- Email: [email protected]
The Fit Between Amazonia, Baltica and Laurentia During the Mesoproterozoic Assemblage of the Supercontinent Rodinia
Gondwana Research, V 5,No. I, p p . 101-107. 02002 International Association for Gondwana Research, Japan. ISSN: 13422-937X
Gondwana Research
The Fit Between Amazonia, Baltica and Laurentia During the Mesoproterozoic Assemblage of the Supercontinent Rodinia Georg R. Sadowski Institute of Geosciences, University of Slib Paulo/CNPq, Brazil, E-mail: [email protected] (Manuscript received April 19,2001; accepted July 2,2001 )
Abstract During the Mesoproterozoic, western Amazonia and southern Baltica both show progressive outgrowth by orogenic accretion to older cratons. Correlation of these orogenic belts indicates that Amazonia and Baltica were joined and evolved together throughout the Mesoproterozoic. Similar correlations also suggest a close relationship of Amazonia with the Labrador part of Laurentia at the same time.
Key words: Amazonia, Baltica, Laurentia, Mesoproterozoic, orogeny.
Introduction Following preliminary suggestions of former authors (Hoffman, 1991; Dalziel, 1992; Dala Salda et al., 1992 etc.), Sadowski (1992a, 1992b) and Sadowski and Bettencourt (1993a, 1993b and 1996) proposed a correlation between the Mesoproterozoicbelts of Amazonia and Laurentia. In the proposed model, the GrenvilleSunsas Belts formed during an accretionary process that
/
0
culminated with the collision of these cratons during the last stage of the Grenvillian-SunsasOrogeny. Meanwhile, Bettencourt et al. (1996) presented paleomagnetic poles for the 1.15 to 0.95 Ga. interval based on 40Ar/39Ar dating, showing a reasonable coincidence with synchronic poles already determined for Laurentia in different publications. hereby, figure 1 shows a relocation of these poles that indicates an equatorial position for both cratons. Since those earlier proposals, new information about the tectonic organization and evolution of Labrador was obtained through current systematic U/Pb dating in Labrador (Gower, 1996) and additional geochemical and geochronologicaldata from the Amazon Craton (Tassinari et al., 1996; Bettencourt et al., 1996). The present article intends to focus with more intensity on the pin-points that mark the intersections of the foldbelts of Southern Baltica and Northern Amazonia.
Common Thermotectonic Events
Fig. 1. Relative positions between Amazonia and Laurentia during Grenvillian times as suggested by rotated paleomagnetic poles from both continents (based on and modified from Bettencourt et al., 1996).
The new information suggests correlations of the Amazon craton (Fig. 2) with Baltica (Fig. 3 ) and Labrador (Sadowski, 1997). Four main common thermotectonic events have been defined and used to subdivide the Amazon craton into chronogeologic Provinces: The Maroni-Itacaiunas (2.2-1.9 Ga), the Rio Negro-Juruena (1.8-1.55 Ga), the Rondonian (1.45-1.3 Ga), and the Sunsas-Apapef (1.25-1 .O Ga) events (Tekeira et ale,1989 and Tassinari, 1996) in Baltica and Labrador these dates
G.R.SADOWSKI
102
BasedModified from Tassinan, 1997
PRECAMBRIAN VOLCANIC SEDIMENTARY COVER
BRASILIANO BELTS
SUNSAS-AGUAPEi 1 0 - 1 25 Ga
correspond roughly to the Svecofennian = Makkovik = Penokean Orogeny (1.9-1.83 Ga), the Gothian = Kongsbergian = Labradorian Orogeny (1.75-1.5 Ga), including the activity of the Transcandinavian Igneous Belt (1.83-1.77 Ga) and the Sveconorwegian Orogeny senso lato (1.34-95 Ga) = Grenvillian sensu lato = Elsonian. The provinces in all three cratons can then be grouped into provinces with the following age spans: 2.2-1.9 Ga: Maroni-Itacaiunas; Lapland-Kola; Nagssugtogidian; Eastern Churchill; Foxe (?).
RONDONIAN-ST YGNACIO 1.3 - 1.5 Ga
Fig. 2. Chronotectonic provinces of Amazonia (based on Tassinari, 1997).
1.9-1.8: Ventuari-Tapajos; Svecofennian; Torngat; Rinkian. 1.8-1.6: Rio Negro-Juruena; Kongsbergian; TIB; Ketilidian; Labradorian. 1.45-1.3: Rondonia-SJgnacio;anorogenic magmatism; Pinwarian. 1.25-1 .O: Sunsas-Aguapei;Sveconorwegian; Grenvillian. Table 1 summarizes these main chronoprovinces of Amazonia, Baltica and Laurentia and shows possible correlations between the main tectonic events during the Middle Proterozoic to Neoproterozoic. Gondwana Research, K 5, No. 1,2002
AMAZONIA-BALTICA-LAURENTIAFIT IN RODINIA
103
Svecofennian 1.8-1.9 Ga SVN 1.27-.9 //// Lapland-Kola / / / /
2.4- 1.9
TIB 1.77-1.83
Kongsberg 1.7 - 1.5
Fig. 3. Chronotectonic provinces of Baltica.
