Pontiac metavolcanic rocks within the Cadillac tectonic zone, McWatters, Abitibi Belt, Quebec

1993 ◽  
Vol 30 (7) ◽  
pp. 1521-1531 ◽  
Author(s):  
David Morin ◽  
Michel Jébrak ◽  
Marc Bardoux ◽  
Normand Goulet
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Rare Earth Element ◽  
Greenstone Belt ◽  
Earth Element ◽  
Calc Alkaline ◽  
Tectonic Zone ◽  
Southern Boundary ◽  
Abitibi Greenstone Belt ◽  
Metavolcanic Rocks

The McWatters metavolcanic rocks are structurally bounded lenses within the Cadillac tectonic zone on the southern boundary of the Abitibi greenstone belt. They comprise komatiite, tholeiitic basalt and gabbro, and calc-alkaline andesitic lavas and volcaniclastic rocks cut by calc-alkaline dioritic and lamprophyric dykes. The McWatters basalts are mid-ocean-ridge basalt type tholeiites exhibiting low incompatible trace element contents and [La/Yb]N < 1. They may have formed via relatively high degree partial melting of a rare-earth element depleted mantle source. The andesites exhibit chondrite-normalized trace-element patterns with light-rare-earth and large-ion lithophile element enrichments and negative Nb and Ti anomalies, comparable to those of subduction-related calc-alkaline andesites. McWatters units are distinct from nearby Blake River Group rocks, despite comparable lithological assemblages and some common geochemical characteristics. The McWatters basalts exhibit lower Ti/Y, Zr/Y, and La/Yb than the Blake River tholeiites, whereas the McWatters andesites display lower Ti/Zr and higher Zr/Y than the Blake River calc-alkaline units. The McWatters tholeiites can be correlated with northern Pontiac Group tholeiitic units based on similar trace-element ratios and parallel rare-earth-element patterns. Thus, the McWatters tholeiites represent Pontiac rocks, underthrust beneath the southern Abitibi belt and appearing as isolated and retrograded lenses in the Cadillac tectonic zone. They may represent the remnants of an ocean basin that once separated the southern Abitibi greenstone belt from the Pontiac Subprovince.

Geochemical evolution in the Blake River Group, Abitibi Greenstone Belt, Superior Province

1980 ◽  
Vol 17 (9) ◽  
pp. 1292-1299 ◽  
Author(s):  
I. E. M. Smith
Keyword(s):  
Rare Earth ◽  
Volcanic Rock ◽  
Rare Earth Element ◽  
Greenstone Belt ◽  
Earth Element ◽  
Superior Province ◽  
Calc Alkaline ◽  
Abitibi Greenstone Belt ◽  
Rock Types ◽  
Element Fractionation

In well exposed, well developed greenstone belts of the Superior Province there is a clear progression from stratigraphically lower, geochemically primitive volcanic rock types (komatiites, tholeiites) to overlying geochemically evolved calc-alkaline volcanic rock types. In the western Blake River Group of the Abitibi Greenstone Belt the change from tholeiitic to calc-alkaline volcanics represents a geochemical discontinuity defined by an increase in incompatible elements and light/heavy rare-earth element fractionation in the overlying rocks. Quantitative modelling of the parameters of the discontinuity indicates that it can be explained by a change to very small amounts of melting of unmodified mantle lherzolite, although this is not a unique solution. In calc-alkaline suites showing high degrees of rare-earth element fractionation the calculated melt fraction required of unmodified mantle becomes unrealistically low and models involving a geochemically evolved source may have to be considered.

Zircon U-Pb age, Trace Element, and Hf Isotopic Compositions of Nordmarkite in the Lizhuang Rare Earth Element Deposit in the Western Margin of the Yangtze Block

2018 ◽  
Vol 92 (1) ◽  
pp. 225-240 ◽  
Author(s):  
Jiayun ZHOU ◽  
Hongqi TAN ◽  
Daxin GONG ◽  
Zhimin ZHU ◽  
Liping LUO
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Rare Earth Element ◽  
Earth Element ◽  
Yangtze Block ◽  
Western Margin ◽  
Isotopic Compositions

Archean mafic metavolcanics from the Rouyn–Noranda district, Abitibi Greenstone Belt, Quebec. 1. Mobility of the major elements

