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The Laird Lake property, southwest Red Lake greenstone belt, straddles the contact between the Balmer (2.99–2.96 Ga) and the Confederation (2.74–2.73 Ga) assemblages. The property is 10 km along strike from the Madsen and Starrat–Olsen Au mines that are hosted near the contact. The Balmer assemblage consists of fine-grained, aphyric, locally pillowed mafic volcanic rocks, ultramafic intrusive and volcanic rocks with flow breccia textures hosting local spinifex-bearing clasts, and banded-iron formations. In contrast, the Confederation assemblage comprises porphyritic mafic volcanic rocks intercalated with intermediate to felsic volcanic rocks that include crystal lapilli tuffs, crystal tuffs, and tuffs. The Balmer assemblage is composed of tholeiitic mafic volcanic rocks with minor Al-undepleted komatiites, whereas the Confederation assemblage is calc–alkalic. Neodymium isotopes, in conjunction with trace element geochemistry, suggests that parts of the Balmer assemblage were weakly contaminated by an older intermediate basement. Both arc and back-arc volcanism occurs in the Confederation assemblage, with the arc rocks showing a stronger crustal component than the back-arc rocks. A maximum U–Pb age of 2741 ± 19 Ma for a crystal tuff and an age of 2737.68 ± 0.79 Ma for a diorite are consistent with a Confederation assemblage affinity for the intermediate calc–alkaline rocks south of the Au-bearing horizon. The Balmer assemblage represents an oceanic plateau formed by plume magmatism on the margins of the North Caribou Terrane, whereas the Confederation assemblage at Laird Lake formed in an oceanic arc setting where both arc and back-arc volcanism occurred simultaneously. [ABSTRACT FROM AUTHOR]

Igneous rocks of the Jurassic continental arc of southwest North American Cordillera crop out in the region between Cananea and Nacozari, in northeastern Sonora, Mexico. Contemporaneous igneous rocks occur farther south in the Nazas rift province; however, their tectonic affinity is debated between the southern extension of the Cordilleran arc and an origin associated with decompressive mantle melting during the Pangea breakup. We consider that the studied rocks represent the southernmost expression of the Jurassic continental arc. Four magmatic units are distinguished based on geology, U–Pb zircon geochronology, and geochemical composition. They comprise the Buenos Aires granite dated at 183.8 ± 1.1 Ma, the Mababi granite with ages of 175.5 ± 1.8, 173.5 ± 1.8, and 171.7 ± 1.0 Ma, the Elenita Formation volcanic rocks dated at 169.7 ± 1.7 Ma, and the Cerro Blanco granite dated at 162.3 ± 2.4 Ma. The studied samples correspond to highly differentiated rocks with high-silica contents (69–76 wt.%), low Mg# values (mostly <45), and alkali–calcic and peraluminous compositions suggesting crustal contamination. LREE-enriched normalized slopes with negative Eu anomalies and multielement plots characterized by well-developed negative anomalies of Nb–Ta, P, and Ti provide an unequivocal signal of the continental arc nature. In contrast to the Nazas province, where the Jurassic magmatism consists of discreet volcaniclastic sequences deposited in extensional basins with no evidence of plutonic rocks, the Jurassic continental arc of Arizona and northern Sonora forms a regionally coherent geological feature characterized by large exposures of volcanic and plutonic rocks. [ABSTRACT FROM AUTHOR]