Table 1. Main tectonic events in Amazonia, Baltica and Laurentia. PERIOD (Ga)
AMAZONIA
BALTICA
LAURENTIA
Ca. > 2.4 Ca. 2.2-1.9 1.9-1.8 1.8-1.6 1.45-1.3 1.25-1 .O
Central Amazon Maroni Itacaiunas Ventuari - Tapajo’s Rio Negro - Juruena Rondonia - S. Ignacio Sunsas - Aguapei
Karelides - Kola Lapland - Kola Svecofennian Kongsbergian,TIB Anorogenic Sveconorwegian
Greenland/Superior Nagssugtog., East. Churchill, Foxe? Torngat, Rinkian Ketilidian, Labrador Pinwarian Grenvillian
Geologic Similarities Baltica x Amazonia The proposed link of the northern Amazon craton with Baltica is still debatable but fits the initial reconstruction of Rodinia envisaged by Hofmann (1991) and the geometric fits presented by Dalziel and Gahagan (1994, 1996), and Unrug et al. (1996). Gondwana Research, V. 5, No. 1,2002
In terms of correlation with Baltica, the older Central Amazon Province shows similarities with the Karelides as does the Maroni-Itacaiunas in relation to the Svecofennides. A most striking similarity is the general style of the westward accretionarysequence observed from the Ventuari-Tapajos (VT) towards the Rondonian-Sunsas Belts compared to a similar chronotectonic sequence in Baltica, where an accretionary sequence may be observed
G.R. SADOWSKI
104
-
1.9 1.8 Ga
VENTUARI-TAPAJOS C .A..R.-
CENTRAL-AMAZON PROVINCE
-
1.8 1.6 Ga
RIO NEGRO-JURUENA M A G M A T I C ARCS WA
-
CENTRAL AMAZON PROVINCE 1.65-1.6 1.9 1.7
-
-
1.4 0.9 Ga
AMAZON CRATON
LAURENTIA, AREQUIPA, etc. GRENVILLE / SUNSAS /
I++ +++++ ++++++++<
mafic intrusives metamorphic rocks granite magmatic underplate sediment
rn
arc crust oceanic crust mantle
rzl +++++ +++++
upper mantle cratonic crust
toward the same direction from the Svecofennides (SVF) to the Transcandinavian Igneous Belt (TIB) and the Gothian. Figure 4 is a cartoon trying to establish a first impression of this evolution of the Amazon craton where the VT and
Fig. 4. Diagrams showing tectonic evolution of Amazonian provinces at three different age ranges (partially based on Tassinari, 1997).
RNJB are considered, although with objections similarly to those in Scandinavia (see Gorbatchev and Bogdanova, 1993). There is a proposed chronologically transitional sequence of amalgamated magmatic arcs (Tassinari and Van Schmus, 1992; Tassinari, 1996) whose remnants are Gondwana Research, V. 5, No. 1,2002
AMAZONIA-BALTICA-LAURENTIA FIT IN RODINIA
exposed at different crustal levels. They were accreted to a larger continental mass, probably in an Andean style, along an east-dipping subduction zone. The same evolution is proposed by several authors (e.g., Park, 1995) for the Gothian Belt bordered by the TIB, which affected part of the Svecofennides and crosses the border into the Karelides. Such a detailed discrimination between the corresponding units might still not be possible due to the lack of U-Pb data in the RNJB and the relatively small interval of existence of the Svecofennides in a 1.9-1.83 Ga interval. The Svecofennides still have to be considered as correlatable with the RNJB due to their positiion in relation to the Gothian. They are also accreted island arc and accretionary prisms affected by extensive melts which extend from Central Sweden and Finland southwards to the Tornqvist line into Poland (Windley, 1993)). The eastern limit of the Gothian (GB) bordered by the Transcandinavian Igneous Belt (TIB) has an analog with the general border relationship of the eastern RNJB, both with signs of a common paleosubduction direction dipping to the East. In Scandinavia this has been proposed with the help of geophysical data in Henkel and Erikson (1987) along the originally designated ‘Protogine Shear Zone’. In Brazil the main arguments for this subduction model are isotope geochemistry, dating and petrology, and the Marechal Rondon Shear Zone, which apparentlycomposes the eastern limit of the RNJB (Tassinari and Van Schmus, 1992; Tassinari, 1996). The western border of the Amazon craton is composed of the Sunsas-Rondonianbelts, which might be correlated in broad terms with the Sveconorwegian (sensu lato) subdivided into an early Sveconorwegian phase from 1340 to i250 Ma and a main Sveconorwegian phase from 1100-950 Ma, separated by an Intersveconorwegian extensional period from 1250-1 100 Ma (Starmer, 1993). This scheme corresponds very nearly to the Rondonian and the Sunsas Orogenies in South America, and the Rondonian and the Sunsas Belts could correspond to those of the Gothian region in Baltica (here named according to Gaal and Gorbatchev, 1987). Laurentia x Amazonia Precambrian correlations between Amazonia and Laurentia were detailed in Sadowski and Bettencourt (1996) despite difficulties of interpretation caused by Phanerozoic processes. To the South of the Tucavaca Lineament the extensive Phanerozoic cover and the effects of Brasiliano and later overprints make correlations complicated. Also, Pampean ranges with Grenvillian ages, the intra-Andean Precambrian blocks of the Huancapallac ridge in Peru, and the Medellin or Garzon massifs in ~
Gondwana Research, V. 5, No. 1,2002
105
