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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.
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Institutional Sign In. Sign In or Create an Account. User Tools. Sign In. Advanced Search. Article Navigation. Close mobile search navigation Article navigation. VolumeNumber 5. Previous Article Next Article. Research Article August 01, Google Scholar. Anthony E. Williams-Jones Anthony E. Jiajun Liu Jiajun Liu. David Selby David Selby.
Stein H.J. () Dating and Tracing the History of Ore Formation. In: Holland H.D. and Turekian K.K. (eds.) Treatise on Geochemistry, Second Edition, vol. situ U-Pb dating of monazite and xenotime as well as trace element analysis of apatite have been performed formed as a product of apatite leaching by hydrothermal fluids percolating through . tectonic history of the area is complex and is. Request PDF on ResearchGate | Dating and Tracing the History of Ore Formation | Rhenium-osmium (Re-Os) dating of sulfides has transformed economic.
Chao Li Chao Li. Liang Qi Liang Qi. Donghang Guo Donghang Guo. Economic Geology 5 : Article history accepted:. You do not currently have access to this article. You could not be signed in. Librarian Administrator Sign In.
Buy This Article. Email alerts New issue alert. Early publications alert. Article activity alert. Partial melting of ancient lower crust generated felsic magmas with high concentrations of Mo that accumulated within the ancient crustal components. Whereas, the copper mineralization is correlated to the remelting of residual sulfide cumulates in subduction-modified lower crust. The Late Cretaceous porphyry Mo—Cu metallogenesis in the southern Yidun Terrane is considered to be related to the transtensional faulting that triggered asthenospheric upwelling beneath the former sulfide-cumulated arc crust.
The timing and duration of magmatic-hydrothermal activities are of vital importance to understanding the ore-deposit formation Stein, ; Shu et al. The molybdenite Re—Os dating method has become a powerful tool to directly constrain the age of mineralization, due to the high Re and low common Os concentrations of molybdenite Stein et al.
Unlike the approach for zircon U—Pb dating, whole-rock crushing to acquire a vial of molybdenite grains puts Re—Os dating at risk. Full-text available. SynonymsRe—Os geochronology; Re—Os geochronologyDefinitionRhenium—osmium geochronology is based on radioactive decay of Re to Os with a half-life of Both Re and Os are siderophile-chalcophile elements, that is, they are both strongly partitioned into metals or sulfides rather than silicates.
This distinguishes them from other widely used geochronometers whose parent-daughter elements reside in silicates. Re—Os geochronology underpins dating of materials from meteorites, the mantle, and metallic ore deposits. Furthermore, both Re and Os are redox-sensitive metals, soluble when oxidized, and fixed by reduction. This is the basis for Re—Os dating of the depositional age of organic-rich sedimentary rocks and provides a temporally constrained record of changing redox conditions t Such sulphides are referred to as LLHR low level highly radiogenicas their Os isotopic composition mimics molybdenite Stein et al.
Conference Paper. Aug The analysed Cu-sulphides have Re concentrations ranging from 5 to 12 ppb, and total Os concentrations ranging from 26 to 52 ppt. Significant common Os is present in all of the analysed samples.
The origin of the Kupferschiefer mineralization is commonly attributed to multiple flow events of lowtemperature oxidizing metalliferous fluids from basinal sediments and trapped by the geochemical barrier of carbonaceous black shale rich in organic carbon. Our results strongly suggest that within the world-class mining area in Poland the main economic Ag-bearing Cu sulphide mineralization event took place in the Late Triassic Norianca.
Combined, the elevated Re and Os abundances and variable isotopic ratios offer the potential for Re-Os radiometric dating of oils and their fractions. The Re-Os isochron dating method e. Re-Os geochronology is successful in cases where three critical conditions are met: i the Os isotopes are homo- genously distributed at the time of oil formation, ii the duration of oil generation is relatively short, and iii the Re-Os isotopic system remains undisturbed with time.
Re-Os dating of maltenes and asphaltenes within single samples of crude oil. Re-Os geochronology of oil may constrain the timing of oil formation and improve oil-source and oil-oil correlations. Typically, asphaltene ASPHthe heaviest and most Re-Os rich oil fraction, from multiple oils within an oil field or a larger petroleum system are analyzed to obtain sufficient spread in Re-Os isotopic ratios, a mathematical necessity for precise Re-Os isochrons.
The similarity of ages between magmatic rocks and mineralisation for all three studied deposits implies that the ore-forming magmatism and hydrothermal process leading to deposition of Re-bearing molybdenites took place synchronously. The close temporal relationship between magmatism and hydrothermal processes is common for a range of porphyry deposits as reported in a number of publications e.
