Magmatic-hydrothermal metallogenic system in Zhenlongshan, Guangxi: Evidence from ore-forming fluids and materials

The Zhenlongshan magmatic hydrothermal metallogenic system is located in the dome formed by a large short axis anticline in the front arc of the "mountain shaped structure" in Guangxi.The deposits (occurrence) mainly occur in the Cambrian and Devonian clastic rocks.Fluid inclusion thermometry, laser Raman, and H-O-S isotope studies were conducted on typical ore deposits.The system elucidated the source of ore-forming fluids, characteristics and evolution of ore-forming fluids, and sources of ore-forming materials for gold, silver, copper, lead, and zinc deposits around the porphyry, and preliminarily explored the genetic connections of various ore deposits (occurrence) around the porphyry.The results show that the inclusions are mainly gas-liquid inclusions, and contain more CO₂ and CH₄ inclusions, and occasionally contain NaCl daughter crystals.The homogenization temperature of high temperature deposit is 320~339℃, and the salinity is 8%~9% NaCl eqv; the homogenization temperature of medium temperature deposit is 280~299℃, and the salinity is 7%~8% NaCl eqv; the homogenization temperature of low temperature deposit is 160~179℃, and the salinity is 5%~6% NaCl eqv.That is, with the decrease of homogenization temperature, salinity also decreases.The δD_V-SMOW and δ¹⁸O_V-PDB of quartz concentrate in -55‰~-80.1‰ and -9.1‰~-18.8‰.The H-O isotopic diagram is mainly in the range of magmatic water and tends to shift to meteoric water, which indicates that the main source of fluid in the above deposit may be magmatic water, and there is the mixing of meteoric water in the later stage.The sulfur isotope peak values are concentrated in the range of -2‰~2‰, in which arsenopyrite is mainly positive and stibnite is mainly negative.Generally, there is a relatively uniform sulfur source, indicating that the sulfur in sulfide comes from magma.The above research shows that the distribution of ore deposits (occurrence) in Zhenlongshan area has obvious zoning characteristics of magmatic hydrothermal metallogenic system.Porphyry high temperature hydrothermal deposits are developed in the pluton and its edge, and the periphery gradually transits to medium and low temperature hydrothermal deposits.The horizontal and vertical mineralization zoning model for the magmatic hydrothermal metallogenic system in Zhenlongshan area are established.