The Qibaoshan polymetallic ore field is located in the Wulian area, Shandong Province, China. Four ore deposits occur in this ore field: the Jinxiantou Au–Cu, Changgou Cu–Pb–Zn, Xingshanyu Pb–Zn, and Hongshigang Pb–Zn deposits. In the Jinxiantou deposit, three paragenetic stages were identified: quartz–pyrite–specularite–gold (Stage 1), quartz–pyrite–chalcopyrite (Stage 2), and quartz–calcite–pyrite (Stage 3). Liquid-rich aqueous (LV type), vapor-rich aqueous (V type), and halite-bearing (S type) fluid inclusions (FIs) are present in the quartz from stages 1–3. Microthermometry indicates that the initial ore-forming fluids had temperatures of 351–397 °C and salinities of 42.9–45.8 mas. % NaCl equivalent. The measured hydrogen and calculated oxygen isotopic data for fluid inclusion water (δ18OFI = 11.1 to 12.3‰; δDFI = −106.3 to −88.6‰) indicates that the ore-forming fluids were derived from magmatic water; then, they were mixed with meteoric water. In the Changgou deposit, three paragenetic stages were identified: quartz–pyrite–specularite (Stage 1), quartz–pyrite–chalcopyrite (Stage 2), and quartz–galena–sphalerite (Stage 3). LV, V, and S-type FIs are present in the quartz from stages 1–3. Microthermometry indicates that the initial ore-forming fluids had temperatures of 286–328 °C and salinities of 36.7–40.2 mas. % NaCl equivalent. The measured hydrogen and calculated oxygen isotopic data for fluid inclusion water (δDFI = −115.6 to −101.2‰; δ18OFI = 12.2 to 13.4‰) indicates that the ore-forming fluids were derived from magmatic water mixed with meteoric water. The characteristics of the Xingshanyu and Hongshigang deposits are similar. Two paragenetic stages were identified in these two deposits: quartz–galena–sphalerite (Stage 1) and quartz–calcite–poor sulfide (Stage 2). Only LV-type FIs are present in the quartz in stages 1–2. The ore-forming fluids had temperatures of 155–289 °C and salinities of 5.6–10.5 mas. % NaCl equivalent. The measured hydrogen and calculated oxygen isotopic data for fluid inclusion water (δDFI = −109.8 to −100.2‰; δ18OFI = 10.2 to 12.1‰) indicates that the ore-forming fluids were derived from circulating meteoric waters. The sulfur isotopes (δ34Ssulfide = 0.6 to 4.3‰) of the four deposits are similar, indicating a magmatic source for the sulfur with minor contributions from the wall rocks. The ore field underwent at least two phases of mineralization according to the chronology results of previous studies. Based on the mineral assemblage and fluid characteristics, we suggest that the late Pb–Zn mineralization was superimposed on the early Cu (–Au) mineralizaton in the Changgou deposit.
The Junggar–Tianshan collage, located in the southern portion of the Kazakhstan Cu–Au–Mo metallogenic province, encompasses the Junggar block and Tianshan orogenic belt, extending from north to south. The region's peak porphyry/skarn-type mineralization period is the Middle-Late Devonian. However, information on (1) the spatial distribution of porphyry/skarn-type mineralization, (2) geochemical (including isotopic) signatures and fertility of their causative intrusions, and (3) genetic models and tectonic settings is scarce. We introduce new data (zircon U–Pb dating, geochemistry, and Sr–Nd–Pb–Hf isotopes) from the Saibo deposit, along with compiled published data from Late Paleozoic porphyry/skarn-type deposits in the region. Our synthesis reveals that the Middle-Late Devonian porphyry/skarn-type deposits are predominantly located in the northern section of the western Tianshan orogenic belt and eastern Junggar terrane. In addition, all ore-causative granitoids exhibit normal-arc and undifferentiated I-type affinities. Diverse Th/Yb and Ba/La ratios indicate slab-derived hydrous melts metasomatized the mantle source for arc magmas in western Tianshan, while slab-derived aqueous fluids metasomatized the mantle source in East Junggar. Zircon trace element analysis suggests these magmas were high in oxygen fugacity, with those in the eastern Junggar terrane having higher water content compared to those in the northern part of the western Tianshan orogenic belt. Sr–Nd–Pb–Hf isotope data suggest an enriched lithospheric mantle source for the ore-causative granitoids in West Tianshan and a juvenile basaltic lower crust source in East Junggar. Based on the geological, geochronological, and geochemical evidence, we propose that the ore-causative granitoids in West Tianshan were formed through a slab-melting model associated with the rollback of the subducting north Tianshan oceanic slab. In contrast, those in East Junggar likely originated from MASH (i.e., melting, assimilation, storage, and homogenization) processes in a hot zone of the juvenile lower crust related to the subduction of the Kuerti-Erqis Ocean.
