Petrogenesis and Tectonic Setting of Early Cretaceous Intrusive Rocks in the Northern Ulanhot Area, Central and Southern Great Xing’an Range, NE China

Abundant Early Cretaceous magmatism is conserved in the central and southern Great Xing’an Range (GXR) and has significant geodynamic implications for the study of the Late Mesozoic tectonic framework of northeast China. In this study, we provide new high-precision U–Pb zircon geochronology, whole-rock geochemistry, and zircon Hf isotopic data for representative intrusive rocks from the northern part of the Ulanhot area to illustrate the petrogenesis types and magma source of these rocks and evaluate the tectonic setting of the central-southern GXR. Laser ablation inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U–Pb dating showed that magmatism in the Ulanhot area (monzonite porphyry: 128.07 ± 0.62 Ma, quartz monzonite porphyry: 127.47 ± 0.36, quartz porphyry: 124.85 ± 0.34, and granite porphyry: 124.15 ± 0.31 Ma) occurred during the Early Cretaceous. Geochemically, monzonite porphyry belongs to the metaluminous and alkaline series rocks and is characterized by high Al2O3 (average 17.74 wt.%) and TiO2 (average 0.88 wt.%) and low Ni (average 4.63 ppm), Cr (average 6.69 ppm), Mg# (average 31.11), Y (average 15.16 ppm), and Yb (average 1.62 ppm) content with enrichment in Ba, K, Pb, Sr, Zr, and Hf and depletion in Ti, Nb, and Ta. The granitic rocks (e.g., quartz monzonite porphyry, quartz porphyry, and granite porphyry) pertain to the category of high-K calc-alkaline rocks and are characterized by high SiO2 content (>66 wt.%) and low MgO (average 0.69 wt.%), Mg# (average 31.49 ppm), Ni (average 2.78 ppm), and Cr (average 8.10 ppm) content, showing an affinity to I-type granite accompanied by Nb, Ta, P, and Ti depletion and negative Eu anomalies (δEu = 0.57–0.96; average 0.82). The Hf isotopic data suggest that these rocks were the product of the partial melting of juvenile crustal rocks. Notably, fractionation crystallization plays a crucial role in the process of magma emplacement. Combining our study with published ones, we proposed that the Early Cretaceous intrusive rocks in the Ulanhot area were formed in an extensional tectonic background and compactly related to the subduction of the Paleo-Pacific Ocean plate.

Generation of the Giant Porphyry Cu-Au Deposit by Repeated Recharge of Mafic Magmas at Pulang in Eastern Tibet

The giant Pulang porphyry Cu-Au district (446.8 Mt at 0.52% Cu and 0.18 g/t Au) is located in the Yidun arc, eastern Tibet. The district is hosted in an intrusive complex comprising, in order of emplacement, premineralization fine-grained quartz diorite and coarse-grained quartz diorite, intermineralization quartz monzonite, and late-mineralization diorite porphyry, which were all emplaced at ca. 216 ± 2 Ma. Mafic magmatic enclaves are found in both the coarse-grained quartz diorite and quartz monzonite. The well-preserved primary mineral crystals in such a systematic magma series (including contemporaneous relatively mafic intrusions) with well-defined timing provide an excellent opportunity to investigate upper crustal magma reservoir processes, particularly to test the role of mafic magma recharge in porphyry Cu formation. Two groups of amphibole crystals, with different aluminum contents, are observed in these four rocks. Low-Al amphibole crystals (Аl2О3 = 6.2–7.6 wt %) with crystallization temperatures of ~780°C mainly occur in the coarse-grained quartz diorite and quartz monzonite, whereas high-Al amphibole crystals (Al2O3 = 8.0–13.3 wt %) with crystallization temperatures of ~900°C mainly occur in the fine-grained quartz diorite and diorite porphyry. These characteristics, together with detailed petrographic observations and mineral chemistry studies, indicate that the coarse-grained quartz diorite and quartz monzonite probably formed by crystal fractionation in the same felsic magma reservoir, whereas the fine-grained quartz diorite and diorite porphyry formed from relatively mafic magmas sourced from different magma reservoirs. The occurrence of mafic magmatic enclaves, disequilibrium phenocryst textures, and cumulate clots indicates that the coarse-grained quartz diorite and quartz monzonite evolved in an open crustal magma storage system through a combination of crystal fractionation and repeated mafic magma recharge. Mixing with incoming batches of hotter mafic magma is indicated by the appearance of abundant microtextures, such as reverse zoning (Na andesine core with Ca-rich andesine or labradorite rim overgrowth), sharp zoning (Ca-rich andesine or labradorite core with abrupt rimward anorthite decrease) and patchy core (Ca-rich andesine or labradorite and Na andesine patches) textured plagioclase, zoned amphibole, high-Al amphibole clots, skeletal biotite, and quartz ocelli (mantled quartz xenocrysts). Using available partitioning models for apatite crystals from the coarse-grained quartz diorite, quartz monzonite, and diorite porphyry, we estimated absolute magmatic S contents to be 20–100, 25–130, and >650 ppm, respectively. Estimates of absolute magmatic Cl contents for these three rocks are 1,000 ± 600, 1,800 ± 1,100, and 1,300 ± 1,000 ppm, respectively. The slight increase in both magmatic S and Cl contents from the premineralization coarse-grained quartz diorite magma to intermineralization quartz monzonite magma was probably due to repeated recharge of the relatively mafic diorite porphyry magma with higher S but similar Cl contents. Mass balance constraints on Cu, S, and Cl were used to estimate the minimum volume of magma required to form the Pulang porphyry Cu-Au deposit. Magma volume calculated using Cu mass balance constraints implies that a minimum of 21–36 km3 (median of 27 km3) of magma was required to provide the total of 2.3 Mt of Cu at Pulang. This magma volume can explain the Cl endowment of the deposit but is unlikely to supply the sulfur required. Recharge of 5–11 km3 of diorite porphyry magma to the felsic magma reservoir is adequate to account for the additional 6.5–15 Mt of S required at Pulang. Repeated diorite porphyry magma recharge may have supplied significant amounts of S and some Cl and rejuvenated the porphyry system, thus aiding formation of the large, long-lived magma reservoir that produced the porphyry Cu-Au deposit at Pulang.

