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The Naozhi deposit of northeast China comprises intermediate-sulfidation epithermal-style veins and subeconomic, porphyry-style Cu mineralization hosted by dioritic to granitic plutons, which formed at ca. 130 Ma. These intrusive phases were fed by magmas that ponded at mid- to upper-crustal levels and were finally emplaced at < 0.6 kbar based on amphibole geobarometry. The magmas were moderately oxidized (∆NNO − 0.35 to 2.21; with NNO being the nickel–nickel–oxide buffer) and water-rich (mostly > 4 wt. %), and likely experienced a relatively prolonged evolution in the shallow crust rather than at depth. Magma devolatilization and fluid exsolution at shallow-crustal levels lead to decreases in both oxygen fugacity (log ƒO2 − 10.96 to − 14.13) and water content (6.53 to 2.26 wt. %) at < 2.5 kbar pressures. Thermochronological data of zircon and apatite, thermal history modeling, and geological preservation record complex time–temperature histories of the mineralized intrusive rocks, from the cooling of the parent magma itself through burial by younger volcanic rocks to protracted erosion with time. It is estimated that < 2 km of pre-mineralization material was removed from the top of the Naozhi magmatic–hydrothermal system from the Early Cretaceous to present. A 108 ± 2 Ma volcanic event possibly tilted the hydrothermal system, but buried the ores, protecting them from extensive erosion. [ABSTRACT FROM AUTHOR]

The Philippine Mobile Belt is a complex plate boundary with multiple terranes in Southeast Asia, yet its early tectonic evolution is still not fully understood due to a scarcity of solid evidence. Here we report new whole rock geochemical, Sr-Nd isotopic, and zircon U-Pb-Hf isotopic data for Cretaceous-Miocene arc magmatic rocks from the Cebu and Bohol Islands, Philippine Mobile Belt. Bulk geochemical data display arc affinities with enriched large ion lithophile elements (e.g., Sr and Ba) and depleted high field strength elements (e.g., Nb, Ta, and Ti). The high positive εNd(t) (+4.6 to +9.1) values and low initial 87Sr/86Sr ratios (0.7032--0.7048) suggest that these igneous rocks were generated by partial melting of mantle wedge in an arc setting. U-Pb dating of zircons revealed Cretaceous (ca. 120-90 Ma), middle Eocene to early Oligocene (ca. 43-30 Ma), and middle Miocene (ca. 14 Ma) crystallization ages for the arc magmatism with abundant Permian-Triassic zircon xenocrysts clustering at ca. 250 Ma. The Permian-Triassic grains show dominantly negative εHf(t) values ranging from -16.2 to -6.6, which are similar to those of coeval rocks in Eastern Indochina. Combined with previous paleomagnetic studies, we propose that an Eastern Indochina-derived continental fragment was involved during the formation of arcs in the Cebu and Bohol Islands, which highlights the potential contribution of ancient continental materials in the formation of intra-oceanic arcs. This scenario does not support the previously proposed model that the Cretaceous arc in the Philippine Mobile Belt formed in the northern margin of the proto-Philippine Sea Plate and Australian margin. [ABSTRACT FROM AUTHOR]