The Huitongshan skarn Cu deposit is located in the southern orogenic belt of Beishan and is one of the most important metallogenic belts in northwestern China. The ore body is hosted within the external contact zone between the K-feldspar granite and Ordovician marble. The zircon U–Pb dating shows that ore-related K-feldspar granite formed at 402 ± 3.0 Ma, which thus constrains that the mineralization of the Huitongshan skarn copper deposits mostly likely occurred in the Early Devonian. Through field investigation and petrographic observation, the deposit formation can be divided into two periods and four stages of mineralization; the skarn period contains the garnet–diopside skarn stage I and magnetite–quartz stage Ⅱ; the quartz–sulfide period contains the quartz–polymetallic sulfide stage III and the quartz–calcite–minor pyrite stage IV. The variations of fluid inclusion (FI) types, homogenization temperatures, and salinities show the fluid evolution process. In stage Ⅰ and stage Ⅱ, the FIs are characterzied by daughter mineral-bearing (S-type) and vapor-rich (V-type) with homogenization temperatures of 352 °C–485 °C. The salinities of V-type and S-type FIs are 2.1–9.8 wt% NaCl equivalent (equiv.) and 41.5–57.0 wt% NaCl equiv., respectively, indicating that these fluids would boil at pressures of 150–500 bar and depths of 0.6–2.0 km. In stage III, the FIs are mainly daughter mineral-bearing (S-type), vapor-rich (V-type), or liquid-rich (l-type) with homogenization temperatures of 260 °C–325℃, 265℃–325℃, 260℃–320℃ and salinities of 35.0–39.4 wt% NaCl equiv., 1.7–3.5 wt% NaCl equiv., and 6.4–11.5 wt% NaCl equiv., respectively; fluid boiling would occur at pressures of 40–100 bar and depths of 0.4–1.0 km. In stage IV, only l-type FIs are observed, with homogenization temperatures and salinities of 180 °C–245℃ and 2.1–7.2 wt% NaCl equiv., respectively. The HOC isotopes of mineralization stages II–IV suggest that the ore-forming fluids in the early stage (stage Ⅱ) mainly came from magmatic hydrothermal fluid, while a large quantity of meteoric water was mixed with those in the later stages (stage III and IV). The S–Pb isotopic compositions indicate that ore materials were derived from mixing between the magmatic source and the Huaniushan Formation.
