Geology of the Hammer Down mesothermal gold deposit, Newfoundland Appalachians, Canada

1996 ◽  
Vol 33 (2) ◽  
pp. 335-350 ◽  
Author(s):  
Damien Gaboury ◽  
Benoît Dubé ◽  
Marc R. Laflèche ◽  
Kathleen Lauzière
Keyword(s):  
Gold Deposit ◽  
High Strain ◽  
Volcanic Rocks ◽  
Gold Deposits ◽  
Quartz Veins ◽  
Younger Age ◽  
Two Generations ◽  
Brittle Faulting ◽  
Host Rocks ◽  
Actual Geometry

The Hammer Down gold deposit is one of the most significant mesothermal vein-type gold deposits in the Canadian Appalachians. It is located within a complex sequence of Ordovician, mafic-dominated tholeiitic and calc-alkalic and arc-related volcanic rocks, which was intruded by Silurian felsic porphyry dykes. The host rocks have undergone complex polyphase deformation. At least three deformational events influenced vein emplacement and overall geometry of the deposit. A Taconian deformation (D1–2) was responsible for the development of a 250 m wide zone of high-strain deformation (HSZ1) at the interface between two blocks of Ordovician rocks: the Catcher's Pond Group and the Lush's Bight Group. Rocks included within the HSZ1, represent "exotic" slabs of volcanic rocks that were tectonically juxtaposed, intensively foliated (S1), and folded (F2). Gold occurs in high-grade, sulfide-rich, fault-fill quartz veins that occur within the HSZ1. At the outcrop scale, these veins are hosted by discrete centimetre- to metre-wide ductile–brittle D3 high-strain zones (HSZ3) of Silurian or younger age. The development of the gold-hosting structures (HSZ3) is genetically related to layer anisotropy induced by intrafolial F2 folds, and most importantly by the presence of felsic porphyry dykes, which were competent compared to the intensively foliated and incompetent mafic volcanic rock sequence. A postmineralization D4–5 deformation, which included two generations of folds (F4 and F5) and late brittle faulting, is responsible for the actual geometry of the deposit.

scholarly journals Amethyst Occurrences in Tertiary Volcanic Rocks of Greece: Mineralogical, Fluid Inclusion and Oxygen Isotope Constraints on Their Genesis

Minerals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 324 ◽  
Author(s):  
Panagiotis Voudouris ◽  
Vasilios Melfos ◽  
Constantinos Mavrogonatos ◽  
Alexandre Tarantola ◽  
Jens Gӧtze ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Open System ◽  
Volcanic Rocks ◽  
Hydrothermal Fluids ◽  
Northern Greece ◽  
Quartz Veins ◽  
Low Salinity ◽  
Moderate Salinity ◽  
Host Rocks ◽  
Of Greece

Epithermally altered volcanic rocks in Greece host amethyst-bearing veins in association with various silicates, carbonates, oxides and sulfides. Host rocks are Oligocene to Pleistocene calc-alkaline to shoshonitic lavas and pyroclastics of intermediate to acidic composition. The veins are integral parts of high to intermediate sulfidation epithermal mineralized centers in northern Greece (e.g., Kassiteres–Sapes, Kirki, Kornofolia/Soufli, Lesvos Island) and on Milos Island. Colloform–crustiform banding with alternations of amethyst, chalcedony and/or carbonates is a common characteristic of the studied amethyst-bearing veins. Hydrothermal alteration around the quartz veins includes sericitic, K-feldspar (adularia), propylitic and zeolitic types. Precipitation of amethyst took place from near-neutral to alkaline fluids, as indicated by the presence of various amounts of gangue adularia, calcite, zeolites, chlorite and smectite. Fluid inclusion data suggest that the studied amethyst was formed by hydrothermal fluids with relatively low temperatures (~200–250 °C) and low to moderate salinity (1–8 wt % NaCl equiv). A fluid cooling gradually from the external to the inner parts of the veins, possibly with subsequent boiling in an open system, is considered for the amethysts of Silver Hill in Sapes and Kassiteres. Amethysts from Kornofolia, Megala Therma, Kalogries and Chondro Vouno were formed by mixing of moderately saline hydrothermal fluids with low-salinity fluids at relatively lower temperatures indicating the presence of dilution processes and probably boiling in an open system. Stable isotope data point to mixing between magmatic and marine (and/or meteoric) waters and are consistent with the oxidizing conditions required for amethyst formation.

