Native copper and α-copper–zinc in sediments from the TAG hydrothermal field (Mid-Atlantic Ridge, 26°N): nature and origin

Dekov, Vesselin M.; Damyanov, Zhelyazko; Kamenov, George D.; Bonev, Ivan K.; Bogdanov, Kamen

doi:10.1016/s0025-3227(99)00034-1

Cited by 10 publications

(8 citation statements)

References 36 publications

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“…The presence of calcium carbonate in samples was confirmed by a simple preliminary test with a few drops of diluted hydrochloric acid (1M HCl). The presence of other (white) minerals that could interfere with Cal and influence the value of the L* (such as sulfate) was considered negligible, because it was not detected in the TAG field [9][10][11][12][13].…”

Section: Mineral Phases Identified In Hydrothermal Samplesmentioning

confidence: 99%

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XRD Identification of Ore Minerals during Cruises: Refinement of Extraction Procedure with Sodium Acetate Buffer

et al. 2020

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The on-board identification of ore minerals during a cruise is often postponed until long after the cruise is over. During the M127 cruise, 21 cores with deep-seafloor sediments were recovered in the Trans-Atlantic Geotraverse (TAG) field along the Mid Atlantic Ridge (MAR). Sediments were analyzed on-board for physicochemical properties such as lightness (L*), pH and Eh. Selected samples were studied for mineral composition by X-ray powder diffraction (XRD). Based on XRD data, sediment samples were separated into high-, low- and non-carbonated. Removal of carbonates is a common technique in mineralogical studies in which HCl is used as the extraction agent. In the present study, sequential extraction was performed with sodium acetate buffer (pH 5.0) to remove carbonates. The ratio between the highest calcite XRD reflection in the original samples (Iorig) vs its XRD-reflection in samples after their treatment with the buffer (Itreat) was used as a quantitative parameter of calcite removal, as well as to identify minor minerals in carbonated samples (when Iorig/Itreat > 24). It was found that the lightness parameter (L*) showed a positive correlation with calcite XRD reflection in selected TAG samples, and this could be applied to the preliminary on-board determination of extraction steps with acetate buffer (pH 5.0) in carbonated sediment samples. The most abundant minerals detected in carbonated samples were quartz and Al- and Fe-rich clays. Other silicates were also detected (e.g., calcic plagioclase, montmorillonite, nontronite). In non-carbonated samples, Fe oxides and hydroxides (goethite and hematite, respectively) were detected. Pyrite was the dominant hydrothermal mineral and Cu sulfides (chalcopyrite, covellite) and hydrothermal Mn oxides (birnessite and todorokite) were mineral phases identified in few samples, whereas paratacamite was detected in the top 20 cm of the core. The present study demonstrates that portable XRD analysis makes it possible to characterize mineralogy at cored sites, in particular in both low- and high-carbonated samples, before the end of most cruises, thus enabling the quick modification of exploration strategies in light of new information as it becomes available in near-real time.

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Section: Mineral Phases Identified In Hydrothermal Samplesmentioning

confidence: 99%

“…Most studies of mineral deposits, including those regarding active TAG mounds, have been determined onshore by X-ray powder diffraction (XRD) in conventional laboratories [9][10][11][12][13]. Available XRD studies have been performed with dry powder mounts, generally without any pre-treatment of samples to remove calcite.…”

Section: Introductionmentioning

confidence: 99%

XRD Identification of Ore Minerals during Cruises: Refinement of Extraction Procedure with Sodium Acetate Buffer