These studies report coeval magmatism and related mineralisation, with time gaps usually of less than 1 Ma, and often within the analytical uncertainty of the age measurements. The Urals can be regarded as a significant Cu-Mo-porphyry province, hosting over 30 porphyry deposits. Although their geological structure and ore-forming processes have been studied in great detail, uncertainty remains about their age and related geotectonic setting. In this contribution we report for the first time the Re-Os dating of molybdenites from three Cu-Mo porphyry deposits, namely Kalinovskoe, Mikheevskoe and Talitsa.
Three molybdenite samples from the Kalinovskoe deposit yield Silurian Re-Os ages ranging from The molybdenite from the Mikheevskoe deposit gives Re-Os ages of The molybdenite from Talitsa Mo-porphyry deposit yields the youngest Re-Os ages of Thus, the studied Cu and Mo porphyry deposits are not synchronous and belong to distinct tectonic events of the Urals.
Two samples of molybdenite-bearing veinlets from two different drill cores were selected for Re-Os dating. Hadi Mohammaddoost. The Chah-Firouzeh deposit with about Mt ore reserves 0. The mineralization is associated with a porphyry quartz-monzodiorite to quartz-diorite stock, which intruded into Eocene volcanic rocks consisting of andesite, basalt, and andesitic to dacitic tuff. Hydrothermal alteration types in the area include potassic, phyllic, and propylitic varieties.
Silicic alteration locally occurred at the surface, while supergene argillic alteration overprinted the other alterations at shallow levels. Mineralization occurs as quartz-sulfide veinlets and stockworks, as well as disseminations in the porphyry body and volcanic host rocks, in association with potassic and phyllic alteration.
Hypogene minerals in the deposit include pyrite, chalcopyrite, magnetite, molybdenite, and bornite. Supergene enrichment is irregularly developed in the Chah-Firouzeh deposit. However, the unclear paragenetic relationships of molybdenite-bearing veins dated in previous studies, coupled with the poor external reproducibility of ICP-MS analysis Stein,potentially caused by memory effects of Os and destabilized ion signal in the long term and potential bias between laboratories e.
Our Re-Os ages The giant Pulang porphyry Cu-Au district Four intrusive phases host the three Pulang deposits, which are, in order of emplacement, premineralization fine-grained quartz diorite and coarse-grained quartz diorite, intermineraliza-tion quartz monzonite, and late-mineralization diorite porphyry.
The complex intruded carbonaceous rocks of the Late Triassic Tumugou slates. Hydrothermal alteration of the intrusions at Pulang includes five main types: K-silicate, epidote-chlorite, chlorite-illite, quartz-illite, and clay alteration.
K-silicate alteration, subdivided into early K-feldspar alteration and late biotite alteration dominantmainly affected the central quartz monzonite and adjacent coarse-grained quartz diorite and fine-grained quartz diorite.
Epidote-chlorite alteration, the most widespread alteration in the district, extends from the deposit core outward and has overprinted K-silicate alteration at South and North Pulang. Late chlorite-illite, quartz-illite, and clay alteration have overprinted preexisting K-silicate and epidote-chlorite alteration assemblages and are locally developed in all four intrusive phases.
“In this textbook, the author combines up-to-date scientific literature with well- structured Petrological and geochemical background to magmatic ore formation .. Some metals are extracted as trace components of ore minerals of .. combined with knowledge of local geology and geological history, on a much smaller. Read the latest articles of Ore Geology Reviews at bellasoulshop.com, Elsevier's W-Mo and Xiatongling W-Mo-Be deposits: Insights for the duration and cooling history Textural and trace element evolution of pyrite during greenschist facies .. for the LA-ICP-MS U-Pb dating of cassiterite” on the manuscript “Geological. Nevertheless, debate remains regarding the origin of ore-forming fluids, especially those .. U-Pb dating and trace elements of zircons.
Hypogene pyrrhotite is intergrown with chalcopyrite and mainly occurs in chlorite-illite-and quartz-illite-altered, coarse-grained quartz diorite at East Pulang.
Molybdenite Re-Os dating shows that mineralization in the district occurred at The sequence of intrusion emplacement, alteration and veining, and sulfide associations at the three deposits suggests that South and North Pulang are two separate porphyry Cu-Au deposits, whereas East Pulang is probably a distal part of South Pulang.
