Age constraints on Jerritt Canyon and other carlin-type gold deposits in the Western United States; relationship to mid-Tertiary extension and magmatism

Hofstra, Albert H.; Snee, Lawrence W.; Rye, Robert O.; Folger, Helen W.; Phinisey, Jeffrey D.; Loranger, R. J.; Dahl, A. R.; Naeser, Charles W.; Stein, Holly J.; Lewchuk, Michael T.

doi:10.2113/gsecongeo.94.6.769

Cited by 112 publications

(37 citation statements)

References 68 publications

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“…In the southern Tuscarora Mountains, more deeply formed plutonic rocks were exposed by 16.5 Ma and shed clasts into the western part of the Carlin basin. Supergene alunite dates from gold deposits along the Carlin and Getchell trends indicate that there was enough uplift and erosion to erode and weather the deposits between 30 and 18 Ma (Hofstra et al, 1999;Cline et al, 2005).…”

Section: Regional Geologic Settingmentioning

confidence: 99%

Late Cenozoic paleogeographic evolution of northeastern Nevada: Evidence from the sedimentary basins

2008

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Field and geochronologic studies of Neogene sedimentary basins in northeasternNevada document the paleogeographic and geologic evolution of this region and the effects on major mineral deposits. The broad area that includes the four middle Miocene basins studied-Chimney, Ivanhoe, Carlin, and Elko, from west to east-was an upland that underwent prolonged middle Tertiary exposure and moderate erosion. All four basins began to retain sediments at ca. 16 Ma. Eruption of volcanic fl ows in the Chimney and Ivanhoe basins produced short-lived (ca. 2 Ma), lacustrine-dominated basins before the dams failed and the streams drained to the southwest. In contrast, early, high-angle, normal faulting induced fl uvial to lacustrine sedimentation in the Carlin and Elko basins, and volcanic fl ows further blocked drainage in the Carlin basin until the basin drained at ca. 14.5 Ma. The Elko basin, with continued synsedimentary faulting, retained sediments until ca. 9.8 Ma and then drained west into the Carlin basin. Sediment buildup in all basins progressively buried existing highlands and created a subdued landscape.Relatively minor post-sedimentation extension produced early north-northwest-striking normal faults with variable amounts of offset, and later east-northeast-striking normal faults with up to several kilometers of vertical and left-lateral offset. The earlier faults are more pronounced east of the Tuscarora Mountains, possibly refl ecting a hanging-wall infl uence related to uplift of the Ruby Mountains-East Humboldt core complex on the east side of the Elko basin. The later faults are concentrated along the northnorthwest-trending northern Nevada rift west of the Tuscarora Mountains. The area west of the rift contains major tilted horsts and alluvium-fi lled grabens, and differential extension between this more highly extended region and the less extended area to the east produced the intervening east-northeaststriking faults.The Humboldt River drainage system formed as the four basins became integrated after ca. 9.8 Ma. Flow was into northwestern Nevada, the site of active normal faulting and graben formation. This faulting lowered the base level of the river and induced substantial erosion in upstream regions. Erosion preferentially removed the poorly consolidated Miocene sediments, progressively reexposed the pre-middle Miocene highlands, and transported the sediments to downstream basins. Thus, some ranges in the upstream region are exhumed older highlands rather than newly formed horsts. In addition, the drainage system evolution indicates that northern Nevada has become progressively lower than central Nevada since the middle Miocene.Mineral belts with large Eocene gold deposits are exposed in uplands and concealed beneath Neogene basin units in the study area. Also, numerous epithermal hot-spring deposits formed at and near the paleosurface in the Chimney, Ivanhoe, and Carlin basins as those basins were forming. The Neogene geologic and landscape evolution had variable effects on all of these deposits, includin...

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Section: Regional Geologic Settingmentioning

confidence: 99%

Late Cenozoic paleogeographic evolution of northeastern Nevada: Evidence from the sedimentary basins

2008

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“…Although still controversial, some geologists have concluded that Eocene stress relaxation and extension accompanied this southward sweep of arc magmatism across western North America (Gans et al, 1989;Feeley and Grunder, 1991;Seedorf, 1991;Hofstra et al, 1999). For example, Henry et al (2001), Haynes (2003), Satarugsa and Johnson (2000), Cline et al (2005), and Henrici and Haynes (2006) conclude that the Eocene-age Elko Formation accumulated in an extension-related basin (Fig.…”

Section: Geotectonic Settingmentioning

confidence: 99%

“…Small bodies of jasperoid have anomalous concentrations of Au, As, Hg, Sb, and Tl. The deposits are spatially associated with volcanism that is part of a south- S u lp h u r S p ri n g R a n g e Elko Carlin Study Are S u lp h u r S p ri n g R a n g e S u lp h u r S p ri n g R a n g e S u lp h u r S p ri n g R a n g e ward sweep of magmatism that passed through this area in the Eocene (Seedorf, 1991;Hofstra et al, 1999;Cline et al, 2005;Ressel and Henry, 2006). However, the exact nature of the relationship between Carlin-type deposits and Eocene magmatism is the subject of debate.…”

