Search

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. [ABSTRACT FROM AUTHOR]

The Chaobuleng skarn deposit, located in the Erlian–East Ujimqin region, Northeast China, is a medium-sized Fe Zn polymetallic deposit. Iron-polymetallic mineralization occurs mainly as stratiform, lenticular, and vein types hosted in the contact zone between the Chaobuleng syenogranite and the Devonian Taerbagete Formation. The Chaobuleng deposit is a calcic skarn deposit dominated by a grossular-rhodonite-allanite-epidote assemblage. The ore minerals mainly consist of magnetite, pyrite, sphalerite, chalcopyrite, and bismuthinite, with lesser amounts of molybdenite, arsenopyrite, and pyrrhotine. Four mineralization stages have been identified: (I) a prograde skarn stage; (II) a retrograde skarn stage; (III) a quartz-minor calcite-polymetallic sulfide stage; and (IV) a quartz-calcite-minor pyrite stage. Three types of fluid inclusions (FIs) in garnet, quartz and calcite were classified: vapor-rich two-phase FIs (V-type), liquid-rich two-phase FIs (L-type), and daughter mineral-bearing three-phase FIs (S-type). The homogenization temperatures of FIs from stages I, II, III, and IV are 446–547, 411–519, 279–415, and 147–217 °C, respectively, with corresponding salinities of 0.87–59.47, 0.52–51.52, 0.70–13.25, and 3.05–7.85 wt% NaCl equiv., respectively. The results suggest that mineralization in the Chaobuleng deposit occurred at a depth of 1.0–2.8 km, with fluid boiling and mixing with meteoric water likely being responsible for ore precipitation. The C O isotope data suggest the early ore-forming fluids were mainly related to felsic rocks and were accompanied by intense water/rock reactions during the fluid migration. The S Pb isotopic compositions indicate that ore materials were derived from the mixing between magma and wall rocks. Zircon U Pb dating yields a weighted mean 206Pb/238U age of 135.9 ± 0.8 Ma (MSWD = 1.03), which represents the crystallization time of the syenogranite. Together, these data suggest that the Chaobuleng deposit is a skarn ore system that is spatially, temporally, and genetically related to syenogranite and formed in an extensional environment resulted from the roll back of the subducted Paleo-Pacific Plate. [Display omitted] • The Chaobuleng deposit is a typical skarn Fe Zn deposit, formed in the Early Cretaceous. • The fluids evolved from a high-temperature, intermediate-salinity NaCl–H 2 O system of magmatic water. • Ore-forming materials had a mixed source of the granitic pluton and Taerbagete Formation. [ABSTRACT FROM AUTHOR]