The pyrrhotite related to late chlorite-illite and quartz-illite alteration suggests local reduction due to interaction with the carbonaceous Tumugou slates. The atypical association of epidote-chlorite alteration and Cu mineralization at Pulang either is due to fluids from another porphyry deposit nearby overprinting epidote-chlorite alteration onto preexisting copper miner-alization and K-silicate alteration at Pulang or is the result of collapse of epidote-chlorite-stable fluids into the K-silicate-altered core during waning hydrothermal activity.
When compared to the duration of mineralization at other porphyry deposits worldwide, e.ORE GEOLOGY
The Re-Os and Ar-Ar geochronological age deter- minations from this study suggest that pulses of magmatism were short lived, and U-Pb age determinations from mineral- ized tonalites suggest porphyry mineralization persisted over at least 1.
Rachel L. Harrison Adi Maryono Malcolm S. Norris David S. The Tumpangpitu porphyry and high-intermediate-sulfidation epithermal deposit is the largest deposit in the Tujuh Bukit district, southeast Java, Indonesia. The porphyry resource contains 1.
There are an additional 2. At least eight discrete intrusions spanning the alteration-mineralization sequence have been identified at Tumpangpitu. What is unusual, however, is the presence of both a premineralization, relatively dry volcanic breccia pipe Tanjung Jahe and a late-mineralization diatreme complex associated with a significant, large magmatic-hydrothermal system Tumpangpitu in the same district.
Magmatism, mineralization, and alteration at Tumpangpitu occurred in response to north-directed subduction of the Indo-Australian plate beneath the Asian continental plate margin.
Dating and Tracing the History of Ore Formation
The Tujuh Bukit district is floored by early to late Miocene sedimentary and andesitic volcanic rocks. Volcanic-hydrothermal activity at Tujuh Bukit began with the formation of the weakly altered Tanjung Jahe diatreme complex U-Pbzircon ages of 8. Mineralization at Tumpangpitu was preceded by the intrusion of a large, equigranular, dioritic batholith 5.
Hydrothermal activity associated with mineralization has been constrained by U-Pb age determinations from syn- to late-mineralization porphyries that were emplaced in the early Pliocene from 5.
This suggests extreme rates of uplift, exhumation, and erosion in the vicinity of the Sunda-Banda magmatic arc. Volcanic-hydrothermal activity associated with the Tumpangpitu diatreme occurred during epithermal mineralization breccia matrix zircon age of 2.
Clasts of high-sulfidation state mineralized rocks are a minor but significant component of the diatreme, and late-stage epithermal veins cutting the diatreme demonstrate an intermineralization timing with respect to epithermal activity in the district, implying that epithermal mineralization continued intermittently for 1 to 1. Since the quartz vein system at Gameleira is partly hosted within, and appears to be directly related to, the underlying granite, this could indicate that the alkali feldspar granite at Gameleira is similar in age to the Pojuca Granite.
The Sm-Nd ages are calculated from whole-rock samples Pimentel et al. May Re-Os dating of molybdenite provides robust primary radiometric ages Stein et al. The after Madeisky, with location of the Lar porphyry Cu-Mo deposit igneous host rocks. Lar is a sub-economic porphyry Cu-Mo deposit with average grades of 0. The Cu-Mo mineralization developed in post-collisional shoshonitic syenitic to monzonitic intrusions in an Oligocene igneous complex known as the Lar Igneous Complex LIC.
The host and country rocks have undergone variable degrees of supergene and hypogene alteration including silicic, potassic, propylitic, phyllic, and argillic alteration. The Cu-Mo mineralization is mainly controlled by NNW striking faults and fractures, and occurs as quartz veins and veinlets, disseminated sulfides, and stockworks. The mineralization can be divided into two types: hypogene and supergene.
Hypogene mineralization is characterized by chalcopyrite, pyrite, bornite, molybdenite and magnetite, whereas supergene mineralization is characterized by enargite, covellite, chalcocite, digenite, malachite, azurite, and iron hydroxides. Sulfur isotope values for hypogene sulfides range from 0.
Re-Os dating of two molybdenite samples from two different drill holes yields dates of Our analyses indicate that the concentration of common Os in molybdenite from the Qar- achilar deposit is 0. However, compared with the Os value of The dated sample yielded a model age of Sep The open-system behaviour of the Re-Os isotope system in arseno- pyrite and other sulphides during metamorphism and overprinting fluid flow events was demonstrated by Stein et al.
Especially, mildly oxidizing hydro- thermal fluids may have an important effect on the Re-Os isotope sys- tems in sulphide minerals Stein, Repeated syn- and post-orogenic gold mineralization events between 1. 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 Pbisotope 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. This time-interval is concurrent with widespread granitoid emplacement at the close of the Svecofennian orogeny.
