The Archean-Proterozoic craton of West Africa hosts numerous gold deposits, which are spatially and temporally related to the Eburnean orogeny that took place between and Ma, and included multiple deformation events. The majority of these gold deposits are located along shear zones. The structural history is relatively well established for most gold deposits, but absolute timing of the mineralization is commonly lacking. Gold mineralization was structurally characterized at each deposit, and dated by the Re-Os method on pyrite, arsenopyrite, and pyrrhotite grains that were coeval with the gold deposition. Combined structural and Re-Os geochronological constraints allow two groups of gold deposits to be distinguished. Early orogenic gold formed during the Eoeburnean orogeny, i. These Re-Os ages on the early sulfides at Wassa and Kiaka are significant because they definitively provide the first direct age constraints on gold-only Eoeburnean mineralization in the Birimian of West Africa. The high uncertainties on the Nassara and Damang ages may be directly linked to the low rhenium and osmium contents of the studied samples. These results highlight the polyphase character of the widespread gold mineralization in the West African craton. Although the late stages of the Eburnean orogeny constitute a prolific period for the formation of highgrade gold mineralization, identification of less well-studied early-stage gold deposits, which can also contain large quantities of gold, is critical for mineral exploration in the West African craton.
rhenium osmium using
This reos is affected by the charge re-os of rhenium atom. The beta decay arsenopyrite Re is used for rheniumosmium dating re-os ores. Facts Re-os Osmium.
“U-Pb and Re-Os geochronologic evidence for two alkalic porphyry ore-forming “Dating multiply overprinted Sn-mineralized granites? examples from the.
Pyrite is the most abundant sulfide mineral. Pyrite’s metallic luster and pale brass-yellow hue give it a superficial resemblance to gold , hence the well-known nickname of fool’s gold. The color has also led to the nicknames brass , brazzle , and Brazil , primarily used to refer to pyrite found in coal. By Georgius Agricola ‘s time, c. Pyrite is usually found associated with other sulfides or oxides in quartz veins , sedimentary rock , and metamorphic rock , as well as in coal beds and as a replacement mineral in fossils , but has also been identified in the sclerites of scaly-foot gastropods.
A substantial proportion of the gold is “invisible gold” incorporated into the pyrite see Carlin-type gold deposit. It has been suggested that the presence of both gold and arsenic is a case of coupled substitution but as of the chemical state of the gold remained controversial. Pyrite has been used since classical times to manufacture copperas iron II sulfate. Iron pyrite was heaped up and allowed to weather an example of an early form of heap leaching. The acidic runoff from the heap was then boiled with iron to produce iron sulfate.
In the 15th century, new methods of such leaching began to replace the burning of sulfur as a source of sulfuric acid. Pyrite remains in commercial use for the production of sulfur dioxide , for use in such applications as the paper industry , and in the manufacture of sulfuric acid. A newer commercial use for pyrite is as the cathode material in Energizer brand non-rechargeable lithium batteries. Pyrite is a semiconductor material with a band gap of 0.
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Metallic minerals are mainly pyrite, pyrrhotite, arsenopyrite, chalcopyrite, galena, and sphalerite, of which pyrrhotite, pyrite, and arsenopyrite are the dominant.
Mineral deposits of Canada: a synthesis of major deposit-types, district metallogeny, the evolution of geological provinces, and exploration methods; by Goodfellow, W D ed. This publication is contained in Goodfellow, W D; Mineral deposits of Canada: a synthesis of major deposit-types, district metallogeny, the evolution of geological provinces, and exploration methods, Geological Association of Canada, Mineral Deposits Division, Special Publication no.
Consolidating Canada’s Geoscience Knowledge. The lower Ordovician Meguma Group of Nova Scotia consists of a lower thick unit of Goldenville Formation greywacke and an upper unit of black sulphidic Halifax Formation slate. The transition between the two units contains an Mn-rich horizon and Tremadocian fossils. The auriferous Goldenville formation comprises thick beds of light to dark grey sandy metagreywacke that contain thin beds of green chloritic silt and clay on the upper contact of each Bouma cycle.
Occasionally at this stratigraphic horizon, the green slaty beds are replaced by a sequence of black sulphidic slate, which occurs abundantly throughout local stratigraphic sections. Within these carbonaceous sections, auriferous ribbon laminated, crack-seal veins occur, commonly at the upper contacts of slate beds with the overlying metagreywacke. They may extend for several kilometres in length and 10s to s of bedding-parallel veins may occur in a single district. Also occurring are en echelon veins, various types of angular veins smaller , pegmatitic veins, and cross cutting veins larger.
