Search Results (21)

This study explores the magmatic and hydrothermal evolution of porphyry–skarn–transitional Cu-Mo-W-Au systems within the Nilüfer Mineralization Complex (NMC), located in the westernmost segment of the Eocene Tavşanlı Metallogenic Belt, NW Türkiye. Through integration of field data, whole-rock geochemistry, Re–Os molybdenite dating, and amphibole–biotite mineral chemistry, the petrogenetic controls on mineralization across four spatially associated mineralized regions (Kirazgedik, Güneybudaklar, Kozbudaklar, and Delice) were examined. The earliest and thermally most distinct phase is represented by the Kirazgedik porphyry system, characterized by high temperature (~930 °C), oxidized quartz monzodioritic intrusions emplaced at ~2.7 kbar. Rising fO₂ and volatile enrichment during magma ascent facilitated structurally focused Cu-Mo mineralization. At Güneybudaklar, Re–Os geochronology yields an age of ~49.9 Ma, linking Mo- and W-rich mineralization to a transitional porphyry–skarn environment developed under moderately oxidized (ΔFMQ + 1.8 to +0.5) and hydrous (up to 7 wt.% H₂O) magmatic conditions. Kozbudaklar represents a more reduced, volatile-poor skarn system, leading to Mo-enriched scheelite mineralization typical of late-stage W-skarns. The Delice system, developed at the contact of felsic cupolas and carbonates, records the broadest range of redox and fluid compositions. Mixed oxidized–reduced fluid signatures and intense fluid–rock interaction reflect complex, multistage fluid evolution involving both magmatic and external inputs. Geochemical and mineralogical trends—from increasing silica and Rb to decreasing Sr and V—trace a systematic evolution from mantle-derived to felsic, volatile-rich magmas. Structurally, mineralization is controlled by oblique fault zones that localize magma emplacement and hydrothermal flow. These findings support a unified genetic model in which porphyry and skarn mineralization styles evolved continuously from multiphase magmatic systems during syn-to-post-subduction processes, offering implications for exploration models in the Western Tethyan domain. Full article

The article provides a comprehensive analysis of the Magal Gebreel granitic suites (MGGs) using petrological (fieldwork, petrography, mineral chemistry, and bulk rock analysis) aspects to infer their petrogenesis and emplacement setting. Our understanding of the development of the northern portion of the Arabian Nubian Shield is significantly improved by the Neoproterozoic granitic rocks of the seldom studied MGGs in Egypt’s south Eastern Desert. According to detailed field, mineralogical, and geochemical assessments, they comprise syn-collision (granodiorites) and post-collision (monzogranites, syenogranites, and alkali feldspar rocks). Granodiorite has strong positive Pb, notable negative P, Ti, and Nb anomalies, and is magnesian in composition. They have high content of LREEs (light rare-earth elements) compared to HREEs (heavy rare-earth elements) and clear elevation of LFSEs (low-field strength elements; K Rb, and Ba) compared to HFSEs (high-field strength elements; Zr and Nb), which are in accord with the contents of I-type granites from the Eastern Desert. In this context, the granodiorites are indicative of an early magmatic phase that probably resulted from the partial melting of high K-mafic sources in the subduction zone. Conversely, the post-collision rocks have low contents of Mg#, CaO, P₂O₅, MgO, Fe₂O₃, Sr, and Ti, and high SiO₂, Fe₂O₃/MgO, Nb, Ce, and Ga/Al, suggesting A-type features with ferroan affinity. Their P, Nb, Sr, Ba, and Ti negative anomalies are in accord with the findings for Eastern Desert granites of the A2-type. Furthermore, they exhibit a prominent negative anomaly in Eu and a small elevation of LREEs in relation to HREEs. The oxygen fugacity (fO₂) for the rocks under investigation can be calculated using the biotite chemistry. The narrow Fe/(Fe + Mg) ratio range (0.6–0.75) indicates that they crystallized under moderately oxidizing conditions between ~QFM +0.1 and QFM +1. The A-type rocks were formed by the partial melting of a tonalite source (underplating rocks) in a post-collisional environment during the late period of extension via slab delamination. The lithosphere became somewhat impregnated with particular elements as a result of the interaction between the deeper crust and the upwelling mantle. Full article

