Evidence for a modified placer origin for auriferous conglomerates, Canavieiras Mine, Jacobina, Brazil

Autor:	W. H. Gross
Rok vydání:	1968
Předmět:	Placer mining Dike geography geography.geographical_feature_category Geochemistry Mineralogy Metamorphism chemistry.chemical_element Geology engineering.material Uranium Conglomerate Intrusion Geophysics Uraninite chemistry Geochemistry and Petrology engineering Economic Geology Pyrite
Zdroj:	Economic Geology. 63:271-276
ISSN:	1554-0774 0361-0128
DOI:	10.2113/gsecongeo.63.3.271
Popis:	Gold is a trace constituent (average 0.015 ounces per ton) in the matrix of virtually all the 28 conglomerate beds exposed at the mine, and economic concentrations occur in 10 beds that are interpreted as giant foreset beds. The greatest concentrations occur close to the line where the foresets grade into topsets, supporting a placer origin for the gold. During subsequent folding, metamorphism, and intrusion, gold was redistributed to form concentrations at the top of the conglomerate beds and near dike contacts. Some gold is seen in fractures cutting conglomerate boulders. High-grade gold is associated with stringers of pitchblende. There is no evidence that gold is necessarily cogenetic with pyrite or uranium minerals.
Databáze:	OpenAIRE
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