The Guaviare Complex: new evidence of Mesoproterozoic (ca. 1.3 Ga) crust in the Colombian Amazonian Craton
Carolina Amaya-LópezJorge Julián RestrepoMarion WeberFederico Alberto Cuadros JiménezNilson Francisquini BotelhoMauricio Ibáñez-MejíaMario Maya SánchezOrlando Manuel Pérez ParraCarlos A. Ramírez-Cárdenas
8
Citation
32
Reference
10
Related Paper
Citation Trend
Abstract:
The Guaviare Complex is a new unit defined in the Colombian Amazonian Craton, which is part of the Precambrian basement located in southeastern Colombia. It is divided into three units according to their textural and compositional characteristics, termed Termales Gneiss, Unilla Amphibolite, and La Rompida Quartzite. Termales Gneiss rocks are petrographically classified as gneisses and quartz-feldspar granofels, with the local formation of blastomylonite-like dynamic rocks. The Unilla Amphibolite consists of only amphibolites, and La Rompida Quartzite consists of muscovite quartzites, quartz-feldspar granofels, and quartz-muscovite schists. The protoliths of Termales Gneiss and Unilla Amphibolite were formed in the Mesoproterozoic at 1.3 Ga due to bimodal magmatism (felsic and mafic) derived from mantle material, with some crust contamination that was probably related to the formation of extensional arcs associated with trans-arc basins in the NW section of the Amazon Craton. La Rompida Quartzite rocks originated from sediments derived from granite rocks and from other, older areas of the craton. These rocks have a maximum age of 1.28 Ga. The low-to-medium grade metamorphism that affected these units occurred from 1.28 to 0.6 Ga, most likely concurrently with the Putumayo orogeny of approximately 1.0 Ga, although it may have been an independent event.Weathering of the earliest continents could have set in motion the formation of cratons, the immutable roots of continents.
Cite
Citations (0)
The La Plata craton of Uruguay consists mostly of Paleoproterozoic terranes that are ideal for the investigation of the Trans-Amazonian Cycle evolution because, unlike the terranes of southeastern Brazil, they are unaffected by the Brasiliano collisional orogenies (640-590 Ma). The U-Pb isotopic dating of zircons from four Uruguayan rocks by the Sensitive High-mass Resolution Ion Micro Probe (SHRIMP II) shows an evolution from 2224 to 2056 Ma. We also extend the discussion of the cycle to the entire South American continent to provide a broad overview of the processes and belts involved. The Trans-Amazonian Cycle of South America consists of four main orogenies, of which three are present in the Uruguayan Piedra Alta (Isla Mala, Paso Severino, and Soca units) and Nico Pérez (Rivera and Valentines samples) terranes. All four Trans-Amazonian Cycle orogenies described in the classical Trans-Amazon orogen of the type-area (São Luís cratonic fragment, Gurupi belt) and in the Amazon craton are present in the La Plata craton. In Uruguay the second (2180-2120 Ma) and the third (2080-2050 Ma) Trans-Amazonian Cycle orogenies are well developed, whereas the oldest orogeny (2260-2200 Ma) is identified by only one inherited zircon (2224 Ma, Valentines granulite) and the fourth orogeny (2020-2010 Ma) has to be detected, but it is present in neighboring southern Brazil (Itapema, Camboriú, and Santa Maria-Chico units). The Rivera meta-trondhjemite was formed at 2140 ± 6 Ma, an epoch of granitoid-greenstone formation along all the Trans-Amazonian Cycle belts of South America, and by the Paso Severino felsic volcanics, formed at 2146 ± 7 Ma. The Rivera trondhjemite was metamorphosed at 2077 ± 6 Ma, a period characterized by intrusion of post-tectonic potassic granitoids and regional high-grade metamorphism. The metamorphism of the Valentines granulite is slightly younger (2058 ± 3 Ma) and this rock contains zircon with several inherited ages, such as 2224, 2163 (second orogeny), 2535, and 2619 Ma. The Soca charnockite is the youngest known Trans-Amazonian Cycle rock in Uruguay (2056 ± 6 Ma) and represents a continent-wide period of emplacement of post-tectonic, evolved granites and charnockites, such as the Calçoene charnockite (2059 Ma) of Amapá, Brazil. The data presented improve our understanding of tectonic processes active in South America during the Rhyacian Trans-Amazonian Cycle. However, the evolution of large segments of Paleoproterozoic crust and the Trans-Amazonian Cycle subdivision remain uncertain in many regions where U-Pb data are scarce or not available. The dating and characterization of these terrains require further investigation.
