The Shuangjianzishan vein-type Ag-Pb-Zn deposit in the southern Great Xing’an Range (GXR), NE China, is hosted in the slate of the Lower Permian Dashizhai Formation intruded by granite porphyry. In ...this paper, U–Pb zircon ages and bulk-rock and isotope (Sr, Nd, Pb and Hf) compositions are reported to investigate the derivation, evolution and geodynamic setting of this granite porphyry. It is closely associated with Pb-Zn-Ag mineralization in the southern GXR and contains important geological information relating to regional tectonic evolution. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) zircon U–Pb dating yields an emplacement age of 131 ± 1 Ma for the granite porphyry. Bulk-rock analyses show that the Shuangjianzishan granite porphyry is characterized by high Si, Na and K contents but low Mg and Fe contents, and that the enrichment of Zr, Y and Ga suggests an A-type granite affinity. Most of the studied samples have relatively low 87Sr/86Sr values (0.70549–0.70558), with positive ϵNd(t) (0.71–0.88) and ϵHf(t) (4.9–6.9) values. The Sr–Nd isotope modelling results, in combination with the young TDM2 ages of Nd and Hf (850–864 and 668–778 Ma, respectively), reveal that the Shuangjianzishan granite porphyry may be derived from the melting of mantle-derived juvenile component, with minor lower crustal components; this finding is also supported by Pb isotopic compositions. Considering the widespread presence of granitoids with coeval volcanic rocks and regional geology data, we propose that the Shuangjianzishan granite porphyry formed in a post-orogenic extensional environment related to the upwelling of asthenospheric mantle following the closure of the Mongol–Okhotsk Ocean.
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•The parental magma is high temperature, high-Mg content and oxidized.•Three stages of sulfide segregation have been identified.•Assimilation of siliceous rocks was the major factor ...for sulfide segregation.•The Beishan area is still a favorable target for Ni prospecting.
In recent decades, new breakthroughs in Ni prospecting have been made in the Beishan area, southern Central Asian Orogenic Belt, NW China—more vein-type sulfide mineralization with high Ni tenor has been discovered. Here, novel discussions on the petrogenesis and sulfide immiscibility of the Permian mafic–ultramafic rock are presented based on petrological, geochronological, mineralogical, and Hf–S isotopic studies of the newly discovered Hongnieshan Ni occurrence. The complex is predominantly composed of dunite, wehrlite, olivine clinopyroxenite, olivine gabbro, gabbro and norite. The gabbro has a zircon age of 282.9 Ma and positive εHf(t) values (+5.5–+7.8). The complex may have originated from partial melting of the depleted mantle, which was metasomatized by subduction fluid in a post-orogenic extensional setting. The parental magma is characterized by high temperature (1396 ℃) and high Mg (picritic affinity, 14.4 wt% MgO) and Ti (2.3 wt%) contents, and an oxidized nature (FMQ + 0.59). The disseminated and vein-type sulfide mineralization are the results of multistage segregation. The first segregation was induced by the assimilation of Archean strata, as indicated by the presence of Δ33S of sulfide minerals (1.4‰ to 3.6‰), which is within the range of Archean crust (-2.5‰–+11‰) and is clearly beyond the range of post-Archean rocks (0 ± 0.1‰). The sulfide was removed at depth, leading to that the later segregated sulfide was poor in platinum group element. Vein-type high Ni tenor mineralization was ascribed to the second segregation before olivine crystallization and later injection of sulfide ore pulp. The third sulfide segregation was accompanied by fractional crystallization and gave rise to disseminated mineralization with a low Ni tenor. The δ34S in the Beishan Ni-Cu deposits ranges from-2.01 to 2.07‰, exhibiting a mantle-like variation and arguing against the incorporation of crustal S. Crustal assimilation, especially the addition of Si-rich components from country rocks is the main trigger factor. The Beishan area is still a favorable exploration target in future prospecting.
