Two stage of gold-bearing sulfide ores of early Proterozoic gabbroids in the north Ladoga area

In a study based on Pb isotopes, it has been shown that the formation of gold-sulfide mineralization in the Early Proterozoic gabbros of the Northern Ladoga region is associated with different tectonic phases. This conclusion is based on a comparative study of isotopic data for feldspars and lead sulfides in two Early Proterozoic intrusions; Velimäki and Alattu-Päkylä. The investigated intrusions have similar geological settings at the junction of the Svecofennian accretionary complex and the Karelian craton. Both massifs are characterized by manifestations of noble metal sulfide mineralization associated with zones of local shear deformations. The formation of the studied ore massifs is attributed to the Svecofennian and Caledonian tectonic stages. Feldspars of Velimäki intrusion have parameters and model age of Pb significantly older than U-Pb age of zircon (1.9 Ga), although they correspond to the Svecofennian time of magmatic crystallization of gabbro and clinopyroxenites, while sulfide pyrite-pyrrhotite mineralization is associated with gold in these rocks with the Caledonian stage of fluid-thermal processing of the Early Proterozoic magmatic mineral paracenteses. Feldspars and sulfides of the Alattu-Päkylä intrusion have similar lead isotopic parameters and Pb model age (~ 2 Ga), also somewhat older than the U-Pb age of zircon, but at the same time indicating the formation of rock-forming and ore sulfide associations with gold during the Svecofennian (Early Proterozoic) plutonic and tectonic-thermal events. The source of lead sulfides of the Velimäki massif is characterized by the parameters of the upper crust with high µ2 = 238U / 204Pb, while the µ2 parameter of the minerals of the Alattu-Päkylä massif is slightly lower, which indicates the participation of the mantle-lower crustal reservoir material in the formation of magma.

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Native Metal Sulfide Mineralization of Perga Ore Knot (the Ukrainian Shield)

Mineralogical Journal ◽

10.15407/mineraljournal.39.04.077 ◽

2017 ◽

Vol 39 (4) ◽

pp. 77-88

Author(s):

B. SLOBODYAN ◽

V. PAVLYSHYN ◽

S. BONDARENKO ◽

L. STEPANYUK ◽

V. SYOMKA ◽

...

Keyword(s):

Metal Sulfide ◽

Ukrainian Shield ◽

Sulfide Mineralization ◽

Native Metal

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The Archaean Atâ intrusive complex (Atâ tonalite), north-east Disko Bugt, West Greenland

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/ggub.v181.5118 ◽

1999 ◽

pp. 103-112

Author(s):

Feiko Kalsbeek ◽

Lilian Skjernaa

Keyword(s):

Intrusive Complex ◽

The South ◽

Original Series ◽

Early Proterozoic ◽

West Greenland ◽

North East ◽

The North ◽

Southern Border ◽

Area North ◽

Igneous Layering

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kalsbeek, F., & Skjernaa, L. (1999). The Archaean Atâ intrusive complex (Atâ tonalite), north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 103-112. https://doi.org/10.34194/ggub.v181.5118 _______________ The 2800 Ma Atâ intrusive complex (elsewhere referred to as ‘Atâ granite’ or ‘Atâ tonalite’), which occupies an area of c. 400 km2 in the area north-east of Disko Bugt, was emplaced into grey migmatitic gneisses and supracrustal rocks. At its southern border the Atâ complex is cut by younger granites. The complex is divided by a belt of supracrustal rocks into a western, mainly tonalitic part, and an eastern part consisting mainly of granodiorite and trondhjemite. The ‘eastern complex’ is a classical pluton. It is little deformed in its central part, displaying well-preserved igneous layering and local orbicular textures. Near its intrusive contact with the overlying supracrustal rocks the rocks become foliated, with foliation parallel to the contact. The Atâ intrusive complex has escaped much of the later Archaean and early Proterozoic deformation and metamorphism that characterises the gneisses to the north and to the south; it belongs to the best-preserved Archaean tonalite-trondhjemite-granodiorite intrusions in Greenland.