The Eastern Carpathians are thrust to the east and north over their Eastern European foreland, tectonically covering it over an area several hundred kilometers across. Information about the nature of the underthrust part of the Carpathian foreland can be obtained from the rock fragments preserved in the sedimentary successions of the Carpathian fold and thrust belt, specifically in the Outer Dacides and the Moldavides. Fragments of felsic rocks occurring within the sedimentary units of the Upper Cretaceous successions of the Moldavides have long been attributed to the Cuman Cordillera—an intrabasinal ridge in the Eastern Outer Carpathians. This work is the first complex geochemical and geochronological study on the exotic igneous clasts of the Cuman Cordillera. Igneous clasts from the southern part of the Moldavides (Variegated clay nappe/formation) are investigated here. They include mainly granites and rhyolites. Phaneritic rocks are composed of cumulus plagioclase, albite, amphibole and biotite, and intercumulus quartz and potassium feldspar, with apatite, magnetite, sphene, and zircon as main accessories, while the porphyritic rocks have a mineral assemblage similar to that mentioned above, displayed in a porphyritic texture with a usually crystallized groundmass. SHRIMP U-Pb zircon dating indicated the 583–597 Ma age interval for magma crystallization. Based on calcareous nannofossils, the depositional age of the investigated igneous clasts is Cenomanian to Maastrichtian, implying that the Cuman Cordillera was an emerged piece of land, herein an active source of sediments in the flysch basin for at least 40 Ma, from the Early Cretaceous (Aptian) to the Late Cretaceous (Maastrichtian). The intrusive and subvolcanic rocks show similar trends for trace and major elements, evincing their comagmatic nature. The enrichment in LILE and LREE relative to HFSE and HREE, as well as the element anomalies (e.g., negative Nb, Ta, and Eu and positive Rb, Ba, K, and Pb) suggest a convergent continental plate margin tectonic setting. Mineral chemistry suggests magma crystallization in relatively oxic conditions (magnetite series), during ascent within a depth of 15 km to 5 km. The igneous rocks attributed to the Cuman ridge display compositional and geochronological features similar to Brno and Thaya batholiths in the Brunovistulian terrane, which could be a piece of the Carpathian foreland not covered by the Tertiary thrusts. Our data confirm the non-Carpathian origin of the igneous clasts, revealing a Neoproterozoic history of the Carpathian foreland units, which include a Cadomian/Pan-African continental arc, exposed mainly during the Late Cretaceous as an intrabasinal island of the Alpine Tethys, traditionally known as the Cuman Cordillera. Full article

The Luanchuan Neoproterozoic gabbroic intrusions are located at the southern margin of the North China Craton (NCC), intruding into the marble and schist from the Nannihu and Meiyaogou Formations of the Neoproterozoic Luanchuan Group. The gabbroic rocks consist of plagioclase (30%–50%) and amphibole (40%–60%), with minor ilmenite (2%–5%), biotite (1%–3%), and titanite (~1%). Based on the occurrence and mineral chemistry, two types of biotites were identified. The first type of biotite (Bt I) is brown, with a fine- to micro-grained anhedral texture, occurring around the magmatic ilmenite and coexisting with titanite. Bt I is characterized by high TiO₂ and FeO contents, with TiO₂ > 2 wt% (2.03 wt%–3.15 wt%) and FeO ranging from 19.94 wt% to 22.08 wt%. The other type of biotite (Bt II) is light grayish-brown to dark reddish-brown, with a medium- to coarse-grained euhedral texture, coexisting with grayish-green amphibole. Bt II exhibits lower TiO₂ (1.40 wt%–1.90 wt%) and FeO contents (18.03 wt%–21.42 wt%). The K₂O (7.56 wt%–9.32 wt%) and SiO₂ (34.49 wt%–37.04 wt%) contents of Bt I are slightly lower than those of Bt II (8.28 wt%–9.73 wt% and 35.18 wt%–37.52 wt%, respectively). Despite the low Ti content in biotites, the mineral occurrence indicates that both types of biotite yield a magmatic origin, resulting from the reactions between early crystallized minerals and residual magma. Bt I originated from the reaction between ilmenite and residual magma, while Bt II resulted from the production of the reaction between clinopyroxne and residual magma. Ilmenite exhibits low MgO and Fe₂O₃ contents but high FeO and MnO contents, suggesting genetic similarities to the Skaergaard and Panzhihua intrusions. Both types of biotites record consistent temperatures (T = 766 to 818 °C), pressures (P = 5.30–8.80 kbar), and oxygen fugacities (log fO₂ = −12.35 to −14.06), aligning with those of the Fanshan complex and the Falcon Island intrusion. The mineralogy of ilmenite and biotite indicates that the Luanchuan gabbroic intrusions formed in a continental rift setting, which is considered to be associated with the breakup of the Rodinia supercontinent. Full article