The geochronological data precisely defined the mineralization age of the Haobugao deposit (Fig. 3a–c); The discriminant diagram identifies the dynamic background of the Early Cretaceous diagenesis ...and mineralization (Fig. 3d); Combined with the regional mineralization event, a compilation of existing data reveals that skarn Fe-Sn-Zn-Pb polymetallic mineralization from the Haobugao and other areas along the Southern Great Xing’an Range metallogenic belt took place coevally in the Early Cretaceous and was related to a post-collisional extensional environment.
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•Geochronological data precisely date the magmatism and mineralization.•A-type granite formed under a post-orogenic extensional setting.•Identify an A-type granite-related Fe-Sn-Zn-Pb belt in the SGXR.
The Haobugao skarn Fe-Zn polymetallic deposit is located in the Southern Great Xing’an Range, northeastern China, and hosted in the Lower Permian carbonates. Laser ablation inductively coupled plasma mass spectrometer zircon U-Pb dating constrains the crystallization of the granite and feldspar-phyric diorite at 139 ± 2 Ma and 134 ± 2 Ma, respectively. According to the geological investigation, the Haobugao ore bodies are cut by the feldspar-phyric diorite emplaced along the post-mineralization fault, indicating that the mineralization occurred between 134 Ma and 139 Ma. Five molybdenite samples from skarn-type ores yield a Re-Os isochron age of 138 ± 3 Ma, agree with the crystallization age of the granite, indicating the Early Cretaceous magmatism and mineralization events. The enrichment of Zr, Y and Ga in the Haobugao granite suggest its A-type granite affinity. The positive εNd(t) values, young TDM2 ages and low initial 87Sr/86Sr values for the granite potentially reveal significant amount of juvenile material contributing to the parental magma. Based on Sr-Nd isotopic two-component mixing model, the Haobugao A-type granite was derived by magma mixing between mantle-derived juvenile component (∼80%) and the lower crust component (∼20%), also supported by the Pb isotopic compositions. The geochemical and isotopic signatures indicate that the Haobugao granite are derived from a post-collisional extensional setting. A high oxidation state between Ni-NiO and Fe2O3-Fe3O4 buffer could be predicted by the assemblage of quartz-magnetite-titanite-amphibole-biotite in the granite. Hence, sulfur would have been present as sulfates (SO2-4) in such highly oxidized magmas, and the chalcophile elements (Zn, Pb, Cu, Mo) were retained as incompatible elements in the melt, facilitating subsequent mineralization. A compilation of existing data reveals that the skarn Fe-Zn polymetallic mineralization from the Haobugao and other areas along the Southern Great Xing’an Range metallogenic belt took place coevally in the Early Cretaceous and was related to a post-collisional extensional environment. This significantly differs from the typical porphyry-skarn related deposits that are commonly formed under the arc-compressive setting (e.g., the Pacific Rim).
Schematic illustration showing the genetic model for the Huangtupo-Huangtan deposit.
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•Ore-forming fluids are mainly composed of magmatic water mixed with seawater.•Sulfide ...precipitation is mainly controlled by the rapid temperature drop and pH rise.•The Huangtan and Huangtupo deposits constitute a unique VMS metallogenic system.
