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The Rondonian-San Ignacio Province in the SW Amazonian Craton: An overview

Jorge Silva Bettencourt a,*, Washington Barbosa Leite Jr. b, Amarildo Salina Ruiz c, Ramiro Matos d,a,Bruno Leonelo Payolla e, Richard M. Tosdal f

a Institute of Geosciences of the University of So Paulo (IGc-USP), So Paulo, Brazilb Institute of Geosciences and Exact Sciences of the So Paulo State University (IGCE-UNESP), Rio Claro, So Paulo, Brazilc Institute of Geosciences, Federal University of Mato Grosso, Cuiab, Brazild Institute of Geologic Investigation and Environment, University Mayor de San Andrs, La Paz, Boliviae

Centrais Eltricas do Norte do Brazil SA Eletronorte, BrazilfMineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC, Canada V6T 1Z2

a r t i c l e i n f o

Article history:Received 5 May 2009Accepted 10 August 2009

Keywords:SW Amazonian CratonRondonian-San Ignacio ProvinceMesoproterozoic evolutionAccretionary belts

Collisional orogeny

a b s t r a c t

The Rondonian-San Ignacio Province (1.561.30 Ga) is a composite orogen created through successiveaccretion of arcs, ocean basin closure and final oblique microcontinentcontinent collision. The effectsof the collision are well preserved mostly in the Paragu Terrane (Bolivia and Mato Grosso regions)and in the Alto Guapor Belt and the Rio Negro-Juruena Province (Rondnia region), considering thatthe province was affected by later collision-related deformation and metamorphism during the SunssOrogeny (1.251.00 Ga). The Rondonian-San Ignacio Province comprises: (1) the Jauru Terrane (1.781.42 Ga) that hosts Paleoproterozoic basement (1.781.72 Ga), and the Cachoeirinha (1.561.52 Ga)and the Santa Helena (1.481.42 Ga) accretionary orogens, both developed in an Andean-type magmaticarc; (2) the Paragu Terrane (1.741.32 Ga) that hosts pre-San Ignacio units (>1640 Ma: Chiquitania

Gneiss Complex, San Ignacio Schist Group and Lomas Manechis Granulitic Complex) and the PensamientoGranitoid Complex (1.371.34 Ga) developed in an Andean-type magmatic arc; (3) the Rio Alegre Terrane(1.511.38 Ga) that includes units generated in a mid-ocean ridge and an intra-oceanic magmatic arcenvironments; and (4) the Alto Guapor Belt (


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zones, and plutonic complexes that reflect the collisional nature ofthe boundary. Conversely, Santos et al. (2000) andSantos et al.(2008), based on UPb and SmNd, separated the rocks of the RSIPinto the Rondnia-Juruena Province (1.841.54 Ga) and SunssProvince (1.461.11 Ga). They proposed that the Sunss Orogen

is characterized by an autochthonous evolution and was formedby four orogenies: Santa Helena (1.461.42 Ga), Candeias (1.371.32 Ga), San Andres (ca. 1.27 Ga) and Nova Brasilndia (1.181.11 Ga).

Currently, the RSIP in the southwestern border of the Amazo-nian Craton is limited to the north and east by the Rio Negro-Juru-ena Province. To the south, the RSIP is bounded by the SunssProvince along the Sunss tectonic front (Rio Negro Front and San-ta Catalina Straight Zone). The western part of the RSIP is coveredby Phanerozoic sedimentary sequences. The total area exposed isat least 2000 km long and 800 km wide. It includes large partsof the Precambrian shield of the Brazilian states of Rondnia andMato Grosso, as well as a large area of the Santa Cruz and Benidepartments in Bolivia. Outcrops of the RSIP in the northwestern

corner of the Amazonian Craton are obscured by Phanerozoic sed-imentary sequences.Despite the substantial new geological mapping, and the addi-

tional collection of geophysical, geochronological and geochemicaldata, very little is known about several segments of the RSIP inRondnia, Mato Grosso and eastern Bolivia regions. This lack ofdata hampers a better correlation of units. Furthermore, definitionof tectonic unit boundaries, age limits, lateral continuation, inter-nal organization, subdivision and varied nomenclature all are con-troversial, nonetheless leading to several competing chronologicframeworks, and terminology for the tectonic events in the RSIP.

We proposed the RSIP is a composite orogen, consisting of anolder complex accretionary orogen (15561430 Ma) followed by,the terminal microcontinent-continent collision at 13401320Ma. The major tectonic units are: the Paragu Terrane, Jauru Ter-rane, Rio Alegre Terrane and the Alto Guapor Belt (Fig. 1). We fur-thermore expand the upper age of RSIP to 1.56 Ga in order toinclude the Cachoeirinha Orogen (1.561.52 Ma). The overall timeinterval for RSIP is thus considered herein to 1.561.30 Ga.

We review the presently accepted evolutionary history of theRSIP, including the temporal and spatial distribution, precursors,and tectonic settings. Included are descriptions of the terranesand orogens, and their tectonic limits. These data provide the basisfor an overall interpretation and related tectonic model. Post-Ron-donian-San Ignacio events (Sunss Orogeny) that affected the RSIPare described byTeixeira et al. (2010).

2. The RSIP in the context of the SW Amazonian Craton

Several recent reviews of the Amazonian Craton (Tassinari andMacambira, 1999; Santos et al., 2000; Tassinari et al., 2000; Corda-ni and Teixeira, 2007; Cordani et al., 2009) have focused on the cor-relation of major geologic units and structures. These reviews aresubstantially enhanced by regional scale work based on UPb TIMSand SHRIMP geochronology, SmNd geochemistry, as well as PbPb evaporation techniques.

The SW portion of the Amazonian Craton is represented by fourProterozoic sub-parallel provinces (Cordani and Teixeira, 2007;Cordani et al., 2009): Ventuari-Tapajs (2.001.80 Ga), Rio Negro-Juruena (1.781.55 Ga), Rondonian-San Ignacio (1.501.30 Ga)and Sunss-Aguape (1.251.00 Ga) (Fig. 1). In this context, for Cor-dani and Teixeira (2007), the RSIP may be interpreted to represent

collisional orogeny involving a possible microcontinent combinedwith domains composed of the Rio Crespo Intrusive Suite(1.50 Ga), Rio Alegre Complex (1.511.48 Ga), Santa Helena batho-lith (1.451.42 Ga), Colorado Metamorphic Suite (1.361.30 Ga)

and the Pensamiento Granitoid Complex (1.361.30 Ga). High-grade metamorphic rocks related to the San Ignacio Orogeny(1.35 Ga) and late- to post-tectonic plutonism: Santo Antnio(1.41 Ga), Teotnio (1.39 Ga), Alto Candeias (1.34 Ga) and SoLoureno-Caripunas intrusive suites are also evident. RSIP craton-

ization is interpreted to have occurred at 1.30 Ga (ArAr ages)and 1.25 Ga (KAr ages).Cratonization of the RSIP was followed by tectonic reactivation,

deformation, thermal overprint, and magmatism related to theSunss Orogeny. These effects are manifested by extensive shearzones (e.g. Ji-Paran Shear Zone, Scandolara et al., 1999; Tohveret al., 2005), mylonitic belts, rifts and sedimentary basins, andpost-tectonic and anorogenic intrusions (Cordani and Teixeira,2007; Cordani et al., 2009; Teixeira et al., 2010).

3. The Rondonian-San Ignacio Province

3.1. The Paragu Terrane (1.821.32 Ga)

Theterm Paragu Craton was introduced by Litherland et al.(1986)in eastern Bolivia Precambrian shield to denote a tectoni-cally stable region during the Meso- to Neoproterozoic deforma-tion of the Sunss and Aguape belts. However, Saes and FragosoCesar (1996)subdivided the shield into two terranes, the ParaguTerrane and the San Pablo Terrane, and Tohver et al. (2004)ex-panded the limits of the craton to include a large area of the MatoGrosso, and proposed that the EW trending Nova Brasilndia belt(ca. 2000 km in extent) marks the limit between the Amazonianand Paragu cratons, during the late Mesoproterozoic. In this pa-per, we adopt the term Paragu Terrane to denote a composite ter-rane, which comprises Paleoproterozoic basement rocks(Chiquitania Gneissic Complex, San Ignacio Schist Group, LomasManechis Granulitic Complex) and Mesoproterozoic granitoids

(Pensamiento Granitoid Complex), amalgamated to the proto-Amazonian Craton during the Rondonian-San Ignacio Orogeny. Tothe east a ductile shear zone marks the limit with Rio Alegre Ter-rane. To the north the limit with the Alto Guapor Belt is hiddenby Cenozoic sedimentary sequences. To the south the boundaryis hidden by Brasiliano platform sediments (post-Sunss units),and to the west by Cenozoic sedimentary sequences (Fig. 1).

3.1.1. Pre-San Ignacio basement rocks (>1640 Ma)The pre-San Ignacio crust, based on RbSr whole-rock ages was

considered older than 1961 Ma (Litherland et al., 1986). Boger et al.(2005) refined the understanding of these rocks doing precise UPbSHRIMP zircon ages from two high-metamorphic grade rocks ofthe Lomas Manechis Granulitic Complex (LMGC), predominantly

composed of granites, orthopyroxene bearing granitoids and pink-ish granitoids that yielded UPb SHRIMP zircon crystallization agesof 1689 5 and 1663 4 Ma, and from two high-grade paragneis-ses from the Chiquitania Gneissic Complex (CGC), represented bybiotite-bearing felsic gneisses, and interpreted to be of sedimen-tary or volcanic origin (detrital zircons).Boger et al. (2005)inter-preted the Chiquitania paragneiss protolith to have been derivedfrom a predominantly Paleoproterozoic source formed at about1765 Ma, whereas the paragneiss protolith was deposited after atca. 1690 Ma (Fig. 2,Table 1).

Additional UPb SHRIMP zircon ages from the Lomas Manechisgranulitic gneiss, Rio Fortuna orthogneiss, Santa Rita orthogneiss,and Refugio Granite are reported by Santos et al. (2008). The LomasManechis granulitic gneiss contains magmatic zircons with

207Pb/206Pb age of 1818 13 Ma; these zircons are the oldest yetidentified in Bolivia. The Rio Fortuna and Santa Rita orthogneissshow inherited zircon grains formed between 1772 and 1729 Ma.The Refugio Granite has a 207Pb/206Pb crystallization age of

J.S. Bettencourt et al. / Journal of South American Earth Sciences 29 (2010) 2846 29
https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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Fig. 1. (A)Simplified map of theSW Amazonian Cratonshowingthe approximateboundaries of the main provinces, majororogens, terranes andbelts, tectonic elements, andlithologic units. (B) Major geochronological provinces of the Amazonian Craton (after Cordani and Teixeira, 2007). MI, Maroni- Itacaiunas Province; VT, Ventuari-TapajsProvince; RNJ, Rio Negro-Juruena Province; RO, Rondonian-San Ignacio Province; SS, Suns-Aguape Province. Locations ofFigs. 24are shown.

