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Détail de l'auteur
Auteur David I. Groves
Documents disponibles écrits par cet auteur
Affiner la rechercheBroad synchroneity of three gold mineralization styles in the kalgoorlie gold field / Noreen M. Vielreicher in Economic geology, Vol. 105 N° 1 (Janvier/Fevrier 2010)
[article]
in Economic geology > Vol. 105 N° 1 (Janvier/Fevrier 2010) . - pp. 187-227
Titre : Broad synchroneity of three gold mineralization styles in the kalgoorlie gold field : SHRIMP, U-Pb, and 40Ar/39Ar geochronological evidence Type de document : texte imprimé Auteurs : Noreen M. Vielreicher, Auteur ; David I. Groves, Auteur ; Lawrence W. Snee, Auteur Année de publication : 2011 Article en page(s) : pp. 187-227 Note générale : Economic geology Langues : Anglais (eng) Mots-clés : Gold mineralization Uranium Plomb Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : There has been a long-standing controversy regarding the timing and number of gold mineralization events at Kalgoorlie. Uranium-Pb dating of zircons and hydrothermal monazite and xenotime, as well as 40Ar/39Ar analysis of metasomatic fuchsite and white mica, are used to date pre- to synore dikes, alteration, and orebodies in order to resolve this issue. The majority of gold mineralization at Kalgoorlie, including ductile-brittle Fimiston-, brittle-ductile Oroya- and brittle Mount Charlotte-style gold, are different expressions of a complex mineralizing system that was active at broadly the same time at ca. 2.64 Ga. Gold mineralization was thus deposited in both ductile and brittle structures at approximately the same crustal level at broadly the same time, under similar P-T conditions. This giant ore system formed after ca. 2.69 Ga basic magmatism, intrusion of the Golden Mile Dolerite sill at 2680 ± 9 Ma, and intrusion of calc-alkaline feldspar-quartz porphyry dikes at 2670 ± 5 Ma. Gold mineralization was broadly coeval with lamprophyre dike intrusion at 2642 ± 6 Ma and overlapped the waning stages of hornblende- and albite-bearing porphyry dike emplacement at 2650 ± 6 Ma and regional metamorphism. Subsequent brittle deformation in the Kalgoorlie gold field was accompanied by hydrothermal activity that may have led to some late gold mineralization or remobilization in extensional quartz vein arrays in the Golden Mile between about 2.61 and 2.60 Ga. This late hydrothermal activity and associated brittle deformation marks the last event to significantly affect the rocks at Kalgoorlie and may be related to uplift and final cooling of the terrane. Despite this late event, the geometry of the Kalgoorlie gold field and its contained lode systems has remained essentially the same since the time of gold mineralization. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/1/187.abstract [article] Broad synchroneity of three gold mineralization styles in the kalgoorlie gold field : SHRIMP, U-Pb, and 40Ar/39Ar geochronological evidence [texte imprimé] / Noreen M. Vielreicher, Auteur ; David I. Groves, Auteur ; Lawrence W. Snee, Auteur . - 2011 . - pp. 187-227.