The newly discovered Huangtan Au-Cu deposit is located in the central Dananhu - Tousuquan arc of Eastern Tianshan, southern Central Asian Orogenic Belt (CAOB). It is the first Au-dominated volcanogenic massive sulfide (VMS) polymetallic deposit in the Eastern Tianshan. Veinlet-disseminated and massive orebodies are hosted within Early Silurian pyritic phyllic tuff and volcanic breccia and controlled by a secondary fracture zone of the Kalatag fault with extensive hydrothermal alteration. Four primary alteration/mineralization stages have been recognized as follows: (1) Early ore stage (S1), forming mainly ore-barren fine quartz veins with minor gold-bearing sulfides; (2) main ore stage (S2), forming mainly thick quartz veins with abundant coarse-grained subhedral pyrite (S2-1), and plentiful chalcopyrite, sphalerite, barite and Au-bearing sulfide veins (S2-2); (3) late ore stage (S3), which is characterized by plenty of barren quartz–calcite veins with few sulfides; and (4) supergene stage (S4), accompanied by abundant oxide mineralization, including malachite, jarosite and other supergene minerals. From S1 to S3, microthermometric data of fluid inclusions show homogenization temperatures of 263–379 °C (mean = 308 °C), 188-292 °C (mean = 240 °C), and 118-198 °C (mean = 158 °C), respectively, and salinities of 5.3–14.2 (mean = 10.8) wt.% NaCl equiv., 2.8–10.7 (mean = 7.6) wt.% NaCl equiv., and 0.3–14.1 (mean = 2.6) wt.% NaCl equiv., respectively. The ore-forming fluids are characterized by middle-low temperature, low salinity, relatively reduced condition, and an H2O-NaCl ± CO2 ± CH4 system.
The δ34S values (−5.25‰ to 0.50‰) and Pb isotopic ratios (206Pb/204Pb = 17.868–19.495, 207Pb/204Pb = 15.446–15.575, and 208Pb/204Pb = 37.350–38.491) suggest that the ore-forming materials came predominantly from a deep-seated magma source with a minor contribution of lower continental crust. The δ18OH2O and δDV-SMOW values of fluid inclusions in each metallogenic stage range from −6.1 to 5.6‰ and −66.8 to −53.9‰, respectively, suggesting the dominant role of magmatic water mixed with convectively circulating heated seawater during fluid evolution. Fluid cooling dilution, local boiling, and fluid mixing were considered as the main mechanisms of metal precipitation. The 40Ar-39Ar plateau age of hydrothermal muscovite from the late ore stage (S3) is 414.4 ± 0.4 Ma, which represents the upper limit age of shallow hydrothermal alteration and Au-Cu mineralization. It is also consistent with the Early Silurian polymetallic metallogenic event in the Kalatag district. The auriferous Huangtan and adjacent Cu-Zn-rich Huangtupo VMS deposits show obvious ore-forming element differences, and constitute a unique VMS metallogenic system in the Eastern Tianshan Orogenic Belt (ETOB), which provides an important research object and new insight for ore prospecting in the peripheral Gobi Desert area.
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•Two stages of sulfide segregation have been recognized.•The parental magma is PGE-depleted due to early segregation at depth.•Model of “early segregation at depth + later segregation ...in situ + multistage pulsation”.
A series of early Permian mafic–ultramafic complexes associated with Ni-Cu mineralization are distributed in western Beishan region, Xinjiang, NW China. The Ni mineralization in this area consists of two sub-belts, which have the same magma conduit at depth, similar rock types and similar emplacement ages, but different mineralization types. The Ni mineralization in the north (Hongshishan) sub-belt consists of low-tenor disseminated sulfide, whereas that in the south (Pobei) sub-belt consists of disseminated sulfide and vein-type sulfide with high tenor, suggesting different sulfide segregation mechanisms. The Hongshishan complex consists of dunite, wehrlite, olivine clinopyroxenite, troctolite, olivine gabbro, and gabbro (from earlier to later). The mafic rocks occur along margins of the complex, and the mineralized ultramafic rocks are confined to the center. The dunite and wehrlite host significant amounts of disseminated sulfide. The parental magma of the Hongshishan complex may have originated from 17.0% partial melting of the depleted mantle. It is characterized by high temperature (1368 ℃), high Mg (picritic affinity, 14.52 wt% MgO), oxidation and platinum group element (PGE) depletion, as constrained by the major and trace elements, olivine and chromite mineralogy, and PGE contents. Two stages of sulfide segregation have been recognized. Early sulfide segregation at depth, which is indicated by elevated Cu/Pd ratios and sulfide inclusions in chromite, produces the PGE-depleted parental magma. Later in situ segregation results in disseminated sulfide mineralization. Model of the olivine crystallization and PGE content shows that 0.01%−0.015% of the sulfide is segregated in situ, with R = 100–500. Significant crustal contamination is suggested by xenoliths of wall rock as well as negative Nb, Ta, and Ti anomalies and positive Pb and Sr anomalies in intrusive rocks. The addition of crustal Si and decrease in FeO by fractional crystallization are the main factors triggering S-oversaturation and later in situ segregation. The early segregation at depth is more likely caused by the addition of crustal S, although the δ34S values of sulfides (-0.75‰ to 1.15‰) indicate the isotopic signature of mantle sulfur. For comparison, the development of vein-type sulfide mineralization in the Poyi deposit is ascribed to assimilation of S-bearing Archean rocks. Finally, a model of “early segregation at depth + later in situ segregation + multistage pulsation” is proposed for the Ni mineralization in this area.
