Study Of Low-temperature Hydrothermal Fluids’ Characteristics In The North Rim Of Sichuan Basin

Geological fluids exist in many kinds of geological process, and play an important partin various diageneses as well as mineralization. This paper is on the basis of fieldinvestigation, applying the petrographic and geochemical methods to study thelow-temperature fluids varieties and characteristics in dabashan tectonic belt and Mayuanlead-zinc deposit of beiba vault, Micangshan tectonic belt, clarifying its macrography andmicroscopic petrography symbol, dividing fluids activity time, discussing the fluids originand environment, announcing the fluids geochemical characteristic.Researches show that Dabashan tectonic belt and Beiba dome of Micangshan tectonicbelt separately have different periods′low-temperature hydrothermal fluids. Dabashan thrustand nappe tectonic belt could differentiate the preindosinian, indosinian and yanshanian fluids.Preindosinian fluids have strongly metamorphic and deformation phenomenon, and somecrumple with the stratum; Indosinian fluids have no metamorphic but weak deformationphenomenon. The veins most fill in the X or En echelon type of joint. Yanshanian fluids haveno metamorphic and deformation phenomenon, and the viens fill in the separation fracture.Geological mapping of fluid shows that preindosinian fluids mainly exist in Dabashanthrust and nappe tectonic belt which mainly mineral is quarts, and the trend of the veins aremainly5°、53°、302°、317°and333°. Indosinian fluids exist in every part of Dabashantectonic belt which quantity and area are enlargement. The minerals mainly are quarts andcalcite.35°、82°and300°are the mainly trend. Yanshanian fluids are familiar with theindosinian fluids in mineral and distribution, and the trends mainly focus on60°and310°.Carbon and oxygen isotopes show that three stages calcite have three origins: one islimestone′recrystallization. The other is the mixture of limestone′solution and rain. Anotheris mamatic water. Hydrogen and oxygen isotopes show that the water in low-temperaturehydrothermal calcite was mainly from rain, which seeped into the strata and reacted with therock and formed the formation water. Affected by the volcanic material, part of vein show thecharacteristic of magmatic water.Trace element and REE show that the first and second calcite veins in Dabashan tectonicbelt are normal sediment, and the third calcite vein have litte hot-water feature. All calcite veins were formed in a oxidation environment.