Colombia may be interpreted as remaining slivers of sheared cratonic borders or accreted exotic terranes (see for example, Dalla Salda et al., 1992; Ramos et al., 1986). Some of the pending questions related to a more rigorous geometric fit between Amazonia, Laurentia and Baltica are: The more contiguous Proterozoic formations located near the borderlines of an eventual lateral fit between Laurentia and the Amazon craton are buried under the sediments of the Chaco or hidden between and below the Andean formations (See Geodynamic Map of the assemblage of the Gondwana Supercontinent, BRGM-SAGS, 1996). Structural features that crosscut the borders of the cratons and could be used as pinpoints similar to those in Baltica vs. Amazonia are absent between Amazonia and Laurentia. They eventually have still to be established in South America and in Laurentia were affected by the Appalachian Orogeny. One of them, for example, mapped in Labrador could be the trend of the Lake Melville and Hawke River Terranes which crosses the usual NE strike of the Grenville Province. Could it have corespondents in South America? (Recently an extensive EW suture has been determined in Rondonia, named the Rio Branco Lineament). In South America the Arequipa massif shows Grenvillian and Transamazonian = Penokean ages (Dalziel, 1996, oral communication). However, as already implied above, the structure of its basement needs to be better known and so are its relations with the Sunsas Belt below the Bolivian Altiplano and Chiquitania regions. South of the Tucavaca Syncline, the Grenvillian age rocks crop out in the Pampean ranges in Argentina and along the Assuncion Arch in Brazil-Paraguay.They may represent a former continuation of the Amazon Craton that split during the late Proterozoic along the Tucavaca lineament. However, lateProterozoic orogens (Brasiliano Orogeny, 0.90-0.55 Ga) represent the Puncoviscana and Paraguaya Belts, and later deformations along the Andean border imprinted the older rocks, turning reconstructions more difficult. A tempting fit of the rocks of the Rockall Plateau and the British Islands next to South America was proposed by Dalziel and Gahagan (1994, 1996) and Park (1995).
The Geometric Fit The positions of Baltica and Amazonia are proposed in figure 5. They could be acceptable mainly if we bear in mind the tolerant rotations admitted for Baltica on the order of 40 to even 90 degrees (Park, 1995; Gaal and
106
G.R.SADOWSKI
Fig. 5. Geometric relationship between Baltica, Laurentia and Amazonia in Grenvillian time.
Gorbatchev, 1987) used by some authors to allow fits with the Rockall Plateau, British Isles or Laurentia.
Conclusions 1. Five chronotectonic provinces of the Amazon craton recently delineated by Tassinari (1996) seem to cross the craton’s border towards the North. They include Maroni-Itacaiunas (approximately PenokeanTransamazonian in age), northern Central Amazon (Paleoproterozoic to Archean), the RNJB and, more westerly, the Rondonian and Sunsas Provinces. They could be correlated with those of Baltica and Laurentia as follows: 2.2-1.9 Ga: Maroni-Itacaiunas, Lapland-Kola, Nagssugtogidian, Eastern Churchill, Foxe (?). 1.9-1.8: Ventuari-Tapajo’s, Svecofennian, Torngat, Rinkian. 1.8-1.6: Rio Negro Juruena, Kongsbergian, TIB, Ketilidian, Labradorian. 1.45-1.3: Rondonia-S. Ignacio, anorogenic magmatism, Pinwarian.
1.25-1 .O: Sunsas-Aguapei, Sveconorwegian, Grenvillian. 2. Some Brasiliano-early Paleozoic ages were determined below the foreland of the Merida and Caribbean Andes (Unrug et al., 1996), and they complicate our interpretation of the presumed extension of the Central Amazon Province to the northern limits of the craton. These newer ages were obtained by means of WAr or Rb/Sr dating of drill core samples and could have been subjected to Phanerozoic thermal overprinting. 3. In terms of correlation with Baltica, the Central Amazon Province shows similarities with the Karelides as do the Ventuari-Tapajos and Maroni-Itacaiunas with the Svecofennides. 4. In the Gothian region the ensialic activity during the Kongsbergian and Sveconorwegian Orogenies (Starmer, 1993), was correlated with the Rondonian and Sunsas Provinces by Sadowski and Bettencourt (1993). Its relationship with the intruded TIB that affected part of the Svecofennidesand older basements is practically identical to that of the Sunsas-Rondonian Provinces with the Rio Negro Juruena. Gondwana Research, V.5, No. 1,2002
Ah4AZONIA-BALTICA-LAUAURENTIA FIT IN RODINIA
5. The possibility of correlating the RN . B with the Gothian and TransScandinavian Belts allows visualization of a major event of juvenile crust accretion which took place not only in this region but in different places of Rodinia, such as the Siberian and West African cratons. 6. The North-South fit of Baltica and Amazonia very probably requires less difficulties than some of the proposed fits of Baltica with Laurentia and may help to better conform Rodinia.
Acknowledgments The author thanks the Brazilian Conselho Nacional de Pesquisas for financial support and Prof. John Rogers for helpful revision and comments for the improvement of the paper.