Metallogeny of the Marco zone, Corvet Est, disseminated gold deposit, James Bay, Quebec, Canada

2012 ◽  
Vol 49 (10) ◽  
pp. 1154-1176
Author(s):  
Martin Aucoin ◽  
Georges Beaudoin ◽  
Robert A. Creaser ◽  
Paul Archer
Keyword(s):  
Gold Deposit ◽  
Basaltic Andesite ◽  
Native Gold ◽  
Gold Mineralization ◽  
Isotope Composition ◽  
Hanging Wall ◽  
Volcanic Rocks ◽  
Weighted Average ◽  
James Bay ◽  
Host Rocks

The Corvet Est gold deposit is hosted by Archean rocks of the Superior Province in the James Bay region, northern Quebec, Canada. The Marco zone is hosted by amphibolite-grade, strongly foliated volcanic rocks and consists of disseminated gold, with an apparent thickness ranging from 1.8 to 39.5 m and gold grades up to 23 g·t–1 over 1 m, that is continuous along strike for ∼1.3 km. The lithotectonic sequence comprises footwall basaltic andesite amphibolite overlain by a lenticular unit of metadacite and then by hanging-wall basaltic andesite amphibolite, all intruded by quartz–feldspar porphyry dikes. Dacite, basaltic andesite amphibolite, and quartz–feldspar porphyry show a calc-alkaline to transitional affinity and plot in the plate margin arc basalt field, with typical volcanic arc trace element patterns. Mineralization consists of pyrite, arsenopyrite, pyrrhotite, chalcopyrite, and gold, disseminated in deformed dacite, in andesite amphibolite, and in quartz–feldspar porphyry dikes. Dacite and andesite display weak alteration characterized by silicification. Native gold forms inclusions in metamorphic quartz, garnet, feldspar, arsenopyrite, and pyrite or free grains interstitial to quartz, feldspar, pyrite, chalcopyrite, and arsenopyrite. Free gold in late quartz veins cut the sericitized metamorphic fabric. Inclusion and interstitial native gold within minerals annealed during metamorphism shows that gold mineralization is pre- to syn-metamorphic, with some gold remobilized in later veins. Rhenium–osmium dating of arsenopyrite yields an isochron age of 2663 ± 13 Ma for mineralization and a weighted average model age of 2632 ± 7 Ma for arsenopyrite formed during peak metamorphism. The ∼2663 Ma arsenopyrite has a low initial 187Os/188Os of 0.19 ± 0.10, suggesting a juvenile crust or a mantle Os source. The sulfur isotope composition of Marco zone pyrite and arsenopyrite shows that sulfur could have been leached from its volcanic host rocks or from reduction of Archean seawater. The Corvet Est deposit is interpreted to be an orogenic gold deposit (2663 Ma) deformed and recrystallized during amphibolite-grade metamorphism (2632 Ma).

scholarly journals Tourmaline from Late Quartz Veins of the Murtykty Gold Deposit, Republic of Bashkortostan

2020 ◽  
Vol 6 (1) ◽  
pp. 69-83
Author(s):  
M.A. Rassomakhin ◽  
E.V. Belogub ◽  
K.A. Novoselov ◽  
P.V. Khvorov
Keyword(s):  
Gold Deposit ◽  
Sedimentary Rocks ◽  
Gold Deposits ◽  
Sulfide Mineralization ◽  
Porphyry Deposits ◽  
Quartz Veins ◽  
Orogenic Gold Deposits ◽  
Eastern Zone ◽  
Republic Of Bashkortostan ◽  
Intermediate Member