The Bundelkhand granite (BG) constitutes the bulk of the granitoid complex in the Bundelkhand Craton and preserves imprints of its evolution from the magmatic to a protracted hydrothermal stage as deduced from the petrography. In order to reconstruct such a path of evolution in this study, thermobarometric calculations were attempted on the mineral chemistry of the major (hornblende, plagioclase, biotite) and minor (epidote, apatite) magmatic phases. They yielded magmatic temperatures and pressures (in excess of 700 °C and ~5 kbar), although not consistently, and indicate mid-crustal conditions at the onset of crystallization. Temperatures in the hydrothermal regime within the BG are better constrained by the chemistry of the chlorite and epidote minerals (340 to 160 °C) that conform with the ranges of homogenization temperatures of aqueous–biphase inclusions in matrix quartz in the BG and subordinate quartz veins. These reconstructions indicate that fluid within the BG evolved down to lower temperatures and towards the deposition of quartz and, more importantly, bears a striking similarity to the temperature–salinity characteristics of fluid in the giant quartz reef system. Scanty mixed aqueous–carbonic inclusions in the BG are indicative of the CO₂-poor nature of the BG magma and the exsolution of CO₂ at lower pressure (~2.6 kbar). The dominant mechanism of fluid evolution in the BG appears to be the incursion of meteoric fluid, which caused fluid dilution. Laser Raman microspectrometry reveals many types of solid phases in aqueous–carbonic inclusions in the BG domain. The occurrence of unusual, effervescent-type inclusions, though infrequent, bears a striking similarity to that reported in the giant quartz reef domain. Thus, the highlight of the present work is the convincing fluid inclusion evidence that genetically links the BG with the giant quartz reef system, although many cited discrepancies arise from the radiometric dates. We visualize the episodic release of silica-transporting fluid to the major fracture system (now occupied by the giant reef) from the BG, thus making the fluid in the two domains virtually indistinguishable. Full article

At least three tephra layers, with ages around 2 Ma, crop out in the Pleistocene marine sequence of the Crotone basin, in southern Italy. We present the petrography and the mineral and glass chemistry of these layers, in order to correlate them with other Pleistocene sequences and, possibly, to identify the volcanic source(s). The oldest layer (a1) contains glass shards with homogeneous rhyolitic composition, together with crystals of ortho- and clinopyroxene, plagioclase and amphibole. The age, petrography and major elements’ glass composition allow for correlation with coeval tephra layers cropping out in the southern Apennines, near the town of Craco, in Valle Ricca, near Rome, and in the Periadriatic basin, in central Italy. Two other younger tephras (a3 and a4) can be distinguished by the absence of hydrous phases in a3 and the occurrence of biotite in a4. They show a higher variability in glass composition, which may be related to multiple volcanic sources. A fourth tephra of unknown position, but probably intermediate between a1 and a3, was also recognized. The volcanic source of the tephra layers was identified in a submerged paleo-arc in the central Tyrrhenian Sea, possibly corresponding to the Ventotene ridge. The paper also provides a dataset of glass trace elements’ composition for future correlations. Full article