The reduced nature of the subducting slab has been used to explain the relatively poor endowment of economic porphyry copper deposits in Paleo-Tethyan arc systems. The presence of numerous porphyry Cu deposits in the southern Yidun terrane potentially challenges this model, because these deposits are thought to be the product of Paleo-Tethyan subduction. To investigate this, two representative deposits (i.e., Pulang and Songnuo porphyry Cu deposits) from the southern Yidun terrane have been studied. Zircon U-Pb ages of pre- and syn-mineral porphyries in Pulang are 221 ± 2 Ma (MSWD = 0.89) and 215 ± 2 Ma (MSWD = 1.50), respectively. Zircon and garnet U-Pb ages of the Songnuo syn-mineral porphyry are 217 ± 2 Ma (MSWD = 1.15) and 223 ± 5 Ma (MSWD = 0.97), respectively. The Pulang and Songnuo porphyries both have high whole-rock Sr/Y ratios with minor or no negative Eu anomalies, consistent with derivation from hydrous magmas that underwent minor early plagioclase crystallization but abundant amphibole fractionation. The two porphyry intrusions are characterized by high large-ion-lithophile elements (LILE: Th, U, Ba, Rb) abundances, and low concentrations of high-field-strength elements (HFSE: Nb, Ta, Ti, Zr, Hf). They have similar initial Sr isotope ratios from 0.7055 to 0.7073, ƐNd (t) values from − 4.3 to − 1.6 and zircon ƐHf (t) values of − 1.81 ± 1.34 (n = 47) that are distinct from published results for the Permian–Early Triassic Paleo-Tethyan arc granitoids in the Sanjiang region but similar to the Neoproterozoic arc intrusions in the nearby western Yangtze craton. The Pulang and Songnuo porphyries have relatively high zircon EuN/EuN* ratios (0.59 ± 0.04, n = 52) and calculated Δ log fO2 (FMQ) values (1.61 ± 0.23, n = 52), consistent with relatively oxidized magmas. This feature is similar to the published data for the Neoproterozoic arc intrusions (EuN/EuN* = 0.55 ± 0.08; Δ log fO2 (FMQ) = 2.14 ± 0.60), but distinct from the published data for the reduced normal Paleo-Tethyan arc magmas (EuN/EuN* = 0.29 ± 0.10; Δ log fO2 (FMQ) = − 0.68 ± 0.88). Given that the most recent tectonic reconstruction models suggest that the Paleo-Tethys Ocean closed before ~ 220 Ma, we propose that the Pulang and Songnuo porphyries Cu deposits were formed in a postsubduction setting from oxidized melts generated by reactivating the Neoproterozoic arc root, unrelated to Paleo-Tethyan subduction. [ABSTRACT FROM AUTHOR]

The Late Triassic Guichon Creek batholith is a large (~ 1800 km2), composite, zoned batholith that hosts several large porphyry Cu-Mo deposits of the Highland Valley Copper district. The batholith consists of intrusive rocks that range in composition from gabbro to quartz monzonite. Adjacent to the mafic margin of the batholith is the Gump Lake granodiorite to quartz monzonite stock. A new U-Pb zircon age of 218 ± 0.18 for the Gump Lake stock indicates that magmatism in the region began at least seven million years prior to the emplacement of the main Guichon Creek batholith rocks at 211 Ma. Zircons from fifteen samples from the Guichon Creek batholith were analyzed by laser ablation ICP-MS to characterize the magmatic evolution and ore fertility of the batholith. The trace element composition of zircon record early, lower crustal, fractional crystallization followed by five pulses of magma recharge and mixing in an upper-crustal, oxidized, magma chamber as well as degassing of the magmatic-hydrothermal fluids that formed the porphyry copper deposits. Zircons from the early barren rocks have chondrite-normalized Eu/EuN* values of 0.19 to 0.56 and estimated temperatures of 850 to 750 °C. The middle to late intrusions that host porphyry copper mineralization have zircon Eu/EuN* values of 0.30 to 0.74 and slightly lower estimated temperatures of 800 to 600 °C. Late porphyritic stocks and dikes from the mineralized centers contain zircon crystals elevated in Y, Nb, Ta, and REE concentration relative to zircon from the earlier intrusions. This distinct change in zircon composition coincides with the copper mineralization, suggesting that zircon chemistry can be used as a tool to identify the genetic evolution of a crystallizing magma chamber and potential for mineralization. [ABSTRACT FROM AUTHOR]

In the past decade, significant research efforts have been devoted to mineral chemistry studies to assist porphyry exploration. These activities can be divided into two major fields of research: (1) porphyry indicator minerals (PIMs), which are used to identify the presence of, or potential for, porphyry-style mineralization based on the chemistry of magmatic minerals such as zircon, plagioclase and apatite, or resistate hydrothermal minerals such as magnetite; and (2) porphyry vectoring and fertility tools (PVFTs), which use the chemical compositions of hydrothermal minerals such as epidote, chlorite and alunite to predict the likely direction and distance to mineralized centres, and the potential metal endowment of a mineral district. This new generation of exploration tools has been enabled by advances in and increased access to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), short-wave length infrared (SWIR), visible near-infrared (VNIR) and hyperspectral technologies. PIMs and PVFTs show considerable promise for exploration and are starting to be applied to the diversity of environments that host porphyry and epithermal deposits globally. Industry has consistently supported development of these tools, and in the case of PVFTs encouraged by several successful blind tests where deposit centres have successfully been predicted from distal propylitic settings. Industry adoption is steadily increasing but is restrained by a lack of the necessary analytical equipment and expertise in commercial laboratories, and also by the ongoing reliance on well-established geochemical exploration techniques (e.g. sediment, soil and rock chip sampling) that have aided the discovery of near-surface resources over many decades, but are now proving less effective in the search for deeply buried mineral resources and for those concealed under cover. Thematic collection: This article is part of the Exploration 17 collection available at: https://www.lyellcollection.org/cc/exploration-17 [ABSTRACT FROM AUTHOR]