30 J.S. Bettencourt et al. / Journal of South American Earth Sciences 29 (2010) 2846


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1641 4 Ma, andNd TDM model age of 1.7 Ga and eNd(t)= +4.06. TheLa Cruz granite yields 207Pb/206Pb SHRIMP zircon age of1673 21Ma, NdTDMmodel age of 1.83 Ga and eNd(t)of +2.1.

3.1.2. Granitoid magmatismThe Pensamiento Granitoid Complex (PGC) forms much of the

Paragu Terrane, and is related to the San Ignacio Orogeny(Fig. 2). Herein we divided the PGC into two groups of granitoids(Table 1): (1) the syn- to late-kinematic granitoids (UPb SHRIMPzircon ages of 13731347 Ma) represented by La Junta, Florida,Puerto Alegre, San Martin and Campamento granites, and (2) late-

to post-kinematic granitoids comprising the Diamantina (UPbSHRIMP zircon age of 1340 Ma), Porvenir, Padre Eterno, Trs Picos,Orobayaya, Discordncia, El Tigre, San Cristobal granites and thePiso Firme Granophyre.

The La Junta and San Martin syn- to late-kinematic granites arecharacterized by Nd and Sr isotopic compositions (eNd(t)values of+1.8 to 3.7; Sri= 0.7052) and negative Nb and Ta anomalies indi-cating that different sources contributed to the granitoid magmagenesis in a Mesoproterozoic continental-margin arc system(Matos et al., 2009). Piso Firme and the Diamantina late- to post-kinematic granites exhibit 87Sr/86Sr ratios close to Bulk Earth andNdTDMages (1.921.51 Ga), which coupled with the eNd(t) values(1.25 to +3.90) indicate mixtures among MORB-like magmasand isotopic homogeneous protoliths (Darbyshire, 2000; Matoset al., 2009).

In the Brasilian side of the Paragu Terrane in Santa Brbara hill,

the PGC is characterized by voluminous crustally derived graniticplutons (Tarum Granite-Gneiss and Lajes Granite) emplaced alonga NNW structural pattern. The strongly foliated syn-kinematic Tar-um Granite-Gneiss shows UPb zircon age of 1.38 Ga; Nd

Fig. 2. Major orogens, geological units, and tectonic elements of the Paragu Terrane (eastern Bolivia) (modified from Litherland et al. (1986), Ruiz (2005), Matos et al.

(2009)).

https://www.researchgate.net/publication/236348392_Geochemistry_and_Nd-Sr_Isotopic_Signatures_of_the_Pensamiento_Granitoid_Complex_Rondonian-San_Ignacio_Province_Eastern_Precambrian_Shield_of_Bolivia_Petrogenetic_Constraints_for_a_Mesoproterozoic_Magm?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348392_Geochemistry_and_Nd-Sr_Isotopic_Signatures_of_the_Pensamiento_Granitoid_Complex_Rondonian-San_Ignacio_Province_Eastern_Precambrian_Shield_of_Bolivia_Petrogenetic_Constraints_for_a_Mesoproterozoic_Magm?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348392_Geochemistry_and_Nd-Sr_Isotopic_Signatures_of_the_Pensamiento_Granitoid_Complex_Rondonian-San_Ignacio_Province_Eastern_Precambrian_Shield_of_Bolivia_Petrogenetic_Constraints_for_a_Mesoproterozoic_Magm?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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Table 1

Summary of the main geological and geochronological features in the Paragu Terrane (RSIP southern sector).

Units Zone Lithology Composition Metamorphism andreformation

UPbShrimp(Zr) age(Ma)

K39Ar40

age(Ma)

Tectonic setting/Sources

ParaguTerrane

San Ignacio Orogen (SIO)Late-to-post-kinematicgranitoids

Bt-sienogranite, Btand Bt-Hbl-syenogranite

NordmarkiteTDM= 1.92 to1.65 GaeNd(t)= +2.75 to1.25

Alkaline Remelting of enriched crustalrocks

1340 13801244

Juvenilecharacterrelated to RSIO

Generated in acontinental,Andean-type,

orogenic arc relatedto RSIO continentalmargin calc-alkalinearc

PensamientoGranitoidComplex

Northern Granophyre, Qz-syenite Bt and Hbl-syenograniteTDM= 1.59 to1.51 GaeNd(t)= +3.9to +2.3

Metaluminous toweaklyperaluminous sub-alkaline to high -alkaline I typegranites (and scarceS-type)

Deformation andmigmatisation of basementrocks are related to RSIO

Differentmagmasources.

Juvenile/crustal sources.Partial meltingof lower crust

Syn- to late-kinematicgranitoids

Bt-granite, Hbl-Btmonzo-tosyenograniteAugen-gneissTDM= 2.1 to 1.68GaeNd(t)= +1.8 to -3.7

13731347

Granitoidrocks

Southern Bt-augengneiss, Hbl-Bt -granodioriteTonalite

TDM= 1.7

eNd(t)= -0.1

? 14291275

Pre-San Ignacio basement rocks (>1640 Ms)LomasManechisComplex

Charnockitic hyperstene granulites (granite).Enderbitic hyperstene granulites. Mafichyperstene (norite) granulite leptite.Granitic sills interleaved with psamitic andcalc-silicate metas. rocks.TDM= 2.07 to1.6Ga. eNd(t)= +4.0 to -3.97

? Upper amphibolite togranuiite facies (13191353Ma). High p(tot)> PH2Opartial remelting deformationand metamorphism related toRSIO (13191380 Ma)

16901660

?

San IgnacioSchist Group

Pelitic schist with psammitic layers:metavolcanics:metarhyolite, metabasalt. BIF,chert < 1.764Ma

Bimodal tholeiitic tocalc-alkaline

(tIckeness over 10km). High-grade gneiss with cordIeriteand hyperstene

Depositionafter1690Ma

Oceanic-floorsetting. Derivedfrom 1765 Masource

ChiquitaniaGneissComplex

Migmatic semi-pelitic gneiss associated toschist belts; banded micaceous qz.feld.gneiss.TDM= 1.86 to 1.74Ga eNd(t)=0.61 to4.88

? Upper amphibolite tomedium-grade facies. HighP(tot)> PH2O. Peakmetamorphism at 1333 Ma.Remelting

Detritalzircons17641678

13361323

?

References:Litherland and Bloomfield (1981), Berrang and Litherland (1982), Litherland et al. (1986), Boger et al. (2005), Ruiz et al. (2007), Santos et al. (2008), Matos et al. (2009). Mineral abbreviations afterKretz (1983).

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J.S.Bettencourtetal./JournalofSouthAmericanEarthSciences29(2010)2846
https://www.researchgate.net/publication/229285314_The_proterozoic_history_of_eastern_Bolivia?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/229285314_The_proterozoic_history_of_eastern_Bolivia?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/229285314_The_proterozoic_history_of_eastern_Bolivia?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348392_Geochemistry_and_Nd-Sr_Isotopic_Signatures_of_the_Pensamiento_Granitoid_Complex_Rondonian-San_Ignacio_Province_Eastern_Precambrian_Shield_of_Bolivia_Petrogenetic_Constraints_for_a_Mesoproterozoic_Magm?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/223653358_Age_and_autochthonous_evolution_of_the_Sunsas_Orogen_in_West_Amazon_Craton_based_on_mapping_and_U-Pb_geochronology?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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TDM= 1.9 Ga and eNd(t)= 4.11 and the weakly foliated late-kyne-matic Lajes Granite exhibits UPb zircon age of 1.31 Ga, NdTDM= 1.7 Ga and eNd(t)= 0.0 (Geraldes, 2000; Ruiz, 2005).

In the Ricardo Franco or Huanchaca hill the Pensamiento grani-toids are not affected by the Sunss Orogeny, and preserve the San

Ignacio metamorphic and deformational characteristics. In the VilaBela region, the PGC consists of syn-kinematic foliated NNW-trending monzogranite and granodiorite (Guapore Granite), andweakly foliated granites such as the Passagem Granite (1.29 Ga).Geochemical and isotopic signatures, and negative eNd(t)values ofthe San Ignacio related granitoids in Brazil indicate that theyformed in a continental magmatic arc and/or in a collisional conti-nental setting (Ruiz, 2005).

A reappraisal of the San Ignacio granitoids of the Southern Zoneas defined byLitherland et al. (1986)is on course, mainly based onprecise UPb SHRIMP ages and isotopic geochemistry. For example,the San Rafael granite (1334 12 Ma) was synchronous withthe San Ignacio Orogeny, and inherited zircon core age(1686 16 Ma) indicates that the granite interacted or was melted

from a Paleoproterozoic protolith (Boger et al., 2005). The San Ra-mon granite (1429 4 Ma, Nd TDM model age of 1.6 Ga andeNd(t)= +2.3) and San Andrs granite (1275 7 Ma) (Santos et al.,2008) indicate the existence of two magmatic events not relatedto the San Ignacio granitoid magmatism.

Elsewhere, Santos et al. (2008)reported SHRIMP UPb zirconages from Rio Fortuna 1336 3 Ma and Santa Rita 1319 6 Ma,orthogneisses, both previously considered as part of the Chiquita-nia Gneiss Complex byLitherland et al. (1986), are related to theSan Ignacio Orogeny.

3.1.3. Deformation and metamorphismThe San Ignacio Orogeny encompasses three WNW-directed

phases of deformation, subscripts Do1, Do2, and Do3 (Litherlandet al., 1986). The youngest, Do3, the major penetrative event, wasaccompanied by voluminous syn-kinematic granite intrusions,and migmatization of the 1690 Ma older sedimentary rocks, butsome of the late- to post-kinematic granitoids postdate Do3 phaseand were emplaced along a NNW trend (Litherland et al., 1986; Bo-ger et al., 2005). Sunss-age deformation was confined to Sunssand Aguape belts. In the Sunss Belt the main shear zones and tec-tonic front are the Rio Negro Front and Santa Catalina StraightZone, which define the northern limit of the Sunss Belt, and SanDiablo Front (Litherland et al., 1986). In the Aguape Belt the tec-tonic effects are represented by transpressive shear zones(e.g. San-ta Rita Shear Zone), and transposition of older structures parallel tothe N2040W/7080SW orogenic trend (Ruiz, 2005) (Fig. 1).