The Huaduoshan Cu–Mo prospect is in the Duobaoshan orefield, northeast China. The Cu–Mo mineralization occurs in the granodiorites as veinlet-disseminated. The ore-forming process can be divided into four mineralization stages: (I) quartz–pyrite–magnetite; (II) quartz–pyrite–chalcopyrite ± molybdenite; (III) quartz–pyrite–molybdenite–chalcopyrite–sphalerite; and (IV) quartz–calcite–minor pyrite. Liquid-rich two-phase aqueous (L-type), vapour-rich aqueous (V-type) and daughter-minerals three-phase (S-type) fluid inclusions (FIs) were identified at Huaduoshan. The last two types of FIs are absent in stages III and IV. The homogenization temperatures of FIs from stages I to IV are 375–438, 335–378, 283–335, and 223–267 ℃, with corresponding salinities of 2.4–50.4, 2.1–44.9, 2.7–10.1, and 1.7–7.3 wt. % NaCl eqv., respectively. The H–O isotope data of quartz in stages I (δ18OH2O = 6.1–8.0‰, δDH2O = −102.4–−94.6‰) show a magmatic origin of ore-forming fluid; the decreasing δ18OH2O (−6.8–3.2‰) and δDH2O (−117.1–−98.5‰) values of quartz in stage II–IV show the fluid mixing with meteoric water. The S–Pb isotopic values (δ34S = −2.7–0.8; 206Pb/204Pb = 18.236–18.599; 207Pb/204 Pb = 15.504–15.557; 208Pb/204Pb = 37.816–38.629) of pyrites indicate that the ore-forming materials are of magmatic origin. Fluid boiling and mixing may be the major mechanisms of ore precipitation. Zircon U–Pb age (172.1 ± 0.5 Ma) and geochemical data indicate that the ore-related granodiorites are I-type rocks formed in the subduction setting of the Paleo-Pacific Ocean Plate in the Early–Middle Jurassic. In conclusion, we propose that the Huaduoshan Cu–Mo prospect is a porphyry deposit and has potential for further exploration of porphyry Cu–Mo prospecting. [ABSTRACT FROM AUTHOR]

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The area northeast of Sudbury, Ontario, is well known for hosting one of the largest unexplained geophysical anomalies in the Canadian Shield, the Temagami Anomaly. In search of a geological explanation for this anomaly, low-grade metamorphic ultrabasic dykes have been discovered in the overlying Huronian Supergroup sedimentary rocks, both in outcrop and in a deep drill core. Here, we report on the first geochemical and geochronological data obtained on these dykes and compare these data with known magmatic units in and around the 1850 Ma impact-generated Sudbury Igneous Complex (SIC). The NW-striking dykes, which cut across sedimentary rocks of the ca. 2.3 Ga Cobalt Group, and which are, in turn, crosscut by pseudotachylitic breccia, are characterized by distinctively high concentrations of Ti, P, Nb, and Zr, highly fractionated rare earth element patterns (La/YbN 7.6–15.5), and a lack of crustal contamination (Nb/Th > 10). Such features are typical of modern ocean island basalts but very different from Palaeoproterozoic rocks previously documented in the wider region. Multigrain U–Pb laser ablation inductively coupled plasma mass spectrometry analyses performed on magmatic titanite and apatite with high Th/U ratios yielded 1876.0 ± 8.7 and 1880.9 ± 8.3 Ma, respectively, which we interpret as the intrusion age of the dykes. This interpretation is supported by similar whole-rock Sm-Nd model ages of 1890–2000 Ma (initial εNd +2.5). This magmatic event in the footwall of the SIC shortly before the impact was coeval with, and likely genetically related to, the 1.88–1.87 Ga Circum-Superior Large Igneous Province. [ABSTRACT FROM AUTHOR]

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The article presents a study related to rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska. It mentions that Complexities of mélange sections of accretionary prisms include varying degrees of metamorphism of blocks that also have variable origins and different metamorphic paths, preserved within a matrix that may have a different metamorphic grade.

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The article discusses spanning 2500 km along the western margin of North America from the Yukon and Northwest Territories, Canada, to Montana, Wyoming, and Idaho, United States, have diabase dykes, sills, and basaltic volcanic rocks. Topics include the northwestern United States, the Gunbarrel LIP has exposed in several geological settings; and U–Pb zircon ages for Gunbarrel sills within the study area for the Rogers Pass and Turah sills.

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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.)