Economic geology
Langues : Anglais (eng)
in Economic geology > Vol. 105 N° 1 (Janvier/Fevrier 2010) . - pp. 187-227
Mots-clés : Gold mineralization Uranium Plomb Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : There has been a long-standing controversy regarding the timing and number of gold mineralization events at Kalgoorlie. Uranium-Pb dating of zircons and hydrothermal monazite and xenotime, as well as 40Ar/39Ar analysis of metasomatic fuchsite and white mica, are used to date pre- to synore dikes, alteration, and orebodies in order to resolve this issue. The majority of gold mineralization at Kalgoorlie, including ductile-brittle Fimiston-, brittle-ductile Oroya- and brittle Mount Charlotte-style gold, are different expressions of a complex mineralizing system that was active at broadly the same time at ca. 2.64 Ga. Gold mineralization was thus deposited in both ductile and brittle structures at approximately the same crustal level at broadly the same time, under similar P-T conditions. This giant ore system formed after ca. 2.69 Ga basic magmatism, intrusion of the Golden Mile Dolerite sill at 2680 ± 9 Ma, and intrusion of calc-alkaline feldspar-quartz porphyry dikes at 2670 ± 5 Ma. Gold mineralization was broadly coeval with lamprophyre dike intrusion at 2642 ± 6 Ma and overlapped the waning stages of hornblende- and albite-bearing porphyry dike emplacement at 2650 ± 6 Ma and regional metamorphism. Subsequent brittle deformation in the Kalgoorlie gold field was accompanied by hydrothermal activity that may have led to some late gold mineralization or remobilization in extensional quartz vein arrays in the Golden Mile between about 2.61 and 2.60 Ga. This late hydrothermal activity and associated brittle deformation marks the last event to significantly affect the rocks at Kalgoorlie and may be related to uplift and final cooling of the terrane. Despite this late event, the geometry of the Kalgoorlie gold field and its contained lode systems has remained essentially the same since the time of gold mineralization. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/1/187.abstract Iron oxide copper-gold (IOCG) deposits through earth history / David I. Groves in Economic geology, Vol. 105 N° 3 (Mai 2010)
[article]
in Economic geology > Vol. 105 N° 3 (Mai 2010) . - pp. 641-654
Titre : Iron oxide copper-gold (IOCG) deposits through earth history : implications for origin, lithospheric setting, and distinction from other epigenetic iron oxide deposits Type de document : texte imprimé Auteurs : David I. Groves, Auteur ; Frank P. Bierlein, Auteur ; Lawrence D. Meinert, Auteur Année de publication : 2011 Article en page(s) : pp. 641-654 Note générale : Economic geology Langues : Anglais (eng) Mots-clés : Iron opxide Gold deposits Copper deposits Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The iron oxide copper-gold (IOCG) group of deposits, initially defined following discovery of the giant Olympic Dam Cu-U-Au deposit, has progressively become too-embracing when associated deposits and potential end members or analogs are included. The broader group includes several low Ti iron oxide-associated deposits that include iron oxide (P-rich), iron oxide (F- and REE-rich), Fe or Cu-Au skarn, high-grade iron oxide-hosted Au ± Cu, carbonatite-hosted (Cu-, REE-, and F-rich), and IOCG sensu stricto deposits. Consideration of this broad group as a whole obscures the critical features of the IOCG sensu stricto deposits, such as their temporal distribution and tectonic environment, thus leading to difficulties in developing a robust exploration model.
The IOCG sensu stricto deposits are magmatic-hydrothermal deposits that contain economic Cu and Au grades, are structurally controlled, commonly contain significant volumes of breccia, are commonly associated with presulfide sodic or sodic-calcic alteration, have alteration and/or brecciation zones on a large, commonly regional, scale relative to economic mineralization, have abundant low Ti iron oxides and/or iron silicates intimately associated with, but generally paragenetically older than, Fe-Cu sulfides, have LREE enrichment and low S sulfides (lack of abundant pyrite), lack widespread quartz veins or silicification, and show a clear temporal, but not close spatial, relationship to major magmatic intrusions. These intrusions, where identified, are commonly alkaline to subalkaline, mixed mafic (even ultramafic) to felsic in composition, with evidence for mantle derivation of at least the mafic end members of the suite. The giant size of many of the deposits and surrounding alteration zones, the highly saline ore fluids, and the available stable and radiogenic isotope data indicate release of deep, volatile-rich magmatic fluids through devolatization of causative, mantle-derived magmas and variable degrees of mixing of these magmatic fluids with other crustal fluids along regional-scale fluid flow paths.
