A Província Aurífera Tapajós-Xingu: Avanços no ... - ADIMB

A Província Aurífera Tapajós-Xingu: Avanços noConhecimento Geológico-MetalogenéticoCaetano Juliani (USP)Instituto de Geociências – USPInstituto Nacional de Ciências e Tecnologia da Amazônia – INCT-GEOCIAMSIMEXMIN – 2012Ouro Preto

These rocks cover more than1.100.000 km 2

THE UATUMÃ MAGMATISMIncludes calc-alkaline and alkaline granites and volcanic rocks with agesranging from ~2,0 to 1,75 Ga.These unit covers more than 1.200.000 km 2 (Santos et al. 2000), which isapproximately 30% of the Amazonian craton, excluding the PhanerozoicAmazon River basin.The original volcanic area could have reached 2.000.000 km 2Many areas where volcanic rocks outcrop are not identified in geologicmaps, even in more recent workThe largest felsic province of the world

THE UATUMÃ SUPERGRUP INCLUDES:Alkaline A type granites named Maloquinha Intrusive Suite in the Tapajós(Almeida et al. 1977, Andrade et al. 1978), Mapuera at north of Rio Amazonasbasin (Oliveira et al. 1975) and Velho Guilherme Intrusive Suite in the Xinguregion (Macambira & Vale 1997).However, the calc-alkaline affiliation of the basal volcanic units of theUatumã doesn’t favour such interpretation. Thus, the Uatumã volcanismgenerated in an continental magmatic arc may be likely related to the Parauariplutonism. But, outher older and younger calc-alkaline could be present inTapajós – Xingu orogenic beltThe type A granites possibly are genetically related with the alkaline volcanicunit.THIS IMPLIES IN AT LEAST TWO PALEOPROTEROZOIC VOLCANIC SEQUENCES:CALK-ALKALINE (LOWER) AND A-TYPE ALKALINE (UPPER)

1.9 – 1.86 MAGMATIC-HYDROTHERMAL MINERALIZATION IN UATUMÃ EVENT

Geologic map of the Tapajós Gold Province (simplified from CPRM, 2000)

Schematic stratigraphy of the Tapajós Gold Province (Juliani et al., 2003)

Caldera complexes, high- and low-sulfidation mineralization, and associatedporphyry-type mineralization in the Tapajós Gold ProvinceHS Au mineralizationLS and porphyry Cu-Mo-(Au)Volcanic caldera complexes

Au high-sulfidationmineralizationCu-Mo-(Au) low-sulfidationoverprinted by a porphyry typemineralizationPaleoproterozoic arkoses and arenitesHS mineralization

Hydrothermal alteration in the volcanic rocks in the highsulfidationmineralizationa) Silicification and hematitizationMassive and vuggy silica with microcrystalline quartz and minor sulfides partially or totally replacedby hematite, pyrophylite, alunite and relicts of feldsparsb) Advanced argillic alteration with alunite and quartzAlunite + natroalunite + andalusite + corindon + pyrophyllite + quartz + rutile +woodhousenite-svambergite + hindaslite + topaz + famatinite + tetraedrite–tennantite + tiemannita+ barite + pyrite + chalcopyrite + bornite + covellite + galena + sphalerite + enargite-luzonite +aguilarite + clorargirite + native copper, silver and goldc) Advanced argillic alterationPyrophyllite + quartz + pyrite + andalusite + diaspore + rutile + woodhousenitesvanbergite+ tourmaline + fluorite + hematited) Intermediate argillic alterationkaolinite + dickite + sericite + chlorite + feldspar relictse) Sericitic alterationSericite + quartz + zeolite + clay-minerals + sulfidesf) Propylitic alterationEpidote + clinozoisite + chlorite + actinolite + albite + zeolite + carbonate + sulfides

Schematic cross-section of the high-sulfidation mineralization (Juliani et al., 2005)

Hematite-rich silica cap (vuggysilica):complete leaching of ignimbrites,rhyolites and hydrothermalbreccias, which are cut by smallhydrothermal breccia dikes

AluniteJuliani et al. (2005)Paleoproterozoic highsulfidationmineralization in theTapajós Gold Province,Amazonian Craton,Brazil: Geology,mineralogy, aluniteargon age and stableisotope constraints.Chemical Geology,215: 95–125

Juliani et al. (2005)

Pyrite sulfur isotopeTapajós HS: – 6.3 to + 1.7Tap. Au-bearing vein: + 4.4El Indio: – 4.9 to –1.8Noble gases indicate mantlesource for the magmaticfluidsLandis et al. (2005)