The central Wasatch Mountains of Utah host a number of mineralized intrusions including the White Pine Fork and Park Premier porphyry deposits. The western stocks of the central Wasatch igneous belt (WIB) include the Clayton Peak, Alta and Little Cottonwood stocks, and the eastern stocks are the Flagstaff, Mayflower, Ontario, Glencoe, Valeo, Pine Creek and Park Premier stocks. New geochronological results comprising zircon LA-ICP-MS 238U-206Pb Concordia intercept ages and molybdenite TIMS 187Re-187Os ages show that the igneous rocks of the central Wasatch Mountains were emplaced in at least two separate events between ~36 to 29 Ma. The oldest phase is associated with the easternmost intrusions, including the Valeo (35.38 ± 0.66 Ma), Flagstaff (35.00 ± 0.64 Ma) and Pine Creek (34.85 ± 0.65 Ma) stocks. The easternmost Park Premier stock has a slightly younger age of 33.69 ± 0.79 Ma. Ignimbritic flows that form part of the Keetley volcanic rocks and igneous clasts found within the Keetley Volcanics are coeval with this phase. A volcanic clast, an ignimbrite, and a flow were sampled separately to yield zircon ages of 35.38 ± 0.66 Ma, 34.9 ± 0.44 Ma, and 34.6 ± 0.39 Ma, respectively. The Clayton Peak stock, which is located in the centre of the suite of stocks, is similar in age to the eastern stocks (34.64 ± 0.73 Ma). The Alta stock, which is located west of the Clayton Peak stock in the central-west part of the district, has a younger crystallization age (32.82 ± 0.65 Ma). The westernmost intrusion, the Little Cottonwood stock, has the youngest crystallization dates (three different samples of the stock yield ages of 29.91 ± 0.56, 29.63 ± 0.52, and 29.45 ± 0.54 Ma). The White Pine intrusion is a late crystallizing phase of the Little Cottonwood Stock. This intrusion hosts Mo mineralization in a breccia with granitic clasts that yield a U-Pb age of 26.61 ± 0.47 Ma. The Mo mineralization in the breccia yields a Re-Os age of 30.21 ± 0.14 Ma with a repeated age of 29.84 ± 0.15 Ma. Duplicate ages (25.30 ± 11 and 28.3 ± 0.13 Ma) were obtained from a second sample of the Mo mineralization. The western stocks (Little Cottonwood, Alta, and Clayton Peak) range in composition from diorite through to granite (53-74 wt% SiO2). The eastern stocks (Flagstaff, Mayflower, Ontario, Park Premier, Pine Creek and Valeo) and Keetley volcanics have a narrower compositional range (59-65 wt% SiO2). All rocks sampled are calc-alkaline in composition. The Clayton Peak stock has the most mafic composition; whereas, the youngest of the western stocks, the Little Cottonwood stock, is the most felsic. This variation in composition is consistent with increasing melt evolution with decreasing age. The igneous stocks have εNd(t) compositions that range from εNd(t) = 12.8 (Alta stock) to εNd(t) = 18.5 (White Pine intrusion). The easternmost samples display the most isotopically-enriched compositions, with fSm/Nd(t) values of -0.58 to 0.56, compared to the rest of the igneous stocks that range from -0.53 to -0.49. The geochemical data suggest a more complex evolution for the porphyry-related intrusions of the WIB than previously recognised. The western stocks evolved to more felsic compositions over time with increased crustal contamination not observed in the eastern stocks. The increased contamination in the western stocks over time suggests that the magmas were ponding at depth and assimilating older crust, consistent with their greater depth of emplacement. Increasing (La/Yb)cn ratios in the youngest and most felsic rocks, which were emplaced during regional crustal thinning, suggest a deeper melt source and identify fertile rocks for porphyry mineralization. [ABSTRACT FROM AUTHOR]

