Lead isotopes in the Grenville and adjacent Palaeozoic formations

1977 ◽  
Vol 14 (1) ◽  
pp. 56-66 ◽  
Author(s):  
Ian R. Fletcher ◽  
R. M. Farquhar
Keyword(s):  
New York ◽  
Lead Isotope ◽  
Lead Isotopes ◽  
Ore Deposits ◽  
Evolution Model ◽  
Isotopic Ratios ◽  
Southern Ontario ◽  
Critical Questions ◽  
Lead Isotope Ratios ◽  
And Migration

Lead-isotope ratios have been determined for a preliminary set of 16 galenas from the Grenville and some adjacent Palaeozoic formations in southern Ontario and Quebec. The 206Pb/204Pb ratios of the Grenville-hosted deposits range from 16.24 to 20.20. Six of the Grenville-hosted samples have a post-Ordovician age of mineralization, but may represent re-mineralized Grenville lead. With the five 'true' Grenville samples they can be used to define a Grenville 'secondary isochron' on a 207Pb/204Pb–206Pb/204Pb plot. The trend of this isochron appears to be consistent with published feldspar- and marble-lead data for nearby sections of the Grenville. Its slope (.120 ±.015) is compatible with a time of ~1300 Ma ago for inclusion of uranium in the sediments of the Grenville supergroup, followed by lead mineralization at ~1000 Ma. Calculations based on a simple lead-isotope evolution model give a similar age (1280 ± 15 Ma) for the stratabound Tétrault Pb–Zn deposit.The geologically similar New Calumet deposit has a quite different model age of 1115 ± 20 Ma. This is similar to the model age of the Balmat, New York ore deposits and it appears that New Calumet and Balmat may be members of a contemporaneous mantle (volcanic)–continental sequence.An apparent correspondence of the isotopic ratios of the Palaeozoic samples with the Grenville secondary isochron raises some critical questions regarding the development and migration of the Pb in these deposits.

Lead- and strontium-isotope geochemistry of Paleozoic Sicker Group and Jurassic Bonanza Group volcanic rocks and Island Intrusions, Vancouver Island, British Columbia

1989 ◽  
Vol 26 (5) ◽  
pp. 894-907 ◽  
Author(s):  
Anne Andrew ◽  
Colin I. Godwin
Keyword(s):  
Lead Isotope ◽  
Isotope Geochemistry ◽  
Lead Isotopes ◽  
Volcanic Rocks ◽  
Isotope Ratios ◽  
Ore Deposits ◽  
Island Arc ◽  
Lead Isotope Ratios ◽  
Rock Suite ◽  
Isotope Analyses

Whole-rock and galena lead-isotope analyses have been obtained from the Sicker Group Paleozoic island-arc volcanic package and from a Jurassic island-arc represented by the Bonanza Group volcanics and Island Intrusions. Galena lead-isotope analyses from the volcanogenic ore deposits at the Buttle Lake mining camp in the Sicker Group provide estimates of the initial lead ratios for the Sicker Group. Lead-isotope signatures are uniform within each of the major orebodies, but the Myra orebody is less radiogenic than the older H–W orebody. This has major significance in terms of ore genesis for these important deposits.There are significant differences in isotopic composition between the Sicker Group and Devonian island-arc type rocks in the Shasta district, California, which rules out direct correlations between the rock units of these two areas. Relatively high initial values of 207Pb/204Pb (> 15.56) and 208Pb/204Pb (> 38.00) suggest that large quantities of crustal lead must have been involved in the formation of the Sicker Group volcanic rocks. Thus it is proposed that the trench related to the Paleozoic island arc had a substantial input of continental detritus and may have lain near a continent.The Jurassic island arc is characterized by low 207Pb/204Pb ratios (< 15.59), suggesting a more primitive arc environment than for the Paleozoic arc. Bonanza Group volcanic rocks contain lead that is less radiogenic than lead in the Island Intrusions. Present and initial lead-isotope ratios of both the Bonanza Group volcanics and Island intrusions follow the same trend, supporting the hypothesis that they are comagmatic. Lead isotopes from a galena vein within the Island Copper porphyry deposit plot with the initial ratios for Bonanza Group volcanics and Island Intrusions. This confirms the hypothesis that this mineralization is related to the Jurassic island-arc volcanic event.Initial lead-isotope ratios for the Jurassic rock suite form a linear array on both 207Pb/204Pb versus 206Pb/204Pb and 208Pb/204Pb versus 206Pb/204Pb plots. If interpreted as due to isotopic mixing, the more radiogenic end member has a composition that is lower in 207Pb/204Pb and higher in 206Pb/204Pb than typical upper continental crust. Assimilation of Sicker Group material during the emplacement of the Jurassic arc can explain the mixing trend.