Upper-amphibolite mineral assemblage characterizes the Chiq-uitania and Lomas Manechis complexes, whereas the San Ignacio

Group is characterized by low- to medium-grade metamorphicminerals. UPb SHRIMP zircon rim ages from LMGC (orthopyrox-ene-bearing granitoid) yield a weighted 207Pb206Pb age of1320 11 Ma, and a biotite-bearing felsic gneiss (leucosome) fromthe CGC has zircon rims with UPb ages of 1333 6 Ma(Table 1).These ages are interpreted to reflect the time of partialmelting related to the peak metamorphism in the LMGC and CGCduring the San Ignacio Orogeny (Boger et al., 2005).

Other UPb SHRIMP zircon, monazite and titanite ages fromgranitoid rocks of the LMGC, Rio Fortuna orthogneiss, Santa Ritaorthogneiss suggest that high-grade metamorphism occurred overa long timeperiod between 1353 and 1319 Ma (Santos et al., 2008).Monazite from a Lomas Manechis granulitic rock has a metamor-phic age of 1339 4 Ma, which overlaps the 207Pb/206Pb age of

metamorphic zircons at 1338 21 Ma. The Rio Fortuna orthogneisshas magmatic zircons and rims formed at 1336 3 Ma. The SantaRita orthogneiss has magmatic zircons with 207Pb/206Pb age of1319 6 Ma. These authors concluded that all Lomas Manechis

granulite rocks and their counterparts observed in western Rond-nia are orogenic rocks formed during the time interval 13531319 Ma.

3.2. The Jauru Terrane (1.781.42 Ga)

The Jauru Terrane was defined by Saes and Fragoso Cesar (1996)to include Paleoproterozic metamorphic complexes resulting fromaccretions of intra-oceanic arcs into the Amazonia Central Prov-ince. In this paper, the composite Jauru Terrane consists of Paleo-proterozoic basement rocks (Alto Jauru Group, Figueira BrancaIntrusive Suite, Alto Guapor Metamorphic Complex and CabaalTonalite) and the Mesoproterozoic Cachoeirinha and Santa Helenaorogens. To the west a ductile shear zone marks the limit with theRio Alegre Terrane. To the north, east and south the limits are hid-den by Phanerozoic sedimentary sequences (Fig. 1).

3.2.1. Paleoproterozoic basement rocks (1.781.72 Ga)The Paleoproterozoic basement rocks consist of four lithostrati-

graphic units: The Alto Jauru Group, Figueira Branca IntrusiveSuite, Alto Guapor Metamorphic Complex, and Cabaal Tonalite(Fig. 3,Table 2).

The Alto Jauru Group (Monteiro et al., 1986) consists of gneis-ses, migmatites and three metavolcano-sedimentary sequences:Cabaal, Araputanga, and Jauru. Silicic to intermediate volcanicrocks have UPb ages of 1.761.72 Ga, and eNd(t) values are be-tween +2.6 and +2.2, allowing a dominantly juvenile mantle deri-vation for these rocks. Geochemical data from the Cabaaltholeiitic basalts suggest the incorporation of successive intra-oce-anic arcs within the Alto Jauru Group, during the evolution of thecontinental margin of the Rio Negro-Juruena Province (Pinhoet al., 1997; Geraldes et al., 2001). ArAr ages between 1.53 and1.46 Ga record metamorphic cooling related to the CachoeirinhaOrogeny.

The Figueira Branca Intrusive Suite (unknown age) is composedof numerous meta-basic and meta-ultrabasic plutons that intrudedthe Alto Jauru Group, are polydeformed and are metamorphosed athigh-amphibolite to greenschist facies (Saes et al., 1984; Ruiz,2005). The close association between the maficultramafic intru-sions and the Alto Jauru Group supracrustal rocks indicates thatthe rock association likely represents relicts of Paleoproterozoicoceanic crust (Ruiz, 2005).

The Alto Guapor Metamorphic Complex as defined by Menezeset al. (1993) consists of granodioritic to tonalitic orthogneiss,which intruded the volcano-sedimentary supracrustal sequences.The gneisses were metamorphosed at greenschist to amphibolitefacies. The oldest dated orthogneisses range in UPb zircon agesbetween 1.8 and 1.7 Ga. Positive eNd(t) values varying from +2.4

to 0.8 suggest a crustal contribution to largely mantle derivedmagma (Pinho, 1996; Geraldes et al., 2001; Ruiz, 2005). ArAr agesindicate that the gneisses were thermally affected during the Cach-oeirinha Orogeny at 1.51 Ga or reflect resetting during the SunssOrogeny (1.251.00 Ma) (Paulo, 2005; Ruiz, 2005).

The Cabaal Tonalite, first described by Monteiro et al. (1986), isa tonalite batholith metamorphosed at amphibolite facies, whichhad intruded in the Cabaal volcanic-sedimentary sequence (AltoJauru Group). Pb isotopic data suggest a crystallization age of1.78 Ga (Pinho, 1996). This segment of the Jauru Terrane was suc-cessively reworked during the Cachoeirinha (1.561.52 Ga) andSanta Helena orogenies (1.481.42Ga) (Ruiz, 2005).

3.2.2. The Cachoeirinha Orogen (1.561.52 Ga)

Rocks in the Cachoeirinha Orogen, initially described byCarnei-ro et al. (1992), evolved during the Cachoeirinha Orogeny (VanSchmus et al., 1998; Geraldes et al.,1999; Geraldes, 2000). TheCachoeirinha Orogen, herein interpreted as an accretionary orogen,

https://www.researchgate.net/publication/223653358_Age_and_autochthonous_evolution_of_the_Sunsas_Orogen_in_West_Amazon_Craton_based_on_mapping_and_U-Pb_geochronology?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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Fig. 3. Simplified geologictectonic map of SW Mato Grosso region showing major orogens, terranes and belts, tectonic elements, and lithologic units (modified fromRuiz, 2005).

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https://www.researchgate.net/publication/35685109_Evolucao_geologica_do_sudoeste_do_Craton_Amazonico_regiao_limitrofe_Brasil-Bolivia_-_Mato_Grosso?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/222884473_Geochemistry_and_isotopic_constraints_on_the_origin_of_the_mesoproterozoic_Rio_Branco_'anorogenic'_plutonic_suite_SW_of_Amazonian_craton_Brazil_High_heat_flow_and_crustal_extension_behind_the_Santa_He?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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is covered on the north and south by MesozoicCenozoic sedimen-tary sequences and is bounded to the east and west by the AltoJauru Group (Ruiz, 2005) (Fig. 3). Included in the orogen are tona-lite, granodiorite, granite and gneissic migmatite formed duringmagmatic and metamorphic events between 1.56 and 1.52 Ga

(Geraldes et al., 2001; Paulo, 2005; Ruiz, 2005; Arajo, 2008) (Ta-ble 2). These events also overprinted precursor lithotectonic unitsof the Jauru Terrane. Peak metamorphism during the CachoeirinhaOrogeny reached amphibolite facies, but has largely retrogressedto greenschist facies (Ruiz, 1992; Sousa et al., 2009).

According to Geraldes et al. (2001), Ruiz et al. (2004) and Arajo(2008), the Cachoeirinha Orogen evolved through two magmaticstages. A syn-kinematic stage is represented by the Santa CruzIntrusive Suite and a late-kinematic stage by the Alvorada IntrusiveSuite.

3.2.2.1. The Santa Cruz Intrusive Suite. The Santa Cruz Intrusive Suiteis a foliated NNW-trending, multiphased batholith (Ruiz et al.,2004; Ruiz, 2005; Arajo, 2008). The batholith has three distinct fa-

cies: (1) pink to red medium- to coarse- grained equigranular sye-nogranite through monzogranite (2) grayish to pink porphyriticmonzogranite, and (3) dark to light-gray inequigranular or med-ium- to coarse-grained porphyritic granodiorite. The geochemicaldata suggest that the suite is peraluminous and calc-alkaline incharacter. UPb zircon magmatic ages for these granitoids varyfrom 1.56 to 1.52 Ga. NdTDMmodel ages of 1.91.8 Ga, and eNd(t)values of +0.9 to +1.0 indicate that the protolith material has bothcrustal and mantle components (Geraldes et al. 2001; Ruiz, 2005).ArAr and KAr isotopic ages for the same suite varying from 1.53to 1.52Ga (Carneiro, 1985; Paulo, 2005), suggest that regionalcooling is related to the orogenic metamorphism. The orogenmight be considered as the roots of a continental-margin arc builtupon the Jauru Terrane (Geraldes et al., 2001; Ruiz et al., 2004;Ruiz, 2005; Arajo, 2008; Sousa et al., 2009).

3.2.2.2. The Alvorada Intrusive Suite. This suite, firstly described byMonteiro et al. (1986) and Ruiz (1992) consists of rounded to ellip-tical shaped granitic plutons composed of light-gray to pink col-ored medium- to fine-grained isotropic monzogranitic bodies,which are occasionally foliated.Geraldes et al. (2001), Ruiz et al.(2004) and Arajo (2008) reported UPb zircon magmatic agesfor these granitoids varying from 1.53 to 1.44 Ga, and Nd isotopicdata (Nd TDM model ages of 1.81.7 Ga and eNd(t) between +0.5and 1.3) suggest a mixing of juvenile mantle derived magmaswith recycled older material. The metaluminous to peraluminous,sub-alkaline, calc-alkaline geochemical and isotopic signatures ofthe suite are typical for volcanic arc granitoids (Ruiz, 2005; Arajo,2008; Sousa et al., 2009).

3.2.3. The Santa Helena Orogen (1.481.42 Ga)Basement rocks mainly of granitic composition were included

in the Santa Helena batholith (Saes et al., 1984). Later onGeraldeset al. (1997) and Van Schmus et al. (1998) proposed the term SantaHelena Suite (1.481.42 Ga), comprising igneous and meta-igneousrocks, represented by tonalite, orthogneiss, and granite, forming acalc-alkaline arc-related suite. Tassinari et al. (2000) upgradedthe Santa Helena Suite to orogen status. The Santa Helena Orogenis bordered to the west by the Rio Alegre Terrane (Piratininga ShearZone), to the east by Alto Jauru Group, and to the north and south itis covered by Mesozoic-Cenozoic sedimentary sequences (Fig. 3).

