# Age and Source of the Jinjingzui Skarn-Type Gold Deposit in the Southeastern Hubei Province, China
## 3 Sampling and Analytical Methods  
Zircon and rock powder were extracted from three fresh diorite samples (JJZ-7, JJZ-8, and JJZ-9), all sourced from the -280-m level footrill of the Jinjingzui skarn deposit. The fresh diorite has a gray to grayish-green color and has fine-grained, medium and massive textures (Figure 6). The mineral compositions mainly include plagioclase (60-80%), amphibo (3-8%), pyroxene (2-7%), biotite (3-5%), quartz (1-3%), and minor quantities of titanite, zircon and apatite (Figure 6). Molybdenum (Figure 7) and pyrite are separated from skarn and silicified altered diorite, respectively. (Figure 4).  
The major trace and rare earth element concentrations of the samples were analyzed at Yanduzhongshi Testing Technology Co., LTD., Beijing, China. The concentrations of major elements were determined using X-ray fluorescence (XRF). Before XRF analysis, the powder sample was weighed, mixed with Li\({}_{2}\)B\({}_{4}\)O\({}_{7}\) (1:8) flux, and then heated to 1150 \({}^{\circ}\)C. Sample melts were poured into a gold-platinum crucible to cool, forming a uniform glass sheet. Glass sheets were directly analyzed via XRF spectrometry. The loss on ignition (LOI) was quantified by subjecting samples to heating in silica crucibles at 1000 \({}^{\circ}\)C for one hour, with subsequent measurement of weight reduction. Trace and rare earth elements concentrations were analyzed by inductively coupled plasma-mass spectrometer (ICP-MS) using a M90, Analytik Jena instrument. The error of the measured data is less than 5% based on repeated assay of the control sample GSR 2. The error of some volatile and trace elements is less than 10%.  
The Re-Os isotope analysis of molybden was performed at Beijing Yandu Zhongshi Testing Technology Co., Ltd. (Beijing, China). The analysis utilized the isotope dilution method, with specific procedures including reverse aqua regia digestion using [PERSON] tubes, conducted under sealed conditions at 220 \({}^{\circ}\)C for 24 h. Os was separated and enriched via direct distillation, while Re was extracted with acetone from an 8 mol/L sodium hydroxide solution. Isotope ratios were subsequently determined using ICP-MS (Thermo Fisher Scientific Triton Plus, MA, USA). In-house sulfide Re-Os isotope reference JCBY from the Jinchuan Cu-Ni deposit was used for quality control.  
S and Pb isotopes were analysed at ALS Chemex (Guangzhou) Co., Ltd. (Guangzhou, China). First, the powder crushed to 60-80 mesh was selected under a binocular microscope to isolate pyrite minerals, ensuring a purity of approximately 99%. The sulfur analysing procedure is as follows: accurately weigh an appropriate amount of the pyrite powder sample and transfer it to a tin boat. Use the Costech ECS 4010 elemental analyzer in conjunction with the Finnigan MAT 253 stable isotope ratio mass spectrometer to determine the 34S/32S isotopic ratio in the sample. Lead isotope ratios were determined by taking a 0.5 g sub-sample and dissolving it sequentially with perchloric acid, hydrofluoric acid, nitric acid and hydrochloric acid. After digestion, the solution was evaporated by heating on an electric mantle, following which the residue was re-dissolved in hydrochloric acid; The cooled solution was volumetrically diluted to 25 mL with hydrochloric acid (10%) and analyzed by ICP-MS. Pb isotope standard material and internal standards were used to validate sample measurements.