The Middle Mountain Metamorphic Domain of the Montana Metasedimentary Terrane, northwestern Wyoming Craton, within the northwestern Tobacco Root Mountains, mainly comprises migmatized tonalitic gneiss interlayered with amphibolitic (hornblende) gneiss, both of which are cut by metamorphosed mafic rocks. Together, these gneisses are defined as Middle Mountain Gneiss. Archean tonalitic gneiss from west of, and amphibolitic gneiss from east of, the Bismark Fault give, from chemically and air-abraded zircon grains, U-Pb ID-TIMS ages of 3325.5 ±1.7 and 3340 Ma, respectively. These results reflect primary magmatic ages and show that the Middle Mountain Gneiss extends into the northern area of the Central Fault Block, between the Bismark and Mammoth faults. Older crustal processes in the tonalitic gneiss are evidenced by inherited grains, the oldest of which is >3460 Ma. A metabasite hosted in tonalitic gneiss in the Bismark Fault selvage zone yields a zircon age of 2468 Ma, which is interpreted as the time of metamorphism. This date and other ca. 2470 Ma dates known in the region reflect a series of thermotectonic events designated here as the Beaverhead - Tobacco Root Orogeny. Geochemical evidence in the Central Fault Block metabasites suggests that their >2470 Ma precursors evolved in a back-arc - arc-rift setting, whereas their equivalents west of the Bismark Fault were largely mid-ocean ridge basalt-related tholeiites and east of the Central Fault Block were back-arc tholeiites showing some continental affinity. The metabasite was metamorphosed, deformed, and intruded by pegmatite at 1756 Ma during the Big Sky Orogeny. This orogenic event also produced new zircon growth in Archean tonalitic gneiss. Monazite with an age of 75 Ma, found at one location, reflects nearby intrusion of the Cretaceous Tobacco Root Batholith. Le domaine métamorphique de Middle Mountain dans le terrane métasédimentaire du Montana, nord-ouest du craton Wyoming, nord-ouest des monts Tobacco Root, comprend surtout des gneiss tonalitiques migmatisés interstratifiés avec des gneiss amphibolitiques (hornblende); les deux sont recoupés par des roches mafiques métamorphisées. Ensemble, ces gneiss forment le gneiss de Middle Mountain. Un gneiss tonalitique archéen provenant d'un site à l'ouest de la faille Bismark et un gneiss amphibolitique provenant d'un site à l'est de cette faille ont donné des âges U-Pb ID-TIMS respectifs de 3325,5 ±1,7 et 3340 Ma, sur des zircons prétraités par abrasion chimique ou par abrasion à l'air. Ces résultats reflètent des âges magmatiques primaires et montrent que le gneiss de Middle Mountain s'étend dans le secteur nord du Central Fault Block, entre les failles Bismark et Mammoth. Des processus plus anciens de la croûte dans le gneiss tonalitique sont mis en évidence par des grains hérités, dont le plus ancien date de >3460 Ma. Une métabasite encaissée dans un gneiss tonalitique dans la zone de salbande de la faille Bismark a donné un âge sur zircon de 2468 Ma, ce qui est interprété comme le moment du métamorphisme. Cette datation et d'autres autour de 2470 Ma connues dans la région sont le reflet d'une série d'événements thermo-tectoniques désignés ici sous l'appellation orogène Beaverhead - Tobacco Root. Les évidences géochimiques dans les métabasites du Central Fault Block suggèrent que leurs précurseurs >2470 Ma aient évolué dans un environnement d'arrière-arc - arc de distension, alors que leurs équivalents à l'ouest de la faille Bismark était largement des tholéiites reliés à des basaltes de dorsale médio-océanique et, à l'est du Central Fault Block, étaient des tholéiites d'arrière-arc montrant une certaine affinité continentale. La métabasite était métamorphisée, déformée et une pegmatite l'a pénétrée à 1756 Ma durant l'orogène Big Sky. Cet événement orogénique a aussi engendré une nouvelle croissance de zircons dans le gneiss tonalitique archéen. Une monazite, âgée de 75 Ma, trouvée à un site, reflète l'intrusion avoisinante du batholite Tobacco Root, au Crétacé. [ABSTRACT FROM AUTHOR]

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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.)

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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.)

