Abstract
The quartz-vein-type Baiyinhan tungsten deposit is located at the eastern part of the Central Asian Orogenic Belt, NE China. Analyses of fluid inclusions, H-O isotope of quartz and Re-Os isotope of molybdenite were carried out. Three stages of mineralization were identified: The early quartz + wolframite + bismuth stage, the middle quartz + molybdenite stage and the late calcite + fluorite stage. Quartz veins formed in the three stages were selected for the fluid inclusion analysis. The petrographic observation and fluid inclusion microthermometry results revealed three types of fluid inclusions: CO2-H2O (C-type), liquid-rich (L-type) and vapor-rich (V-type). The homogenization temperatures of C-type, V-type and L-type inclusions were 233–374 °C, 210–312 °C, and 196–311 °C, respectively. The salinity of the three types of inclusions was identical, varying in the range of 5–12 wt%. The H-O isotope analyses results showed that quartz had δ18OH2O and δDSMOW compositions of −2.6‰ to 4.3‰ and −97‰ to −82‰, respectively, indicating that the ore-forming fluids were mainly derived from magmatic water with a minor contribution of meteoric water. The addition of meteoric water reduces the temperature and salinity of the ore-forming fluids, which leads to a decrease of the solubility of tungsten and molybdenum in the fluids and eventually the precipitation of minerals. Re-Os isotopic analysis of five molybdenite samples yielded an isochron age of 139.6 ± 7.6 Ma (2σ) with an initial 187Os of −0.05 ± 0.57 (MSWD = 3.5). Rhenium concentrations of the molybdenite samples were between 3.1 ug/g and 8.5 ug/g. The results suggest that the metals of the Baiyinhan deposit have a crust origin, and the mineralization is one episode of the Early Cretaceous tungsten mineralization epoch which occurred at the eastern part of the Central Asian Orogenic Belt.
Highlights
The eastern Central Asian Orogenic Belt (CAOB) in NE China is characterized by orogenic events of the Paleo-Asian domain superimposed by the magmatism of the Paleo-Pacific and Ohotsk Ocean tectonic domains, which resulted in extensive distribution of Mesozoic volcanic and granitic rocksMinerals 2020, 10, 664; doi:10.3390/min10080664 www.mdpi.com/journal/mineralsMinerals 2020, 10, 664 together with widespread Cu, Mo, Au, Pb-Zn-Ag and Sn polymetal deposits [1–7]
The results suggest that the metals of the Baiyinhan deposit have a crust origin, and the mineralization is one episode of the Early Cretaceous tungsten mineralization epoch which occurred at the eastern part of the Central Asian Orogenic Belt
The H-O isotope analyses were accomplished with a MAT253 mass spectrometer at the Institute of Geology and Geophysics, Chinese Academy of Sciences
Summary
The eastern Central Asian Orogenic Belt (CAOB) in NE China is characterized by orogenic events of the Paleo-Asian domain superimposed by the magmatism of the Paleo-Pacific and Ohotsk Ocean tectonic domains, which resulted in extensive distribution of Mesozoic volcanic and granitic rocks. Minerals 2020, 10, 664 together with widespread Cu, Mo, Au, Pb-Zn-Ag and Sn polymetal deposits [1–7]. An increasing number of tungsten deposits have been discovered in this region, revealing a great potential of large-scale tungsten mineralization. The previous geochronology studies of the tungsten mineralization in eastern CAOB have shown. The mineralization includes porphyry, skarn and quartz-type deposits. The quartz-vein-type tungsten deposits can be divided into two subtypes: Quartz-wolframite and quartz-scheelite vein types. The Baiyinhan quartz-vein-type tungsten deposit belongs to the quartz-wolframite subtype
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