Precambrian deposits are the dominant members of the IOCG group in terms of both copper and gold resources. The 12 IOCG deposits with >100 tonnes (t) resources are located in intracratonic settings within about 100 km of the margins of Archean or Paleoproterozoic cratons or other lithospheric boundaries, and formed 100 to 200 m.y. after supercontinent assembly. Their tectonic setting at formation was most likely anorogenic, with magmatism and associated hydrothermal activity driven by mantle underplating and/or plumes. Limited amounts of partial melting of volatile-rich and possibly metal-enriched metasomatized early Precambrian subcontinental lithospheric mantle (SCLM), fertilized during earlier subduction, probably produced basic to ultrabasic magmas that melted overlying continental crust and mixed with resultant felsic melts, with devolatilization and some penecontemporaneous incorporation of other lower to middle crustal fluids to produce the IOCG deposits. Preservation of near-surface deposits, such as Olympic Dam, is probably due to their formation above buoyant and refractory SCLM, which resisted delamination and associated uplift.
Most Precambrian iron oxide (P-rich) or magnetite-apatite (Kiruna-type) deposits have a different temporal distribution, apparently forming in convergent margin settings prior to or following supercontinent assembly. It is only in the Phanerozoic that IOCG and magnetite-apatite deposits are roughly penecontemporaneous in convergent margin settings. The Phanerozoic IOCG deposits, such as Candelaria, Chile, occur in anomalous extensional to transtensional zones in the Coastal Cordillera, which are also the sites of mantle-derived mafic to felsic intrusions that are anomalous in an Andean context. This implies that special conditions, possibly detached slabs of metasomatized SCLM, may be required in convergent margin settings to generate world-class IOCG deposits.
It is likely that formation of giant IOCG deposits was mainly a Precambrian phenomenon related to the extensive mantle underplating that impacted on buoyant metasomatized SCLM. Generally smaller and rarer Phanerozoic IOCG deposits formed in tectonic settings where conditions similar to those in the Precambrian were replicated.DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/3/641.abstract [article] Iron oxide copper-gold (IOCG) deposits through earth history : implications for origin, lithospheric setting, and distinction from other epigenetic iron oxide deposits [texte imprimé] / David I. Groves, Auteur ; Frank P. Bierlein, Auteur ; Lawrence D. Meinert, Auteur . - 2011 . - pp. 641-654.
Economic geology
Langues : Anglais (eng)
in Economic geology > Vol. 105 N° 3 (Mai 2010) . - pp. 641-654
Mots-clés : Iron opxide Gold deposits Copper deposits Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The iron oxide copper-gold (IOCG) group of deposits, initially defined following discovery of the giant Olympic Dam Cu-U-Au deposit, has progressively become too-embracing when associated deposits and potential end members or analogs are included. The broader group includes several low Ti iron oxide-associated deposits that include iron oxide (P-rich), iron oxide (F- and REE-rich), Fe or Cu-Au skarn, high-grade iron oxide-hosted Au ± Cu, carbonatite-hosted (Cu-, REE-, and F-rich), and IOCG sensu stricto deposits. Consideration of this broad group as a whole obscures the critical features of the IOCG sensu stricto deposits, such as their temporal distribution and tectonic environment, thus leading to difficulties in developing a robust exploration model.
The IOCG sensu stricto deposits are magmatic-hydrothermal deposits that contain economic Cu and Au grades, are structurally controlled, commonly contain significant volumes of breccia, are commonly associated with presulfide sodic or sodic-calcic alteration, have alteration and/or brecciation zones on a large, commonly regional, scale relative to economic mineralization, have abundant low Ti iron oxides and/or iron silicates intimately associated with, but generally paragenetically older than, Fe-Cu sulfides, have LREE enrichment and low S sulfides (lack of abundant pyrite), lack widespread quartz veins or silicification, and show a clear temporal, but not close spatial, relationship to major magmatic intrusions. These intrusions, where identified, are commonly alkaline to subalkaline, mixed mafic (even ultramafic) to felsic in composition, with evidence for mantle derivation of at least the mafic end members of the suite. The giant size of many of the deposits and surrounding alteration zones, the highly saline ore fluids, and the available stable and radiogenic isotope data indicate release of deep, volatile-rich magmatic fluids through devolatization of causative, mantle-derived magmas and variable degrees of mixing of these magmatic fluids with other crustal fluids along regional-scale fluid flow paths.
