Características isotópicas (Nd e Sr) do plutonismo intrusivo no extremo NW do Cráton Amazônico, Venezuela, e implicações para a evolução paleoproterozóica

Teixeira, Wilson; Tassinari, Colombo Celso Gaeta; Mondin, Mateus

doi:10.5327/s1519-874x2002000100011

Cited by 6 publications

(2 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Samples dated by U-Pb methods in this region, from the studies of Bonilla-Pérez et al (2013), Cordani et al (2016b), andIbañez-Mejia (2014) are mainly from outcrops located around the Orinoco, Inírida, and Atabapo Rivers. From oldest to youngest, the basement in this area is comprised by: (i) Volcanic and intrusive rocks of the Cuchivero magmatic belt (Gibbs, 1987;Teixeira et al, 2002), with crystallization ages ca. 1.99 Ga and thus presumably belonging to a broader magmatic event in the Guiana Shield known as the Orocaima event (Reis et al, 2000), which in NW Venezuela is dominantly comprised by coarse-and fine-grained biotite granitoids (e.g., Figure 5a, 5b); (ii) intermediate and granitic orthogneisses which are widespread along the Atabapo and Ventuari Rivers (e.g., Figure 5c) and yield igneous crystallization ages ca.…”

Section: Geology Of Guainía and Vichada Near The Colombia-venezuela Bmentioning

confidence: 99%

Chapter 4

SGC¹

2019

View full text Add to dashboard Cite

The crystalline basement of eastern Colombia, east of the frontal deformation zone of the north Andean Eastern Cordillera, is comprised by Precambrian igneous, metamorphic, and sedimentary rocks of the western Guiana Shield. Designated in the late seventies with the all-embracing stratigraphic name of 'Mitú Migmatitic Complex', the age, petrology, and tectonic history of the Precambrian basement in eastern Colombia has remained one of the least explored issues in South American geology. This chapter aims to present a brief overview of recent advances made to improve our general understanding of the geology of this wide region, using a compilation of the available U-Pb, Sm-Nd, Lu-Hf, and δ 18 O isotopic data obtained using modern methods. Using all the available U-Pb geochronologic data we show that, in general: (i) The Precambrian basement of the western Guiana Shield exhibits magmatic crystallization ages in the range from ca. 1.99 to ca. 1.38 Ga, and (ii) that four broad periods of magmatic activity, two in the mid-to late-Paleoproterozoic (ca. 1.99 and ca. 1.81-1.72 Ga), one in the early Mesoproterozoic (ca. 1.59-1.50 Ga), and one in the mid Mesoproterozoic (ca. 1.41-1.39 Ga) dominate the geology of the area. The (whole-rock) Nd and combined (zircon) Hf-O datasets indicate a general lack of 'depleted mantle' like mid-Paleoproterozoic or Mesoproterozoic crust, thus indicating that either the Proterozoic sub-continental mantle in the region was not as radiogenic as global mantle evolution models would suggest, or that reworking of older crust might have played an important role in the geological and geochemical evolution of the western Guiana Shield. Therefore, although the geochronologic results confirm that most of the exposed basement in eastern Colombia can be broadly considered to be of Rio Negro-Juruena-like affinity, this belt exhibits some distinct isotopic characteristics relative to similar age domains exposed south of the Amazon Basin. Furthermore, we note that the geochronologic data obtained to this date has failed to clearly identify an early-to mid-Mesoproterozoic terrane boundary in the Colombian basement, thus opening the possibility that a Rondonian-San Ignacio-like province is not represented in the Guiana Shield. Based on these recent field, geochemical, and geochronological observations, we consider the long and extensively used term 'Mitú Migmatitic Complex' to be now inadequate and obsolete, and argue that the current state of the knowledge of the Colombian Precambrian basement is such that the community should move towards adopting Proterozoic

show abstract

Section: Geology Of Guainía and Vichada Near The Colombia-venezuela Bmentioning

confidence: 99%

Chapter 4

SGC¹

2019

View full text Add to dashboard Cite

show abstract

“…The early stages of cooling and uplift of Imataca granulites may be related to thrusting along the major fault zones. Win et al, 1993 andTeixeira et al, 2002).…”

Section: Geological Settingmentioning

confidence: 99%

The Imataca Complex, NW Amazonian Craton, Venezuela: Crustal evolution and integration of geochronological and petrological cooling histories

Tassinari¹,

Munhá²,

Teixeira³

et al. 2004

Episodes

Self Cite

View full text Add to dashboard Cite

SHRIMP U/Pb-zircon data and Nd mean crustal residence ages indicate that the Imataca Complex developed from an Archean (≥3.2 Ga) continental protolith which has undergone considerable isotopic disturbance plus and juvenile accretion during late-Archean (~ 2.8 Ga) times. Transamazonian granulites experienced peak metamorphic conditions of 750 -800 °C, 6 -8 kbar with associated transpressive thrusting and tectonic imbrication. Geochronology on zircon, pyroxene and garnet constrains the timing of peak metamorphism at 1.98 -2.05 Ga. Diffusion modeling of Fe-Mg exchange between biotite inclusions and host garnet yields (near metamorphic peak) cooling rates of 50 -100 °C/Ma, with petrological cooling rates being generally consistent with cooling rates determined from geochronology. Combining the retrograde P-T path with cooling rates suggests that after the metamorphic peak, large portions of the Imataca Complex were exhumed from 30 to 17 km at a rate of 7 -2 km/Ma. After this, exhumation rates progressively decreased as the rocks approached the surface. Rapid overall uplift/erosion had ceased when the rocks passed below 600 -550 °C at 2.01 -1.96 Ga ago. Observed variations in mineral cooling ages are interpreted as to reflect episodic differential tectonic exhumation within major fault systems. Inferred (maximum) ages of fault re-activation generally coincide with major continental accretion events in the Amazonian Craton and reflect long-term thermal evolution of the Imataca terrane, as conditioned by variable response to continued continental convergence during the Proterozoic. Imataca Complex (Venezuela) provide a time framework for protolith formation and high-grade metamorphism. Petrological investigation of Imataca Complex samples is used to define the main fea-

show abstract

Autochthonous and allochthonous strata of the El Callao greenstone belt: Implications for the nature of the Paleoproterozoic Trans-Amazonian orogeny and the origin of gold-bearing shear zones in the El Callao mining district, Guayana shield, Venezuela

Hildebrand¹

2005

Precambrian Research

View full text Add to dashboard Cite

Características isotópicas (Nd e Sr) do plutonismo intrusivo no extremo NW do Cráton Amazônico, Venezuela, e implicações para a evolução paleoproterozóica

Cited by 6 publications

References 21 publications

Chapter 4

Chapter 4

The Imataca Complex, NW Amazonian Craton, Venezuela: Crustal evolution and integration of geochronological and petrological cooling histories

Autochthonous and allochthonous strata of the El Callao greenstone belt: Implications for the nature of the Paleoproterozoic Trans-Amazonian orogeny and the origin of gold-bearing shear zones in the El Callao mining district, Guayana shield, Venezuela

Contact Info

Product

Resources

About