The question of whether the high U and Th concentrations in zircon are primary or secondary is often difficult to resolve, and a clear understanding of the modification processes of secondary U- and Thrich zircon is lacking. Zircon crystals from two well-studied, highly evolved granites, the Jiangjunshan muscovite granite in the Chinese Altai Mountains and the Cuonadong leucogranite in the Eastern Tethyan Himalaya, have been investigated and classified into two types. Type I exhibits typical igneous growth zoning, and type II has "diffuse" or "spongy" internal structures. These textures, along with compositional data, indicate that the type II zircon crystals formed through hydrothermal modification of magmatic zircon (type I) by infiltrating hydrothermal fluids. During hydrothermal modification, the U and Th concentrations increase from type I to type II in the Jiangjunshan muscovite granite but decrease from type I to type II in the Cuonadong leucogranite. The Raman spectra of type II zircon crystals from Jiangjunshan muscovite granite have broader peaks (i.e., measured as the full width at half maximum, FWHM) with decreased intensities than their type I counterparts, which indicates that the former are affected by significant accumulated radiation damage. However, the preserved radiation damage in both the type I and II zircon measured by Raman spectroscopy is less than that expected from the total dose of alpha particles calculated from the U and Th contents, which indicates variable degrees of annealing. We propose that late magmatic-hydrothermal alteration was responsible for the modification of magmatic zircon grains in highly evolved granites and resulted in the enrichment or redistribution of U and Th. The calculated radiation dose of the Cuonadong leucogranite zircon is far below that required for metamictization, which indicates that metamictization is not always responsible for diffuse and spongy textures. [ABSTRACT FROM AUTHOR]

Abstract Two populations of zircons are present in the F-rich highly evolved 300 Ma Shuangji granites, Xinjiang, eastern Tianshan, China. Zircon I comprise a very small proportion of the population. They show characteristics of primary igneous zircons and yield an age of ca. 300 Ma. Zircon II are the dominant type and are weakly luminescent under cathodoluminescence (CL) but show a range of complex textures in back-scattered electron (BSE) images. Zircon II are characterized by Th-U-rich mineral inclusions not seen in zircon I and can be divided into zircon IIa and zircon IIb. Autometasomatism during the magmatic-hydrothermal phase of the highly evolved Shuangji granites, fluids rich in F interacted with zircon I through a coupled dissolution-reprecipitation process forming pores and cracks in the zircon grains. The simultaneous alteration of U-rich euxenite, released high amounts of U and Th into the fluids. Interaction of these fluids with porous zircon I resulted in the precipitation of U- and Th-rich inclusions in the zircon I grains. Radiation damage resulted in the formation of metamict zircons. Later hydrothermal alteration affected the metamict zircons, forming nanoscale baddeleyite in the amorphous zone. Subsequent radiation damage accumulated continuously resulting in the final textures of zircon II. Highlights • Primary and altered zircons can coexist in one granitic system. • Zircons could be hydrothermally altered rather than hydrothermal zircons. • The magmatic-hydrothermal transition could be traced by zircons. [ABSTRACT FROM AUTHOR]

• U-Pb ion microprobe measurements in zircons of 109 new samples. • Definition of two step-wise geochemical shifts in felsic to intermediate intrusions at 2.75 Ga and 2.7 Ga. • A 2.87 Ga xenocryst in the 2.72 Ga phase of the Atikwa batholith, located in the Neoarchean Western Wabigoon terrane, is the earliest isotopic evidence for a Mesoarchean heritage there. • Recognition of linked chemo-stratigraphy across isotopically distinct terranes including ∼2.8 Ga continental emergence in the Jutten and Wagita assemblages of the respective Winnipeg River and Marmion terranes. • Autochthonous development of isotopically distinct terranes of the Wabigoon superterrane. Archaean crustal growth models remain contentious. Isotopically distinct crustal domains in the Superior Craton have been interpreted as exotic terranes, which has bolstered models of Archaean subduction-accretion. However, new geochemistry and geochronology of 3.0-2.7 Ga felsic igneous rocks across the Wabigoon superterrane, Superior Craton, together with a new stratigraphic synthesis, point to a shared chemo-stratigraphy across four isotopically-defined 'terranes'. Uranium-Pb zircon emplacement ages were measured for 109 new samples by ion microprobe. Two chemical shifts were identified across 3.02–2.68 Ga magmatism. At 2.75 Ga, variability in major oxides increases and some LILE, LREE, Sr/Y and La/Lu increase. At ca. 2.69 Ga, sanukitoid-like rocks record an increase in Mg#, compatible and transition elements, P 2 O 5 , LREE and steepening of REE patterns. The 2.75 Ga shift highlights the onset of greater melting/crystallisation depths and changing magma sources, reflecting cratonic thickening. The shift follows ∼2.8 Ga continental emergence recorded in basal conglomerates at a transition from plateau-like to rift- and arc-like greenstone assemblages. The <2.7 Ga shift reflects garnet-stable melting of a metasomatised mantle and correlates with craton-wide sedimentation and orogenesis. Several age peaks in near-continuous Marmion terrane magmatism from 3.02 Ga to 2.78 Ga are contemporaneous with scattered 3.02–2.78 Ga emplacement and inherited zircon ages from the 3.4 Ga Winnipeg River and 2.9 Ga Eastern Wabigoon terranes. All terranes record major magmatic episodes at ca. 2.74-2.72 and 2.7 Ga. A 2.87 Ga zircon xenocryst in the 2.72 Ga Atikwa batholith of the Western Wabigoon terrane is the earliest isotopic evidence for Mesoarchaean basement there. Contemporaneous magmatism, evidence for Mesoarchaean zircon age inheritance in Neoarchaean terranes, and a newly hypothesized time-correlative unconformity across terranes, favours (para-) autochthonous growth of the superterrane. The granite-greenstone record is reconciled by Mesoarchaean rifting, and subsequent development of a Neoarchaean suprasubduction zone before culminating with Kenoran collision. Therefore, <2.78 Ga subduction-accretion overprinted and shortened, but did not necessarily assemble, the Wabigoon superterrane. This finding complements growing global evidence for a unique mechanism of Archaean granite-greenstone development that culminated in late, localized subduction before cratonisation, with implications for the global onset of plate tectonics in the late Archean. [ABSTRACT FROM AUTHOR]

