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Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lead isotope values for volcanogenic massive sulfide (VMS) deposits provide important insights into metal sources and the nature of pre-accretionary tectonostratigraphic terranes and underlying basements. Deposits of this type in New England formed in diverse tectonic settings including volcanic arcs and backarcs, a supra–subduction zone arc, a rifted forearc foreland basin, and a rifted continental margin. Following VMS mineralization on or near the seafloor, components of the tectonostratigraphic assemblages—volcanic ± sedimentary rocks, coeval intrusions, sulfide deposits, and underlying basements—were diachronously accreted to the Laurentian margin during the Paleozoic. Lead isotope data for galena show relatively large ranges for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb. Evaluation of potential lead sources, using for comparison Pb-isotope data from modern and ancient settings, suggests that principal sources include the mantle, volcanic ± sedimentary rocks, and deeper basement rocks. Integration of the Pb-isotope values with published data such as Nd isotopes for the volcanic rocks and from deep seismic reflection profiles points to the involvement of several basements, including those of Grenvillian, Ganderian, Avalonian, and West African (and (or) Amazonian) affinity. Clustering of Pb-isotope data for VMS deposits within individual Cambrian and Ordovician volcanic and volcanosedimentary settings, delineated by differences in 206Pb/204Pb and µ (238U/204Pb) values, are consistent with lead derivation from at least four and possibly five different tectonostratigraphic assemblages with isotopically distinct basements. Collectively, our Pb-isotope data for New England VMS deposits provide a novel window into the nature of subarc basement rocks during pre-accretionary sulfide mineralization outboard of Laurentia during early Paleozoic time. [ABSTRACT FROM AUTHOR]

A diverse suite of tholeiitic to alkaline basalt and gabbroic intrusions located in the Coldwell Complex on the northern margin of the Midcontinent Rift exhibit unusual trace element signatures that show enriched large ion lithophile elements and light rare earth elements with negative Nb and Zr anomalies. These features are not typical of magmas derived by partial melting within or above a rising mantle plume, as might be expected in an early Midcontinent Rift magmatic event. In this paper, we provide a detailed geochemical study of a 500 m thick sequence of metabasalt that represents the earliest stage of magmatism in the Coldwell Complex. We show that contamination or crystallization processes or subsequent metasomatism cannot explain the trace element variations. Instead, we propose partial melting in a metasomatized Subcontinental Lithospheric Mantle source to explain the decoupled behavior of large ion lithophile elements from light rare earth elements and heavy rare earth elements and rare earth elements from high field strength elements and the enriched Nd isotope signature of metabasalt. Similar features occur in unit 5b of the Mamainse Point Volcanic Group located at the northern margin of the Rift. An objective of this paper is to relate Two Duck Lake gabbro, host rock for low-sulfur, high precious metal sulfide mineralization at the Marathon deposit, to the metabasalt sequence. The excellent match of trace element abundances in Two Duck Lake gabbro to metabasalt unit 3 confirms an early Coldwell Complex age for metabasalt and a Subcontinental Lithospheric Mantle source for Cu--platinum group element mineralized gabbros. Une succession diversifiée de basaltes tholéiitiques à alcalins et d'intrusions gabbroïques située dans le complexe de Coldwell à la bordure nord du rift médio-continental présente des signatures d'éléments traces inhabituelles qui montrent un enrichissement en éléments lithophiles à grand rayon ionique et en terres rares légères avec des anomalies négatives de Nb et Zr. Ces caractéristiques ne sont pas typiques de magmas issus d'une fusion partielle au-dessus d'un panache mantellique ascendant ou à l'intérieur de celui-ci, à l'instar de ce qui serait attendu durant un épisode magmatique associé au début du rifting médio-continental. Nous présentons une étude géochimique détaillée d'une séquence de 500 m