Precambrian deposits are the dominant members of the IOCG group in terms of both copper and gold resources. The 12 IOCG deposits with >100 tonnes (t) resources are located in intracratonic settings within about 100 km of the margins of Archean or Paleoproterozoic cratons or other lithospheric boundaries, and formed 100 to 200 m.y. after supercontinent assembly. Their tectonic setting at formation was most likely anorogenic, with magmatism and associated hydrothermal activity driven by mantle underplating and/or plumes. Limited amounts of partial melting of volatile-rich and possibly metal-enriched metasomatized early Precambrian subcontinental lithospheric mantle (SCLM), fertilized during earlier subduction, probably produced basic to ultrabasic magmas that melted overlying continental crust and mixed with resultant felsic melts, with devolatilization and some penecontemporaneous incorporation of other lower to middle crustal fluids to produce the IOCG deposits. Preservation of near-surface deposits, such as Olympic Dam, is probably due to their formation above buoyant and refractory SCLM, which resisted delamination and associated uplift.
Most Precambrian iron oxide (P-rich) or magnetite-apatite (Kiruna-type) deposits have a different temporal distribution, apparently forming in convergent margin settings prior to or following supercontinent assembly. It is only in the Phanerozoic that IOCG and magnetite-apatite deposits are roughly penecontemporaneous in convergent margin settings. The Phanerozoic IOCG deposits, such as Candelaria, Chile, occur in anomalous extensional to transtensional zones in the Coastal Cordillera, which are also the sites of mantle-derived mafic to felsic intrusions that are anomalous in an Andean context. This implies that special conditions, possibly detached slabs of metasomatized SCLM, may be required in convergent margin settings to generate world-class IOCG deposits.
It is likely that formation of giant IOCG deposits was mainly a Precambrian phenomenon related to the extensive mantle underplating that impacted on buoyant metasomatized SCLM. Generally smaller and rarer Phanerozoic IOCG deposits formed in tectonic settings where conditions similar to those in the Precambrian were replicated.DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/105/3/641.abstract Petrogenesis of postcollisional magmatism at Scheelite Dome, Yukon, Canada / John L. Mair in Economic geology, Vol. 106 N° 3 (Mai 2011)
[article]
in Economic geology > Vol. 106 N° 3 (Mai 2011) . - pp. 451-480
Titre : Petrogenesis of postcollisional magmatism at Scheelite Dome, Yukon, Canada : evidence for a lithospheric mantle source for magmas associated with intrusion-related gold systems Type de document : texte imprimé Auteurs : John L. Mair, Auteur ; G. Lang Farmer, Auteur ; David I. Groves, Auteur Année de publication : 2011 Article en page(s) : pp. 451-480 Note générale : Géologie Economique Langues : Anglais (eng) Mots-clés : Postcollisional magmatism Lithospheric mantle Scheelite Dome Gold systems Canada Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The type examples for the class of deposits termed intrusion-related gold systems occur in the Tombstone-Tungsten belt of Alaska and Yukon, on the eastern side of the Tintina gold province. In this part of the northern Cordillera, extensive mid-Cretaceous postcollisional plutonism took place following the accretion of exotic terranes to the continental margin. The most cratonward of the resulting plutonic belts comprises small isolated intrusive centers, with compositionally diverse, dominantly potassic rocks, as exemplified at Scheelite Dome, located in central Yukon. Similar to other spatially and temporally related intrusive centers, the Scheelite Dome intrusions are genetically associated with intrusion-related gold deposits.
Intrusions have exceptional variability, ranging from volumetrically dominant clinopyroxene-bearing monzogranites, to calc-alkaline minettes and spessartites, with an intervening range of intermediate to felsic stocks and dikes, including leucominettes, quartz monzonites, quartz monzodiorites, and granodiorites. All rock types are potassic, are strongly enriched in LILEs and LREEs, and feature high LILE/HFSE ratios. Clinopyroxene is common to all rock types and ranges from salite in felsic rocks to high Mg augite and Cr-rich diopside in lamprophyres. Less common, calcic amphibole ranges from actinolitic hornblende to pargasite. The rocks have strongly radiogenic Sr (initial 87Sr/86Sr from 0.711-0.714) and Pb isotope ratios (206Pb/204Pb from 19.2-19.7), and negative initial {varepsilon}Nd values (–8.06 to –11.26).
