Magma mixing processes in a continental collision zone: Insights from mineralogical and geochemical constraints

Detailed Description of Dataset Generation Process, Processing Methods, and Equipment/Tools Used 4 Analytical Methods 4.1 Zircon U-Pb Dating The dataset generation process involves first collecting rock samples through fieldwork in Tibet, followed by laboratory pretreatment, zircon separation, and testing, ultimately yielding zircon U-Pb age data and related isotopic ratios. Sample Pretreatment: Zircon separation, epoxy mount preparation, and cathodoluminescence (CL) imaging were conducted at Langfang Shangyi Rock and Mineral Testing Technical Service Co., Ltd. Based on the CL images, zircon crystals with well-developed zoning and high euhedrality were selected for dating analysis. Experimental Analysis: Zircon U-Pb dating was performed at the Key Laboratory of Sedimentary Mineralization and Sedimentary Minerals, Shandong University of Science and Technology, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The analytical system consisted of an Agilent 7900 ICP-MS coupled with a GeoLas HD laser ablation system; helium was used as the carrier gas during laser ablation, and argon as the makeup gas, with a laser beam spot diameter of 32 µm. Data Calibration: Zircon standard sample 91500 was employed as the external standard for U-Pb dating, glass standard sample NIST SRM 610 as the external standard for trace element calibration, and 29Si as the internal standard for data correction. Data Processing: Raw data were processed using ICPMSDataCal 10.0 software (Liu et al., 2010); concordia diagrams and weighted mean age calculations were generated using IsoplotR 4.11 software embedded in Excel (Ludwig, 2003), ultimately forming the zircon U-Pb age dataset. Equipment and Tools Used: Experimental equipment included a GeoLas HD laser ablation system, an Agilent 7900 ICP-MS, and a cathodoluminescence imager; data processing software included ICPMSDataCal 10.0 and IsoplotR 4.11 (Excel-embedded version); standard materials included zircon standard 91500 and glass standard NIST SRM 610. 4.2 Whole-Rock Major and Trace Element Analysis The dataset generation process involves crushing and grinding field-collected rock samples into powder in the laboratory, followed by X-ray fluorescence (XRF) spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) analysis to obtain whole-rock major and trace element content data. Sample Pretreatment: Rock samples were crushed and ground into powder finer than 200 mesh, then dried for subsequent use. Major Element Analysis: Conducted at the Key Laboratory of Sedimentary Mineralization and Sedimentary Minerals, Shandong University of Science and Technology, using a Rigaku ZSX Primus IV X-ray fluorescence (XRF) spectrometer with an analytical precision better than ±5%. Trace Element Analysis: Performed at Nanjing Hongchuang Geological Exploration Technology Service Co., Ltd., using an Agilent 7900 inductively coupled plasma mass spectrometer (ICP-MS) with an analytical precision better than ±10% for most trace elements. Equipment and Tools Used: Experimental equipment included a Rigaku ZSX Primus IV XRF spectrometer and an Agilent 7900 ICP-MS; sample processing tools included a crusher, a grinder, and a drying oven. 4.3 Electron Probe Microanalysis (EPMA) The dataset generation process involves preparing rock samples into thin sections, followed by electron probe microanalysis to obtain major element composition and content data of minerals for mineral identification and compositional characterization. Sample Pretreatment: Rock samples were prepared into standard thin sections (30 µm thick). Experimental Analysis: Carried out at Nanjing Hongchuang Geological Exploration Technology Service Co., Ltd., using a JEOL JXA-8230 electron probe microanalyzer. Analytical conditions were set as follows: accelerating voltage of 15 kV, beam current of 10 nA, and beam diameter of 10 µm; peak counting time was 10 seconds for Si, Ti, Al, Fe, Mn, Mg, Ca, Na, and K, and 20 seconds for Cr. Data Calibration: Specialized standard materials were used for calibration, specifically: chlorite (for Si, Al, Mg), rutile (for Ti), olivine (for Fe), johannsenite (for Mn, Ca), albite (for Na), orthoclase (for K), and chromium oxide (for Cr). Equipment and Tools Used: Experimental equipment included a JEOL JXA-8230 electron probe microanalyzer; sample processing tools included a microtome and a grinder; standard materials included chlorite, rutile, olivine, johannsenite, albite, orthoclase, and chromium oxide standard samples. 4.4 In Situ Zircon Lu-Hf Isotope Analysis The dataset generation process involves conducting laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) analysis near the same spots used for zircon U-Pb dating to obtain in situ zircon Lu-Hf isotopic ratios and related parameter data. Sample Selection: Based on zircon CL images and U-Pb dating spots, Lu-Hf isotope analysis spots were determined (closely corresponding to the U-Pb dating spots). Experimental Analysis: Performed at Wuhan Sample Solution Analytical Technology Co., Ltd., Hubei, China, using an analytical system consisting of a GeoLas HD laser ablation system and a Neptune Plus MC-ICP-MS. Helium was used as the carrier gas to transport ablated materials, and a small amount of nitrogen was added after the ablation cell to enhance Hf sensitivity (Hu et al., 2012); the laser beam spot diameter was set to 44 µm. A high-performance cone combination recently developed for the Neptune Plus was employed, and Lu mass fractionation was corrected using the empirically determined Yb mass fractionation coefficient (βYb). Data Processing: Data processing, including identification of signal and blank intervals and mass fractionation correction, was performed using ICPMSDataCal software (Liu et al., 2010); detailed analytical procedures were described in Hu et al. (2012), ultimately generating the zircon Lu-Hf isotope dataset. Equipment and Tools Used: Experimental equipment included a GeoLas HD laser ablation system and a Neptune Plus MC-ICP-MS; data processing software included ICPMSDataCal; auxiliary gases included helium and nitrogen; standard materials included relevant isotopic calibration standards (selected according to the method of Hu et al., 2012). 4.5 TIMA (TESCAN Integrated Mineral Analyzer) Analysis The dataset generation process involves preparing rock samples into thin sections and coating them with carbon, followed by TESCAN Integrated Mineral Analyzer (TIMA) analysis to obtain mineral BSE images, energy-dispersive spectroscopy (EDS) data, and datasets on mineral composition, content, and dissemination characteristics. Sample Pretreatment: Rock samples were prepared into standard thin sections, which were coated with carbon prior to analysis (to improve conductivity). Experimental Analysis: Conducted at Nanjing Hongchuang Geological Exploration Technology Service Co., Ltd., using a Mira-3 scanning electron microscope equipped with four EDAX Element 30 energy-dispersive spectrometry (EDS) detectors. Analytical conditions were set as follows: accelerating voltage of 25 kV, beam current of 9 nA, and working distance of 15 mm; beam current and backscattered electron (BSE) signal intensity were automatically calibrated using a platinum Faraday cup, while EDS calibration was performed using a Mn standard sample. Analysis was carried out in Liberation Analysis mode, simultaneously acquiring BSE images and EDS data with an X-ray counting time of 1000 counts per point, a pixel size of 2.5 µm, and an EDS step size of 7.5 µm. Data Processing: BSE images and EDS data were integrated and analyzed using TIMA supporting software to identify mineral types, statistics mineral content and dissemination characteristics, forming a comprehensive mineralogical dataset. Equipment and Tools Used: Experimental equipment included a Mira-3 scanning electron microscope, EDAX Element 30 EDS detectors, and a TESCAN Integrated Mineral Analyzer (TIMA); sample processing tools included a microtome, a grinder, and a carbon coater; standard materials included a Mn standard sample and a platinum Faraday cup calibration standard; data processing software included TIMA supporting analysis software.