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Rhenium-osmium geochronology using arsenopyrite was undertaken for three gold deposits in the Meguma terrane, Nova Scotia, Canada, in order to better constrain their age of formation and to assess the utility of arsenopyrite for dating similar deposits globally. The lack of common Os in some arsenopyrite samples from both The Ovens and Dufferin permit calculation of single mineral model ages for each deposit, which are identical to those determined using the isochron method.
Initial Os compositions for the two vein types at The Ovens suggest a predominately crustal source of Os in the mineralizing fluids, whereas a less radiogenic initial Os composition for arsenopyrite from Dufferin does not as clearly define a crustal metal source. At a third locality, the Touquoy deposit, the Re-Os systematics of arsenopyrite associated with disseminated gold mineralization do not define a precise formation age, possibly as a result of mixing of Re and Os derived from the mineralizing fluid and the shale host rock.
The Re-Os ages of arsenopyrite indicate that there were at least two distinct periods of gold deposition in the Meguma terrane coinciding with widespread tectonothermal events: regional deformation and metamorphism associated with Acadian orogenesis, and widespread generation of meta- and peraluminous granites and high-grade metamorphism within the basement rocks under the Meguma terrane.
Based on U-Pb dating, as well as Re-Os and Pb-isotope systematics of and model age calculations using Re-Os isotopic data for arsenopyrite and in situ.
Table S1. It is not known whether environmental O 2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the Great Oxidation Event.
Transient oxygenation events, like the one captured by the Mount McRae Shale, probably separated intervals of less oxygenated conditions during the late Archean. Multiple lines of geochemical evidence from sedimentary rocks point to the production and accumulation of photosynthetic O 2 in surface environments since at least 3 billion years ago Ga 1 — 7. In contrast, sulfur mass-independent fractionation S-MIF indicates that Archean atmospheric O 2 levels were predominantly below 0.
However, transiently higher O 2 levels are possible if crustal recycling of S-MIF signatures is taken into account Therefore, evidence for O 2 production during Archean time may represent one of several scenarios. One possibility is that small linear stepwise increases in atmospheric O 2 allowed mild oxygenation and oxidative continental weathering to occur continuously and with increasing intensity in the several hundred million years before the first major accumulation of O 2 in the atmosphere [the ca.
Nonlinear fluctuations in Earth surface redox conditions may have also been driven by variations in the relative fluxes of reducing gases, such as biogenic methane 11 — Distinguishing between these hypotheses is critical for understanding the dynamics of planetary oxygenation on Earth and ultimately the evolution of complex life 7. The 2. Increased Mo and Re concentrations may capture a transient increase in oxidative continental weathering, possibly associated with a rise in atmospheric O 2 levels, and the subsequent decrease in Mo and Re concentrations may reflect a return to a lower redox state 1.
Because the magnitude of Mo and Re enrichment in marine sediments is influenced by local bottom water redox conditions, organic carbon export fluxes, and sedimentation rates 16 , 17 , the elevated Mo and Re concentrations may reflect changes in local depositional conditions against a backdrop of mild environmental O 2 levels 1.
rhenium osmium using
Both Re and Os are siderophile elements mostly enriched in alloy and sulfide phases. As Os is a highly compatible element during partial melting of mantle and Re is a moderately incompatible element Brenan, ; Sattari et al. This significant geochemical behavior makes Re- Os isotope system available for tracing and dating.
Bohemian Massif: geochemistry and Re-Os dating of sulfide mineralization. The Re-Os age of arsenopyrite overlaps published age data for the KJPC and.
Degao Zhai, Anthony E. Economic Geology ; 5 : — Native gold is intergrown with molybdenite and pyrite in auriferous quartz veins hosted by a monzogranite-monzonite stock and locally by Proterozoic gneiss, thereby offering an excellent opportunity to directly date the mineralizing event. Uranium-Pb age determinations for zircon yielded ages for the monzogranite and monzonite of Numerous mafic to felsic dikes, which are crosscut by ore veins pre-ore , parallel to these veins possibly synore , or crosscut by them post-ore , were carefully examined and dated.
The age of mineralization was determined directly using the Re-Os method applied to molybdenite. A total of 19 molybdenite samples separated from auriferous quartz veins yielded widely differing Re-Os model ages of to Ma, and replicate analyses of individual samples also yielded widely differing ages. Significantly, the wide range is attributable entirely to the results obtained for some coarse-grained molybdenite samples and is interpreted to be due to Re and Os isotope decoupling, the considerable spatial Re heterogeneity, the analytical procedure e.
Thus, the molybdenite Re-Os ages are identical, within uncertainty, to those of the dikes that are parallel to the ore veins, indicating that these dikes were emplaced contemporaneously with the ore and that they and the Haigou gold mineralization are of late Paleozoic age ca.
