Search engine for discovering works of Art, research articles, and books related to Art and Culture
Javascript must be enabled to continue!
Nd-isotope evolution of Archaean plutonic rocks in southeastern Superior Province
View through CrossRef
The Opatica plutonic belt, Abitibi greenstone belt, and Pontiac Subprovince represent a major proportion of the southeastern Superior Province, which was formed and accreted rapidly between approximately 2.9 and 2.8 Ga. Plutons in these belts are grouped into four types: (i) trondhjemite–tonalite–granodiorite (TTG) suite (2.82–2.69 Ga), (ii) monzodiorite (MZD) suite (2.697–2.669 Ga), (iii) late alkaline granitoid (ALK) suite (2.68–2.67 Ga), and (iv) anatectic granite and monzonite (ANA) suite (2.69–2.64 Ga). The four suites are represented in all belts and show similar petrography and geochemistry. In terms of Nd-isotope composition, the TTG, MZD, and ALK suites are typical of destructive plate margin magmatism and have + 1.4 < initial εNd < +3.7, values which are very similar to that of the Abitibi mantle (εNd + 2.5). The lower values for the ANA suites (εNd + 0.1 to + 2.4) result from recycling of crustal components. In the Opatica belt the ANA granitoids fall on the Nd-isotope evolution curve defined by the Opatica TTG plutons, and are thus considered to be melt products of this suite. However, Abitibi and Pontiac ANA suites show a larger range of εNd, from + 0.1 to + 2.4, compared with + 1.0 to + 1.3 for the Opatica, suggesting more heterogeneous crustal source rock. Recent geological mapping and geophysical studies associated with the Lithoprobe project have suggested that the Opatica belt represents a plutonic belt against which the Abitibi was accreted by subduction-related collision and that the Pontiac Subprovince is dominated by imbricated metasediments related to the final stages of collision in the Abitibi region. The Nd-isotope data provide support for these arguments. Early plutonic suites are mantle derived and related to arc-accretion processes. As the collision process progresses, a more evolved isotopic component is introduced, possibly in relation to sediment subduction into the mantle. Anatexis of the crust in the central Opatica belt and the core of the Pontiac Subprovince resulted in the formation of granites with a crustal signature for Nd isotopes.
Title: Nd-isotope evolution of Archaean plutonic rocks in southeastern Superior Province
Description:
The Opatica plutonic belt, Abitibi greenstone belt, and Pontiac Subprovince represent a major proportion of the southeastern Superior Province, which was formed and accreted rapidly between approximately 2.
9 and 2.
8 Ga.
Plutons in these belts are grouped into four types: (i) trondhjemite–tonalite–granodiorite (TTG) suite (2.
82–2.
69 Ga), (ii) monzodiorite (MZD) suite (2.
697–2.
669 Ga), (iii) late alkaline granitoid (ALK) suite (2.
68–2.
67 Ga), and (iv) anatectic granite and monzonite (ANA) suite (2.
69–2.
64 Ga).
The four suites are represented in all belts and show similar petrography and geochemistry.
In terms of Nd-isotope composition, the TTG, MZD, and ALK suites are typical of destructive plate margin magmatism and have + 1.
4 < initial εNd < +3.
7, values which are very similar to that of the Abitibi mantle (εNd + 2.
5).
The lower values for the ANA suites (εNd + 0.
1 to + 2.
4) result from recycling of crustal components.
In the Opatica belt the ANA granitoids fall on the Nd-isotope evolution curve defined by the Opatica TTG plutons, and are thus considered to be melt products of this suite.
However, Abitibi and Pontiac ANA suites show a larger range of εNd, from + 0.
1 to + 2.
4, compared with + 1.
0 to + 1.
3 for the Opatica, suggesting more heterogeneous crustal source rock.
Recent geological mapping and geophysical studies associated with the Lithoprobe project have suggested that the Opatica belt represents a plutonic belt against which the Abitibi was accreted by subduction-related collision and that the Pontiac Subprovince is dominated by imbricated metasediments related to the final stages of collision in the Abitibi region.
The Nd-isotope data provide support for these arguments.
Early plutonic suites are mantle derived and related to arc-accretion processes.
As the collision process progresses, a more evolved isotopic component is introduced, possibly in relation to sediment subduction into the mantle.
Anatexis of the crust in the central Opatica belt and the core of the Pontiac Subprovince resulted in the formation of granites with a crustal signature for Nd isotopes.
Related Results
Resolving the Hf-Nd paradox of early Earth crust-mantle evolution
Resolving the Hf-Nd paradox of early Earth crust-mantle evolution
<p>One of the fundamental tenets of geochemistry is that the Earth&#8217;s crust has been extracted from the mantle creating a crustal reservoir enriched&...
Pre-Mesozoic evolution of Avalon terranes of southern New England
Pre-Mesozoic evolution of Avalon terranes of southern New England
With the recognition of the Hope Valley shear zone (HVSZ) as a terrane boundary, the Esmond-Dedham terrane (EDT) was subdivided, and the western division was named the Hope Valley ...
Natural Gases of North America, Volumes 1 & 2
Natural Gases of North America, Volumes 1 & 2
Abstract
Discoveries of natural gas in Alaska have resulted from the search for oil, which has continued intermittently since about 1898. In northern Alaska two gas ...
Aspects of the Tectono-magmatic Evolution of Late Mesozoic Silicic Magmatic Systems in Hong Kong
Aspects of the Tectono-magmatic Evolution of Late Mesozoic Silicic Magmatic Systems in Hong Kong
<p>Hong Kong represents a microcosm of the magmatic and tectonic processes that are related to formation of the Southeast China Magmatic Belt (SCMB, ~1,300 km long by 400 km ...
Deciphering Cryptic Multi-Stage Crystal-Melt Separation during Construction of the Tonglu Volcanic–Plutonic Complex, SE China
Deciphering Cryptic Multi-Stage Crystal-Melt Separation during Construction of the Tonglu Volcanic–Plutonic Complex, SE China
Abstract
Revealing the origin of explosive eruptions of silica-rich magma is of paramount importance for understanding the evolution of continental crust and volcani...
On the crumpling and repaving of the North American continent
On the crumpling and repaving of the North American continent
At perhaps the coarsest scale of consideration, the rock cycle operates through fluxes associated with tectonic uplift and erosion, which are generally balanced by subsidence/subdu...
Geology of the Florida Mountains, southwestern New Mexico
Geology of the Florida Mountains, southwestern New Mexico
The Florida Mountains are an eastward-tilted Basin and Range fault block approximately 24 km (15 mi) southeast of Deming. The mountains are surrounded by a broad bajada that slopes...
Differences in Geochemical Signatures and Petrogenesis between the Van Canh and Ben Giang-Que Son Granitic Rocks in the Southern Kontum Massif, Vietnam
Differences in Geochemical Signatures and Petrogenesis between the Van Canh and Ben Giang-Que Son Granitic Rocks in the Southern Kontum Massif, Vietnam
Permian Ben Giang-Que Son and Triassic Van Canh granitic rocks are widely distributed across the southern Kontum Massif, the basement of which consists mainly of metasedimentary ro...