scholarly journals Geology and gold mineralization of the Gold Basin-Lost Basin mining districts, Mohave County, Arizona, with a section on K-Ar chronology of mineralization and igneous activity, and a section on implications of the compositions of lode and placer gold

1987 ◽  
Author(s):  
Ted G. Theodore ◽  
Will N. Blair ◽  
J. Thomas Nash ◽  
E.H. McKee ◽  
J.C. Antweiler ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Placer Gold ◽  
Igneous Activity ◽  
Mohave County ◽  
Mining Districts

scholarly journals Typomorphic Features of Placer Gold from the Billyakh Tectonic Melange Zone of the Anabar Shield and Its Potential Ore Sources (Northeastern Siberian Platform)

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 281
Author(s):  
Boris Gerasimov ◽  
Vasily Beryozkin ◽  
Alexander Kravchenko
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Coarse Fraction ◽  
Gold Deposits ◽  
Primary Sources ◽  
The Arctic ◽  
Geochemical Data ◽  
Placer Gold ◽  
Anabar Shield ◽  
Tectonic Mélange

Precambrian shields and outcropped Precambrian rock complexes in the Arctic may serve as the most important sources of various types of mineral raw materials, including gold. The gold potential of the Anabar shield in the territory of Siberia has, thus far, been poorly studied. A number of primary and placer gold occurrences have been discovered there, but criteria for the prediction of and search for gold mineralization remain unclear. The main purpose of this paper was to study the typomorphic features of placer gold in the central part of the Billyakh tectonic mélange zone in the Anabar shield and to compare them to mineralization from primary sources. To achieve this, we utilized common methods for mineralogical, petrographic, and mineragraphic analyses. Additionally, geochemical data were used. As a result of this investigation, important prospecting guides were identified, and essential criteria for the prediction of and search for gold deposits were elucidated. The characteristics of the studied placer gold were specific for gold derived from a proximal provenance. These characteristics included the poor roundness of the native gold grains, a cloddy–angular and dendritic form, an uneven surface, and a high content of coarse-fraction native gold (0.5–2 mm), which was as high as 24% of the volume of analyzed native gold. In addition, we conducted a study on the mineralogical features of the gold-sulfide mineralization that was disseminated throughout a small exposure area of paleo-Proterozoic para- and orthogneisses in the Anabar shield basement. A comparison of mineral inclusions in the coarse-fraction native gold and mineral assemblages in the ore deposits showed that one of the possible primary sources for placer gold might be small bodies of metasomatically altered orthogneisses associated with large granitoid plutons.

Secondary gold mineralization in the Amani Placer Gold Deposit, Tanzania

2019 ◽  
Vol 107 ◽  
pp. 87-107 ◽  
Author(s):  
Stephan C. Dunn ◽  
Bjorn P. von der Heyden ◽  
Abraham Rozendaal ◽  
Rikard Taljaard
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Placer Gold

scholarly journals Reconstruction of the Ancient River Network and Prospects of the Placer Gold Mineralization on the Southern Part of the Miass Intermountain Depression (South Urals)

2021 ◽  
Vol 20 (1) ◽  
pp. 56-62
Author(s):  
P. V. Kazakov ◽  
Keyword(s):  
Gold Mineralization ◽  
River Network ◽  
South Urals ◽  
Geological Exploration ◽  
Placer Gold ◽  
The Right ◽  
Placer Formation

We conducted the reconstruction of the ancient river network of the basins of the right tributaries of the Uy River Shartymka and Kiruda located in the southern part of the Miass intermountain depression within the Shartymskiy graben and its southern periphery. The sequence of placer formation from Cretaceous and Miocene karst-alluvial placers (Shartymsky graben) to the Eopleistocene and Neopleistocene has been established. In the valleys of the Shartymka and Kiruda rivers, areas of inherited development have been identified. This increased the reliability of estimation of the placer gold forecast resources. The most promising areas are recommended for geological exploration licensing.