References Bettencourt, J.S., Onstott, TC., De Jesus, T and Teixeira, W. (1996) Tectonic interpretation of 40Ar/39Arages on country rocks from the central sector of the Rio Negro-Juruena Province, Southwest Amazonian Craton. Int. Geol. Rev., V. 38, pp. 42-56. Dalla Salda, L.H., Cingolani, C. and Varela, R. (1992) Early Paleozoic orogenic belt in the Andes in southwestern South America. Result of Laurentia - Gondwana collision? Geology, V. 20, pp. 616-620. Dalziel, I.W.D. (1992) Antarctica: a tale of two supercontinents. Ann. Rev. Earth Planet. Sci., v. 20, pp. 501-526. Dalziel, I.W.D. and Gahagan, L. (1994) The SWEAT and Laurentian Paleozoic ‘End-Run’hypothesis: a synopsis. EOS supplemment for 1994 meeting of the American Geophysical Union, v. 75, p. 610. Dalziel, I.W.D. and Gahagan, L. (1996) The SWEAT and Laurentian Paleozoic ‘End-Run’hypothesis: a synopsis. A chart with a series of reconstructions presented at the 30th Intern. Geol. Congr. in Beijing, Special Symposium on IGCP Contribution to Supercontinent formation, Symposium K4. Gaal, G. and Gorbatchev, R. (1987) An outline of the Precambrian evolution of the Baltic Shield. Precamb. Res., V. 35, pp. 15-52. Gorbatschev,R. and Bogdanova, S. (1993) Frontiers in the Baltic shield. Precamb. Res., v. 64, pp. 3-21. Gower, C.E (1996) The evolution of the Grenville Province in eastern Labrador, Canada. In Brewer,T. and Aitken, B.P. (Eds.), Precambrian crustal evolution in the North Atlantic region, Geol. SOC.Spl. Publ., 112, pp. 197-218. Henkel, H. and Eriksson, L. (1987) Regional aeromagnetic and gravity studies in Scandinavia. Precamb. Res., v. 35, pp. 169-180. Hofmann, P.E (1991) Did the breakout of Laurentia turn Gondwanaland inside-out? Science, v. 252, pp. 1409-1412. Park, R.G. (1995) Palaeoproterozoic Laurentia-Baltica
Gondwana Research, V. 5, No. 1,2002
107
relationships: a view from the Lewisian. In: Coward, M.P. and Ries, A.C. (Eds.), Early Precambrian processes. Geol. SOC.Spl. Publ., 95, pp. 211-224. Ramos, V.A., Jordan, TE., Allmendinger, R.W., Mpodozis, C., Kay, S.M., CortCs, J.M. and Palma, M.A. (1986) Paleozoic terranes of Central Argentine-Chilean Andes. Tectonics, V. 5, pp. 855-880. Sadowski, G.R. (1992a) An essay of correlation between Amazonia and Grenvillia. (Oral Communication) Penrose Conference on late Precambrian tectonics and the dawn of the Phanerozoic. Death Valley, California. October 1992. Sadowski, G.R. (1992b) Novas perspectivas da Geodinhmica do Gondwana no Proterozoico Superior e MCdio - contribuiqiio do IGCP 288. Abstract (in Portuguese). 37thBrazilian Geological Congr., v. 1, p. 323. Sadowski, G.R. (1997) The fit between Amazonia, Baltica and Laurentia during the Neoproterozoic assemblage of the Supercontinent Gondwana. EUG-9, European Union of Geosciences, (Abst.), p. 168. Sadowski, G.R. and Bettencourt, J.S. (1993a) The GrenvilleAmazon connection in the frame of the SWEAT reconstruction. Geol. SOC.Amer. Abstracts with Programs, V. 3, pp. 76-77. Sadowski, G.R. and Bettencourt, J.S. (1993b) The GrenvilleAmazon link in the frame of the SWEAT reconstruction. Ext. Abstracts of the Intern. Symposium on the Physics and Chemistry of the upper mantle, August 1994, Sao Paulo, Brazil, pp. 103-107 Sadowski, G.R. and Bettencourt, J.S. (1996) Mesoproterozoic tectonic correlations between east Laurentia and the western border of the Amazon craton. Precamb. Res., v. 76, pp. 213-227. Starmer, I.C. (1993) The Sveconorwegian orogeny in Southern Norway, relative to deep crustal structures and events in the North Atlantic Proterozoic Supercontinent. Norsk Geologisk Tidsskrift, v. 73, pp. 109-132. Tassinari, C.G. (1996) Compartimentaqiio GeocronoMgica do Craton Amazonico. (Geochronological subdivision of the Amazonaian Craton)- In Portuguese. Free Lecturer Thesis. Inst. of Geosciences, Univ. of Siio Paulo, Brazil. Tassinari, C.G. and Van Schmus, R. (1992) Oral communication on the geochronological evolution of the Rio Negro Juruena Province, Amazon Craton (held in Brazil). Tassinari, C.G., Nutman, A.P., Van Schmus, W.R., Bettencourt, J.S. and Taylor, P.N. (1996) Geochronological systematics on basement rocks from the Rio Negro-Juruena Province (Amazonian Craton) and tectonic implications. Int. Geol. Rev., v. 38, pp. 161-175. Teixeira, W., Tassinari, C.G., Cordani, U.G. and Kawashita, K. (1989) A review of the geochronology of the Amazonian Craton: tectonic implications. Precamb. Res., v. 42, pp. 213-227. Unrug, R., Sadowski, G.R., Powell, C.McA., Gresse, P., Tack, L., Castaing, C. and Feybesse, J.L. (Eds.), 1996 Geodynamic map of the assemblage of the Gondwana supercontinent. Scale: 1 : l O 000 000, BRGM/SAGS. 4 sheets. Windley, B.E (1993) Uniformitarianism: today plate tectonics is the key to the past. J. Geol. SOC.London, v. 150, pp. 7- 9.