et al. 2020

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“…Mid-ocean ridge deposits associated with N-MORB are typically enriched in Cu and Zn [Bogdanov et al, 1995;Fouquet et al, 1993cFouquet et al, , 1996Fouquet et al, , 1998bHannington et al, 1991Hannington et al, , 1995Hannington et al, , 1999Herzig and Hannington, 1995;Humphris et al, 1995;Krasnov et al, 1995;Mozgova et al, 1999]. Back-arc and arc systems associated with felsic rocks are enriched in Zn, Pb, Cu, As, Sb, Ag, Au, Hg, and Ba [Binns and Scott, 1993;Binns et al, 1993;de Ronde et al, 2005;Dekov et al, 1999;Fouquet et al, 1993b;Herzig et al, 1993;Petersen et al, 2003Petersen et al, , 2004Tanahashi et al, 2006;Tufar, 1989]. Sedimenthosted mid-ocean ridge sulfide deposits have generally lower concentrations of base metals than deposits on sedimentstarved ridges [Ames et al, 1993;Goodfellow and Franklin, 1993;Houghton et al, 2004;Koski et al, 1985Koski et al, , 1988Peter and Scott, 1988;Zierenberg et al, 1993Zierenberg et al, , 1998].…”

Section: Introductionmentioning

confidence: 99%

Geodiversity of hydrothermal processes along the Mid-Atlantic Ridge and ultramafic-hosted mineralization: A new type of oceanic Cu-Zn-Co-Au volcanogenic massive sulfide deposit

Fouquet

Cambon

Étoubleau

et al. 2010

Geophysical Monograph Series

140

164

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Several hydrothermal deposits associated with ultramafic rocks have recently been found along slow spreading ridges with a low magmatic budget. Three preferential settings are identified: (1) rift valley walls near the amagmatic ends of ridge segments; (2) nontransform offsets; and (3) ultramafic domes at inside corners of ridge transform-fault intersections. The exposed mantle at these sites is often interpreted to be a detachment fault. Hydrothermal cells in ultramafic rocks may be driven by regional heat flow, cooling gabbroic intrusions, and exothermic heat produced during serpentinization. Along the Mid-Atlantic Ridge (MAR), hydrothermal deposits in ultramafic rocks include the following: (1) sulfide mounds related to high-temperature low-pH fluids (Logatchev, Rainbow, and Ashadze); (2) carbonate chimneys related to low-temperature, high-pH fluids (Lost City); (3) low-temperature diffuse venting and high-methane discharge associated with silica, minor sulfides, manganese oxides, and pervasive alteration (Saldanha); and (4) stockwork quartz veins with sulfides at the base of detachment faults (15°05′N). These settings are closely linked to preferential circulation of fluid along permeable detachment faults. Compared to mineralization in basaltic environments, sulfide deposits associated with ultramafic rocks are enriched in Cu, Zn, Co, Au, and Ni. Gold has a bimodal distribution in low-temperature Zn-rich and in hightemperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the MAR seem to be more abundant than in ophiolites on land. This may be because ultramafic-hosted volcanogenic massive sulfide deposits on slow spreading ridges are usually not accreted to continental margins during obduction and may constitute a specific marine type of mineralization.

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“…Zincian native copper is relatively common and is found in a wide range of environments, including lunar regolith, kimberlites, basic and ultrabasic rocks, hydrothermal ores, volcano-sedimentary sequences, and pelagic sediments (Dekov et al, 1999). Native lead in contrast has been documented in a few tens of localities worldwide, but this rarity is likely to be biased because the mineral has frequently been disregarded as a contamination or an artifact.…”

Section: Authigenic Mineralsmentioning

confidence: 99%

The Sandstone-Hosted Beverley Uranium Deposit, Lake Frome Basin, South Australia: Mineralogy, Geochemistry, and a Time-Constrained Model for Its Genesis

Wülser¹,

Brugger²,

Foden³

et al. 2011

Economic Geology

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Native copper and α-copper–zinc in sediments from the TAG hydrothermal field (Mid-Atlantic Ridge, 26°N): nature and origin

Cited by 10 publications

References 36 publications

XRD Identification of Ore Minerals during Cruises: Refinement of Extraction Procedure with Sodium Acetate Buffer

XRD Identification of Ore Minerals during Cruises: Refinement of Extraction Procedure with Sodium Acetate Buffer

Geodiversity of hydrothermal processes along the Mid-Atlantic Ridge and ultramafic-hosted mineralization: A new type of oceanic Cu-Zn-Co-Au volcanogenic massive sulfide deposit

The Sandstone-Hosted Beverley Uranium Deposit, Lake Frome Basin, South Australia: Mineralogy, Geochemistry, and a Time-Constrained Model for Its Genesis

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