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A V Chugaev - One of the best experts on this subject based on the ideXlab platform.
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contribution of crustal and mantle sources to genesis of sn b and pb zn deposits in south sikhote alin subprovince russian far east evidence from high precision mc icp ms Lead Isotope study
Ore Geology Reviews, 2020Co-Authors: A V Chugaev, I V Chernyshev, V V Ratkin, V G Gonevchuk, O A EliseevaAbstract:Abstract South Sikhote-Alin metallogenic subprovince (SSAP) is located in the southern part of the Sikhote-Alin orogenic belt. It encompasses more than one hundred well-known deposits and occurrences of boron, tin, Lead, and zinc. These deposits have been genetically related to the Late Cretaceous and Paleocene granitoid magmatism. Pb Isotope composition was measured using the MC-ICP-MS method in 20 SSAP deposits. Pb Isotope ratios (48 samples of galena) vary within narrow limits: 206Pb/204Pb ranges from 18.321 to 18.474, 207Pb/204Pb − 15.608–15.655, and 208Pb/204Pb 38.601–38.796. The high degree of homogeneity of the Pb Isotope composition and absence of correlations between the Lead Isotope characteristics of the deposits, on the one hand, and the age and type of ore mineralization, on the other, indicate the presence of a regional uniform Pb source for all the SSAP deposits. The results of Pb-Pb studies of the different rocks of the SSAP suggest that the source was most likely the Mesozoic sedimentary sequences of the Sikhote-Alin accretionary complexes. In turn, individual Lead Isotope characteristics of the SSAP deposits are caused by varibale contribution of mantle source to the overall balance of Lead.
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Lead Isotope systematics of porphyry epithermal spectrum of the birgilda tomino ore cluster in the south urals russia
Ore Geology Reviews, 2017Co-Authors: Olga Yu Plotinskaya, A V Chugaev, Reimar SeltmannAbstract:Abstract The paper provides the first data on Lead isotopic composition of porphyry and epithermal mineralization of the Birgilda-Tomino ore cluster. Lead Isotope characteristics were obtained for 24 sulfide samples representing epithermal Au-Ag (Bereznyakovskoe ore field and Michurino occurrence), base-metal carbonate replacement (Biksizak occurrence), porphyry copper (Tomino, Kalinovskoe, and Birgilda deposits), and four plagioclase samples of the Birgilda-Tomino Igneous Complex. Ore samples have Lead isotopic signatures similar to neighboring intrusions of the Birgilda-Tomino igneous complex and this confirms genetic relations between epithermal Au-Ag, base-metal carbonate replacement and porphyry copper mineralization with diorite porphyry intrusions. Variations in Lead isotopic composition are caused by mixing of mantle and crustal Lead sources. The input of radiogenic 206 Pb took place during the post-ore phase as a result of a series of tectono-magmatic events, which include emplacement of at least two phases of the Chelyabinsk pluton. The latter however could act only as a trigger of hydrothermal activity but not as a Lead source.
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Lead Isotope ore provinces of eastern transbaikalia and their relationships to regional structures results of high precision mc icp ms study of pb Isotopes
Geology of Ore Deposits, 2013Co-Authors: A V Chugaev, I V Chernyshev, N S Bortnikov, V A Kovalenker, G D Kiseleva, Yu V ProkofevAbstract:Lead isotopic composition was studied at 12 deposits of eastern Transbaikalia, which differ in type and scale of mineralization. The high-precision Pb-Pb data obtained using multicollector inductively coupled plasma mass-spectrometry allowed us to outline two large Lead Isotope provinces spatially coinciding with the West Stanovoi and Argun tectonic blocks. The difference in Pb isotopic composition of deposits in these provinces indicates that regional ore sources contrasting in geochemistry took part in ore formation. In the deposits at the southern margin of the West Stanovoi Block with predominance of Au and Mo mineralization, the Lead role is played by a mixed mantle-type source, whereas the source of Lead in the deposits of the Argun Block has U-Th-Pb isotopic characteristics inherent to a continental crust of orogenic type.
Martin S Appold - One of the best experts on this subject based on the ideXlab platform.