Fluid infiltration into Proterozoic and Early Palaeozoic dry, orthopyroxene-bearing granitoids and gneisses in Dronning Maud Land, Antarctica, has caused changes to rock appearance, mineralogy, and rock chemistry. The main mineralogical changes are the replacement of orthopyroxene by hornblende and biotite, ilmenite by titanite, and various changes in feldspar structure and composition. Geochemically, these processes resulted in general gains of Si, mostly of Al, and marginally of K and Na but losses of Fe, Mg, Ti, Ca, and P. The isotopic oxygen composition (δ¹⁸O_SMOW = 6.0‰–9.9‰) is in accordance with that of the magmatic precursor, both for the host rock and infiltrating fluid. U-Pb isotopes in zircon of the altered and unaltered syenite to quartz-monzonite indicate a primary crystallization age of 520.2 ± 1.0 Ma, while titanite defines alteration at 485.5 ± 1.4 Ma. Two sets of gneiss samples yield a Rb-Sr age of 517 ± 6 Ma and a Sm-Nd age of 536 ± 23 Ma. The initial Sr and Nd isotopic ratios suggest derivation of the gneisses from a relatively juvenile source but with a very strong metasomatic effect that introduced radiogenic Sr into the system. The granitoid data indicate instead a derivation from Mid-Proterozoic crust, probably with additions of mantle components. Full article

The Kunduleng granite hosts one of several significant uranium anomalies within the southern Great Xing’an Range, NE China. Whole-rock geochemistry and mineral chemistry data, along with the zircon U-Pb-Hf isotope have been used to constrain the petrogenesis of this granitic intrusion and the origin of the uranium anomaly. Microscopically, quartz, alkali-feldspar, and plagioclase are the essential mineral constituents of the granite, with minor biotite, while monazite, apatite, xenotime, and zircon are accessory minerals. Geochemically, the silica- and alkali-rich granites show a highly fractionated character with “seagull-shaped” REE patterns and significant negative anomalies of Ba and Sr, along with low Zr/Hf and Nb/Ta ratios. The granite has positive zircon ε_Hf(t) values ranging from +12.7 to +14.5 and crustal model ages (T_DM2) of 259–376 Ma, indicating a Paleozoic juvenile crustal source. Uraninite and brannerite are the main radioactive minerals responsible for the uranium anomaly within the Kunduleng granite. Uraninite presents well-developed cubic crystals and occurs as tiny inclusions in quartz and K-feldspar with magmatic characteristics (e.g., elevated ThO₂, Y₂O₃, and REE₂O₃ contents and low CaO, FeO, and SiO₂ concentrations). The calculated U-Th-Pb chemical ages (135.4 Ma) are contemporaneous with the U-Pb zircon age (135.4–135.6 Ma) of the granite, indicating a magmatic genesis for uraninite. The granites are highly differentiated, and extreme magmatic fractionation might be the main mechanism for the initial uranium enrichment. Brannerite is relatively less abundant and typically forms crusts on ilmenite and rutile or it cements them, representing the local redistribution and accumulation of uranium. Full article

This paper investigates the monazite grains from the Dibrova rare-earth-thorium-uranium (U-Th-REE) mineral deposit within the Azov Megablock of Ukrainian Shield. U-Th-REE mineralization is associated with K-feldspar-quartz metasandstones and metagritstones (hereafter quartzites) and pegmatoids. The latter possibly represent products of ultrametamorphism/granitization of initially sedimentary clastic rocks during tectono-magmatic activation during the Paleoproterozoic. Ores are composed of quartz as a principal mineral, feldspar, sillimanite, muscovite, monazite, brannerite, uraninite, zircon, rutile, and sulfides. The purpose of this work was to obtain insights into the genesis of the mineral deposit by studying the monazite grains, their chemistry, and ages. Petrographic research work was carried out that included studying/analyzing the monazites from various monazite-bearing rocks (quartzites, pegmatoid, and biotite schist samples). A variety of methods and tools were used, including optical microscopy study, X-ray fluorescence (XRF) mapping of selected samples, as well as scanning electron microscope (SEM) and electron microprobe (EPMA) characterization of monazites, including U-Th-Pb monazite chemical dating. U-Pb-Th chemical electron microprobe dating of the monazites yielded two major distinct monazite age groups at 3.0–2.8 Ga and 2.2–2.0 Ga. The first age group corresponds to the time of formation of the Archean granitoids, which served as a source of monazite for its clastic sedimentation during the Paleoproterozoic in the Dibrova suite sediments. The second age group corresponds to the reprecipitation (i.e., remobilization) of monazite during the Paleoproterozoic tectono-magmatic activation. The location of the mineral deposit within the deep mantle-crustal Devladivska shear zone is another favorable factor for the remobilization and transport of metals. New data on the age of mineralization yield a more complete understanding of the geological history and formation of the complex polyphase rare-earth-uranium-thorium Dibrova mineral deposit. Full article

