Fluid speciation controls of low temperature copper isotope fractionation applied to the Kupferschiefer and Timna ore deposits

Asael, Dan; Matthews, Alan; Oszczepalski, Sławomir; Bar‐Matthews, Miryam; Halicz, Ludwik

doi:10.1016/j.chemgeo.2009.01.015

Cited by 79 publications

(26 citation statements)

References 27 publications

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“…Literature sources that reported chalcocite as the major phase present in the copper isotope analyses were used [16][17][18][19] along with new data from Coates Lake, Copper Mine, Michigan, and Udokan. Data from Kupferschiefer [20], Michigan [21,22], and Coates Lake [23] provide classic examples of sedimentary copper deposits along with the prospect, Coppermine [24].…”

Section: Types Of Chalcocite Considered and Deposits Analyzedmentioning

confidence: 99%

Origins of Chalcocite Defined by Copper Isotope Values

et al. 2018

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The origin of chalcocite is explored through a comparison of the copper isotope values of this mineral from supergene enrichment, sedimentary copper/red bed, and high-temperature hypogene mineralization around the world. Data from the literature and the data presented here ( = 361) reveal that chalcocite from high-temperature mineralization has the tightest cluster of values of 65 Cu = 0 ± 0.6 in comparison to sedimentary copper/red bed 65 Cu = −0.9 ± 1.0 and supergene enrichment 65 Cu = +1.9 ± 1.8. Although the errors of the means overlap, large portions of the data lie in different values, allowing for distinguishing ranges for 65 Cu of <−1‰ for sedimentary copper/red bed, between −1 and +1 for high-temperature hypogene, and >+1 for supergene enrichment chalcocite. The copper isotope values of sedimentary copper/red bed and supergene enrichment chalcocite are caused by redox reactions associated with the dissolution and transport of copper, whereas the tighter range of copper isotope values for hypogene minerals is associated with processes active with equilibrium conditions.

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Section: Types Of Chalcocite Considered and Deposits Analyzedmentioning

confidence: 99%

Origins of Chalcocite Defined by Copper Isotope Values

et al. 2018

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] As a result, the residual primary copper-rich minerals (Cu(I)) have their δ 65 Cu values shifted toward lower values as the leaching processes proceed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] In the case of our sample, primary cubanite grains near the weathered surface of the sample were significantly affected by dissolution during low-temperature oxidation and weathering processes, and copper (Cu(I)) in the cubanite grains was probably leached, and precipitated as thin secondary minerals (malachite) (Cu(II)). Thus, these grains show lower δ…”

Section: Application To Cubanite Micro-grains From the Mihara Mine Jmentioning

confidence: 99%

“…2 This variation is quite large compared with other non-traditional stable isotopes (e.g., Fe and Zn), 1 presumably due to significant isotope fractionations during redox reactions (oxidation states 0, +1 and +2 of Cu are not uncommon in nature, compared with Fe and Zn) that occurred at relatively low temperatures. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Therefore, the copper isotopes are potentially an excellent tracer of geological and biological processes.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of UV-fs-LA-MC-ICP-MS for Precise in situ Copper Isotopic Microanalysis of Cubanite

Ikehata

Hirata

2013

ANAL. SCI.

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“…There are virtually no geologic studies involving copper isotopes prior to 1999 [1], but subsequent advances in analytical methods that lowered analytical errors have made it possible to investigate the natural variation of copper isotopes in geological materials (e.g., [2][3][4]). In the two decades following, there have been multiple studies that document the natural variability of copper isotopes in mineral deposit environments (e.g., [5][6][7][8][9][10][11][12][13][14][15]). Copper isotopic studies have demonstrated their value in developing a better understanding of the processes involved in the genesis of copper-bearing minerals, and Mathur [16] has demonstrated that copper isotopes are directly applicable to mineral exploration.…”

Section: Introductionmentioning

confidence: 99%

Copper Isotope Constraints on the Genesis of the Keweenaw Peninsula Native Copper District, Michigan, USA

Bornhorst

Mathur

2017

Minerals

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Abstract:The Keweenaw Peninsula native copper district of Michigan, USA is the largest concentration of native copper in the world. The copper isotopic composition of native copper was measured from stratabound and vein deposits, hosted by multiple rift-filling basalt-dominated stratigraphic horizons over 110 km of strike length. The δ 65 Cu of the native copper has an overall mean of +0.28‰ and a range of −0.32‰ to +0.80‰ (excluding one anomalous value). The data appear to be normally distributed and unimodal with no substantial differences between the native copper isotopic composition from the wide spread of deposits studied here. This suggests a common regional and relatively uniform process of derivation and precipitation of the copper in these deposits. Several published studies indicate that the ore-forming hydrothermal fluids carried copper as Cu 1+ , which is reduced to Cu 0 during the precipitation of native copper. The δ 65 Cu of copper in the ore-forming fluids is thereby constrained to +0.80‰ or higher in order to yield the measured native copper values by reductive precipitation. The currently accepted hypothesis for the genesis of native copper relies on the leaching of copper from the rift-filling basalt-dominated stratigraphic section at a depth below the deposits during burial metamorphism. Oxidative dissolution of copper from magmatic source rocks with magmatic δ 65 Cu of 0‰ ± 0.3‰ is needed to obtain the copper isotopic composition of the metamorphogenic ore-forming hydrothermal fluids. In order to accommodate oxidative dissolution of copper from the rift-filling basalt source rocks, the copper needs to have been sited in native copper. Magmatic native copper in basalt is likely stable when the magma is low in sulfur. Low sulfur is predicted by the lack of sulfide minerals in the ore deposits and in the rift-filling basalt-dominated section, which are source rocks, the same rocks through which the ore fluids moved upwards, and the host rocks for the native copper ores. When combined with geologic evidence and inferences, the copper isotopic composition of native copper helps to further constrain the genetic model for this unique mining district.

show abstract

Fluid speciation controls of low temperature copper isotope fractionation applied to the Kupferschiefer and Timna ore deposits

Cited by 79 publications

References 27 publications

Origins of Chalcocite Defined by Copper Isotope Values

Origins of Chalcocite Defined by Copper Isotope Values

Evaluation of UV-fs-LA-MC-ICP-MS for Precise in situ Copper Isotopic Microanalysis of Cubanite

Copper Isotope Constraints on the Genesis of the Keweenaw Peninsula Native Copper District, Michigan, USA

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