Syenite Porphyry Research Articles

The superposition of Cretaceous mineralization events leading to the formation of the large Baiyinnuoer Pb–Zn deposit in NE China

The Baiyinnuoer Pb–Zn deposit, estimated at 26.57 million metric tonnes (Mt) with grades of 1.77% Pb and 5.21% Zn, is situated in the southern Great Xing'an Range (SGXR) of northeast China. The deposit comprises southern and northern ore belts. The southern belt primarily contains skarn ore bodies (32% of reserves) associated with Triassic granodiorite, while the northern belt is dominated by skarn ore bodies (30% of reserves) related to Triassic diorite porphyry. In addition to Triassic skarn‐type mineralization, the deposit also exhibits Early Cretaceous mineralization. This includes vein‐type occurrences (36% of reserves) within volcanic tuff and syenite porphyry, alongside a small amount of skarn ore bodies (2% of reserves) related to syenite porphyry. LA‐ICP‐MS U–Pb dating of intrusive rocks and garnets was conducted to investigate the timing and genesis of these mineralization events, revealing two distinct stages of skarn‐type mineralization. The first stage, associated with Early Triassic granitoids, dates to 254.6 ± 1.4–241.7 ± 2.7 Ma, while the second stage is closely associated with Early Cretaceous syenite porphyry, constrained to 135.4 ± 1.1–135.2 ± 1.6 Ma. Garnet U–Pb dating in the syenite porphyry‐related skarn yielded an age of 134.9 ± 4.7 Ma; however, due to low U content, reliable dating of garnets associated with Early Triassic granitoid‐related skarn was not feasible. Micro‐thermometry and Laser Raman analyses of fluid inclusions within vein‐type ore bodies highlighted distinct differences between vein‐type mineralization and Early Triassic skarn‐type mineralization. Additionally, in situ sulfur isotope analyses of sphalerite from both Early Triassic and Early Cretaceous ore bodies indicate a magmatic origin for sulfur in both stages. Through comprehensive geological, geochronological, in situ sulfur isotope and fluid inclusion studies, the Baiyinnuoer Pb–Zn deposit is conclusively identified as a large deposit characterized by two distinct periods of mineralization (Early Triassic and Early Cretaceous), akin to several other significant polymetallic deposits in NE China.

Age, Conditions and Sources of Igneous Rocks of Gora Rudnaya (Southern Yakutia)

The paper presents the results of a complex petrogeochemical and isotope-geochemical (Rb–Sr and Sm–Nd systems) study of alkaline syenites and ore-bearing metasomatites (beresites) of the Gora Rudnaya (Southern Yakutia, Russia), as well as a comparison with compositionally similar massifs of the Aldan Mesozoic igneous province. The Gora Rudnaya, together with the recently discovered Morozkinskoye deposit, is located within the Central Aldan ore region. The massif is composed predominantly of alkaline syenites with a minor amount of alkaline porphyritic syenites, which are intruded by later dikes and sills of alkaline syenite porphyries and calc-alkaline lamprophyres. Industrial gold mineralization is confined to beresitization zones (Qz–Ser– Ank–Py) in areas of intense metasomatic reworking of rocks along steeply dipping fault structures within the intrusion. The obtained Rb–Sr age values for ore-bearing metasomatites (132±1 Ma) indicate subsynchronism of the ore process and crystallization of alkaline syenites, which corresponds to the time of manifestation of the main stage of magmatism in the Aldan Mesozoic igneous province (150–115 Ma). The rocks of the Gora Rudnaya do not differ in petrogeochemical and isotope-geochemical characteristics from rocks of similar composition from other massifs of the Aldan Mesozoic igneous province, indicating a wide lateral distribution of enriched EM I type mantle beneath the studied region. Variations in the initial isotopic composition of neodymium ((143Nd/144Nd) : from 0.511375 to 0.511636) in the studied samples are probably due to the heterogeneity of the source composition. At the same time, the calculated model ages indicate that the enriched mantle source was formed no later than 2.0–2.5 Ga.

