scholarly journals Tonalite-Dominated Magmatism in the Abitibi Subprovince, Canada, and Significance for Cu-Au Magmatic-Hydrothermal Systems

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 242 ◽  
Author(s):  
Lucie Mathieu ◽  
Alexandre Crépon ◽  
Daniel J. Kontak
Keyword(s):  
Volcanic Rocks ◽  
Significant Proportion ◽  
Hydrothermal Systems ◽  
Heavy Rare Earth ◽  
Geological Surveys ◽  
Abitibi Subprovince ◽  
Heavy Rare Earth Elements ◽  
Pressure Melting ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

In Archean greenstone belts, magmatism is dominated by intrusive and volcanic rocks with tholeiitic affinities, as well as tonalite- and granodiorite-dominated large-volume batholiths, i.e., tonalite–trondhjemite–granodiorite (TTG) suites. These intrusions are associated with poorly documented mineralization (Cu-Au porphyries) that, in the Neoarchean Abitibi Subprovince (>2.79 to ~2.65 Ga), Superior Province, Canada, are associated with diorite bearing plutons, i.e., tonalite–trondhjemite–diorite (TTD) suites. The importance of TTG versus TTD suites in the evolution of greenstone belts and of their magmatic-hydrothermal systems and related mineralization is unconstrained. The aim of this study was to portray the chemistry and distribution of these suites in the Abitibi Subprovince. The study used data compiled by the geological surveys of Québec and Ontario to evaluate the chemistry of TTG and TTD suites and uncovered two coeval magmas that significantly differentiated (fractional crystallization mostly): 1) a heavy rare earth elements (HREE)-depleted tonalitic magma from high pressure melting of an hydrated basalt source; and 2) a hybrid HREE-undepleted magma that may be a mixture of mantle-derived (tholeiite) and tonalitic melts. The HREE-depleted rocks (mostly tonalite and granodiorite) display chemical characteristics of TTG suites (HREE, Ti, Nb, Ta, Y, and Sr depletion, lack of mafic unit, Na-rich), while the other rocks (tonalite and diorite) formed TTD suites. Tonalite-dominated magmatism, in the Abitibi Subprovince, comprises crustal melts as well as a significant proportion of mantle-derived magmas and this may be essential for Cu-Au magmatic-hydrothermal mineralizing systems.

Rubidium–strontium ages from the Oxford Lake – Knee Lake greenstone belt, northern Manitoba

1980 ◽  
Vol 17 (5) ◽  
pp. 560-568 ◽  
Author(s):  
G. S. Clark ◽  
S.-P. Cheung
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Superior Province ◽  
Granitic Intrusion ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

Rb–Sr whole-rock ages have been determined for rocks from the Oxford Lake – Knee Lake – Gods Lake greenstone belt, in the Superior Province of northeastern Manitoba.The age of the Magill Lake Pluton is 2455 ± 35 Ma (λ87Rb = 1.42 × 10−11 yr−1), with an initial 87Sr/86Sr ratio of 0.7078 ± 0.0043. This granitic stock intrudes the Oxford Lake Group, so it is post-tectonic and probably related to the second, weaker stage of metamorphism.The age of the Bayly Lake Pluton is 2424 ± 74 Ma, with an initial 87Sr/86Sr ratio of 0.7029 ± 0.0001. This granodioritic batholith complex does not intrude the Oxford Lake Group. It is syn-tectonic and metamorphosed.The age of volcanic rocks of the Hayes River Group, from Goose Lake (30 km south of Gods Lake Narrows), is 2680 ± 125 Ma, with an initial 87Sr/86Sr ratio of 0.7014 ± 0.0009.The age for the Magill Lake and Bayly Lake Plutons can be interpreted as the minimum ages of granitic intrusion in the area.The age for the Hayes River Group volcanic rocks is consistent with Rb–Sr ages of volcanic rocks from other Archean greenstone belts within the northwestern Superior Province.