Combined mapping, U-Pb isotope dilution - thermal ionization mass spectrometry (ID-TIMS) geochronology and geochemical studies in Harvey-Cardiff domain in the western Composite Arc Belt reveal the presence of a long-lived magmatic-metamorphic history between 1290 and 1030 Ma. Following intrusion of gneissic tonalite of the Anstruther and Burleigh gneiss complexes at ca. 1290 Ma, diorite of the Salmon Burn intrusive complex was emplaced at 1242.1 ±1.1 Ma. A potassium-feldspar megacrystic monzogranite in the Salerno Creek deformation zone that forms the boundary between Harvey-Cardiff domain and Bancroft terrane was emplaced at 1211.3 ±1.5 Ma, similar to the 1220 ±1.6 Ma old Junction pluton and a previously reported age of ca. 1229 Ma from another Methuen suite granite in the domain. All three ages are 20 to 30 million years younger than Methuen suite ages elsewhere in the Composite Arc Belt (1250-1240 Ma). Deformation along the Salerno Creek deformation zone is constrained between 1211 Ma, the age of the megacrystic monzogranite, and 1050 Ma, the age of titanite grains from the Salmon Burn intrusive complex and a late alkalic dike. A monzogranite of the newly recognized Catchacoma granite suite yielded an age of 1067 ±3.7 Ma, similar to the 1059.2 ±1.6 Ma age obtained from the Cavendish pegmatite vein. These ages suggest a temporal link between late granite and pegmatite emplacement in Harvey-Cardiff domain. Metamorphic zircon, monazite, and titanite ages fall into three clusters (1082-1070, 1063-1045, and 1037-1030 Ma) and may represent a protracted metamorphic event or reflect distinct pulses during the Ottawan orogeny. Une combinaison de cartographie, d'études géochimiques et de géochronologie U-Pb ID-TIMS dans le domaine Harvey-Cardiff dans la Ceinture d'arcs composite occidentale a révélé la présence d'un historique magmatique-métamorphique de longue durée entre 1290 et 1030 Ma. Après l'intrusion d'une tonalite gneissique des complexes gneissiques Anstruther et Burleigh vers 1290 Ma, la diorite du complexe intrusif de Salmon Burn a été mise en place à 1242,1 ±1,1 Ma. Un monzogranite potassium-feldspath à mégacristaux dans la zone de déformation Salerno Creek, laquelle forme la limite entre le domaine Harvey-Cardiff et le terrane de Bancroft, a été mis en place à 1211,3 ±1,5 Ma, ce qui est semblable au pluton Junction (1220 ±1,6 Ma) et un âge, rapporté antérieurement, d'environ 1229 Ma provenant d'un autre granite dans la suite de Methuen dans le domaine. Ces trois âges sont de 20 à 30 Ma plus jeunes que les âges de la suite Methuen ailleurs dans la Ceinture d'arcs composite (1250-1240 Ma). La déformation le long de la zone de déformation Salerno Creek est fixée entre 1211 Ma, l'âge du monzogranite macrocristallin, et 1050 Ma, l'âge des grains de titanite du complexe intrusif Salmon Burn et un dyke alcalin tardif. Un monzogranite de la suite granitique Catchacoma, nouvellement reconnue, a donné un âge de 1067 ±3,7 Ma, semblable à l'âge de 1059,2 ±1,6 Ma obtenu d'une veine de pegmatite Cavendish. Ces âges suggèrent un lien temporel entre la mise en place de la pegmatite et du granite tardifs dans le domaine Harvey-Cardiff. Les âges du zircon métamorphique, de la monazite et de la titanite forment trois ensembles : 1082-1070, 1063-1045 et 1037-1030 Ma pouvant représenter un événement métamorphique prolongé ou être le reflet de pulsations distinctes dans l'orogène d'Ottawa. [ABSTRACT FROM AUTHOR]