Orogeny
Rodinia
Geochronology
Laurentia
Cite
Citations (133)
The signs of the collisional structure are expressed in the upper crust by the advanced Priverhoyansk forland and local hinterland basins is separated by a high-speed array, most likely of magmatic origin. The boundary of the craton at an angle of about 15 ° is submerged under the crust of the folded system, where the characteristic layer of the craton lower crust at velocity of 6,7–6,9 km /s is absent and the velocity in a whole crust is reduced, as well as along the Moho from 8,3 to 7,9-8,0 km / s.
Upper crust
Cite
Citations (1)
S1: Radial plot and Age vs. Age plotFigure S1.Radial plot and Age vs. Age plot of AFT single grain ages for sample 171, constructed using QTQt (Gallagher, 2012).The "y" axis on the radial plot is referred in the figure with the label provided by the QTQt software.However, we acknowledge that the "y" axis in a radial plot is given by yj = (zj -z0)/σ(zj ), for 1 ≤ j ≤ n, n equals the number of grains and with zj a transformation of some data and σ(zj) the corresponding measurement uncertainty (Galbraith, 1988).Normally it is referred as a "standardised estimate".
Cite
Citations (0)
The entire Earth was bombarded during the episode that also scarred the Moon, our neighbor in space. Circular Moon-like fracture patterns must have characterized the Earth’s surface in the past, but their survival is generally assumed to be incompatible with the workings of plate tectonics. Yet “low-tech” observations of published maps clearly show continent-sized circular patterns for which no explanation seems available other than as vestiges of the bombardment of ~4100–3850 Ma. South America provides a prime example for when tectonic slivers of Precambrian rocks in the Andes are taken into account, and the younger rocks of the Amazon Basin ignored, the Guyanan and Brazilian Shields together form a nearly perfect circle. The problem is to find an explanation for the observed patterns that is compatible with what is known (not assumed) concerning the workings of plate tectonics. Here it is proposed that sufficiently deep impact-fractures have been regenerated upward from the brittle-ductile boundary throughout four billion years of our planet’s history. Regeneration of deep fractures was assured by outgassing, flow, convection, changes in crystal structure, earthquakes, and the twice-daily earth-tide. This has prevented scars in contact with the underlying ductile material from ever fully healing. These ancient scars thereby established initial conditions for later regional geology. Such scars are regenerated “cold” from below and are fundamentally different from astroblemes, whose rocks were directly subjected to the high temperatures and pressures that accompany hypervelocity impacts. Melt-rock from the impacts themselves, and from decompression melting within excavations, filled the largest impact sites and produced coherent 3-D “craterforms”, with melt-overflow producing platforms. Collisions caused craton rims to buckle, producing orogens. Erosion of smaller-diameter scars exposed impact-fractures entering the Earth at gentle angles along which subduction could occur. Plate tectonics became possible when the deep 3–D scars were eroded to the point where the crust became loose, apparently first occurring following episodes of Snowball Earth. This did not occur on planetary bodies lacking liquid water in the surface domain. Activation of deep fractures from below is a recurring geological phenomenon in both continental and oceanic settings. The LHB provides the framework within which plate tectonics can and does operate.
Cite
Citations (0)