Role of Hydrothermal Fluids in the Formation of the Kamioka Skarn-Type Pb–Zn Deposits, Japan

Morishita, Y.; Wada, Ayaka

doi:10.3390/geosciences11110447

Cited by 2 publications

(4 citation statements)

References 15 publications

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“…Several isotopic studies (Kushikino deposit [22,29], Ohtani and Kaneuchi deposits [24], Takatori deposit [25], and Noya deposit [26]) were introduced, assuming that the mineral assemblages were close to equilibrium. We observed varying degrees of kinetic reactions and equilibrium goals in the δ 13 C-δ 18 O relationship of limestone at the Kamioka deposit [27]. These previous findings in several hydrothermal ore deposits suggest that actual isotope fractionations in nature, even at low-to-intermediate temperatures, are similar to equilibrium fractionations among minerals with coexisting fluid.…”

Section: Discussionsupporting

confidence: 69%

“…The study on the Kamioka skarn-type Pb-Zn deposits is a good example to consider the kinetics-to-equilibrium transition in isotopes for the genesis and evolution of the oreforming hydrothermal fluid [27]. The crystalline limestone in the mining area suffered from the ore-forming hydrothermal fluid.…”

Section: Hydrothermal Depositmentioning

confidence: 99%

“…Oppositely, the direct precipitation of calcite into veins from the hydrothermal fluid also occurred. The calcite was supposed to be equilibrated with the hydrothermal fluid, and the δ 13 C and δ 18 O values of calcite were the end-members of the mining area [27]. The δ 13 C and δ 18 O values of the isotopically reacted limestone are distributed in a wide range of isotope ratios between the original limestone and precipitated veins in a δ 13 C-δ 18 O graph [27].…”

Section: Hydrothermal Depositmentioning

confidence: 99%

“…The calcite was supposed to be equilibrated with the hydrothermal fluid, and the δ 13 C and δ 18 O values of calcite were the end-members of the mining area [27]. The δ 13 C and δ 18 O values of the isotopically reacted limestone are distributed in a wide range of isotope ratios between the original limestone and precipitated veins in a δ 13 C-δ 18 O graph [27]. This confirms that the isotope exchange kinetics in the limestone changed the δ 13 C and δ 18 O values to various degrees.…”

Section: Hydrothermal Depositmentioning

confidence: 99%

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Hydrothermal Calcite Precipitation in Veins: Inspired by Experiments for Oxygen Isotope Fractionation between CO2 and Calcite from 1 °C to 150 °C

Morishita

2023

Applied Sciences

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The oxygen isotope ratios of minerals are important for estimating the formation temperature of hydrothermal deposits. Calcite is generally found in most mining districts. The oxygen isotope ratio of hydrothermal calcite in isotopic equilibrium with a fluid depends on that of the fluid as well as the formation temperature. The isotope ratios of calcite are generally determined to measure the isotope ratios of CO2 generated via reaction with 100% phosphoric acid at 25 °C. This is why the oxygen isotope fractionation between CO2 and calcite at 25 °C is required to conduct the procedure. When using other carbonate minerals such as dolomite, ankerite, and siderite, the reaction requires higher temperatures. Therefore, the oxygen isotope fractionation between CO2 and calcite at higher temperatures should be known because the laboratory standard sample of carbonates is usually calcite. Here, the oxygen isotope fractionation in CO2 during the reaction of calcite with phosphoric acid at temperatures between 1 °C and 150 °C was thoroughly determined in the first half, and the value can be represented by the following equation: 1000 lnα = 0.494 (106/T2) + 4.64. The experiments raised questions such as the equilibrium vs. kinetics issue in isotopic reactions in the formation of hydrothermal ore deposits. The raised issue is discussed in the second half based on the findings of previous isotope studies in deposits.

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