Tourmaline, an intermediate member of the oxyschorl–oxydravite–oxymagnesio-foitite-bosiite series with a predominance of the oxy-dravite-bosiite end-member, was studied from late calcite-quartz veins in the eastern zone of the Murtykty gold deposit (Republic of Bashkortostan). Sulfide mineralization in veins includes rare chalcopyrite, pyrite, sphalerite and galena. Accessory minerals are xenotime-(Y), vanadium-containing rutile and fine high-fineness gold. Supergene mineralization resulted from decomposition of carbonates, sulfides and rock-forming silicates includes kaolinite, hydroxides of Mn (chalcophanite, psilomelane) and Fe (goethite and limonite ochers), mainly developed in vein cavities ; chalcopyrite is replaced by cuprite and malachite. The composition of tourmaline is close to metamorphic dravite of orogenic gold deposits and tourmaline of gold-porphyry deposits, transitioning from porphyry to epithermal. Two possible B sources for the formation of tourmaline are considered: sedimentary rocks of the paleoisland-arc complex and granodiorites of the Mansurovo pluton. Figures 9. Table 1. References 36. Key words: tourmaline, boron, gold, xenotime-(Y), Murtykty deposit, Republic of Bashkortostan.

scholarly journals Amethyst occurrences in Tertiary volcanic rocks of Greece: mineralogical and genetic implications

2013 ◽  
Vol 47 (1) ◽  
pp. 477 ◽  
Author(s):  
P. Voudouris ◽  
I. Psimis ◽  
C. Mavrogonatos ◽  
C. Kanellopoulos ◽  
M. Kati ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Hydrothermal Activity ◽  
Hydrothermal Fluids ◽  
Calc Alkaline ◽  
Northern Greece ◽  
Volcanic Arc ◽  
Quartz Veins ◽  
High Sulfidation ◽  
Host Rocks ◽  
Of Greece

Epithermal-altered volcanic rocks in Greece host gem-quality amethyst veins in association with various silicates, carbonates, oxides, sulfides and halides. Host rocks are Oligocene to recent calc-alkaline to shoshonitic lavas and pyroclastics of intermediate- to acid composition. The amethyst-bearing veins occur in the periphery of porphyry-type and/or high-sulfidation epithermal mineralized centers in northern Greece (e.g. Sapes, Kirki, Kornofolia/Soufli, Lesvos island) and on Milos island in the active Aegean Volcanic Arc. Hydrothermal alteration around the quartz veins includes sericitic, K-feldspar (adularia), argillic, propylitic and zeolitic types. Precipitation of amethyst in the northern Greece occurrences, took place during the final stages of the magmatic-hydrothermal activity from near-neutral to alkaline fluids, as indicated by the presence of gangue adularia, calcite, smectite, chlorite, sericite, pyrite, zeolites (laumontite, heulandite, clinoptilolite), analcime and minor amounts of barite, halite, epidote and fluorite in the quartz veins. Amethyst at Milos Island (Chondro Vouno and Kalogries-Vani areas), is accompanied by barite, smectite and lepidocrocite. Colloform-crustiform banding with alternations of amethyst, chalcedony and/or carbonates is a common characteristic of the studied amethyst-bearing veins. Fluid inclusion- and mineralogical data suggest that the studied amethyst were formed at: 174-246 °C (Sapes area), 100-175 °C (Kirki and Kornofolia areas) and 223-234°C (Lesvos island). The amethyst formation requires oxidizing conditions and is probably the result of mixing between meteoric or seawater with upwelling hydrothermal fluids. The involvement of seawater in the studied mineralization is supported by the presence of halite and abundant barite in the veins. Finally, the studied amethyst deposits should be evaluated as potential gemstone sources in Greece.

scholarly journals Genesis of the Koka Gold Deposit in Northwest Eritrea, NE Africa: Constraints from Fluid Inclusions and C-H-O-S Isotopes

2019 ◽  
Author(s):  
Kai Zhao ◽  
Huazhou Yao ◽  
Jianxiong Wang ◽  
Ghebsha Fitwi Ghebretnsae ◽  
Wenshuai Xiang ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Meteoric Water ◽  
Gold Mineralization ◽  
Early Stage ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Quartz Veins ◽  
Three Phase ◽  
Igneous Origin ◽  
Ne Africa