Re-melting of the Neoproterozoic juvenile mafic lower crust: The origin of adakitic and non-adakitic felsic suites in the southwest margin of Yangtze Craton

Eocene-Oligocene adakitic and non-adakitic shoshonitic felsic intrusions from the southwest margin of the Yangtze Craton provide a crucial geological record for studying crust-mantle interactions at the craton boundary. Despite their significance, the petrogenesis and source properties of these intrusions remain debated. This study suggests that the adakitic and non-adakitic features of these intrusions result from the re-melting of Neoproterozoic juvenile lower crust, as evidenced by zircon U-Pb dating, geochemical analyses, and petrogenetic investigations. The Ninglang-Yongsheng shoshonitic felsic intrusions, characterized by high Mg#, MgO, Ni, and Cr contents, exhibit isotopic characteristics akin to mantle-derived magma and juvenile mafic lower crust. Their U-Pb ages span 32–36 Ma, and they show similar patterns in major and trace elements, rare earth elements (REEs), and isotopes, with enrichment in large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs) like Nb, Ta, and Ti. These intrusions also demonstrate significant fractionation between light and heavy REEs, with a modest negative Eu anomaly. Their (87Sr/86Sr)i and εNd(t) values range from 0.7060 to 0.7069 and − 4.4 to −1.5, respectively, while Pb isotopic compositions vary slightly.This paper, along with prior research, has developed a genetic model for the Ninglang-Yongsheng shoshonitic felsic intrusions. The adakitic quartz monzonite porphyries likely originated from high-degree partial melting of the juvenile lower crust, whereas the non-adakitic shoshonitic syenite porphyries resulted from lower-degree melting. The composition of the juvenile lower crust may be garnet amphibolite-pyroxenite. This suggests distinct compositional variations within the Ninglang-Yongsheng juvenile lower crust. Moreover, the region's shoshonitic felsic intrusions have assimilated mantle-derived magma. In conclusion, the juvenile lower crust on the Yangtze Craton's southwest margin displays zonal characteristics, with the Liuhe-Beiya area's lower crust showing higher potassium content and more enriched isotopic signatures compared to the Ninglang-Yongsheng region.

Petrogenesis and Tectonic Implications of the Oligocene Dalongtan Shoshonitic Syenite Porphyry in Central Yunnan, Southeastern Tibetan Plateau: Constraints from Geochronology, Geochemistry and Sr-Nd-Hf Isotopes

Shoshonitic rocks are widely distributed in post-collisional settings and provide key information on deep geodynamic mechanisms and magmatic evolution. In this paper, we present petrographic, zircon U-Pb age-related, trace elemental, Hf isotopic, bulk-rock elemental, and Sr-Nd isotopic data of the Dalongtan shoshonitic syenite porphyries (DSSPs) in central Yunnan, southeastern Tibet. The DSSPs formed at 33.2 ± 0.3 Ma in a post-collisional setting. They define linear trends on Harker diagrams, and they display similar trace element patterns and enriched bulk-rock Sr-Nd isotopes [(87Sr/86Sr)i = 0.70964–0.70968, εNd(t) = −12.9 to −12.7] and zircon Hf isotopes (εHf(t) = −15.7 to −13.1) to the coeval mantle-derived potassic mafic rocks. This suggests that the DSSPs were fractionated from the lithospheric mantle-derived mafic magmas. The DSSPs, along with the coeval felsic and mafic magmatic rocks (37.2–32.3 Ma), exhibit a planar distribution on the SE Tibet and predate the left-lateral shearing of the Ailaoshan–Red River shear zone (ARSZ) (32–22 Ma), suggesting that there are no genetic relationships between them. The DSSPs have geochemical characteristics similar to those of A-type granites, with high total alkalinity (10.39–11.17 wt.%), HFSE concentrations (Zr + Nb + Ce + Y = 890.2–1054.3 ppm), Ga/Al ratios (10,000 × Ga/Al = 2.95–3.46), whole-rock zircon saturation temperatures (906–947 °C), and oxygen fugacity (ΔFMQ = +3.30–+4.65), indicating that they are products of the high-temperature melting of the lithosphere as a result of asthenosphere upwelling in extensional settings. Based on our data and regional observations, it is proposed that the generation of the DSSPs may be linked to the convective thinning of the thickened lithospheric mantle following the India–Asia collision.

