Preface to SEG Compilation on Carlin-type Gold Deposits

John Muntean

Nevada Bureau of Mines and Geology

University of Nevada Reno

 

Since the discovery of the original Carlin gold deposit in 1961, approximately 200 million ounces of gold in Carlin-type deposits have been mined or identified in northern Nevada, making the United States one of the world’s largest gold producers for the past several decades. Despite their importance, Carlin-type deposits remain enigmatic.   Controversy over their origin mainly stems from the very fine grained character of the ore and gold. Carlin-type gold deposits are largely hydrothermal replacement bodies with visually subtle alteration dominated by decarbonatization and silicification of carbonate-bearing host rocks. Gold occurs in solid solution or as submicron particles in very fine grained disseminated arsenian pyrite or marcasite. To date, over 90% of the gold mined from what most geologists would call Carlin-type deposits has come from northern Nevada, and debate exists whether similar-looking deposits elsewhere share a comparable origin or whether the deposits in Nevada represent a unique occurrence.

Numerous papers on Carlin-type gold deposits have been published in Economic Geology and in various publications by the Society of Economic Geologists (SEG).   This SEG Compilation contains 157 papers that cover a range of topics.   The papers in this compilation are organized into ten categories:

1. Summary Papers
2. Deposit Description/Paragenesis/Origin; subcategory for Forum 2005

3. Age-Dating

4. Geochemistry/Alteration

5. Pyrite/Sulfides
6. Organic Matter
6. Structural Geology/Magmatism/Tectonic Setting/Geophysics
7. Carlin-like Deposits

9. Other Relative Papers
10. Papers in SEG Guidebooks

 

This huge collection of papers is summarized below in a chronological manner so one can better appreciate the evolution of thought regarding these controversial deposits.The Early Years (1921-1960)The first paper in Economic Geology on a Carlin-type deposit was Ferguson’s 1921 paper on the limestone ores of the Manhattan district in Nevada.   His description of the White Caps mine, which contained silver-poor gold ores associated with pyrite, arsenopyrite, orpiment, stibnite, and realgar, with no visible gold, is uncannily similar to the ores that were found near Carlin, Nevada, forty years later.   Even then, unanswered questions remained over the temporal relationship of the White Cap ores to adjacent ores at the Manhattan Consolidated mine, where much of the ore was of more typical epithermal character, occurred in fissures, had visible gold, and contained appreciable silver.   For the next description of a Carlin-type deposit, readers had to wait 30 years, until Joralemon’s 1951 paper on the Getchell gold deposit.   Joralemon recognized the importance of “invisible” gold at Getchell and other deposits in Nevada, and likened them to mercury deposits and active hot spring systems, an idea that remained popular for many decades, and that may still hold validity.

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Carlin-type gold deposits: a compliation

Владелец инбокса: kaptar.j

Preface to SEG Compilation on Carlin-type Gold Deposits

John Muntean

Nevada Bureau of Mines and Geology

University of Nevada Reno

 

Since the discovery of the original Carlin gold deposit in 1961, approximately 200 million ounces of gold in Carlin-type deposits have been mined or identified in northern Nevada, making the United States one of the world’s largest gold producers for the past several decades. Despite their importance, Carlin-type deposits remain enigmatic.   Controversy over their origin mainly stems from the very fine grained character of the ore and gold. Carlin-type gold deposits are largely hydrothermal replacement bodies with visually subtle alteration dominated by decarbonatization and silicification of carbonate-bearing host rocks. Gold occurs in solid solution or as submicron particles in very fine grained disseminated arsenian pyrite or marcasite. To date, over 90% of the gold mined from what most geologists would call Carlin-type deposits has come from northern Nevada, and debate exists whether similar-looking deposits elsewhere share a comparable origin or whether the deposits in Nevada represent a unique occurrence.

Numerous papers on Carlin-type gold deposits have been published in Economic Geology and in various publications by the Society of Economic Geologists (SEG).   This SEG Compilation contains 157 papers that cover a range of topics.   The papers in this compilation are organized into ten categories:

1. Summary Papers
2. Deposit Description/Paragenesis/Origin; subcategory for Forum 2005

3. Age-Dating

4. Geochemistry/Alteration

5. Pyrite/Sulfides
6. Organic Matter
6. Structural Geology/Magmatism/Tectonic Setting/Geophysics
7. Carlin-like Deposits

9. Other Relative Papers
10. Papers in SEG Guidebooks

 

This huge collection of papers is summarized below in a chronological manner so one can better appreciate the evolution of thought regarding these controversial deposits.The Early Years (1921-1960)The first paper in Economic Geology on a Carlin-type deposit was Ferguson’s 1921 paper on the limestone ores of the Manhattan district in Nevada.   His description of the White Caps mine, which contained silver-poor gold ores associated with pyrite, arsenopyrite, orpiment, stibnite, and realgar, with no visible gold, is uncannily similar to the ores that were found near Carlin, Nevada, forty years later.   Even then, unanswered questions remained over the temporal relationship of the White Cap ores to adjacent ores at the Manhattan Consolidated mine, where much of the ore was of more typical epithermal character, occurred in fissures, had visible gold, and contained appreciable silver.   For the next description of a Carlin-type deposit, readers had to wait 30 years, until Joralemon’s 1951 paper on the Getchell gold deposit.   Joralemon recognized the importance of “invisible” gold at Getchell and other deposits in Nevada, and likened them to mercury deposits and active hot spring systems, an idea that remained popular for many decades, and that may still hold validity.

Прикрепленные файлы
Категория: Полезные ископаемые Метки: Carlin type gold,Gold,Золото,Полезные ископаемые,
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