Disturbance of the Re-Os system in the early auriferous arsenopyrite can be connected to the late stage mineralizing processes. Pb isotope data suggest a mixed mantle and lower crust origin for fluids in the post-orogenic hydrothermal system. In situ U-Pb dating in polished thin sections in tandem with electron microprobe analyses of mineral compositions and detailed textural observations, highlights the utility of xenotime and monazite as robust geochronometers capable of recording repeated hydrothermal events in Paleoproterozoic orogenic systems.
Results provide precise temporal constraints for orogenic gold mineralization and vital information to refine the tectonic evolution of the Central Lapland Greenstone Belt. Constraining the timing and duration of magmatic-hydrothermal events is vital to understanding ore deposit formation, from both academic and economic viewpoints Stein, Petrogenesis of the Dasuji porphyry Mo deposit at the northern margin of North China Craton: Constrains from geochronology, geochemistry and isotopes characteristics.
Peiwen Chen. These ages are indistinguishable to the molybdenite Re—Os isochron age of The Dasuji granites show the petrological, mineralogical, geochemical, and geotectonic characteristics of A-type granites. In chondrite- and mantle-normalized trace element diagrams, all the granitic rocks show negative anomalies in Ba, Sr, and Eu, and a positive anomaly in Pb. These data are attributed to fractional crystallization processes.
Fractionation of feldspar, biotite, and possibly K-feldspar produced the variations in major elements and Rb, Sr and Ba, and the distribution of REE are controlled mainly by fractionation of zircon, allanite, minor apatite, and possibly a small quantity of monazite.
Together with the regional geology, the data infer that the Dasuji porphyry Mo deposit formed in a post-collision extensional setting during the Late Triassic. This radiometric clock has been widely used to date sulfide minerals from crustal e.
In addition, Re- Os isotopic ratios are used as geochemical tracers for identifying im- portant sinks, sources, or processes in high-and low-temperature geochemistry e. Precise and accurate measurements of the isotopic composition of rhenium Re in geologic samples are of paramount importance for the successful application of the Re-Os geochronometer.
Two methods for chemical isolation of Re are used in the geochronology community — column chemistry using anion exchange resin and solvent-solvent extraction using a sodium hydroxide-acetone mixture.
Despite their ubiquitous application, a systematic comparison of these two methods is missing. Here we compare Re-isotopic data on a variety of samples sulfides, hydrocarbons, shales, and in-house standard solutions that were processed by both chemical methods.
Standard solutions processed through column chemistry, however, preserve their natural Re isotopic composition. In contrast, the acetone-NaOH method produces more consistent Re isotopic results across the same range of sample types, Re loads and signal intensities. Thus, we recommend use of the acetone-NaOH solvent-solvent extraction procedure for low-Re samples, and provide a practical way to lower the typically higher Re blank supplied by NaOH.
Re-Os ages typically preserve the time of formation of molybdenite whereas Ar-Ar ages may be strongly affected by subsequent thermal events Selby et al. Berezina and Berzina presented whole-rock geo- chemical data for intrusive rocks from the Ak-Sug intrusive complex and adjacent Tannu-Ola series, but did not specify which intrusive phases are represented.
Paragenesis and re-os molybdenite age of the cambrian ak-sug porphyry cu-Au-mo deposit, tyva republic, Russian federation. The Ak-Sug intrusive complex is made up of a series of nested intrusions, including diorite, feldspar porphyry, quartz-feldspar porphyry, tonalite I, and tonalite II. Cu-Au-Mo mineralization occurs mainly within quartz-carbonate?
In the northern zone, sulfide zoning consists of a central bornite core flanked by chalcopyrite and pyrite-chalcopyrite zones, with a pyrite zone on the hanging-wall side. Re-Os molybdenite dating of an early-stage quartz-carbonate? This indicates an Early Cambrian age for mineralization at Ak-Sug, making it one of the oldest porphyry copper deposits in the Central Asian orogenic belt.
Published whole-rock geochemical data indicate that intrusive rocks at Ak-Sug and other Cambrian to Early Ordovician intrusive complexes in the Tuva-Mongol arc evolved by hornblende? Age and genesis of polymetallic veins in the Freiberg district, Erzgebirge, Germany: constraints from radiogenic isotopes.