The Triassic Paleo-Tethyan magmatic belt in the East Kunlun Orogen (EKO) hosts a small number of porphyry-skarn deposits. The controls of these deposits, especially those in the eastern EKO, are poorly understood. In this contribution, we report new petrological, zircon U-Th-Pb-Hf isotopic, whole-rock elemental with Sr-Nd isotopic, and mineral chemistry data of the Delong quartz diorite and mafic enclaves to constrain their petrogenesis and metal fertility. The quartz diorite and mafic enclaves are emplaced in the Late Triassic (ca. 234 Ma). They are medium-K, metaluminous, enriched in large-ion lithophile elements (e.g., Rb, Ba, Th) and light rare earth elements (e.g., La, Ce, Nd), and relatively depleted in high field strength elements (e.g., Nb, Ta, Ti, P) and heavy rare earth elements (e.g., Gd, Er, Tm, Yb). The quartz diorite show similar (⁸⁷Sr/⁸⁶Sr)_i (0.712584~0.713172) and more depleted εNd(t) (−6.4~−5.7) and εHf(t) (−2.3~+2.6) to those of mafic enclaves ((⁸⁷Sr/⁸⁶Sr)_i = 0.712463~0.713093; εNd(t) = −6.4~−6.0; εHf(t) = −9.4~−4.8). Geochemical compositions of zircon, amphibole, and biotite yield high water content (5.3 wt.%~6.9 wt.% and 6.1 wt.%~7.3 wt.% based on amphibole, respectively) and high redox state for both the quartz diorite and mafic enclaves. These data, together with petrography, indicate the Delong intrusion was formed by mingling of magmas from enriched mantle and lower continental crust with juvenile materials. The oxidized and water-rich features of these magmas denote they have potential for porphyry Cu (±Au ± Mo) deposits, as do some Triassic magmatic rocks in the eastern EKO that show similar geochemical and petrographic characteristics with the Delong intrusion. Full article

The Sandaozhuang super-large W-Mo deposit is located in the southern margin of the North China Craton, within the well-known East Qinling Mo mineralization belt, and is one of the typical skarn-type W-Mo deposits in China. Based on EMPA and LA-ICP-MS analyses, major and trace elements were presented, and the mineral chemistry of magnetite at various mineralization stages was discussed. Combining field observations, petrography, and geochemical characteristics, the magnetite at the Sandaozhuang deposit can be classified into three types, namely early-magmatic-stage high-temperature magnetite (Mag1), potassic-alteration-stage magnetite (Mag2), and retrograde-alteration-stage magnetite (Mag3). The Mag1 and Mag2 magnetites primarily occurred in granites in association with potassium (K) feldspar and biotite, whereas Mag3 is associated with metallic sulfide minerals that occurred mainly in vein-like structures in skarn. The three magnetites Mag1, Mag2, and Mag3 can be distinguished as having magmatic, magmatic–hydrothermal transition, and hydrothermal origins, respectively. All three types of magnetite exhibit a depletion of high-field-strength elements (HFSEs) such as Zr, Hf, Nb, Ta, and Ti, and large-ion lithophile elements (LILEs) including Rb, K, Ba, and Sr, compared to the mean continental crust composition. Conversely, they are enriched in elements such as Sn, Mo, V, Cr, Zn, and Ga. Mag3 showed no significant depletion of Co, Ni, Cu, and Bi, indicating that the influence of coexisting sulfides on the composition of magnetite at the Sandaozhuang deposit is limited. There are systematic variations in major and trace elements from Mag1 to Mag3, which exhibited similar patterns in trace element spider and rare earth element diagrams, and Y/Ho ratio, indicating a consistent source for the three types of magnetite. The changes in V and Cr contents and (Ti + V) vs. (Al + Mn) diagram of magnetite at the Sandaozhuang deposit reflected the evolution of ore-forming fluids with an initial increase in oxygen fugacity and a subsequent decrease, as well as a gradual decrease in temperature during skarn mineralization. The early high-temperature and high-oxygen-fugacity magmatic fluids became W and Mo enriched by hydrothermal fluid interaction. The rapid change in fluid properties during the retrograde alteration stage led to the precipitation of scheelite and molybdenite. Full article