Gondwana Research
The Fit Between Amazonia, Baltica and Laurentia During the Mesoproterozoic Assemblage of the Supercontinent Rodinia Georg R. Sadowski Institute of Geosciences, University of Slib Paulo/CNPq, Brazil, E-mail: [email protected] (Manuscript received April 19,2001; accepted July 2,2001 )
Abstract During the Mesoproterozoic, western Amazonia and southern Baltica both show progressive outgrowth by orogenic accretion to older cratons. Correlation of these orogenic belts indicates that Amazonia and Baltica were joined and evolved together throughout the Mesoproterozoic. Similar correlations also suggest a close relationship of Amazonia with the Labrador part of Laurentia at the same time.
Key words: Amazonia, Baltica, Laurentia, Mesoproterozoic, orogeny.
Introduction Following preliminary suggestions of former authors (Hoffman, 1991; Dalziel, 1992; Dala Salda et al., 1992 etc.), Sadowski (1992a, 1992b) and Sadowski and Bettencourt (1993a, 1993b and 1996) proposed a correlation between the Mesoproterozoicbelts of Amazonia and Laurentia. In the proposed model, the GrenvilleSunsas Belts formed during an accretionary process that
/
0
culminated with the collision of these cratons during the last stage of the Grenvillian-SunsasOrogeny. Meanwhile, Bettencourt et al. (1996) presented paleomagnetic poles for the 1.15 to 0.95 Ga. interval based on 40Ar/39Ar dating, showing a reasonable coincidence with synchronic poles already determined for Laurentia in different publications. hereby, figure 1 shows a relocation of these poles that indicates an equatorial position for both cratons. Since those earlier proposals, new information about the tectonic organization and evolution of Labrador was obtained through current systematic U/Pb dating in Labrador (Gower, 1996) and additional geochemical and geochronologicaldata from the Amazon Craton (Tassinari et al., 1996; Bettencourt et al., 1996). The present article intends to focus with more intensity on the pin-points that mark the intersections of the foldbelts of Southern Baltica and Northern Amazonia.
Common Thermotectonic Events
Fig. 1. Relative positions between Amazonia and Laurentia during Grenvillian times as suggested by rotated paleomagnetic poles from both continents (based on and modified from Bettencourt et al., 1996).
The new information suggests correlations of the Amazon craton (Fig. 2) with Baltica (Fig. 3 ) and Labrador (Sadowski, 1997). Four main common thermotectonic events have been defined and used to subdivide the Amazon craton into chronogeologic Provinces: The Maroni-Itacaiunas (2.2-1.9 Ga), the Rio Negro-Juruena (1.8-1.55 Ga), the Rondonian (1.45-1.3 Ga), and the Sunsas-Apapef (1.25-1 .O Ga) events (Tekeira et ale,1989 and Tassinari, 1996) in Baltica and Labrador these dates
G.R.SADOWSKI
102
BasedModified from Tassinan, 1997
PRECAMBRIAN VOLCANIC SEDIMENTARY COVER
BRASILIANO BELTS
SUNSAS-AGUAPEi 1 0 - 1 25 Ga
correspond roughly to the Svecofennian = Makkovik = Penokean Orogeny (1.9-1.83 Ga), the Gothian = Kongsbergian = Labradorian Orogeny (1.75-1.5 Ga), including the activity of the Transcandinavian Igneous Belt (1.83-1.77 Ga) and the Sveconorwegian Orogeny senso lato (1.34-95 Ga) = Grenvillian sensu lato = Elsonian. The provinces in all three cratons can then be grouped into provinces with the following age spans: 2.2-1.9 Ga: Maroni-Itacaiunas; Lapland-Kola; Nagssugtogidian; Eastern Churchill; Foxe (?).
RONDONIAN-ST YGNACIO 1.3 - 1.5 Ga
Fig. 2. Chronotectonic provinces of Amazonia (based on Tassinari, 1997).
1.9-1.8: Ventuari-Tapajos; Svecofennian; Torngat; Rinkian. 1.8-1.6: Rio Negro-Juruena; Kongsbergian; TIB; Ketilidian; Labradorian. 1.45-1.3: Rondonia-SJgnacio;anorogenic magmatism; Pinwarian. 1.25-1 .O: Sunsas-Aguapei;Sveconorwegian; Grenvillian. Table 1 summarizes these main chronoprovinces of Amazonia, Baltica and Laurentia and shows possible correlations between the main tectonic events during the Middle Proterozoic to Neoproterozoic. Gondwana Research, K 5, No. 1,2002
AMAZONIA-BALTICA-LAURENTIAFIT IN RODINIA
103
Svecofennian 1.8-1.9 Ga SVN 1.27-.9 //// Lapland-Kola / / / /
2.4- 1.9
TIB 1.77-1.83
Kongsberg 1.7 - 1.5
Fig. 3. Chronotectonic provinces of Baltica.