The Freiberg mining district in the Erzgebirge hosts three principal types of polymetallic veins. These are 1 the quartz-bearing polymetallic sulfide type, 2 the carbonate-bearing polymetallic sulfide type, and 3 the barite-fluorite-sulfide type. We investigated the genesis of each vein-type using Rb-Sr sphalerite geochronology, Sm-Nd fluorite geochronology, and Pb, Sr, and Nd isotope systematics of ore and gangue minerals. The high mean squared weighted deviation MSWD value of 42 on the regression is considered to reflect initial isotopic heterogeneity, which is probably related to fluid-rock interaction during the hydrothermal mineralization process.
Although some sphalerites from barite-fluorite-sulfide veins have strongly disturbed Rb-Sr isotope systematics, six sphalerites and one co-genetic fahlore yield a robust isochron age of The new ages and radiogenic isotope data place robust constraints on the long-held hypothesis that veins in the Freiberg district formed during two hydrothermal events.
The Lower Permian age of first stage quartz-bearing polymetallic sulfide veins and carbonate-bearing polymetallic sulfide veins coincides with post-Variscan crustal reorganization and Rotliegend volcanism. The Mid-Cretaceous age of second stage barite-fluorite-sulfide veins coincides with opening of the North Atlantic Ocean during the break-up of Pangea. The Siah Kamar porphyry Mo deposit is the newly discovered deposit of this type in the Neo Tethys-related Urumieh—Dokhtar magmatic arc, northwest Iran.
Mineralization occurs as stock-work quartz—molybdenite and mono-mineralic molybdenite veinlets within the porphyry quartz-monzonite stock and the country rocks, accompanied by locally scattered later-stage and cross-cutting quartz-chalcopyrite-pyrite veinlets in the trachy-andesite and trachy-basalt country rocks.
U—Pb zircon geochronology of the porphyry stock yielded Early Oligocene dates of However, it is younger than the majority of the porphyry Cu deposits in the southern Lesser Caucasus and only shows temporal correlation with the Paragachay and first-stage Kadjaran porphyry Cu deposits. Moreover, it is older than all the porphyry Cu—Mo systems across the central and south-eastern parts of the Urumieh—Dokhtar magmatic arc, except the Bondar Hanza deposit, which is nearly coeval with the Siah Kamar porphyry Mo deposit.
All these data reveal an old to young trend along the UDMA and the porphyry Cu belt of Iran, further testifying to the diachronous and later closure of the Neo-Tethyan oceanic basin in central and SE Iran. Apr Miner Deposita.
Sediment-hosted stratiform ore deposits that underwent metamorphism and orogenesis are interpreted either to have a multiphase origin that might in part predate these events or to be exclusively related to fluid migration during the orogeny. This controversy concerns the formation of many world-class sediment-hosted ore deposits such as in the Central African Copperbelt. Here we present Re—Os dating results for disseminated and stratiform Cu—Co sulfide pseudomorphs after anhydrite in nodules and layers from the Copperbelt.
Results demonstrate that at least some of the ores formed at around Ma during rifting and basin development, and thus predate the Pan-African Lufilian orogeny. Younger Re—Os ages, i. This polyphase district provided c. It consists of mineralized quartz veins, silica-rich gneiss, pegmatites and aplites associated with a heterogeneous, locally sulphide-bearing, amphibolites facies gneiss called Knaben Gneiss, and hosted in a regional-scale monotonous, commonly weakly foliated, granitic gneiss.
This age links magmatism in the district to the regional — Ma Sirdal I-type granite suite, corresponding to voluminous crustal melting during the Sveconorwegian orogeny.
The rim records protracted hydrothermal activity, which started during the main magmatic event and outlasted it. This process was coeval with regional high-grade Sveconorwegian metamorphism.
Molybdenum deposition probably started during this event when silica-rich mineralizing fluids or hydrous magmas were released from granite magma batches.
An analogy between the Knaben district and shallow, short-lived porphyry Mo deposits is inappropriate. The Morococha district in central Peru is characterised by economically important Cordilleran polymetallic Zn-Pb-Ag-Cu vein and replacement bodies and the large Toromocho porphyry Cu-Mo deposit in its centre.
In the late Miocene, three individual magmatic-hydrothermal centres were active: the Codiciada, Toromocho, and Ticlio centres, each separated in time and space. The Codiciada centre is the oldest magmatic-hydrothermal system in the district and consists of a composite porphyry stock associated with anhydrous skarn and quartz-molybdenite veins. The hydrothermal events are recorded by a titanite U-Pb age at 9. These ages are indistinguishable from zircon U-Pb ages for porphyry intrusions of the composite stock and indicate a time span of 0.