d'épaisseur de métabasaltes qui représente le tout début du magmatisme dans le complexe de Coldwell. Nous démontrons que des processus de contamination ou de cristallisation ou encore un métasomatisme subséquent ne peuvent expliquer les variations des éléments traces. Nous proposons plutôt que la fusion partielle dans une source dans le manteau lithosphérique subcontinental métasomatisé explique le découplage du comportement des éléments lithophiles à grand rayon ionique de celui des terres rares légères et des terres rares lourdes, et le découplage du comportement des terres rares de celui des éléments à forte liaison atomique, ainsi que la signature enrichie des isotopes de Nd des métabasaltes. Des caractéristiques semblables sont observées dans l'unité 5b du Groupe volcanique de Mamainse Point situé à la bordure nord du rift. Un des objectifs du présent article est de relier le gabbro de Two Duck Lake, la roche hôte de la minéralisation en sulfures riche en métaux précieux et pauvre en soufre au gisement Marathon, à la séquence de métabasaltes. L'excellente concordance des abondances d'éléments traces dans le gabbro de Two Duck Lake et dans l'unité 3 des métabasaltes confirme un âge du début de la formation du complexe de Coldwell pour les métabasaltes et une source dans le manteau lithosphérique subcontinental pour les gabbros minéralisés en Cu--élément du groupe platine. [Traduit par la Rédaction], Introduction The Coldwell Complex (CC) in Ontario, Canada (Fig. 1), provides not only a complete record of alkaline intrusive magmatism (Mitchell and Platt 1978, 1982; Mitchell et al. 1993) during [...]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

447 The Touquoy Zone deposit is host to disseminated gold mineralisation in metasiltstones of lower Palaeozoic age. From the close correlation between ore grades and the intersection of favourable stratigraphy and bounding faults, it is apparent that mineralisation is controlled by both structural and lithological influences. Within the ore zone, disseminated gold, arsenopyrite, pyrite, and rare base-metal sulphides are associated with a network of widely spaced, millimetre-scale, quartz carbonate veinlets. Quasi-pervasive fluid flow and prolonged interaction with the host rocks resulted in a diffuse, but pronounced half of wall-rock alteration that is characterized by the breakdown of detrital feldspar and metamorphic chlorite and the development of hydrothermal carbonate phases, K-mica, and disseminated sulphides. These mineralogical changes are accompanied by enrichment in CO[sub2], K, Au, As, and S and depletion in Na across the ore zone. Vein formation occurred at between 250° and 350°C and pressures of less than 1-2 kbar (1 kbar = 100 MPa), corresponding to an estimated depth of between <2.8 and 6 kin. Mineralisation resulted from the unmixing of an overpressured (low-salinity, CO[sub2]-rich) fluid in response to decreasing pressure during its ascent and penetration into permeable host rocks. Geological and geochemical features of mineralisation in the Touquoy Zone deposit are seen as convincing evidence for a close genetic association between disseminated-style and lode gold mineralisation in orogenic terrains, with the resulting style of mineralisation largely controlled by the overall structural geometry of the mineralising site, rheological properties, permeability and chemical receptiveness of the host rock, and structural level of emplacement. [ABSTRACT FROM AUTHOR]

The Wulong lode gold deposit is located in the Liaoning Province, northeast part of North China Craton. Gold ore bodies are mainly hosted in the Late Jurassic granite and structurally controlled by northeast-trending faults. Gold occurs in disseminated and auriferous quartz-sulfide veins and veinlets within hydrothermally altered rocks. Mineralization can be divided into three stages: (1) quartz-pyrite stage, (2) quartz-polymetallic sulfides stage, and (3) quartz-carbonate stage. Gold formed mainly in the middle stage. Quartz formed in the two earlier stages contains three compositional types of fluid inclusions, i.e., pure C[O.sub.2], C[O.sub.2]--[H.sub.2]O and NaCl--[H.sub.2]O, but the late-stage minerals only contain NaCl--[H.sub.2]O inclusions. The inclusions in quartz formed in the early, main, and late stages yield total homogenization temperatures of 317-383 [degrees]C, 260-380 [degrees]C and 159-234 [degrees]C, respectively, with salinities of 5.14-9.44, 2.95-6.20,1.23-4.34 wt% NaCl equivalent, respectively. Trapping pressures estimated from C[O.sub.2]--[H.sub.2]O inclusions are 200-390 MPa in the main stage. Fluid boiling and immiscibility caused rapid precipitation of sulfides and gold. Through immiscibility and inflow of meteoric water, the ore-forming fluid system evolved from C[O.sub.2]-rich to C[O.sub.2]-poor in composition, and from magmatic to meteoric, as indicated by [[delta].sup.18][O.sub.water] values (4.5[per thousand]-7.3[per thousand]). The carbon (-12.2[per thousand] to -11.5[per thousand]), sulfur (0.9[per thousand]-2.6[per thousand]), and lead isotope ([.sup.207]Pb/[.sup.204]Pb of 15.606-15.618) compositions suggest the host rocks to be a significant source of ore metals. Integrating the data obtained from the studies including regional geology, ore geology, fluid inclusion, and C--H--O--S--Pb isotope geochemistry, we conclude that the Wulong deposit is a decratonization gold deposit formed during lithospheric thinning associated with destruction of the North China Craton triggered by the subduction of the Paleo-Pacific Oceanic plate in the Early Cretaceous. Key words: Wulong lode gold deposit, C--H--O--S--Pb isotopes, fluid inclusions, northeastern North China Craton, decratonization-type gold deposit. Le gisement d'or filonien de Wulong est situé dans la province de Liaoning, dans la partie nord-est du craton de Chine septentrionale. Les corps aurifères sont principalement encaissés dans du granite d'âge jurassique tardif et sont contrôlés sur le plan structural par des failles d'orientation nordest. L'or se trouve dans des filons et filonnets de quartz--sulfures aurifères disséminés dans des roches ayant fait l'objet d'une altération hydrothermale. La genèse de la minéralisation peut être divisée en trois étapes : (1) une étape à quartz et pyrite, (2) une étape à quartz et sulfures polymétalliques et (3) une étape à quartz et carbonates. L'or s'est principalement formé durant la deuxième étape. Le quartz formé durant les deux premières étapes contient trois types d'inclusions fluides sur le plan compositionnel, à savoir des inclusions de C[O.sub.2] pur, de C[O.sub.2]--[H.sub.2]O et de NaCl--[H.sub.2]O, alors que les minéraux de la dernière étape ne contiennent que des inclusions de NaCl--[H.sub.2]O. Les inclusions dans le quartz formées durant les étapes précoce, principale et tardive donnent des températures d'homogénéisation totale de 317-383 [degré]C, 260-380 [degré]C et 159-234 [degré]C, respectivement, et des salinités de 5,14-9,44%, 2,95-6,20% et 1,23-4,34% en poids d'équivalent NaCl, respectivement. Les pressions de piégeage estimées pour les inclusions de C[O.sub.2]--[H.sub.2]O sont de 200-390 MPa durant l'étape principale. L'ébullition et l'immiscibilité des fluides ont entraîné la précipitation rapide de sulfures et d'or. En raison de l'immiscibilité et de l'entrée d'eau météorique, le système de fluides minéralisateurs est passé d'une composition riche en C[O.sub.2] à une composition pauvre en C[O.sub.2], et de magmatique à météorique, comme l'indiquent les valeurs de [[delta].sup.18][O.sub.eau] (4,5 [per thousand]-7,3 [per thousand]). Les concentrations d'isotopes de carbone (de -12,2 [per thousand] à -11,5 [per thousand]), de soufre (0,9 [per thousand]-2,6 [per thousand]) et de plomb ([.sup.207]Pb/[.sup.204]Pb : 15,606-15,618) donnent à penser que les encaissantes étaient une importante source des métaux composant le minerai. L'intégration des données obtenues des études de la géologie régionale, de la géologie du minerai, des inclusions fluides et de la géochimie des isotopes de C--H--O--S--Pb nous permet de conclure que le gisement de Wulong est un gisement aurifère de type décratonisation, formé durant l'amincissement de la lithosphère associé à la destruction du craton de Chine septentrionale déclenchée par la subduction de la plaque océanique paléopacifique au Crétacé précoce. Mots-clés: gisement d'or filonien de Wulong, isotopes de C--H--O--S--Pb, inclusions fluides, nord-est du craton de Chine septentrionale, gisement aurifère de type décratonisation., Introduction The concept of an orogenic-type gold deposit was first introduced by Bohlke (1982) and then thoroughly addressed by Groves et al. (1998), Kerrich et al. (2000), and Goldfarb et [...]