The Santa Helena Orogen is herein interpreted as an accretion-ary orogen, resulted from the development of a continental mag-

matic arc during the Santa Helena Orogeny. The orogenencompasses the syn-kinematic intrusions of the Santa Helenaand gua Clara intrusive suites (1.481.42 Ga) and PindaiatubaIntrusive Suite (1.461.42 Ga), as well as the post-kinematic or

anorogenic rapakivi granites and associated mafic rocks includedin the Rio Branco Intrusive Suite (1.42 Ga) (Geraldes et al., 2001,2004; Ruiz, 2005; Arajo, 2008) (Table 2).

3.2.3.1. The gua Clara Intrusive Suite. The suite is represented by a

batholith (Fig. 3), which comprises two petrographic facies: thedominant one is made up of gray-foliated medium- to coarse-grained equigranular granodiorite and the other subordinatedfacies comprises gray-foliated porphyritic granodiorite and monz-ogranites (Ruiz, 2005).Geraldes et al. (2001)provide an estimatefor the timing of magmatic activity at 1.48 Ga, and NdTDMmodelage of1.8 Gaand eNd(t) of +1.7 suggest an important juvenile sourcefor the batholith. The geochemical data show that the granitoidsare sub-alkaline, metaluminous to weakly peraluminous, and plotin the calc-alkaline field, reflecting a magmatic arc setting (Ruiz,2005).

3.2.3.2. The Santa Helena Intrusive Suite. The Santa Helena IntrusiveSuite consists of a batholith, which straddles the NNW trend and

encompasses four principal strongly foliated petrographic faciesassociations, which are syenogranite and monzogranite in compo-sition (Ruiz, 2005) (Fig. 3; Table 2). Geraldes et al. (2001) presentedUPb zircon magmatic ages for the batholith in the range of 1.461.42 Ga. The NdTDMmodel ages ranging from 1.5 to 1.6 Ga and theeNd(t)values between +2.7 and +4.0, indicate a largely juvenile sig-nature (Geraldes et al., 2001). Overall, the magmatism is sub-alka-line and of calc-alkaline chemistry and I-type characteristics. Theless evolved Santa Helena granitoid facies is slightly metaluminousand the most fractionated are weakly peraluminous, which indi-cate crustal contamination (Geraldes et al., 2001). On tectonic clas-sification diagrams, the rocks define distinct fractionation trendsand plot from the field of intra-plate granites to the volcanic arcgranites (Sousa et al., 2009). ArAr biotite and sericite ages forthe Santa Helena granites and schists vary from 0.91 to 0.89 Gaand are interpreted to reflect the regional Sunss reactivation (Pau-lo, 2005; Tohver et al., 2006).

3.2.3.3. The Pindaiatuba Intrusive Suite. The suite, consisting of sev-eral granitoid batholiths, plutons and stocks, is controlled by firstorder N3050W trending regional fault-zones (Fig. 3). The compo-nents of the suite are foliated or occasional mylonitic granitoidsand compositionally they range from tonalite to syenogranite. UPb zircon yielded crystallization ages varying from 1.46 to1.42 Ga (Table 2). The NdTDMmodel ages are in the range of 1.7to 1.8 Ga, whereas eNd(t)values vary from +0.03 to +2.33, indicatingthat the original magma was derived largely from juvenile sources.Geochemical results indicate that the Pindaiatuba Intrusive Suite ismetaluminous to peraluminous, medium to high-K calc-alkaline

tonalite and syenogranite, and the tectono-chemical diagramsshow that the granitoids plot within the volcanic arc granites field(Ruiz, 2005).

The ArAr ages byRuiz (2005)suggest four cooling events: (1)1.45 Ga biotite age from granodiorite; (2) 1.02 Ga biotite ages inmylonites that crosscut granodiorite; (3) 1.021.01 Ga biotite agesfrom foliated granites; and (4) 0.950.94 Ga biotite ages for granitebodies exhibiting tectonic foliation and mylonitization. The1.45 Ga biotite ages record the timing of cooling of the granodioritebody. The 1.02 Ga from mylonites and foliated granites record thetiming of regional deformation and regional metamorphic cooling,respectively. The 0.950.94 Ga biotite ages from granite record theage of penetrative foliation related to the Sunss Orogeny, and per-haps from the thermal effects due to younger Sunss granite

intrusions.

3.2.3.4. The Rio Branco Intrusive Suite. Rock units of the Rio BrancoIntrusive Sute intrude volcanicplutonic rocks of the Alto Jauru

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Terrane (Fig. 3) and are considered as part of a bimodal rapakiviigneous association byGeraldes et al. (1999, 2004a). The maficmember comprises gabbro, tholeiitic diabase dykes and porphy-ritic basalt, which show UPb zircon crystallization age of1471 8 Ma, Nd TDM model ages varying from 1.80 to 1.73 Ga,

and eNd(t) ranges from +1.9 to +1.2, suggesting a mantle sourceand crustal rock contributions (Geraldes et al., 2004a). The felsicmembers are mostly composed of red to pink granite rocks of sye-nitic to granitic composition which yielded UPb zircon age of1427 10 Ma, NdTDMmodel ages range of 1.891.81 Ga, and eNd(t)values varying from +0.2 to1.0, indicating an older crustal contri-bution in their source. The granites exhibit geochemical character-istics of A-type granite and are interpreted to have formed in aintra-plate setting (Geraldes et al., 2004a).

3.2.3.5. Deformation and Metamorphism. The Paleoproterozoicbasement exhibits compressive polyphase deformation pattern.The main structural elements comprise of refolded NEENWWtrending gneissic compositional banding and NNWstriking mylon-

itic zones, which show mass transport from NE towards SW. Themetamorphism reached high-amphibole facies, but has retrog-rassed to greenschist facies conditions. Granitoid rocks from theCachoeirinha Orogen show a N3040W/6070SE trending pene-trative foliation associated with shear zones characterized by atranspressive mass transport towards SW. The Santa Helena Oro-gen is deeply affected by the Sunss Orogeny (1.251.00 Ga) result-ing in a N3040W trending foliation parallel to the Aguape Belt(Indiava-Lucialva and Piratininga shear zones), and resetting theArAr system at 1.0 Ga (Ruiz, 2005).

3.3. The Rio Alegre Terrane (1.511.38 Ga)

The Rio Alegre Terrane was first defined as a suture zone by Saesand Fragoso Cesar (1996), coined as Rio Alegre Terrane bySaes(1999) or Rio Alegre Orogen by Matos et al. (2004). The terraneis bounded to the east by the Jauru Terrane (Piratininga shear zone)and to the west by the Paragu Terrane (Santa Rita shear zone) anddeformed sediments of the Aguape Group (1.171.15 Ga). Thenorthern and southern extensions are unknown (Matos et al.,2004), providing that the terrane is covered by Cenozoic sedimen-tary sequences (Fig. 1). The main geological features and geody-namic significance of the Rio Alegre Terrane are described indetail by Matos et al. (2004) and Ruiz (2005). This accretionary oro-gen comprises three units: Rio Alegre Volcanic-Sedimentary Unit,Maficultramafic Intrusive Suite, and Santa Rita Intrusive Suite(Fig. 3,Table 2).

3.3.1. Lithologic units

The Rio Alegre Volcanic-Sedimentary Unit comprises mafic andultramafic volcanic rocks, chemical and clastic sedimentary rocks,metamorphosed at greenschist to low-amphibolite facies. It hasbeensubdivided by Matos (1994) and Matos et al. (2004) into threesub-units, as follows:

(a) The Basal Minouro Formation consists of abundant basic toultrabasic volcanic rocks (basic metavolcanic and subvolca-nic rocks, fine-grained metabasalts and diabases), all associ-ated with fine-grained banded iron formations (withmagnetite-bearing layers), chemical sediments, chert andclastic rocks. The geochemical data indicate an ocean floortectonic setting for these rocks (Matos et al., 2004).

(b) The Intermediate Santa Isabel Formation comprises intermedi-

ate and acid lavas and pyroclastic rocks, represented by met-adacite, metarhyolite and associated meta-pyroclastic rocks.Two samples of metadacite yield UPb zircon ages of1509 10Ma and 1503 14Ma, NdTDM model ages of ca.

1.54 Ga, eNd(t)values of +4.3 and +4.8, respectively (Geraldeset al., 2000; Matos et al., 2004).

(c) The So Fabiano Formation comprises clastic, chemical andvolcaniclastic meta-sedimentary rocks represented by phyl-lites, quartzites, carbonaceous layers, garnet-kyanite-

muscovite-biotite schists, metacherts and banded ironformations.

The Maficultramafic Intrusive Suite crops out for hundreds ofkilometers to the NNW, and comprises mesocratic to melanocraticcoarse to very coarse-grained cumulate metaperidotite, metaharz-burgite, metaleucogabbros, metagabbros and serpentinites, whichare derived from metamorphosed dunite, peridotite and harzburg-ite. In UPb zircon data, these rocks yield ages ranging from1509 10 to 1494 11Ma, NdTDMmodel ages of ca. 1.67 Ga, andeNd(t)values of +4.5 to +2.5 (Matos et al., 2004).

The Santa Rita Suite Intrusive Suite comprises tonalite and gran-ites, intruded at the Rio Alegre Volcanic-Sedimentary Unit and Ma-ficultramafic Intrusive Suite, and metamorphosed at greenschist

to amphibolite facies. UPb zircon ages of these rocks vary from1444 15 to 1384 40 Ma, NdTDM model ages values are in therange of 1.521.49 Ga, and eNd(t)values vary from +3.7 to +3.6 (Ma-tos et al., 2004; Ruiz, 2005).

The lithologic association, geochemical and isotopic data sug-gest that the Rio Alegre Volcanic-Sedimentary Unit and Maficultramafic Intrusive Suite (1.511.49 Ga) were originated in mid-oceanic ridge setting, and the Santa Rita Intrusive Suite was formedin an oceanic island arc setting (1.441.38 Ga) (Matos et al., 2004;Ruiz, 2005).