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The Iso-Kuotko deposit is located 10 km to the north of Suurikuusikko along the same shear zone. Gold mineralization at Iso-Kuotko formed in two major stages: an early stage refractory gold mineralization with auriferous arsenopyrite with similarities to the ore at Suurikuusikko and a late, main stage mineralization with free gold in carbonate-quartz veins with abundant pyrrhotite, native bismuth and other sulphide minerals.
This latter ore is absent at Suurikuusikko. Based on U-Pb dating, as well as Re-Os and Pb-isotope systematics of rock-forming and hydrothermal minerals, we evaluate the relationships between tectonic evolution and formation of gold deposits throughout the late Palaeoproterozoic in the northern part of the CLGB. Results from in situ U-Pb dating of zircon and petrographically well constrained hydrothermal monazite and xenotime by LA-ICPMS, and model age calculations using Re-Os isotopic data for arsenopyrite and in situ Pb-isotope data for galena from the Iso-Kuotko deposit provide evidence for multiple episodes of hydrothermal activity along the KiSZ.
Data suggest coincident felsic magmatism and structurally controlled fluid flow events during wrench fault-dominated N-S shearing associated with early, micro-continent accretion ushering in the Svecofennian orogeny.
Structural characteristics and Re–Os dating of quartz-pyrite veins in Rhenium–Osmium arsenopyrite geochronology of Meguma Group gold deposits.
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THE Re–Os AGE VALUES OF GOLD-BEARING SULPHIDE AT THE RADZIMOWICE DEPOSIT. The several Co-bearing arsenopyrite samples for Re–Os dating.
The Longmendian Ag—Pb—Zn deposit is located in the southern margin of the North China Craton, and the mineralization occurs mainly in quartz veins, altered gneissic wallrocks, and minor fault breccias in the Taihua Group. Based on vein crosscutting relations, mineral assemblages, and paragenesis, the mineralization can be divided into three stages: 1 quartz—pyrite, 2 quartz—polymetallic sulfides, and 3 quartz—carbonate—polymetallic sulfides.
Wallrock alteration can be divided into three zones, i. Fluid inclusions in all Stage 1 to 3 quartz are dominated by vapor-liquid two-phase aqueous type W-type. The H—C—O—S—Pb isotope compositions indicate that the ore-forming materials may have been derived from the Taihua Group and the granitic magma. The fluid boiling and cooling and mixing with meteoric water may have been critical for the Ag—Pb—Zn ore precipitation.
It is also an important mineral province, hosting a variety of ore deposits [ 1 , 2 ]. The regional Au and Mo mineralization was coeval with the first Mesozoic magmatic phase there late Jurassic-early Cretaceous, ca. Meanwhile, Ag—Pb—Zn mineralization was mostly coeval with the second magmatic phase early Cretaceous, ca. In addition, Neoproterozoic Mo mineralization was also reported locally, as represented by the Zhaiao and Longmendian deposits [ 15 , 16 ].
The Longmendian Mo mineralization is spatially related to the migmatites but distal from intrusions or faults [ 17 ]. Four types of fluid inclusions FIs have been recognized in the Mo-bearing quartz and calcite grains, i. The Paleoproterozoic mineralization event was interpreted to have linked to the collision between the western and eastern NCC along the Trans North China Orogen at 1.
The regional tectonic events include the formation of the continental nucleus and then the cratonic basement in the Paleoproterozoic, Mesoproterozoic rifting, Neoproterozoic-to-Paleozoic sedimentation, and Mesozoic tectonic reactivation.
Re and Os rhenium and osmium are chalcophile-siderophile elements transition metals with a unique position in isotope geochemistry. Unlike other commonly used decay schemes for radiometric dating, these metals take residency in resource-related media, for example, sulfide minerals, the organic component in black shales, coals, and bitumens and oils.
In short, the reducing environment is their haven whereas under oxidizing conditions, Re and Os become unmoored and the radiometric clock becomes compromised. The clock is not temperature sensitive, and its applicability spans Early Archean to Pleistocene. This Bunsen Medal lecture will explore and review the challenges in bringing Re-Os from the meteorite-mantle community into the crustal environment.
Towards the north, locally mineralized amphibolites (4 g/t Au) are in faulted contact ±12 Ma for gold-bearing arsenopyrite were obtained by Re-Os dating.
Technician support will underpin growth of the Program through increased student involvement, increased Front Range collaborations, and expansion of global partnerships. New research opportunities will build on AIRIE’s nine-year history of collaborations with over scientists from industry, government and academia, on projects spanning five continents. To date, the focus of the Program has been on development, testing, and application of the rhenium-osmium Re-Os molybdenite geochronometer, with transfer of this technology to the mineral industry for application in exploration.
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