High-precision U-Pb isotope dilution - thermal ionization mass spectrometry (ID-TIMS) geochronology on chemically abraded zircon grains from a noritic gabbro of the Ni-bearing Suwar mafic-ultramafic layered complex, northwestern Yemen, gives a mean 206Pb/238U age of 638.46 ±0.73 Ma (2σ; MSWD = 1.4). At Wadi Qutabah, ~30 km to the north, a similar mafic sample has an identical age of 638.58 0.51 Ma (2σ; MSWD = 0.32), which supports the possibility of there being a single, large intrusive complex with an estimated areal extent of ~250 km2. This is supported by geochemical data of samples from each locality, which are postkinematic, gabbroic rocks that contain variable amounts of cumulus olivine, plagioclase, orthopyroxene, and ilmenite with intercumulus augite, hornblende, and Ni-sulphides. Straight rare Earth element (REE) patterns, Ba/La ~30, Rb/Ba ~0.04, and negative primitive-mantle-normalized P anomalies resemble EM1 (Enriched Mantle 1) of oceanic island basalts and Archean subcontinental mantle lithosphere. The mineralogy and magmatic/tectonic discrimination diagrams suggest within-plate continental tholeiitic and noritic cumulates typical of a rift setting for both intrusions. The complex intrudes retrograded, amphibolite-facies paragneiss of the Pan-African Afif lithotectonic terrane, and is generally undeformed and unaltered, and, therefore, unaffected by the Pan-African orogeny. Emplacement of the 639 Ma complex occurred during a tensional tectonic regime on the Arabian Peninsula and marks the time of proto-Iapetan rifting. The estimated size of the intrusion, its noritic composition, and Archean subcontinental lithospheric mantle signature and its position in thin Proterozoic lithosphere abutting Archean cratonic rocks, give it the key characteristics of known, mostly Proterozoic, intrusions that host world-class Ni-Cu-Co ore deposits. De la géochronologie U-Pb ID-TIMS à haute précision sur des grains de zircons abrasés chimiquement provenant d'un gabbro noritique du complexe nickélifère lité, mafique-ultramafique de Suwar, dans le Nord-Ouest du Yémen, a donné un âge de 206Pb/238U age of 638,46 ±0,73 Ma (2σ; MSWD = 1,4). À Wadi Qutabah, à ~30 km vers le nord, un échantillon mafique similaire présente un âge identique de 638,58 0,51 Ma (2σ; MSWD = 0,32), ce qui supporte la possibilité qu'il n'existe qu'un seul grand complexe intrusif dont l'étendue aurait ~ 250 km2. Cette hypothèse est supportée par des données géochimiques d'échantillons de chaque localité, soit des roches gabbroïques post-cinématiques qui contiennent des quantités variables d'olivine, de plagioclase, d'orthopyroxène et d'ilménite de la phase cumulus avec de l'augite, de la hornblende et des sulfures de nickel de la phase intercumulus. Des patrons d'éléments de terres rares rectilignes, Ba/La ~30, Rb/Ba ~ 0,04 et des anomalies P négatives, normalisées pour le manteau primitif ressemblent au EM1 (Enriched Mantle 1) des basaltes d'îles océaniques et à la lithosphère du manteau subcontinental archéen. La minéralogie et les diagrammes de discrimination magmatique/tectonique suggèrent, à l'intérieur de la plaque continentale, des cumulats tholéiitiques et noritiques typiques d'un environnement de distension pour les deux intrusions. Le complexe pénètre des paragneiss rétrogradés, au faciès des amphibolites du terrane lithotectonique pan-africain Afif; en général, il est non déformé et non altéré, donc non affecté par l'orogène pan-africain. La mise en place du complexe de 639 Ma a eu lieu durant un régime tectonique de tension sur la péninsule d'Arabie et elle marque le moment de la distension de l'océan Iapetus primitif. La dimension estimée de l'intrusion, sa composition noritique, la signature du manteau lithosphérique subcontinental archéen et sa position dans la mince lithosphère protérozoïque adjacente aux roches cratoniques archéennes, lui donnent les caractéristiques clés d'intrusions connues, datant surtout du Protérozoïque, qui contiennent des gisements de minerai Ni-Cu-Co de classe mondiale. [ABSTRACT FROM AUTHOR]

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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.)

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.)