Yankuang ceshi (Nov 2018)
Hydrogen-Oxygen-Sulfur Isotope Composition of Shihoushan Pyrite and Tungsten Polymetallic Deposit, Southern Jiangxi
Abstract
BACKGROUND Shihoushan Pyrite and Tungsten polymetallic deposit, located in the northern of Yinkeng-Qingtang Au-Ag polymetallic integrated exploration area, is the only large pyrite deposit in southern Jiangxi. The pyrrhotite-pyrite (-chalcopyrite-scheelite) orebody hosts in calciferous sandstone in the Zishan Formation of Carboniferous System, mainly formed in the quartz-sulfide stage. OBJECTIVES In order to better understand the ore-forming material source and the evolution processes of Shihoushan deposit, the primary ores were selected as laboratory raw materials for stable isotope testing. METHODS H-O-S isotope composition of primary ore minerals was analyzed combined with the Pb isotope and metallogenic age results. The ore-forming fluid source and ore-forming evolution process are discussed. RESULTS The δ34S values range from -5.50‰ to -0.20‰, which are mainly concentrated at -3.0‰-0.0‰ (n=11), show the typical signature of mantle S. The wide range of variation indicates that the ore-forming fluid has been subjected to superposition and modification. H-O isotope analyses show that δD=-74.4‰--48.0‰ (n=9), δ18OH2O=3.76‰-10.86‰ (n=9), indicating that the ore-forming fluid is composed mainly of magmatic water and metamorphic water, with minor meteoric water. CONCLUSIONS According to the comprehensive analysis, the ore-forming fluid of this deposit mainly comes from deep magmatic water. The contact between magmatic hydrothermal fluid and calcium-bearing strata forms a large-scale metamorphic fluid, mixed with a small amount of meteoric water. The fluid immiscibility makes the ore-forming materials precipitate in the contact between the rock mass and the calcium-bearing strata, forming a hydrothermal filling and metasomatic deposit.
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