Abstract The Jiaobei Terrane in the southeastern North China Craton (NCC) witnessed intense magmatic pulses during Mesozoic in response to lithospheric thinning. These include sporadic felsic-porphyritic dikes which preserve important information on the magmatic processes and of its implications on lithospheric thinning. Here we present a detailed investigation of representative felsic-porphyritic dikes based on whole-rock geochemical analysis, zircon LA-ICPMS U-Pb geochronology, trace elements and hafnium isotopic compositions. Our results identify stages of felsic dikes in the Jiaobei Terrane with ages in the range of 131–127 Ma and 123–116 Ma. The early stage felsic dikes (ESFDs) have negative zircon ɛ Hf (t) (−22.4 to −11.1), high zircon Eu N /Eu N * (0.41–0.92) and Ce4+/Ce3+ (62–944), low Ti-in-zircon crystallization temperatures (524–738 °C), and are geochemically comparable to the coexisting Guojialing granodiorite. Abundant inherited zircons and scattered zircon Hf, Yb/Gd, Th/U, and Ce/Sm values suggest that the magmas from which the dikes formed involved crustal contamination. They are interpreted to be the hypabyssal phase of the Guojialing suite sourced from the Paleoproterozoic lower crust of the eastern NCC with input of mantle components, associated with extensive crust-mantle interaction during the peak lithospheric thinning. The late stage felsic dikes (LSFDs) are characterized by variable zircon ɛ Hf (t), Eu N /Eu N * and Ce4+/Ce3+ values (−20.1 to −12.2, 0.38–0.88 and 64–956 for the granodiorite- and quartz-porphyritic dikes; −27.6 to −16.2, 0.17–0.75 and 22–503 for the monzogranite-porphyritic dikes), low Ti-in-zircon crystallization temperatures (562 to 774 °C), and display geochemical similarity with the Aishan granitoids. Systematic variations of zircon Hf, Yb/Gd, Th/U and Ce/Sm suggest that fractional crystallization of hornblende played a significant role in the formation of the late dikes. The LSFDs originated from the Neoarchean-Paleoproterozoic lower crust of the NCC with heterogeneous involvement of lesser amounts of mantle materials than the early dikes, consistent with weak crust-mantle interaction during the waning stage of lithospheric thinning. In the LSFDs, the granodiorite and monzogranite porphyries are broadly coeval (123–118 Ma) with large scale gold mineralization in the area as also favored by the high zircon Ce4+/Ce3+ ratios. Our study also provides new insights into the formation of gold deposits. Graphical abstract Unlabelled Image Highlights • Two distinct pulses of Cretaceous felsic dike emplacement in the Jiaobei Terrane • Early stage emplaced at 131-127 Ma with magma sourced from Paleoproterozoic lower crust • Late stage formed at 123-116 Ma with magma source from Neoarchean-Paleoproterozoic crust • High zircon Ce4+/Ce3+ and EuN/Eu N * ratios reflect oxidized conditions with potential to generate metallic mineralization. [ABSTRACT FROM AUTHOR]

