Controls on the distribution of molybdenum and other critical trace elements at the Bingham Canyon porphyry deposit, Utah

File Description SizeFormat 
Appendix A - Sample catalogue.pdfSample descriptions220.47 MBAdobe PDFView/Open
Appendix B - Whole Rock Geochemistry Data.xlsxAnalytical Data138.6 kBMicrosoft ExcelView/Open
Appendix C - Molybdenite LA-ICP-MS Data.xlsxAnalytical Data11.6 MBMicrosoft ExcelView/Open
Appendix D - XRD Results.pdfAnalytical Data1.97 MBAdobe PDFView/Open
Appendix E - Re-Os Data and Compiled Geochronology Data.xlsxAnalytical Data28.38 kBMicrosoft ExcelView/Open
Appendix F - Molybdenum Isotope Data.xlsxAnalytical Data70.95 kBMicrosoft ExcelView/Open
Appendix G - Fluid Inclusion Microthermometry Data.xlsxAnalytical Data369.05 kBMicrosoft ExcelView/Open
Appendix H - Fluid Inclusion Raman Data.xlsxAnalytical Data7.58 MBMicrosoft ExcelView/Open
Appendix I - Fluid Inlucison LA-ICP-MS Data.xlsxAnalytical Data7.06 MBMicrosoft ExcelView/Open
Appendix J - EPMA Data.xlsxAnalytical Data198.07 kBMicrosoft ExcelView/Open
Kocher-S-2017-PhD-Thesis.pdfThesis39.15 MBAdobe PDFView/Open
Title: Controls on the distribution of molybdenum and other critical trace elements at the Bingham Canyon porphyry deposit, Utah
Authors: Kocher, Simon
Item Type: Thesis or dissertation
Abstract: Molybdenite is a common mineral in porphyry deposits and is the only economic source for molybdenum metal. Approximately 99% of the global Mo production is obtained from porphyry-type deposits (e.g. Sillitoe, 2010), making it the metal with the single strongest affinity for a specific deposit type. The controls on the formation of Mo-rich porphyry deposits remain poorly constrained. By combining fieldwork, whole rock geochemistry, detailed analysis of molybdenite (i.e. trace element composition, Mo isotope composition and Re-Os dating) and a fluid inclusion study this project assesses the magmatic-hydrothermal evolution of Bingham Canyon to help constrain the processes controlling Mo mineralisation at one of the world's most prolific Cu-Au-Mo porphyry deposits. New high precision Re-Os molybdenite data suggest that molybdenum mineralisation formed between 37.62 and 38.22 Ma during a late hydrothermal event coinciding with the emplacement of the youngest porphyry phase. Petrographic and fluid inclusion and results indicate two episodes of mineralisation. Type 1 molybdenite formed at depth during the Cu-stage from single-phase, intermediate density parental fluids, prior to phase separation and main Cu deposition. Mo-rich Type 2 mineralisation formed at a later stage from high-salinity fluids and coexisting vapours that were exsolved directly from a fractionated magma source in response to mafic replenishment and T increase. The decoupled deposition of Mo and Cu at Bingham is attributed to the prior preferential extraction of Cu from the underlying, less evolved magma chamber during earlier mineralising events. Molybdenite precipitated in response to cooling and bulk reduction of the fluids. In accordance with data from other Mo-rich porphyry systems, results indicate that Mo-Cu decoupling is controlled by a combination of changes in source magma chemistry as well as by the evolving P-T-X properties of hydrothermal fluids. Molybdenite trace element compositions from Bingham and other localities are a function of their respective magmatic sources and are capable of recording hydrothermal overprints. Mineralogically complex Bi and As mineralisations formed during prograde skarn formation and in a high-sulphidation environment during the veining stages of the hydrothermal system.
Content Version: Open Access
Issue Date: May-2017
Date Awarded: Nov-2017
Supervisor: Wilkinson, Jamie J.
Sponsor/Funder: Rio Tinto (Group)
Imperial College London
Department: Earth Science & Engineering
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Earth Science and Engineering PhD theses

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