Petrogenesis of the Upper Cretaceous volcanism in the Kefken region, Western Pontides, NW Turkey

2021 ◽  
Author(s):  
Turgut Duzman ◽  
Ezgi Sağlam ◽  
Aral I. Okay
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Early Eocene ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Elements ◽  
Cretaceous Volcanism ◽  
Oceanic Slab

<p>The Upper Cretaceous volcanic and volcaniclastic rocks crop out along the Black Sea coastline in Turkey. They are part of a magmatic arc that formed as a result of northward subduction of the Tethys ocean beneath the southern margin of Laurasia. The lower part of the Upper Cretaceous volcanism in the Kefken region, 100 km northeast of Istanbul, is represented by basaltic andesites, andesites, agglomerates and tuffs, which have yielded Late Cretaceous (Campanian, ca. 83 Ma) U-Pb zircon ages. The volcanic and volcanoclastic rocks are stratigraphically overlain by shallow to deep marine limestones, which range in age from Late Campanian to Early Eocene.  Geochemically, basaltic andesites and andesites display negative anomalies in Nb, Ta and Ti, enrichment in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). Light rare earth elements (LREE) show slightly enrichment relative to heavy rare earth elements (La<sub>cn</sub>/Yb<sub>cn</sub> =2.51-3.63) and there are slight negative Eu anomalies (Eu/Eu* = 0.71-0.95) in basaltic andesite and andesite samples. The geochemical data indicate that Campanian volcanic rocks were derived from the partial melting of the mantle wedge induced by hydrous fluids released by dehydration of the subducted oceanic slab.</p><p>There is also a horizon of volcanic rocks, about 230 m thick, within the Late Campanian-Early Eocene limestone sequence.  This volcanic horizon, which consists of pillow basalts, porphyritic basalts,  andesites and dacites, is of Maastrichtian age based on paleontological data from the intra-pillow sediments and U-Pb zircon ages from the andesites and dacites (72-68 Ma).  The Maastrichtian andesites and dacites are geochemically distinct from the Campanian volcanic rocks. They show distinct adakite-like geochemical signatures with high ratios of Sr/Y (>85.5), high La<sub>cn</sub>/Yb<sub>cn </sub>(16.4-23.7) ratios, low content of Y (7.4-8.6 ppm) and low content of heavy rare-earth elements (HREE). The adakitic rocks most probably formed as a result of partial melting of the subducting oceanic slab under garnet and amphibole stable conditions.</p><p>The Upper Cretaceous arc sequence in the Kefken region shows a change from typical subduction-related magmas to adakitic ones, accompanied by decrease in the volcanism.</p><p> </p><p> </p>

scholarly journals Petrogenetic Study of the Multiphase Chibougamau Pluton: Archaean Magmas Associated with Cu–Au Magmato-Hydrothermal Systems

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 174 ◽  
Author(s):  
Lucie Mathieu ◽  
Denis Racicot
Keyword(s):  
Chemical Evolution ◽  
Hydrothermal System ◽  
Hydrothermal Systems ◽  
Historical Mining ◽  
Magmatic Rocks ◽  
Emplacement Mechanism ◽  
Greenstone Belts ◽  
Archean Greenstone Belts ◽  
Heterogeneous Source ◽  
Metasomatized Mantle

The Chibougamau pluton is a Neoarchean multiphase intrusion that is related to Cu–Au porphyry-style deposits. In Archean greenstone belts, porphyries are marginal and poorly documented mineralizations. Such deposits are, however, important in the Chibougamau area, where the main historical mining camp (Central Camp) is a magmato-hydrothermal system. Understanding such systems requires documenting the related magmatic rocks. This contribution focuses on the petrogenesis of the Chibougamau pluton to elucidate how the intrusion participated in Cu and Au mineralized systems. Using field descriptions, whole-rock analyses, and petrographic observations, we describe the source, emplacement mechanism, and chemical evolution of the Chibougamau pluton. The Chibougamau pluton is a TTD (tonalite-trondhjemite-diorite) suite that contains more K than most plutons of similar age. This suite was produced from a heterogeneous source; i.e., a hydrated basalt and possibly a metasomatized mantle. These are rare (and thus prospective) characteristics for an Archean intrusion. In addition, differentiation may have been sufficiently prolonged in the diorite phase to concentrate metals and fluids in the evolved magma. These magmatic constraints must now be tested against a renewed understanding of the Cu-dominated mineralized systems of the Chibougamau area.