There is significant debate regarding the mineralization ages of the East Kounrad, Zhanet and Akshatau W-Mo deposits of Central Kazakhstan, and the petrogenesis and tectono-magmatic evolution of the granites associated with these deposits. To address these issues, we present molybdenite Re-Os dating, zircon U-Pb dating, whole rock geochemistry as well as Sr-Nd-Pb and zircon O-Hf isotopic analyses on the pre-mineralization and ore-forming granites. U-Pb dating of zircons from pre-mineralization granitic rocks yield Late Carboniferous ages of 320–309 Ma, whereas ore-forming granites have Early Permian ages of 298–285 Ma. Molybdenite Re-Os isotopic data indicate a mineralization age of ~ 296 Ma at East Kounrad, ~ 294 Ma at Akshatau and ~ 285 Ma at Zhanet. The pre-ore and ore-forming granites are high-K calc-alkaline, metaluminous to slightly peraluminous I-type granites. The pre-mineralization granites are relatively unfractionated, whereas the ore-forming granites are highly fractionated. The fractionating mineral phases are probably K-feldspar, apatite, Ti-bearing phases and minor plagioclase. The pre-mineralization and ore-forming rocks are characterized by similar Sr-Nd-Pb-Hf-O isotopic compositions (( 87 Sr/ 86 Sr) i = 0.70308–0.70501, ε Nd (t) = − 0.5 to + 2.8, 207 Pb/ 204 Pb = 15.60–15.82, zircon ε Hf (t) = + 1.2 to + 15.6 and δ 18 O = + 4.6 to + 10.3‰), whole rock T DM C (Nd) (840–1120 Ma) and zircon T DM C (Hf) (320–1240 Ma). The isotopic characteristics are consistent with a hybrid magma source caused by 10–30% assimilation of ancient crust by juvenile lower crust. The geochronology and geochemistry of these granites show that the Late Carboniferous pre-mineralization granitic rocks formed during subduction, whereas the Early Permian ore-forming, highly fractionated granite probably underwent significant fractionation with a restite assemblage of K-feldspar, apatite, Ti-bearing phases and minor plagioclase and developed during collision between the Yili and Kazakhstan terranes commenced at the latest Late Carboniferous. [ABSTRACT FROM AUTHOR]

The Paleo-Tethyan arc belt is host to a small number of porphyry Cu deposits the key controls on which remains poorly understood. It has been hypothesized that the Paleo-Tethyan arc magmas were reduced and therefore less fertile for porphyry Cu formation but few studies have been conducted to directly assess the magmatic oxygen fugacity. We investigate the magma fertility of eastern Paleo-Tethyan arc igneous rocks in the Sanjiang region, SW China, represented by the Maoding (268.3 ± 2.3 Ma), Suwalong (275.6 ± 1.4 Ma to 264.7 ± 1.4 Ma) and Baimaxueshan (255.7 ± 1.5 Ma to 249.3 ± 1.1 Ma) granitoids. They have geochemical features consistent with typical continental arc rocks, formed from partial melting of the mantle wedge, with increasing contamination of crust-derived melts over time. The presence of amphibole, high Sr/Y ratios (35 ± 20, n = 17), and lack of negative Eu anomalies (Eu N /Eu N ⁎ = 1.04 ± 0.3, n = 17) are consistent with derivation from hydrous magmas. Zircons from the intrusive rocks have relatively low Eu N /Eu N ⁎ (mostly <0.4) ratios and calculated ΔFMQ values (−2.1 ± 1.2, n = 86). Combined with apatite microphenocrysts with extremely low sulfur contents (< 0.12 wt% SO 3), it suggests that the intrusions originated from water-rich but reduced arc magmas, that were less fertile for porphyry Cu formation. Our study highlights that magmatic f O 2 is probably a critical control on the prospectivity of arc systems and confirms that zircon and apatite compositions can be used to evaluate porphyry Cu fertility. • The Paleo-Tethyan arc igneous rocks were dated from ~275 to 249 Ma. • They were derived from partial melting of mantle wedge during MASH processes. • These arc magmas were reduced and less fertile for porphyry Cu formation. • Zircon and apatite compositions can be used to evaluate porphyry Cu fertility. [ABSTRACT FROM AUTHOR]