3.3.2. Deformation and metamorphismThe NNW-trending Piratininga and Santa Rita mylonitic shear

zones constitute the main tectonic features observed in the RioAlegre Terrane, and are related to the Sunss Orogeny as demon-strated by ArAr muscovite age (0.9 Ga). However, the Rio Alegremetavolcanic-sedimentary unit shows a polyphase deformationpattern represented by gneissose banding and/or schistosity (S1)refolding phases related to Rio Alegre Orogeny. The structural ele-ments indicate a tectonic sense of vergence towards N3050W,under greenschist facies metamorphic conditions (Ruiz, 2005).

The So Fabiano Formation consists of a sequence of low-green-schist metamorphic facies compatible with the chlorite zone. Themaficultramafic intrusive rocks underwent low-grade metamor-phism, expressed by medium-grade greenschist facies conditions(biotite zone); transition to the high-greenschist facies metamor-phic conditions (garnet zone) occur in some area (Matos et al.,2004). The deformation pattern is polyphase and the structural ele-ments indicate a northeastward transport (Matos et al., 2004).

Metamorphism under greenschist to lower-amphibolite faciesand deformation are apparently associated with soft-accretion ofan oceanic island arc to the proto-Amazonian Craton during themesoproterozoic (Geraldes et al., 2006). The ArAr amphibole agesof 1.411.38 Ga and ArAr biotite ages ca. 1.32 Ga (Paulo, 2005;Tohver et al., 2006) are interpreted byGeraldes et al. (2006)asmetamorphic cooling of the Rio Alegre Orogen. However, in ouropinion, the ArAr ages of ca 1.32 Ga are related to the Rondo-nian-San Ignacio collision orogeny (1.341.32 Ga).

3.4. The RSIP in Rondnia

The RSIP in the Rondnia region includes geological units withages varying from1500 to 1300 Ma. Someof themare grouped into

a major tectonic unit, the Alto Guapor Belt (Quadros and Rizzotto,2007). The spatial and temporal distributions of these units areshown inFig. 4, and the main geological characteristics are sum-marized inTable 3.

https://www.researchgate.net/publication/239615440_Petrografia_Geoquimica_e_Geocronologia_das_Rochas_do_Orogeno_Rio_Alegre_Mato_Grosso_Um_Registro_de_Crosta_Oceanica_Mesoproterozoica_no_SW_do_Craton_Amazonico?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/239615440_Petrografia_Geoquimica_e_Geocronologia_das_Rochas_do_Orogeno_Rio_Alegre_Mato_Grosso_Um_Registro_de_Crosta_Oceanica_Mesoproterozoica_no_SW_do_Craton_Amazonico?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/239615440_Petrografia_Geoquimica_e_Geocronologia_das_Rochas_do_Orogeno_Rio_Alegre_Mato_Grosso_Um_Registro_de_Crosta_Oceanica_Mesoproterozoica_no_SW_do_Craton_Amazonico?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/239615440_Petrografia_Geoquimica_e_Geocronologia_das_Rochas_do_Orogeno_Rio_Alegre_Mato_Grosso_Um_Registro_de_Crosta_Oceanica_Mesoproterozoica_no_SW_do_Craton_Amazonico?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/239615440_Petrografia_Geoquimica_e_Geocronologia_das_Rochas_do_Orogeno_Rio_Alegre_Mato_Grosso_Um_Registro_de_Crosta_Oceanica_Mesoproterozoica_no_SW_do_Craton_Amazonico?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/222884473_Geochemistry_and_isotopic_constraints_on_the_origin_of_the_mesoproterozoic_Rio_Branco_'anorogenic'_plutonic_suite_SW_of_Amazonian_craton_Brazil_High_heat_flow_and_crustal_extension_behind_the_Santa_He?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/222884473_Geochemistry_and_isotopic_constraints_on_the_origin_of_the_mesoproterozoic_Rio_Branco_'anorogenic'_plutonic_suite_SW_of_Amazonian_craton_Brazil_High_heat_flow_and_crustal_extension_behind_the_Santa_He?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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Fig. 4. Simplifiedgeologictectonic map of Rondnia regionand eastern Bolivia, showing the approximate boundary of the mainprovinces, major tectonic features, lithologicunits, and compiled thermochronologic age data (modified fromLitherland et al. (1986), Rizzotto et al. (2004), Quadros and Rizzotto (2007) ).



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https://www.researchgate.net/publication/223653358_Age_and_autochthonous_evolution_of_the_Sunsas_Orogen_in_West_Amazon_Craton_based_on_mapping_and_U-Pb_geochronology?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348411_The_Rio_Crespo_Intrusive_Suite_geological_U-Pb_and_Sm-Nd_isotopic_evidence_for_a_major_143_Ga_arc-related_magmatism_in_the_Rondonia_State_SW_Amazonia_Craton_Brazil?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/242408081_SHRIMP-RG_UPb_ZIRCON_GEOCHRONOLOGY_OF_GNEISS_FROM_THE_RIO_CRESPO_INTRUSIVE_SUITE_SW_AMAZONIAN_CRATON_RONDONIA_BRAZIL_NEW_INSIGHT_ABOUT_PROTOLITH_CRYSTALLIZATION_AND_METAMORPHIC_AGES?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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The controversialboundary between the RSIP and Rio Negro-Juruena Province was earlier inferred based on RbSr and KArages (Cordani et al., 1979; Teixeira et al., 1989). This, plus furtherTassinari et al. (1996)UPb zircon ages, and more recently ArArages, ledCordani and Teixeira (2007)to re-evaluate this contact.

It is postulated a new inferred boundary, which is not a structuralbut rather is based on the spatial distribution of the RSIP geologicalunits, KAr, ArAr and UPb thermal imprints (Figs. 1 and 4).

3.4.1. Anorogenic suites3.4.1.1. Rio Crespo Intrusive Suite. In the Rondnia region the RioCrespo Intrusive Suite (ca. 1500 Ma;Bettencourt et al., 2006) isthe oldest recognized geologic unit of the RSIP. This unit formsan elongated EW area across the central Rondnia. The easternand western extensions of the unit are poorly known (Fig. 4).

The Rio Crespo Intrusive Suite (Payolla et al., 2001) is repre-sented by pink or greenish, fine- to medium-grained, quartz-feld-spathic banded gneisses showing medium- to high-grademetamorphic facies. Banding is defined by alternating quartz +

plagioclase + K-feldspar layers and hornblende + magnetite + titan-ite + epidote garnet orthopyroxene clinopyroxene discontinu-ous layers and enhanced by concordant, locally folded graniticveins. Metacharnockite (ca. 1.56 Ga) and mafic granulite (ca.1.73 Ga) xenoliths support an intrusive origin for the protolith ofthe fine-grained gneisses and granulites. Preliminary geochemicaldata indicate that these rocks are characterized by strong ironenrichment, have metaluminous to marginally peraluminous com-positions and exhibit a high- to ultra high-K signature (Payollaet al., 2002). Their trace element contents are comparable to thePhanerozoic A-type and intra-plate granites. The positive eNd(t)(+1.0 and +1.8) and the narrow range of Nd TDM model ages(1.731.75Ga) of these rocks suggest that they represent juvenilematerial with minor older crustal source contributions (Betten-court et al., 2006).

3.4.1.2. Santo Antnio Intrusive Suite. The Santo Antnio IntrusiveSuite (14001360 Ma; Bettencourt et al. 1999; Quadros and Rizzot-to, 2007), along with the Teotnio Intrusive Suite, form the com-posite Santo Antnio batholith in the northern part of Rondnia(Fig. 4). This batholith covers an area of ca. 2000 km2, but its truedimension is unknown because the northern domain is overlainby Phanerozoic continental sediments of the Amazon basin.

The Santo Antnio Intrusive Suite is composed of two main gra-nitic types. These are seriate to locally porphyritic biotite monzog-ranite and syenogranite, and equigranular biotite monzogranite.Some distinctive rock types of smaller areal extent include fine-grained hornblende-biotite quartz monzonite, dyke-like bodies ofhybrid rocks (monzogranite, quartz monzonite, and quartz monzo-

diorite) and syn-plutonic diabase dykes. The granites are sub-alka-line and slightly peraluminous rocks showing high Fe/Mg, K, F, Rb,Ga, Nb, Zr, and REE, aswell as low Ca, Mg, P, and Sr, being similar toPhanerozoic intra-plate and A-type (A2 group) granites (Payolla,1994; Bettencourt et al., 1997).

3.4.1.3. Teotnio Intrusive Suite. The Teotnio Intrusive Suite (ca.1387 Ma;Bettencourt et al. 1999) apparently forms a minor partof the Santo Antnio batholith at the present level of erosion(Fig. 4). The rocks of this suite were described byPayolla (1994)in the Teotnio cataract area. Major units are massive coarse-grained alkali-feldspar granite, banded medium-grained alkali-feldspar granite and pink coarse- to medium-grained quartzalkali-feldspar syenite with less common alkali-feldspar granite

and syenogranite. Sparse fayalite-clinopyroxene alkali-feldsparsyenite dykes and syn-plutonic diorite, monzodiorite and monzo-nite dykes cut the granites and syenogranites. Fine-grained sye-nogranite and monzogranite dykes cut the early rocks. The

syenite and granites are metaluminous, and define an alkaline sil-ica-oversaturated series with high Fe/(Fe + Mg). The granites showgeochemical characteristics of Phanerozoic intra-plate and A-type(A1 group) granites (Payolla, 1994; Bettencourt et al., 1997).

3.4.2. The Alto Guapor BeltThe Alto Guapor Belt is a WNWESE trending area (ca.500 100 km), in the southern and southeastern Rondnia region.The northern boundary is the Pacas Novos basin, Alto CandeiasIntrusive Suite, Nova Brasilndia Terrane and Rio Negro-JuruenaProvince. To the south and east the boundaries are poorly known,providing that the limits are overlain by Phanerozoic sedimentarysequences (Fig. 1). Herein the belt is characterized as an accretion-ary orogen comprising at least six units (Fig. 4,Table 3): TrincheiraMaficultramafic Complex, Colorado Complex, Nova MamorMetamorphic Suite, Serra do Colorado Intrusive Suite, IgarapEnganado Intrusive Suite and Alto Escondido Intrusive Suite.

3.4.2.1. Trincheira Maficultramafic Complex. The Trincheira Mafic

ultramafic Complex (unknown age) consists mostly of bandedamphibolite, metagabbro, amphibolitic gneiss, metapyroxenite,metabasalt, and serpentinite. Preliminary geochemical data sug-gest that the amphibolites and metagabbros show geochemicalcharacteristics of N-MORB (Rizzotto and Quadros, 2007) althoughsome samples exhibit composition ranges of Nd and Sr isotopes(eNd(t)= + 4.1 and +5.2; and eSr(t)= 5.0 and 30.7), and trace ele-ment geochemistry of oceanic arc basalts (Girardi et al., 2008).

