bafgh-Zarand district, include a thick pile of Cadomian extrusive and pyroclastic units intruded by younger granitoid stocks. New zircon U–Pb ages show eruptions at ∼552 Ma, followed by emplacement of granodiorite at ∼537 Ma. The Jalal Abad magmatic rocks have typical high-K and shoshonitic signatures, and are characterized by enrichment in large-ion lithophile elements (LILEs) and depletion in high-field-strength elements (HFSE). Zircon ɛHf(t) from the Jalal Abad magmatic rocks ranges from +3.9 to −3.9 for volcanic rocks and −1.2 to +8.1 for granodiorite. Zircon δ18O values for the Jalal Abad are variable from +5.1 to +8.8‰, progressively higher than those of mantle-derived melts. The whole-rock ɛNd(t) values range between −7.7 to −7.4 for granodiorite, −4.6 to −3 for volcanic rocks and −6.2 to −8.2 for ignimbrites/tuff. The whole-rock Nd and zircon Hf crustal model ages (TDMC) for the Jalal Abad magmatic r...
New and compiled geochemical, isotopic and geochronological data allow us to propose a new explan... more New and compiled geochemical, isotopic and geochronological data allow us to propose a new explanation for Paleogene oceanic magmatic rocks along the Iran–Iraq border. These rocks are represented by a thick pile (>1000 m) of pillow lavas and pelagic sediments and underlying plutonic rocks. These are sometimes argued to represent a Paleogene ophiolite but there are no associated mantle rocks. Integrated zircon U–Pb ages, bulk rock major and trace element and radiogenic isotope data indicate that these rocks are more likely related to forearc rifting due to extreme extension during Late Paleogene time which also triggered high-flux magmatism in the Urumieh–Dokhtar Magmatic Belt and exhumation of core complexes in Iran. These observations are most consistent with formation of the Paleogene oceanic igneous rocks in a >220 km long forearc rift zone.Supplementary material: Detailed analytical procedure and tables S1 to S6 are available at: https://doi.org/10.6084/m9.figshare.c.4972994
The redox state of Earth’s upper mantle in several tectonic settings, such as cratonic mantle, oc... more The redox state of Earth’s upper mantle in several tectonic settings, such as cratonic mantle, oceanic mantle, and mantle wedges beneath magmatic arcs, has been well documented. In contrast, oxygen fugacity () data of upper mantle under orogens worldwide are rare, and the mechanism responsible for the mantle condition under orogens is not well constrained. In this study, we investigated the of mantle xenoliths derived from the southern Tibetan lithospheric mantle beneath the Himalayan orogen, and that of postcollisional ultrapotassic volcanic rocks hosting the xenoliths. The of mantle xenoliths ranges from ΔFMQ = +0.5 to +1.2 (where ΔFMQ is the deviation of log from the fayalite-magnetite-quartz buffer), indicating that the southern Tibetan lithospheric mantle is more oxidized than cratonic and oceanic mantle, and it falls within the typical range of mantle wedge values. Mineralogical evidence suggests that water-rich fluids and sediment melts liberated from both the subducting Neo-...
We focused on the Pirin–Pangeon–Thasos carbonate sequence of the Rhodope thrust system, combining... more We focused on the Pirin–Pangeon–Thasos carbonate sequence of the Rhodope thrust system, combining Sr isotopes from marble with U–Pb dating of detrital zircons from interlayered schists with outcrop near the villages of Ilindentsi and Petrovo in Bulgaria. The youngest zircon age at Ilindentsi is 266 Ma, i.e. Middle Permian, while the youngest zircon at Petrovo yielded an age of 290 Ma, i.e. Early Permian. Strontium isotopes range from 0.707420 to 0.707653, and are consistent with a Middle Permian maximum depositional age. Middle Permian sedimentation of this carbonate platform most likely occurred along the Eurasian margin rather than the Gondwana margin.
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