Fractionation of the copper, oxygen and hydrogen isotopes between malachite and aqueous phase
Fractionation of the copper, oxygen and hydrogen isotopes between malachite and aqueous phase
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DOI：
10.1016/j.gca.2021.02.009
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发表时间：
2021-03-24
影响因子：
5
通讯作者：
Majzlan, Juraj
中科院分区：
文献类型：
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作者：
Plumhoff, Alexandra M.;Mathur, Ryan;Majzlan, Juraj
矿物稳定同位素平衡同位素性质的研究主要是由于其在解决地球化学问题中的应用而开始的。因此，我们研究了矿床氧化带中常见的次生矿物孔雀石。稳定同位素表征可以通过建立母体沃茨的同位素组成来提供孔雀石形成所需的信息。在10 ~ 65 ℃的温度范围内，通过沉淀实验确定了孔雀石和溶液之间的平衡氧和氢同位素分馏，并可根据温度的不同分为两组分馏因子。对于45-65 ℃，分馏表示为1000 ln α（氧）（mal-sol）= 2.87（10（6）/T-2）+0.96和1000 ln α（氢）（mal-sol）= -1.47（10（6）/T-2）-22.3，温度（T）以开尔文为单位。应用大气降水线上孔雀石的氢、氧分馏因子，计算出代表孔雀石同位素组成的“孔雀石线”。我们还研究了10 - 65 ℃溶液和孔雀石之间的铜同位素分馏因子：1000 ln α（铜）（sol-mal）= 0.033（10（6）/T-2）- 0.19，δ（65）Cumalachite溶液的分馏位移= -0.17 +/- 0.05 ppm。这种分馏位移意味着，化学反应没有改变的氧化还原状态只产生轻微的铜同位素分馏。计算的分馏因子的氧和氢被用来确定的氧和氢同位素组成的原生沃茨的天然孔雀石样品从世界各地的一些地方。天然孔雀石的δ O-18（VSMOW）值为+22.1至+29.5 ‰，δ D值为-132至-61 ‰，母水和Cu同位素的δ O-18（VSMOW）值为-14.5至-7 ‰，δ D值为-107至-36 ‰，认为所研究的孔雀石样品均为大气降水形成的表生样品。即使在乌拉尔山脉的大量孔雀石样本中。（俄罗斯），从同位素组成中没有检测到其他流体的迹象。(C)2021爱思唯尔有限公司保留所有权利。
Studies of the equilibrium isotope properties of stable isotopes of minerals have been initiated principally because of their application to the solution of geochemical problems. Therefore, we examined malachite, a common secondary mineral in the oxidation zone of ore deposits. Stable isotope characterization can contribute needed information on the formation of malachite by establishing the isotopic composition of the parental waters. The equilibrium oxygen and hydrogen isotope fractionations between malachite and solution were determined by precipitation experiments over the temperature range from 10 to 65 degrees C and could be distinguished in two sets of fractionation factors depending on the temperature. For 45-65 degrees C, the fractionation is expressed as 1000 ln alpha(oxygen)(mal-sol) = 2.87(10(6)/T-2) + 0.96 and 1000 ln alpha(hydrogen)(mal-sol) = -1.47(10(6)/T-2) - 22.3 with temperature (T) in Kelvin. With the application of the fractionation factors of oxygen and hydrogen of malachite onto source water from the meteoric water line, we were able to calculate the "malachite line" which represents the isotopic compositions of malachite that would precipitate from such water. We also examined the copper isotope fractionation factors between solution and malachite from 10 to 65 degrees C: 1000 ln alpha(copper)(sol-mal) = 0.033(10(6)/T-2) - 0.19 with fractionation shift of Delta(65) Cumalachite-solution = -0.17 +/- 0.05 parts per thousand. This fractionation shift implies that chemical reactions without change of the redox state yield only minor copper isotope fractionation. The calculated fractionation factors of oxygen and hydrogen were used to determine the oxygen and hydrogen isotopic composition of the parental waters of natural malachite samples from a number of localities worldwide. With delta O-18(VSMOW) values of +22.1 to +29.5 parts per thousand and delta D values of -132 to -61 parts per thousand for the natural malachite and delta O-18(VSMOW) values of -14.5 to -7 parts per thousand and delta D values of -107 to -36 parts per thousand for the parental water together with the Cu isotopes, it is to assume that all investigated malachite samples are supergene samples which formed from meteoric water. Even in massive malachite samples from Ural Mts. (Russia), no signs of other fluids were detected from the isotopic composition. (C) 2021 Elsevier Ltd. All rights reserved.