Age of the Alunite of HS mineralizationJuliani et al. (2005)

The low-sulfidation (adularia-sericite)evolved to intermediate-sulfidation and Cu-Mo-(Au) porphyry mineralization overprint

Hydrothermal alteration in the volcanic rocks associatedwith the low-sulfidation mineralizationa) Sericitic alteration with adulariaSericite + quartz + adularia + pyrite + chalcopyrite + molybdenite + Femolybdenite+ anilite + chalcocite + covelite + sphalerite + gold + rutile +titaniteb) Propylitic alteration with adulariaChlorite + carbonate + epidote + fluorite + albite + adularia+ chalcopyrite + pyrite + quartz + leucoxene + rutile + baritec) Argillic alterationKaolinite + chalcedony + allophane + microcrystaline quartz + hematited) Sericitic alteration in shear zonesSericite + quartz + sulfides, without adularia

Stratigraphy of volcanicrocks and porphyry dikesin the drill holes in thelow-sulfidationmineralizationPorphyry dikes

Adularia-sericite hydrothermalalterationEPITHERMAL LOW-SULFIDATIONMINERALIZATIONOVERPRINT OF Cu-Mo PORPHYRYSTYLE MINERALIZATIONChalcopyrite and molybdenite insericitic zones in K-metasomatizedporphyry dikes

Rhyolites strongly affected by adularia-sericitic alteration and silicificationPlaty calcite replaced by chalcedony

K-metasomatized and propylitized porphyry dikes associated with LSM

Quartz and sulfide veins in strongly altered rhyolitesLater sericitic alteration and silicification in K-metasomatized and propylitized porphyry dikesassociated with LSM

Sericitic alteration with adularia in rhyolitesPlaty cacite replaced by chalcedonyMolybdenitePyrite and chalcopyrite

Xingu areaLagler (2011)Juliani & Fernandes (2010)

Volcanic agglomeratesVolcanic breccias (clasts of tuffs)Lapilli tuffsCrystal- and welded tuffs

Ash tuffSpherulitesMarine calciarenites with evaporite (?) layers

De La Roche et al. (1980)

Tapajós - XinguPearce et al. (1984)

Not all rocks interpreted as A-type volcanic rocks in thesouth part of Amazonian craton are A-type!!!!(La/Yb) N ~ 4, baixo LILE/HFS.(La/Yb) N ~ 12, alto LILE/HFS.(La/Yb) N ~ 12, alto LILE/HFS.(La/Yb) N ~ 13, alto LILE/HFS.Lagler (2011)

The Palito Granite1.89 Ga Au-(Cu) porphyry(~ 650.000 oz Au eq.)

Porphyry-like deep emplaced Au granitePossible flat subduction event and Xingu volcanism

GEOCHEMISTRYHarris et al. (1986) Schandl & Gorton (2002)

Palito mine geologyN1 km

Palito Alkali-calcic g ran ite(a d o m ic in tru sio n ? )Au -Cu m ain vein sF o fo q u in h a g ran o d io ritean d q u artz d io riteM afic d ikesSeco n d ary Au -Cu m ain vein san d sto ckw o rksRio No vo g ran iteM ag n etite g ran itePo rp h yry d ikes- Mafic dikes appear to be coeval with Au-Cu mineralization- Some porphyry dikes post-date gold and copper mineralization- Brittle faults cut orebodies

Hydrothermal alteration in the Palito granite and granites,porphyry (stocks and dikes) associated to epithermalmineralizationa) Na-metasomatism (more abundat in Batalha Granite, local inepizonal porphyries and granophyries)Albite + quartz + fluoriteb) K-metasomatismMicrocline + biotite + quartzc) Propylitic alterationEpidote + clinozoisite + chlorite + albite + carbonates + quartz + sericite +sulfides + leucoxene + biotite + fluorite + apatite + titanited) Sericitic alterationQuartz + amethyst + sericite + pyrite + chalcopyrite + molybdenite galena +fluorite + pyrophyllite + clay minerals + gold + prehnite pumpellyite + zeolites

CpyGa + SpCpyGa + Sp + Cpy

Massive sulfide vein with chalcopyrite + chalcocite + bismuthinite +native bismuth + Bi-sulphosalts + gold (up to 2500 ppm – average ~15 ppm)