Table 1. Main tectonic events in Amazonia, Baltica and Laurentia. PERIOD (Ga)
AMAZONIA
BALTICA
LAURENTIA
Ca. > 2.4 Ca. 2.2-1.9 1.9-1.8 1.8-1.6 1.45-1.3 1.25-1 .O
Central Amazon Maroni Itacaiunas Ventuari - Tapajo’s Rio Negro - Juruena Rondonia - S. Ignacio Sunsas - Aguapei
Karelides - Kola Lapland - Kola Svecofennian Kongsbergian,TIB Anorogenic Sveconorwegian
Greenland/Superior Nagssugtog., East. Churchill, Foxe? Torngat, Rinkian Ketilidian, Labrador Pinwarian Grenvillian
Geologic Similarities Baltica x Amazonia The proposed link of the northern Amazon craton with Baltica is still debatable but fits the initial reconstruction of Rodinia envisaged by Hofmann (1991) and the geometric fits presented by Dalziel and Gahagan (1994, 1996), and Unrug et al. (1996). Gondwana Research, V. 5, No. 1,2002
In terms of correlation with Baltica, the older Central Amazon Province shows similarities with the Karelides as does the Maroni-Itacaiunas in relation to the Svecofennides. A most striking similarity is the general style of the westward accretionarysequence observed from the Ventuari-Tapajos (VT) towards the Rondonian-Sunsas Belts compared to a similar chronotectonic sequence in Baltica, where an accretionary sequence may be observed
G.R. SADOWSKI
104
-
1.9 1.8 Ga
VENTUARI-TAPAJOS C .A..R.-
CENTRAL-AMAZON PROVINCE
-
1.8 1.6 Ga
RIO NEGRO-JURUENA M A G M A T I C ARCS WA
-
CENTRAL AMAZON PROVINCE 1.65-1.6 1.9 1.7
-
-
1.4 0.9 Ga
AMAZON CRATON
LAURENTIA, AREQUIPA, etc. GRENVILLE / SUNSAS /
I++ +++++ ++++++++<
mafic intrusives metamorphic rocks granite magmatic underplate sediment
rn
arc crust oceanic crust mantle
rzl +++++ +++++
upper mantle cratonic crust
toward the same direction from the Svecofennides (SVF) to the Transcandinavian Igneous Belt (TIB) and the Gothian. Figure 4 is a cartoon trying to establish a first impression of this evolution of the Amazon craton where the VT and
Fig. 4. Diagrams showing tectonic evolution of Amazonian provinces at three different age ranges (partially based on Tassinari, 1997).
RNJB are considered, although with objections similarly to those in Scandinavia (see Gorbatchev and Bogdanova, 1993). There is a proposed chronologically transitional sequence of amalgamated magmatic arcs (Tassinari and Van Schmus, 1992; Tassinari, 1996) whose remnants are Gondwana Research, V. 5, No. 1,2002
AMAZONIA-BALTICA-LAURENTIA FIT IN RODINIA
exposed at different crustal levels. They were accreted to a larger continental mass, probably in an Andean style, along an east-dipping subduction zone. The same evolution is proposed by several authors (e.g., Park, 1995) for the Gothian Belt bordered by the TIB, which affected part of the Svecofennides and crosses the border into the Karelides. Such a detailed discrimination between the corresponding units might still not be possible due to the lack of U-Pb data in the RNJB and the relatively small interval of existence of the Svecofennides in a 1.9-1.83 Ga interval. The Svecofennides still have to be considered as correlatable with the RNJB due to their positiion in relation to the Gothian. They are also accreted island arc and accretionary prisms affected by extensive melts which extend from Central Sweden and Finland southwards to the Tornqvist line into Poland (Windley, 1993)). The eastern limit of the Gothian (GB) bordered by the Transcandinavian Igneous Belt (TIB) has an analog with the general border relationship of the eastern RNJB, both with signs of a common paleosubduction direction dipping to the East. In Scandinavia this has been proposed with the help of geophysical data in Henkel and Erikson (1987) along the originally designated ‘Protogine Shear Zone’. In Brazil the main arguments for this subduction model are isotope geochemistry, dating and petrology, and the Marechal Rondon Shear Zone, which apparentlycomposes the eastern limit of the RNJB (Tassinari and Van Schmus, 1992; Tassinari, 1996). The western border of the Amazon craton is composed of the Sunsas-Rondonianbelts, which might be correlated in broad terms with the Sveconorwegian (sensu lato) subdivided into an early Sveconorwegian phase from 1340 to i250 Ma and a main Sveconorwegian phase from 1100-950 Ma, separated by an Intersveconorwegian extensional period from 1250-1 100 Ma (Starmer, 1993). This scheme corresponds very nearly to the Rondonian and the Sunsas Orogenies in South America, and the Rondonian and the Sunsas Belts could correspond to those of the Gothian region in Baltica (here named according to Gaal and Gorbatchev, 1987). Laurentia x Amazonia Precambrian correlations between Amazonia and Laurentia were detailed in Sadowski and Bettencourt (1996) despite difficulties of interpretation caused by Phanerozoic processes. To the South of the Tucavaca Lineament the extensive Phanerozoic cover and the effects of Brasiliano and later overprints make correlations complicated. Also, Pampean ranges with Grenvillian ages, the intra-Andean Precambrian blocks of the Huancapallac ridge in Peru, and the Medellin or Garzon massifs in ~
Gondwana Research, V. 5, No. 1,2002
105