scholarly journals Criteria for the recognition of Archean calc-alkaline lamprophyres: examples from the Abitibi Subprovince

2018 ◽  
Vol 55 (2) ◽  
pp. 188-205 ◽  
Author(s):  
Lucie Mathieu ◽  
Émile Bouchard ◽  
Francis Guay ◽  
Alizée Liénard ◽  
Pierre Pilote ◽  
...  
Keyword(s):  
Mineral Exploration ◽  
Gold Deposits ◽  
Chemical Analyses ◽  
Calc Alkaline ◽  
Thin Sections ◽  
Mafic Intrusions ◽  
Abitibi Subprovince ◽  
Greenstone Belts ◽  
Archean Greenstone Belts ◽  
Alkaline Lamprophyres

Lamprophyres are minor intrusions with atypical sources and crystallisation sequences. Among lamprophyres, the calc-alkaline (CAL) type on which this study focuses has the least distinctive chemistry and petrology. CAL correspond to small-volume mafic intrusions characterised by the early fractionation of amphibole and (or) biotite. In the Archean Superior Province (Canada), CAL are temporally and spatially related to several gold deposits and may thus be relevant to mineral exploration. This study focuses on several altered and metamorphosed intrusions of the Abitibi and La Grande subprovinces, which were designated lamprophyres based on field observations. Several criteria established from thin sections, whole-rock chemical analyses, and SEM data are applied to the studied rocks to distinguish CAL from other types of magma. As a result, only one of the studied dykes has the morphology, chemistry, and petrology typical of CAL, while the other intrusions are either too altered to be classified or may correspond to metamorphosed and metasomatized gabbro and diorite. This study shows that thin sections and whole-rock chemical analyses are not always sufficient to unequivocally classify an altered and metamorphosed intrusion as a CAL. Also, intrusions as challenging to recognise as CAL should not be used by exploration geologists to prospect for orogenic gold deposits. Much remains to be done to document the distribution and volume represented by lamprophyres in Archean greenstone belts and to confirm their spatial dependence with gold deposits.

The sulfur content of Archean volcanic rocks and a comparison with ocean floor basalts

1978 ◽  
Vol 15 (5) ◽  
pp. 715-728 ◽  
Author(s):  
A. J. Naldrett ◽  
A. M. Goodwin ◽  
T. L. Fisher ◽  
R. H. Ridler
Keyword(s):  
Major Element ◽  
Sea Water ◽  
Volcanic Rocks ◽  
Direct Interaction ◽  
Ocean Floor ◽  
Major Element Composition ◽  
Lake Of The Woods ◽  
Fe Content ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