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Mise‐a‐la‐masse survey for an auriferous sulfide deposit

Geophysics ◽

10.1190/1.1444924 ◽

2001 ◽

Vol 66 (1) ◽

pp. 70-77 ◽

Cited By ~ 6

Author(s):

B. B. Bhattacharya ◽

Dinesh Gupta ◽

Buddhadeb Banerjee ◽

Shalivahan

Keyword(s):

Massive Sulfide ◽

Sulfide Deposit ◽

Sulfide Mineralization ◽

Gold Exploration ◽

Copper Mineralization ◽

Geophysical Surveys ◽

Sulfide Content ◽

Equipotential Map ◽

Massive Sulfide Mineralization ◽

Gold Bearing

A mise‐a‐la‐masse survey was carried out in Bhukia area, Banswara district, Rajasthan, India for auriferous sulfide occurrences. This area was originally surveyed for copper mineralization. Exploratory drilling, however, proved it to be economically not viable. The area was reopened for geophysical surveys when grab samples indicated the presence of gold. Initial geophysical surveys for copper mineralization showed electromagnetic, induced polarization, and resistivity anomalies. At first, one borehole was drilled for gold exploration on the basis of initial geophysical surveys. It encountered massive sulfide mineralization in association with gold. Borehole logging and a mise‐a‐la‐masse survey were carried out in this borehole. Three further boreholes drilled on the basis of the mise‐a‐la‐masse results encountered massive sulfide mineralization in association with gold. One of the three boreholes, 100 m from the first borehole along strike, was used for another set of mise‐a‐la‐masse measurements. A composite equipotential map was prepared using the results of mise‐a‐la‐masse results of both the boreholes. The equipotential contours show a north‐northwest‐south‐southeast trend of mineralization. The boreholes drilled on the basis of the mise‐a‐la‐masse results have delineated a strike length of more than 500 m of gold‐bearing sulfide mineralization. The sulfide content ranges from 10 to 40% and gold concentration ranges from 2 to 6 ppm. The dip and plunge of the lode, as anticipated from the mise‐a‐la‐masse results, are toward the west and north, respectively. Mise‐a‐la‐masse surveys are continuing in the adjoining areas.

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Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Stark Formation

Canadian Journal of Earth Sciences ◽

10.1139/e76-060 ◽

1976 ◽

Vol 13 (4) ◽

pp. 563-578 ◽

Cited By ~ 20

Author(s):

D. K. Bingham ◽

M. E. Evans

Keyword(s):

Northwest Territories ◽

North American ◽

Geomagnetic Field ◽

Pole Position ◽

The West ◽

Stratigraphic Sequence ◽

Polar Wander ◽

Early Proterozoic ◽

The North ◽

Polarity Reversals

Paleomagnetic results from 55 sampling sites throughout the Stark Formation are reported. The known stratigraphic sequence of these sites enables the behaviour of the geomagnetic field in these remote times (1750 m.y.) to be elucidated. Two polarity reversals are identified and these represent potentially useful correlative features in strata devoid of index fossils. One of these is investigated in detail and indicates that behaviour of the geomagnetic field during polarity reversals was essentially the same in the early Proterozoic as it has been over the last few million years. The pole position (145°W, 15°S, dp = 3.5, dm = 6.9) lies far to the west of that anticipated from earlier results, implying further complexity of the North American polar wander curve. Possible alternatives to this added complexity are discussed.

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Metamorphic Origin of Ore-Forming Fluids for Orogenic Gold-Bearing Quartz Vein Systems in the North American Cordillera: Constraints from a Reconnaissance Study of 15N, D, and 18O

Economic Geology ◽

10.2113/98.1.109 ◽

2003 ◽

Vol 98 (1) ◽

pp. 109-123 ◽

Cited By ~ 8

Author(s):

Y. Jia

Keyword(s):

North American ◽

Quartz Vein ◽

Orogenic Gold ◽

North American Cordillera ◽

The North ◽

Gold Bearing

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Occurrence and genetic implications of hyalophane in manganese-rich iron-formation, Cuyuna Iron Range, Minnesota, USA

Mineralogical Magazine ◽

10.1180/minmag.1994.058.392.04 ◽

1994 ◽

Vol 58 (392) ◽

pp. 387-399 ◽

Cited By ~ 13

Author(s):

Peter L. McSwiggen ◽

G. B. Morey ◽

Jane M. Cleland

Keyword(s):