Whole-rock major and trace element, radiogenic isotope, and mineralogical data suggest that the felsic to intermediate rocks were derived from mafic potassic magmas sourced from the lithospheric mantle via fractional crystallization and minor assimilation of metasedimentary crust. Mainly unmodified minettes and spessartites represent the most primitive and final phases emplaced. Metasomatic enrichments in the underlying lithospheric mantle are attributes of the ancient North American cratonic margin that appear to be essential prerequisites to this style of postcollisional magmatism and associated gold-rich fluid exsolution. This type of magmatic hydrothermal activity occurs in a very specific tectonic setting that typically sets intrusion-related gold deposits apart from orogenic gold deposits, which are synorogenic in timing and have no consistent direct relationship to such diverse and contemporaneous lithospheric mantle-derived magmas, although they too are commonly sited adjacent to lithospheric boundaries.
DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/cgi/content/abstract/106/3/451 [article] Petrogenesis of postcollisional magmatism at Scheelite Dome, Yukon, Canada : evidence for a lithospheric mantle source for magmas associated with intrusion-related gold systems [texte imprimé] / John L. Mair, Auteur ; G. Lang Farmer, Auteur ; David I. Groves, Auteur . - 2011 . - pp. 451-480.
Géologie Economique
Langues : Anglais (eng)
in Economic geology > Vol. 106 N° 3 (Mai 2011) . - pp. 451-480
Mots-clés : Postcollisional magmatism Lithospheric mantle Scheelite Dome Gold systems Canada Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The type examples for the class of deposits termed intrusion-related gold systems occur in the Tombstone-Tungsten belt of Alaska and Yukon, on the eastern side of the Tintina gold province. In this part of the northern Cordillera, extensive mid-Cretaceous postcollisional plutonism took place following the accretion of exotic terranes to the continental margin. The most cratonward of the resulting plutonic belts comprises small isolated intrusive centers, with compositionally diverse, dominantly potassic rocks, as exemplified at Scheelite Dome, located in central Yukon. Similar to other spatially and temporally related intrusive centers, the Scheelite Dome intrusions are genetically associated with intrusion-related gold deposits.
Intrusions have exceptional variability, ranging from volumetrically dominant clinopyroxene-bearing monzogranites, to calc-alkaline minettes and spessartites, with an intervening range of intermediate to felsic stocks and dikes, including leucominettes, quartz monzonites, quartz monzodiorites, and granodiorites. All rock types are potassic, are strongly enriched in LILEs and LREEs, and feature high LILE/HFSE ratios. Clinopyroxene is common to all rock types and ranges from salite in felsic rocks to high Mg augite and Cr-rich diopside in lamprophyres. Less common, calcic amphibole ranges from actinolitic hornblende to pargasite. The rocks have strongly radiogenic Sr (initial 87Sr/86Sr from 0.711-0.714) and Pb isotope ratios (206Pb/204Pb from 19.2-19.7), and negative initial {varepsilon}Nd values (–8.06 to –11.26).
Whole-rock major and trace element, radiogenic isotope, and mineralogical data suggest that the felsic to intermediate rocks were derived from mafic potassic magmas sourced from the lithospheric mantle via fractional crystallization and minor assimilation of metasedimentary crust. Mainly unmodified minettes and spessartites represent the most primitive and final phases emplaced. Metasomatic enrichments in the underlying lithospheric mantle are attributes of the ancient North American cratonic margin that appear to be essential prerequisites to this style of postcollisional magmatism and associated gold-rich fluid exsolution. This type of magmatic hydrothermal activity occurs in a very specific tectonic setting that typically sets intrusion-related gold deposits apart from orogenic gold deposits, which are synorogenic in timing and have no consistent direct relationship to such diverse and contemporaneous lithospheric mantle-derived magmas, although they too are commonly sited adjacent to lithospheric boundaries.
DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/cgi/content/abstract/106/3/451