In this paper we report the sulfur contents of 1056 basalts, andesites, dacites and rhyolites of known major element composition from the Rankin–Ennadai, Birch Lake – Uchi Lake, Lake of the Woods – Wabigoon Lake, Timmins and Skead Archean greenstone belts of the Canadian Shield. The sulfur contents of 299 ocean floor basalts and 68 sub-aerial or shallow water extrusive rocks are also reported. Sulfur contents for rocks of a given class are highly variable, ranging from near zero to several thousand parts per million (ppm). However, when averages for each of the rock classes are examined, the data from the two best documented of the Archean greenstone belts exhibit the same positive correlation between sulfur and total Fe content of the rocks. The trend for the Rankin–Ennadai belt coincides almost exactly with that reported earlier for the Blake River Group, approximating that expected if the rocks were saturated in sulfide at the time of extrusion. Rocks from the Lake of the Woods – Wabigoon Lake, Timmins and Skead areas seem to be somewhat poorer in sulfur than those from the Rankin–Ennadai and Blake River belts.Despite the fact that all evidence in the literature for fresh glassy pillow rims indicates that modern ocean floor basalts are saturated in sulfide, our average values for these ocean floor rocks are much lower than the predicted saturation levels, suggesting that the rocks have lost one-half to three-fourths of their sulfur, presumably through reaction with sea water. It is suggested that the reason for the Archean basalts retaining most of their sulfur despite the extensive redistribution that has occurred, whereas modern ocean floor basalts lose so much, may be due to the Archean rocks accumulating much more quickly and being exposed to direct interaction with sea water for a much shorter time than the modern rocks.

Constraints on early Archean crustal extraction and tholeiitic-komatiitic volcanism in greenstone belts of the Northern Superior Province

2003 ◽  
Vol 40 (3) ◽  
pp. 431-445 ◽  
Author(s):  
Charles Maurice ◽  
Don Francis ◽  
Louis Madore
Keyword(s):  
Mantle Source ◽  
Volcanic Rocks ◽  
Major Elements ◽  
Chemical Characteristics ◽  
Superior Province ◽  
Mantle Sources ◽  
Volcanic Events ◽  
Greenstone Belts ◽  
Archean Greenstone Belts ◽  
Ree Patterns

Numerous small remnants of Archean greenstone belts in the Northern Superior Province (ca. 2875–2710 Ma) have chemical characteristics similar to those of the larger greenstone belts of the Southern Superior Province, and preserve direct evidence of crustal conditions prior to the major volcanic events of the late Archean (Wawa–Abitibi subprovinces; ca. 2760–2700 Ma). Three of the best preserved belts are engulfed in tonalite intrusions of the Faribault-Thury Complex (FTC) and exhibit common chemical characteristics, which may imply a similar origin. The dominant tholeiitic basalts typically have MgO contents > 7 wt.%, TiO2 < 1 wt.% and nearly flat rare-earth element (REE) patterns (La/Smn = 0.77–1.22; Gd/Ybn = 0.86–1.20). Associated komatiites have flat to depleted REE patterns (La/Smn = 0.45–0.95), high Al2O3/TiO2 (>15), low CaO/Al2O3 (<1.2), and chondritic Gd/Yb ratios similar to 2.7 Ga Al-undepleted komatiites. The trace-element ratios of komatiitic rocks are indistinguishable from those of the associated tholeiites, suggesting either a derivation from similar mantle sources or a comagmatic relationship (Nb/Thpm = 0.8–1.1; La/Cepm = 0.9–1.3; Nb/Ce = 0.7–0.9; Y/Hopm ~1; and Th/Lapm = 0.7–1.1). Numerical modelling of trace and major elements during low-pressure crystal fractionation reproduces the spectrum of both inferred liquid and cumulate compositions and is consistent with a comagmatic origin between the komatiites and tholeiites. The relatively low Nb/Th ratios of these mid-Archean volcanic rocks relative to both modern day basalts and late Archean basalts may indicate that they were derived from a mantle source that had not lost its crustal components, nor seen significant recycled oceanic crust (high Nb/Th). The extraction of continental crust from this Archean mantle source might then postdate the FTC volcanism, and may be associated with the generation of the voluminous tonalites that engulf the belts.

scholarly journals Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 966
Author(s):  
Baptiste Madon ◽  
Lucie Mathieu ◽  
Jeffrey H. Marsh
Keyword(s):  
Oxygen Fugacity ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Chemical Diversity ◽  
Temporal Association ◽  
Volatile Content ◽  
Abitibi Subprovince

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

Sign in / Sign up

Export Citation Format

Share Document