The Koka gold deposit is located in the Elababu shear zone between the Nakfa terrane and the Adobha Abiy terrane, NW Eritrea. Based on the paragenetic study two main stages of gold mineralization were identified in the Koka gold deposit: 1) an early stage of pyrite-chalcopyrite-sphalerite-galena-gold-quartz vein; and 2) a second stage of pyrite-quartz veins. NaCl-aqueous inclusions, CO2-rich inclusions, and three-phase CO2-H2O inclusions occur in the quartz veins at Koka. The ore-bearing quartz veins formed at 268℃, from NaCl-CO2-H2O(-CH4) fluids averaging 5 wt% NaCl eq. The ore-forming mechanisms include fluid immiscibility during stage I, and mixing with meteoric water during stage II. Oxygen, hydrogen and carbon isotopes suggest that the ore-forming fluids originated as mixtures of metamorphic water, meteoric water and magmatic water, whereas sulfur isotope suggest an igneous origin. Features of geology and ore-forming fluid at Koka deposit are similar to those of orogenic gold deposits, suggesting the Koka deposit might be an orogenic gold deposit related to granite.

scholarly journals Mineralizing Events of the World-Class Volta Grande Gold Deposit, Southeastern Amazonian Craton, Brazil

2021 ◽  
Vol 6 (1) ◽  
pp. 19
Author(s):  
Hugo Paiva Tavares de Souza ◽  
Carlos Marcello Dias Fernandes ◽  
Ricardo de Freitas Lopes ◽  
Stéphane Amireault ◽  
Marcelo Lacerda Vasquez
Keyword(s):  
Gold Deposit ◽  
Native Gold ◽  
Gold Deposits ◽  
Quartz Veins ◽  
The World ◽  
Intrusive Rocks ◽  
Amazonian Craton ◽  
World Class ◽  
High Level ◽  
Southeastern Region

The southeastern region of the Amazonian Craton has been the target of several metallogenetic surveys, which recently led to the identification of the world-class Volta Grande gold deposit with gold reserves of ~3.8 Moz at 1.02 g/t. This deposit is located ~60 km southeast of Altamira city, Pará state, and is hosted by the Três Palmeiras intrusive greenstone belt that is located in the northern Bacajá tectonic domain (2.24–2.0 Ga). The mineralization is hosted by a high-level intrusive and mylonitized suite. Local kinematic indicators suggest dip-slip movement in which the greenstone moves up relative to the intrusive rocks. Native gold mostly occurs as isolated grains in centimeter-wide quartz veins and veinlets associated with pervasive carbonate alteration that was synchronous with dynamic metamorphism. Part of the gold is also associated with disseminated sulfides in this generally low-sulfide mineralization. These relationships are compatible with orogenic lode-type gold systems elsewhere. New petrographic studies from core samples along a stratigraphic profile reveal the presence of lava flows and dykes of rhyodacite, rhyolite, and plutonic rocks such as quartz monzonite, granodiorite, monzodiorite, and subordinate microgranite crosscutting an earlier style of mineralization. These rocks are characterized by potassic, propylitic, intermediate argillic, and/or carbonate hydrothermal alterations in selective, pervasive, or fracture-controlled styles. Within the hydrothermal volcano-plutonic sequence, gold occurs as disseminated isolated grains or replacing sulfides. Both native gold and sulfides are also present in centimetric quartz veinlets. Such features of the deposit are similar to those from porphyry-type and low- to intermediate-sulfidation epithermal systems already identified in the Amazonian Craton. The Volta Grande deposit data suggest a second mineralizing event, common in large-tonnage gold deposits, and can represent a new exploration guide.

U-Pb Dating on Hydrothermal Rutile and Monazite from the Badu Gold Deposit Supports an Early Cretaceous Age for Carlin-Type Gold Mineralization in the Youjiang Basin, Southwestern China

2021 ◽  
Author(s):  
Wei Gao ◽  
Ruizhong Hu ◽  
Albert H. Hofstra ◽  
Qiuli Li ◽  
Jingjing Zhu ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Early Cretaceous ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Detrital Zircons ◽  
Youjiang Basin ◽  
Host Rocks ◽  
Gold Bearing ◽  
Carlin Type Gold Deposits

