Fluid inclusion constraints on the origin of the Zhaiwa Mo deposit, Luoning county, Henan Province

Abstract

The Zhaiwa Mo deposit, in Luoning county, Henan province, is located in the Xiong'er Terrane in southern margin of North China Craton. Its ore bodies, occurring as lode, are hosted in biotite-amphibole-plagiogneiss of the Taihua Group and controlled by subsidiary faults of the Machaying fault which is the south boundary fault of the Xiong'er terrane. Three stages of hydrothermal ore - forming process are recognized, Quartz-molybdenite (I), which is the main metallogenic stage, Quartz-polymetallic sulfide (II) and Quartz-carbonate (III). Two types of fluid inclusions, i.e. H2O-NaCl, daughter mineral-bearing, are observed. Laser-Raman spectrum showing that the most important component of fluid inclusion is water. From early to late stages, homogeneous temperatures of fluid inclusions change from 100-260 °C (I), through 110-160°C (II), to 120-180°C (III), this showing that the Zhaiwa Mo deposit belongs to low-temperature hydrothermal deposit; salinities change from 2-25 wt%NaCl.eqv(I), through 6-30 wt%NaCl.eqv (II), and to 7-25 wt%NaCl.eqv(III). The broad range of homogeneous temperatures of stage I, the evolution of salinities from bimodal to unimodal, and negative correlation between homogeneous temperatures and salinities indicate that fluid mixing is the most important metallogenic mechanism in Zhaiwa Mo deposit. The characteristic of fluid inclusion in Zhaiwa Mo deposit are high density, high salinities and low temperature, which is the result of CaCl2-bearing fluid involved in ore forming process, the mixing of hot magmatic fluid and cold CaCl2-bearing brine result to precipitation of molybdenite. In summary, The geological and fluid inclusions features of the Zhaiwa Mo deposit are similar to intrusion-related deposit, we affirm that the Zhaiwa Mo deposit is a intrusion-related Mo deposit.