The Xiongcun Cu–Au ore district is in the southern middle Gangdese Metallogenic Belt, Tibet, and formed during Neo-Tethyan oceanic subduction. The Xiongcun ore district mainly comprises two deposits, the No. I and No. II deposits, which were formed by two individual mineralization events according to deposit geology and Re–Os isotopic dating of molybdenite. The No. I deposit is similar to a reduced porphyry copper–gold deposit, given the widespread occurrence of primary and/or hydrothermal pyrrhotite and common CH₄-rich and rare N₂-rich fluid inclusions. The No. II deposit, similar to classic oxidized porphyry copper–gold deposits, contains highly oxidized minerals, including magnetite, anhydrite, and hematite. The halogen chemistry of the ore-forming fluid from the No. I and No. II deposits is still unclear. Biotite geochemistry with halogen contents was used to investigate the differences in ore-forming fluid between the No. I and No. II deposits. Hydrothermal biotite from the No. I deposit, usually intergrown with sphalerite, is Mg-rich and classified as phlogopite and Mg-biotite, and hydrothermal biotite from the No. II deposit is classified as Mg-biotite. Hydrothermal biotite from the No. I deposit has significantly higher SiO₂, MnO, MgO, F, Li, Sc, Zn, Rb, Tl, and Pb contents and lower Al₂O₃, FeO_tot, Cl, Ba, Cr, V, Co, Ni, Y, Sr, Zr, Th, and Cu contents than the biotite from the No. II deposit. Hydrothermal biotites from the No. I and No. II deposits yield temperatures ranging from 230 °C to 593 °C and 212 °C to 306 °C, respectively. The calculated oxygen fugacity and fugacity ratios indicate that the hydrothermal fluid of the No. I deposit has a higher F content, oxygen fugacity, and log(fHF/fHCl) value and a lower log(fH₂O/fHF) value than the hydrothermal fluid from the No. II deposit. The biotite geochemistry shows that the No. I and No. II deposits formed from different hydrothermal fluids. The hydrothermal fluid of the No. I deposit was mixed with meteoric waters containing organic matter, resulting in a decrease in oxygen fugacity and more efficient precipitation of gold. The No. I and No. II deposits were formed by a Cl-rich hydrothermal system conducive to transporting Cu and Au. The decreasing Cl, oxygen fugacity, and temperature may be the key factors in Cu and Au precipitation. Biotite geochemistry allows a more detailed evaluation of the halogen chemistry of hydrothermal fluids and their evolution within porphyry Cu systems. Full article

Different ore deposit types may evolve from a common magmatic-hydrothermal system. Establishing a genetic link between different deposit types in an ore cluster can not only deepen the understanding of the magmatic-hydrothermal mineralization process but can also guide exploration. Both the Nihe iron-oxide–apatite (IOA) deposit and the Shaxi porphyry Cu–Au deposit in the Lower Yangtze Valley, Anhui, Southeast China, formed in the Luzong Cretaceous volcanic basin at ~130 Ma. We examined a temporal–spatial and potential genetic link between these deposits based on stratigraphic lithofacies sections, biotite and clinopyroxene mineralogical chemistry, zircon chronology, Hf isotopes, and trace elements. Stratigraphy, petrology, mineralogical chemistry, and available fluid inclusion results support that the emplacement depth of the Nihe ore-related porphyry is shallower than that of the Shaxi porphyry. The magmatic zircon and hydrothermal zircon from Nihe provided U–Pb ages of 130.6 ± 0.7 Ma and 130.7 ± 0.7 Ma, respectively. The magmatic zircon U–Pb age (130.0 ± 0.8 Ma) of Shaxi overlaps with its molybdenite Re–Os age (130.0 ± 1.0 Ma). The agreement between the mineralization and porphyry emplacement ages of Nihe and Shaxi indicates a temporal coincidence and supports a possible genetic link between the two deposits, considering their close spatial relationship (in the same ore district, 15 km). The zircon Hf isotopes and trace elements support the evolution of both deposits from an enriched lithospheric mantle, although the Shaxi deposit may have experienced contamination of the Jiangnan-type basement. Both deposits lie above the fayalite-magnetite-quartz buffer, but the Nihe magmatic zircons are of lower temperature and less oxidized than that of Shaxi. The much higher Eu/Eu* and Yb/Dy values of zircons from Shaxi are likely caused by the suppression of early plagioclase crystallization and the prevalence of amphibole fractionation, thus indicating more hydrous content of the Shaxi ore-related magma. Additionally, the Shaxi ore-related porphyry has higher zircon Hf concentrations, suggesting that the porphyry Cu–Au deposit has experienced a greater degree of magma fractionation. Our study highlights that the Nihe IOA deposit and the Shaxi porphyry Cu–Au deposit have a common magma source, while different extent of crust contamination, magma oxidation state, hydrous content, and degree of magma fractionation collectively result in the two distinct ore deposits. This possible genetic link suggests a great potential of porphyry Cu–Au-PGE mineralization in the Middle–Lower Yangtze River metallogenetic belt, especially in the deep part of the IOA district in the Luzong Cretaceous volcanic basin. Full article