Abstract The Youjiang basin on the southwestern margin of the Yangtze block in southwestern China is the world’s second largest Carlin-type gold province after Nevada, USA. The lack of precise age determinations on gold deposits in this province has hindered understanding of their genesis and relation to the geodynamic setting. Although most Carlin-type gold deposits in the basin are hosted in calcareous sedimentary rocks, ~70% of the ore in the Badu Carlin-type gold deposit is hosted by altered and sulfidized dolerite. Although in most respects Badu is similar to other Carlin-type gold deposits in the province, alteration of the unusual dolerite host produced hydrothermal rutile and monazite that can be dated. Field observations show that gold mineralization is spatially associated with, but temporally later than, dolerite. In situ secondary ion mass spectrometry (SIMS) U-Pb dating on magmatic zircon from the least altered dolerite yielded a robust emplacement age of 212.2 ± 1.9 Ma (2σ, mean square of weighted deviates [MSWD] = 0.55), providing a maximum age constraint on gold mineralization. The U-Th/He ages of detrital zircons from hydrothermally mineralized sedimentary host rocks at Badu and four other Carlin-type gold deposits yielded consistent weighted mean ages of 146 to 130 Ma that record cooling from a temperature over 180° to 200°C and place a lower limit on the age of gold mineralization in the basin. Hydrothermal rutile and monazite that are coeval with gold mineralization have been identified in the mineralized dolerite. Rutile is closely associated with hydrothermal ankerite, sericite, and gold-bearing pyrite. It has high concentrations of W, Fe, V, Cr, and Nb, as well as growth zones that are variably enriched in W, Fe, Nb, and U. Monazite contains primary two-phase fluid inclusions and is intergrown with gold-bearing pyrite and hydrothermal minerals. In situ SIMS U-Pb dating of rutile yielded a Tera-Wasserburg lower intercept age of 141.7 ± 5.8 Ma (2σ, MSWD = 1.04) that is within error of the in situ SIMS Th-Pb age of 143.5 ± 1.4 Ma (2σ, MSWD = 1.5) on monazite. These ages are ~70 m.y. younger than magmatic zircons in the host dolerite and are similar to the aforementioned U-Th/He cooling ages on detrital zircons from hydrothermally mineralized sedimentary host rocks. We, therefore, conclude that the Badu Carlin-type gold deposit formed at ca. 144 Ma. The agreement of the rutile and monazite ages with the U-Th-He cooling ages of Badu and four other Carlin-type gold deposits in the Youjiang basin suggests that ca. 144 Ma is representative of a regional Early Cretaceous Carlin-type hydrothermal event formed during back-arc extension.

LA-ICP-MS zircon U–Pb and sericite 40Ar/39Ar ages of the Songjianghe gold deposit in southeastern Jilin Province, Northeast China, and their geological significance

2019 ◽  
Vol 56 (6) ◽  
pp. 607-628
Author(s):  
Xiao-Tian Zhang ◽  
Jing-Gui Sun ◽  
Zheng-Tao Yu ◽  
Quan-Heng Song
Keyword(s):  
Gold Deposit ◽  
Gold Deposits ◽  
Pacific Plate ◽  
Jilin Province ◽  
Late Triassic ◽  
Retrograde Metamorphism ◽  
Late Permian ◽  
Multi Stage ◽  
Metallogenic Epoch ◽  
Host Rocks

The Songjianghe deposit is a newly discovered altered gold deposit in the southeastern Jiapigou-Haigou Gold Metallogenic Belt (JHGMB) in southeastern Jilin Province of NE China. The host rocks were considered to be the Mesoproterozoic Seluohe Group, and the metallogenic epoch lacked accurate isotopic constraints. To determine the age and metallogenic setting of the deposit, we describe the geologic characteristics of the deposit and present the results of petrographic and geochronologic analyses of the host rocks and ores. The ore bodies are hosted within a suite of amphibolite facies metamorphic rocks superimposed by greenschist facies indicative of retrograde metamorphism. Zircon U–Pb dating results indicate that the host rocks belong to the Jiapigou Group that formed at the end of the Neoarchean (2543–2527 Ma). Subsequently, the rocks successively underwent metamorphism during the late Neoarchean (2521–2506 Ma), retrograde metamorphism caused by the closure of the Paleo-Asian Ocean during the late Permian to Early Triassic (262–250 Ma), and extension after the closure of the Paleo-Asian Ocean during the Late Triassic (231–210 Ma). Sericite 40Ar/39Ar dating results suggest that the Songjianghe deposit formed during the Late Jurassic between 157 Ma and 156 Ma. By combining these new insights with those of previous studies, we propose that the Songjianghe deposit is a mesothermal gold deposit and that mineralization occurred during the extensional period in the intermittent stage that followed the first subduction of the Paleo-Pacific Plate. All the gold deposits in the JHGMB formed from the late Permian to Early Cretaceous by multi-stage mineralization events that corresponded temporally with the tectonic evolution of the Paleo-Asian Ocean and the episodic subduction of the Paleo-Pacific Plate.

