This thesis focuses on fisheries managers’ efforts to restore native cutthroats to northern Nevada’s Pyramid Lake for recreation, and the Paiutes’ battle to preserve them as a means of livelihood. Their efforts to reconstruct the fishery revealed the implausibility of environmental restoration, but more importantly underlined the motivations necessary to attempt it. Chapter 2 describes how the Pyramid Lake Lahontan cutthroat— historically an important subsistence resource for Northern Paiutes— were initially exploited for profit in the late 1800s and early 1900s, and gradually destroyed as agricultural interests diverted the Truckee River’s water and industrial pollution contaminated the trout’s aquatic habitat. Fisheries managers in Nevada turned to artificial propagation to meet the demands of fishermen and replace the native fish industrialization destroyed. The Nevada Fish and Game Commission experimented with non-native introductions and like most of the West became proponents of rainbow trout and their recreational potential. Chapter 3 narrates a history of the Nevada Fish and Game Commission’s project to restore trout to Pyramid Lake in the 1950s and 1960s after its native cutthroat became extinct in the early 1940s. For the Commission, restoring Pyramid Lake meant establishing trout and salmon populations— native or not— to feed the growing outdoor tourism industry. While the Commission made plans to restore natural spawning runs, these were unsuccessful, and the Commission relied on stocking the lake to maintain the fishery. However, these experiments failed and eventually cutthroats from other lakes in Nevada proved better occupants of the lake. Chapter 4 describes the native cutthroat’s role in the water debate carried out in government agencies and in the courts in the 1970s and 1980s to decide whether or not water diverted from the Truckee for agriculture should be returned to the Paiutes to support their shrinking lake and dwindling fishery. Environmentalist groups like the Sierra Club joined the Paiutes in their effort to gain water that would allow for the native fishery’s restoration. Their vision clashed with that of agriculturists who feared losing water they depended on for their crops. However, after a lengthy struggle, the Paiutes won an important victory toward preserving their lake.

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. / Graduation date: 2013