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•Hydrothermal pyrite grains in this deposit are classified into two types.•Sulfur isotope data suggest derivation from a magmatic source.•The most of the pyrite plots below the gold ...saturation line.
The Haweit gold deposit is located in the Neoproterozoic Hamisana Shear Zone in the Red Sea Hills of NE Sudan. In this study, we use major and trace element chemistry of pyrite, SEM studies, as well as the sulfur isotope composition of pyrite from the deposit to characterize the mineralization, origin of the ore-forming fluids and to constrain the ore-forming processes. Mineralization was controlled by NE- and NW-trending faults, which host many gold-bearing quartz veins in the Neoproterozoic andesitic and granitic country rocks. Fluids and melts associated with the quartz veins produced extensive zones of wall-rock alteration a few centimeters to several meters in thickness. The associated hydrothermal alteration is characterized by sericitization, carbonatization, silicification and pyritization. The Au mineralization is closely associated with the alteration zones, in which two generations of hydrothermal pyrite were identified on the basis of morphology; Py1 consisting of anhedral, elongate or spongy grains and Py2 consisting of medium- to coarse-grained, anhedral to subhedral crystals. Py1 is characterized by slighty lower concentrations of Au, whereas Py2 has slightly higher amounts of Au, As, and Zn. Arsenic, Co, Ni and Cu vary in concentration between the two types of pyrite as shown by their Co/Ni ratios ranging from 0.02 to 57 (average 13.5 ppm) in Py1 and from 0.04 to 165 (average 23.4 ppm) in Py2, indicating growth from magmatic-hydrothermal fluids. The δ34S values of the two types of pyrite are similar, ranging from −3.3 to 3.4‰, with an average value of −0.7%, suggesting a common, magmatic source for the sulfur. All available data point to a hydrothermal-magmatic source for the Haweit gold deposit.
The widely distributed granitic intrusions in the Nubian Shield can provide comprehensive data for understanding its crustal evolution. We present new bulk-rock geochemistry and isotopic (zircon U-Pb ...and Lu-Hf) data from the Haweit granodiorites in the Gabgaba Terrane (NE Sudan). The dated zircons presented a 206Pb/238U Concordia age of 718.5 ± 2.2 Ma, indicating that they crystallized during the Cryogenian. The granodiorites contain both biotite and amphibole as the main mafic constituents. The samples exhibit metaluminous (A/CNK = 0.84–0.94) and calc-alkaline signatures. Their mineralogical composition and remarkable low P2O5, Zr, Ce, and Nb concentrations confirm that they belong to I-type granites. They exhibit subduction-related magma geochemical characters such as enrichment in LILEs and LREEs and depletion in HFSEs and HREEs, with a low (La/Yb)N ratio (3.0–5.9) and apparent negative Nb anomaly. The positive Hf(t) values (+7.34 to +11.21) and young crustal model age (TDMC = 734–985 Ma) indicates a juvenile composition of the granodiorites. The data suggest that the Haweit granodiorites may have formed from partially melting a juvenile low-K mafic source. During subduction, the ascending asthenosphere melts might heat and partially melt the pre-existing lower crust mafic materials to generate the Haweit granodiorites in the middle segment of the Nubian Shield.