LEAD ISOTOPE RATIOS FROM THE COBALT–NORANDA AREA, CANADA

1965 ◽  
Vol 2 (4) ◽  
pp. 361-384 ◽  
Author(s):  
E. R. Kanasewich ◽  
R. M. Farquhar
Keyword(s):  
Lead Isotope ◽  
Source Region ◽  
Isotope Ratios ◽  
Single Stage ◽  
Isotopic Ratios ◽  
Crustal Rocks ◽  
Lead Isotope Ratios ◽  
Relationship Of ◽  
The Relationship ◽  
Lead Line

Lead isotope ratios indicate that very old galenas in Archean volcanics and sediments in the vicinity of Timmins, Ontario; Noranda and Val d'Or, Quebec, have had additions of younger lead of the type found near Cobalt, Ontario. The mixture of leads of two distinct ages has produced isotopic ratios which are linearly related. The greatest degree of mixing has occurred in areas such as Kirkland Lake which are close to the boundary between Archean rocks and the Bruce–Cobalt Series. Most of the lead appears to have been derived from a subsialic source region. From the relationship of the anomalous lead line and the single-stage growth curve commonly accepted for ordinary leads it is found that lead sulfide mineralization occurred 3 250 ± 150 million years (m.y.) ago in Archean rocks of Ontario and Quebec. The leads associated with mines along the northeastern edge of the Cobalt basin were separated from their uranium and thorium source region 2 300 ± 150 m.y. ago. Leads from Chibougamau, Quebec, appear to be related in age to the Cobalt leads. This study of 50 lead isotope ratios is a clear illustration of the claim that single-stage lead models must not be applied indiscriminately to isolated analyses of galena. It also produces evidence for the existence of crustal rocks in North America prior to 3 200 m.y. ago.

Lead Isotope Studies of Rock Samples from the Superior Geological Province

1971 ◽  
Vol 8 (4) ◽  
pp. 444-454 ◽  
Author(s):  
J. M. Ozard ◽  
R. D. Russell
Keyword(s):  
Standard Deviation ◽  
Lead Isotope ◽  
Lead Isotopes ◽  
Internal Standard ◽  
Lake Area ◽  
Single Filament ◽  
Lead Isotope Ratios ◽  
Rock Samples ◽  
Isotope Studies ◽  
Isotope Analyses

Single filament whole rock lead isotope analyses were corrected for fractionation by using an internal standard (double spike). An estimated standard deviation of 0.15% was obtained for lead isotope ratios and 0.25% for lead and uranium concentrations. These are some of the first analyses of this accuracy for lead isotopes in whole rocks. Lead and uranium analyses from the Vogt–Hobbs area near Lake Timagami, Ontario and from the Rice Lake – Beresford Lake area, Manitoba gave ages with the pattern lead–lead age > uranium 235 – lead 207 age > uranium 238 – lead 206 age. This pattern was interpreted as arising from loss of lead from the systems studied. A similar three-stage history, marked by major events prior to 3000 m.y. ago and at approximately 2600 m.y. ago, fits both of these suites. This history is shown to be consistent with rubidium–strontium data, zircon uranium–lead ages, potassium–argon, and ore lead data.

scholarly journals Determination of Lead Elemental Concentration and Isotopic Ratios in Coal Ash and Coal Fly Ash Reference Materials Using Isotope Dilution Thermal Ionization Mass Spectrometry

2019 ◽  
Vol 16 (23) ◽  
pp. 4772 ◽  
Author(s):  
Chaofeng Li ◽  
Huiqian Wu ◽  
Xuance Wang ◽  
Zhuyin Chu ◽  
Youlian Li ◽  
...  
Keyword(s):  
Lead Isotope ◽  
Thermal Ionization Mass Spectrometry ◽  
Environmental Science ◽  
Coal Fly Ash ◽  
Lead Isotopes ◽  
Coal Ash ◽  
Isotope Ratios ◽  
Ionization Mass ◽  
Pb Isotope ◽  
Lead Isotope Ratios

