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.

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.

Chronostratigraphic constraints on the genesis of Archean greenstone belts, northwestern Superior Province, Ontario, Canada

1998 ◽  
Vol 92 (3) ◽  
pp. 277-295 ◽  
Author(s):  
Fernando Corfu ◽  
Donald W. Davis ◽  
Denver Stone ◽  
Michelle L Moore
Keyword(s):  
Superior Province ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

scholarly journals Upper Cretaceous to Pleistocene melilitic volcanic rocks of the Bohemian Massif: petrology and mineral chemistry

2015 ◽  
Vol 66 (3) ◽  
pp. 197-216 ◽  
Author(s):  
Roman Skála ◽  
Jaromír Ulrych ◽  
Lukáš Ackerman ◽  
Lukáš Krmíček ◽  
Ferry Fediuk ◽  
...  
Keyword(s):  
Mantle Source ◽  
Bohemian Massif ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Mineral Chemistry ◽  
Primitive Mantle ◽  
Mantle Sources ◽  
Heterogeneous Mantle ◽  
Central European Volcanic Province ◽  
Scoria Cones

Abstract Upper Cretaceous to Pleistocene volcanic rocks of the Bohemian Massif represent the easternmost part of the Central European Volcanic Province. These alkaline volcanic series include rare melilitic rocks occurring as dykes, sills, scoria cones and flows. They occur in three volcanic periods: (i) the Late Cretaceous to Paleocene period (80–59 Ma) in northern Bohemia including adjacent territories of Saxony and Lusatia, (ii) the Mid Eocene to Late Miocene (32.3–5.9 Ma) period disseminated in the Ohře Rift, the Cheb–Domažlice Graben, Vogtland, and Silesia and (iii) the Early to Late Pleistocene period (1.0–0.26 Ma) in western Bohemia. Melilitic magmas of the Eocene to Miocene and Pleistocene periods show a primitive mantle source [(143Nd/144Nd)t=0.51280–0.51287; (87Sr/86Sr)t=0.7034–0.7038)] while those of the Upper Cretaceous to Paleocene period display a broad scatter of Sr–Nd ratios. The (143Nd/144Nd)t ratios (0.51272–0.51282) of the Upper Cretaceous to Paleocene rocks suggest a partly heterogeneous mantle source, and their (87Sr/86Sr)t ratios (0.7033–0.7049) point to an additional late- to post-magmatic hydrothermal contribution. Major rock-forming minerals include forsterite, diopside, melilite, nepheline, sodalite group minerals, phlogopite, Cr- and Ti-bearing spinels. Crystallization pressures and temperatures of clinopyroxene vary widely between ~1 to 2 GPa and between 1000 to 1200 °C, respectively. Nepheline crystallized at about 500 to 770 °C. Geochemical and isotopic similarities of these rocks occurring from the Upper Cretaceous to Pleistocene suggest that they had similar mantle sources and similar processes of magma development by partial melting of a heterogeneous carbonatized mantle source.

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.

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.

Petrogenesis of mantle-derived, LILE-enriched Archean monzodiorites and trachyandesites (sanukitoids) in southwestern Superior Province

1989 ◽  
Vol 26 (9) ◽  
pp. 1688-1712 ◽  
Author(s):  
Richard A. Stern ◽  
Gilbert N. Hanson ◽  
Steven B. Shirey
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Mantle Source ◽  
Earth Element ◽  
Crustal Contamination ◽  
Mantle Peridotite ◽  
Superior Province ◽  
Source Regions ◽  
Enriched Mantle ◽  
Ree Patterns

In southwestern Superior Province, diorite, monzodiorite, and trachyandesite ("sanukitoids") occurring within syn- to post-tectonic intrusive complexes and within greenstone belts have the following chemical characteristics: 55–60 wt.% SiO2, MgO > 6 wt.%, Mg# > 0.60, Ni and Cr both > 100 ppm, Na2O + K2O = 6 wt.%, Sr and Ba both 600–1800 ppm, and rare-earth-element (REE) patterns that are strongly light rare-earth-element (LREE) enriched (Cen = 80–250, Ybn = 4 – 10) and show no Eu anomalies. Sanukitoids and their granodioritic derivatives constitute at least 5% of the exposed crust in the study area. The sanukitoids cannot be derived by melting, fractionation, or crustal contamination of basalts or lamprophyres that are coeval with the sanukitoids. Crustal contamination of komatiites fails to explain the high large-ion-lithophile-element (LILE) contents of the sanukitoids. Rather, we suggest that the sanukitoids were derived by hydrous melting of LILE-enriched mantle peridotite at pressures between 10 and 15 kbar. The sanukitoids with steepest REE patterns have the lowest FeO contents, indicating that the part of the mantle source with the highest Mg# had the most fractionated REE pattern prior to melting. Mantle source regions to the sanukitoids had different Mg#'s and were enriched in LILE's (metasomatized) to varying extents by fluids of crustal or mantle origin prior to melting.

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