Graduate Thesis Or Dissertation

 

Trace element characteristics of zircon : a means of assessing mineralization potential of intrusions in northern Nevada Public Deposited

https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/6m311s69r

Descriptions

Attribute NameValues
Creator
Abstract
  • Oxidized hydrous intermediate composition magmas are responsible for porphyry copper (Cu ±Mo ±Au) deposits and epithermal Au ore deposits formed globally in the shallow crust (Sillitoe, 2010; Seedorff et al., 2005). Recently, zircon geochemistry has been used to characterize both productive and barren intrusions associated with porphyry Cu-Au ore deposits. Zircon composition differs slightly between the two intrusive groups, and researchers have proposed that zircon in productive intrusions has crystallized from a relatively more oxidized melt compared to barren intrusions (Ballard et al., 2002; Muñoz et al., 2012). Zircon rare earth elements record anomalies in Ce and Eu contents that allow estimation of the ratio of oxidized versus reduced species, i.e. Ce⁴⁺/Ce³⁺ (Ce[superscript IV]/Ce[superscript III]) and Eu³⁺/Eu²⁺ (Eu/Eu*)[subscript CN]. This study focuses on understanding the compositions of Eocene magmas associated with sediment hosted Carlin gold deposits and the gold-copper ores of the Battle Mountain porphyry Cu-Au-skarn district in northern Nevada. Zircon trace element composition was analyzed using LA-ICP-MS and SHRIMP-RG to determine differences between mineralizing and non-mineralizing intrusions in northern Nevada and to compare these compositions with known porphyry Cu-Au type magmas. These zircon and rock compositional data was then used to test the hypothesis of a magmatic origin of the Carlin type gold deposits (Muntean et al., 2011). Zircon U-Pb ages were calculated using multiple SHRIMP-RG spot analyses of each sample for two Carlin biotite porphyry dikes, two Battle Mountain porphyry dikes and the granodiorite of the Copper Canyon stock. The new U-Pb age dates for Carlin porphyry dikes are 38.7 ± 0.5 Ma and 38.8 ± 0.4 Ma. The age of the Copper Canyon stock is 38.0 ± 0.7 Ma, and the age of the Battle Mountain porphyry dikes are 40.2 ± 0.4 Ma and 41.3 ± 0.4 Ma. The Carlin dike ages are the same age, within uncertainty, with previous studies conducted (Mortensesn et al., 2000). The productive porphyry dikes from the Battle Mountain district have Ce(IV)/Ce(III) ratios of 500 to 10000 and a wide range of (Eu/Eu*)[subscript CN] values between 0.3 and 0.7 respectively. Carlin porphyry dikes have Ce(IV)/Ce(III) values between 100 and 1000, and a more limited (Eu/Eu*)[subscript CN] range of 0.5 to 0.7. Barren Eocene intrusions at Harrison Pass and Caetano have much lower Ce(IV)/Ce(III) ratios that range from 20 to 500, and have a very large span of (Eu/Eu*)[subscript CN] from 0.03 to 0.6. Calculated Ce(IV)/Ce(III) and (Eu/Eu*)[subscript CN] of zircon of this study illustrate a distinction between productive and barren intrusions in northern Nevada, and demonstrate a geochemical link between porphyry type magmas and dikes associated with Carlin type gold deposits. These ratios may provide a useful means of evaluating potentially economic geologic terranes and serving as a method to infer relative oxidation state of zircon bearing intrusive rocks.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Keyword
Subject
Rights Statement
Peer Reviewed
Language
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2013-01-22T19:23:50Z (GMT) No. of bitstreams: 1 FarmerLucianP2013.pdf: 9012175 bytes, checksum: 97f493f46832827ea867dc52b3c353f8 (MD5)
  • description.provenance : Made available in DSpace on 2013-01-23T18:09:13Z (GMT). No. of bitstreams: 1 FarmerLucianP2013.pdf: 9012175 bytes, checksum: 97f493f46832827ea867dc52b3c353f8 (MD5) Previous issue date: 2012-11-29
  • description.provenance : Submitted by Lucian Farmer (farmerlu@onid.orst.edu) on 2013-01-14T04:52:32Z No. of bitstreams: 1 FarmerLucianP2013.pdf: 9012175 bytes, checksum: 97f493f46832827ea867dc52b3c353f8 (MD5)
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2013-01-23T18:09:13Z (GMT) No. of bitstreams: 1 FarmerLucianP2013.pdf: 9012175 bytes, checksum: 97f493f46832827ea867dc52b3c353f8 (MD5)

Relationships

Parents:

This work has no parents.

In Collection:

Items