KISACA
AFRİKA KITASININ MADENLERİ ve OROJENİK ALTIN YATAKLARI
Petrography,
Mineralogy, and Compositional Characteristics of Rare-Metal-Bearing Pegmatite
of Côte d’Ivoire: A Review
K. F. Oufouet et al.
August 2025
Afrika kıtası, nadir metallerle zenginleştirilmiş
pegmatitler açısından zengindir. Kıtadaki birçok bölge, önemli nadir element pegmatit
yataklarıyla tanınır. Bunlar arasında, en zengin tantal ve lityum
kaynaklarından biri olan Demokratik Kongo Cumhuriyeti, tantal, berilyum ve
lityum içeren pegmatit yatakları bulunan Ruanda, niyobyum, tantal ve kalay
yatakları bulunan Burundi ve yaklaşık 100 yıllık kalay ve tantal üretimi
bulunan Uganda gibi Orta Afrika ülkeleri bulunur. Diğer kaynaklar ise Mısır,
Etiyopya (tantal bakımından zengin pegmatitler), Somali, Mozambik, Madagaskar,
Namibya, Zimbabve ve Güney Afrika'da bulunur.
Birçok Batı Afrika ülkesi, kanıtlanmış kaynak ve/veya
potansiyele sahip bol miktarda lityum, kalay, niyobyum, tantal, berilyum ve
sezyum minerali varlığına sahiptir. Bunlar arasında: Bölgenin en gelişmiş ve
önemli lityum yataklarına ev sahipliği yapan Mali (Bougouni, Goulamina, Falea);
Üretime yakın Ewoyaa projesiyle Gana (Winneba, Mankoadze, Cape Coast); Yaygın
lityum keşifleri ve dikkate değer niyobyum-tantal oluşumlarıyla Nijerya (Jos
Plateau, Nasarawa, Kogi, Ekiti); Birkaç umut verici lityum taşıyan ve
columbo-tantalit taşıyan pegmatit prospektifinin araştırıldığı Fildişi Sahili
(Issia, Boundiali, Agboville); Bölgesel pegmatitik oluşumları içeren Burkina
Faso (Gaoua, Boromo, Houndé) ve Senegal (Kedougou, Saraya); Tarihi kalay
üretimi ve küçük lityum potansiyeliyle bilinen Nijer (Liptako, Air Massif);
Sierra Leone (Kono, Kenema, Bo) ve Liberya (Nimba, Bong, Grand Cape Mount),
mineralizasyonun hala zanaatkar veya erken arama aşamasında olduğu yerler.
ECONOMIC GEOLOGY: OROGENIC GOLD DEPOSITS
INTRODUCTION
Orogenic gold deposits are one of the most significant sources of gold in the world, accounting for a large proportion of global production.
These deposits are formed in regions of mountain-building, known as orogenic belts, and are closely associated with metamorphic rocks and major fault systems.
They are called "orogenic" because their formation is related to tectonic processes during the orogeny, or the structural formation of mountains.
Orogenic gold deposits are particularly important because they provide high-grade gold resources and are economically viable to mine in many regions.
GEOLOGICAL SETTING
Orogenic gold deposits typically occur in metamorphic terranes ranging from low-grade greenschist to high-grade amphibolite facies.
They are commonly found along major crustal-scale faults or shear zones, which act as conduits for hydrothermal fluids that transport and deposit gold.
These deposits are most abundant in regions of past or ongoing tectonic activity, such as the greenstone belts of West Africa, the Canadian Shield, the Carlin Trend in Nevada, and the Yilgarn Craton in Australia.
FORMATION AND GENESIS
The formation of orogenic gold deposits involves several interrelated processes, including fluid generation, fluid migration, and mineral precipitation.
Metamorphic dehydration reactions in rocks at depth produce hot, aqueous fluids rich in dissolved gold and other metals.
These fluids migrate along faults, fractures, and shear zones toward the surface.
As they ascend, changes in pressure, temperature, and chemistry cause gold and associated minerals, such as quartz, pyrite, arsenopyrite, and sulfides, to precipitate.
The fluids in orogenic gold systems are typically low in salinity and contain significant amounts of carbon dioxide and methane, which help in the transport and deposition of gold.
Structural traps, such as bends in faults, dilation zones, and intersections of shear zones, provide the physical space for ore deposition.
MINERALOGY AND PETROGRAPHY
Quartz is the dominant gangue mineral in orogenic gold deposits, often forming veins, veinlets, and stockworks.
CONCLUSION
Orogenic gold deposits are a cornerstone of economic geology, linking fundamental geological processes with practical economic outcomes.
They demonstrate the importance of tectonics, metamorphism, and hydrothermal processes in forming high-value mineral resources.
With the integration of modern exploration technologies, geochemical modeling, and sustainable mining practices, these deposits will continue to provide critical resources for global economic development while balancing environmental stewardship.
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