morphism of the migmatitic gneiss complex is in amphibolite to granulite facies grade; the schist belt which is essentially N-S to NNE-SSW trending belts and concentrated more in western half of the Nigeria is greenschist-amphibolite facies (Ajibade and Wright 1989). The rocks of the schist belt host the gold and

The term orogenic gold deposits has been widely accepted, but there has been continuing debate on their genesis. Early syn-sedimentary or syn-volcanic models and hydrothermal meteoric-fluid models are now invalid. Magmatic-hydrothermal models fail because of the lack of consistent spatially associated granitic intrusions and inconsistent …

The Qussuk gold occurrence illustrates that epithermal gold deposits existed at the Archean, and that they can be preserved up to upper amphibolite metamorphic conditions, further highlighting the ...

Abstract and Figures. A metamorphic devolatilization model can explain the enrichment, segregation, timing, distribution and character of many goldfields such as those found in Archean greenstone ...

Gold prices are constantly changing during market hours. The spot price of gold and the spot price of silver is determined by many domestic and foreign exchanges, which allows the spot prices to update from Sunday through Friday, 6 pm EST to 5:15 am EST. While gold, and other precious metals, may experience longer periods of relatively …

To model the formation of orogenic gold deposits, in a global perspective, it is important to understand the ore-forming conditions not only for deposits hosted in greenschist facies rocks but also in amphibolite facies. The Paleoproterozoic Fäboliden deposit in northern Sweden belongs to the globally rare hypozonal group of orogenic …

Senja, Norway. Width of sample 10 cm. Amphibolite is a metamorphosed mafic igneous rock ( basalt, gabbro) although it is usually difficult to determine the protolith because original features are often obliterated. …

Our thermodynamic simulations indicate that subsolidus metamorphic devolatilization of komatiites at ~700 °C (upper amphibolite facies) can unlock …

Among those, the La Pointe deposit has several characteristics similar to other amphibolite facies orogenic gold deposits, such as disseminated and replacement mineralization, and an alteration ...

Petrology and gold mineralization of the amphibolite belt, Ilesha area, Southwestern Nigeria. Geologie en mijnbouw, 65, p.189-195, maps, table, English résumé. International African Bibliography Online .

Amphibolite, a rock composed largely or dominantly of minerals of the amphibole group. The term has been applied to rocks of either igneous or metamorphic origin. In igneous …

A syn-peak metamorphic introduction of gold (i.e. continuum) in a hydrothermal fluid would lead to in situ partial melting, rather than aqueous gold transport, given the inferred metamorphic grade (see 3 Principles of partial melting in the uppermost amphibolite and granulite facies, 4.2.1 Geological setting of the Big Bell gold deposit). …

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 ...

An important group of rock-forming minerals in igneous and metamorphic rocks, amphiboles share a similar crystal structure and cleavage pattern, but contain different proportions of sodium (Na), calcium (Ca), iron (Fe) and magnesium (Mg), which substitute for one another in its crystal structure. Amphibole minerals are generally dark-colored ...

It is suggested that a gold-bearing magmatic rock was metamorphosed into amphibolite and metadolerite with the subsequent partitioning of Fe-oxide, rutile and Fe-rich biotite in the gold grains ...

The close spatial association of creeks containing placer gold and the gneiss, schist, amphibolite, and marble unit strongly suggests this metamorphic unit is the gold source. High terrace gravels record a time from the late Tertiary to early Pleistocene when the ancestral Fortymile River and its major tributaries, the North and South Forks ...

KEYWORDS: amphibolite facies, geochronology, gold, metamorphism, migmatite Introduction 'Orogenic' gold deposits commonly form in greenschist facies terrains, and are rare in high-grade metamorphic rocks (Groves, 1993). This is conventionally attributed to gold mineralization forming from gold complexes

Metamorphic devolatilization of pelite is a key process in sourcing fluids and metals for orogenic gold deposits. The process of extracting S, Au, As, Cu, Pb and Zn …

Many workers accept a metamorphic model for orogenic gold ore formation, where a gold-bearing aqueous-carbonic fluid is an inherent product of devolatilization across the greenschist-amphibolite ...

The amphibolite, most likely grunerite, has now been largely altered to hematite, goethite and quartz and it displays a beautiful golden iridescence. Also called "Gold Leaf Stone". It occurs in the Pilbara region of Western Australia on Abydos Station approximately 120 km south of Port Hedland.

Amphibolite is a coarse-grained metamorphic rock, predominantly composed of mineral amphibole and plagioclase …

The Weizigou gold deposit is located 30 km northwest of Jixi in Heilongjiang Province. Strata exposed in the orefield are mainly the Ximashan Formation, which is composed of biotite-amphibole granulite with marble and migmatite intercalations; the Jiantang Formation, which comprises marble, quartz schist, migmatite, granulite, and …

The Navachab gold mine in central Namibia is situated in amphibolite-facies, marble-dominated metasediments of the Neoproterozoic Damara Sequence in the Pan-African Damara Belt.

The orogenic gold deposits have been subdivided into the hypozonal (>12 km), mesozonal (6 to 12 km), and epizonal (<6 km) types by Groves et al. (1998).Major features, especially the alteration and mineralization features, of representative deposits from six orogenic gold provinces with varied formation depth and gold mineralization …

Deposits are also found in higher-grade metamorphic rocks, known as hypozonal gold deposits. These deposits are mostly hosted in amphibolite-facies rocks in greenstone belts and are characterized by high-temperature alteration assemblages such as garnet, diopside, hornblende, and K-feldspar and ore-forming temperatures as high as …

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Andrew Alden. Amphibolite is a rock composed mostly of amphibole minerals.Usually, it's a hornblende schist like this as hornblende is the commonest amphibole. Amphibolite forms when basaltic rock is subjected to higher temperatures between 550 C and 750 C) and slightly greater pressure range than that which yields …

The greenschist-amphibolite facies transition zone within metabasites is of great importance due to the common occurrence of this transition within greenstone belts, and the proposition that fluids released across the transition may be involved in orogenic gold deposit formation.

The one-million ounce Glenburgh gold deposit was formed in the Paleoproterozoic, upper-amphibolite facies Glenb urgh T errane in the southern Gascoyne Province of W estern Australia.

The most obvious shortcoming is in considering ore deposits found in rocks of uppermost amphibolite and granulite facies domains where temperatures were …