Thermoluminescence of quartz from Shihu gold deposit, western Hebei province, China: some implications for gold exploration

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
Ye Cao ◽  
Shengrong Li ◽  
Meijuan Yao ◽  
Huafeng Zhang
Keyword(s):  
Gold Deposit ◽  
Cross Sections ◽  
North China Craton ◽  
North China ◽  
Mineral Exploration ◽  
Gold Deposits ◽  
Quartz Veins ◽  
The North ◽  
Indicator Mineral ◽  
Gold Bearing

AbstractThermoluminescence (TL) of monomineralic separates have been widely used in various geosciences fields in order to trace the thermal history and aid in prospecting for gold deposits. Quartz is a ubiquitous mineral in the Shihu gold deposit, which is situated in the northern part of the Taihang orogenic belt in the North China craton (NCC). The deposit is hosted by ductile-brittle faults within an Archean metamorphic core complex of the Fuping Group. This deposit is characterized by gold-bearing quartz-polymetallic sulfides and quartz veins. New TL results have been obtained for quartz, in which four type-TL glow curves were identified. The gold-bearing quartz present type III glow curves that consist of two peak glow curves at the middle and high peak temperatures with the similar TL intensity. In addition, the cross-sections of peak temperatures and TL intensity highlight the valuable area where the Au-bearing quartz present weak TL intensity and low-middle peak temperatures. Our results significantly enhance the usefulness of quartz in metallogenic studies of the North China craton and as an indicator mineral in mineral exploration of the Taihang Mountain region.

Chapter 6: The Supergiant, High-Grade, Paleoproterozoic Metasedimentary Rock- and Shear Vein-Hosted Obuasi (Ashanti) Gold Deposit, Ghana, West Africa

2020 ◽  
pp. 121-140
Author(s):  
Nicholas H.S. Oliver ◽  
Andrew Allibone ◽  
Michael J. Nugus ◽  
Carlos Vargas ◽  
Richard Jongens ◽  
...  
Keyword(s):  
West Africa ◽  
Gold Deposit ◽  
Source Rocks ◽  
Fluid Injection ◽  
Quartz Veins ◽  
The World ◽  
Basin Edge ◽  
Siliciclastic Rocks ◽  
Host Rocks ◽  
Greenschist Facies Metamorphism

Abstract Obuasi, with a total mineral resource plus past production of 70 Moz, is the largest gold deposit in West Africa, and one of the largest in the world. It is hosted by ~2135 Ma siliciclastic rocks of the Eburnean Kumasi Basin, which were obliquely shortened along an inverted boundary with the older Eoeburnean Ashanti belt to the east. Greenschist facies metamorphism was coeval with mineralization and related alteration at ~2095 Ma. The steeply dipping, ENE-plunging lodes extend over an 8-km strike length and to depths of >2.5 km. They include paragenetically complex gold-rich quartz veins surrounded by refractory auriferous arsenopyrite and closely associated carbonate-muscovite alteration halos in deformed carbonaceous phyllites and subordinate metaigneous host rocks. Gold and arsenic were initially precipitated during deformation-assisted interaction with reduced host rocks at ~350°C and 100 to 200 MPa. The mineralizing fluids were derived primarily from deeper, As-rich metasedimentary sources by basinal fluid expulsion and metamorphic devolatilization triggered by inversion and shortening, followed by transpression. Continued fluid injection during and after the metamorphic peak produced changes in gold fineness, sulfide assemblages, repeated dissolution (stylolites) and reprecipitation of mineralized veins, and a change from early deformed shear-related, sulfide-rich lodes to later quartz-rich lodes that plunge down or across the axes of younger transpressional folds. Channelized fluid flow due to reactivation of basin-edge transfer structures, and/or irregularly distributed gold source rocks, may explain the variation in gold endowment along the former basin boundary.

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