The small Ticlio magmatic-hydrothermal centre in the west of the district has a maximum duration of 0. The Toromocho magmatic-hydrothermal centre has a minimum of five recorded porphyry intrusions that span a total of 1. At least two hydrothermal pulses are identified. These ages mark the end of the slowly cooling and long-lived Toromocho magmatic-hydrothermal centre soon after last magmatic activity at 7.
District-wide 50 km2 Cordilleran base metal vein and replacement bodies post-date the youngest recorded porphyry mineralisation event at Toromocho by more than 0. Polymetallic veins 5. Hydrothermal activity ceased after the formation of the base metal vein and replacement bodies.
Overlapping monazite U-Pb 8. These ages pre-date those of Toromocho porphyry Cu-Mo formation and show that Zn-Pb-Ag-Cu mineralisation formed during several discrete magmatic-hydrothermal pulses in the same district. Despite a wealth of research on the Kalahari Copperbelt over the past 30 years, two crucial aspects of the mineralizing systems have remained elusive.
First, the age of the rift sequence hosting the deposits and, second, the nature of the fluid pathways for the mineralizing fluids. Lu-Hf analysis of detrital zircon suggests that the Mesoproterozoic and Paleoproterozoic rocks of the Namaqua Sector and the Rehoboth Basement Inlier were the primary sediment sources for the siliciclastic rocks of the Ghanzi Group and lesser material was derived from the basin-bounding footwall margin of the northwest Botswana rift, the Paleoproterozoic Magondi Belt and the Okwa Block, and possibly parts of the Limpopo Belt on the northern margin of the Kalahari Craton in southern Africa.
High-resolution aeromagnetic maps were utilized to define the stratigraphy and structure of the Ghanzi Group of the central Kalahari Copperbelt. Maps of the second vertical derivative transformation were compared with detailed stratigraphic data from drill holes. Detailed facies architecture derived from both drilling and magnetic data at the Zone 5 Cu-Ag deposit, located east of the Kgwebe and Makgabana Hills, suggests that its physical stratigraphic and chemical organic material and in-situ bacteriogenic sulfide nature were influenced by the underlying basin architecture, which was critical in development of trap sites and in funneling epigenetic hydrothermal fluids into those traps.
The presented new data indicate that the basin architecture underlying the Kalahari Copperbelt strongly influenced the localization of deformation and hydrothermal fluid flow during epigenetic events. The results of this study can be used to help vector exploration for Cu-Ag deposits through the recognition of buried paleotopographic highs and associated favorable trap sites. Jun Anal Chem. Determining and correcting for background contributions of Re and Os from chemical reagents is critical for accurate and precise Re-Os dating of materials with parts per billion to parts per trillion Re and Os concentrations.
Here we investigate reducing Os content in nitric acid, as it is the main contributor to the Os blank. Pre-treating high-purity nitric acid with hydrogen peroxide H2O2 significantly reduces nitric acid's Os contribution to femtogram levels, greatly reducing Os blank corrections. The improvement in background Os allows analysis of samples with extremely low Os concentrations into the low ppt level.
We present experimental data identifying key factors in reducing Os blank, including nitric acid to hydrogen peroxide ratios, wet versus dry glassware, and dark versus lighted reaction environments. These variables affect the reaction time between the two reagents, which in turn correlates inversely with the final Os content. In contrast to Os, pre-treatment with hydrogen peroxide did not improve the Re blank of nitric acid; Re background reduction requires conventional methods such as sub-boiling distillation.
Neoproterozoic tin mineralization in South China: geology and cassiterite U—Pb age of the Baotan tin deposit in northern Guangxi. The Baotan tin deposit 23 Mt 0. Tin mineralization is mainly in the cassiterite greisen, cassiterite—tourmaline—quartz, and cassiterite—quartz vein stages.
The deposit is characterized by widespread tourmalinization. Both pre-ore and ore-stage tourmaline is schorl. These two dates are consistent with the previously reported zircon U—Pb ages of — Ma for the Pingying granite, which indicates that tin mineralization is related to the granite. Our study confirms the Neoproterozoic tin mineralization event in South China and indicates that the Neoproterozoic highly fractionated S-type granites in the southeastern margin of Yangtze Block have a great potential for tin mineralization.
Age of the Zambian Copperbelt. It has been widely accepted that the disseminated mineralization was introduced during sediment diagenesis in a rift setting, and possibly in multiple events spanning several hundred million years. In contrast, the veinlet-hosted mineralization is commonly thought to have been derived either by remobilization of the disseminated sulfides during the Lufilian collisional orogeny or introduced at broadly the same time s as the disseminated sulfides during diagenesis and subsequent orogeny.
