The sequence of magmatic and mineralization events in the Abitibi greenstone belt: isotopic evidence from Taylor Township, Timmins area, northern Ontario, Canada

1995 ◽  
Vol 32 (8) ◽  
pp. 1221-1235 ◽  
Author(s):  
J. M. Worden ◽  
G. L. Cumming ◽  
D. Krstic
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Pb Isotope ◽  
Northern Ontario ◽  
Abitibi Greenstone Belt ◽  
Igneous Activity ◽  
The Difference ◽  
A Minor ◽  
Hydrothermal Event

Samples from the Porphyry deposit and the Shoot zone prospect of St. Andrew Goldfields Ltd. in Taylor Township near Matheson, Ontario, have been dated by several different techniques and utilized as a test of the use of Pb-isotope measurements in determining the time of mineralization in gold deposits of the Abitibi greenstone Belt. Clear and abraded zircons from an altered "sulfidic porphyry" unit yield a well-defined age of 2697.3 ± 1.3 Ma, indicating that the original intrusive rock unit containing these zircons was either latest synvolcanic or earliest syntectonic. Larger "bulk" samples of zircon from the same unit contain many altered and cracked grains, and yield an age of 2682 ± 4 Ma, close to the peak of syntectonic igneous activity. Pb/Pb isochrons determined from sulfide samples in mineralized material from the Taylor "porphyry zone" yield a two-stage model age of 2663 ± 17 Ma, and suggest that mineralization postdates the syntectonic granitoids. These Pb-isotope data are compared with isotope ratios determined on samples from the Dome mine. For these latter samples, the isotopic ratios indicate that an earlier mineralization event was reset at 2266 ± 49 Ma, suggesting to us that the sulfides, and hence gold mineralization, were remobilized at this later time. It is proposed that this remobilization is responsible for a significant benefaction of the gold ore and may make the difference between a mineable orebody and an uneconomic prospect. This time of remobilization corresponds well with some Rb/Sr dates in the Abitibi Province and may represent a previously unrecognized, but significant hydrothermal event. Rb/Sr ages on volcanic units yield ages of 2520–2580 Ma, consistent with similar ages in the surrounding area. They may represent cooling following a thermal event associated with the intrusion of the latest granitic plutons. A minor hydrothermal event at ~1600 Ma seems to have reset the Rb/Sr system in some micas and affected some pyrite samples, resulting in the formation of late carbonate and hematite.

Geology, lithogeochemistry, and significance of porphyry intrusions associated with gold mineralization within the Timmins–Porcupine gold camp, Canada

2019 ◽  
Vol 56 (4) ◽  
pp. 399-418 ◽  
Author(s):  
Peter J. MacDonald ◽  
Stephen J. Piercey
Keyword(s):  
Partial Melting ◽  
Greenstone Belt ◽  
Deformation Zone ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Crustal Thickening ◽  
Abitibi Greenstone Belt ◽  
Crustal Structures ◽  
Intrusive Rocks ◽  
Intrusive Suite

The Timmins–Porcupine gold camp, Abitibi greenstone belt, is host >60 Moz of Au with many gold deposits spatially associated with porphyry intrusions and the Porcupine–Destor deformation zone (PDDZ). Porphyry intrusions form three suites. The Timmins porphyry suite (TIS) consists of high-Al tonalite–trondjhemite–granodiorite (TTG) with calc–alkalic affinities and high La/Yb ratios and formed during ∼2690 Ma D1-related crustal thickening and hydrous partial melting of mafic crust where garnet and hornblende were stable in the residue. The Carr Township porphyry intrusive suite (CIS) and the granodiorite intrusive suite (GIS) also have high-Al TTG, calc-alkalic affinities, but were generated 10–15 million years after the TIS; the CIS were generated at shallower depths (during postorogenic extension?) with no garnet in the crustal residue, whereas the GIS formed during D2 thrust-related crustal thickening and partial melting where garnet was stable in the residue. Gold mineralization is preferentially associated with the TIS, and to a lesser extent the GIS, proximal to the PDDZ. Intrusions near mineralization have abundant sericite, carbonate, and sulphide alteration. These intrusions exhibit low Na2O and Sr, and high Al2O3/Na2O, K2O, K2O/Na2O, Rb, and Cs, (i.e., potassic alteration); sulfide- and carbonate-altered porphyries have high (CaO + MgO + Fe2O3)/Al2O3 and LOI values. Although porphyries are not genetically related to gold mineralization, they are spatially related and are interpreted to reflect the emplacement of intrusions and subsequent Au-bearing fluids along the same crustal structures. The intrusive rocks also served as structural traps, where gold mineralization precipitated in dilatant structures along the margins of intrusions during regional (D3?) deformation.