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Lead Isotope geochemistry of mississippi valley type deposits of the southern appalachians
Economic Geology, 1994Co-Authors: Stephen E Kesler, George L Cumming, Dragan Krstic, Martin S AppoldAbstract:Lead Isotope compositions of sphalerite, fluorite, barite and sparry dolomite in Mississippi Valley-type deposits of the southern Appalachians fall into four different isotopic groups. Most sphalerite forms two small clusters, whereas barite, fluorite, and sparry dolomite compositions are more scattered. These Lead Isotope compositions reflect the distribution of the deposits, which are hosted by two main palcoaquifers. Lower Cambrian clastic and carbonate rocks host the Austinville (Zn-Pb), Cartersville (Ba), Embreeville (Zn), and Doughtery (Zn) deposits, all of which fall in a cluster of Lead Isotope compositions near 207 Pb/ 204 Pb = 15.73 and 206 Pb/ 204 Pb = 19.45. Lower Ordovician carbonate rocks of the Knox Group host the Copper Ridge (Zn), Eve Mills (Zn), Greeneville-Fall Branch (Ba-F), Mascot-Jefferson City (Zn), Powell River (Zn-Pb), Russell-Tazewell (Ba-F), and Sweetwater (Ba-Zn-F) deposits, which have more complex compositions. Sphalerite from Mascot-Jefferson City, Eve Mills, Sweetwater, and Russell-Tazewell plots in a cluster around 207 Pb/ 204 Pb = 15.67 and 206 Pb/ 204 Pb = 19.0, whereas that from Copper Ridge plots in both clusters. Fluorite from Sweetwater falls on a long array in 207 Pb/ 204 Pb- 206 Pb/ 204 Pb space that has a two-stage age of 1.55 to 1.9 Ga for t 2 = 360 Ma, the previously published 87 Sr/ 86 Sr isochron age obtained for the Mascot-Jefferson City district. Barite and sparry dolomite compositions are relatively similar and have lower 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios than most sphalerite and fluorite. The spatial distribution of Lead Isotope compositions indicates that there were at least two mineralizing solutions, represented by the two Lead clusters; the upper cluster solution dominated the Lower Ordovician palcoaquifer whereas the lower cluster dominated the Lower Cambrian palcoaquifer; and that the two solutions mixed in most areas except the Mascot-Jefferson City district, where zinc mineralization is strongest. Although the specific sources of these Leads cannot be determined from available data on possible source rocks, the two Lead clusters probably came from relatively young, well-mixed sedimentary basins and the Lead in the fluorite must have come from a source with an unusally high U/Th ratio such as phosphoritc. This study confirms that the isotopic composition of Lead in southern Appalachian Mississippi Valley-type deposits differs significantly from that found in mid-continent deposits.
Stephen E Kesler - One of the best experts on this subject based on the ideXlab platform.
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Lead Isotope geochemistry of mississippi valley type deposits of the southern appalachians
Economic Geology, 1994Co-Authors: Stephen E Kesler, George L Cumming, Dragan Krstic, Martin S AppoldAbstract:Lead Isotope compositions of sphalerite, fluorite, barite and sparry dolomite in Mississippi Valley-type deposits of the southern Appalachians fall into four different isotopic groups. Most sphalerite forms two small clusters, whereas barite, fluorite, and sparry dolomite compositions are more scattered. These Lead Isotope compositions reflect the distribution of the deposits, which are hosted by two main palcoaquifers. Lower Cambrian clastic and carbonate rocks host the Austinville (Zn-Pb), Cartersville (Ba), Embreeville (Zn), and Doughtery (Zn) deposits, all of which fall in a cluster of Lead Isotope compositions near 207 Pb/ 204 Pb = 15.73 and 206 Pb/ 204 Pb = 19.45. Lower Ordovician carbonate rocks of the Knox Group host the Copper Ridge (Zn), Eve Mills (Zn), Greeneville-Fall Branch (Ba-F), Mascot-Jefferson City (Zn), Powell River (Zn-Pb), Russell-Tazewell (Ba-F), and Sweetwater (Ba-Zn-F) deposits, which have more complex compositions. Sphalerite from Mascot-Jefferson City, Eve Mills, Sweetwater, and Russell-Tazewell plots in a cluster around 207 Pb/ 204 Pb = 15.67 and 206 Pb/ 204 Pb = 19.0, whereas that from Copper Ridge plots in both clusters. Fluorite from Sweetwater falls on a long array in 207 Pb/ 204 Pb- 206 Pb/ 204 Pb space that has a two-stage age of 1.55 to 1.9 Ga for t 2 = 360 Ma, the previously published 87 Sr/ 86 Sr isochron age obtained for the Mascot-Jefferson City district. Barite and sparry dolomite compositions are relatively similar and have lower 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios than most sphalerite and fluorite. The spatial distribution of Lead Isotope compositions indicates that there were at least two mineralizing solutions, represented by the two Lead clusters; the upper cluster solution dominated the Lower Ordovician palcoaquifer whereas the lower cluster dominated the Lower Cambrian palcoaquifer; and that the two solutions mixed in most areas except the Mascot-Jefferson City district, where zinc mineralization is strongest. Although the specific sources of these Leads cannot be determined from available data on possible source rocks, the two Lead clusters probably came from relatively young, well-mixed sedimentary basins and the Lead in the fluorite must have come from a source with an unusally high U/Th ratio such as phosphoritc. This study confirms that the isotopic composition of Lead in southern Appalachian Mississippi Valley-type deposits differs significantly from that found in mid-continent deposits.