Differentiation of Lamproitic Magma: Case Study of Mesozoic High-K Dikes of the Ryabinovyi Massif (Central Aldan)

Abstract ––Studies of the mineral–petrographic and geochemical compositions of high-potassic lamprophyric dikes of the Tobuk complex, manifested at the Ryabinovyi plutonic massif (Central Aldan Mesozoic magmatic province, Russia), have shown that these dikes compose a single fractionation series formed from a high-Mg lamproitic parental melt in an intermediate chamber. The composition of the rocks ranges from olivine–diopside–phlogopite and diopside–phlogopite lamproites through minettes to microsyenites and syenite–porphyry. Early crystallization of high-Mg olivine and chromite in an intermediate chamber could produce cumulative dunites similar to those of the Inagli intrusion. Crystallization of olivine and chromite was followed by cotectic crystallization of olivine and clinopyroxene, then that of clinopyroxene and phlogopite, and, finally, eutectic crystallization of Na-rich clinopyroxene, phlogopite, and K-feldspar. Crystallization and gravitational differentiation of lamproitic melt was complicated by silicate–carbonate immiscibility, which is texturally manifested in minettes as carbonate–silicate globules and interstitial calcium and magnesium carbonates. Furthermore, compositional zoning of Sr in apatite and Ba in phlogopite and K-feldspar is considered to have resulted from the immiscibility. Separation of the carbonate–fluorite melt fraction might have led to formation of the carbonatite and fluorite–carbonatite schlieren and gangues which have been described in drill cores from the Ryabinovyi massif. In most of the geochemical and mineralogic features, the Ryabinovyi massif lamproites are similar to the low-Ti lamproites of the Mediterranean postcollisional belt and northern Vietnam and differ from typical high-Ti within-plate lamproites.

Petrogenesis of the Eocene Highly Fractionated Granite Porphyry with REE Tetrad Effect: An Example from Western Yunnan, Southeastern Tibetan Plateau

Highly fractionated granites are widely distributed in the crust and provide unique windows into magmatic evolution. This study reports petrography, zircon U–Pb ages, trace elemental, and Hf isotopic, as well as whole-rock elemental and Nd isotopic data of highly fractionated granite porphyries from the Shiguanshan area in western Yunnan, southeastern Tibet. The granite porphyries were formed at 34.0 ± 0.3 Ma in a post-collisional setting. They are strongly peraluminous (A/CNK = 1.95–2.80), have high SiO2 content (SiO2 = 78.16–79.13 wt.%) and zircon saturation temperatures (803–829 °C, average 819 °C), and low MgO, with pronounced enrichment in Pb, U, Th, and Rb, and depletion in Ti, Eu, P, Sr, and Ba, and belong to highly fractionated A-type granites. These rocks define linear trends on Harker diagrams and display similar enriched whole-rock Nd isotopic (εNd(t) = −12.8 to −12.3) and zircon Hf isotopic (εHf(t) = −10.4 to −8.8) compositions compared to the published data of coeval mantle-derived syenite porphyries, which can be attributed to fractional crystallization processes. A quantitative model suggests that the Shiguanshan granite porphyries likely formed through the fractionation process of a mineral assemblage consisting of plagioclase, K-feldspar, biotite, and amphibole (in a ratio of 40:30:25:5), with fractionation degrees of 50%–55%. The magmatic textures and zircons, decoupling between the REE tetrad effect and fractionation of twin-elements, along with the modeling result of Rayleigh fractionation, suggest that the REE tetrad effect in the Shiguanshan granite porphyries may be caused by fractionation of accessory minerals. Our data, along with regional observations, propose that the generation of these granite porphyries is possibly related to lithospheric removal following the Indo–Asia collision.

Discovery, geological setting and mineralization of the Shuvuutai molybdenum deposit, central-southern Mongolia

We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO2-bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO2-poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids.

Lithology classification of igneous rocks using C-band and L-band dual-polarization SAR data

Abstract Distinguishing different kinds of igneous rocks is difficult because of their subtle differences. Synthetic aperture radar (SAR) is sensitive to rock surface morphology, which can help a lot in classification. Dual-pol SAR data have the advantages of low cost, but few articles are using only dual-pol SAR data for igneous rock classification. In this study, we explored the performance of dual-pol SAR data in distinguishing granitoid, tuff, and syenite porphyry. Backscatter coefficients, polarization decomposition parameters, and texture features from gray-level co-occurrence matrix extracted by Sentinel-1 or PALSAR were classified using several machine learning algorithms. The results are as follows. First, the texture information has greater potential for igneous rock classification, but the polarization decomposition parameters contribute less. Second, after comparing machine learning algorithms, AdaBoost algorithm has the highest overall accuracy for either C-band or L-band SAR data. C-band SAR data provide better classification results than L-band. Finally, tuff is the easiest igneous rock to be successfully classified, and L-band dual-pol SAR data have advantages in the discrimination of syenite porphyry. This study outlines the effectiveness of dual-pol SAR data for igneous rock classification, which will help to select SAR data of appropriate wavelengths for specific types of lithology discrimination.