Chapter 8: The World-Class Gold Deposits in the Geita Greenstone Belt, Northwestern Tanzania

2020 ◽  
pp. 163-183
Author(s):  
P.H.G.M. Dirks ◽  
I. V. Sanislav ◽  
M. R. van Ryt ◽  
J.-M. Huizenga ◽  
T. G. Blenkinsop ◽  
...  
Keyword(s):  
Greenstone Belt ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Normal Faulting ◽  
Rock Interaction ◽  
Northwestern Tanzania ◽  
The Matrix ◽  
Igneous Activity ◽  
History Of ◽  
Gold Bearing

Abstract The Geita mine is operated by AngloGold Ashanti and currently comprises four gold deposits mined as open pits and underground operations in the Geita greenstone belt, Tanzania. The mine produces ~0.5 Moz of gold a year and has produced ~8.3 Moz since 2000, with current resources estimated at ~6.5 Moz, using a lower cut-off of 0.5 g/t. The geologic history of the Geita greenstone belt involved three tectonic stages: (I) early (2820–2700 Ma) extension (D1) and formation of the greenstone sequence in an oceanic plateau environment; (II) shortening of the greenstone sequence (2700–2660 Ma) involving ductile folding (D2–5) and brittle-ductile shearing (D6), coincident with long-lived igneous activity concentrated in five intrusive centers; and (III) renewed extension (2660–2620 Ma) involving strike-slip and normal faulting (D7–8), basin formation, and potassic magmatism. Major gold deposits in the Geita greenstone belt formed late in the history of the greenstone belt, during D8 normal faulting at ~2640 Ma, and the structural framework, mineral paragenesis, and timing of gold precipitation is essentially the same in all major deposits. Gold is hosted in iron-rich lithologies along contacts between folded metaironstone beds and tonalite-trondhjemite-granodiorite (TTG) intrusions, particularly where the contacts were sheared and fractured during D6–7 faulting. The faults, together with damage zones created along D3 fold hinges and D2–3 hydrothermal breccia zones near intrusions, formed microfracture networks that were reactivated during D8. The fracture networks served as conduits for gold-bearing fluids; i.e., lithologies and structures that trap gold formed early, but gold was introduced late. Fluids carried gold as Au bisulfide complexes and interacted with Fe-rich wall rocks to precipitate gold. Fluid-rock interaction and mineralization were enhanced as a result of D8 extension, and localized hydrofracturing formed high-grade breccia ores. Gold is contained in electrum and gold-bearing tellurides that occur in the matrix and as inclusions in pyrrhotite and pyrite. The gold mineralization is spatially linked to long-lived, near-stationary intrusive centers. Critical factors in forming the deposits include the (syn-D2–6) formation of damage zones in lithologies that enhance gold precipitation (Fe-rich lithologies); late tectonic reactivation of the damage zones during extensional (D8) faulting with the introduction of an S-rich, gold-bearing fluid; and efficient fluid-rock interaction in zones that were structurally well prepared.

scholarly journals Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 966
Author(s):  
Baptiste Madon ◽  
Lucie Mathieu ◽  
Jeffrey H. Marsh
Keyword(s):  
Oxygen Fugacity ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Chemical Diversity ◽  
Temporal Association ◽  
Volatile Content ◽  
Abitibi Subprovince

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

Nd and Pb isotope ratios of the Abitibi greenstone belt: new evidence for very early differentiation of the Earth

1994 ◽  
Vol 128 (3-4) ◽  
pp. 215-229 ◽  
Author(s):  
Jeffrey D. Vervoort ◽  
William M. White ◽  
Ralph I. Thorpe
Keyword(s):  
Greenstone Belt ◽  
Isotope Ratios ◽  
Pb Isotope ◽  
Early Differentiation ◽  
Abitibi Greenstone Belt ◽  
The Earth ◽  
New Evidence

Postmagmatic thermal activity in the Abitibi greenstone belt, Noranda and Matagami districts; evidence from whole-rock Pb isotope data

1993 ◽  
Vol 88 (6) ◽  
pp. 1598-1614 ◽  
Author(s):  
J. D. Vervoort ◽  
W. M. White ◽  
R. I. Thorpe ◽  
J. M. Franklin
Keyword(s):  
Greenstone Belt ◽  
Thermal Activity ◽  
Pb Isotope ◽  
Abitibi Greenstone Belt ◽  
Isotope Data

Laser ablation ICP MS trace element composition of native gold from the Abitibi Greenstone belt, Timmins Ontario.

2021 ◽  
Author(s):  
John D. Greenough ◽  
Alejandro Velasquez ◽  
Mohamed Shaheen ◽  
Joel Gagnon ◽  
Brian J. Fryer ◽  
...  
Keyword(s):  
Trace Elements ◽  
Laser Ablation ◽  
Trace Element ◽  
Greenstone Belt ◽  
Native Gold ◽  
Internal Standard ◽  
Gold Deposits ◽  
Ore Deposits ◽  
Abitibi Greenstone Belt ◽  
Icp Ms