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.

scholarly journals Placer gold occurrences along the major rivers of Nepal Himalaya and their possible primary sources

1996 ◽  
Vol 13 ◽  
Author(s):  
K. P. Kaphle ◽  
P. R. Joshi ◽  
H. R. Khan
Keyword(s):  
Gold Mineralization ◽  
Gold Deposits ◽  
Primary Sources ◽  
Gold Content ◽  
Lower Paleozoic ◽  
Nepal Himalaya ◽  
Placer Gold ◽  
Flood Plains ◽  
River Flood ◽  
Primary Gold

Recent exploration in Lungri Khola area, Rolpa district, midwestern Nepal helped to delineate a discontinuous 1.5 to 40 m thick and about 30 km long primary gold mineralization zone in the Precambrian greenschists and Lower Paleozoic micaceous marbles of the Lesser Himalaya. The gold content in these lodes vary from 0.01 to 6.7 ppm. In eastern Nepal occurrences of primary gold is recorded in quartz-biotiteschist, amphibolite and pegmatite bodies in Sunmai and Bering Khola of Ilam district. Fine flakes of gold also occur in the pyritiferous quartz beds/lenses in chlorite-sericite phyllite and quartzite of Bamangaon polymetallic prospect, Dadeldhura district, far western Nepal. In this prospect the gold content is from 0.2 to 0.8 ppm, and one sample showed up to 14 ppm. Primary gold occurrences are also detected in few irregular quartz-pyrite veins and iron-copper sulphide bearing quartzite lying close to the amphibolite bodies. Some pyrite bearing radioactive quartzite beds in Banku Quartzite of Purchauni Crystalline Complex exposed at Boregad, Bangabagar, Baggoth and Jamari Gad area in Darchula and Baitadi districts, far western Nepal also contain gold. The gold content in the radioactive quartzite varies from 0.2 to 1.2 ppm and in some pyritiferous radioactive quartzite floats it reaches up to 5.06 ppm. The primary gold appears to be of synsedimentary, hydrothermal and possibly volcanogenic in origin. Placer gold is derived from primary sources and deposited at favourable locations along the river flood plains. Further investigations in similar geological terrain may help to identify economically viable primary as well as placer gold deposits in the Nepal Himalaya.

scholarly journals Types of Tellurium Mineralization of Gold Deposits of the Aldan Shield (Southern Yakutia, Russia)

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 698
Author(s):  
Larisa A. Kondratieva ◽  
Galina S. Anisimova ◽  
Veronika N. Kardashevskaia
Keyword(s):  
Large Scale ◽  
Native Gold ◽  
Gold Mineralization ◽  
Aldan Shield ◽  
Original Data ◽  
Gold Deposits ◽  
Ore Deposits ◽  
Gold Content ◽  
Southern Yakutia ◽  
Igneous Activity

The published and original data on the tellurium mineralization of gold ore deposits of the Aldan Shield are systematized and generalized. The gold content is related to hydrothermal-metasomatic processes caused by Mesozoic igneous activity of the region. The formation of tellurides occurred at the very late stages of the generation of gold mineralization of all existing types of metasomatic formations. 29 tellurium minerals, including 16 tellurides, 5 sulfotellurides and 8 tellurates have been identified. Tellurium minerals of two systems predominate: Au-Bi-Te and Au-Ag-Te. Gold is not only in an invisible state in sulfides and in the form of native gold of different fineness, but also is part of a variety of compounds: montbrayite, calaverite, sylvanite, krennerite and petzite. In the gold deposits of the Aldan Shield, three mineral types are distinguished: Au-Ag-Te, Au-Bi-Te, and also a mixed one, which combines the mineralization of both systems. The decrease in the fineness of native gold is consistent with the sequence and temperatures of the formation of Te minerals and associated mineral paragenesis from the epithermal–mesothermal Au-Bi-Te to epithermal Au-Ag-Te. The conducted studies allowed us to determine a wide variety of mineral species and significantly expand the area of distribution of Au-Te mineralization that indicates its large-scale regional occurrence in the Aldan Shield.

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.

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