Late-Permian subduction-to-collision transition and closure of Paleo-Asian Ocean in eastern Central Asian Orogenic Belt: Evidence from borehole cores in the Songliao Basin, Northeast China

The process and timing of the closure of the Paleo-Asian Ocean remain uncertain. The upper Permian Linxi Formation in the Songliao–Xilinhot block provides a key sedimentary record of the closure of the eastern Paleo-Asian Ocean and the associated orogenesis. Here we present a seismic reflection profile and geochronological, paleontological, and geochemical data from 600 m of borehole cores (2022–1394 m depth) from the Songliao Basin to constrain the timing, provenance, and tectonic background of the Linxi Formation. Detrital zircons from the Linxi Formation yield a maximum depositional age of 257.4 ± 4.1 Ma. The formation was intruded by a syenite porphyry dike that crystallized at 245.6 ± 2.7 Ma. Furthermore, the paleontological assemblage indicates an upper Permian stratigraphic age. Borehole samples yield fingerprints of major oxides that are similar to clastic rocks in continental arc basins. Their Rb contents are relatively high (92 ppm on average), Rb/Sr (0.02–2.86) and Th/U (1.12–6.30) ratios are low, and (La/Yb)N and Eu/Eu* ratios are 3.85–8.13 and 0.54–0.98, respectively. These geochemical characteristics indicate a source of continental magma arc. Aided by discrimination diagrams, we propose that the Linxi Formation was deposited within a continental arc or on a continental margin during the closure of the Paleo-Asian Ocean. The Linxi Formation was deposited in a water body that experienced a gradual reduction in salinity, transitioning from a marine environment at the bottom to a transitional marine-terrestrial environment at the top. The water body also became gradually shallower and deposited sediment in the tectonic setting of continental arc. These changes indicate that there was a transition from subduction to collision during the Late Permian.

Geochronology and Geochemistry of Wangjiadashan Quartz Syenite Porphyry in Suizao Area of Hubei Province in the Tongbai-Dabie Orogenic Belt

Geochronology and Geochemistry of Wangjiadashan Quartz Syenite Porphyry in Suizao Area of Hubei Province in the Tongbai-Dabie Orogenic Belt

Cogenetic Origin of Magmatic Enclaves in Peralkaline Felsic Volcanic Rocks from the Sanshui Basin, South China

Centimeter-scale magmatic enclaves are abundant in peralkaline felsic volcanic rocks in the Sanshui Basin. Their lithology is mainly syenite and syenitic porphyry, and they mainly comprise alkali feldspar and amphibole, which is similar to the mineral assemblage of the host trachyte and comendite. The SiO2 content in the syenitic enclaves is ~63 wt%, which is similar to that of the host trachyte but lower than that of the comendite. Thermobarometric calculations showed that the syenitic enclaves crystallized at similar temperature and pressure conditions as their host trachyte. The results of mass-balance modeling and MCS modeling indicate that the syenitic enclaves likely experienced an approximately 74% fractional crystallization from the basaltic parental magma. Combined with the similar mineral assemblages and geochemical characteristics of the host trachyte, we think that the enclaves resulted from the in situ crystallization of trachytic magma in the shallow crust and that they had a cogenetic origin with their host volcanic rocks, which means that they were likely to derived from the identical magma chamber which was formed from different batches of magma mixing/mingling. The recharge and mixing of basaltic magma triggered the eruption of trachytic magma eruption. The syenitic crust may have been disaggregated by the ascending trachytic magma and brought to the surface as syenitic enclaves. The syenitic enclaves in volcanic rocks provide unique information on the magmatism of the shallow crust as evidence of magma mixing/mingling.

Petrogenesis and tectonic significance of Late Mesozoic A-type granite from the Huangmeijian intrusion in the Luzong volcanic basin, eastern China: Constraints from geochronology and geochemistry