Merce Corbella - One of the best experts on this subject based on the ideXlab platform.
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sulfur and Lead Isotope systematics implications for the genesis of the riopar zn fe pb carbonate hosted deposit prebetic zone se spain
Ore Geology Reviews, 2017Co-Authors: Didac Navarrociurana, Esteve Cardellach, Elena Vindel, Albert Griera, David Gomezgras, Merce CorbellaAbstract:Abstract The Zn-(Fe-Pb) deposits of the Riopar area (Prebetic Zone, SE Spain) are hosted by dolostones that replace Berriasian to Valanginian (Upper Jurassic-Lower Cretaceous) limestones. Mineralization consists of hypogene sphalerite, marcasite and galena, and supergene calamine zones. The hypogene ores are associated with a saddle dolomite gangue. The ore bodies occur as discordant and stratiform lenses, ore-cemented breccias, cm- to mm-wide veins and veinlets, disseminations and stylolite porosity filling within the host dolomites. The main ore controls include stratigraphy and/or lithology, tectonics (faults, fractures and breccias) and availability of metals and sulfur. The morphologies and epigenetic character of the hypogene ore bodies are consistent with the classification of this mineralization as a Mississippi Valley-type (MVT) deposit. The Ga/Ge geothermometer in sphalerite yielded a temperature range of 194–252 °C, which represents the temperature of the source region of the ore solution. This value is comparable to the temperature obtained in the ore deposition site, 159 ± 15 °C from the Δ 34 S geothermometer in sphalerite galena pairs. This similitude points to a hydrothermal fluid that did not cool down significantly during flow from the fluid reservoir area to the precipitation site. δ 34 S values of base-metal sulfides (−7.5 to +3.5‰) are consistent with thermochemical reduction of Triassic sulfate (seawater and/or derived from dissolution of evaporites) by interaction with organic compounds (e.g., hydrocarbons, methane), which reduced sulfate to sulfide in the deposition site. The Lead Isotope ratios ( 206 Pb/ 204 Pb = 18.736–18.762; 207 Pb/ 204 Pb = 15.629–15.660; 208 Pb/ 204 Pb = 38.496–38.595) of galena suggest that Pb, and probably other metals as Zn, is derived from continental crustal rocks. On the other hand, these relations points to a unique metal source probably derived from the Paleozoic basement rocks. The relationship between bedding-parallel stylolites, dolomitization, sulfide precipitation and Alpine tectonic affecting the MVT ore, suggests a relative timing range for the mineralization in the Riopar area of 95–20 Ma (Upper Cretaceous-Tertiary). The sulfide mineralization and the associated dolomitization are thus explained by the contribution of two fluids that mixed in different proportions during dolomitization and mineralization: i) a fluid probably derived from Cretaceous seawater saturating Mesozoic sediments (Fluid A), characterized by being dilute and initially low temperature, which should have contained organic rich compounds in the ore deposition site (e.g., hydrocarbons and CH 4 dissolved gas); and ii) a high salinity hydrothermal brine (Fluid B) rich in both metals and sulfate, circulated through the Paleozoic basement. During the pre-ore dolomitizing stage the fluid phase was dominated by the diluted fluid (Fluid A > Fluid B), whereas in a later fluid pulse, the proportion of the high salinity fluid increased (Fluid A
Barry C Grant - One of the best experts on this subject based on the ideXlab platform.
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Lead Isotope analysis of marine carbonates and seawater by multiple collector icp ms
Chemical Geology, 2003Co-Authors: Matthew K Reuer, Edward A Boyle, Barry C GrantAbstract:Abstract A consistent method for stable Lead Isotope analysis of marine carbonates and seawater is presented, utilizing multiple collector ICP-MS (MC-ICP-MS). This study presents new observations of the large (0.7% amu−1), time-dependent mass bias determined by thallium normalization, including preferential light ion transmission induced by the acceleration potential and plasma interface (β=−1.3 to 0.9). These experiments show equivalent results for three empirical correction laws, and the previously proposed βPb/βTl correction does not improve Isotope ratio accuracy under these conditions. External normalization to SRM-981 following the thallium correction provides one simple alternative, and a rationale is provided based on secondary bias effects. With current intensities less than 1.5×10−12 A, external Isotope ratio precision better than 250 ppm for SRM-981 207Pb/206Pb and 208Pb/206Pb ratios is observed (2σ). From reconstructed Lead isotopic variability in the North Atlantic, this instrumental precision results in a signal-to-noise ratio greater than 100. Matrix effects are significant with concomitant calcium in SRM-981 (−280 ppm at 257 μM [Ca]). With the appropriate corrections and minimal concomitants, MC-ICP-MS can reliably determine 207Pb/206Pb and 208Pb/206Pb ratios of marine carbonates (30 mg) and seawater (160–200 g).