The Bianjiadayuan Pb–Zn–Ag deposit in the Southern Great Xing'an Range consists of quartz-sulfide vein-type and breccia-type mineralization related to granite. Vein orebodies are localized in ...NW-trending extensional faults. Hydrothermal alteration is well developed and includes silicification, potassic alteration, chloritization and sericitization. Three stages of mineralization are recognized based on field evidence and petrographic observation and are marked by assemblages of quartz–arsenopyrite–pyrite (stage I), quartz–pyrrhotite–chalcopyrite–sphalerite (stage II) and quartz–galena–silver minerals (stage III). The granite, with a zircon age of 143.2±1.5Ma (n=14, MSWD=0.93), is subalkaline, peraluminous and is classified as A2-type granite originating in a post-orogenic extensional setting during the opening of suture zone between the North China Craton and the Siberia Craton from the Late Jurassic to the Early Cretaceous. The δ34SCDT values of sulfides, ranging from 3.19 to 10.65‰, are not consistent with the majority of magmatic hydrothermal deposits in the SGXR, possibly implying accessory source in addition to magmatic source. Microthermometric measurements show that ore minerals were deposited at intermediate temperatures (347.8–136.4°C) with moderate salinities (2.9–14.4wt.% NaCl). Ore-forming fluids were derived largely from magmatic hydrothermal processes, with the addition of meteoric water in late stage. Successive precipitation of Pb, Zn and Ag occurred with changes of physicochemical conditions. Overall considering mineralization features, ore-forming fluids and materials and tectonic setting and comparing with adjacent deposits, the Bianjiadayuan deposit is a mesothermal magmatic hydrothermal vein-type Pb–Zn–Ag deposit controlled by fractures and related to A2-type granite in response to the tectonic/magmatic/hydrothermal activity in late Jurassic. Besides, the explosive breccias in the west area require more attention in future exploration.
•The Bianjiadayuan deposit consists of vein-type and crypto-explosive breccias type mineralization.•The ore-related granite is A2-type granite in an post-orogenic extensional setting.•The sulfur and ore-forming fluid have accessory source besides magmatic source.
The early Paleozoic is a crucial period in the formation and evolution of the Eastern Kunlun Orogenic Belt (EKOB), and is of great significance for understanding the evolutionary history of the ...Proto-Tethyan Ocean. This paper presents new petrography, geochemistry, zircon U–Pb dating, and Lu–Hf isotopic research on the Yuejingshan gabbro from the eastern segment of the EKOB. Zircon U–Pb data suggests that the gabbro formed in the Early Silurian (435 ± 2 Ma). All samples have relatively low TiO2 contents (0.45–2.97%), widely varying MgO (6.58–8.41%) and Mg# (58–65) contents, and are rich in large ion lithophile elements (LILE such as Rb, Ba, Th, and U) and light rare earth elements (LREE). This indicates that it has a similar geochemical composition to island arc basalt. The major element features indicate that the formation of this gabbro underwent fractional crystallization of clinopyroxene, olivine, and plagioclase. The depletion of high field strength elements (HFSE, such as Nb, Ta, and Ti), and a slightly positive Hf isotope (with εHf(t) ranging from 1.13 to 2.45) may be related to the partial melting of spinel-bearing peridotite, led by slab fluid metasomatism. The gabbro likely represents magmatic records of the latest period of the early Paleozoic oceanic crust subduction in the Eastern Kunlun. Therefore, the final closure of the Proto-Tethyan Ocean and the beginning of collisional orogeny occurred before the Early Silurian.
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