scholarly journals Pb Isotope Signatures of Polymetallic (Au-Cu-Zn) Deposits of the SW Amazonian Craton and Their Relation to Crustal Evolution

Noble Metals ◽  
10.5772/35801 ◽  
2012 ◽  
Author(s):  
Mauro C.
Keyword(s):  
Crustal Evolution ◽  
Pb Isotope ◽  
Amazonian Craton

Insights on the magmatism, crustal evolution and metallogenesis of the Amazonian craton

2009 ◽  
Vol 27 (2-3) ◽  
pp. 109-112
Author(s):  
Roberto Dall’Agnol ◽  
Reinhardt A. Fuck ◽  
Raimundo Netuno Nobre Villas
Keyword(s):  
Crustal Evolution ◽  
Amazonian Craton

scholarly journals Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

2017 ◽  
Vol 47 (2) ◽  
pp. 275-299 ◽  
Author(s):  
Bruna Karine Correa Nogueira ◽  
Paulo Sergio de Sousa Gorayeb ◽  
Elton Luiz Dantas ◽  
Rafael Estumano Leal ◽  
Marco Antonio Galarza
Keyword(s):  
Shear Zones ◽  
Crustal Evolution ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Crust Formation ◽  
Magmatic Arc ◽  
Continental Arc ◽  
Amazonian Craton ◽  
Granitoid Rocks ◽  
Geochemical Studies

ABSTRACT: The São Luís Cráton comprises an area between northeast Pará state and northwest Maranhão that exposes Paleoproterozoic granitic suites and meta-volcanosedimentary sequences. In the east of this geotectonic unit, about 70 km south of São Luís, there is a portion of the São Luís Craton, represented by the intrusive Rosario Suite (RS). This work is focused on rocks of this suite, including petrographic, lithochemical and geochronological studies to understand the crustal evolution of these granitoid rocks. The rock spectrum varies from tonalitic to granodioritic, quartz dioritic and granitic compositions, and there are partial structural and mineralogical changes related to deformation along transcurrent shear zones. The geochemical studies show granitic metaluminous compositions of the calc-alkaline series with I-type affinity typical of magmatic arc. Rare earth elements show marked fractionation and slight Eu positive or negative anomalies (Eu/Eu* = 0.82 to 1.1). Zircon U-Pb data provided consistent ages of 2165 ± 7 Ma, 2170 ± 7 Ma, 2170 ± 7 Ma, 2161 ± 4 Ma and 2175 ± 8 Ma, dating emplacement of these granitoids as Paleoproterozoic (Rhyacian). Sm-Nd isotopic data provided model ages (TDM) of 2.21 to 2.31 Ga with positive values of εNd +1.9 to +3.2 (t = 2.17 Ga), indicating predominantly Rhyacian crustal sources for the parental magmas, similar to those ones found in other areas of the São Luís Craton. The data, integrated with published geological and geochronological information, indicate the occurrence of an important continental crust formation event in this area. The Paleoproterozoic evolution between 2.17 and 2.15 Ga is related to the Transamazonian orogeny. The granitoids of the Rosario Suite represent the main phase of continental arc magmatism that has continuity in other parts of the São Luís Craton and can be correlated with Rhyacian accretionary magmatism in the northwestern portion of the Amazonian Craton that amalgamated Archean terrains during the Transamazonian orogeny.

A reassessment of the timing of early Archaean crustal evolution in West Greenland

1998 ◽  
pp. 88-93 ◽  
Author(s):  
Stephen Moorbath ◽  
Balz Samuel Kamber
Keyword(s):  
Grain Structure ◽  
Crustal Evolution ◽  
Pb Isotope ◽  
West Greenland ◽  
Ion Probe ◽  
Combined Use ◽  
Wide Range ◽  
History Of ◽  
Single Zircon ◽  
Precambrian Terrain