Trace elements in native gold provide a “fingerprint” that tends to be unique to individual gold deposits. Fingerprinting can distinguish gold sources and potentially yield insights into geochemical processes operating during gold deposit formation. Native gold grains come from three historical gold ore deposits; Hollinger, McIntyre (quartz-vein ore), and Aunor near Timmins, Ontario, at the western end of the Porcupine gold camp and the south-western part of the Abitibi greenstone belt. Laser-ablation, inductively-coupled plasma mass spectrometry (LA ICP MS) trace element concentrations were determined on 20 to 25 µm wide, 300 µm long rastor trails in ~ 60 native gold grains. Analyses used Ag as an internal standard with Ag and Au determined by a scanning electron microscope with an energy dispersive spectrometer. The London Bullion Market AuRM2 reference material served as the external standard for 21 trace element analytes (Al, As, Bi, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Pd, Pt, Rh, Sb, Se, Si, Sn, Te, Ti, Zn; Se generally below detection in samples). Trace elements in native gold associate according to Goldschmidt’s classification of elements strongly suggesting that element behavior in native Au is not random. Such element behavior suggests that samples from each Timmins deposit formed under similar but slightly variable geochemical conditions. Chalcophile and siderophile elements provide the most compelling fingerprints of the three ore deposits and appear to be mostly in solid solution in Au. Lithophile elements are not very useful for distinguishing these deposits and element ABSTRACT CUT OFF BY SOFTWARE

Gold Remobilization: Insights from Gold Deposits in the Archean Swayze Greenstone Belt, Abitibi Subprovince, Canada

2020 ◽  
Vol 115 (2) ◽  
pp. 241-277 ◽  
Author(s):  
Evan C.G. Hastie ◽  
Daniel J. Kontak ◽  
Bruno Lafrance
Keyword(s):  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Native Gold ◽  
Gold Deposits ◽  
Coarse Grained ◽  
High Grade ◽  
Northern Ontario ◽  
Inductively Coupled ◽  
Abitibi Subprovince ◽  
Plasma Mass Spectrometry

Abstract Recognizing if and how Au is remobilized, in solid, melt, or fluid state, is critical for understanding the origin of high-grade ore zones in Au deposits. When evidence for Au remobilization can be demonstrated, then primary versus secondary processes can be distinguished, resulting in a more complete understanding of Au deposit formation. To address this, samples from two Au deposits, Jerome and Kenty, in the Archean Swayze greenstone belt of northern Ontario, Canada, together with archived samples from 39 high-grade Au deposits from the Abitibi greenstone belt across Ontario and Quebec, were geochemically characterized using integrated scanning electron microscopy-energy dispersive spectroscopy and electron microprobe imaging and analyses in addition to laser ablation-inductively coupled plasma-mass spectrometry elemental mapping. These data provided the basis to develop a model for Au remobilization and upgrading of Au that is widely applicable to orogenic gold settings. Data for the Jerome deposit indicate that Au uptake into early pyrite was not due to pulsing of different fluids, but instead was predominantly controlled by S availability, whereby the oscillatory/sector zoning in pyrite resulted from the substitution of As into S sites during rapid growth due to local chemical disequilibrium. In addition, Au-bearing pyrite from both the Jerome and Kenty deposits records textures, such as porosity development coincident with the presence of native gold and accessory sulfide phases, that are strongly suggestive of coupled dissolution-reprecipitation (CDR) reactions that liberated Au and associated elements from earlier auriferous (100–5,000 ppm Au) pyrite. During the remobilization process, Au and Ag were decoupled, which resulted in (1) a change in Au/Ag ratios of 0.5 to 5 in early pyrite to ≈9 in the new native gold (900 Au fineness) and (2) incorporation of Ag into cogenetic secondary mineral phases (e.g., chalcopyrite, tetrahedrite, and galena). Evidence for an association of low-melting point chalcophile elements (LMCE; Hg, Te, Sb, and Bi) with Au at the Jerome, Kenty, and many (>50%) of the 39 historic deposits sampled, along with native gold filling structurally favorable sites in vein quartz in all samples, indicates a fluid might not have been the only factor contributing to remobilization. This systematic Au-LMCE association strongly supports a model whereby Au is released by CDR reactions and is then remobilized by fluid-mediated, LMCE-rich melts that began to form at 335°C and/or by local, nanoparticle (nanomelt?) transport during deformation and metamorphism. Conclusions drawn from this study have implications for Au deposits globally and can account for the common presence of coarse-grained, commonly crystalline, native gold filling fractures in quartz and the paragenetically late-stage origin of gold in veins. They can also better explain the inability of Au in solution remobilization models to account for locally high gold grades, given the relatively low solubility of Au in hydrothermal fluids.

Fractionation of the platinum-group elements and gold in some komatiites of the Abitibi greenstone belt, northern Ontario

1987 ◽  
Vol 82 (1) ◽  
pp. 165-183 ◽  
Author(s):  
Sarah-Jane Barnes ◽  
Anthony J. Naldrett
Keyword(s):  
Greenstone Belt ◽  
Platinum Group Elements ◽  
Northern Ontario ◽  
Abitibi Greenstone Belt ◽  
Platinum Group
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