Colombia may be interpreted as remaining slivers of sheared cratonic borders or accreted exotic terranes (see for example, Dalla Salda et al., 1992; Ramos et al., 1986). Some of the pending questions related to a more rigorous geometric fit between Amazonia, Laurentia and Baltica are: The more contiguous Proterozoic formations located near the borderlines of an eventual lateral fit between Laurentia and the Amazon craton are buried under the sediments of the Chaco or hidden between and below the Andean formations (See Geodynamic Map of the assemblage of the Gondwana Supercontinent, BRGM-SAGS, 1996). Structural features that crosscut the borders of the cratons and could be used as pinpoints similar to those in Baltica vs. Amazonia are absent between Amazonia and Laurentia. They eventually have still to be established in South America and in Laurentia were affected by the Appalachian Orogeny. One of them, for example, mapped in Labrador could be the trend of the Lake Melville and Hawke River Terranes which crosses the usual NE strike of the Grenville Province. Could it have corespondents in South America? (Recently an extensive EW suture has been determined in Rondonia, named the Rio Branco Lineament). In South America the Arequipa massif shows Grenvillian and Transamazonian = Penokean ages (Dalziel, 1996, oral communication). However, as already implied above, the structure of its basement needs to be better known and so are its relations with the Sunsas Belt below the Bolivian Altiplano and Chiquitania regions. South of the Tucavaca Syncline, the Grenvillian age rocks crop out in the Pampean ranges in Argentina and along the Assuncion Arch in Brazil-Paraguay.They may represent a former continuation of the Amazon Craton that split during the late Proterozoic along the Tucavaca lineament. However, lateProterozoic orogens (Brasiliano Orogeny, 0.90-0.55 Ga) represent the Puncoviscana and Paraguaya Belts, and later deformations along the Andean border imprinted the older rocks, turning reconstructions more difficult. A tempting fit of the rocks of the Rockall Plateau and the British Islands next to South America was proposed by Dalziel and Gahagan (1994, 1996) and Park (1995).
The Geometric Fit The positions of Baltica and Amazonia are proposed in figure 5. They could be acceptable mainly if we bear in mind the tolerant rotations admitted for Baltica on the order of 40 to even 90 degrees (Park, 1995; Gaal and
106
G.R.SADOWSKI
Fig. 5. Geometric relationship between Baltica, Laurentia and Amazonia in Grenvillian time.
Gorbatchev, 1987) used by some authors to allow fits with the Rockall Plateau, British Isles or Laurentia.
Conclusions 1. Five chronotectonic provinces of the Amazon craton recently delineated by Tassinari (1996) seem to cross the craton’s border towards the North. They include Maroni-Itacaiunas (approximately PenokeanTransamazonian in age), northern Central Amazon (Paleoproterozoic to Archean), the RNJB and, more westerly, the Rondonian and Sunsas Provinces. They could be correlated with those of Baltica and Laurentia as follows: 2.2-1.9 Ga: Maroni-Itacaiunas, Lapland-Kola, Nagssugtogidian, Eastern Churchill, Foxe (?). 1.9-1.8: Ventuari-Tapajo’s, Svecofennian, Torngat, Rinkian. 1.8-1.6: Rio Negro Juruena, Kongsbergian, TIB, Ketilidian, Labradorian. 1.45-1.3: Rondonia-S. Ignacio, anorogenic magmatism, Pinwarian.
1.25-1 .O: Sunsas-Aguapei, Sveconorwegian, Grenvillian. 2. Some Brasiliano-early Paleozoic ages were determined below the foreland of the Merida and Caribbean Andes (Unrug et al., 1996), and they complicate our interpretation of the presumed extension of the Central Amazon Province to the northern limits of the craton. These newer ages were obtained by means of WAr or Rb/Sr dating of drill core samples and could have been subjected to Phanerozoic thermal overprinting. 3. In terms of correlation with Baltica, the Central Amazon Province shows similarities with the Karelides as do the Ventuari-Tapajos and Maroni-Itacaiunas with the Svecofennides. 4. In the Gothian region the ensialic activity during the Kongsbergian and Sveconorwegian Orogenies (Starmer, 1993), was correlated with the Rondonian and Sunsas Provinces by Sadowski and Bettencourt (1993). Its relationship with the intruded TIB that affected part of the Svecofennidesand older basements is practically identical to that of the Sunsas-Rondonian Provinces with the Rio Negro Juruena. Gondwana Research, V.5, No. 1,2002
Ah4AZONIA-BALTICA-LAUAURENTIA FIT IN RODINIA
5. The possibility of correlating the RN . B with the Gothian and TransScandinavian Belts allows visualization of a major event of juvenile crust accretion which took place not only in this region but in different places of Rodinia, such as the Siberian and West African cratons. 6. The North-South fit of Baltica and Amazonia very probably requires less difficulties than some of the proposed fits of Baltica with Laurentia and may help to better conform Rodinia.
Acknowledgments The author thanks the Brazilian Conselho Nacional de Pesquisas for financial support and Prof. John Rogers for helpful revision and comments for the improvement of the paper.