The rapid expansion of coal-fired power plants around the world has produced a huge volume of toxic elements associated with combustion residues such as coal fly ash (CFA) and coal ash (CA), which pose great threats to the global environment. It is therefore crucial for environmental science to monitor the migration and emission pathway of toxic elements such as CFA and CA. Lead isotopes have proved to be powerful tracers capable of dealing with this issue. Unfortunately, up to now, few high precision lead isotope data of CFA and CA certified reference materials (CRMs) determined by using the double spike technique have been reported. Hence, to facilitate the application of lead isotopes in environmental science, it is indispensable and urgent to determine a suite of high precision Pb isotope ratios and Pb elemental contents for CFA and CA CRMs. Here, we measured lead isotope ratios from four CFA and CA CRMs using thermal ionization mass spectrometry (TIMS) combined with the 204Pb–207Pb double spike method. Lead isotope ratios values of CRMs (GBW11124, GBW08401, GBW11125d, and JCFA-1) covered wide variation ranges from 17.993 to 19.228 for 206Pb/204Pb, from 15.513 to 15.675 for 207Pb/204Pb, and from 38.184 to 39.067 for 208Pb/204Pb. Lead isotope ratios of these CRMs, except for GBW11124, show good external reproducibility (2 RSD, n = 8), which is better than 0.05% for 206Pb/204Pb and 207Pb/204Pb, 0.07% for 208Pb/204Pb, 0.04% for 206Pb/207Pb, and 0.05% for 208Pb/206Pb. The Pb concentrations of these CRMs were determined using 207Pb single spike method. The reproducibility (1 RSD, n = 4) of Pb elemental content was <0.60%. This indicates the distribution of Pb elements in these CRMs is homogeneous. With the exception of GBW11124, the suite of CRMs can be used for determining CFA and CA matrix composition for quality control of Pb isotope analyses.

Isotopic composition of lead from a paleo-island arc: Shasta, California

1983 ◽  
Vol 20 (10) ◽  
pp. 1521-1527
Author(s):  
W. F. Slawson
Keyword(s):  
Isotopic Composition ◽  
Lead Isotope ◽  
Linear Array ◽  
Linear Trend ◽  
Lead Isotopes ◽  
Isotopic Ratios ◽  
The West ◽  
Geochemical Tracers ◽  
Good Linear ◽  
Isotope Analyses

Twelve new lead isotope analyses of samples from the West and East Shasta districts, California are presented. The measured isotopic ratios 206Pb/204Pb versus 207Pb/204Pb exhibit a good linear trend with a slope of 0.1794 ± 0.0066. Arguments are presented that the two-stage ages calculated from this slope are not real events. It is suggested the linear array is due to fortuitous addition of contaminants to the volcanogenic mineralizations. Thus common lead isotopes are possibly better geochemical tracers than they are geochronometers. This may be particularly true in cases where the total lead content is low.

Untold stories: Jamaican transnational mothers in New York City

2018 ◽  
Vol 7 (4) ◽  
pp. 409-432
Author(s):  
Derrace Garfield McCallum
Keyword(s):  
New York ◽  
New York City ◽  
Gender Stereotypes ◽  
York City ◽  
Cultural Norms ◽  
Transnational Mothers ◽  
Women's Lives ◽  
International Labour Migration ◽  
And Migration ◽  
Societal Expectations

AbstractGlobalization and contemporary international labour migration continue to transform women’s lives. Moreover, gender stereotypes, biased cultural norms, biological responsibilities and economic marginalization serve to constrain women disproportionately, particularly mothers. Indeed, globalization and migration increases existing pressures associated with motherhood. They intensify societal expectations of women, and often result in extreme distress. Many transnational mothers suffer in silence with little or no chance to share their stories and be heard. This study explores the experiences of Jamaican transnational mothers in New York City and documents their stories in light of current research which investigates how transnational motherhood transgresses gender stereotypes and pushes the boundaries of gender roles and expectations. The stories shared in this paper vividly capture the women’s narratives of loss, longing, empowerment and shared responsibilities across borders.

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