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A lithogeochemical study of hydrothermal alteration associated with Mafic Hosted and Besshi-type Massive Sulphide deposits Stoynov, Hristo Simeonov
Abstract
Pearce element ratio (PER) analysis was proposed in 1968 as a graphical method to be applied in petrology. Using major element chemical compositions of rocks, it allows for the determination of primary mineral parageneses. The application of the technique was later expanded to include studies of hydro thermal alteration associated with mineral deposits. This study tests the applicability of PER analysis and the related generalized element ratio (GER) analysis methods to the study of alteration associated with two classes of Volcanic-Hosted Massive Sulphide deposits. Presented are case studies of the Chu Chua and the Konuto Lake Mafic-Hosted Massive Sulphide deposits and the Goldstream Besshi-type deposit. Molar element ratio techniques (PER and GER) are used to identify altered samples and to differentiate between individual chemical alteration types. It is demonstrated that the technique is capable of identifying the exact alteration reaction for an individual sample or for a coherently altered group of samples. The format in which the chemical analytical data are presented allows for a convenient interpretation of the mineralogical effects of alteration. Thus, the validity of the conclusions based on major element lithogeochemistry can be independently verified by petrographic methods. The most typical chemical alteration types found in the three studied deposits are silica mobility (loss and addition), loss of Ca and Na and addition of Fe and Mg. Mineralogically, the alteration process involves the destruction of plagioclase and pyroxene, local deposition of quartz and deposition of iron sulphides. At Chu Chua, extreme Fe-Mg addition caused the characteristic talc-magnetite assemblage whereas at Goldstream Fe and Mg-rich clays were deposited in a seafloor hydrothermal vent setting. Mobilized Ca, Na and excess Si02 were exhaled on the seafloor, giving rise to exhalative chert deposits, carbonate and clay minerals. The tested technique allows the degree of alteration to be quantified in each individual sample. The geographic coordinates of altered samples are then plotted to reveal the spatial patterns of alteration. The outlined alteration anomalies coincide spatially with the known ore bodies and are significantly larger in overall dimensions. Thus, in an exploration context, they would represent intermediate targets. The study proposes exploration parameters, which can be used in similar geologic settings.
Item Metadata
Title |
A lithogeochemical study of hydrothermal alteration associated with Mafic Hosted and Besshi-type Massive Sulphide deposits
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2003
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Description |
Pearce element ratio (PER) analysis was proposed in 1968 as a graphical method to be applied
in petrology. Using major element chemical compositions of rocks, it allows for the
determination of primary mineral parageneses. The application of the technique was later
expanded to include studies of hydro thermal alteration associated with mineral deposits. This
study tests the applicability of PER analysis and the related generalized element ratio (GER)
analysis methods to the study of alteration associated with two classes of Volcanic-Hosted
Massive Sulphide deposits. Presented are case studies of the Chu Chua and the Konuto Lake
Mafic-Hosted Massive Sulphide deposits and the Goldstream Besshi-type deposit.
Molar element ratio techniques (PER and GER) are used to identify altered samples and to
differentiate between individual chemical alteration types. It is demonstrated that the
technique is capable of identifying the exact alteration reaction for an individual sample or for
a coherently altered group of samples. The format in which the chemical analytical data are
presented allows for a convenient interpretation of the mineralogical effects of alteration.
Thus, the validity of the conclusions based on major element lithogeochemistry can be
independently verified by petrographic methods.
The most typical chemical alteration types found in the three studied deposits are silica
mobility (loss and addition), loss of Ca and Na and addition of Fe and Mg. Mineralogically,
the alteration process involves the destruction of plagioclase and pyroxene, local deposition of
quartz and deposition of iron sulphides. At Chu Chua, extreme Fe-Mg addition caused the
characteristic talc-magnetite assemblage whereas at Goldstream Fe and Mg-rich clays were
deposited in a seafloor hydrothermal vent setting. Mobilized Ca, Na and excess Si02 were
exhaled on the seafloor, giving rise to exhalative chert deposits, carbonate and clay minerals.
The tested technique allows the degree of alteration to be quantified in each individual sample.
The geographic coordinates of altered samples are then plotted to reveal the spatial patterns of
alteration. The outlined alteration anomalies coincide spatially with the known ore bodies and
are significantly larger in overall dimensions. Thus, in an exploration context, they would
represent intermediate targets. The study proposes exploration parameters, which can be used
in similar geologic settings.
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Extent |
51585033 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-11-12
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0052684
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2003-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.