The molybdenite ages for the disseminated stratiform mineralization at two localities do not support the notion of syndiagenetic Cu introduction. Highly Siderophile Element and Osmium signatures in non-cratonic basalt-hosted peridotite xenoliths: Unravelling the origin and evolution of the Post-Archean Lithospheric Mantle.
These transition elements show relative chemical inertness and high market values, which respectively earned them the additional names of noble metals and precious metals. Consequently, the HSE are thought to have been efficiently sequestered within the metallic core of our planet during the metal—silicate differentiation of Earth, leaving the silicate counterpart almost HSE-barren.
Investigations of mantle peridotites since the s revealed ng. Such abundances and inter-HSE fractionations are not predicted for the silicate Earth left after separation of the metallic core for low- or high-pressure core—mantle differentiation see Brenan et al.
The close agreement between the osmium isotopic compositions of fertile mantle peridotites and those of chondritic meteorites Walker et al. Our new Re-Os data, together with previous studies, identify four distinct hydrothermal events at the Lala deposit.
Our results indicate that the Lala deposit formed during multiple, protracted mineralization events over several hundred million years. The first three Mesoproterozoic mineralization events are coeval with intra-continental rifting breakup of the supercontinent Nuna and share a temporal link to other IOCG-style deposits within the Kangdian Copper Belt, and the last Neoproterozoic hydrothermal event is coeval with the Sibao orogeny which culminated with the amalgamation of the Yangtze Block with the Cathaysia Block at — Ma.
Dating and tracing the history of ore formation
Rhenium uptake and distribution in phaeophyceae macroalgae, Fucus vesiculosus. Owing to Rhenium Re having no known biological role, it is not fully understood how Re is concentrated in oil kerogens.
A commonly held assumption is that Re is incorporated into decomposing biomass under reducing conditions. However, living macroalgae also concentrate Re to several orders of magnitude greater than that of seawater.
This study uses Fucus vesiculosus to assess Re uptake and its subsequent localization in the biomass. It is demonstrated that the Re abundance varies within the macroalgae and that Re is not located in one specific structure. A positive correlation is shown between the concentration of Re-doped seawater and the abundance of Re accumulated in the tips. However, significant differences between Re VII compounds are observed. Although the specific cell structures where the Re is localized is not known, our findings suggest that Re is not held within chloroplasts or cytoplasmic proteins.
In addition, metabolically inactivated F. The Paleoproterozoic Cu-Au deposits are commonly hosted within Neoarchean IOCG alteration systems and the common occurrence of potassic alteration especially biotite in both types of deposits means that special care is required in interpreting the paragenesis of alteration in both types of deposits.
The Paleoproterozoic Cu-Au deposits are reduced, and sulfur- and quartz-rich deposits lacking in major amounts of iron oxides and are therefore unlike IOCG deposits. However, there is increasing evidence for the occurrence of porphyry deposits related to magmas generated after the underplating arc has ceased. Post-subduction lithospheric thickening, lithospheric extension, or mantle lithosphere delamination could trigger the remelting of subduction-modified arc lithosphere and lead to the formation of post-subduction porphyry deposits.
The NNW-trending Yidun Terrane, located in the eastern Tethys, experienced subduction of Garze—Litang oceanic plate a branch of the Paleotethys in the Late Triassic and witnessed two mineralization events respectively associated with the ca.
It is, therefore, an ideal place to investigate the genetic linkage between the subduction-related porphyry deposits and post-subduction porphyry deposits. Our new in situ zircon U—Pb dating of the two granitic intrusions biotite granite, Furthermore, the arc-like elemental signatures and the mixed Sr—Nd—Hf isotopic signatures of the Late Cretaceous ore-related porphyries i.
This suggests that the remelting of underplated arc-related mafic rocks formed during the subduction of the Garze—Litang Ocean could be responsible for the mixing between the mantle-derived components and the Mesoproterozoic lower crustal materials, when post-subduction transextension occurred in the Late Cretaceous.
The formation of the Late Cretaceous porphyry—skarn Cu—Mo—W deposits could most likely be related to the remelting of Late Triassic residual sulfide-bearing Cu-rich cumulates in the subduction-modified lower crust that triggered by the Late Cretaceous transtension.
Jun The Re-Os model ages for the molybdenites range between and Ma and apparently correspond to the early stages of metamorphism connected with pre-Variscan rift-related tectono-metamorphic events, which affected and recrystallized sedimentary CLM material rich in Mo-Th-Nb-REE.