References Bettencourt, J.S., Onstott, TC., De Jesus, T and Teixeira, W. (1996) Tectonic interpretation of 40Ar/39Arages on country rocks from the central sector of the Rio Negro-Juruena Province, Southwest Amazonian Craton. Int. Geol. Rev., V. 38, pp. 42-56. Dalla Salda, L.H., Cingolani, C. and Varela, R. (1992) Early Paleozoic orogenic belt in the Andes in southwestern South America. Result of Laurentia - Gondwana collision? Geology, V. 20, pp. 616-620. Dalziel, I.W.D. (1992) Antarctica: a tale of two supercontinents. Ann. Rev. Earth Planet. Sci., v. 20, pp. 501-526. Dalziel, I.W.D. and Gahagan, L. (1994) The SWEAT and Laurentian Paleozoic ‘End-Run’hypothesis: a synopsis. EOS supplemment for 1994 meeting of the American Geophysical Union, v. 75, p. 610. Dalziel, I.W.D. and Gahagan, L. (1996) The SWEAT and Laurentian Paleozoic ‘End-Run’hypothesis: a synopsis. A chart with a series of reconstructions presented at the 30th Intern. Geol. Congr. in Beijing, Special Symposium on IGCP Contribution to Supercontinent formation, Symposium K4. Gaal, G. and Gorbatchev, R. (1987) An outline of the Precambrian evolution of the Baltic Shield. Precamb. Res., V. 35, pp. 15-52. Gorbatschev,R. and Bogdanova, S. (1993) Frontiers in the Baltic shield. Precamb. Res., v. 64, pp. 3-21. Gower, C.E (1996) The evolution of the Grenville Province in eastern Labrador, Canada. In Brewer,T. and Aitken, B.P. (Eds.), Precambrian crustal evolution in the North Atlantic region, Geol. SOC.Spl. Publ., 112, pp. 197-218. Henkel, H. and Eriksson, L. (1987) Regional aeromagnetic and gravity studies in Scandinavia. Precamb. Res., v. 35, pp. 169-180. Hofmann, P.E (1991) Did the breakout of Laurentia turn Gondwanaland inside-out? Science, v. 252, pp. 1409-1412. Park, R.G. (1995) Palaeoproterozoic Laurentia-Baltica
Gondwana Research, V. 5, No. 1,2002
107
relationships: a view from the Lewisian. In: Coward, M.P. and Ries, A.C. (Eds.), Early Precambrian processes. Geol. SOC.Spl. Publ., 95, pp. 211-224. Ramos, V.A., Jordan, TE., Allmendinger, R.W., Mpodozis, C., Kay, S.M., CortCs, J.M. and Palma, M.A. (1986) Paleozoic terranes of Central Argentine-Chilean Andes. Tectonics, V. 5, pp. 855-880. Sadowski, G.R. (1992a) An essay of correlation between Amazonia and Grenvillia. (Oral Communication) Penrose Conference on late Precambrian tectonics and the dawn of the Phanerozoic. Death Valley, California. October 1992. Sadowski, G.R. (1992b) Novas perspectivas da Geodinhmica do Gondwana no Proterozoico Superior e MCdio - contribuiqiio do IGCP 288. Abstract (in Portuguese). 37thBrazilian Geological Congr., v. 1, p. 323. Sadowski, G.R. (1997) The fit between Amazonia, Baltica and Laurentia during the Neoproterozoic assemblage of the Supercontinent Gondwana. EUG-9, European Union of Geosciences, (Abst.), p. 168. Sadowski, G.R. and Bettencourt, J.S. (1993a) The GrenvilleAmazon connection in the frame of the SWEAT reconstruction. Geol. SOC.Amer. Abstracts with Programs, V. 3, pp. 76-77. Sadowski, G.R. and Bettencourt, J.S. (1993b) The GrenvilleAmazon link in the frame of the SWEAT reconstruction. Ext. Abstracts of the Intern. Symposium on the Physics and Chemistry of the upper mantle, August 1994, Sao Paulo, Brazil, pp. 103-107 Sadowski, G.R. and Bettencourt, J.S. (1996) Mesoproterozoic tectonic correlations between east Laurentia and the western border of the Amazon craton. Precamb. Res., v. 76, pp. 213-227. Starmer, I.C. (1993) The Sveconorwegian orogeny in Southern Norway, relative to deep crustal structures and events in the North Atlantic Proterozoic Supercontinent. Norsk Geologisk Tidsskrift, v. 73, pp. 109-132. Tassinari, C.G. (1996) Compartimentaqiio GeocronoMgica do Craton Amazonico. (Geochronological subdivision of the Amazonaian Craton)- In Portuguese. Free Lecturer Thesis. Inst. of Geosciences, Univ. of Siio Paulo, Brazil. Tassinari, C.G. and Van Schmus, R. (1992) Oral communication on the geochronological evolution of the Rio Negro Juruena Province, Amazon Craton (held in Brazil). Tassinari, C.G., Nutman, A.P., Van Schmus, W.R., Bettencourt, J.S. and Taylor, P.N. (1996) Geochronological systematics on basement rocks from the Rio Negro-Juruena Province (Amazonian Craton) and tectonic implications. Int. Geol. Rev., v. 38, pp. 161-175. Teixeira, W., Tassinari, C.G., Cordani, U.G. and Kawashita, K. (1989) A review of the geochronology of the Amazonian Craton: tectonic implications. Precamb. Res., v. 42, pp. 213-227. Unrug, R., Sadowski, G.R., Powell, C.McA., Gresse, P., Tack, L., Castaing, C. and Feybesse, J.L. (Eds.), 1996 Geodynamic map of the assemblage of the Gondwana supercontinent. Scale: 1 : l O 000 000, BRGM/SAGS. 4 sheets. Windley, B.E (1993) Uniformitarianism: today plate tectonics is the key to the past. J. Geol. SOC.London, v. 150, pp. 7- 9.