The ~60 m thick Magilligan Sill is part of the British Palaeogene Igneous Province in the North Atlantic. The sill comprises layers of dolerite and olivine gabbro, and it intrudes a thick sequence of Mesozoic mudstones and marls, which are locally baked at the sill margins. Since 2014, the sill has been an exploration target for orthomagmatic Ni-Cu-platinum group element (PGE) sulfide mineralisation analogous to the Noril'sk-Talnakh intrusion in Russia. We present new petrological, geochemical, and S isotope data to assess the prospectivity of the sill and the underlying magmatic plumbing system. Most sulfides in the dolerite portions of the sill are 150 [micro]m size pentlandite, chalcopyrite, and pyrrhotite grains contain Keywords: PGE, sulfur isotopes, magma conduit system, mineralisation, North Atlantic Igneous Province. Le m de Magilligan, d'une épaisseur d'environ 60 m, fait partie de la province magmatique paléogène britannique de l'Atlantique Nord. Le filon-couche est constitué de couches de dolérite et de gabbro à olivine et recoupe une épaisse séquence de mudstones et marnes mésozoïques, qui sont cuits localement au contact du filon-couche. Depuis 2014, le filon-couche est une cible d'exploration pour de la minéralisation orthomagmatique à sulfures de Ni - Cu - éléments du groupe platine (EGP) analogue à celle de l'intrusion du Noril'sk-Talnakh en Russie. Nous présentons de nouvelles données pétrologiques, géochimiques et sur les isotopes de S afin d'évaluer la prospectivité du filon-couche et du système de plomberie magmatique sous-jacent. La plupart des sulfures dans les parties doléritiques du filon-couche font moins de 50 [micro]m et ne comprennent que de la pyrite avec des concentrations en EGP inférieures à la limite de détection. Dans les gabbros à olivine, des grains de pentlandite, chalcopyrite et pyrrhotite de >150 [micro]m contiennent Mots-clés: EGP, isotopes du soufre, système de conduits magmatiques, minéralisation, province magmatique de l'Atlantique Nord., Introduction Mafic-ultramafic magmatic plumbing systems in the upper crust may be highly prospective for orthomagmatic sulfide mineralisation, and they host some of the largest Ni-Cu and platinum group element (PGE) [...]