The Late Mesozoic A-type granites are widely distributed along eastern China's Lower Yangtze River Belt (LYRB). Much attention has been paid to this region's adakitic rocks and ore deposits, whereas few studies have examined A-type granites. The largest A-type granitic pluton within the Luzong basin, the Huangmeijian (HMJ) intrusion, is composed of quartz syenite, syenogranite, syenite porphyry, and a minor quartz monzonite. Syenite porphyry in the HMJ is divided into fine-grained syenite porphyry (FSP) and coarse-grained syenite porphyry (CSP) with different grain sizes, but studies on syenite porphyry are sparse. In this study, we reported a detailed study including the in situ U–Pb age and trace-element data, whole-rock major and trace elements, apatite compositions, and Sr-Nd isotopes from the HMJ pluton, with aims to further constraints on the petrogenesis, magmatic sources, and evolution, and tectonic significance of A-type granites in the LYRB. These two syenite porphyries (FSP and CSP) in HMJ intrusion were delineated by zircon U–Pb dating with the ages of 126.4 ± 4.4 Ma and 128.9 ± 0.54 Ma respectively. They have geochemical characteristics similar to those of A-type granites, with high total-alkali (10.5–10.7 wt%), HFSEs (Zr + Nb + Ce + Y = 540.4–949.4 ppm), high Ga/Al ratios (10,000 × Ga/Al = 3.88–4.57), and high whole-rock zircon saturation temperatures (832–906 °C) and high oxygen fugacity, classified as A1 type granite. The slightly enriched Sr-Nd isotope composition (87Sr/86Sr = 0.70428–0.71275, εNd(t) = −3.26 to −5.86) of the HMJ apatite with high F and Cl contents, coupled with trace element features, indicating that syenite porphyry was likely originated from metasomatized mantle-derived magma. In addition, two groups of ancient inherited zircons were observed in the FSP, implying the contribution of the old crystalline basement and Paleozoic materials in the magma source. Moreover, significant hostile Eu, Sr, and Ba anomalies and depletion of Sr and Eu in apatite suggest the fractionation of plagioclase, K-feldspar, apatite, and Fe-Ti oxides are also reflected in their elemental variations. Comprehensive discriminant analysis shows that the HMJ syenite porphyries were derived from the metasomatized mantle-derived magma mixing with ancient crustal components in the Paleo-Pacific plate roll-back and intensive lithospheric extension setting, and followed by fractional crystallization.

Oldest syenitic intrusions of the Yilgarn Craton identified at Karari gold deposit, Carosue Dam camp, Western Australia?

Apatite was separated from four samples of syenite porphyry, taken from the Karari gold deposit, in the Kurnalpi Terrane of the Archean Kalgoorlie-Kurnalpi Rift, Eastern Goldfields Superterrane (EGST). The alkalic composition of the syenitic magmas inhibited zircon crystallisation, so apatite provided the best mineral for geochronological investigations. LA-ICP-MS analysis of U, Th and Pb isotopes in the apatite gave a relatively wide range of lower intercept ages, with large errors, ranging from 1 to 3%, using OD-306 apatite as the primary standard. Cathodoluminescent (CL)-darker cores that comprise the major volume of apatite grains are relatively homogeneous in two samples, with one having clear oscillatory zoning. These samples yielded intercept ages of 2701 ± 34 Ma and 2699 ± 25 Ma, respectively. These ages are interpreted to approximate the magmatic crystallisation age of the apatite. Younger intercept ages were generated by apatite from two other samples, which display more complex and heterogeneous patterns of CL brightness. The apatite ages from these two samples are interpreted to have been produced by integrated analysis of apatite that has been heterogeneously modified by younger events. However, the magnitude of the temporal gap between magma emplacement and closure of the U–Pb system in apatite from these two samples remains unknown. Our best estimate of the age of the magmatic apatite from at least two of the syenitic intrusions at Karari is ca 2.70 Ga, which identifies these as the oldest intrusions of the Syenitic Group of magmas yet identified in the EGST. However, if ages are corrected to offset observed in the 401 apatite secondary standard, the two oldest syenitic intrusions are dated at ca 2660 Ma.

Geological, fluid inclusion, and H–O–S–Pb isotopic constraints on the genesis of the Bajiazi mesothermal lode gold deposit in the Jiapigou ore cluster, northeast China