3.4.2.2. Colorado Complex. The Colorado Complex is a meta-sedi-mentary sequence, and is composed of paragneiss, pelitic schist,calc-silicate gneiss, para-amphibolite, and BIF. The protolith of par-agneiss and pelitic schist is interpreted as a turbiditic sequencedeposited in a passive margin basin (Quadros and Rizzotto,2007). UPb zircon ages of 1420 Ma (detrital zircon) and of1340 Ma (metamorphic zircon) bracket deposition of the originalsedimentary protolith of the paragneiss. The main detrital zirconage group (ca. 1508 13 Ma) shows that the clasticwedge sedi-ment was predominantly recycled from the Rio Crespo IntrusiveSuite (ca. 1.50 Ma), and two other subordinate zircon age groups(ca. 1938 and 1645 Ma) indicate a Paleoproterozoic crust prove-nance (Rizzotto and Quadros, 2007).

3.4.2.3. Nova Mamor Metamorphic Suite. The Nova Mamor Meta-morphic Suite was first described in the western side of Rondniaas Nova Mamor Complex (Quadros and Rizzotto, 2007). However,in our opinion, mainly based on field geological mapping, is thatthe lithotypes are of restricted occurrence and constitute scatteredrock remnants along the Rio Crespo Intrusive Suite. The suite is a

meta-sedimentary sequence and shows geological similarities tothe Colorado Complex. It is composed of migmatitic paragneiss(pelitic and psamitic gneisses), calc-silicate gneiss and granofels,quartz-fedspasthic granofels, and pelitic schist. The protolith ofthe paragneiss and pelitic schist is interpreted to be a turbiditic se-quence deposited on a passive margin basin (Quadros and Rizzotto,2007). UPb detrital zircon ages vary between 2030 and 1532 Ma,and metamorphic zircons yield an age of 1345 Ma. The timing ofthe deposition of the sedimentary protolith is between 1532 and1345 Ma (Rizzotto and Quadros, 2007).

3.4.2.4. Serra do Colorado Intrusive Suite. The Serra do ColoradoIntrusive Suite comprises layered maficultramafic complexes,which are intrusive in the Trincheira and Colorado complexes.

The suite is made of metagabbro, metagabbronorite, anorthosite,hornblendite, and serpentinite (Quadros and Rizzotto, 2007; Rizz-otto and Quadros, 2007). A sample of metagabbro yields a crystal-lization age of 1352 Ma, and shows geochemical and radiogenic

https://www.researchgate.net/publication/233287157_Geochronological_Systematics_on_Basement_Rocks_from_the_Rio_Negro-Juruena_Province_Amazonian_Craton_and_Tectonic_Implications?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/223609457_A_review_of_the_geochronology_of_the_Amazonian_Craton_tectonic_implications_Precambrian_Res_42_213-227?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348411_The_Rio_Crespo_Intrusive_Suite_geological_U-Pb_and_Sm-Nd_isotopic_evidence_for_a_major_143_Ga_arc-related_magmatism_in_the_Rondonia_State_SW_Amazonia_Craton_Brazil?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/242408081_SHRIMP-RG_UPb_ZIRCON_GEOCHRONOLOGY_OF_GNEISS_FROM_THE_RIO_CRESPO_INTRUSIVE_SUITE_SW_AMAZONIAN_CRATON_RONDONIA_BRAZIL_NEW_INSIGHT_ABOUT_PROTOLITH_CRYSTALLIZATION_AND_METAMORPHIC_AGES?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/233287157_Geochronological_Systematics_on_Basement_Rocks_from_the_Rio_Negro-Juruena_Province_Amazonian_Craton_and_Tectonic_Implications?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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isotope (eNd(t)= +2.1 and eSr(t)= 17.1) features of N-MORB andOAB (Rizzotto et al., 2002; Teixeira et al., 2006; Girardi et al., 2008).

3.4.2.5. Igarap Enganado Intrusive Suite. The Igarap EnganadoIntrusive Suite includes mainly syenogranite, monzogranite, and

granodiorite, together with rare tonalite, gabbro, and hybrid rock.The suite intrudes the supracrustal rocks of the Colorado complexand normally shows magmatic and/or metamorphic foliation(Quadros and Rizzotto, 2007). Foliated monzogranite and syenog-ranite provide a similar UPb zircon crystallization age of1340 5 Ma (SHRIMP zircon method) and the samples give posi-tive eNd(t)values of +2.8 and +2.3, respectively (Rizzotto and Quad-ros, 2007), suggesting a dominant juvenile character of themagmas. The rocks have metaluminous character with high-Kcalc-alkaline affinities and the granites show trace elements simi-larities to collisional granites (Rizzotto and Quadros, 2007).

3.4.2.6. Alto Escondido Intrusive Suite. The Alto Escondido IntrusiveSuite is composed of monzogranite and syenogranite and is intru-

sive in the Trincheira and Colorado Complexes as well as in the Iga-rap Enganado Intrusive Suite (Quadros and Rizzotto, 2007). Asyenogranite gives a UPb zircon crystallization age of1336 4 Ma (TIMS method), and positiveeNd(t)value of +2.0 (Rizz-otto and Quadros, 2007), suggesting a dominant juvenile characterof the magmas. The rocks are marginally peraluminous to metalu-minous and exhibit high-K calc-alkaline affinities, with trace ele-ments similarities to post-collisional granites (Rizzotto andQuadros, 2007).

3.4.3. Late- to post-tectonic suites3.4.3.1. Alto Candeias Intrusive Suite. The Alto Candeias IntrusiveSuite is largely composed of coarse- to medium-grained porphy-ritic granites and pyterlites, with lesser amounts of porphyriticcharnockites, medium- to fine-grained equigranular granite andsyenite (Bettencourt et al., 1997). Three samples of the granitesprovide intrusion ages between 1346 and 1338 Ma (Bettencourtet al., 1999; Santos et al., 2008). The granites are sub-alkaline,metaluminous, and show geochemical characteristic of Phanerozo-ic intra-plate and A-type granites (Bettencourt et al., 1997).

3.4.3.2. So Loureno-Caripunas Intrusive Suite. The So Loureno-Caripunas Intrusive Suite consists of normal rapakivi granite vari-eties, such as pyterlite and minor wiborgite, along with associatedporphyritic and equigranular granites and subvolcanic and volca-nic felsic rocks (Bettencourt et al., 1997). Two granites and one rhy-olite porphyry, analysed by Bettencourt et al. (1999), yieldintrusion ages between 1314 and 1309 Ma. The rocks are sub-alka-line, metaluminous to marginally peraluminous, and show strong

iron enrichment. They have A-type and intra-plate granite traceelement signatures (Bettencourt et al., 1997) and are consideredto be a late manifestation of the Rondonian-San Ignacio Orogeny.

3.4.4. Deformation and metamorphismThe basement rocks of the RSIP in Rondnia region are marked

by a wide network of sinistral strike-slip displacement shear zonescalled Ji-Paran and Rio Formoso-Ariquemes shear zones (Fig. 4)(Scandolara et al., 1999; Tohver et al., 2004, 2005, 2006; Scandolar-a, 2006). According to Scandolara (2006) these shear zones aredeveloped within the time interval 1.201.15 Ga at lower-amphib-olite fcies metamorphism, and all are related either to the lateRondonian-San Ignacio Orogeny stage or to the opening of theNova Brasilndia basin. Instead Tohver et al. (2006) report that

the basement rocks in Rondnia mostly preserve ages older than1.3 Ga and, localized isotopic ArAr age resetting at 1.181.12 Gais caused by Grenvillian activation of widespread sinistral strike-slip shear zones. Whether the shear zones were generated during

the Rondonian-San Ignacio Orogeny and, subsequently reactivatedat 1.181.12 Ga or created during the Sunss Orogeny remains anopen question.

The Rondonian-San Ignacio event (1.341.32 Ga) is character-ized by metamorphic mineral assemblages and anatexis, which

are suggestive of upper-amphibolite to granulite facies metamor-phism, and are widely developed in the supracrustal rocks of theColorado Complex and Nova Mamor Metamorphic Suite (Quadrosand Rizzotto, 2007; Rizzotto and Quadros, 2007). A tectono-meta-morphic imprint over rocks of the Rio Crespo Intrusive Suite andthe Rio Negro-Juruena Province is reported in the Ji-Paran andAriquemes region, mainly based on UPb zircon, monazite andtitanite ages, as well as ArAr in hornblende, biotite and muscoviteages (Fig. 4,Table 3) (Payolla et al., 2002; Silva et al., 2002; Tohveret al., 2005; Bettencourt et al., 2006; Scandolara, 2006; Santoset al., 2008). Hornblende and biotite ArAr ages are interpretedto mark cooling as granitic magmatism waned, deformation ceasedand stability was achieved. Also the syn- to post-Rondonian-SanIgnacio magmatism and regional thermal effects are interpreted

to be related to crustal thickening associated with the collision oc-curred between the Paragu Block and the Rio Negro-JuruenaProvince.

3.5. Regional correlations

The Rondonian Province (Teixeira and Tassinari, 1984) and SanIgnacio Orogen (Litherland et al., 1986, 1989) have been consideredtorepresent coeval segments of Mesoproterozoic crustal growthalong the SW margin of the Amazonian Craton (Teixeira et al,1989; Tassinari et al., 2000; Cordani and Teixeira, 2007). However,this model is controversial (Tohver et al., 2004; Boger et al., 2005).According toTohver et al. (2004)the EW trending Nova Brasiln-dia Belt marks the limit between the Amazonian and Paragu cra-tons, and formed during the late Mesoproterozoic. If true, thencorrelations in the basement province across the belt, includingthe RISP, are not possible. On the other hand, Boger et al. (2005)proposed that the Proterozoic rocks of eastern Bolivia (the ParaguCraton) evolved in four geologic distinct stages not present in theRondnia and Mato Grosso regions of western Brazil. They con-clude that the Paragu Craton was allochthonous with respect tothe southwestern margin of the Amazonia. The time-space chartof events in the Rondonian-San Ignacio Province in SW AmazonianCraton is shown inFig. 5.