The Timmins-Porcupine gold camp, Abitibi greenstone belt, is host >60 Moz of Au with many gold deposits spatially associated with porphyry intrusions and the Porcupine-Destor deformation zone (PDDZ). Porphyry intrusions form three suites. The Timmins porphyry suite (TIS) consists of high-Al tonalite-trondjhemite-granodiorite (TTG) with calc-alkalic affinities and high La/Yb ratios and formed during ~2690 Ma D1-related crustal thickening and hydrous partial melting of mafic crust where garnet and hornblende were stable in the residue. The Carr Township porphyry intrusive suite (CIS) and the granodiorite intrusive suite (GIS) also have high-Al TTG, calc-alkalic affinities, but were generated 10-15 million years after the TIS; the CIS were generated at shallower depths (during postorogenic extension?) with no garnet in the crustal residue, whereas the GIS formed during D2 thrust-related crustal thickening and partial melting where garnet was stable in the residue. Gold mineralization is preferentially associated with the TIS, and to a lesser extent the GIS, proximal to the PDDZ. Intrusions near mineralization have abundant sericite, carbonate, and sulphide alteration. These intrusions exhibit low Na2O and Sr, and high [Al.sub.2][O.sub.3]/[Na.sub.2]O, [K.sub.2]O, [K.sub.2]O/[Na.sub.2]O, Rb, and Cs, (i.e., potassic alteration); sulfide- and carbonate-altered porphyries have high (CaO + MgO + [Fe.sub.2][O.sub.3])/[Al.sub.2][O.sub.3] and LOI values. Although porphyries are not genetically related to gold mineralization, they are spatially related and are interpreted to reflect the emplacement of intrusions and subsequent Au-bearing fluids along the same crustal structures. The intrusive rocks also served as structural traps, where gold mineralization precipitated in dilatant structures along the margins of intrusions during regional (D3?) deformation. Key words: Abitibi, orogenic gold, lithogeochemistry, economic geology, petrology. Resume : Le camp minier de Timmins-Porcupine, dans la ceinture de roches vertes de l'Abitibi, renferme plus de 60 Moz d'or, dont de nombreux gisements auriferes associes dans l'espace a des intrusions de porphyre et la zone de deformation de Porcupine-Destor (ZDPP). Les intrusions de porphyre forment trois series. La serie de porphyres de Timmins (TIS) est composee de tonalites-trondjhemites-granodiorites (TTG) riches en Al avec des affinites calcoalcalines et des rapports La/Yb eleves et elle s'est formee vers 2690 Ma durant un epaississement crustal associe a D1 et la fusion partielle de croute mafique en presence d'eau ayant produit des roches residuelles dans lesquelles le grenat et la hornblende etaient stables. La serie d'intrusions porphyriques du township de Carr (CIS) et la serie intrusive granodioritique (GIS) presentent aussi des TTG riches en Al a affinites calcoalcalines, mais ont ete produites de 10 millions d'annees a 15 millions d'annees apres la TIS; la CIS a ete generee a de plus faibles profondeurs (durant une extension post-orogenique?), le grenat n'etant pas stable dans le residu, alors que la GIS s'est formee durant l'epaississement crustal associe au chevauchement D2 et une fusion partielle dans le residu de laquelle le grenat etait stable. La mineralisation aurifere est preferentiellement associee a la TIS et, dans une moindre mesure, a la GIS, a proximite de la ZDPP. Dans les intrusions a proximite de mineralisation, la sericite, les carbonates et une alteration a sulfures sont abondants. Ces intrusions presentent de faibles concentrations de Na2O et Sr et des valeurs elevees de [Al.sub.2][O.sub.3]/[Na.sub.2]O, [K.sub.2]O, [K.sub.2]O/[Na.sub.2]O, Rb et Cs (c.-a-d., alteration potassique); les porphyres a alteration a sulfures et carbonates presentent des valeurs elevees de (CaO + MgO + [Fe.sub.2][O.sub.3])/[Al.sub.2][O.sub.3] et de perte au feu. Si les porphyres ne sont pas genetiquement relies a la mineralisation aurifere, ils lui sont associes dans l'espace et interpretes comme refletant la mise en place d'intrusions, puis de fluides auriferes le long des memes structures crustales. Les roches intrusives ont egalement servi de pieges structuraux dans lesquels la mineralisation aurifere a ete precipitee dans des structures de dilatation le long des bordures d'intrusions durant la deformation regionale (D3?). [Traduit par la Redaction] Mots-cles: Abitibi, or orogenique, lithogeochimie, geologie economique, petrologie., Introduction The Timmins-Porcupine gold camp represents one of the world's most prolific gold mining camps containing >60 Moz of Au (past production and current reserves) since its discovery in 1909 [...]

