The Application of Lead Isotopes to the Problems of Ore Genesis and Ore Prospect Evaluation: A Review

Abstract

Lead isotope data are now available not only for ores but also for cryptic rock leads from ultrabasic, oceanic and continental volcanic, granitic, metamorphic, oceanic-pelagic. and continental sedimentary rocks. The data show great application to problems of ore genesis and great promise in ore prospect evaluation.In ore genesis, the major applications are (1) in defining the source material for the lead in the ores and (2) in determining an estimate of the age of mineralization. As an example of each application, isotopic studies have shown that (1) the lead in the Phanerozoic galena ores of southeast Missouri has been mainly from a Cambrian sandstone aquifer unit and perhaps partly the Precambrian basement and Paleozoic carbonate host rock units (in agreement with a lateral secretion hypothesis) and that (2) the age of the bulk of the ores in the Coeur d'Alene district in Idaho now is established as Precambrian, whereas some scientists previously had thought the deposit to be Cenozoic.Applications to ore prospect evaluation are as follows:(1) Most major base-metal ore deposits of the world have characteristic lead isotope ratios and many appear to have lead isotopic compositions that evolved under conditions approximating single-stage conditions. Under these conditions no changes would have occurred in the value of U/Pb and Th/Pb in the source of the ores, since the formation of the earth, other than those resulting from radioactive decay of uranium and thorium. Many minor deposits appear to have leads not evolved under these conditions. This difference in lead isotopic composition between major and minor ore deposits provides an isotopic tool for ore prospect evaluation anywhere in the world.(2) A refined application involves "fingerprinting" the lead of a prospect for matching with that of a producing deposit in the same district, because different producing deposits within a district often have similar lead isotope compositions. This application extends the use of lead isotopes in ore prospect evaluation to certain major ore deposits that have anomalous leads, such as those of the Mississippi Valley.(3) The leads in the high-temperature copper ores of Utah are sinfilar in isotopic composition to leads in the igneous rocks, and the leads in the low-temperature leadzinc-silver ores at Creede, Colorado, have characteristics that must be related to underlying Precambrian country rocks, which suggests that the lead isotopic composition might parallel the zoning of the ore metals in a district. 757 758 B. R. DOE AND J. S. STACEY quiring no more sophisticated knowledge of what produces lead isotopes variations than of what produces trace element variations.The variations in lead isotopic composition are the result of radioactive decay--•aau and •asU to the radiogenic isotopes •øøPb and •ø7Pb (uranogenic leads) respectively and ø'a•Th to the radiogenic isotope 2øaPb (thorogenic lead). The fourth stable lead isotope, •ø4pb, has no long-lived radioactive parent. The physicochemical effects that are so all important on...

Stable Isotope Study of the Langshan Polymetallic Mineral District, Inner Mongolia, China

“…Using the parameter of Doe and Stacey (1974), the model ages of the ore minerals from different ore deposits were calculated, and the results are listed in Table 1. The model ages of the ore minerals are 1.92-2.07 Ga for the Tanyaokou, 1.95-2.07 Ga for the Dongshengmiao and 1.30-1.72 Ga for the Jiashengpan deposits.…”

Flux de dépôt de métaux lourds sur le manteau neigeux alpin français au cours des hivers 1997-1998 et 1998-1999 Méthodologie et résultats préliminaires

“…En .ettet le plomb possède quatr e isotopes sta bles qu i per met te nt de cara ctéri ser ses sou rces anthropiques et natu relles, grâce aux rappo rts isotopiques caractéristiques (signature) des différents gisements dont le plomb est issu . Chaque gisement possède une composition isotopique propre , qui est fonction de l'origine géographique et de l'âge du minerai [10]. Le rappo rt 206Pb/ 2o7 Pb mes uré dan s les princ ipa ux gise me nts mo ndia ux va rie da ns une lar ge ga mme allant de 0,897 pour Barbeton (Afrique du Sud), à 1,385 au Missouri (États -Unis).…”

Le lien genetique entre la mineralisation en or et en mercure et l evolution petrolifere

“…Doe, 1970;Doe and Stacey, 1974) demonstrated that, except in the Mississippi Valley-type lead zinc and fluorite deposits, lead isotope data in many sedimentary rock-hosted stratiform deposits, such as the Kupferschiefer follow the singlestage growth curve, and their model age is identical to their host sedimentary rocks.…”

“…The model age from the ore lead is calculated by the method proposed by Doe and Stacey (1974). The parameters used for plotting single-stage growth curves and the isochrons of Fig.…”