The Bajiazi gold deposit, located in the northeast of the North China Craton, is a typical representative of the Jiapigou ore cluster in northeast China. The deposit is hosted within the Neoarchean–Paleoproterozoic supracrustal rocks (greenstone belts) and metamorphosed plutonic rocks. The orebodies occur along NE-trending ductile–brittle faults as auriferous quartz veins. The mineral assemblages reveal three stages of mineralization: quartz–pyrite (early), quartz–polymetallic sulfide (main), and quartz–carbonate (late). Three types of primary fluid inclusions (FIs), namely A-type (aqueous), C-type (aqueous–carbonic), and PC-type (pure carbonic) FIs, have been distinguished in different stages of quartz. The early- and main-stage quartz grains contain C-, A-, and a few PC-type FIs, while the late-stage quartz grains contain only A-type FIs. The early-, main-, and late-stage FIs homogenized at temperatures of 288–397 °C, 183–281 °C, and 120–190 °C, corresponding to salinities of 8.8–19.5, 3.9–18.8, and 3.2–11.3 wt% NaCl eqv., respectively. The ore fluid system evolved from H2O–NaCl–CO2 to H2O–NaCl during ore formation. The gold precipitation resulted from fluid immiscibility during the main mineralization stage. The HO isotope data reveal that the ore fluids originally came from magmatic water, and mixed with meteoric water during ore formation. The δ34S values (−0.2 ‰ to 8.3 ‰) of ore-related sulfides suggest that the sulfur in the ores was originally magmatic-sourced, and mixed with the sulfur in wall rocks during fluid migration. The Pb isotope ratios (206Pb/204Pb = 15.890–16.794, 207Pb/204Pb = 15.188–15.530, and 208Pb/204Pb = 36.589–37.710) of ore-related sulfides indicate the metals in the ores originated primarily from the lower crust, with a minor mantle contribution, and most likely came from a deep magmatic system. The Late Triassic gold mineralization has a clear genetic link to a quartz syenite porphyry. Based on the geological, FI, and isotopic constraints, the Bajiazi deposit is classified as a mesothermal lode gold deposit, which formed in an extensional setting after the closure of the Paleo-Asian Ocean.

Dating of Variscan magmatism in Kraishte and Balkan Mts

New age determinations by in-situ zircon and titanite LA-ICP-MS analysis for Variscan magmatic activity from Kraishte and Balkan Mts. are reported. The results confirm the presumed Variscan age of the magmatic rocks. For the Sedemte Prestola potassic granitoids, titanite dating reveal an age of 308.7±9.1 Ma. The zircon dating of potassic syenites, cropping out west of Shipka town gave less consistent results – 355±89 Ma. For potassic-alkaline syenite porphyries from the Lutskan pluton, Variscan 206Pb/238U ages cluster in 328–308 Ma interval. Zircons dating of potassic quartzdiorite porphyry from the Lutskan pluton display important inheritance with single 206Pb/238U age of 316 Ma, whereas results of titanite dating range between 350 and 315 Ma, defining poor isochrone of 301±91 Ma and MSWD of 5.6. Zircons from gabbro-diorite porphyries, cutting the Lutskan granitoids plotted on Terra-Wasserburg diagram yield Variscan age of 312±21 Ma and Concordia age of 296±4.6 Ma.

Petrogenesis of Alkaline Complex of the Longbaoshan Rare Earth Element Deposit in the Luxi Block, North China Craton, China

The alkaline complex in the southwest region of Luxi Terrane of the North China Craton is spatially correlated with the newly discovered Longbaoshan REE deposit. Its petrogenesis, however, remains ambiguous. In this study, we present an integrated petrology, whole-rock geochemistry, sphene U-Pb and rare earth element data from the Longbaoshan alkaline complex to investigate the petrogenesis, magma source and tectonic evolution. The Longbaoshan alkaline complex consists of mafic to intermediate rocks of hornblende diorite and alkaline hornblende syenite porphyry, biotite monzonite porphyry and aegirine diorite porphyrite. The hornblende diorites show a composition of low SiO2, high MgO, Fe2O3 and moderate Na2O, CaO and are metaluminous and medium-to-high-K calc-alkaline. The hornblende syenite porphyries, biotite monzonites and argirine diorite porphyrites display a relatively higher content of SiO2, Na2O, K2O and Al2O3 and lower contents of MgO, Fe2O3 and CaO and are metaluminous, peralkaline, high-K calcic-alkaline and shoshonite. The sphene U-Pb data shows that the parent magma of the hornblende diorite was emplaced at ca. 120 Ma. All these samples show a common depletion in Th, Nb-Ta and Zr-Hf and enrichment in large ion lithophile elements (e.g., Pb, Ba, Sr) and Light Rare Earth Elements. The magma may have experienced fractionation of pyroxene, amphibole, sphene, apatite and zircon during its evolution. The variable La content, La/Sm, Rb/Sr and (Ta/Th) N ratios indicate that the parent magma may produce by partial melting of a mantle source that was interacted with sediment-derived melts in a subduction setting. Therefore, we propose that the parent magma of the Longbaoshan alkaline complex was derived from a lithospheric mantle which was metasomatized by sediment-derived melt in a prior subduction process. The enriched magma was emplaced through an extension process and experienced subsequent fractionation and assimilation with the continental crust during the rollback of the Paleo Pacific Ocean plate.