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Moorbath, S., & Kamber, B. S. (1998). A reassessment of the timing of early Archaean crustal evolution in West Greenland. Geology of Greenland Survey Bulletin, 180, 88-93. https://doi.org/10.34194/ggub.v180.5091 _______________ In last year’s Review of Greenland activities, Kalsbeek (1997) divided the recent history of geochronology into three successive periods: 1. single-sample K-Ar and Rb-Sr mineral or whole-rock age determinations; 2. Rb-Sr and Pb/Pb whole-rock isochrons and multigrain zircon U-Pb isotope data; 3. the present, where ‘single’ zircon U-Pb data are predominantly used. To these three, we would propose adding a fourth, namely a combination of all three, in order to achieve the maximum age information within complex terrains. For an early Precambrian terrain like that of West Greenland, we consider that the combined use of at least the last two approaches is essential (to which should be added the Sm-Nd method). In recent years, study of the geochronological evolution of the Godthåbsfjord and Isua regions has been dominated by rapid and precise ion-probe U-Pb dating of complex-structured zircons, and it has become fashionable to regard the wide range of zircon dates, and particularly the oldest, as giving the age of rock formation. Dates obtained from whole-rock Rb-Sr, Sm-Nd and Pb/Pb regressions have been regarded as too imprecise for adequate age resolution, whilst constraints on crustal evolution imposed by initial Sr, Nd and Pb isotope ratios have been summarily dismissed or totally ignored. We consider that this sole dependence on ion-probe dating of zircon can lead (as, indeed, in the early Archaean of West Greenland) to a potential misinterpretation of the timing of crustal evolution, especially in those cases where little or no information regarding the relationship between measured date and internal grain structure is available. Figure 1 shows the localities mentioned in the text.

Labradorian and Grenvillian crustal evolution of the Goose Bay region, Labrador: new U–Pb geochronological constraints

1993 ◽  
Vol 30 (12) ◽  
pp. 2315-2327 ◽  
Author(s):  
S. Philippe ◽  
R. J. Wardle ◽  
U. Schärer
Keyword(s):  
Crustal Evolution ◽  
Calc Alkaline ◽  
Crust Formation ◽  
Pb Isotope ◽  
Grenville Province ◽  
Previous Evidence ◽  
Anorthosite Massif ◽  
Thrust System ◽  
Grenvillian Orogeny ◽  
Geochronological Constraints

Major initial crust formation in the northeastern Grenville Province of Labrador occurred during the Labradorian orogeny (1710–1620 Ma) prior to re-deformation in the Grenvillian orogeny between 1050 and 950 Ma. The Goose Bay region includes several types of juvenile Labradorian crust, including calc-alkaline (arc-related?) terranes and the granite–anorthosite massif of the Mealy Mountains Terrane. New U–Pb dates corroborate previous evidence that calc-alkaline plutonism occurred ca. 1672 Ma and was followed closely by Labradorian metamorphism ca. 1659 Ma. Dates from strongly deformed rocks at the base of the Mealy Mountains Terrane have yielded ca. 1712, 1754, and 1775 Ma maximum upper intercept ages of plutonic and (or) metamorphic origin. These apparent ages represent the oldest component of the Labradorian crust that has been recognized to date and appear to be a distinctive feature of Mealy Mountains Terrane. The initial Pb isotope signature of these rocks, however, precludes the presence of significantly earlier (pre-1.8 Ga) crust.New U–Pb ages also support previous models for episodic Grenvillian metamorphism and indicate metamorphic pulses ca. 1035, 1010, 990, and 970 Ma, which probably represent the metamorphic response to progressive overthrusting by Mealy Mountains Terrane. Overthrusting of this terrane occurred along the Grand Lake thrust system, which is highlighted as a fundamental structure of the eastern Grenville Province and one that may have developed by reactivation of a Labradorian terrane boundary.

scholarly journals Nd AND Pb ISOTOPE STUDIES BEARING ON THE CRUSTAL EVOLUTION OF SOUTHEASTERN BRAZIL

1987 ◽  
Vol 17 (3) ◽  
pp. 263-268 ◽  
Author(s):  
M. S. M. MANTOVANI ◽  
C. J. HAWKESWORTH ◽  
M. A. S. BASEI
Keyword(s):  
Southeastern Brazil ◽  
Crustal Evolution ◽  
Pb Isotope ◽  
Isotope Studies
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