Structural geology, age, and mechanisms of gold vein formation at the Kensington and Jualin deposits, Berners Bay District, Southeast Alaska
| Autor: | Lance J. Miller, Richard J. Goldfarb, Carol A. Gent, Lawrence W. Snee, Richard A. Kirkham |
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| Rok vydání: | 1995 |
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| Zdroj: | Economic Geology. 90:343-368 |
| ISSN: | 1554-0774 0361-0128 |
| Popis: | The Berners Bay district at the north end of the Juneau gold belt, southeast Alaska, contains a series of structurally controlled mesothermal gold-bearing quartz veins. The 106 Ma Jualin Diorite, which intrudes metabasalt of the Wrangellia terrane, hosts most of the > 2 Moz of gold resources. Wrangellia is one of a sequence of lithotectonic terranes that were accreted along the western margin of the Coast Mountains during Cretaceous time. Following a period of mid-Cretaceous deformation, igneous activity, and regional metamorphism, a belt of tonalite bodies 5 km east of the district were intruded at 71 to 61 Ma. Eocene granodioritic bodies of the Coast Mountains batholith were emplaced at shallow levels 10 km east of the district, coevally with gold vein emplacement. 40 Ar/ 39 Ar age spectra for hydrothermal sericite from variably oriented structures in the Berners Bay district indicate that hydrothermal activity occurred between 56.5 and 53.2 Ma. Gold occurs in quartz carbonate veins containing pyrite and tellurides and with distinctive ankeritic alteration zones. Gold-bearing veins were deposited at temperatures of about 200 degrees to 235 degrees C and a depth of 3 km. The ore fluids were composed of 93 to 97 mole percent H 2 O, 2 to 5 mole percent CO 2 , 1 to 2 mole percent NaCl |
| Databáze: | OpenAIRE |
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