The Haerdaban Pb-Zn deposit is located on the western edge of the Chinese Western Tianshan Orogen. This deposit consists of stratiform and veined mineralization hosted in Proterozoic carbonaceous and dolomitic limestone. Three metallogenic stages were recognized: an early sedimentary exhalative stage (stage 1), an intermediate metamorphic remobilization stage (stage 2), and a late magmatic-hydrothermal stage (stage 3). Fluid inclusions (FIs) present in stage 1 are liquid-rich aqueous, with homogenization temperatures of 206–246 C and salinities of 5.9–11.6 wt% NaCl eq. FIs present in stage 2 are also liquid-rich aqueous, with homogenization temperatures of 326–349 C and salinities of 3.4–6.6 wt% NaCl eq. FIs present in stage 3 include halite-bearing, vapor-rich aqueous, and liquid-rich aqueous FIs. Homogenization temperatures for these FIs span a range of 249–316 C. Halite-bearing, vapor-rich aqueous, and liquid-rich aqueous FIs yield salinities of 33.8–38.9, 2.6–3.5, and 4.2–8.1 wt% NaCl eq., respectively. Oxygen and hydrogen isotopic data (δ 18 O H2O = 2.6–13.6‰, δD H2O = −94.7 to −40.7‰) indicate that the ore-forming fluids of stages 1–3 were derived from modified seawater, metamorphic water, and magmatic-meteoric mixed water, respectively. Sulfur isotopic data (δ 34 S = 2.1–16.3‰) reveal that ore constituents were derived from mixing of marine sulfate and magmatic materials. Lead isotopic data ( 206 Pb/ 204 Pb = 17.002–17.552, 207 Pb/ 204 Pb = 15.502–15.523, 208 Pb/ 204 Pb = 37.025–37.503) reveal that ore constituents were derived from a mixed crust-mantle source. We propose that the Haerdaban deposit was a Proterozoic sedimentary exhalative deposit overprinted by later metamorphic remobilization and magmatic-hydrothermal mineralization.
The Saibo skarn–porphyry deposit, located in West Tianshan, NW China, is a large copper deposit discovered recently; however, information regarding the differences and connections between skarn and porphyry mineralization remains limited. Thus, this study aimed to investigate fluid inclusions (FIs), H–O–C–S–Pb isotopes, and U–Pb, and Re–Os geochronology to unravel the origin and evolution of the entire hydrothermal system. Skarn mineralization occurs as stratiform and lenticular in the contact zone between the granodiorite porphyry and Kusongmuqieke Group limestone. We identified four mineralization stages: prograde skarn stage (IS), retrograde skarn stage (IIS), quartz–pyrrhotite–chalcopyrite stage (IIIS), and calcite–quartz–pyrite stage (IVS), and four types of FIs: CH4-rich (C-type), halite-bearing (S-type), vapor-rich (V-type), and liquid-rich (L-type) FIs. The homogenization temperatures (Th) of FIs from stages IS, IIIS, and IVS were 366–419, 271–315, and 174–235 °C, respectively, with salinities of 1.7–46.0, 2.2–9.6, and 4.5–7.7 wt% NaCl eqv., respectively. Porphyry mineralization occurs as veinlet-disseminated ores in the granodiorite porphyry. We identified three mineralization stages: quartz–molybdenite–pyrite stage (IP), quartz–chalcopyrite–pyrite stage (IIP), and calcite–quartz–galena stage (IIIP). Unlike skarn mineralization, only the S-, V-, and L-type FIs were identified, with Th of 332–379, 263–315, and 169–233 °C from stages IP, IIP, and IIIP, respectively, and salinities of 1.9–42.3, 2.2–9.6, and 4.2–6.9 wt% NaCl eqv., respectively. The H–O isotope data indicate that the ore-forming fluids were initially derived from magmatic water and gradually diluted by meteoric water during fluid migration. According to C isotope data and the presence of C-type FIs, fluids from skarn mineralization contained more organic carbon than those from porphyry mineralization. The S–Pb isotope data of sulfides suggest that ore-forming materials are derived from both granodiorite porphyry and the Kusongmuqieke Group, although the latter contributed more to skarn mineralization. Pyrites from porphyry mineralization yielded a Re−Os isochron age of 376.0 ± 7.9 Ma, which was slightly younger than the chalcopyrite Re−Os ages of skarn mineralization (>379 Ma). The granodiorite porphyry, which is considered the ore-causative intrusion, yielded a U–Pb age of 380.8 ± 1.8 Ma. Our results indicate that two styles of mineralization were formed successively at different spatial locations during the emplacement of the granodiorite porphyry in a southward subduction setting of the North Tianshan Ocean. The proposed metallogenic model provides a better understanding of the Saibo skarn–porphyry metallogenic system and is expected to assist in the exploration of similar deposits in the West Tianshan orogenic belt.
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