Chronology of Alkaline Magmatism and Gold Mineralization in the Central Aldan Ore District (Southern Yakutia)

Abstract —The Central Aldan ore district (CAOD) is unique by the abundance of gold deposits associated with Mesozoic alkaline magmatism. Four types of gold deposits are established here: porphyry gold, gold–sulfide, gold–argillizite-K-feldspar–quartz, and gold–uranium. The available geochronological data on the age of igneous rocks and gold mineralization in the CAOD show that the latter formed in the period 151–120 Ma. These data also agree with the results of the U–Pb dating of the El’kon gold–uranium ore-magmatic system (143–125 Ma). Analysis of our and earlier published geochronological data showed two stages of magmatism evolution in this region. At the early stage (151–130 Ma), most of the alkali syenites, monzonites, and their analogues (sills, stocks, ring intrusions, and volcanic sequences) and ores formed. They are widespread in various deposits and massifs. In the Ryabinovyi massif, this stage is marked by the formation of most of the alkaline rocks (Aldan Complex) and ores: aegirine syenites, 151.4 ± 1.9 Ma; pyroxene–K-feldspar pegmatites, 144.8 ± 1.5 Ma; and Au–Cu ores, 137.5 ± 1.7—131.1 ± 16 Ma. The crystallization of amphibole in the syenite of the Lunnoe deposit (143.1 ± 2.0 Ma) and in the clinopyroxenite of the Inagli massif (142.4 ± 2.0 Ma) and the formation of most of the alkaline rocks of its ring framing also took place at this stage. At the Samolazovskoe deposit, this stage is marked by the formation of zircon in pseudoleucite syenite, 135.9 ± 1.9 Ma, and in different syenite porphyry phases, 141.39 ± 0.90—142.4 ± 5.0 and 134.25 ± 0.70—129.9 ± 2.6 Ma, as well as gold–skarn mineralization, 129.9 ± 2.6—134.9 ± 2.8 Ma. The same period included the formation of primary ores at the Kuranakh deposit, 136.2 ± 1.7 Ma, and the deposition of brannerite mineralization at the Lunnoe deposit, 132.4 ± 1.6 Ma. Early intrusive phases, such as potassic picrites, shonkinites, and lamprophyres, are scarce among the products of this stage of magmatism, which is possibly due to their burial beneath large volumes of later formed alkali syenites and monzonite–syenites. The second stage (128–120 Ma) was distinguished within the Ryabinovyi massif as small intrusions and dikes of olivine lamproites, shonkinite porphyry, minettes, and syenite porphyry. We revealed explosive breccias with an age of 127 Ma at the Samolazovskoe deposit. Magmatism of this stage was of limited occurrence in the CAOD and did not produce alkali syenites, monzonite–syenites, and ores. At the same time, rocks with an age of 121.1 ± 1.3—115.5 ± 1.6 Ma are widespread in the large (120 km2) Dzheltula ring massif of the Tyrkanda ore district, located east of the Central Aldan region.

Geochronology and Geochemistry of the Mamupu Cu‐Au Polymetallic Deposit, Eastern Tibet: Implications for Eocene Cu Metallogenesis in the Yulong Porphyry Copper Belt

AbstractThe Mamupu skarn‐type Cu‐Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt (YPCB), eastern Tibet. The Cu‐Au mineralization mainly occurs as chalcopyrite in breccia, within the plate‐like carbonate interlayer, being closely related to chloritization (e.g., chlorite, magnetite and epidote) and skarnization (e.g., diopside, tremolite and garnet). The ore‐related quartz syenite porphyry (QSP) and granodiorite porphyry (GP) were emplaced at 40.1 ± 0.2 Ma and 39.9 ± 0.3 Ma, respectively. The QSP of Mamupu is an alkaline‐rich intrusion, relatively enriched in LREE, LILE, depleted in HFSE, with no significant negative Eu and Ce anomalies, slightly high (87Sr/86Sr)i, low ∊Nd(t), uniform (206Pb/204Pb)i and ∊Hf(t) values, which indicates that the porphyry magma may be caused by both the mixing of metasomatized EM II enriched mantle and thickened juvenile lower crust. The QSP in the Mamupu deposit shares a similar genesis of petrology to other ore‐related porphyries within the YPCB. High oxygen fugacity and water content of the magmas are essential for the formation of porphyry and skarn Cu deposits. The QSP has similar high magmatic oxidation states and water content to the Yulong deposit, which indicates that the Mamupu has a high prospecting potential. Differences in the geological characteristics and scale of mineralization between the Mamupu and other YPCB deposits may be due to the different emplacement depths of ore‐related intrusions, as well as differences in the surrounding rocks.