1982 ◽  
Vol 19 (12) ◽  
pp. 2258-2275 ◽  
Author(s):  
Léopold Gélinas ◽  
Michel Mellinger ◽  
Pierre Trudel
Keyword(s):  
Greenstone Belt ◽  
Great Depth ◽  
Major Elements ◽  
Chemical Degradation ◽  
Type I ◽  
Calc Alkaline ◽  
Calcium Leaching ◽  
Abitibi Greenstone Belt ◽  
Metavolcanic Rocks ◽  
Metamorphic Facies

In a suite of Archean mafic pillows from the Rouyn–Noranda region of Quebec's Abitibi Greenstoné Belt, including both tholeiitic and calc-alkaline varieties spanning the prehnite–pumpellyite to upper greenschist metamorphic facies, three types of alteration can be defined: (I) chlorite–epidote–actinolite; (II) chlorite–epidote; and (III) chlorite ± sericite; the number of mineral phases decreases as a result of progressive hydration from type I to type III alteration. Albitization, resulting from substitution of [Formula: see text], in calcic plagioclase, is highly variable in type I alteration, but in types II and III the plagioclase is totally albitized and in some cases silicified. Chloritization is closely linked to increasing hydration and Ca leaching with MgO and FeO substituting for CaO in ferromagnesian minerals.Calcium was mobilized and carried by solutions, as evidenced by the variable concentration of epidote at the margins of pillows. This calcium leaching generated an excess of Al2O3 with respect to the combined molecular proportions of Na2O, K2O, and CaO, and is shown by the presence of corundum in CIPW norm calculations. In some pillows showing substitution of [Formula: see text], the fo2 of the invading fluid appears to have remained constant, being buffered by the pillow composition; this would be favored by a low water/rock mass ratio. As a result, the initial pillow Fe2O3/FeO ratio remained constant. In other pillows, the fo2 appears to have been imposed by the invading fluid rather than by the mineral assemblage: the FeO/MgO ratios are thus no longer representative of the magmatic composition whereas the ΣFeO/MgO is still representative of the pristine magmatic value.Two types of substitution of CaO by FeO and (or) MgO have been observed: (1) preferential substitution restricted to type I alteration, of FeO over MgO, similar to low-temperature substitution in modern-day sea-floor alteration; and (2) the more common substitution in type II and III alterations in which MgO predominates over FeO, similar to the high-temperature substitution taking place at great depth on the ocean floor.Although the samples were collected to test mineral heterogeneities caused by chemical degradation, more than 40% of the pillows sampled retained their pristine ΣFeO/MgO ratios. The various alteration patterns are independent of the initial tholeiitic or calc-alkaline lineage; this was confirmed using rare earth elements (REE) and inert trace elements such as Zr, Y, and Ti. The chemical changes in the mafic metavolcanic rocks do not obliterate their tholeiitic or calc-alkaline chemical affinities.

Eocene Challis-Kamloops volcanism in central British Columbia: an example from the Buck Creek basin

1998 ◽  
Vol 35 (8) ◽  
pp. 951-963 ◽  
Author(s):  
J Dostal ◽  
D A Robichaud ◽  
B N Church ◽  
P H Reynolds
Keyword(s):  
British Columbia ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Fractional Crystallization ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
The United States ◽  
Calc Alkaline ◽  
Heavy Rare Earth Element

Eocene volcanic rocks of the Buck Creek basin in central British Columbia are part of the Challis-Kamloops volcanic belt extending from the United States across British Columbia to central Yukon. The volcanic rocks include two units, the Buck Creek Formation, composed of high-K calc-alkaline rocks with predominant andesitic composition, and the overlying Swans Lake unit made up of intraplate tholeiitic basalts. Whole rock 40Ar/39Ar data for both units show that they were emplaced at 50 Ma. They have similar mantle-normalized trace element patterns characterized by a large-ion lithophile element enrichment and Nb-Ta depletion, similar chondrite-normalized rare earth element patterns with (La/Yb)n ~4-14 and heavy rare earth element fractionation, and overlapping epsilonNd values (2.4-3.1) and initial Sr-isotope ratios ( ~ 0.704). These features suggest derivation of these two units from a similar mantle source, probably garnet-bearing subcontinental lithosphere. The differences between tholeiitic and calc-alkaline suites can be due, in part, to differences in the depth of fractional crystallization and the crystallizing mineral assemblage. Fractional crystallization of the calc-alkaline magmas began at a greater (mid-crustal) depth and included fractionation of Fe-Ti oxides. The volcanic rocks are probably related to subduction of the Farallon plate under the North American continent in a regime characterized by transcurrent movements and strike-slip faulting.