The Hongqiling magmatic Ni-Cu sulfide deposit, situated on the southern margin of the eastern Central Asian Orogenic Belt (CAOB), is composed of over 30 mafic-ultramafic intrusions. These ore-bearing intrusions are composed mainly of harzburgite, lherzolite, websterite, orthopyroxenite, and norite (gabbro). The constituent minerals are olivine, diopside, bronzite, calcic-hornblende, plagioclase, and spinel with orthopyroxene as a dominant mineral in these intrusions. These ore-bearing intrusions are not Alaskan-type complexes. Spinel and clinopyroxene both exhibit different chemical compositions from those in the Alaskan-type complexes. The rocks that make up the intrusions have high contents of MgO (average value = 25.20 wt.%) and low Ti[O.sub.2] (average value = 0.58 wt.%). The high MgO contents of the minerals and the high Mg (#) (71) of the calculated melt in equilibrium with olivine demonstrate that the parental magma of the Hongqiling mafic-ultramafic intrusions was a high-Mg tholeiitic magma. The Hongqiling ore-bearing mafic-ultramafic intrusions and the calculated 'trapped liquids' for the olivine-orthopyroxene cumulate rocks are all enriched in large-ion lithophile elements and depleted in high field strength elements. The Ce/Pb, Ta/La, Th/Yb, and (La/Sm)PM values and the depletion of Nb and Ta suggest that the magma experienced crustal contamination. The Hongqiling ore-bearing intrusions display many similarities with mafic-ultramafic intrusions that formed in a post-collisional extensional environment in the western CAOB (e.g., Huangshanxi). Common features include their whole-rock compositions and mineral chemistry. Combined with the evolutionary history of the eastern segment of the CAOB, we believe that the Late Triassic Hongqiling mafic-ultramafic intrusions formed in a post-collisional extensional environment.Le gisement magmatique de sulfures a Ni-Cu de Hongqiling, situe a la bordure sud de la ceinture orogenique d'Asie centrale (COAC), renferme plus de 30 intrusions mafiques-ultramafiques. Ces intrusions mineralisees sont constituees principalement d'harzburgite, de lherzolite, de websterite, d'orthopyroxenite et de norite (gabbro). Les mineraux constituants sont l'olivine, le diopside, la bronzite, la hornblende calcique, le plagioclase et le spinelle, l'orthopyroxene etant un mineral dominant dans ces intrusions. Ces intrusions mineralisees ne sont pas des complexes de type alaskien. Le spinelle et le clinopyroxene presentent tous deux des compositions chimiques differentes de celles de complexes de type alaskien. Les roches qui composent les intrusions ont de fortes teneurs en MgO (moyenne = 25,20% en poids) et de faibles teneurs en Ti[O.sub.2] (moyenne = 0,58% en poids). Les fortes teneurs en MgO des mineraux et le Mg (#) eleve (71) de la composition calculee du magma en equilibre avec l'olivine demontrent que le magma parental des intrusions mafiques-ultramafiques de Hongqiling etait un magma tholeiitique riche en Mg. Ces intrusions et les [much less than]liquides pieges[much greater than] qui ont produit les cumulats a olivine et orthopyroxene sont tous enrichis en elements lithophiles a grand rayon ionique et appauvris en elements a forte liaison atomique. Les valeurs de Ce/Pb, Ta/La, Th/Yb et (La/Sm)PM et l'appauvrissement en Nb et Ta donnent a penser que le magma a subi une contamination crustale. Les intrusions mineralisees de Hongqiling partagent de nombreuses similitudes avec les intrusions mafiques-ultramafiques formees dans un milieu d'extension post-collision dans la partie ouest de la COAC (p. ex. Huangshanxi), dont leurs compositions sur roche totale et la chimie de leurs mineraux. La combinaison de ces resultats et de l'evolution du segment est de la COAC nous porte a croire que les intrusions mafiques-ultramafiques de Hongqiling du Trias tardif se sont formees dans un milieu d'extension post-collision. [Traduit par la Redaction], IntroductionA number of small Ni-Cu ore-bearing mafic-ultramafic intrusions occur in the southern part of the Central Asian Orogenic Belt (CAOB); examples include the Kalatongke (Song and Li 2009; Z.C. Zhang [...]