Mineral Chemical formula Mineral Chemical formulaChalcopyrite CuFeS 2 Wittichenite Cu 3 BiS 3Chalcocite Cu 2 S Hedleyita Bi 7 Te 3Pyrite FeS 2 Cuprobismuthinite Cu 10 Bi 12 S 23MineralFórmula químicaCalcopirita CuFeS 2CalcocitaCu 2 SPirita FeS 2PirrotitaFeSGalenaPbSEsfaleritaZnSOuroAuElectrumAu-AgBarita BaSO 4ArgentocuproauridaCu 3 (Au,Ag)Bismuto nativoBiBismutinita Bi 2 S 3Makovickyita Ag 1 , 5 Bi 5,5 S 9Wittichenita Cu 3 BiS 3Hedleyita Bi 7 Te 3Pyrrhotite FeS Kupcikite (Cu,Fe) 4 Bi 6 S 10Galena PbS Bi-Te selenide Bi 4 Te 2 SeSphalerite ZnS Ag-Te-Bi telluride Ag 16 FeBiTe 3 S 8Gold Au Matildite AgBiS 2 (Fe,Cu)Electrum Au-Ag Tetradymite Bi 2 Te 3 SBarite BaSO 4 Scheelite Ca(WO 4 )Argentocuproauride Cu 3 (Au,Ag) Ytrialite (Y,Th) 2 SiO 7Bismuth Bi Monazite (Ce,La,Nd,Th)PO 4Bismuthinite Bi 2 S 3 Thorite ThSiO 4Makovickyite Ag 1 , 5 Bi 5,5 S 9 Pilsenite Bi 4 Te 3

Echeverri-Misas (2010)Biotite

Hydrogen Isotopic compositionMineralδD mineral(‰ SMOW)δD fluid(‰ SMOW)(350 ºC)Chlorite - 119 ‰ - 55,4 ‰Sericite - 74 a - 38 ‰ - 36,2 a – 0,2‰Oxygen Isotopic compositionMineralδ 18 O mineral(‰ SMOW)δ 18 O fluid(‰ SMOW)(450 ºC)Quartz 8,8 a 11,2 ‰ 5,1 a 7,5 ‰K Feldspar 7,9 a 8,8 ‰ 6,3 a 7,2 ‰Sericite 1,7 a 6,9 ‰ 1,1 a 6,3 ‰Chlorite(350 ºC)- 2,4 ‰ 1,6 ‰Calcite(350 ºC)9,0 a 23,9 ‰ 6,2 a 21,1‰

SULFUR ISOTOPICCOMPOSITIONMineralδ 34 SPyrite 2,4 a 3,6 ‰Chalcopyrite 2,2 a 3,6 ‰Galena 1,2 ‰

FLUID INCLUSION STUDYUsero et al. (2009)‣ The fluids were exsolved from magmas‣ Evidences of boiling at 350 o C and continousboiling in lower temperatures‣ Fluid mixing, probably with meteoric water, isobserved‣ The salinity ranges from low to ~29% eq. NaCl inAu-Cu quartz veins‣ Melt inclusions are also present‣ Opaque minerals in IFs appears to be Cpy

PhanerozoicbasinHS mineralization

Fig. 2.5 Reconstruction of cratons and orogenic belts (green) at 1.88 Ga. The Archean cratons are shown in gray.Data available from Laurentia (L), Baltica (B), Amazonia (Am), Siberia (S), Australia (A) and Kalahari (K). The ca.1.90–1.80 Ga orogenic belts are shown in dark green and they are: in Laurentia Nagssugtoqidian (N), Ketilidian(K), Torngat (T), Trans-Hudson (TH), Penokean (P), Woopmay (W), and Taltson-Thelon (T-T); in Baltica Lapland-Kola(L-K) and Svecofennian (Sv); in Amazonia Ventuari-Tapajos (V-T); in Siberia Akitkan (A); in Australia Capricorn (C);and in Kalahari Limpopo (L). Mertanen and Pesonen (2012)

Geologic environment in the Paleoproterozoic of the TGP, suggesting also possible VHMS,SEDEX and reefs gold mineralizations.

Carneiro et al. – See the poster exposed today for more detail.

Tassinari & Macambira (1999) Santos et al. (2000)

Volcanic coverANP

At least 2magmatic arcs ?ANPJuruena belt – 1,75 Ga

LS + Por(Cu+Mo+(Au)HS (Au)??Por (Au+(Cu))???Carajás?

Are the Tapajósprovince and Tapajós– Xingu belt a goldonlyprovince?

AcknowlegmentsWe are greatly indebted to:• Serviço Geológico do Brasil – CPRM for the geophysical data• ADIMB and Prof. Onildo Marini