Fractionation of rare-earth elements during magmatic differentiation and weathering of calc-alkaline granites in southern Myanmar

2016 ◽  
Vol 80 (1) ◽  
pp. 77-102 ◽  
Author(s):  
Kenzo Sanematsu ◽  
Terumi Ejima ◽  
Yoshiaki Kon ◽  
Takayuki Manaka ◽  
Khin Zaw ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Rare Earth Element ◽  
Earth Element ◽  
Geochemical Characteristics ◽  
Magmatic Differentiation ◽  
Calc Alkaline ◽  
Mineral Assemblages ◽  
Weathering Resistance

AbstractGeochemical characteristics and rare-earth element (REE)-bearing minerals of calc-alkaline granites in southern Myanmar were investigated to identify the minerals controlling fractionation between light and heavyREE(LREE and HREE) during magmatic differentiation and weathering. The granites were classified on the basis of the mineral assemblages into two contrasting groups: allanite-(Ce)- and/or titanite-bearing granites; and more HREE-enriched granites characterized by hydrothermal minerals including synchysite(Y), parisite-(Ce), bastnäsite-(Ce), xenotime-(Y), monazite-(Ce), Y-Ca silicate, waimirite-(Y) and fluorite. This suggests that allanite-(Ce) and titanite are not stable in differentiated magma and HREE are eventually preferentially incorporated into the hydrothermal minerals. The occurrence of theREE-bearing minerals is constrained by the degree of magmatic differentiation and the boundary of two contrasting granite groups is indicated by SiO2contents of ∼74 wt.% or Rb/Sr ratios of ∼3–8. Fractionation between LREE and HREE during weathering of the granites is influenced by weathering resistance of theREE-bearing minerals, i.e. allanite-(Ce), titanite, theREEfluorocarbonates and waimirite-(Y) are probably more susceptible to weathering, whereas zircon, monazite-(Ce) and xenotime-(Y) are resistant to weathering. Ion-exchangeableREEin weathered granites tend to be depleted in HREE relative to the whole-rock compositions, suggesting that HREE are more strongly adsorbed on weathering products or that HREE remain in residual minerals.

Two-stage evolution in an Archean tonalite suite: the Taschereau stock, Abitibi (Quebec, Canada)

1991 ◽  
Vol 28 (2) ◽  
pp. 172-183 ◽  
Author(s):  
Michel Jébrak ◽  
Luc Harnois
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Trace Element ◽  
Greenstone Belt ◽  
Shear Zones ◽  
Granitic Rocks ◽  
Element Abundances ◽  
Abitibi Greenstone Belt ◽  
Rock Types ◽  
End Members

The Taschereau stock occurs north of Timmins and Val-d'Or, Quebec, in the Abitibi greenstone belt of the Superior Province. This late Archean composite pluton is composed mainly of diorite–tonalite–trondhjemite cut by granitic rocks. Gold–molybdenum occurrences are associated with a zone of albite-rich rocks surrounding the granitic rocks. Diabase dykes and shear zones postdate all rock units. Field and geochemical evidence suggests that the Taschereau stock was emplaced diachronously. Trace-element geochemical modelling shows that trace-element abundances (rare-earth elements, Ti, Zr) of Taschereau granitic rocks are consistent with partial melting of preexisting Taschereau tonalitic rocks and implies that these two rock types are not end members of a single magma that evolved through fractional crystallization.

Rare Earth Element and Trace Element Features of Gold-bearing Pyrite in the Jinshan Gold Deposit, Jiangxi Province

2010 ◽  
Vol 84 (3) ◽  
pp. 614-623 ◽  
Author(s):  
Guangzhou MAO ◽  
Renmin HUA ◽  
Jianfeng GAO ◽  
Kuidong ZHAO ◽  
Guangming LONG ◽  
...  
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Gold Deposit ◽  
Rare Earth Element ◽  
Earth Element ◽  
Jiangxi Province ◽  
Gold Bearing
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