OVERVIEW OF EPITHERMAL GOLD DEPOSITS

Öz

This review aims to evaluate the geological, geochemical, and hydrothermal properties of low- and high-sulfidation epithermal systems within a holistic framework. Fluid compositions, pH–fO₂ conditions, alteration mineral zonation, metal transport patterns, and ore precipitation mechanisms described in the literature are comparatively investigated. In high-sulfidation systems, a low pH (≤2), high oxygen fugacity, and low salinity (≤5 wt.% NaCl) fluid regime, resulting from the condensation of SO₂-dominated magmatic vapor, controls advanced argillic alteration (alunite–pyrophyllite) and porous silica development, while mineralization is linked to magmatic fluid–meteoritic water mixing or deep vapor absorption. In contrast, low-sulfidation systems develop in a hydrothermal environment dominated by meteoric, neutral-pH, and low-salinity fluids with reducing properties. Au transport is controlled by the stability of Au–bisulfide complexes. The loss of H₂S/CO₂ from boiling triggers gold precipitation by influencing both pH gradients and the illite–adularia–calcite stability fields. A comparison of the two systems demonstrates that fluid sources, volatile behavior, and hydrothermal instabilities play decisive roles in the formation of epithermal deposits. This review provides a useful conceptual basis for understanding epithermal mineralization and developing ore exploration models.

Anahtar Kelimeler

• Epithermal deposits
• low sulphidation
• high sulphidation
• vuggy silica

EPİTERMAL ALTIN YATAKLARINA GENEL BAKIŞ

Öz

Bu derleme çalışması, düşük ve yüksek sülfidasyon epitermal sistemlerin jeolojik, jeokimyasal ve hidrotermal özelliklerini bütüncül bir çerçevede değerlendirmeyi amaçlamaktadır. Literatürde tanımlanan akışkan bileşimleri, pH–fO₂ koşulları, alterasyon mineral zonlaşması, metal taşınım formları ve cevher çökelme mekanizmaları karşılaştırmalı olarak incelenmiştir. Yüksek sülfidasyon sistemlerinde SO₂-dominant magmatik buharın yoğunlaşması ile gelişen düşük pH (≤2), yüksek oksijen fugasitesi ve düşük tuzluluklu (≤5 wt.% NaCl) akışkan rejimi; ileri arjilik alterasyon (alünit–pirofillit) ile boşluklu silika gelişimini kontrol ederken, cevherleşmenin magmatik akışkan–meteorik su karışması veya derin buhar absorbsiyonuna bağlı olduğu görülmektedir. Buna karşın düşük sülfidasyon sistemleri, meteoritik kaynaklı, nötr pH’lı ve indirgen karakterli düşük tuzluluklu akışkanların egemen olduğu bir hidrotermal ortamda gelişmekte; Au taşınımı Au–bisülfür komplekslerinin kararlılığı ile denetlenmektedir. Kaynama kaynaklı H₂S/CO₂ kaybı hem pH değişimlerini hem de illit–adularya–kalsit stabilite alanlarını etkileyerek altının çökelmesini tetiklemektedir. Her iki sistemin karşılaştırılması, epitermal yatakların oluşumunda akışkan kaynakları, uçucu davranışı ve hidrotermal dengesizliklerin belirleyici rol oynadığını göstermektedir. Bu derleme, epitermal cevherleşmenin anlaşılmasında ve cevher arama modellerinin geliştirilmesinde kullanışlı kavramsal bir temel sunmaktadır.

Anahtar Kelimeler

• Epitermal Yataklar
• Düşük Sülfürlü
• Yüksek Sülfürlü
• Boşluklu silika

Kaynakça

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