There is no geological evidence for the participation of fluids mobilized from host rocks in the formation of the CLM. Because the Re-Os chronometer in molybdenite is demonstrably stable through later Variscan facies metamorphism, the molybdenite chronometer has not been affected by subsequent thermal overprints associated with the Variscan orogeny.
Show more. Regional-scale Cretaceous albitization in the Pyrenees: evidence from in situ U-Th-Pb dating of monazite, titanite and zircon. Albitization is a common metasomatic process active in various geodynamic contexts. In the northern Pyrenees, there are several occurrences of albitites but, until now, only one occurrence has been dated Ma, Ar-Ar dating. This paper presents new U-Th-Pb ages for several albitite occurrences throughout the Pyrenees to test whether they are contemporaneous and, if so, to specify the regional extent of the albitization event.
The zircon U-Th-Pb isotopic system did not record this Cretaceous metasomatic event, even when grains were selected in metasomatically Zr-enriched rocks or in hydrothermal structures millimetre-sized veins cross-cutting granitoids.
We argue that the total time span of 20 Ma recorded by albitites corresponds to a long-lived hydrothermal system that was active during the rotation of Iberia around Europe, along the North Pyrenean Fault. Because albitization and talc mineralization have the same spatial and temporal distribution in the Pyrenees, we argue that these two metasomatic phenomena are two independent records of this single, regional-scale, long-lived hydrothermal system.
Skarn deposits are an abundant ore type and represent a globally can track the fluid–rock interaction history and provide a continuous. Article history . In contrast, the ages of other magmatic-hydrothermal ore deposits are still poorly . In situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) trace element analysis of molybdenite. over the last decades (see detailed history in Davis et al. ; Corfu . temperature events that that post-date ore formation, allowing a fuller U–Pb dating should be homogenous in age, trace element composition, and have comparable.
Zircon tiny but timely: Hydrothermal zircons. Primitive Os and Ma age for marine shale: implications for Paleoproterozoic glacial events and the rise of atmospheric oxygen.
scheelite; Sm-Nd dating; trace elements; Sb-Au deposit; Longshan and ore- forming fluids in these deposits were magmatic in origin .
These units were deposited between what are interpreted as the second and third of three Paleoproterozoic global glacial events, and thus provide minimum and maximum ages, respectively, for these events. The Rooihoogte Formation is correlative with the Duitschland Formation, which records previously undated carbon isotope excursions. Because the pyrite samples show no evidence of mass independent fractionation of sulfur and have highly negative delta 34 S values, the rise of atmospheric oxygen most likely began prior to 2.
Os is mobile only under oxidizing conditions. Even if atmospheric oxygen levels had increased significantly by 2. Reproducibility of Re-Os molybdenite ages depends on sample size and homogeneity, suggesting that Re and Os are decoupled within individual molybdenite crystals and do not remain spatially linked over time.
Experimentation with mineral separations and sample size over a 7-yr period predicted that this would be the outcome. We suggest that Os is more likely to be the mobile species, based on its charge and ionic radius, and that Os becomes decoupled from parent Re with time on the micron and larger scale.
Incompatible charge and ionic radius for Os ions formed during reduction of molybdenite-forming fluids may explain the widely observed absence of common initial Os in molybdenite. Geologically accurate ages for molybdenite can only be obtained for fully homogenized crystals or crystal aggregates so that any post-crystallization ReOs decoupling is overcome.
A growing number of geologically accurate ID-NTIMS ReOs ages for homogenized molybdenite suggest that postcrystallization mobility of radiogenic Os must be limited to within the molybdenite mineral phase. We suggest that radiogenic Os may be stored in micron scale dislocations, kink bands, and delamination cracks produced by deformation, and that the unusual structure and deformation response of molybdenite results in an increased chemical stability in this mineral.
Migration Of Os into adjacent silicate phases is highly unlikely, but other contacting sulfides may take in Os. In an example from a Proterozoic skarn deposit at Pitkaranta western Russiawe demonstrate minor loss of radiogenic Os from molybdenite and a corresponding gain in adjacent chalcopyrite such that the molybdenite age is not perceptibly disturbed, whereas the resulting chalcopyrite ages are impossibly old. Therefore, it is unadvisable to perform Re-Os analytical work on any sulfide in contact or intimate association with molybdenite.
Copyright C Elsevier Ltd. Geology and exploration progress at the Resolution porphyry Cu-Mo deposit, Arizona.
Carl Hehnke G. Theories of ore deposition historically considered. Leonora gold camp: 2. Atlas of zircon textures. Fernando Corfu. A study of the rhenium-osmium geochronometry of molybdenites.
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