Rare and Critical Metals in Pyrite, Chalcopyrite, Magnetite, and Titanite from the Vathi Porphyry Cu-Au±Mo Deposit, Northern Greece

The Vathi porphyry Cu-Au±Mo deposit is located in the Kilkis ore district, northern Greece. Hydrothermally altered and mineralized samples of latite and quartz monzonite are enriched with numerous rare and critical metals. The present study focuses on the bulk geochemistry and the mineral chemistry of pyrite, chalcopyrite, magnetite, and titanite. Pyrite and chalcopyrite are the most abundant ore minerals at Vathi and are related to potassic, propylitic, and sericitic hydrothermal alterations (A- and D-veins), as well as to the late-stage epithermal overprint (E-veins). Magnetite and titanite are found mainly in M-type veins and as disseminations in the potassic-calcic alteration of quartz monzonite. Disseminated magnetite is also present in the potassic alteration in latite, which is overprinted by sericitic alteration. Scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and chalcopyrite reveal the presence of pyrrhotite, galena, and Bi-telluride inclusions in pyrite and enrichments of Ag, Co, Sb, Se, and Ti. Chalcopyrite hosts bornite, sphalerite, galena, and Bi-sulfosalt inclusions and is enriched with Ag, In, and Ti. Inclusions of wittichenite, tetradymite, and cuprobismutite reflect enrichments of Te and Bi in the mineralizing fluids. Native gold is related to A- and D-type veins and is found as nano-inclusions in pyrite. Titanite inclusions characterize magnetite, whereas titanite is a major host of Ce, Gd, La, Nd, Sm, Th, and W.

El plutón anorogénico Chinquilchoro del Pérmico medio: un caso de zonación concéntrica normal en su parte meridional, norte de Chile

The southern part of the Mid-Permian Chinquilchoro pluton consits of two approximately concentric lithofacies: an A lithofacies, external melanocratic and a leucocratic internal B lithofacies. The A lithofacies is formed by quartz diorite and quartz monzonite, and the B lithofacies lies in the limit between quartz monzodiorite and quartz monzonite. The contact between the two lithofacies is transitional and difuse. The two lithofacies are calcalkaline, metaluminous and ferric. The coexistence of both lithofacies can be explained by fractional crystallization from the same parental magma in an anorogernic tectonic environment.

Ediacaran initial subduction and Cambrian slab rollback of the Junggar Ocean: New evidence from igneous tectonic blocks and gabbro enclave in Early Palaeozoic accretionary complexes, southern West Junggar, NW China