The Sungun Cu-Mo porphyry deposit forms part of the Ahar–Arasbaran Magmatic Belt (AAMB). Its host Miocene porphyry stock is quartz monzonitic in composition and is cut by intermediate dykes that post-date mineralization. These dykes contain pyroxene and enclaves of ambiguous origin. Dykes of microdiorite are observed within quartz diorite dykes, whereas later diorite dykes contain three different kinds of enclaves (diorite, quartz diorite and hornfels) of sizes between 1 and 10 cm. Enclaves consist of plagioclase, hornblende and biotite, with accessory sphene, quartz and apatite. Chlorite compositions in microdiorite are within the chamosite range, whereas they are within the clinochlore range in diorite enclaves. Microprobe analyses of pyroxene indicate an augitic composition (Fs13.38-22.79Wo29.1-33.57En48.53-56.61), consistent with an igneous origin. Hornblende of the diorite enclaves formed at pressures ranging between 3 and 5.3 kilobars and temperatures between 714 and 731 °C. Average oxygen fugacity during rock formation is −14.75. Such high oxygen fugacities suggest that the diorite formed near the boundaries of a convergent margin. Amphibole compositions suggest that the diorite enclaves are sub-alkaline to mildly alkaline, consistent with reported whole-rock chemistry of the Sungun magmas. Pyroxenes were formed at pressures ranging between 11 and 15 kilobars (33–45 km) and temperatures between 1100 and 1400 °C. The amount of Fe³⁺ in clinopyroxene is also consistent with high oxygen fugacity within their environment of crystallization. Overall, these results have implications for our understanding of the origin of the Sungun Cu-Mo porphyry magmas and their mineral deposits in a lower-crustal setting. Full article

Archean supracrustal rocks from the Qingyuan area of the northern Liaoning terrane, the North China Craton, occur as enclaves or rafts of various scales within tonalite–trondhjemite–granodiorite (TTG) domes. They were normally subjected to metamorphism at amphibolite facies with locally granulite facies. We collected biotite two-feldspar gneiss from the Hongtoushan of the Qingyuan area and conducted petrography, mineral chemistry, phase equilibrium modeling and monazite dating to reveal its metamorphic evolution. The peak condition was constrained to be 750–775 °C at ~7 kbar based on the stability of the inferred peak mineral assemblage and mineral compositions including the pyrite and grossular contents in the garnet core, and X_Mg in biotite. The final condition was constrained to be ~700 °C at ~6 kbar on the solidus based on the presence of muscovite in the final assemblage. The post-peak near-isobaric cooling process was consistent with the core→rim decreasing pyrite content in garnet. Monazite dating yielded a metamorphic age of ~2.50 Ga for the sample, coeval with the final magmatism of TTGs in the terrane. By combining other geological features, we suggest a vertical sagduction process to be responsible for the metamorphic evolution of the Qingyuan area. This process may be correlated with Archean mantle plume. Full article