According toBoger et al. (2005)the San Ignacio Schist Group(SISG), Chiquitania Gneissic Complex (CGC) and the Lomas Mane-chis Granulitic Complex (LMGC) have no equivalents in SW MatoGrosso and Rondnia. However, detrital zircons suggest that theSIG and CGC may be the temporal equivalents to the Quatro Cac-

hoeiras Suite (Quadros and Rizzotto, 2007) or to the Machadinhoparagneisses (Payolla et al., 2002), in the Rondnia region. More-over the 16571677 Ma magmatic and metamorphic events ob-served by Santos et al. (2000, 2008) and Silva et al. (2002),denote the presence of correlatable LMGC units in Rondnia.Zircon core ages from LMGC (17751715Ma,Boger et al., 2005)and Rio Fortuna orthogneiss (17721734 Ma,Santos et al., 2008)are comparable with zircon crystallization ages from rocks ofthe Jamari Complex (1.761.73 Ga) in Rondnia. One magmaticzircon from the LMGC yields an age of 1818Ma, which suggestsan older crust in eastern Bolivia, comparable to the basementages of the Juruena region in northern Mato Grosso (Santoset al., 2008). These facts suggest that the Paragu Terrane couldbe a segment of the Rio Negro-Juruena Province detached at ca.

1.501.40 Ga time interval, consistent with the model ofSadowskiand Bettencourt (1996).

Currently, no correlatable units of the Cachoeirinha accretion-ary orogen (1.561.52 Ga) in the Jauru Terrane are known in

https://www.researchgate.net/publication/223167550_A_New_Understanding_of_the_Provinces_of_the_Amazon_Craton_Based_on_Integration_of_Field_Mapping_and_U-Pb_and_Sm-Nd_Geochronology?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/232392351_U-Pb_age_data_from_the_Sunsas_region_of_Eastern_Bolivia_evidence_for_the_allochthonous_origin_of_the_Paragua_Block?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348454_Caracterizacao_geocronologica_da_Provincia_Rondoniana_e_suas_implicacoes_geotectonicas?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236016498_Restored_transect_across_the_exhumed_Grenville_orogen_of_Laurentia_and_Amazonia_with_implications_for_crustal_architecture?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/248450726_Geological_evolution_of_the_basement_rocks_in_the_east-central_part_of_the_Rondonia_Tin_Province_SW_Amazonian_craton_Brazil_U-Pb_and_Sm-Nd_isotopic_constraints?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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Rondnia region, although the rapakivi granites and related rocksof the Serra da Providncia Intrusive Suite (1.601.53 Ga) have

been interpreted as a probable inboard expression of the subduc-tion-related magmatism of the Cachoeirinha Orogeny (Bettencourtet al. 1999; Tassinari et al., 2000; Payolla et al., 2002; Geraldeset al., 2004b). Conversely, we suggest that the Serra da ProvidnciaIntrusive Suite is part of the Rio Negro-Juruena Province (Table 3)and related to a tectono-metamorphic event dated at 16701630 Ma (Santos et al., 2008). Both proposals deserve furtherinvestigation.

The A-type and intra-plate granites of the Rio Crespo IntrusiveSuite in Rondnia region (ca. 1500 Ma) have no equivalents inthe Jauru and Paragu terranes (Bettencourt et al., 2006). However,these rocks are age-correlative with intermediate volcanic rocks(15101500 Ma) of the Rio Alegre Terrane. Based on these observa-tions, we propose that the initial rifting along the flanks of the Rio

Negro-Juruena Province was firstly accompanied by the intrusionof the Rio Crespo Intrusive Suite and followed by the Santo AntnioIntrusive Suite (14001360 Ma) and Teotnio Intrusive Suite (ca.1387 Ma).

The Santa Helena accretionary orogen (1.481.42 Ga) is largelyrepresented by the syn-kinematic Santa Helena and gua Clara

intrusive suites (1.481.42 Ga), the Pindaiatuba Intrusive Suite(1.461.42 Ga), and by the post-kinematic and/or anorogenic, bi-modal rapakivi Rio Branco Suite (1.42 Ga) (Geraldes et al., 2001;Geraldes et al., 2004; Ruiz, 2005). San Ramn tonalite (1429 Ma)in the Paragu Terrane may represent correlative magmatic activ-ity (Santos et al., 2008).

The Pensamiento Granitoid Complex (13731340 Ma) is time-correlated with the Igarap Enganado Intrusive Suite (1340 Ma),Alto Escondido Intrusive Suite (1336 Ma) (Alto Guapor Belt), aswell as with the Alto Candeias Intrusive Suite (13461338 Ma).These granitoid rocks exhibit distinct petrographic and geochemi-cal characteristics, which suggest involvement of different tectonicsettings and magmas sources for their formation, during the sameperiod of time (13731336 Ma). In this context the Pensamiento

Granitoid Complex was generated in an Andean-type magmaticarc, the Igarap Enganado and Alto Escondido intrusives suiteswere formed in an intra-oceanic arc and the Alto Candeias Intru-sive Suite shows intra-plate and A-type granite affinities.

Fig. 5. Tectono-stratigraphic time-space plot showing the timing of major orogenic events, igneous events, depositional packages, and Nd TDMranges for the Rondonian-SanIgnacio Province. RSIO, Rondonian-San Ignacio Orogeny; RCIS, Rio Crespo Intrusive Suite; NMMS, Nova Mamor Metamorphic Suite; TIS-SAIS, Teotnio and Santo Antniointrusive suites; ACIS, Alto Candeias Intrusive Suite; SLCIS, So Loureno-Caripunas Intrusive Suite; TMUC, Trincheira Maficultramafic Complex; CC, Colorado Complex; SCIS,Serra do Colorado Intrusive Suite; IEIS-AEIS, Igarap Escondido and Alto Enganado intrusive suites; CO, Cachoeirinha Orogeny; RAO, Rio Alegre Orogeny; SHO, Santa HelenaOrogeny; SCIS, Santa Cruz Intrusive Suite; AIS, Alvorada Intrusive Suite; RAV, Rio Alegre Volcanic-Sedimentary Unit; SRIS, Santa Rita Intrusive Suite; SHIS, Santa HelenaIntrusive Suite; PIS, Pindaituba Intrusive Suite; RBIS, Rio Branco Intrusive Suite; PGC, Pensamiento Granitoid Complex; SR, San Ramn Granitods; SIO, San Ignacio Orogeny.Data fromLitherland et al. (1986), Tassinari et al. (1999), Bettencourt et al. (1999, 2006), Geraldes et al. (2001), Payolla et al. (2001, 2002), Silva et al. (2002), Matos et al.(2004), Boger et al. (2005), Ruiz (2005), Tohver et al. (2005), Tohver et al. (2006), Scandolara (2006), Quadros and Rizzotto (2007), Rizzotto and Quadros (2007), Santos et al.(2008), Matos et al. (2009).

https://www.researchgate.net/publication/279539867_Geochronological_provinces_of_the_Amazonian_Craton?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/279539867_Geochronological_provinces_of_the_Amazonian_Craton?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/279539867_Geochronological_provinces_of_the_Amazonian_Craton?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348411_The_Rio_Crespo_Intrusive_Suite_geological_U-Pb_and_Sm-Nd_isotopic_evidence_for_a_major_143_Ga_arc-related_magmatism_in_the_Rondonia_State_SW_Amazonia_Craton_Brazil?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/279539867_Geochronological_provinces_of_the_Amazonian_Craton?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/236348411_The_Rio_Crespo_Intrusive_Suite_geological_U-Pb_and_Sm-Nd_isotopic_evidence_for_a_major_143_Ga_arc-related_magmatism_in_the_Rondonia_State_SW_Amazonia_Craton_Brazil?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/242408081_SHRIMP-RG_UPb_ZIRCON_GEOCHRONOLOGY_OF_GNEISS_FROM_THE_RIO_CRESPO_INTRUSIVE_SUITE_SW_AMAZONIAN_CRATON_RONDONIA_BRAZIL_NEW_INSIGHT_ABOUT_PROTOLITH_CRYSTALLIZATION_AND_METAMORPHIC_AGES?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==https://www.researchgate.net/publication/223388022_Mesoproterozoic_rapakivi_granites_of_the_Rondonia_Tin_Province_southwestern_border_of_the_Amazonian_craton_Brazil_-_I_Reconnaissance_U-Pb_geochronology_and_regional_implications?el=1_x_8&enrichId=rgreq-424ff1a7-a330-49b5-ade8-8476d6c69a31&enrichSource=Y292ZXJQYWdlOzIyMjkxMzc1MDtBUzoxMDEwMjYxMDc0OTQ0MjVAMTQwMTA5NzkxMDEyOQ==


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Deformation and high-grade metamorphism are recognizedalong the extent of the RSIP mainly in the Paragu Terrane andRondnia region, more frequently between 1340 and 1320 Ma.Peak metamorphism and partial melting are recorded in the LomasManechis Granulitic Complex (13391320 Ma) and Chiquitania

Gneiss Complex (ca. 1333 Ma) (Paragu Terrane) (Boger et al.,2005; Santos et al., 2008), and in the Colorado Complex and NovaMamor Metamorphic Suite (Alto Guapor Belt) at ca. 1340 Ma(Tassinari et al., 1999; Payolla et al., 2002; Quadros and Rizzotto,2007; Rizzotto and Quadros, 2007).

3.6. Tectonic framework

The basement rocks (>1560 Ma) which constitute the continen-tal-margin framework to which all the studied Mesoproterozoicorogen where accreted comprise: the Chiquitania Gneiss Complex

and San Ignacio Schist Group (P1.69 Ga) and the Lomas ManechisGranulitic Complex (1.691.66 Ga) in the Paragu Terrane (Bogeret al., 2005); the Alto Jauru Group (1.761.72 Ga), Figueira BrancaIntrusive Suite, Alto Guapor Metamorphic Complex (1.81.7 Ga)and Cabaal Tonalite (1.78 Ga) in the Jauru Terrane (Ruiz, 2005)

and the Jamari Complex (1.761.73 Ga), Mutum Paran Formation(1.75 Ga), Igarap Lourdes Formation, Quatro Cachoeiras Suite(P1.60 Ga) and Serra da Providncia Intrusive Suite (1.601.53 Ga) in the Rio Negro-Juruena Province in Rondnia region(Quadros and Rizzotto, 2007) (Tables 13).