New zircon U–Pb ages and whole-rock chemical data from four adakitic and two non-adakitic igneous rocks as tectonic blocks in the southern West Junggar accretionary complexes, northwestern China and one gabbro enclave in adakitic block provide further constraints on the initial subduction and following rollback process of the Junggar Ocean as part of southern Palaeo-Asian Ocean. The oldest adakitic monzonite in Tangbale is intruded by the non-adakitic quartz monzonite at 549 Ma, and the youngest adakitic diorite in Tierekehuola formed at 520 Ma. The Ediacaran–Cambrian magmatism show a N-wards younger trend. The high-SiO2 adakitic rocks have high Sr (300–663 ppm) and low Y (6.68–12.2 ppm), with Sr/Y = 40–84 and Mg no. = 46–60, whereas the non-adakitic rocks have high Y (13.2–22.7 ppm) and Yb (2.32–2.92 ppm), with Mg no. = 36–40. The gabbro has high MgO (14.81–15.11 wt%), Co (45–48 ppm), Cr (1120–1360 ppm) and Ni (231–288 ppm), with Mg no. = 72–73. All the samples show similar large-ion lithophile element (LILE) and light rare earth element (LREE) enrichment and Nb, Ta, Ti and varying Zr and Hf depletion, suggesting that they were formed in a subduction-related setting. The adakitic rocks were produced by partial melting of subducted oceanic slab, but the melts were modified by mantle wedge and slab-derived fluids; the non-adakitic rocks were likely derived from partial melts of the middle-lower arc crust; and the gabbro originated from the mantle wedge modified by slab-derived fluids. The magmatism could have been generated during the Ediacaran initial subduction and Cambrian slab rollback of the Junggar Ocean.

The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece

The Vathi porphyry Cu-Au ± Mo mineralization is located in the Serbo-Macedonian metallogenic province of the Western Tethyan Metallogenic Belt. It is mainly hosted by a latite and is genetically associated with a quartz monzonite intrusion, which intruded the basement rocks of the Vertiskos Unit and the latite, 18 to 17 Ma ago. A phreatic breccia crosscuts the latite. The quartz monzonite was affected by potassic alteration, whereas the latite was subjected to local propylitic alteration. Both styles of alteration were subsequently overprinted by intense sericitic alteration. M-type and A-type veins are spatially associated with potassic alteration, whereas D-type veins are related to the sericitic alteration. Three ore assemblages are associated with the porphyry stage: (1) pyrite + chalcopyrite + bornite + molybdenite + magnetite associated with potassic alteration; (2) pyrite + chalcopyrite related to propylitic alteration; and (3) pyrite + chalcopyrite + native gold ± tetradymite associated with sericitic alteration. A fourth assemblage consisting of sphalerite + galena + arsenopyrite + pyrrhotite + pyrite ± stibnite ± tennantite is related to an epithermal overprint. Fluid inclusion data indicate that the A-type veins and related porphyry-style mineralization formed at 390–540 °C and pressures of up to 646 bars (<2.6 km depth) from boiling hydrothermal fluids. A later condensation of vapor-rich inclusions resulted in a moderately saline fluid (8.4–11.2 wt % NaCl equiv) at temperatures between 311 and 392 °C, which were related to sericitic alteration, D-type veins, and associated metallic mineralization. Subsequent dilution of the moderately saline fluid at lower temperatures (205–259 °C) produced a less saline (1.4–2.9 wt % NaCl equiv.) fluid, which is likely associated with the late epithermal overprint.

Petrography and geochemistry of intrusive magmas in Varmaqan – Sardare ghobadi in the west of Iran

The study area is a quadrilateral of 155 km2 between eastern longitude 47˚ and 40 ′ to 47˚ and 52 ′ and northern latitudes 35˚ and 00 ′ to 35˚ and 04 ′ that is located in west of Iran, north of Sonqor city and between Varmaqan and Sardare Ghobadi villages of Kermanshah province. In this range, the intrusive rocks are alkaline granite, granite, granodiorite, tonalite, quartz alkaline syenite, quartz monzonite, quartz monzodiorite, quartz diorite, alkaline syenite, monzonite, diorite, gabbro diorite, gabbro, and olivine gabbro as they were injected in the iron ores of cretaceous which has resulted in contact metamorphism and created hornfels at the site of contact. After comprehensive sampling of all required igneous rocks and according to the thesis objectives, thin sections were prepared and after petrography and some samples were selected for geochemical experiments. XRF analysis, ICP and alkaline fusion were performed on some samples. According to geochemical and petrological studies, the magmas forming these intrusive igneous rocks are from one region and because of magmatic differentiation or fractional crystallization, they from basaltic to acidic terms. Samples of this quadrilateral have a meta-alumina nature and granitoids are in the range of arc islands granites, continental arc granitoids and continental collision granitoids. The mineralogical and chemical composition of the acidic rocks in the area show that the granites in this study are type I.