Section: Introductionmentioning

confidence: 99%

Age and petrogenesis of volcanic and intrusive rocks in the Sulphur Spring Range, central Nevada: Comparisons with ore-associated Eocene magma systems in the Great Basin

et al. 2008

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Widespread base-and precious-metal anomalies, oxidized sulfi de veins, silicifi ed calcareous shales and carbonates, and altered porphyry intrusions occur in the northeastern Sulphur Spring Range, Nevada, 80 km south of important gold deposits in the Carlin trend. The small historic mines and prospects in the area are spatially and perhaps genetically related to a suite of variably altered dikes, small lava fl ows, silicic domes, and related pyroclastic rocks. New major-and trace-element data and U-Pb zircon ages show that the East Sulphur Spring volcanic suite is Eo-Oligocene in age (36-31 Ma) and ranges in composition from high MgO-basaltic andesite to peraluminous rhyolite. The major-and trace-element compositions of the volcanic rocks are characteristic of continental margin subduction zone magmas and form a high-K, calc-alkaline suite with low Fe/Mg ratios. In addition, the rocks have negative Nb and Ti anomalies and elevated Ba, K, and Pb on normalized trace-element diagrams. Crustal melting is indicated by the eruption of a peraluminous garnet-bearing ignimbrite and as a component in hybridized andesite.The nature of this suite and its potential for mineralization is elucidated via comparisons to other Eocene age volcanic rocks associated with much larger gold and copper deposits in the Great Basin. The East Sulphur Spring suite is more similar to Eocene igneous rocks found along and near the Carlin trend than it is to those erupted while the Bingham porphyry copper deposit developed 300 km farther to the east. For example, the East Sulphur Spring suite and the Eocene magmatic rocks along the Carlin trend are less alkaline than the Bingham suite and lack its unusual enrichment of Cr, Ni, and Ba in intermediate composition rocks (58-68 wt% silica). Nonetheless, the Bingham and East Sulphur Spring volcanic suites both preserve evidence of mixing that created intermediate compositions. For example, an andesite has obvious mineral disequilibrium with plagioclase, biotite, clinopyroxene, orthopyroxene, olivine, and amphibole coexisting with extensively resorbed megacrysts of quartz, K-feldspar, and garnet-indicative of mixing basaltic andesite or andesite and largely crystallized garnet-bearing rhyolite. On the other hand, we found no evidence for mixing with a mafi c alkaline magma like that in the Bingham Canyon magma-ore system. We conclude that: (1) an unusual tectonic setting prevailed during the Eocene and Oligocene of the western United States that promoted the production of oxidized mafi c magma in an arclike setting, but far inland as a result of the rollback of the Farallon slab;(2) the mafi c magmas intruded or erupted separately, or mixed with more silicic magma generated by fractional crystallization and assimilation of crustal materials; and (3) these mafi c magmas may have delivered signifi cant amounts of sulfur and chalcophile metals to upper crustal magma chambers and eventually to Paleogene ore deposits in the eastern Great Basin.

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“…Many of the major mineral deposits in north-central Nevada (including the worldclass Carlin-type gold deposits) formed during the Eocene-early Oligocene (e.g., Hofstra et al, 1999;Ressel and Henry, 2006) and thus predate major extension in the northern Basin and Range, which took place primarily during the Miocene (e.g., Dickinson, 2006). Mineral deposits and potential mineralized host rocks have been variably disrupted by this faulting; therefore understanding Basin and Range deformation in this region is key for placing these deposits in their original structural context and for locating unexposed deposits beneath sedimentary or structural cover.…”

Section: Introductionmentioning

confidence: 99%

Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada

et al. 2008

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Because major mineral deposits in northcentral Nevada predate signifi cant Basin andRange extension, a detailed understanding of the timing and kinematics of extensional faulting is necessary to place these deposits in their original structural context. The complexity of pre-Cenozoic deformation in northern Nevada makes restoring Basin and Range faulting diffi cult without locating well-dated, regionally extensive Cenozoic units that can be used to restore slip along normal faults. The goal of this study is to reconstruct extensional faulting in the Shoshone and northern Toiyabe Ranges by using Cenozoic rocks in and around the Caetano caldera, which formed ca. 33.8 Ma during eruption of the Caetano Tuff. The caldera fi lled with more than 4 km of intracaldera tuff during initial caldera-forming eruptions, and additional sedimentary and volcanic rocks subsequently fi lled the topographic depression left by the caldera collapse. These rocks are conformable over the interval 34-25 Ma, consistent with little, if any, extension during that time. The 34-25 Ma rocks were later cut by a set of closely spaced (1-3 km) normal faults that accommodated signifi cant extension and footwall rotations of 40º-50º. Restored structural cross sections indicate that the present ~42 km (east-west) width of the Caetano caldera has been extended 110%, resulting in 22 ± 3 km westward translation of the Fish Creek Mountains relative to the southern Cortez Range. Major normal faults mapped within the caldera continue south and north along strike into the surrounding Paleozoic basement rocks; therefore it is likely that parts of surrounding areas are also signifi cantly extended. Miocene (16-12 Ma) sedimentary rocks in the hanging walls of major normal faults include both fl uvial/lacustrine facies and coarser alluvial fan deposits. Where exposed, the bases of the Miocene sedimentary sections are in angular conformity with underlying ~40°E tilted 34-25 Ma volcanic and sedimentary rocks. The distribution, composition, and geometry of these deposits are best explained by accumulation in a set of half-graben basins that formed in response to slip on basin-bounding faults. Extension thus appears to have taken place in the middle Miocene, beginning at or shortly after 16 Ma, and was mostly completed by 10-12 Ma. Fault blocks and basins formed during middle Miocene extension are cut by younger, more widely spaced, high-angle normal faults that began forming more recently than 10-12 Ma. These faults outline the modern basins and ranges in the study area and some have remained active into the Holocene.

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Age constraints on Jerritt Canyon and other carlin-type gold deposits in the Western United States; relationship to mid-Tertiary extension and magmatism

Cited by 112 publications

References 68 publications

Late Cenozoic paleogeographic evolution of northeastern Nevada: Evidence from the sedimentary basins

Late Cenozoic paleogeographic evolution of northeastern Nevada: Evidence from the sedimentary basins

Age and petrogenesis of volcanic and intrusive rocks in the Sulphur Spring Range, central Nevada: Comparisons with ore-associated Eocene magma systems in the Great Basin

Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada

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