A comprehensive overview on the origin of intrusive rocks and polymetallic mineralization in the Tongling ore-cluster region, lower Yangtze River Metallogenic Belt: Geological and geochemical constraints

The Tongling ore-cluster region is one of the most important Cu-Au polymetallic producers in the famous Lower Yangtze River Metallogenic Belt (LYRMB) in eastern China. The Cu-Au polymetallic ore deposits can be divided into four types, i.e., skarn, strata-bound hydrothermal, porphyry, and cryptobreccia, closely related to the Late Jurassic to Early Cretaceous magmatism. We summarize the geology of the Mesozoic Cu-Au deposits in Tongling, eastern China, and revisit the age distributions and geochemical characteristics of associated Mesozoic intrusions, by integrating a large number of published geochemical data (including major and trace elements for both early-stage and late-stage intrusions, whole-rock Sr-Nd-Pb isotopes, and zircon U-Pb age and Hf isotopes for early-stage intrusions), to reveal their sources and genesis.According to the U-Pb ages of intrusions, the main magmatic events in the area can be divided into two stages, i.e., 152–135 Ma and 135–124 Ma, respectively. The early-stage magmatism mainly produced Cu-Au mineralization-related dioritic intrusions, including pyroxene diorite-pyroxene monzodiorite, quartz diorite-quartz monzodiorite, and granodiorite, showing unobvious geochronological order. Geochemical data of Late Jurassic-Early Cretaceous intrusions from the early-stage magmatism suggest that they are all derived from a similar source composed of different proportions of slab-derived melt, metasomatized lithospheric mantle, and a lesser content of lower crust materials. Among them, the key differences lie in that more lower crust materials are incorporated in the source of intermediate-felsic rocks compared to intermediate-basic rocks. The late-stage magmatism produced a wide variety of rocks (diorite porphyry, syenite porphyry, granite porphyry, monzonite, and granite porphyry), which are related to Pb-Zn deposits. The late-stage igneous rocks may evolve from the early-stage rocks and have experienced fractional crystallization of apatite, ilmenite, and other minerals. Both early and late-stage magmatic events in the Tongling region were formed in the subduction setting, and corresponding to compression and extensional setting, respectively.Besides, the H-O isotopes of different kinds of minerals suggest that the ore-forming fluids of most ore deposits were mainly derived from the magma and mixed with a small amount of meteoric water in the late-stage mineralization. The S isotopes of sulfides show that the ore-forming materials come from the magma, accompanied by the addition of original sediments.

The Changshagou gold deposit, Eastern Tianshan, NW China: orogenic gold mineralization overprinting a porphyry gold occurrence

Abstract The temporal–spatial relationships of porphyry and orogenic gold mineralization in the Eastern Tianshan Orogenic Belt are ambiguous. The newly discovered Changshagou deposit in this belt contains both porphyry and orogenic gold mineralization, which are characterized by polymetallic–sulfide veinlets and quartz–pyrite veins, respectively. Fluid inclusions in the porphyry mineralization episode were trapped at 290–340°C with salinities of 3.0–8.0 wt% NaCl equiv . The homogenization temperatures and salinities in the orogenic mineralization episode range from 240 to 300°C and from 1.0 to 5.0 wt% NaCl equiv . Coexisting V- and L-type fluid inclusions with similar homogenization temperatures are indicative of fluid immiscibility. The δ 18 O w and δ D w values are in the ranges 7.6–9.1 and −70.9 to −84.0‰ in the porphyry mineralization episode, and 6.4–7.1 and −65.7 to −72.1‰ in the orogenic mineralization episode, overlapping magmatic and metamorphic ranges, respectively. The pyrite δ 34 S values range from 3.5 to 4.9‰, falling into the magmatic range. Pyrite in porphyry and orogenic mineralization episodes yield Re–Os isotope ages of 269.1 ± 2.9 and 257.4 ± 2.4 Ma. The porphyry and orogenic gold mineralizations are genetically associated with the quartz syenite porphyry and Kanggur strike-slip shear activity, respectively.