Rapid Formation of Porphyry and Skarn Copper-Gold Mineralization in a Postsubduction Environment: Re-Os and U-Pb Geochronology of the Ok Tedi Mine, Papua New Guinea

The Ok Tedi copper-gold mine in Western Province, Papua New Guinea, is situated in the western part of the Ok Tedi Complex where monzodiorite to quartz monzonite intrusions are associated with porphyry- and skarn-style copper-gold mineralization. The Pleistocene age of the intrusive rocks and mineralization provides an opportunity to study the longevity of the magmatic and hydrothermal evolution at Ok Tedi through U-Pb dating of zircon and high-precision Re-Os dating of molybdenite. Six main phases of intrusive rocks can be recognized within the mine area, with the sequence of intrusion indicated by contact relationships. Each has been dated by the SHRIMP U-Pb technique with correction for Th-U disequilibrium based on the U and Th content of each sample. In order of intrusion from oldest to youngest these include: Sydney Monzodiorite (1.368 ± 0.045 Ma), Warsaw Monzodiorite (1.269 ± 0.039 Ma), Kalgoorlie Monzodiorite (1.261 ± 0.050 Ma), Ningi Quartz Monzonite Porphyry (QMP)(1.229 ± 0.051 Ma), Bonn Quartz Monzonite (1.219 ± 0.040 Ma), and Fubilan QMP (1.213 ± 0.049 Ma). The intrusions are alkaline, high K to shoshonitic rocks with high Sr/Y ratios typical of Cu-fertile arc magmas. Chondrite-normalized REE patterns have minor or no negative Eu anomalies and downward sloping to listric-shaped HREE patterns typical of arc magmas in which high water contents supress plagioclase fractionation in favor of an evolution by hornblende ± garnet ± titanite fractionation. Cu-Au mineralization at Ok Tedi can be divided into four main stages based on crosscutting relationships: (1) skarn-endoskarn and associated vein-style mineralization in the Darai Limestone, Ieru siltstone, and Sydney Monzodiorite; (2) porphyry-style veins and breccias within the Ningi QMP and older intrusions, and at Siltstone Ridge: (3) porphyry-style veins and breccias in the Fubilan QMP and older intrusions: and (4) skarn-style mineralization in the lower part of the Darai Limestone along the Taranaki thrust. High-precision Re-Os dating of molybdenite has enabled a chronology to be established for the first three stages. Molybdenite from a quartz-mushketovite-epidote-carbonate-pyrite-chalcopyrite-molybdenite vein in clinopyroxene- and garnet-altered Sydney Monzodiorite has an age of 1.3206 ± 0.0020 Ma, and this dates the formation of the Gold Coast and Berlin skarns. Molybdenite from a quartz-pyrite-chalcopyrite-molybdenite vein in the sericite-altered Sydney Monzodiorite yields an age of 1.3166 ± 0.0043 Ma, and a quartz-pyrite-chalcopyrite-molybdenite vein with K-feldspar alteration selvages hosted in Ieru siltstone beneath the Gold Coast skarn has an age of 1.3031 ± 0.0015 Ma. Samples of molybdenite from quartz-sulfide veins from Siltstone Ridge have ages of 1.2116 ± 0.0029 and 1.2078 ± 0.0031 Ma. Molybdenite from a quartz-K-feldspar-pyrite-molybdenite vein, which overprints propylitic alteration in the Sydney Monzodiorite, has an age of 1.2120 ± 0.0024 Ma. These samples date porphyry-style mineralization in and around the Ningi QMP and at Siltstone Ridge. A sample of molybdenite from the matrix of hydrothermal intrusive breccia in the Fubilan QMP has an age of 1.2146 ± 0.0020 Ma, similar to the age of the adjacent Siltstone Ridge mineralization, and is interpreted to have been mechanically incorporated into the breccia during its formation. Several samples have been dated from the Fubilan porphyry system, including molybdenite from the matrix of a hydrothermal intrusive breccia (1.1648 ± 0.0020 Ma) and three samples from veins which postdate the breccias: a vuggy quartz-sulfide vein (1.1532 ± 0.0027 Ma), chalcopyrite-pyrite-molybdenite vein (1.1446 ± 0.0028 Ma), and duplicate analyses of a molybdenite-only vein (1.1326 ± 0.0034 and 1.1297 ± 0.0026 Ma) in agreement at 2σ. Molybdenite from a quartz-K-feldspar-biotite-magnetite-pyrite-chalcopyrite-molybdenite vein in endoskarn-altered Sydney Monzodiorite (beneath the Gold Coast skarn) has an age of 1.1459 ± 0.0012 Ma, and a similar vein without magnetite hosted in Warsaw Monzodiorite has an age of 1.1438 ± 0.0042 Ma, both within error of the chalcopyrite-pyrite-molybdenite vein in Fubilan QMP. Intrusive rocks in the Ok Tedi mine were emplaced over a period of approximately 200,000 years, with Cu-Au mineralization formed in discrete episodes of much shorter duration. The Gold Coast skarn and associated porphyry-style veins in Sydney Monzodiorite and Ieru siltstone formed in 14,000 to 21,000 years (n = 3), the Siltstone Ridge porphyry system in 2,000 to 12,000 years (n = 4), and the Fubilan porphyry system in 31,000 to 40,000 years (n = 6). The Taranaki skarn has not been dated in the mine area due to a lack of molybdenite, but geologic relationships indicate it is younger than the Fubilan QMP.