Depositional Environment ◽

Iron Formation ◽

East Central ◽

Early Proterozoic ◽

Iron Range ◽

The North ◽

History Of ◽

Ferromanganese Deposits ◽

Iron Formations ◽

Chemical Sediments

AbstractThe recent discovery of hyalophane [(K,Ba)Al1−2Si3−2O8] on the North range segment of the Early Proterozoic Cuyuna Iron Range of east-central Minnesota has shed new light on the depositional environment of these rocks. This Ba-feldspar occurs in a 10 m thick interval within the main iron-formation and typically contains between 8 and 26 mol.% celsian (BaAl2Si2O8). Its occurrence in several textural settings suggests that barium was being deposited at various stages in the paragenetic history of the iron-formation. Some of the hyalophane grains occur as the cores of micronodules, which are structurally similar to oolites or oncolites, but mineralogically are very complex. The hyalophane also occurs as rims on core grains of diverse mineral composition and as discrete phases in late crosscutting veins.Hyalophane, like other Ba-silicates, has a very restricted paragenesis. They are associated typically either with sedimentary manganese and ferromanganese deposits, or with Cu-Pb-Zn-Ba deposits. The presence of hyalophane in the Early Proterozoic manganiferous iron ores of east-central Minnesota casts doubt on the historic interpretation of these deposits as typical Superior-type sedimentary iron-formations and instead supports the view that these deposits, at least in part, consist of chemical sediments from a hydrothermal fumarolic system. The suggested involvement of a hydrothermal system is also supported by the occurrence of aegirine within the hyalophane-rich layer, and the occurrence of tourmalinites and Sr-rich baryte veins elsewhere in the Cuyuna North range.

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Caledonian eclogite-facies metamorphism of Early Proterozoic protoliths from the North-East Greenland Eclogite Province

Contributions to Mineralogy and Petrology ◽

10.1007/s004100050353 ◽

1998 ◽

Vol 130 (2) ◽

pp. 103-120 ◽

Cited By ~ 56

Author(s):

Hannes K. Brueckner ◽

Jane A. Gilotti ◽

Allen P. Nutman

Keyword(s):

East Greenland ◽

Early Proterozoic ◽

North East ◽

The North ◽

Facies Metamorphism ◽

Eclogite Facies

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Where are the Eburnian–Transamazonian collisional belts?

Canadian Journal of Earth Sciences ◽

10.1139/e90-148 ◽

1990 ◽

Vol 27 (10) ◽

pp. 1382-1393 ◽

Cited By ~ 53

Author(s):

Jean Michel Bertrand ◽

Emmanuel Ferraz Jardim de Sá

Keyword(s):

West African ◽

High Grade ◽

The West ◽

West African Craton ◽

Early Proterozoic ◽

Late Proterozoic ◽

Nappe Tectonics ◽

Pan African ◽

Orogenic Belts ◽

Lower Crustal

The reconstruction of Early Proterozoic crustal evolution and geodynamic environments, in Africa and South America, is incomplete if cratonic areas alone are studied. If the presence of high-grade gneisses is considered as a first clue to past collisional behaviour, 2 Ga high-grade gneisses are more abundant within the Pan-African–Brasiliano mobile belts than in the intervening pre-Late Proterozoic cratons. The West African craton and the Guiana–Amazonia craton consist of relatively small Archaean nuclei and widespread low- to medium-grade volcanic and volcanoclastic formations intruded by Early Proterozoic granites. By contrast, 2 Ga granulitic assemblages and (or) nappes and syntectonic granites are known in several areas within the Pan-African–Brasiliano belts of Hoggar–Iforas–Air, Nigeria, Cameroon, and northeast Brazil. Nappe tectonics have been also described in the Congo–Chaillu craton, and Early Proterozoic reworking of older granulites may have occurred in the São Francisco craton. The location of the Pan-African–Brasiliano orogenic belts is probably controlled by preexisting major structures inherited from the Early Proterozoic. High-grade, lower crustal assemblages 2 Ga old have been uplifted or overthrust and now form polycyclic domains in these younger orogenic belts, though rarely in the cratons themselves. The Congo–Chaillu and perhaps the São Francisco craton are exceptional in showing controversial evidence of collisional Eburnian–Transamazonian assemblages undisturbed during Late Proterozoic time.

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