The following RSIP tectonic evolution and discussion hereinproposed is keyed toFig. 6and provide a summary of the chronol-ogy of events in the time interval 1.561.30 Ga, taking into accountthe currently geological mapping, petrological and geochemicaldata, UPb TIMS and SHRIMP and ArAr dating. For this purposewe have divided the RSIP into two sectors: northern sector

1560 - 1520 Ma

1480 - 1420 Ma

1440 - 1380 Ma

1370 - 1340 Ma

1340 - 1320 Ma

SCIS, AIS

ACIS, SHIS, PIS

SRIS

SHO CAO

PT

RNJP

RNJP

RNJP

RBISCAO

++

+++ +

++

+++ +

CACHOEIRINHA

SANTAHELENA

RIOA

LEGRE

SAN

IGNACIO

RO

NDONIAN-SAN

IGNACIO

OROGENY

OROGENY

OROGENY

OROGENY

OROGENY

JAURU TERRANEJAURU TERRANE

RIO NEGRO-JURUENAPROVINCE

RIO ALEGRETERRANERIO ALEGRETERRANE

ALTO GUAPORBELT

PARAGUTERRANEPARAGUTERRANE

PARAGUTERRANE

+ ++

++ +

++

+++ +

+

1400 - 1387 Ma

1500 Ma

< 1420 Ma

1370 - 1340 Ma

1340 - 1320 Ma

1315 - 1300 Ma

PGC

PGC

AGB

AGB

ACIS

ACIS

RCIS(R)

RCIS(R)

RNJP (R)

RNJP (R)

SLCISSAIS, TIS

SAIS, TIS

PT(R)

PT(R)

PB

PGCPGCSCIEIS

AEIS

IS

RCIS

RNJP

RNJP

SAIS, TISTMUC

CCNMMSPBPB

TMUC

CCNMMS RCIS RNJP SAIS, TIS?

?

RCIS SAIS, TIS RNJP

RCIS

X

X

X

X

X

X X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

++

++

++ +

+

+ +++

+ +++

++

+++

+++

+++ +

+

+++

+++ +

+

X X

X X

X X

X

X

X

X

X X

X

X X

X X

X X

X

X X

X

X X

X

++

+++ +

++

+++

+ +

++

++ +

+

+ +++ +

+

RIFTSTAGE

DRIFTSTAGE

SUBDUCTION

STAGE

SUBDUCTION

STAGE

COLLISIO

NAL

STAGE

COLLISIO

NAL

STAG

E

POST-COLLISIONAL

STAGE

+++

++

+ ++ +

+

+++

++

+ ++ ++

RAO

RAO

SHO

SHO

CAO

CAO

RNJP

RNJP

A B

Fig. 6. Hypothetical simplified cartoon version, showing proposed tectonic evolution of the RSIP (see text for explanation). (A) During the time interval 15601320 Ma(southern sector). RNJP, Rio Negro-Juruena Province; SCIS, Santa Cruz Intrusive Suite; AIS, Alvorada Intusive Suite; ACIS, gua Clara Intrusive Suite; SHIS, Santa HelenaIntrusive Suite; PIS, Pindaiatuba Intrusive Suite; CAO, Cachoeirinha Orogen; RBIS, Rio Branco Intrusive Suite; SRIS, Santa Rita Intrusive Suite; SHO, Santa Helena Orogen; PB,

Paragu Block; PGC, Pensamiento Granitoid Complex;RAO, Rio Alegre Orogen; PT, Paragu Terrane. (B) During the time interval 15001300 Ma (northernsector). RNJP(R), RioNegro-Juruena Province (Reworked); RCIS, Rio Crespo Intrusive Suite; RCIS(R), Rio Crespo Intrusive Suite (reworked); SAIS, Santo Antnio Intrusive Suite; TIS, TeotnioIntrusive Suite; TMUC, Trincheira Maficultramafic Complex; CC, Colorado Complex; NMMS, Nova Mamor Metamorphic Sute; SCIS, Serra do Colorado Intrusive Suite; IEIS,Igarap Enganado Intrusive Suite; AEIS, Alto Escondido Intrusive Suite; ACIS, Alto Candeias Intrusive Suite; SLCIS, So Loureno-Caripunas Intrusive Suite; AGB, Alto GuaporBelt.



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(Fig. 4) and southern sector (Figs. 2 and 3). We envisage the evolu-tion of the RSIP into two distinct evolutionary periods: 15601370and 13701300 Ma. The older period is marked by diachronousevents, leading to the building of the Cachoeirinha, Santa Helenaand Rio Alegre accretionary orogens (southern sector), and rifting

and oceanic spreading (northern sector), along the flanks of theRio Negro-Juruena Province. The second period is synchronousalong the entire continental margin, and encompasses subductionof oceanic lithosphere and microcontinent (Paragu Block) conti-nent (proto-Amazonian Craton) collision. Based on this analysis,the RSIP is interpreted as a composite orogen or an orogeneticsystem, comprising an older complex accretionary orogen (15561340 Ma), and a terminal microcontinent-continent collision oro-gen at 13401320 Ma.

3.6.1. Cachoeirinha Orogeny (15601520 Ma)The Cachoeirinha accretionary orogen was formed in a conver-

gent continental margin, resulting in a juvenile magmatic arc. Thisarc results from calc-alkaline magmatism, which is represented by

the syn- to late-kinematic Santa Cruz Intrusive Suite and late- topost-kinematic Alvorada Intrusive Suite (Fig. 6a).

3.6.2. Santa Helena Orogeny (14801420 Ma)This orogeny was characterized by the development of the San-

ta Helena accretionary orogen, considered by Geraldes et al. (2001)andRuiz (2005), as an Andean-type magmatic arc. This orogen islargely represented by syn-kinematic intrusions, the Santa HelenaIntrusive Suite and gua Clara Intrusive Suite (1.441.42 Ga), andthe Pindaiatuba Intrusive Suite (1.461.42 Ga). Post-kinematicand/or anorogenic plutons include the 1.42 Ga rapakivi granitesand related mafic rocks of the Rio Branco Intrusive Suite (Geraldeset al., 2001; Geraldes et al., 2004; Ruiz, 2005) (Fig. 6a).

3.6.3. Rio Alegre Orogeny (14401380 Ma)The development of the Rio Alegre accretionary orogen (1510

1380 Ma) comprises oceanic spreading (15101490 Ma), subduc-tion and soft-accretion stages (14401380 Ma) (Saes, 1999; Geral-des, 2000; Matos et al., 2004; Ruiz, 2005). The drift stage ischaracterized by the Rio Alegre Volcano-Sedimentary Unit andthe Maficultramafic Intrusive Suite (Matos, 1994; Matos et al.,2004; Ruiz, 2005). The orogenic stage (14801380 Ma) is recordedby oceanic lithosphere consumption during convergence in a prob-able intra-oceanic arc environment, accompanied by extensivetholeiitic and I-type calc-alkaline plutons and batholiths repre-sented by the Santa Rita Intrusive Suite (Fig. 6a). Subsequentsoft-collision was accompanied by N3050W tectonic vergenceunder greenschist facies conditions (Ruiz, 2005).

3.6.4. Rondonian-San Igncio Orogeny (13701320 Ma)Mesoproterozoic events at the time interval between 1500 and

1300 Ma are best recognized in Rondnia and eastern Bolivia andthe proposed time sequence is shown in Fig. 6b. The rift stage(15001387 Ma) was mainly characterized in Rondnia region bythe emplacement of A-type and intra-plate granites and associatedrocks of the Rio Crespo, Santo Antnio and Teotnio intrusivesuites. The drift stage (


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spatial organization of Sunss age structures in the SW AmazonianCraton is compatible with a transpressional left-lateral componentduring collision (Sadowski and Bettencourt, 1996; Teixeira et al.,2010), and extension components responsible for the insertion ofthe Neoproterozoic basins.

Acknowledgments

Careful reviews by U.G. Cordani and B. B. de Brito Neves areappreciated. Two other anonymous journal reviewers and GuestEditor Cesar Casquet are thanked for comments that much improvethe quality of the manuscript. Also we sincerely thank Thelma Col-lao Samara from the the IGc-USP for the drafts.

References

Arajo, L.M.B., 2008. Evoluo do Magmatismo Ps-Cinemtico do DomnioCachoeirinha: Sutes Intrusivas Rio Branco, Alvorada e Santa Cruz, SW doCrton Amaznico, MT. Ph.D. Thesis, So PauloState University, Rio Claro, Brazil(in Portuguese).

Barros, A.M., Silva, R.H., Cardoso, O.R.F.A., Freire, F.A., Souza Jr., J.J., da Rivetti, M.,Luz, D.S., Palmeira, R.C., Tassinari, C.C.G.,1982. Geologia. In: Ministrio dasMinase Energia. Projeto RADAMBRASIL, Folha SD.21. Cuiab. Riode Janeiro, 544p. In: Levantamentos de Recursos Naturais, vol. 26, pp. 25192.

Berrang, J.P., Litherland, M., 1982. Sinopss de la geologia y potencial de mineralesdel area del Proyecto Precambrico. Boletin del Servicio Geolgico de Bolivia,Informe 21, 120.

Bettencourt, J.S., Leite, W.B., Payolla, B.L., Scandolara, J.E., Muzzolon, R., Vian, J.A.J.,1997. The rapakivi granites of the Rondnia Tin Province, Northern Brazil. In:2nd International Symposium on Granites and Associated Mineralizations,Excursion Guide. Salvador, Bahia, Brazil, pp. 331

Bettencourt, J.S., Tosdal, R.M., Leite Jr, W.B., Payolla, B.L., 1999. Mesoproterozoicrapakivi granites of the Rondnia Tin Province, southwestern border of theAmazonian Craton, BrazilI. Reconnaissance UPb geochronology and regionalimplications. Precambrian Research 95, 4167.

Bettencourt, J.S., Payolla, B.L., Tosdal, R.M.; Wooden, J.L., Leite, W.B., Sparrenberger,I., 2006. SHRIMP-RG UPb zircon geochronology of gneiss from the Rio CrespoIntrusive Suite, SW Amazonian Craton, Rondnia, Brazil: new insight aboutprotolith crystallization and metamorphic ages. In: 5th South AmericanSymposium on Isotopic Geology, Short Papers, Punta del Este, Uruguay, pp.4952.

Boger, S.D., Raetz, M., Giles, D., Etchart, E., Fanning, M.C., 2005. UPb age data fromthe Sunsas region of Eastern Bolivia, evidence for the allochtonous origin of theParagu Block. Precambrian Research 139, 121146.

Carneiro, M.A., 1985. Contribuio geologia da regio de So Jos dos QuatroMarcos-MT. M.Sc. Dissertation, University of So Paulo

bettencourt el al. 2010

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